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Sample records for dispersed flow film

  1. A one-dimensional semi-empirical model considering transition boiling effect for dispersed flow film boiling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu-Jou [Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC (China); Pan, Chin, E-mail: cpan@ess.nthu.edu.tw [Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC (China); Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC (China); Low Carbon Energy Research Center, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC (China)

    2017-05-15

    Highlights: • Seven heat transfer mechanisms are studied numerically by the model. • A semi-empirical method is proposed to account for the transition boiling effect. • The parametric effects on the heat transfer mechanisms are investigated. • The thermal non-equilibrium phenomenon between vapor and droplets is investigated. - Abstract: The objective of this paper is to develop a one-dimensional semi-empirical model for the dispersed flow film boiling considering transition boiling effects. The proposed model consists of conservation equations, i.e., vapor mass, vapor energy, droplet mass and droplet momentum conservation, and a set of closure relations to address the interactions among wall, vapor and droplets. The results show that the transition boiling effect is of vital importance in the dispersed flow film boiling regime, since the flowing situation in the downstream would be influenced by the conditions in the upstream. In addition, the present paper, through evaluating the vapor temperature and the amount of heat transferred to droplets, investigates the thermal non-equilibrium phenomenon under different flowing conditions. Comparison of the wall temperature predictions with the 1394 experimental data in the literature, the present model ranging from system pressure of 30–140 bar, heat flux of 204–1837 kW/m{sup 2} and mass flux of 380–5180 kg/m{sup 2} s, shows very good agreement with RMS of 8.80% and standard deviation of 8.81%. Moreover, the model well depicts the thermal non-equilibrium phenomenon for the dispersed flow film boiling.

  2. Three-dimensional investigation of liquid film structure at the initial area of annular-dispersed flow

    Directory of Open Access Journals (Sweden)

    Alekseenko Sergey

    2016-01-01

    Full Text Available Initial stage of downward flow of gas-sheared liquid film in a vertical rectangular duct was studied using brightness-based laser-induced fluorescence technique. Measurements were resolved along both longitudinal and transverse coordinates and time. The initial high-frequency waves which are formed at the inlet were found to be two-dimensional. These waves are promptly broken into localised horseshoe-shaped waves which merge downstream to form large-scale quasi-2D disturbance waves. Peculiarities of three-dimensional evolution of waves of different types were studied in a wide range of flow parameters.

  3. Air Flow and Dispersion Section

    Energy Technology Data Exchange (ETDEWEB)

    Slinn, W. G.N.; Nicola, P. W.; Powell, D. C.; Davis, W. E.

    1976-03-01

    There are eight papers in this section. Some of the fundamentals of atmospheric dispersion of pollutants are examined with theoretical analyses as well as detailed experimental investigations. Emphasis has been placed on analyzing and summarizing previous experimental dispersion data with more realistic and fundamentally sound approaches to plume behavior. The goal is to finalize improved short-range dispersion models from existing data, removing inconsistencies and inadequacies in presently applied assessment models. Dispersion and transport efforts in the future should aim toward evaluating plume behavior on meso and regional scales. The complex features of flow and dispersion through storms, and in the vicinity of significant terrain characteristics influencing local to regional circulations must receive future emphasis. (auth)

  4. DISPERSION OF CYLINDRICAL PARTICLES IN TURBULENT FLOWS

    Institute of Scientific and Technical Information of China (English)

    GAO Zhen-yu; LIN Jian-zhong

    2004-01-01

    With consideration of the Stokes drag and virtual mass force, the equations for mean and fluctuating velocities in rotation and translation were given for rigid cylindrical particles moving in a turbulent flow. Then the rotational and translational dispersion coefficients of particle were derived. The relationships between the dispersion coefficients and flow length scale as well as particle characteristic parameters were analyzed. The resulting dispersion coefficients were proved to decrease as the particle length increases. The conclusions are helpful for the further research on the motion of cylindrical particles in turbulent flows.

  5. Flow properties of acetylated chickpea protein dispersions.

    Science.gov (United States)

    Liu, Li H; Hung, Tran V

    2010-06-01

    Chickpea protein concentrate was acetylated with acetic anhydride at 5 levels. Acetylated chickpea protein (ACP) dispersions at 3 levels (6%, 45%, and 49%) were chosen for this flow property study. Effects of protein concentration, temperature, concentrations of salt addition and particularly, degree of acetylation on these properties were examined. Compared with native chickpea proteins, the ACP dispersions exhibited a strong shear thinning behavior. Within measured temperature range (15 to 55 degrees C), the apparent viscosities of native chickpea protein dispersions were temperature independent; those of ACP dispersions were thermally affected. The flow index (n), consistency coefficient (m), apparent yield stress, and apparent viscosities of ACP dispersions increased progressively up to 45% acetylation but decreased at 49% acetylation level. Conformational studies by gel filtration suggested that chickpea proteins were associated or polymerized at up to 45% acetylation but the associated subunits gradually dissociated to smaller units at higher levels (49%) of acetylation.

  6. Frictionless dispersive hydrodynamics of Stokes flows

    CERN Document Server

    Maiden, Michelle D; Anderson, Dalton V; Schubert, Marika E; Hoefer, Mark A

    2016-01-01

    Effectively frictionless, dispersive flow characterizes superfluids, nonlinear optical diffraction, and geophysical fluid interfaces. Dispersive shock waves (DSWs) and solitons are fundamental nonlinear excitations in these media, but DSW studies to date have been severely constrained by a loss of coherence. Here we report on a novel dispersive hydrodynamics testbed: the effectively frictionless flow of interfacial waves between two high contrast, low Reynolds' number Stokes fluids. This system enables high fidelity observations of large amplitude DSWs, found to agree quantitatively with a nonlinear wave averaging theory. We then report on observations of highly coherent phenomena including DSW backflow, the refraction or absorption of solitons by DSWs, and multi-phase DSW-DSW merger. The complex, coherent, nonlinear mixing of DSWs and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.

  7. Shear Flow Dispersion Under Wave and Current

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The longitudinal dispersion of solute in open channel flow with short period progressive waves is investigated. The waves induce second order drift velocity in the direction of propagation and enhance the mixing process in concurrent direction. The 1-D wave-period-averaged dispersion equation is derived and an expression for the wave-current induced longitudinal dispersion coefficient (WCLDC) is proposed based on Fischer's expression (1979) for dispersion in unidirectional flow. The result shows that the effect of waves on dispersion is mainly due to the cross-sectional variation of the drift velocity. Furthermore, to obtain a more practical expression of the WCLDC, the longitudinal dispersion coefficient due to Seo and Cheong (1998) is modified to incluee the effect of drift velocity. Laboratory experiments have been conducted to verify the proposed expression. The experimental results, together with dimensional analysis, show that the wave effect can be reflected by the ratio between the wave amplitude and wave period. A comparative study between the cases with and without waves demonstrates that the magnitude of the longitudinal dispersion coefficient is increased under the presence of waves.

  8. Dispersion of Suspensions in Unsteady Microchannel Flows

    Science.gov (United States)

    Maxey, Martin; Howard, Amanda; Winklerprins, Lukas; Tripathi, Anubhuv; Yeo, Kyongmin

    2013-11-01

    We explore the dispersion of non-Brownian (Pe >> 1) suspensions in unsteady, low Reynolds number shear flows in a microchannel. Prior experimental work on oscillating Couette flows and Poiseuille flows has shown the importance of strain amplitude in determining the long term distribution of particles across the channel. We will present results from numerical simulations for the early development of these flows and the motion of finite length suspension plugs. The distortion of a plug by the shear flow results in inhomogeneous particle fluxes across the channel. This is largely reversible over the course of a full cycle, giving reversibility in the bulk. Self-diffusion gives irreversibility though at the microscale. As the strain amplitude increases or the initial volume fraction increases irreversibility in the bulk is seen. The dynamics behind these processes and the role of particle pressure will be noted, together with related experimental observations.

  9. Flow separation characteristics of unstable dispersions

    Science.gov (United States)

    Voulgaropoulos, Victor; Zhai, Lusheng; Angeli, Panagiota

    2016-11-01

    Drops of a low viscosity oil are introduced through a multi-capillary inlet during the flow of water in a horizontal pipe. The flow rates of the continuous water phase are kept in the turbulent region while the droplets are injected at similar flow rates (with oil fractions ranging from 0.15 to 0.60). The acrylic pipe (ID of 37mm) is approximately 7m long. Measurements are conducted at three different axial locations to illustrate how the flow structures are formed and develop along the pipe. Initial observations are made on the flow patterns through high-speed imaging. Stratification is observed for the flow rates studied, indicating that the turbulent dispersive forces are lower than the gravity ones. These results are complemented with a tomography system acquiring measurements at the same locations and giving the cross-sectional hold-up. The coalescence dynamics are strong in the dense-packed drop layer and thus measurements with a dual-conductance probe are conducted to capture any drop size changes. It is found that the drop size variations depend on the spatial configuration of the drops, the initial drop size along with the continuous and dispersed phase velocities. Project funded under Chevron Energy Technology.

  10. Characterization of thin films using generalized lamb wave dispersion relations

    OpenAIRE

    Richard, P; Behrend, O.; Gremaud, G.; Kulik, A.

    1993-01-01

    We used the Continuous Wave Scanning Acoustic Microscope to characterize thin film materials. The measurement of the dispersion curve of surface waves and the inversion of this dispersion equation relation, allow to determine the elastic constants, the density or the thickness of a thin layer on a substrate. Besides, it is possible to have qualitative information on the adhesion properties of the layer.

  11. Marangoni elasticity of flowing soap films

    CERN Document Server

    Kim, Ildoo

    2016-01-01

    We measure the Marangoni elasticity of a flowing soap film to be 22 dyne/cm irrespective of its width, thickness, flow speed, or the bulk soap concentration. We perform this measurement by generating an oblique shock in the soap film and measuring the shock angle, flow speed and thickness. We postulate that the elasticity is constant because the film surface is crowded with soap molecules. Our method allows non-destructive measurement of flowing soap film elasticity, and the value 22 dyne/cm is likely applicable to other similarly constructed flowing soap films.

  12. Effect of Solvation Film on the Viscosity of Colloidal Dispersions

    Institute of Scientific and Technical Information of China (English)

    PENG Chang-Sheng; GU Qing-Bao; SONG Shao-Xian

    2005-01-01

    Viscosity is one of the most important properties of colloids in mixing, transportation, stabilization, energy consumption, and so on. According to Einstein's viscosity equation, the viscosity of a colloidal dispersion increases with the increase of particle concentration. And the equation can be applicable to all micro-particle dispersions, because the effect of solvation films coated on particles can be neglectable in that case. But with the decrease of particle size to nano-scale, the formation of solvation films on nano-particles can greatly affect the viscosity of a dispersion, and Einstein's equation may not be applicable to this case. In this work, one kind of micro-size silica particle and two kinds of nano-size silica particles were used to investigate the effect of solvation films on dispersion viscosity, dispersed in water and ethyl alcohol solvents, respectively. The results of theoretical calculation and experimental investigation show that the increase of viscosity is contributed from solvation films by more than 95 percent for nano-particle dispersions, while less than 10 percent for micro-particle dispersions.

  13. Dan Joseph's contributions to disperse multiphase flow

    Science.gov (United States)

    Prosperetti, Andrea

    2012-11-01

    During his distinguished career, Dan Joseph worked on a vast array of problems. One of these, which occupied him off and on over the last two decades of his life, was that of flows with suspended finite-size particles at finite Reynolds numbers. He realized early on that progress in this field had to rely on the insight gained from numerical simulation, an area in which he was a pioneer. On the basis of the early numerical results he recognized the now famous ``drafting, kissing and tumbling'' mechanism of particle-particle interaction, the possibility of fluidization by lift and many others. With a number of colleagues and a series of gifted students he produced a significant body of work summarized in his on-line book Interrogations of Direct Numerical Simulation of Solid-Liquid Flows available from http://www.efluids.com/efluids/books/joseph.htm. This presentation will describe Joseph's contribution to the understanding of disperse multiphase flow and conclude with some examples from the author's recent work in this area. Supported by NSF.

  14. Vertical dispersion in vegetated shear flows

    Science.gov (United States)

    Rubol, Simonetta; Battiato, Ilenia; de Barros, Felipe P. J.

    2016-10-01

    Canopy layers control momentum and solute transport to and from the overlying water surface layer. These transfer mechanisms strongly dependent on canopy geometry, affect the amount of solute in the river, the hydrological retention and availability of dissolved solutes to organisms located in the vegetated layers, and are critical to improve water quality. In this work, we consider steady state transport in a vegetated channel under fully developed flow conditions. Under the hypothesis that the canopy layer can be described as an effective porous medium with prescribed properties, i.e., porosity and permeability, we model solute transport above and within the vegetated layer with an advection-dispersion equation with a spatially variable dispersion coefficient (diffusivity). By means of the Generalized Integral Transform Technique, we derive a semianalytical solution for the concentration field in submerged vegetated aquatic systems. We show that canopy layer's permeability affects the asymmetry of the concentration profile, the effective vertical spreading behavior, and the magnitude of the peak concentration. Due to its analytical features, the model has a low computational cost. The proposed solution successfully reproduces previously published experimental data.

  15. LONGITUDINAL DISPERSION IN SEDIMENT-LADEN OPEN CHANNEL FLOWS

    Institute of Scientific and Technical Information of China (English)

    Z.AHMAD; U.C.KOTHYARI; K.G.RANGA RAJU

    2004-01-01

    Laboratory experiments on longitudinal dispersion in clear-water and sediment-laden open channel flows are reported. Data from these experiments and those available from previous studies indicate that the suspended sediment present in the flow affects the longitudinal dispersion process. The observed velocity distributions over the depth of sediment-laden flows indicate that the velocity deviates from the mean velocity more in sediment-laden flows than in clear-water flows. The velocity distributions over the cross section and secondary flow in the channel are also expected to be altered due to the presence of suspended sediments in the flow. For these reasons, more dispersion is found in sediment-laden flows than in corresponding clear-water flows. A predictor for the dispersion coefficient in sediment-laden flows is proposed.

  16. Dispersion phenomena in helical flow in a concentric annulus.

    Science.gov (United States)

    Song, Young Seok; Brenner, Howard

    2009-12-14

    We examined dispersion phenomena of solutes in helical flow in a concentric annulus through a multiscale approach. The helical flow was developed by the combination of the Poiseuille flow and Couette flow. Here, we present an analytic model that can address the multidimensional Taylor dispersion in the helical flow under a lateral field of thermophoresis (or thermal diffusion) in the gapwise direction. Macroscopic parameters including the average solute velocity and dispersivity were analyzed using relevant microscopic physicochemical properties. The mathematically obtained results were validated by the numerical simulation carried out in this study. The findings show that macrotransport processes are robust and straightforward to handle multidimensional dispersion phenomena of solutes in helical flow. This study is expected to provide a theoretical platform for applications of helical flow such as tube exchangers, oil drilling, and multidimensional field flow fractionations (e.g., helical flow field flow fractionation).

  17. Marangoni elasticity of flowing soap films

    OpenAIRE

    Kim, Ildoo; Mandre, Shreyas

    2016-01-01

    We measure the Marangoni elasticity of a flowing soap film to be 22 dyne/cm irrespective of its width, thickness, flow speed, or the bulk soap concentration. We perform this measurement by generating an oblique shock in the soap film and measuring the shock angle, flow speed and thickness. We postulate that the elasticity is constant because the film surface is crowded with soap molecules. Our method allows non-destructive measurement of flowing soap film elasticity, and the value 22 dyne/cm ...

  18. Effects of dispersion forces in the instability of polymer films

    Institute of Scientific and Technical Information of China (English)

    Zhao He-Ping; Ophelia K.C.Tsui; Liu Zheng-You

    2006-01-01

    Spontaneous rupture of some polymer films upon heating is commonplace. The very criterion for this instability is the system free energy possessing a negative curvature. Within the framework of full frequency-dependent theory of dispersion forces, we have derived the excess free energy of a typical system-polystyrene film deposited on the silicon substrate. The excess free energy, wavelengths and growth rates are calculate and a comparison is made between the accurate results and the approximate results. It is found that the stability of the film can be tuned by the variation of the thickness of the coating and the retardation effects can be significant sometimes.

  19. Polyurethane Dispersions with Peptide Corona: Facile Synthesis of Stimuli-Responsive Dispersions and Films.

    Science.gov (United States)

    Breucker, Laura; Schöttler, Susanne; Landfester, Katharina; Taden, Andreas

    2015-08-10

    Peptide-polymer hybrid particles of submicron size yielding stimuli-responsive macroscopic films are presented. A thermoplastic polyurethane (PU) carrying polysiloxane and polyester soft segments serves as core material to obtain flexible, yet semicrystalline films with temperature-sensitivity. The synthesis is based on the high-sheer emulsification of isocyanate-terminated PU prepolymers, which in our model system purposefully lack any ability of colloidal self-stabilization. While emulsification in water leads to immediate coagulation, stable dispersions of polyurethane nanoparticles were formed in aqueous solutions of a hydrolyzed protein from wool. A comparison of dispersion and film properties to nonreactive, otherwise identical dispersions suggests covalent attachment of the peptide to the PU backbone. We show that the colloidal stability of the hybrid particles is completely governed by the peptide corona, and hence pH-triggered coagulation can be employed to induce particle deposition and film formation. Differential scanning calorimetry confirms partial crystallinity in the film and reveals strongly modified crystallization behavior due to the peptide.

  20. Large Eddy Simulation for Dispersed Bubbly Flows: A Review

    Directory of Open Access Journals (Sweden)

    M. T. Dhotre

    2013-01-01

    Full Text Available Large eddy simulations (LES of dispersed gas-liquid flows for the prediction of flow patterns and its applications have been reviewed. The published literature in the last ten years has been analysed on a coherent basis, and the present status has been brought out for the LES Euler-Euler and Euler-Lagrange approaches. Finally, recommendations for the use of LES in dispersed gas liquid flows have been made.

  1. Investigation on CuO Dispersed PVA Polymer Films

    Directory of Open Access Journals (Sweden)

    R. Divya

    2015-05-01

    Full Text Available Addition of inorganic nanoparticles to polymers allows the modification of physical properties of polymers as well as the implementation of new features in polymer matrix. In the present work, we have made an attempt to disperse CuO nanoparticles in the polyvinyl alcohol (PVA and to understand the change in structural, optical and electrical properties of the polymer film. CuO nanoparticles were added in four different concentrations, viz. 2.5, 5.0, 7.5 and 10 wt%. A total of 5 films were prepared (including the pure PVA film, for comparison.The prepared films were subjected to XRD, FESEM, UV-Vis spectral, PL spectral and electrical analyses. The results obtained are reported.

  2. Direct Measurements of Critical Stresses and Cracking in Thin Films of Colloid Dispersions

    Science.gov (United States)

    Man, Weining; Russel, William B.

    2008-05-01

    Useful films can be formed by drying colloidal dispersions, but the negative capillary pressure generated often promotes cracks. Complex lateral flows during drying compromised previous measurements of the pressure required for cracking. Here we report data for the onset of cracking, and the additional cracks that appear at higher pressures, from high-pressure ultrafiltration experiments on homogeneously compressed films. A comparison of the data with expectations from theory confirms that cracking is controlled by elastic recovery, though an energy criterion only provides a lower bound. Our experiments also identify the role of flaws as nucleation sites that initiate cracks.

  3. Porous squeeze-film flow

    KAUST Repository

    Knox, D. J.

    2013-11-14

    © 2013 © The authors 2013. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved. The squeeze-film flow of a thin layer of Newtonian fluid filling the gap between a flat impermeable surface moving under a prescribed constant load and a flat thin porous bed coating a stationary flat impermeable surface is considered. Unlike in the classical case of an impermeable bed, in which an infinite time is required for the two surfaces to touch, for a porous bed contact occurs in a finite contact time. Using a lubrication approximation, an implicit expression for the fluid layer thickness and an explicit expression for the contact time are obtained and analysed. In addition, the fluid particle paths are calculated, and the penetration depths of fluid particles into the porous bed are determined. In particular, the behaviour in the asymptotic limit of small permeability, in which the contact time is large but finite, is investigated. Finally, the results are interpreted in the context of lubrication in the human knee joint, and some conclusions are drawn about the contact time of the cartilage-coated femoral condyles and tibial plateau and the penetration of nutrients into the cartilage.

  4. Free convection film flows and heat transfer

    CERN Document Server

    Shang, Deyi

    2010-01-01

    Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.

  5. Flow fields in soap films: Relating viscosity and film thickness

    Science.gov (United States)

    Prasad, V.; Weeks, Eric R.

    2009-08-01

    We follow the diffusive motion of colloidal particles in soap films with varying h/d , where h is the thickness of the film and d is the diameter of the particles. The hydrodynamics of these films are determined by looking at the correlated motion of pairs of particles as a function of separation R . The Trapeznikov approximation [A. A. Trapeznikov, Proceedings of the 2nd International Congress on Surface Activity (Butterworths, London, 1957), p. 242] is used to model soap films as an effective two-dimensional (2D) fluid in contact with bulk air phases. The flow fields determined from correlated particle motions show excellent agreement with what is expected for the theory of 2D fluids for all our films where 0.6≤h/d≤14.3 , with the 2D shear viscosity matching that predicted by Trapeznikov. However, the parameters of these flow fields change markedly for thick films (h/d>7±3) . Our results indicate that three-dimensional effects become important for these thicker films, despite the flow fields still having a 2D character.

  6. Axial dispersion in flowing red blood cell suspensions

    Science.gov (United States)

    Podgorski, Thomas; Losserand, Sylvain; Coupier, Gwennou

    2016-11-01

    A key parameter in blood microcirculation is the transit time of red blood cells (RBCs) through an organ, which can influence the efficiency of gas exchange and oxygen availability. A large dispersion of this transit time is observed in vivo and is partly due to the axial dispersion in the flowing suspension. In the classic Taylor-Aris example of a solute flowing in a tube, the combination of molecular diffusion and parabolic velocity profile leads to enhanced axial dispersion. In suspensions of non-Brownian deformable bodies such as RBCs, axial dispersion is governed by a combination of shear induced migration and shear-induced diffusion arising from hydrodynamic interactions. We revisit this problem in the case of RBC pulses flowing in a microchannel and show that the axial dispersion of the pulse eventually saturates with a final extension that depends directly on RBC mechanical properties. The result is especially interesting in the dilute limit since the final pulse length depends only on the channel width, exponent of the migration law and dimensionless migration velocity. In continuous flow, the dispersion of transit times is the result of complex cell-cell and cell-wall interactions and is strongy influenced by the polydispersity of the blood sample. The authors acknowledge support from LabEx TEC21 and CNES.

  7. Particle cage dynamics in flowing colloidal dispersions

    Science.gov (United States)

    Marenne, Stephanie; Morris, Jeffrey F.

    2016-11-01

    The idea of the particle in a suspension at rest being trapped in a cage formed by its neighbors, widely used to understand glassy suspensions, has been applied to freely flowing suspensions. Stokesian Dynamics, a discrete particle simulation, is used to simulate the flow of monodisperse colloidal hard sphere suspensions. The cage analogy is useful to study the nonlinear stress in the material during start-up of shear flow, where the neighbor cage deforms and breaks, and during oscillatory shear flow where, depending on the amplitude of oscillation, the particle is trapped inside the cage or escapes during the oscillation cycle. A precise statistical definition of the cage in terms of the nearest neighbor ring in the pair distribution function is developed. We examine the dependence of the cage dynamics on the volume fraction of particles and the Peclet number Pe , the ratio between shear and Brownian forces. Under flow, the cage is found to break at quite definite positions, and the structural distortion is found to be clearly related to the shear and normal stress response. The shear strain needed to break the neighbor cage depends on Pe as Brownian motion enhances the total deformation. A simple model captures the strain at the stress overshoot for start-up of steady shear.

  8. Strongly coupled dispersed two-phase flows; Ecoulements diphasiques disperses fortement couples

    Energy Technology Data Exchange (ETDEWEB)

    Zun, I.; Lance, M.; Ekiel-Jezewska, M.L.; Petrosyan, A.; Lecoq, N.; Anthore, R.; Bostel, F.; Feuillebois, F.; Nott, P.; Zenit, R.; Hunt, M.L.; Brennen, C.E.; Campbell, C.S.; Tong, P.; Lei, X.; Ackerson, B.J.; Asmolov, E.S.; Abade, G.; da Cunha, F.R.; Lhuillier, D.; Cartellier, A.; Ruzicka, M.C.; Drahos, J.; Thomas, N.H.; Talini, L.; Leblond, J.; Leshansky, A.M.; Lavrenteva, O.M.; Nir, A.; Teshukov, V.; Risso, F.; Ellinsen, K.; Crispel, S.; Dahlkild, A.; Vynnycky, M.; Davila, J.; Matas, J.P.; Guazelli, L.; Morris, J.; Ooms, G.; Poelma, C.; van Wijngaarden, L.; de Vries, A.; Elghobashi, S.; Huilier, D.; Peirano, E.; Minier, J.P.; Gavrilyuk, S.; Saurel, R.; Kashinsky, O.; Randin, V.; Colin, C.; Larue de Tournemine, A.; Roig, V.; Suzanne, C.; Bounhoure, C.; Brunet, Y.; Tanaka, A.T.; Noma, K.; Tsuji, Y.; Pascal-Ribot, S.; Le Gall, F.; Aliseda, A.; Hainaux, F.; Lasheras, J.; Didwania, A.; Costa, A.; Vallerin, W.; Mudde, R.F.; Van Den Akker, H.E.A.; Jaumouillie, P.; Larrarte, F.; Burgisser, A.; Bergantz, G.; Necker, F.; Hartel, C.; Kleiser, L.; Meiburg, E.; Michallet, H.; Mory, M.; Hutter, M.; Markov, A.A.; Dumoulin, F.X.; Suard, S.; Borghi, R.; Hong, M.; Hopfinger, E.; Laforgia, A.; Lawrence, C.J.; Hewitt, G.F.; Osiptsov, A.N.; Tsirkunov, Yu. M.; Volkov, A.N.

    2003-07-01

    This document gathers the abstracts of the Euromech 421 colloquium about strongly coupled dispersed two-phase flows. Behaviors specifically due to the two-phase character of the flow have been categorized as: suspensions, particle-induced agitation, microstructure and screening mechanisms; hydrodynamic interactions, dispersion and phase distribution; turbulence modulation by particles, droplets or bubbles in dense systems; collective effects in dispersed two-phase flows, clustering and phase distribution; large-scale instabilities and gravity driven dispersed flows; strongly coupled two-phase flows involving reacting flows or phase change. Topic l: suspensions particle-induced agitation microstructure and screening mechanisms hydrodynamic interactions between two very close spheres; normal stresses in sheared suspensions; a critical look at the rheological experiments of R.A. Bagnold; non-equilibrium particle configuration in sedimentation; unsteady screening of the long-range hydrodynamic interactions of settling particles; computer simulations of hydrodynamic interactions among a large collection of sedimenting poly-disperse particles; velocity fluctuations in a dilute suspension of rigid spheres sedimenting between vertical plates: the role of boundaries; screening and induced-agitation in dilute uniform bubbly flows at small and moderate particle Reynolds numbers: some experimental results. Topic 2: hydrodynamic interactions, dispersion and phase distribution: hydrodynamic interactions in a bubble array; A 'NMR scattering technique' for the determination of the structure in a dispersion of non-brownian settling particles; segregation and clustering during thermo-capillary migration of bubbles; kinetic modelling of bubbly flows; velocity fluctuations in a homogeneous dilute dispersion of high-Reynolds-number rising bubbles; an attempt to simulate screening effects at moderate particle Reynolds numbers using an hybrid formulation; modelling the two

  9. Studies on dispersive stabilization of porous media flows

    Energy Technology Data Exchange (ETDEWEB)

    Daripa, Prabir, E-mail: prabir.daripa@math.tamu.edu; Gin, Craig [Department of Mathematics, Texas A& M University, College Station, Texas 77843 (United States)

    2016-08-15

    Motivated by a need to improve the performance of chemical enhanced oil recovery (EOR) processes, we investigate dispersive effects on the linear stability of three-layer porous media flow models of EOR for two different types of interfaces: permeable and impermeable interfaces. Results presented are relevant for the design of smarter interfaces in the available parameter space of capillary number, Peclet number, longitudinal and transverse dispersion, and the viscous profile of the middle layer. The stabilization capacity of each of these two interfaces is explored numerically and conditions for complete dispersive stabilization are identified for each of these two types of interfaces. Key results obtained are (i) three-layer porous media flows with permeable interfaces can be almost completely stabilized by diffusion if the optimal viscous profile is chosen, (ii) flows with impermeable interfaces can also be almost completely stabilized for short time, but become more unstable at later times because diffusion flattens out the basic viscous profile, (iii) diffusion stabilizes short waves more than long waves which leads to a “turning point” Peclet number at which short and long waves have the same growth rate, and (iv) mechanical dispersion further stabilizes flows with permeable interfaces but in some cases has a destabilizing effect for flows with impermeable interfaces, which is a surprising result. These results are then used to give a comparison of the two types of interfaces. It is found that for most values of the flow parameters, permeable interfaces suppress flow instability more than impermeable interfaces.

  10. Stability of algebraically unstable dispersive flows

    Science.gov (United States)

    King, Kristina R.; Weinstein, Steven J.; Zaretzky, Paula M.; Cromer, Michael; Barlow, Nathaniel S.

    2016-11-01

    A largely unexplored type of hydrodynamic instability is examined: long-time algebraic growth. Such growth is possible when the dispersion relation extracted from classical stability analysis indicates neutral stability. A physically motivated class of partial differential equations that describes the response of a system to disturbances is examined. Specifically, the propagation characteristics of the response are examined in the context of spatiotemporal stability theory. Morphological differences are identified between system responses that exhibit algebraic growth and the more typical case of exponential growth. One key attribute of predicted algebraically growing solutions is the prevalence of transient growth in almost all of the response, with the long-time growth occurring asymptotically at precisely one wave speed.

  11. Contaminant dispersal in bounded turbulent shear flow

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, J.M.; Bernard, P.S.; Chiang, K.F.; Ong, L. [Univ. of Maryland, College Park, MD (United States)

    1995-12-31

    The dispersion of smoke downstream of a line source at the wall and at y{sup +} = 30 in a turbulent boundary layer has been predicted with a non-local model of the scalar fluxes {bar u}c and {bar v}c. The predicted plume from the wall source has been compared to high Schmidt number experimental measurements using a combination of hot-wire anemometry to obtain velocity component data synchronously with concentration data obtained optically. The predicted plumes from the source at y{sup +} = 30 and at the wall also have been compared to a low Schmidt number direct numerical simulation. Near the source, the non-local flux models give considerably better predictions than models which account solely for mean gradient transport. At a sufficient distance downstream the gradient models gives reasonably good predictions.

  12. Mathematical modeling of disperse two-phase flows

    CERN Document Server

    Morel, Christophe

    2015-01-01

    This book develops the theoretical foundations of disperse two-phase flows, which are characterized by the existence of bubbles, droplets or solid particles finely dispersed in a carrier fluid, which can be a liquid or a gas. Chapters clarify many difficult subjects, including modeling of the interfacial area concentration. Basic knowledge of the subjects treated in this book is essential to practitioners of Computational Fluid Dynamics for two-phase flows in a variety of industrial and environmental settings. The author provides a complete derivation of the basic equations, followed by more advanced subjects like turbulence equations for the two phases (continuous and disperse) and multi-size particulate flow modeling. As well as theoretical material, readers will discover chapters concerned with closure relations and numerical issues. Many physical models are presented, covering key subjects including heat and mass transfers between phases, interfacial forces and fluid particles coalescence and breakup, a...

  13. Ways of intensifying liquid dispersion in gas flow

    Science.gov (United States)

    Bazarov, V. G.

    Ways of intensifying liquid dispersion in gas flow are examined with a view to increasing the efficiency of the existing atomizing nozzles. It is noted that the most economical method of dispersion intensification, without using any additional power, is the excitation of auto-oscillations in liquid and gas flows. Several methods of generating auto-oscillations in commonly used centrifugal nozzles are discussed. Other developments include the spraying of viscous and contaminated fluids in a field of forced pressure, velocity, and vorticity fluctuations, and also gas saturation of liquids prior to spraying in nozzles with porous elements.

  14. Axial Dispersion in Segmented Gas-Liquid Flow: Effects of the Channel Curvature

    Science.gov (United States)

    Muradoglu, Metin

    2009-11-01

    The effects of channel curvature on the axial dispersion in segmented gas-liquid flows have been studied computationally in a two-dimensional setting using a front-tracking/finite-volume method. Passive tracer particles are used to visualize and quantify the axial dispersion. The molecular diffusion is modeled by random walk of tracer particles. It is found that there is significant axial dispersion in serpentine channels even in the absence of molecular diffusion and dispersion increases with channel curvature. It is known that there is no dispersion in straight channels since a lubricating thin liquid layer persists on the wall. However this lubricating liquid layer is periodically broken in the curved channel case leading to enhanced axial dispersion. It is found that the dispersion increases as the Peclet number (Pe) decreases both in straight and curved channels. Difference between the straight and curved channel decreases continuously as the Peclet number decreases and virtually disappears at low Peclet numbers, i.e., Pestudy. A model is proposed based on the difference between the liquid film thicknesses on the inner and outer side of the bend in the limit as Pe->∞. Good agreement is found between the computational results and the model when the liquid slug is well mixed by the chaotic advection.

  15. Newly designed multilayer thin film mirror for dispersion compensation in Ti: sapphire femtosecond lasers

    Institute of Scientific and Technical Information of China (English)

    Chunyan Liao; Jianda Shao; Jianbing Huang; Zhengxiu Fan; Hongbo He

    2005-01-01

    @@ There are two different effects to generate group delay dispersion by multilayer thin film mirrors: chirper effect and Gires-Tournois effect. Both effects are employed to introduce desired dispersion in the designed mirror. Thus the designed mirror provides large dispersion throughout broad waveband. Such mirror can be used for dispersion compensation in Ti:sapphire femtosecond lasers. Most group delay dispersion of a 5-mm Ti:sapphire crystal can be compensated perfectly with only four bounces of the designed mirror.

  16. Studies in thin film flows

    CERN Document Server

    McKinley, I S

    2000-01-01

    the general case of non-zero capillary number numerically. Using the lubrication approximation to the Navier-Stokes equations we investigate the evolution and stability of a thin film of incompressible Newtonian fluid on a planar substrate subjected to a jet of air blowing normally to the substrate. For the simple model of the air jet we adopt, the initially axisymmetric problems we study are identical to those of a drop spreading on a turntable rotating at constant angular velocity (the simplest model for spin coating). We consider both drops without a dry patch (referred to as 'non-annular') and drops with a dry patch at their centre (referred to as 'annular'). First, both symmetric two-dimensional and axisymmetric three-dimensional drops are considered in the quasi-static limit of small capillary number. The evolution of both non-annular and annular drops and the stability of equilibrium solutions to small perturbations with zero wavenumber are determined. Using a specially developed finite-difference code...

  17. Film flows and self-organized patterns of 2D-localized structures

    Energy Technology Data Exchange (ETDEWEB)

    Frenkel, A.L. [Univ. of Alabama, Tuscaloosa, AL (United States)

    1996-12-31

    Films flowing down an inclined plane are considered. An unconventional perturbation approach is discussed. It yields the most general evolution equation for film thickness and the least restrictive conditions for its validity. Results of numerical simulations of the dissipative-dispersive evolution equation indicate that novel, more complex type of spatiotemporal patterns can exist for strange attractors of nonequilibrium systems. It is suggested that real-life experiments satisfying the validity conditions of this theory are possible.

  18. Thin films flowing down inverted substrates: two dimensional flow

    CERN Document Server

    Lin, Te-sheng

    2009-01-01

    We consider free surface instabilities of films flowing on inverted substrates within the framework of lubrication approximation. We allow for the presence of fronts and related contact lines, and explore the role which they play in instability development. It is found that a contact line, modeled by a commonly used precursor film model, leads to free surface instabilities of convective type without any additional natural or excited perturbations. A single parameter D=(3Ca)^{1/3}cot\\alpha, where Ca is the capillary number and \\alpha is the inclination angle, is identified as a governing parameter in the problem. This parameter may be interpreted to reflect the combined effect of inclination angle, film thickness, Reynolds number and the fluid flux. Variation of D leads to change of the wave-like properties of the instabilities, allowing to observe traveling wave behavior, mixed waves, and the waves resembling solitary ones.

  19. Comparison of turbulent particle dispersion models in turbulent shear flows

    Directory of Open Access Journals (Sweden)

    S. Laín

    2007-09-01

    Full Text Available This work compares the performance of two Lagrangian turbulent particle dispersion models: the standard model (e.g., that presented in Sommerfeld et al. (1993, in which the fluctuating fluid velocity experienced by the particle is composed of two components, one correlated with the previous time step and a second one randomly sampled from a Wiener process, and the model proposed by Minier and Peirano (2001, which is based on the PDF approach and performs closure at the level of acceleration of the fluid experienced by the particle. Formulation of a Langevin equation model for the increments of fluid velocity seen by the particle allows capturing some underlying physics of particle dispersion in general turbulent flows while keeping the mathematical manipulation of the stochastic model simple, thereby avoiding some pitfalls and simplifying the derivation of macroscopic relations. The performance of both dispersion models is tested in the configurations of grid-generated turbulence (Wells and Stock (1983 experiments, simple shear flow (Hyland et al., 1999 and confined axisymmetric jet flow laden with solids (Hishida and Maeda (1987 experiments.

  20. Flows in films and over flippers

    Science.gov (United States)

    van Nierop, Ernst Adriaan

    Three topics in fluid mechanics are dealt with in this dissertation, namely (i) reactive spreading and recoil of oil on water, (ii) free film formation theory and experiment, and (iii) how humpback whale flippers delay stall. Reactive spreading of an oil droplet on water is described in Chapter 1. Small amounts of acid and base were added to the oil and water respectively, such that a surfactant was produced at the interface between the oil and the water, greatly enhancing spreading rates. After the oil drop spreads out to some maximum radius, the drop recoils on a timescale that is indicative of a diffusive process redistributing the surfactant over the entire volume of water. In Chapter 2, the theory of soap film formation by withdrawal from a bath of soapy liquid is reviewed, and the assumptions supporting Frankel's law are challenged. Stress balances that describe film evolution in either extensional or shear flow are rigorously derived and we find that the strength of surface stress terms pick the resulting flow type. With this background in mind, we describe in Chapter 3 how films were made using aqueous solutions of poly(ethylene oxide) or PEO with and without surfactant. The initial thickness of these films agrees well with existing data in the literature for overlapping ranges of the capillary number Ca. For larger Ca numbers, we observe that (i) the addition of SDS results in thinner films, (ii) films can be made that are thicker than the wire thickness, and (iii) films swell in thickness when the withdrawal process stops. Some potential mechanisms are described to explain the novel swelling phenomenon. Finally, in Chapter 4, we model the bumpy flipper of a humpback whale as a perturbed elliptic wing with Joukowski profiles of varying chord length, and combine this with lifting line theory as well as experimental stall characteristics of smooth wings. This model shows that the perturbations rearrange the downwash distribution on the wing, smoothing the

  1. Axial dispersion in segmented gas-liquid flow: Effects of alternating channel curvature

    Science.gov (United States)

    Muradoglu, Metin

    2010-12-01

    The effects of channel curvature on the axial dispersion in segmented gas-liquid flows are studied computationally in a two-dimensional setting using a finite-volume/front-tracking method. Passive tracer particles are used to visualize and quantify the axial dispersion. The molecular diffusion is modeled by random walk of tracer particles. It is found that there is significant axial dispersion in serpentine channels even in the absence of molecular diffusion. The lubricating thin liquid layer that persists on the wall of a straight channel is periodically broken in the serpentine channel leading to enhanced axial dispersion. It is also found that the axial dispersion is always larger in the serpentine channel than that in the straight channel but the effects of channel curvature are more pronounced at high Peclet numbers, i.e., Pe>104. A model is proposed based on the difference between the liquid film thicknesses on the inner and outer side of the bend in the limit as Pe→∞. Good agreement is found between the computational results and the model when the liquid slug is well mixed by the chaotic advection.

  2. Low-Flow Film Boiling Heat Transfer on Vertical Surfaces

    DEFF Research Database (Denmark)

    Munthe Andersen, J. G.; Dix, G. E.; Leonard, J. E.

    1976-01-01

    The phenomenon of film boiling heat transfer for high wall temperatures has been investigated. Based on the assumption of laminar flow for the film, the continuity, momentum, and energy equations for the vapor film are solved and a Bromley-type analytical expression for the heat transfer...... length, an average film boiling heat transfer coefficient is obtained....

  3. Comparative Study Between Dispersive and Non-Dispersive Dielectric Permittivity in Spectral Remittances of Chiral Sculptured Zirconia Thin Films

    CERN Document Server

    Babaei, Ferydon; 10.1016/j.optcom.2008.02.012

    2010-01-01

    The transmission and reflection spectra from a right-handed chiral sculptured zirconia thin film are calculated using the piecewise homogeneity approximation method and the Bruggeman homogenization formalism by considering that the propagation of both dispersive and non-dispersive dielectric function occurs for axial and non-axial states. The comparison of spectral results shows that the dispersion of the dielectric function has a considerable effect on the results. In axial excitation of cross-polarized reflectances and co-polarized transmittances the dispersion effect becomes more pronounced at wavelengths further away from the homogenization wavelength. This is also true in case of non-axial excitation of circular transmittances, while there are considerable differences for cross-polarized reflectances where (wavelength) the first Bragg peak occurs. At wavelengths in the vicinity of the homogenization wavelength the dispersion effect of the dielectric function in becomes more significant.

  4. Tailoring the dispersion behavior of optical nanowires with intercore-cladding lithium niobate thin film.

    Science.gov (United States)

    He, Hairong; Miao, Lili; Jiang, Guobao; Zhao, Chujun; Wen, Shuangchun

    2015-10-19

    The dispersion properties of silica and silicon subwavelength-diameter wires with intercore-cladding uniaxial dielectric lithium niobate thin film has been studied numerically in detail. The waveguide dispersion shifts centered around 1550-nm wavelength have been investigated. It shows that the dispersion of optical nanowires with intercore-cladding lithium niobate thin film is highly sensitive to fiber geometry. Moreover, with applied electric field, considerable dispersion shifts without changing its geometric structure can be obtained. Our work may provide an inroad for developing miniaturized functional optoelectronic devices.

  5. Phase thickness approach for determination of thin film refractive index dispersion from transmittance spectra

    Science.gov (United States)

    Nenkov, M. R.; Pencheva, T. G.

    2008-06-01

    A novel approach for determination of refractive index dispersion n(λ ) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate and titanium oxide thin films are investigated and their n(λ ) and d are calculated. The approach is validated using Swanepoel's method and it is found to be applicable for relatively thinner films when measured transmittance spectra have one minimum and one maximum only.

  6. Modeling of dilute and dense dispersed fluid-particle flow

    Energy Technology Data Exchange (ETDEWEB)

    Laux, Harald

    1998-08-01

    A general two-fluid model is derived and applied in CFD computations to various test cases of important industrial multiphase flows. It is general in the sense of its applicability to dilute and dense dispersed fluid-particle flows. The model is limited to isothermal flow without mass transfer and only one particle phase is described. The instantaneous fluid phase equations, including the phase interaction terms, are derived from a volume averaging technique, and the instantaneous particle phase equations are derived from the kinetic theory of granular material. Whereas the averaging procedure, the treatment of the interaction terms, and the kinetic theory approach have been reported in literature prior to this work the combination of the approaches is new. The resulting equations are derived without ambiguity in the interpretation of the particle phase pressure (equation-of-state of particle phase). The basic modeling for the particle phase is improved in two steps. Because in the basic modeling only stresses due to kinetic and collisional interactions are included, a simple model for an effective viscosity is developed in order to allow also frictional stresses within the particle phase. Moreover, turbulent stresses and turbulent dispersion of particles play often an important role for the transport processes. Therefore in a second step, a two-equation turbulence model for both fluid and particle phase turbulence is derived by applying the phasic average to the instantaneous equations. The resulting k-{epsilon}-k{sup d}-{epsilon}{sup d} model is new. Mathematical closure is attempted such that the resulting set of equations is valid for both dilute arid dense flows. During the development of the closure relations a clear distinction is made between granular or ''viscous'' microscale fluctuations and turbulent macro scale fluctuations (true particle turbulence) within the particle phase. The set of governing equations is discretized by using a

  7. Turbulent Dispersion of Film Coolant and Hot Streaks in a Turbine Vane Cascade

    Science.gov (United States)

    2015-01-18

    configuration due to the large amounts of turning in the test section geometry and measurement techniques such as hot wire anemometry or temperature probe...Approved for Public Release; Distribution Unlimited Final Report: Turbulent Dispersion of Film Coolant and Hot Streaks in a Turbine Vane Cascade The...reviewed journals: Final Report: Turbulent Dispersion of Film Coolant and Hot Streaks in a Turbine Vane Cascade Report Title Magnetic resonance

  8. Studies of Tracer Dispersion and Fluid Flow in Porous Media

    Energy Technology Data Exchange (ETDEWEB)

    Rage, T.

    1996-12-31

    This doctoral thesis explores the connection between the topology of a porous medium and its macroscopic transport properties and is based on computerized simulation. In porous media, both diffusion and convection contribute to the dispersion of a tracer and their combined effect is emphasized. The governing equations are solved numerically, using finite differences and Monte Carlo technique. The influence of finite Reynolds number on the outcome of echo-experiments is discussed. Comparing experiments and simulations it is found that nonlinear inertial forces lead to a visible deformation of a returned tracer at surprisingly small Reynolds numbers. In a study of tracer dispersion and fluid flow in periodic arrays of discs it is demonstrated that the mechanisms of mechanical dispersion in periodic media and in natural (non-periodic) porous media are essentially different. Measurements of the percolation probability distribution of a sandstone sample is presented. Local porosity theory predicts that this simple geometric function of a porous medium is of dominant importance for its macroscopic transport properties. It is demonstrated that many aspects of transport through fractures can be studied by using simple but realistic models and readily available computer resources. An example may be the transport of hydrocarbon fluids from the source rock to a reservoir. 165 refs., 44 figs., 1 table

  9. Hierarchical opal grating films prepared by slide coating of colloidal dispersions in binary liquid media.

    Science.gov (United States)

    Lee, Wonmok; Kim, Seulgi; Kim, Seulki; Kim, Jin-Ho; Lee, Hyunjung

    2015-02-15

    There are active researches on well ordered opal films due to their possible applications to various photonic devices. A recently developed slide coating method is capable of rapid fabrication of large area opal films from aqueous colloidal dispersion. In the current study, the slide coating of polystyrene colloidal dispersions in water/i-propanol (IPA) binary media is investigated. Under high IPA content in a dispersing medium, resulting opal film showed a deterioration of long range order, as well as a decreased film thickness due to dilution effect. From the binary liquid, the dried opal films exhibited the unprecedented topological groove patterns with varying periodic distances as a function of alcohol contents in the media. The groove patterns were consisted of the hierarchical structures of the terraced opal layers with periodic thickness variations. The origin of the groove patterns was attributed to a shear-induced periodic instability of colloidal concentration within a thin channel during the coating process which was directly converted to a groove patterns in a resulting opal film due to rapid evaporation of liquid. The groove periods of opal films were in the range of 50-500 μm, and the thickness differences between peak and valley of the groove were significantly large enough to be optically distinguishable, such that the coated films can be utilized as the optical grating film to disperse infra-red light. Utilizing a lowered hydrophilicity of water/IPA dispersant, an opal film could be successfully coated on a flexible Mylar film without significant dewetting problem.

  10. Selective scattering polymer dispersed liquid crystal film for light enhancement of organic light emitting diode.

    Science.gov (United States)

    Jiang, Jinghua; McGraw, Greg; Ma, Ruiqing; Brown, Julie; Yang, Deng-Ke

    2017-02-20

    We developed a novel light enhancing film for an organic light emitting diode (OLED) based on polymer dispersed liquid crystal (PDLC). In the film, the liquid crystal droplets are unidirectionally aligned along the film normal direction and exhibit selective scattering. The film scatters light emitted only in directions with large incident angles but not light emitted in directions with small incident angles. When the light is scattered, it changes propagation direction and exits the OLED. The PDLC film reduces the total internal reflection and thus can significantly increase the light efficiency of the OLED.

  11. Flow and axial dispersion in a sinusoidal-walled tube: Effects of inertial and unsteady flows

    Science.gov (United States)

    Richmond, Marshall C.; Perkins, William A.; Scheibe, Timothy D.; Lambert, Adam; Wood, Brian D.

    2013-12-01

    In this work, we consider a sinusoidal-walled tube (a three-dimensional tube with sinusoidally-varying diameter) as a simplified conceptualization of flow in porous media. Direct numerical simulation using computational fluid dynamics (CFD) methods was used to compute velocity fields by solving the Navier-Stokes equations, and also to numerically solve the volume averaging closure problem, for a range of Reynolds numbers (Re) spanning the low-Re to inertial flow regimes, including one simulation at Re=449 for which unsteady flow was observed. The longitudinal dispersion observed for the flow was computed using a random walk particle tracking method, and this was compared to the longitudinal dispersion predicted from a volume-averaged macroscopic mass balance using the method of volume averaging; the results of the two methods were consistent. Our results are compared to experimental measurements of dispersion in porous media and to previous theoretical results for both the low-Re, Stokes flow regime and for values of Re representing the steady inertial regime. In the steady inertial regime, a power-law increase in the effective longitudinal dispersion (DL) with Re was found, and this is consistent with previous results. This rapid rate of increase is caused by trapping of solute in expansions due to flow separation (eddies). One unsteady (but non-turbulent) flow case (Re=449) was also examined. For this case, the rate of increase of DL with Re was smaller than that observed at lower Re. Velocity fluctuations in this regime lead to increased rates of solute mass transfer between the core flow and separated flow regions, thus diminishing the amount of tailing caused by solute trapping in eddies and thereby reducing longitudinal dispersion. The observed tailing was further explored through analysis of concentration skewness (third moment) and its assymptotic convergence to conventional advection-dispersion behavior (skewness = 0). The method of volume averaging was

  12. Determination of dispersion parameters of thermally deposited CdTe thin film

    Science.gov (United States)

    Dhimmar, J. M.; Desai, H. N.; Modi, B. P.

    2016-05-01

    Cadmium Telluride (CdTe) thin film was deposited onto glass substrates under a vacuum of 5 × 10-6 torr by using thermal evaporation technique. The prepared film was characterized for dispersion analysis from reflectance spectra within the wavelength range of 300 nm - 1100 nm which was recorded by using UV-Visible spectrophotometer. The dispersion parameters (oscillator strength, oscillator wavelength, high frequency dielectric constant, long wavelength refractive index, lattice dielectric constant and plasma resonance frequency) of CdTe thin film were investigated using single sellimeir oscillator model.

  13. Flux Pinning Effects of Y2O3 Nanoparticulate Dispersions in Multilayered YBCO Thin Films

    Science.gov (United States)

    2012-02-01

    AFRL-RZ-WP-TP-2012-0090 FLUX PINNING EFFECTS OF Y2O3 NANOPARTICULATE DISPERSIONS IN MULTILAYERED YBCO THIN FILMS (POSTPRINT) T.A...January 2005 4. TITLE AND SUBTITLE FLUX PINNING EFFECTS OF Y2O3 NANOPARTICULATE DISPERSIONS IN MULTILAYERED YBCO THIN FILMS (POSTPRINT) 5a...Clearance Date: 06 Dec 2005. 14. ABSTRACT The flux pinning effects of Y2O3 nanoparticulate inclusions in YBa2Cu3O7-δ (Y123 or YBCO ) thin films

  14. Determination of the solvation film thickness of dispersed particles with the method of Einstein viscosity equation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The dispersion of a solid particle in a liquid may lead to the formation of solvation film onthe particle surface, which can strongly increase the repulsive force between particles and thus strongly affect the stability of dispersions. The solvation film thickness, which varies with the variation of the property of suspension particles and solutions, is one of the most important parameters of the solvation film, and is also one of the most difficult parameters that can be measured accurately. In this paper, a method, based on the Einstein viscosity equation of dispersions, for determining the solvation film thickness of particles is developed. This method was tested on two kinds of silica spherical powders (namely M1 and M2) dispersed in ethyl alcohol, in water, and in a water-ethyl alcohol mixture (1:1 by volume) through measuring the relative viscosity of dispersions of the particles as a function of the volume fraction of the dry particles in the dispersion, and of the specific surface area and the density of the particles. The calculated solvation film thicknesses on M1 are 7.48, 18.65 and 23.74 nm in alcohol, water and the water-ethyl alcohol mixture, 12.41, 12.71 and 13.13 nm on M2 in alcohol, water and the water-ethyl alcohol mixture, respectively.

  15. Modeling of dilute and dense dispersed fluid-particle flow

    Energy Technology Data Exchange (ETDEWEB)

    Laux, Harald

    1998-08-01

    A general two-fluid model is derived and applied in CFD computations to various test cases of important industrial multiphase flows. It is general in the sense of its applicability to dilute and dense dispersed fluid-particle flows. The model is limited to isothermal flow without mass transfer and only one particle phase is described. The instantaneous fluid phase equations, including the phase interaction terms, are derived from a volume averaging technique, and the instantaneous particle phase equations are derived from the kinetic theory of granular material. Whereas the averaging procedure, the treatment of the interaction terms, and the kinetic theory approach have been reported in literature prior to this work the combination of the approaches is new. The resulting equations are derived without ambiguity in the interpretation of the particle phase pressure (equation-of-state of particle phase). The basic modeling for the particle phase is improved in two steps. Because in the basic modeling only stresses due to kinetic and collisional interactions are included, a simple model for an effective viscosity is developed in order to allow also frictional stresses within the particle phase. Moreover, turbulent stresses and turbulent dispersion of particles play often an important role for the transport processes. Therefore in a second step, a two-equation turbulence model for both fluid and particle phase turbulence is derived by applying the phasic average to the instantaneous equations. The resulting k-{epsilon}-k{sup d}-{epsilon}{sup d} model is new. Mathematical closure is attempted such that the resulting set of equations is valid for both dilute arid dense flows. During the development of the closure relations a clear distinction is made between granular or ''viscous'' microscale fluctuations and turbulent macro scale fluctuations (true particle turbulence) within the particle phase. The set of governing equations is discretized by using a

  16. Impact of Droplets on Inclined Flowing Liquid Films

    CERN Document Server

    Che, Zhizhao; Matar, Omar K

    2015-01-01

    The impact of droplets on an inclined falling liquid film is studied experimentally using high-speed imaging. The falling film is created on a flat substrate with controllable thicknesses and flow rates. Droplets with different sizes and speeds are used to study the impact process under various Ohnesorge and Weber numbers, and film Reynolds numbers. A number of phenomena associated with droplet impact are identified and analysed, such as bouncing, partial coalescence, total coalescence, and splashing. The effects of droplet size, speed, as well the film flow rate are studied culminating in the generation of an impact regime map. The analysis of the lubrication force acted on the droplet via the gas layer shows that a higher flow rate in the liquid film produces a larger lubrication force, slows down the drainage process, and increases the probability of droplet bouncing. Our results demonstrate that the flowing film has a profound effect on the droplet impact process and associated phenomena, which are marked...

  17. Solute dispersion in open channel flow with bed absorption

    Science.gov (United States)

    Wang, Ping; Chen, G. Q.

    2016-12-01

    Reactive solute dispersion is of essential significance in various ecological and environmental applications. It is only qualitatively known that boundary absorption depletes pollutant around the boundary and reduces the concentration nearby. All the existing studies on this topic have been focused on the longitudinally distributed mean concentration, far from enough to fully characterize the transport process with tremendous cross-sectional concentration nonuniformity. This work presents an analytical study of the evolution of two-dimensional concentration distribution for solute dispersion in a laminar open channel flow with bed absorption. The fourth order Aris-Gill expansion proposed in our previous study (Wang and Chen, 2016b) is further extended for the case with bed absorption to cover the transitional effects of skewness and kurtosis. Results reveal the extremely nonuniform cross-sectional concentration distribution, and demonstrate that concentration at the bed instead of the mean should be used for reliable quantification of the absorption flux. The accurate two-dimensional concentration distribution presented in this study brings important environmental implications such as risk assessment associated with peak concentration position and duration of toxic pollutant cloud in open channel waters.

  18. Hydromagnetic thin film flow: Linear stability

    KAUST Repository

    Amaouche, Mustapha

    2013-08-30

    This paper deals with the long wave instability of an electroconductor fluid film, flowing down an inclined plane at small to moderate Reynolds numbers, under the action of electromagnetic fields. A coherent second order long wave model and two simplified versions of it, referred to as first and second reduced models (FRM and SRM), are proposed to describe the nonlinear behavior of the flow. The modeling procedure consists of a combination of the lubrication theory and the weighted residual approach using an appropriate projection basis. A suitable choice of weighting functions allows a significant reduction of the dimension of the problem. The full model is naturally unique, i.e., independent of the particular form of the trial functions. The linear stability of the problem is investigated, and the influence of electromagnetic field on the flow stability is analyzed. Two cases are considered: the applied magnetic field is either normal or parallel to the fluid flow direction, while the electric field is transversal. The numerical solution of the Orr-Sommerfeld (OS) eigenvalue problem and those of the depth averaging model are used to assess the accuracy of the reduced models. It is found that the current models have the advantage of the Benney-like model, which is known to asymptote the exact solution near criticality. Moreover, far from the instability threshold, the current reduced models continue to follow the OS solution up to moderate Reynolds numbers, while the averaging model diverges rapidly. The model SRM gives better results than FRM beyond sufficiently high Reynolds numbers.

  19. Optical constants and their dispersion of Ag-MgF2 nanoparticle composite films

    Institute of Scientific and Technical Information of China (English)

    Zhaoqi Sun(孙兆奇); Daming Sun(孙大明)

    2004-01-01

    Ag-MgF2 composite films with different Ag fractions were prepared through a co-evaporation method.Microstructure analysis shows that the films are composed of amorphous MgF2 matrix and embedded fcc-Ag nanoparticles. The optical constants and their dispersion of the films, within the wavelength range of 250 - 650 nm, were measured by reflecting spectroscopic ellipsometry. The maximum of the imaginary part ε" of the complex dielectric permittivity attributing to the surface plasmon resonance polarization of the Ag nanoparticles in an Ag-MgF2 film, and the tangent of the phase-shift angle δ resulting from the dielectric loss of the film, occur at λ = 435 nm and λ = 420 nm, respectively. Based on Maxwell-Garnett effective medium theory, the experimentally observed dispersion spectra were reasonably described.

  20. Going against the flow: a case for upstream dispersal and detection of uncommon dispersal events

    NARCIS (Netherlands)

    Wubs, E.R.J.; Fraaije, Rob G.A.; Groot, de G.A.; Erkens, R.H.J.; Garsen, Annemarie G.; Kleyheeg, Erik; Raven, Bart M.; Soons, Merel B.

    2016-01-01

    1.Dispersal and colonisation are key processes determining species survival, and their importance is increasing as a consequence of ongoing habitat fragmentation, land-use change and climate change. Identification of long-distance dispersal events, including upstream dispersal, and of the dispersal

  1. Going against the flow: a case for upstream dispersal and detection of uncommon dispersal events

    NARCIS (Netherlands)

    Wubs, E. R. Jasper; Fraaije, Rob G. A.; de Groot, G. Arjen; Erkens, Roy H. J.; Garssen, Annemarie G.; Kleyheeg, Erik; Raven, Bart M.; Soons, Merel B.

    2016-01-01

    * Dispersal and colonisation are key processes determining species survival, and their importance is increasing as a consequence of ongoing habitat fragmentation, land-use change and climate change. Identification of long-distance dispersal events, including upstream dispersal, and of the dispersal

  2. Methanol electrooxidation on Pt particles dispersed into PANI/SWNT composite films

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Gang; Li, Li; Li, Jing-Hong; Xu, Bo-Qing [Innovative Catalysis Program, Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084 (China)

    2006-04-21

    Conducting polymer composite films comprised of polyaniline (PANI) and single wall carbon nanotubes (SWNT) was prepared by electrochemical codeposition during the electropolymerization in an aniline solution with suspending SWNT. The fabricated composite films are assessed with respect to their potential application as support materials in Pt electrocatalyst for electrochemical oxidation of methanol. The PANI/SWNT composite film incorporated with SWNT has a higher polymeric degree and lower defect density in PANI structure than PANI film. Furthermore, the incorporation of SWNT also leads to higher electrochemically accessible surface areas (S{sub a}), electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces, which make higher dispersion and utilization for deposited Pt. Therefore, the Pt particles electrodeposited on PANI/SWNT composite polymer film exhibits excellent catalytic activity and stability for the electrooxidation of methanol in comparison to Pt supported on PANI film, which reveals that the composite film is more promising for application in electrocatalyst as a support material. (author)

  3. Comparison of physicomechanical properties of films prepared from organic solutions and aqueous dispersion of Eudragit RL

    Directory of Open Access Journals (Sweden)

    H Afrasiabi Garekani

    2011-05-01

    Full Text Available Background and the purpose of the study: Mechanical properties of films prepared from aqueous dispersion and organic solutions of Eudragit RL were assessed and the effects of plasticizer type, concentration and curing were examined. Methods: Films were prepared from aqueous dispersion and solutions of Eudragit RL (isopropyl alcohol-water 9:1 containing 0, 10 or 20% (based on polymer weight of PEG 400 or Triethyl Citrate (TEC as plasticizer using casting method. Samples of films were stored in oven at 60ºC for 24 hrs (Cured. The stress-strain curve was obtained for each film using material testing machine and tensile strength, elastic modulus, %elongation and work of failure were calculated. Results and major conclusion: The films with no plasticizer showed different mechanical properties depending on the vehicle used. Addition of 10% or 20% of plasticizer decreased the tensile strength and elastic modulus and increased %elongation and work of failure for all films. The effect of PEG400 on mechanical properties of Eudragit RL films was more pronounced. The differences in mechanical properties of the films due to vehicle decreased by addition of plasticizer and increase in its concentration. Curing process weakened the mechanical properties of the films with no plasticizer and for films with 10% plasticizer no considerable difference in mechanical properties was observed before and after curing. For those with 20% plasticizer only films prepared from aqueous dispersion showed remarkable difference in mechanical properties before and after curing. Results of this study suggest that the mechanical properties of the Eudragit RL films were affected by the vehicle, type of plasticizer and its concentration in the coating liquid.

  4. Influence of nitrogen flow rates on materials properties of CrN films grown by reactive magnetron sputtering

    Indian Academy of Sciences (India)

    B Subramanian; K Prabakaran; M Jayachandran

    2012-08-01

    Chromium nitride (CrN) hard thin films were deposited on different substrates by reactive direct current (d.c.) magnetron sputtering with different nitrogen flow rates. The X-ray diffraction patterns showed mixed Cr2N and CrN phases. The variations in structural parameters are discussed. The grain size increased with increasing nitrogen flow rates. Scanning electron microscopy image showed columnar and dense microstructure with varying nitrogen flow rates. An elemental analysis of the samples was realized by means of energy dispersive spectroscopy. The electrical studies indicated the semiconducting behaviour of the films at the nitrogen flow rate of 15 sccm.

  5. Large-Eddy Simulation on turbulent flow and plume dispersion over a 2-dimensional hill

    Science.gov (United States)

    Nakayama, H.; Nagai, H.

    2010-05-01

    The dispersion analysis of airborne contaminants including radioactive substances from industrial or nuclear facilities is an important issue for air quality maintenance and safety assessment. In Japan, many nuclear power plants are located at complex coastal terrains. In these cases, terrain effects on the turbulent flow and plume dispersion should be investigated. In this study, we perform Large-Eddy Simulation (LES) of turbulent flow and plume dispersion over a 2-dimensional hill flow and investigate the characteristics of mean and fluctuating concentrations.

  6. Refractive index dispersion of swift heavy ion irradiated BFO thin films using Surface Plasmon Resonance technique

    Energy Technology Data Exchange (ETDEWEB)

    Paliwal, Ayushi [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Sharma, Savita [Department of Applied Physics, Delhi Technological University, Delhi (India); Tomar, Monika [Physics Department, Miranda House, University of Delhi, Delhi 110007 (India); Singh, Fouran [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110075 (India); Gupta, Vinay, E-mail: drguptavinay@gmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2016-07-15

    Highlights: • Investigated the optical properties of BiFeO{sub 3} (BFO) thin films after irradiation using SPR. • Otto configuration has been used to excite the surface plasmons using gold metal thin film. • BFO thin films were prepared by sol–gel spin coating technique. • Examined the refractive index dispersion of pristine and irradiated BFO thin film. - Abstract: Swift heavy ion irradiation (SHI) is an effective technique to induce defects for possible modifications in the material properties. There is growing interest in studying the optical properties of multiferroic BiFeO{sub 3} (BFO) thin films for optoelectronic applications. In the present work, BFO thin films were prepared by sol–gel spin coating technique and were irradiated using the 15 UD Pelletron accelerator with 100 MeV Au{sup 9+} ions at a fluence of 1 × 10{sup 12} ions cm{sup −2}. The as-grown films became rough and porous on ion irradiation. Surface Plasmon Resonance (SPR) technique has been identified as a highly sensitive and powerful technique for studying the optical properties of a dielectric material. Optical properties of BFO thin films, before and after irradiation were studied using SPR technique in Otto configuration. Refractive index is found to be decreasing from 2.27 to 2.14 on ion irradiation at a wavelength of 633 nm. Refractive index dispersion of BFO thin film (from 405 nm to 633 nm) before and after ion radiation was examined.

  7. Gene Flow and the Measurement of Dispersal in Plant Populations.

    Science.gov (United States)

    Nicholls, Marc S.

    1986-01-01

    Reviews methods of estimating pollen and seed dispersals and discusses the extent and frequency of gene exchange within and between populations. Offers suggestions for designing exercises suitable for estimating dispersal distances in natural plant populations. (ML)

  8. Dispersion of swimming algae in laminar and turbulent channel flows: theory and simulations

    CERN Document Server

    Croze, O A; Ahmed, M; Bees, M A; Brandt, L

    2012-01-01

    Algal swimming is often biased by environmental cues, e.g. gravitational and viscous torques drive cells towards downwelling fluid (gyrotaxis). In view of biotechnological applications, it is important to understand how such biased swimming affects cell dispersion in a flow. Here, we study the dispersion of gyrotactic swimming algae in laminar and turbulent channel flows. By direct numerical simulation (DNS) of cell motion within upwelling and downwelling channel flows, we evaluate time-dependent measures of dispersion for increasing values of the flow Peclet (Reynolds) numbers, Pe (Re). Furthermore, we derive an analytical `swimming Taylor-Aris dispersion' theory, using flow-dependent transport parameters given by existing microscopic models. In the laminar regime, DNS results and analytical predictions compare very well, providing the first confirmation that cells' response to flow is best described by the generalized-Taylor-dispersion microscopic model. We predict that cells drift along a channel faster th...

  9. Photoactive composite films prepared from mixtures of polystyrene microgel dispersions and poly(3-hexylthiophene) solutions.

    Science.gov (United States)

    Chen, Mu; Cui, Zhengxing; Edmondson, Steve; Hodson, Nigel; Zhou, Mi; Yan, Junfeng; O'Brien, Paul; Saunders, Brian R

    2015-11-14

    Whilst polystyrene microgels belong to the oldest family of microgel particles, their behaviours when deposited onto substrates or prepared as composites have received little attention. Because polystyrene microgels are solvent-swellable, and inherently colloidally stable, they are well suited to form composites with conjugated polymers. Here, we investigate the morphology and light absorption properties of spin coated composite films prepared from mixed dispersions of polystyrene microgels and poly(3-hexylthiophene) (P3HT) for the first time. We compare the morphologies of the composite films to spin coated microgel films. The films were studied using optical microscopy, SEM, AFM, wide-angle X-ray diffraction and UV-visible spectroscopy. The films contained flattened microgel particles with an aspect ratio of ∼10. Microgel islands containing hexagonally close packed particles were evident for both the pure microgel and microgel/P3HT composite films. The latter were electrically conducting. The composite film morphology was dependent on the microgel and P3HT concentration used for film preparation and a morphology phase diagram was constructed. The P3HT phase acted as an electrically conducting cement and increased the robustness of the films to solvent washing. The composite films were photoactive due to the P3HT component. The absorbance for the films was tuneable and increased linearly with both microgel and P3HT concentration. The results of the study should apply to other organic swellable microgel/conjugated polymer combinations and may lead to new colloidal composites for future optoelectronic applications.

  10. Theoretical research on rotational dispersion coefficient of fiber in turbulent shear flow of fiber suspension

    Institute of Scientific and Technical Information of China (English)

    GAO Zhen-yu; LIN Jian-zhong; LI Jun

    2007-01-01

    The rotational dispersion coefficient of the fiber in the turbulent shear flow of fiber suspension was studied theoretically. The function of correlation moment between the different fluctuating velocity gradients of the flow was built firstly. Then the expression, dependent on the characteristic length, time, velocity and a dimensionless parameter related to the effect of wall, of rotational dispersion coefficient is derived. The derived expression of rotational dispersion coefficient can be employed to the inhomogeneous and non-isotropic turbulent flows. Furthermore it can be expanded to three-dimensional turbulent flows and serves the theoretical basis for solving the turbulent flow of fiber suspension.

  11. Particle dispersion models and drag coefficients for particles in turbulent flows

    Science.gov (United States)

    Crowe, C. T.; Chung, J. N.; Troutt, T. R.

    1988-01-01

    Some of the concepts underlying particle dispersion due to turbulence are reviewed. The traditional approaches to particle dispersion in homogeneous, stationary turbulent fields are addressed, and recent work on particle dispersion in large scale turbulent structures is reviewed. The state of knowledge of particle drag coefficients in turbulent gas-particle flows is also reviewed.

  12. Effects of UV-blocking films on the dispersal behavior of Encarsia formosa (Hymenoptera: Aphelinidae).

    Science.gov (United States)

    Doukas, Dimitrios; Payne, Christopher C

    2007-02-01

    The parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) has been used successfully for the control of Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae). The development of UV-blocking plastic films has added a new component to future integrated pest management systems by disrupting insect pest infestation when UV light is excluded. Because both T. vaporariorum and E. formosa are reported to have similar spectral efficiency, there was a need to identify the impact of UV-blocking films on the dispersal behavior of both the pest and the natural enemy. In field studies, using choice-chamber experiments, E. formosa showed some preference to disperse into compartments where less UV light was blocked. However, further studies indicated that the effect was primarily attributable to the different light diffusion properties of the films tested. Thus, unlike its whitefly host, when the UV-absorbing properties of the films were similar, but the light diffusion properties differed, E. formosa adults preferred to disperse into compartments clad with films that had high light diffusion properties. When the plastic films differed most in their UV-absorbing capacity and had no light-diffusion capability, the initial dispersal of E. formosa between treatments was similar, although a small preference toward the environment with UV light was observed over time. When parasitoid dispersal was measured 3 h after release, more parasitoids were found on plants, suggesting that the parasitoids would search plants for whitefly hosts, even in a UV-blocked light environment. The potential for the integration of UV-blocking films with E. formosa in an advanced whitefly management system is discussed.

  13. MHD Effect of Liquid Metal Film Flows as Plasma-Facing Components

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiujie; XU Zengyu; PAN Chuanjie

    2008-01-01

    Stability of liquid metal film flow under gradient magnetic field is investigated. Three dimensional numerical simulations on magnetohydrodynamics (MHD) effect of free surface film flow were carried out, with emphasis on the film thickness variation and its surface stability. Three different MHD phenomena of film flow were observed in the experiment, namely, retardant, rivulet and flat film flow. From our experiment and numerical simulation it can be concluded that flat film flow is a good choice for plasma-facing components (PFCs)

  14. Chemotaxis and flow disorder shape microbial dispersion in porous media

    Science.gov (United States)

    De Anna, Pietro; Yawata, Yutaka; Stocker, Roman; Juanes, Ruben

    2017-04-01

    Bacteria drive a plethora of natural processes in the subsurface, consuming organic matter and catalysing chemical reactions that are key to global elemental cycles. These macro-scale consequences result from the collective action of individual bacteria at the micro-scale, which are modulated by the highly heterogeneous subsurface environment, dominated by flow disorder and strong chemical gradients. Yet, despite the generally recognized importance of these microscale processes, microbe-host medium interaction at the pore scale remain poorly characterized and understood. Here, we introduce a microfluidic model system to directly image and quantify the role of cell motility on bacterial dispersion and residence time in confined, porous, media. Using the soil-dwelling bacterium Bacillus subtilis and the common amino acid serine as a resource, we observe that chemotaxis in highly disordered and confined physico-chemical environment affords bacteria an increase in their ability to persistently occupy the host medium. Our findings illustrate that the interplay between bacterial behaviour and pore-scale disorder in fluid velocity and nutrient concentration directly impacts the residence time, transport and bio-geo-chemical transformation rates of biota in the subsurface, and thus likely the processes they mediate.

  15. Photochromic Properties of Tungsten Oxide/Methylcellulose Composite Film Containing Dispersing Agents.

    Science.gov (United States)

    Yamazaki, Suzuko; Ishida, Hiroki; Shimizu, Dai; Adachi, Kenta

    2015-12-02

    Tungsten oxide-based photochromic films which changed reversibly in air between colorless- transparent in the dark and dark blue under UV irradiation were prepared by using methylcellulose as a film matrix and polyols such as ethylene glycol (EG), propylene glycol (PG), and glycerin (Gly) as dispersing agents. Influence of the dispersing agents and water in the films on the photochromic behavior was systematically studied. Under UV irradiation, absorption bands around 640 and 980 nm increased and the coloring rate was the following order: Gly > EG > PG. An increase in the amounts of dispersing agents or water accelerated the coloring rate. By increasing the water content of the film, a new absorption peak appeared at ca. 775 nm and the Raman spectra indicated a shift of W-O-W stretching vibration to lower wavenumber which was due to the formation of hydrogen bonding. All absorption spectra were fit by three Lorentz functions, whose bands were ascribed to various packing of WO6 octahedra. After the light was turned off, the formation of W(5+) was stopped and bleaching occurred by the reaction with O2 in air to recover its original transparent state. We anticipate that the biodegradable photochromic films developed in this study can be applied in recyclable display medium and especially in detachable films for glass windows whose light transmission properties are changed by sunlight, i.e., for usage as an alternative of smart windows without applying voltage.

  16. Thin liquid films dewetting and polymer flow

    CERN Document Server

    Blossey, Ralf

    2012-01-01

    This book is a treatise on the thermodynamic and dynamic properties of thin liquid films at solid surfaces and, in particular, their rupture instabilities. For the quantitative study of these phenomena, polymer thin films haven proven to be an invaluable experimental model system.   What is it that makes thin film instabilities special and interesting, warranting a whole book? There are several answers to this. Firstly, thin polymeric films have an important range of applications, and with the increase in the number of technologies available to produce and to study them, this range is likely to expand. An understanding of their instabilities is therefore of practical relevance for the design of such films.   Secondly, thin liquid films are an interdisciplinary research topic. Interdisciplinary research is surely not an end to itself, but in this case it leads to a fairly heterogeneous community of theoretical and experimental physicists, engineers, physical chemists, mathematicians and others working on the...

  17. Interfacial properties, thin film stability and foam stability of casein micelle dispersions

    NARCIS (Netherlands)

    Chen, Min; Sala, G.; Meinders, M.B.J.; Valenberg, van H.J.F.; Linden, van der E.; Sagis, L.M.C.

    2017-01-01

    Foam stability of casein micelle dispersions (CMDs) strongly depends on aggregate size. To elucidate the underlying mechanism, the role of interfacial and thin film properties was investigated. CMDs were prepared at 4 °C and 20 °C, designated as CMD4 °C and CMD20 °C. At equal protein concentrations,

  18. Dispersion and film-forming properties of poly(acrylic acid)-stabilized carbon nanotubes.

    Science.gov (United States)

    Saint-Aubin, Karell; Poulin, Philippe; Saadaoui, Hassan; Maugey, Maryse; Zakri, Cécile

    2009-11-17

    We present a detailed study of the influence of pH on the dispersion and film-forming properties of poly(acrylic acid)-stabilized carbon nanotubes. Poly(acrylic acid) (PAA) is a weak polyelectrolyte, with a pH-responsive behavior in aqueous solution. We obtain quantitative UV-visible measurements to show that the amount of polyelectrolyte in optimal pH conditions is weak, showing a good efficiency of the polymer as a carbon nanotube dispersing agent. The best dispersion conditions are achieved at pH 5, a value close to the pK(a) of PAA. Apart from this tenuous pH value, the PAA is not efficient at stabilizing nanotubes and atomic force microscopy allows us to explain the delicate balance between the PAA adsorption and the suspension stability. This study finally permits optimal conditions for making homogeneous and conductive composite films to be determined.

  19. Influence of thermocapillary flow in a liquid film jet

    Science.gov (United States)

    Hu, W. R.; Hu, Q.

    2004-01-01

    The higher temperature liquid (or melt) film ejected from a vessel and painted on the moving solid boundary is analyzed. The thermocapillary flow, driven by the gradient of surface tension on the free surface of a liquid film, changes the height profile of the liquid film. Based on the approximations of lubrication theory and perturbation theory, the equation of liquid height and the process of thermal hydrodynamics in the liquid film are solved for a given temperature distribution on the solid boundary and a given heat flux from the vessel. The solution shows clearly the obvious influence of the thermocapillary flow on the thermal hydrodynamic process and the cross-section profile of the liquid film even for a Newtonian fluid. The results may be used to explain the Barus effect or the Die Swell effect.

  20. Theory of rotating electrohydrodynamic flows in a liquid film.

    Science.gov (United States)

    Shiryaeva, E V; Vladimirov, V A; Zhukov, M Yu

    2009-10-01

    The mathematical model of rotating electrohydrodynamic flows in a thin suspended liquid film is proposed and studied. The flows are driven by the given difference of potentials in one direction and constant external electric field E(out) in another direction in the plane of a film. To derive the model, we employ the spatial averaging over the normal coordinate to a film that leads to the average Reynolds stress that is proportional to |E(out)|3. This stress generates tangential velocity in the vicinity of the edges of a film that, in turn, causes the rotational motion of a liquid. The proposed model is used to explain the experimental observations of the liquid film motor.

  1. Dispersion of swimming algae in laminar and turbulent channel flows: consequences for photobioreactors.

    Science.gov (United States)

    Croze, Ottavio A; Sardina, Gaetano; Ahmed, Mansoor; Bees, Martin A; Brandt, Luca

    2013-04-06

    Shear flow significantly affects the transport of swimming algae in suspension. For example, viscous and gravitational torques bias bottom-heavy cells to swim towards regions of downwelling fluid (gyrotaxis). It is necessary to understand how such biases affect algal dispersion in natural and industrial flows, especially in view of growing interest in algal photobioreactors. Motivated by this, we here study the dispersion of gyrotactic algae in laminar and turbulent channel flows using direct numerical simulation (DNS) and a previously published analytical swimming dispersion theory. Time-resolved dispersion measures are evaluated as functions of the Péclet and Reynolds numbers in upwelling and downwelling flows. For laminar flows, DNS results are compared with theory using competing descriptions of biased swimming cells in shear flow. Excellent agreement is found for predictions that employ generalized Taylor dispersion. The results highlight peculiarities of gyrotactic swimmer dispersion relative to passive tracers. In laminar downwelling flow the cell distribution drifts in excess of the mean flow, increasing in magnitude with Péclet number. The cell effective axial diffusivity increases and decreases with Péclet number (for tracers it merely increases). In turbulent flows, gyrotactic effects are weaker, but discernable and manifested as non-zero drift. These results should have a significant impact on photobioreactor design.

  2. Dispersion of swimming algae in laminar and turbulent channel flows: consequences for photobioreactors

    Science.gov (United States)

    Croze, Ottavio A.; Sardina, Gaetano; Ahmed, Mansoor; Bees, Martin A.; Brandt, Luca

    2013-01-01

    Shear flow significantly affects the transport of swimming algae in suspension. For example, viscous and gravitational torques bias bottom-heavy cells to swim towards regions of downwelling fluid (gyrotaxis). It is necessary to understand how such biases affect algal dispersion in natural and industrial flows, especially in view of growing interest in algal photobioreactors. Motivated by this, we here study the dispersion of gyrotactic algae in laminar and turbulent channel flows using direct numerical simulation (DNS) and a previously published analytical swimming dispersion theory. Time-resolved dispersion measures are evaluated as functions of the Péclet and Reynolds numbers in upwelling and downwelling flows. For laminar flows, DNS results are compared with theory using competing descriptions of biased swimming cells in shear flow. Excellent agreement is found for predictions that employ generalized Taylor dispersion. The results highlight peculiarities of gyrotactic swimmer dispersion relative to passive tracers. In laminar downwelling flow the cell distribution drifts in excess of the mean flow, increasing in magnitude with Péclet number. The cell effective axial diffusivity increases and decreases with Péclet number (for tracers it merely increases). In turbulent flows, gyrotactic effects are weaker, but discernable and manifested as non-zero drift. These results should have a significant impact on photobioreactor design. PMID:23407572

  3. Determination of dispersive optical constants of nanocrystalline CdSe (nc-CdSe) thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Kriti; Al-Kabbi, Alaa S.; Saini, G.S.S. [Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh 160014 (India); Tripathi, S.K., E-mail: surya@pu.ac.in [Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh 160014 (India)

    2012-06-15

    Highlights: ► nc-CdSe thin films are prepared by thermal vacuum evaporation technique. ► TEM analysis shows NCs are spherical in shape. ► XRD reveals the hexagonal (wurtzite) crystal structure of nc-CdSe thin films. ► The direct optical bandgap of nc-CdSe is 2.25 eV in contrast to bulk (1.7 eV). ► Dispersion of refractive index is discussed in terms of Wemple–DiDomenico single oscillator model. -- Abstract: The nanocrystalline thin films of CdSe are prepared by thermal evaporation technique at room temperature. These thin films are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). The transmission spectra are recorded in the transmission range 400–3300 nm for nc-CdSe thin films. Transmittance measurements are used to calculate the refractive index (n) and absorption coefficient (α) using Swanepoel's method. The optical band gap (E{sub g}{sup opt}) has been determined from the absorption coefficient values using Tauc's procedure. The optical constants such as extinction coefficient (k), real (ε{sub 1}) and imaginary (ε{sub 2}) dielectric constants, dielectric loss (tan δ), optical conductivity (σ{sub opt}), Urbach energy (E{sub u}) and steepness parameter (σ) are also calculated for nc-CdSe thin films. The normal dispersion of refractive index is described using Wemple–DiDomenico single-oscillator model. Refractive index dispersion is further analysed to calculate lattice dielectric constant (ε{sub L}).

  4. Rewetting and Flow Film Boiling Along Hot Surface

    Institute of Scientific and Technical Information of China (English)

    王补宣Thermal Engineering Department; Tsinghua University; Beijing 100084; PRC; 彭晓峰

    1994-01-01

    The recent investigations on the rewettmg and film boiling of liquid flowing along a hot/heated surface are briefly reviewed and discussed.Some advanced theoretical analyses are conducted and new conclusions achieved.These investigations describe the fundamental characteristics of liquid flow boiling and further the complicated rewetting phenomena,and have resulted in considerable insight intothe mechanism.

  5. LOCAL DISCONTINUOUS GALERKIN METHOD FOR RADIAL POROUS FLOW WITH DISPERSION AND ADSORPTION

    Institute of Scientific and Technical Information of China (English)

    汪继文; 刘慈群

    2004-01-01

    Based on the local discontinuous Galerkin methods for time-dependent convection-diffusion systems newly developed by Corkburn and Shu,according to the form of the generalized convection-diffusion equations which model the radial porous flow with dispersion and adsorption,a local discontinuous Galerkin method for radial porous flow with dispersion and adsorption was developed,a high order accurary new scheme for radial porous flow is obtained.The presented method was applied to the numerical tests of two cases of radial porous,i.e., the convection-dispersion flow and the convection-dispersion-adsorption flow,the corresponding parts of the numerical results are in good agreement with the published solutions,so the presented method is reliable.Reckoning of the computational cost also shows that the method is practicable.

  6. Application of asymmetric flow-field flow fractionation to the characterization of colloidal dispersions undergoing aggregation.

    Science.gov (United States)

    Lattuada, Marco; Olivo, Carlos; Gauer, Cornelius; Storti, Giuseppe; Morbidelli, Massimo

    2010-05-18

    The characterization of complex colloidal dispersions is a relevant and challenging problem in colloidal science. In this work, we show how asymmetric flow-field flow fractionation (AF4) coupled to static light scattering can be used for this purpose. As an example of complex colloidal dispersions, we have chosen two systems undergoing aggregation. The first one is a conventional polystyrene latex undergoing reaction-limited aggregation, which leads to the formation of fractal clusters with well-known structure. The second one is a dispersion of elastomeric colloidal particles made of a polymer with a low glass transition temperature, which undergoes coalescence upon aggregation. Samples are withdrawn during aggregation at fixed times, fractionated with AF4 using a two-angle static light scattering unit as a detector. We have shown that from the analysis of the ratio between the intensities of the scattered light at the two angles the cluster size distribution can be recovered, without any need for calibration based on standard elution times, provided that the geometry and scattering properties of particles and clusters are known. The nonfractionated samples have been characterized also by conventional static and dynamic light scattering to determine their average radius of gyration and hydrodynamic radius. The size distribution of coalescing particles has been investigated also through image analysis of cryo-scanning electron microscopy (SEM) pictures. The average radius of gyration and the average hydrodynamic radius of the nonfractionated samples have been calculated and successfully compared to the values obtained from the size distributions measured by AF4. In addition, the data obtained are also in good agreement with calculations made with population balance equations.

  7. Transient Taylor-Aris dispersion for time-dependent flows in straight channels

    DEFF Research Database (Denmark)

    Vedel, Søren; Bruus, Henrik

    2012-01-01

    –ket formalism, we derive an expression for the effective solute diffusivity valid for transient Taylor–Aris dispersion in any given time-dependent, multi-frequency solvent flow through straight channels. Our theory shows that the solute dispersion may be greatly enhanced by the time-dependent parts of the flow...... recover the known results for steady and single-frequency pulsating flows, and find new, richer structure of the dispersion as function of system parameters in multi-frequency systems. We show that the effective diffusivity is enhanced significantly by those parts of the time-dependent velocity field...

  8. Carbon film deposition from high velocity rarefied flow

    Energy Technology Data Exchange (ETDEWEB)

    Rebrov, A.K., E-mail: rebrov@itp.nsc.ru; Emelyanov, A.A.; Yudin, I.B.

    2015-01-30

    The presented study is based on the idea of the activation of a gas-precursor high velocity flow by hot wire. The wire forms the channel for flow before expansion to substrate. The construction allows change of the specific flow rate, velocity, composition and temperature of a gas mixture by studying the film synthesis in conditions from free molecular to continuum flow at velocities from hundreds to thousands of m/s. At a high pressure, the film has typical and unusual hexagonal incorporations for diamond tetragonal particles. Raman spectrum with the pronounced diamond peak is typical for diamond-like film. X-ray diffraction points in the presence of lonsdaleite. Conditions of deposition were simulated by Monte Carlo method. Collisions with hot surfaces and chemical transformations were taken into consideration as well.

  9. Cross-linkage effect of cellulose/laponite hybrids in aqueous dispersions and solid films.

    Science.gov (United States)

    Yuan, Zaiwu; Fan, Qingrui; Dai, Xiaonan; Zhao, Chao; Lv, Aijie; Zhang, Jingjing; Xu, Guiying; Qin, Menghua

    2014-02-15

    Homogenous cellulose/laponite aqueous dispersions and composite films were respectively prepared from the pre-cooling NaOH/urea aqueous systems. Rheological measurements of aqueous dispersions demonstrated a sol-to-gel transition triggered by loading of laponite, reflecting a cross-linkage effect of cellulose/laponite hybrids. Similarly, based on scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and X-ray diffraction (XRD) characterizations, as well as mechanical and thermal measurements, the cross-linkage effect of cellulose/laponite hybrids was also found in solid films, which played an important role in improving the tensile strength (σb) of composite films. For instance, the σb exhibited a largest enhancement up to 75.7% at a critical laponite content of 0.100 wt%, indicating that the property of composite film was closely related with the dispersion and interaction state of laponite, i.e. its content in cellulose matrix. These results were expected to provide significant information for fabrication and utility of cellulose-based materials.

  10. Influence of preparation conditions on the dispersion parameters of sprayed iron oxide thin films

    Science.gov (United States)

    Akl, Alaa A.

    2010-10-01

    Iron oxide thin films were prepared by spray pyrolysis technique (SPT) at various substrate temperatures ( Tsub) and different deposition time. X-ray diffraction (XRD) analysis showed that, at Tsub ≥ 350 °C, a single phase of α-Fe 2O 3 film is formed which has the rhombohedral structure. Moreover, the crystallinity was improved by increasing Tsub. The effect of Tsub as well as deposition time on the optical dispersion of these films has been investigated. The optical transmittance and reflectance measurements were performed by using spectrophotometer in the wavelength range from 300 to 2500 nm. The refractive index was determined by using Murmann's exact equation. It was observed that, the refractive index increased with increasing in both the Tsub and film thickness. The optical dispersion parameters have been evaluated and analyzed by using Wemple-Didomenico equation. The obtained results showed that, the dielectric properties have weak dependencies of growth temperature and film thickness. At Tsub ≥ 350 °C, the average values of oscillator energy, Eo and dispersion energy, Ed were found to be 5.96 and 34.08 eV. While at different thickness, the average values of dispersion energies were found to be 3.93 and 17.08 eV. Also, the average values of oscillator strength So and single resonant frequency ωo were estimated 10.78 × 10 13 m -2 and 5.99 × 10 15 Hz, while at different thickness were evaluating 4.81 × 10 13 m -2 and 6.11 × 10 15 Hz. Furthermore, the optical parameters such as wavelength of single oscillator λo, plasma frequency ωp, and dielectric constant ɛ have been evaluated. The carrier concentration Nopt by using Drud's theory was obtained the range of 5.07 × 10 25 m -3 to 1.04 × 10 26 m -3.

  11. Gyrotactic swimmer dispersion in pipe flow: experimental challenge of competing models

    CERN Document Server

    Croze, O A; Bees, M A

    2016-01-01

    Suspensions of microswimmers are a rich source of fascinating new fluid mechanics. Recently we predicted the nonclassical pipe flow dispersion of gyrotactic microalgae, whose orientation is biased by gravity and flow shear. Analytical theory predicts that these active swimmers disperse in a markedly distinct manner from passive tracers (Taylor dispersion). Dispersing swimmers display nonzero drift and effective diffusivity that is non-monotonic with Peclet number. Such predictions agree with numerical simulations, but hitherto have not been tested experimentally. Here, we extend the theory to realistically describe suspensions of negatively buoyant bi-flagellate algae and obtain new predictions for the model species Dunaliella salina, parametrised using tracking video microscopy. We then present a new experimental method to measure gyrotactic dispersion using fluorescently stained D. salina and provide a preliminary comparison with predictions of a nonzero drift above the mean flow. Finally, we propose furthe...

  12. Flush-mounted hot film anemometer accuracy in pulsatile flow.

    Science.gov (United States)

    Nandy, S; Tarbell, J M

    1986-08-01

    The accuracy of a flush-mounted hot film anemometer probe for wall shear stress measurements in physiological pulsatile flows was evaluated in fully developed pulsatile flow in a rigid straight tube. Measured wall shear stress waveform based on steady flow anemometer probe calibrations were compared to theoretical wall shear stress waveforms based on well-established theory and measured flow rate waveforms. The measured and theoretical waveforms were in close agreement during systole (average deviation of 14 percent at peak systole). As expected, agreement was poor during diastole because of flow reversal and diminished frequency response at low shear rate.

  13. Yielding and flow of cellulose microfibril dispersions in the presence of a charged polymer

    NARCIS (Netherlands)

    Kort, De Daan W.; Veen, Sandra J.; As, Van Henk; Bonn, Daniel; Velikov, Krassimir P.; Duynhoven, Van John P.M.

    2016-01-01

    The shear flow of microfibrillated cellulose dispersions is still not wholly understood as a consequence of their multi-length-scale heterogeneity. We added carboxymethyl cellulose, a charged polymer, that makes cellulose microfibril dispersions more homogeneous at the submicron and macro scales.

  14. Dispersed plug flow model for upflow anaerobic sludge bed reactors with focus on granular sludge dynamics

    NARCIS (Netherlands)

    Kalyuzhnyi, S.V.; Fedorovich, V.V.; Lens, P.N.L.

    2006-01-01

    A new approach to model upflow anaerobic sludge bed (UASB)-reactors, referred to as a one-dimensional dispersed plug flow model, was developed. This model focusses on the granular sludge dynamics along the reactor height, based on the balance between dispersion, sedimentation and convection using on

  15. Anomalous dispersion of Lagrangian particles in local regions of turbulent flows revealed by convex hull analysis

    CERN Document Server

    Pratt, J; Mueller, W -C; Chapman, S C; Watkins, N W

    2014-01-01

    Local regions of anomalous particle dispersion, and intermittent events that occur in turbulent flows can greatly influence the global statistical description of the flow. These local behaviors can be identified and analyzed by comparing the growth of neighboring convex hulls of Lagrangian tracer particles. Although in our simulations of homogeneous turbulence the convex hulls generally grow in size, after the Lagrangian particles that define the convex hulls begin to disperse, our analysis reveals short periods when the convex hulls of the Lagrangian particles shrink, evidence that particles are not dispersing simply. Shrinkage can be associated with anisotropic flows, since it occurs most frequently in the presence of a mean magnetic field or thermal convection. We compare dispersion between a wide range of statistically homogeneous and stationary turbulent flows ranging from homogeneous isotropic Navier-Stokes turbulence over different configurations of magnetohydrodynamic turbulence and Boussinesq convect...

  16. Patterns, Instabilities, Colors, and Flows in Vertical Foam Films

    Science.gov (United States)

    Yilixiati, Subinuer; Wojcik, Ewelina; Zhang, Yiran; Pearsall, Collin; Sharma, Vivek

    2015-03-01

    Foams find use in many applications in daily life, industry and biology. Examples include beverages, firefighting foam, cosmetics, foams for oil recovery and foams formed by pollutants. Foams are collection of bubbles separated by thin liquid films that are stabilized against drainage by the presence of surfactant molecules. Drainage kinetics and stability of the foam are strongly influenced by surfactant type, addition of particles, proteins and polymers. In this study, we utilize the thin film interference colors as markers for identifying patterns, instabilities and flows within vertical foam films. We experimentally study the emergence of thickness fluctuations near the borders and within thinning films, and study how buoyancy, capillarity and gravity driven instabilities and flows, are affected by variation in bulk and interfacial physicochemical properties dependent on the choice of constituents.

  17. Influence of Physical and Chemical Modification on the Optical Rotatory Dispersion and Biological Activity of Chitosan Films

    Directory of Open Access Journals (Sweden)

    A. B. Shipovskaya

    2013-01-01

    Full Text Available The optical and bactericidal properties of acetic and basic chitosan films were studied. By the ORD technique, we found that these films differed in the values of their specific optical rotation and of their rotary and dispersive constants. A sign inversion of was observed when the acetic chitosan films were heat-treated. The bactericidal activity of the initial and dehydrated acetic films was analyzed, and their moisture content and optical and biological activities were compared.

  18. Relationship between first-order decay coefficients in ponds, for plug flow, CSTR and dispersed flow regimes.

    Science.gov (United States)

    von, Sperling M

    2002-01-01

    Adequate consideration of the hydraulic regime of a pond is essential in the analysis of BOD and coliform removal, and considerable divergence exists in the literature when reporting removal coefficients. This paper aims at integrating the existing approaches, by quantifying the relationship between the first-order removal coefficients K from the three main hydraulic regimes (CSTR, plug flow and dispersed flow) adopted in the design and performance evaluation of ponds. Based on theoretical considerations and statistical regression analyses, the relationship between the K values is investigated, quantified and modelled. Two tables are presented and two equations are proposed, which allow conversion of K values obtained for dispersed flow to (a) K for CSTR and (b) K for plug flow, based on the hydraulic detention time t and the dispersion number d. These coefficients, when applied in the CSTR or plug-flow equations, will give approximately the same prediction of the effluent concentration as that obtained when using the dispersed-flow model with its proper coefficient. With this approach designers can apply, and researchers can report, K values for the two idealised flow patterns (CSTR and plug flow).

  19. Characterization of a hot-film probe for hypersonic flow

    Science.gov (United States)

    Sheplak, M.; Spina, E.; Mcginley, C.

    1995-01-01

    The critical issues concerning the application of constant-temperature hot-film anemometry to hypersonic flow are reviewed and extended. Mass-flux static calibrations were conducted in a Mach 10 helium flow, while mass-flux and total-temperature static calibrations were made in a Mach 6 air flow. In addition, comparative hot-film/hot-wire turbulence measurements were made in a Mach 11 helium boundary layer to provide insight into the dynamic response of the hot film. The measurements indicate that substrate conduction 'losses' dominate the static response of the hot-film probe, thus resulting in poor sensitivity to mass-flux and total temperature. Furthermore, it has been found that it is not possible to isolate mass-flux fluctuations at high overheat ratios for the current hot-film design. Thus, the sapphire-substrate hot-film anemometer is a robust, high-bandwidth instrument limited to qualitative transition and turbulence measurements. Finally, the extension of this technique to providing quantitative information is dependent upon the development of lower thermal-conductivity substrate materials.

  20. Flow Visualization and Pattern Formation in Vertically Falling Liquid Films

    Science.gov (United States)

    Balakotaiah, Vemuri; Malamataris, Nikolaos

    2008-11-01

    Analytical results of a low-dimensional two equation h-q model and results of a direct numerical simulation of the transient two-dimensional Navier Stokes equations are presented for vertically falling liquid films along a solid wall. The numerical study aims at the elucidation of the hydrodynamics of the falling film. The analytical study aims at the calculation of the parameter space where pattern formation occurs for this flow. It has been found that when the wave amplitude exceeds a certain magnitude, flow reversal occurs in the film underneath the minimum of the waves [1]. The instantaneous vortical structures possess two hyperbolic points on the vertical wall and an elliptic point in the film. As the wave amplitude increases further, the elliptic point reaches the free surface of the film and two more hyperbolic points are formed in the free surface that replace the elliptic point. Between the two hyperbolic points on the free surface, the streamwise component of velocity is negative and the film is divided into asymmetric patterns of up and down flows. Depending on the value of the Kapitza number, these patterns are either stationary or oscillatory. Physical reasons for the influence of the Kapitza number on pattern formation are given. Movies are shown where the pattern formation is demonstrated. [1] N.A.Malamataris and V.Balakotaiah (2008), AIChE J., 54(7), p. 1725-1740

  1. Observation of Self-Cavitating Envelope Dispersive Shock Waves in Yttrium Iron Garnet Thin Films.

    Science.gov (United States)

    Janantha, P A Praveen; Sprenger, Patrick; Hoefer, Mark A; Wu, Mingzhong

    2017-07-14

    The formation and properties of envelope dispersive shock wave (DSW) excitations from repulsive nonlinear waves in a magnetic film are studied. Experiments involve the excitation of a spin wave step pulse in a low-loss magnetic Y_{3}Fe_{5}O_{12} thin film strip, in which the spin wave amplitude increases rapidly, realizing the canonical Riemann problem of shock theory. Under certain conditions, the envelope of the spin wave pulse evolves into a DSW that consists of an expanding train of nonlinear oscillations with amplitudes increasing from front to back, terminated by a black soliton. The onset of DSW self-cavitation, indicated by a point of zero power and a concomitant 180° phase jump, is observed for sufficiently large steps, indicative of the bidirectional dispersive hydrodynamic nature of the DSW. The experimental observations are interpreted with theory and simulations of the nonlinear Schrödinger equation.

  2. Fast drying and film formation of latex dispersions studied with FTIR spectroscopic imaging.

    Science.gov (United States)

    Kimber, James A; Gerst, Matthias; Kazarian, Sergei G

    2014-11-18

    Drying of thin latex films (∼20 μm) at high drying speeds (of the order of seconds) has been studied by fast chemical imaging. ATR-FTIR spectroscopic imaging combined with a fast "kinetic" mode was used to acquire spectral images without coaddition, enabling the amount of water and homogeneity of the drying film to be studied over time. Drying profiles, constructed from analyzing the water content in each image, show two stages of drying, a fast and a slow region. The formulation of latex dispersions affects the onset of slow drying and the volume fraction of water remaining at the onset of slow drying. In this work, the effect of physical properties, film thickness and glass transition temperature (Tg), were investigated, as well as the effect of monomer composition where two monomoers, 2-ethylhexyl acrylate and n-butyl acrylate, and the amount of hydrophilic comonomer, methyl methacrylate (MMA), were varied. It was found that thicker films produced slower overall drying and that the formulation with a Tg above the minimum film formation temperature did not dry evenly, exhibiting cracking. However, the drying kinetics of high and low Tg films were similar, highlighting the advantage of using a spatially-resolved spectroscopic approach. Formulations containing more MMA dried faster than those with less. This was due to the hydrophilicity of MMA and the increase in Tg of the dispersion from the addition of MMA. Overall, FTIR spectroscopic imaging was shown to be a suitable approach in measuring film drying at high speeds as both chemical changes and chemical distribution could be analyzed over time.

  3. A Fundamental Approach to the Simulation of Flow and Dispersion in Fractured Media

    Energy Technology Data Exchange (ETDEWEB)

    Miller, J.D.

    1983-12-15

    Fracture systems may be generalized in terms of number and orientation of sets of parallel fractures and the distribution of length, width, thickness and separation. Borehole measurements may be used to particularize these parameters for a specific site. Global flow and dispersion in an aquifer occur in the interconnected fractures and may be related to specific fracture elements. A fluid dynamics code named SALE has been used to solve the Navier-Stokes equations for laminar flow in these elemental geometries. A marker particle calculation has been added to characterize longitudinal dispersion due to the velocity profile across the fracture and lateral dispersion due to flow disturbances at junctions. Local flow and dispersion in the matrix occur in the finer fracture structure and are evaluated using porous media approaches. These results or models are integrated in a 2D isothermal reservoir simulator named FRACSL. Discrete fractures are superimposed on the edges or diagnoals of rectangular grid elements. Water may flow from node to node through the matrix or through the fracture. The heads are found by iterating for the distribution which conserves the appropriate local mass. Marker particles are used to monitor the tracer dispersion due to motion in the fractures, in the matrix and between the two. Results are given showing flow and dispersion in an orthogonal junction and in a sample fractured reservoir.

  4. Quantification of myocardial blood flow and blood flow reserve in the presence of arterial dispersion: a simulation study.

    Science.gov (United States)

    Schmitt, Melanie; Viallon, Magalie; Thelen, Manfred; Schreiber, Wolfgang G

    2002-04-01

    Myocardial blood flow (MBF) can be quantified using dynamic T1-weighted MRI of diffusible tracers and a mathematical model of underlying vasculature. Quantification of MBF by means of T1- weighted MRI requires knowledge of the arterial input function (AIF). The AIF can be estimated from the left ventricular (LV) cavity. However, dispersion may occur between the LV and the tissue of interest because of the laminar blood flow profiles, branching of venules, and because of stenosis. To evaluate the influence of dispersion on the results of MBF quantification, a simulation study was performed. The dispersion was described as a convolution of the AIF with an exponential residue function. Synthetic tissue and AIF curves were analyzed and the derived parameters fit to the simulated parameters. The results show that an unaccounted dispersion may result in a systematic underestimation of MBF up to approximately 50%. Underestimation increases with increasing dispersion and with increasing MBF. Assuming equal dispersion at rest and during hyperemia, myocardial perfusion reserve (MPR) estimates are also susceptible to underestimation of approximately 20%. An unaccounted dispersion therefore can lead to systematic underestimation of both blood flow and perfusion reserve.

  5. Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing.

    Science.gov (United States)

    Zhang, Meimei; Li, Houli; Lang, Bo; O'Donnell, Kevin; Zhang, Haohao; Wang, Zhouhua; Dong, Yixuan; Wu, Chuanbin; Williams, Robert O

    2012-11-01

    The objective of this study was to prepare amorphous fenofibrate (FB) solid dispersions using thin film freezing (TFF) and to incorporate the solid dispersions into pharmaceutically acceptable dosage forms. FB solid dispersions prepared with optimized drug/polymer ratios were characterized by modulated differential scanning calorimetry (MDSC), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area measurements, Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), and supersaturation dissolution testing. Furthermore, a dry granulation technique was used to encapsulate the TFF compositions for in vitro dissolution and in vivo animal pharmacokinetic studies. The results showed that the TFF process produced amorphous, porous, microstructured, and stable solid dispersions with high surface areas. Development of solid oral dosage forms revealed that the performance of the FB containing solid dispersions was not affected by the formulation process, which was confirmed by DSC and XRD. Moreover, an in vivo pharmacokinetic study in rats revealed a significant increase in FB absorption compared to bulk FB. We confirmed that amorphous solid dispersions with large surface areas produced by the TFF process displayed superior dissolution rates and corresponding enhanced bioavailability of the poorly water-soluble drug, FB. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. An accurate model for the thin film flow

    Institute of Scientific and Technical Information of China (English)

    Hamid Ait Abderahmane; Georgios H. Vatistas

    2008-01-01

    This paper deals with the linear stability of a liquid film flowing down an inclined plane. The Navier-Stokes equations were reduced into four evolution equations that describe the development of the film depth, the flow rate, the free surface velocity, and the wall shear stress, using the Karman-Polhausen boundary layer integral method. Thus, we were able to determine the stability threshold and approach well the critical wave number for long waves. The obtained results were found to be in good agreement with the experiments of Liu et al.

  7. Interfacial properties, thin film stability and foam stability of casein micelle dispersions.

    Science.gov (United States)

    Chen, Min; Sala, Guido; Meinders, Marcel B J; van Valenberg, Hein J F; van der Linden, Erik; Sagis, Leonard M C

    2017-01-01

    Foam stability of casein micelle dispersions (CMDs) strongly depends on aggregate size. To elucidate the underlying mechanism, the role of interfacial and thin film properties was investigated. CMDs were prepared at 4°C and 20°C, designated as CMD4°C and CMD20°C. At equal protein concentrations, foam stability of CMD4°C (with casein micelle aggregates) was markedly higher than CMD20°C (without aggregates). Although the elastic modulus of CMD4°C was twice as that of CMD20°C at 0.005Hz, the protein adsorbed amount was slightly higher for CMD20°C than for CMD4°C, which indicated a slight difference in interfacial composition of the air/water interface. Non-linear surface dilatational rheology showed minor differences between mechanical properties of air/water interfaces stabilized by two CMDs. These differences in interfacial properties could not explain the large difference in foam stability between two CMDs. Thin film analysis showed that films made with CMD20°C drained to a more homogeneous film compared to films stabilized by CMD4°C. Large casein micelle aggregates trapped in the thin film of CMD4°C made the film more heterogeneous. The rupture time of thin films was significantly longer for CMD4°C (>1h) than for CMD20°C (foam stability decreased significantly. In conclusion, the increased stability of foam prepared with CMD4°C appears to be the result of entrapment of casein micelle aggregates in the liquid films of the foam.

  8. Fabrication and evaluation of dispersed-Ag nanoparticles-in-polyimide thin films

    Science.gov (United States)

    Sonehara, Makoto; Watanabe, Yuki; Yamaguchi, Sota; Kato, Takanori; Yoshisaku, Yasuaki; Sato, Toshiro; Itoh, Eiji

    2017-10-01

    A thin-film common-mode filter (TF-CMF) for cell phones in the UHF band was fabricated and evaluated. The TF-CMF consisted of multiple metal–insulator–metal (MIM) capacitors and inductors. The sizes of the 0.70–1.0 GHz band-type and 1.8–2.0 GHz band-type TF-CMFs are 1,140 × 1,260 × 10.5 µm3, and 1,060 × 1,060 × 10.5 µm3, respectively. The footprint in both types of TF-CMFs is over 1 mm2. In order to miniaturize the TF-CMF, we proposed to change a polyimide-only to a polyimide with dispersed Ag nanoparticles with high permittivity in the insulator layer for the MIM capacitor of the TF-CMF. A polyimide (\\text{polyimide precursor}:\\text{toluene with dispersed Ag nanoparticles} = 100:1) thin film with dispersed high-density Ag nanoparticles has a relative permittivity of about 8, which is twice as high as that of the polyimide-only thin film. If the capacitance and distance between electrodes are the same, then the capacitor footprint may be halved.

  9. Dispersion model for optical thin films applicable in wide spectral range

    Science.gov (United States)

    Franta, Daniel; Nečas, David; Ohlídal, Ivan; Giglia, Angelo

    2015-09-01

    In the optics industry thin film systems are used to construct various interference devices such as antireflective coatings, high-reflectance mirrors, beam splitters and filters. The optical characterization of complex optical systems can not be performed by measurements only in the short spectral range in which the interference devices will be employed because the measured data do not contain sufficient information about all relevant parameters of these systems. The characterization of film materials requires the extension of the spectral range of the measurements to the IR region containing phonon absorption and to the UV region containing the electronic excitations. However, this leads to necessity of a dispersion model suitable for the description of the dielectric response in the wide spectral range. Such model must respect the physical conditions following from theory of dispersion, particularly Kramers-Kronig relations and integrability imposed by sum rules. This work presents the construction of a universal dispersion model composed from individual contributions representing both electronic and phonon excitations. The efficiency of presented model is given by the fact that all the contributions are described by analytical expressions. It is shown that the model is suitable for precise modeling of spectral dependencies of optical constants of a broad class of materials used in the optical industry for thin film systems such as MgF2, SiO2, Al2O3, HfO2, Ta2O5 and TiO2 in the spectral range from far IR to vacuum UV.

  10. Rapid photokilling of gram-negative Escherichia coli bacteria by platinum dispersed titania nanocomposite films

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Bonamali, E-mail: bpal@thapar.edu [School of Chemistry and Biochemistry, Thapar University, Patiala 147004 (India); Singh, Isha; Angrish, Kunal; Aminedi, Raghavendra; Das, Niranjan [Department of Biotechnology and Environmental Sciences, Thapar University, Patiala 147004 (India)

    2012-09-14

    Superior antimicrobial activity of 2 wt.% Pt-dispersed TiO{sub 2} thin film was observed in photokilling Gram-negative Escherichia coli bacteria within 5 min irradiation (640 {mu}W cm{sup -2}, {lambda} > 340 nm) from UV torch than bare TiO{sub 2} film. Severe disruption of cell membrane has occurred over illuminated Pt-TiO{sub 2} catalysts films coated with 100-300 {mu}g powders per 5 cm{sup 2} areas over sterilized glass slides. The Pt dispersion onto TiO{sub 2} by impregnation-hydrogen reduction always exhibited better photokilling effect than Pt photodeposition, irrespective of Pt-TiO{sub 2} dose and light exposure time. Similar trend in photoactivity difference between two Pt-TiO{sub 2} catalysts is also observed in aqueous slurry because of the unlike surface structure of TiO{sub 2} due to different annealing temperatures, size and nature of Pt particles dispersion onto TiO{sub 2} photocatalysts. -- Graphical abstract: Platinization of TiO{sub 2} by impregnation-hydrogen reduction method exhibited drastic photoetching and killing of E. coli bacteria over UV-irradiated catalysts films in comparison to Pt photodeposition. Highlights: Black-Right-Pointing-Pointer Remarkable antimicrobial activity of photorradiated Pt-TiO{sub 2} coated thin film. Black-Right-Pointing-Pointer Pt impregnation-exhibits superior photoactivity than Pt photodeposition onto TiO{sub 2}. Black-Right-Pointing-Pointer Photokilling of E. coli cells occur within 10 min of UV (640 {mu}W cm{sup -2}) irradiation. Black-Right-Pointing-Pointer Size and nature of Pt deposition control the bactericidal effect of TiO{sub 2} catalyst. Black-Right-Pointing-Pointer Photodissolution of bacterial surface is occurred on prolong UV light exposure.

  11. Field studies of transport and dispersion of atmospheric tracers in nocturnal drainage flows

    Energy Technology Data Exchange (ETDEWEB)

    Gudiksen, P.H.; Ferber, G.J.; Fowler, M.M.; Eberhard, W.L.; Fosberg, M.A.; Knuth, W.R.

    1984-01-01

    A series of tracer experiments were carried out as part of the Atmospheric Studies in Complex Terrain (ASCOT) program to evaluate pollutant transport and dispersion characteristics of nocturnal drainage flows within a valley in northern California. The results indicate that the degree of interaction of the drainage flows with the larger scale regional flows are strongly dependent on how well the shallow drainage flows are shielded by the surrounding topography from the external environment. For the valley under study, the drainage flows from about mid-slope elevations and below were generally decoupled from the externally generated flows; as evidenced by the similarity of the surface tracer distribution produced during widely varying regional flow conditions. However, tracers released immediately above the drainage flows near the ridge top did reveal considerable mixing between the transition layer flows and the underlying surface drainage flows. Likewise, the transport and dispersion of the tracers at elevated heights within the valley basin were extremely dependent on the influences of the regional scale flows on the valley circulation. The dispersion rates associated with the transition layer flows were dependent on topographic constraints but were appreciably higher than those reported for homogeneous flat terrain situations.

  12. Convective dispersion during steady flow in the conducting airways of the human lung.

    Science.gov (United States)

    Fresconi, Frank E; Prasad, Ajay K

    2008-02-01

    The adverse health effects of inhaled particulate matter from the environment depend on its dispersion, transport, and deposition in the human airways. Similarly, precise targeting of deposition sites by pulmonary drug delivery systems also relies on characterizing the dispersion and transport of therapeutic aerosols in the respiratory tract. A variety of mechanisms may contribute to convective dispersion in the lung; simple axial streaming, augmented dispersion, and steady streaming are investigated in this effort. Flow visualization of a bolus during inhalation and exhalation, and dispersion measurements were conducted during steady flow in a three-generational, anatomically accurate in vitro model of the conducting airways to support this goal. Control variables included Reynolds number, flow direction, generation, and branch. Experiments illustrate transport patterns in the lumen cross section and map their relation to dispersion metrics. These results indicate that simple axial streaming, rather than augmented dispersion, is the dominant steady convective dispersion mechanism in symmetric Weibel generations 7-13 during normal respiration. Experimental evidence supports the branching nature of the airways as a possible contributor to steady streaming in the lung.

  13. Characterizing dispersivity and stagnation in porous media using NMR flow propagators

    Science.gov (United States)

    Singer, P. M.; Mitchell, J.; Fordham, E. J.

    2016-09-01

    Low-field nuclear magnetic resonance (NMR) displacement probability distributions (flow propagators) are presented for water flowing through heterogeneous porous materials. Four sedimentary rocks have been chosen as example systems: Dolostone, Bentheimer sandstone, Berea sandstone, and Indiana limestone (in order of decreasing permeability). The fluid displacement is characterized by pre-asymptotic Stokes' flow and so the probability distributions are bimodal, with peaks corresponding to stagnant fluid in dead-end pores and flowing fluid in the connected porosity. Cut-off Gaussian functions are used to fit the flowing and stagnant peaks independently. An effective dispersivity length scale Lv (also known as the mixing length scale) is estimated by fitting the portion of the probability distribution corresponding to the flowing fluid. For the relatively homogeneous Bentheimer sandstone, the ratio of effective dispersivity length scale to effective transport diameter dt is Lv /dt ≈ 16 , which is an order of magnitude larger than for randomly packed glass beads where Lv /dt ≈ 1.8 . We compare these dispersivity parameters to similar values extracted from a cumulant analysis of the entire propagator. Fitting a cut-off Gaussian avoids the usual complications of analyzing dispersion in the presence of the ubiquitous stagnant fluid, and results in a clear demonstration of the influence of long-range heterogeneities on the dispersivity for flow in real sedimentary rocks.

  14. Characterizing dispersivity and stagnation in porous media using NMR flow propagators.

    Science.gov (United States)

    Singer, P M; Mitchell, J; Fordham, E J

    2016-09-01

    Low-field nuclear magnetic resonance (NMR) displacement probability distributions (flow propagators) are presented for water flowing through heterogeneous porous materials. Four sedimentary rocks have been chosen as example systems: Dolostone, Bentheimer sandstone, Berea sandstone, and Indiana limestone (in order of decreasing permeability). The fluid displacement is characterized by pre-asymptotic Stokes' flow and so the probability distributions are bimodal, with peaks corresponding to stagnant fluid in dead-end pores and flowing fluid in the connected porosity. Cut-off Gaussian functions are used to fit the flowing and stagnant peaks independently. An effective dispersivity length scale Lv (also known as the mixing length scale) is estimated by fitting the portion of the probability distribution corresponding to the flowing fluid. For the relatively homogeneous Bentheimer sandstone, the ratio of effective dispersivity length scale to effective transport diameter dt is Lv/dt≈16, which is an order of magnitude larger than for randomly packed glass beads where Lv/dt≈1.8. We compare these dispersivity parameters to similar values extracted from a cumulant analysis of the entire propagator. Fitting a cut-off Gaussian avoids the usual complications of analyzing dispersion in the presence of the ubiquitous stagnant fluid, and results in a clear demonstration of the influence of long-range heterogeneities on the dispersivity for flow in real sedimentary rocks.

  15. Dispersion of a nanoliter bolus in microfluidic co-flow

    Science.gov (United States)

    Conway, A. J.; Saadi, W. M.; Sinatra, F. L.; Kowalski, G.; Larson, D.; Fiering, J.

    2014-03-01

    Microfluidic systems enable reactions and assays on the scale of nanoliters. However, at this scale non-uniformities in sample delivery become significant. To determine the fundamental minimum sample volume required for a particular device, a detailed understanding of mass transport is required. Co-flowing laminar streams are widely used in many devices, but typically only in the steady-state. Because establishing the co-flow steady-state consumes excess sample volume and time, there is a benefit to operating devices in the transient state, which predominates as the volume of the co-flow reactor decreases. Analysis of the co-flow transient has been neglected thus far. In this work we describe the fabrication of a pneumatically controlled microfluidic injector constructed to inject a discrete 50 nL bolus into one side of a two-stream co-flow reactor. Using dye for image analysis, injections were performed at a range of flow rates from 0.5-10 µL min-1, and for comparison we collected the co-flow steady-state data for this range. The results of the image analysis were also compared against theory and simulations for device validation. For evaluation, we established a metric that indicates how well the mass distribution in the bolus injection approximates steady-state co-flow. Using such analysis, transient-state injections can approximate steady-state conditions within pre-defined errors, allowing straightforward measurements to be performed with reduced reagent consumption.

  16. Dispersal

    Science.gov (United States)

    Clobert, J.; Danchin, E.; Dhondt, A.A.; Nichols, J.D.

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  17. Dispersion-model-free determination of optical constants: application to materials for organic thin film devices.

    Science.gov (United States)

    Flämmich, Michael; Danz, Norbert; Michaelis, Dirk; Bräuer, Andreas; Gather, Malte C; Kremer, Jonas H-W M; Meerholz, Klaus

    2009-03-10

    We describe a method to determine the refractive index and extinction coefficient of thin film materials without prior knowledge of the film thickness and without the assumption of a dispersion model. A straightforward back calculation to the optical parameters can be performed starting from simple measurements of reflection and transmission spectra of a 100-250 nm thick supported film. The exact film thickness is found simultaneously by fulfilling the intrinsic demand of continuity of the refractive index as a function of wavelength. If both the layer and the substrate are homogeneous and isotropic media with plane and parallel interfaces, effects like surface roughness, scattering, or thickness inhomogeneities can be neglected. Then, the accuracy of the measurement is approximately 10(-2) and 10(-3) for the refractive index and the extinction coefficient, respectively. The error of the thin film thickness determination is well below 1 nm. Thus this technique is well suited to determine the input parameters for optical simulations of organic thin film devices, such as organic light-emitting diodes (OLEDs) or organic photovoltaic (OPV) cells. We apply the method to the electroluminescent polymer poly(2,5-dioctyl-p-phenylene vinylene) (PDO-PPV) and show its applicability by comparing the measured and calculated reflection and transmission spectra of OLED stacks with up to five layers.

  18. DVI Film Flow Instability Based on the Normal Mode Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jae Young; Euh, Dong Jin [Handong Global Univ., Pohang (Korea, Republic of)

    2013-10-15

    In the present paper, as the first step of nonlinear studies, the appearance of the third order spatial differentiation of the film thickness in the wave propagation equation is to be derived. The two-fluid model in the adiabatic condition is employed and normal mode analysis. Interfacial pressure forces between steam and water need to be modeled for this purpose. n the present study, we developed a theoretical basis to study nonlinear wave phenomena on the DVI film flow which highly affect the DVI penetration and liquid droplets entrainment out. We set the hyperbolicity breaking condition by providing the interfacial pressure difference considering the curvature of the reactor vessel. The interfacial pressure difference could generate nonlinear wave such as the horseshoe wave which has been believed as a main source of film break up to produce huge amount of droplets to be entrained out. As a safety injection method, the direct vessel injection has been intensively developed in Korea and employed in the APR1400. The developing efforts were made from the determination of the number, location and size of DVI nozzles to the experimental demonstrations. Experimental facilities with various scales have shown its complicated phenomena due to highly nonlinear interaction between the steam and injected water flow. The injected DVI water forms a film type flow but very unstable due to the unsteady energetic steam flow which find the exits around the shell of the downcomer of the reactor vessel. This steam and liquid film interaction leads to the instability on the surface of the film flow and the waves are highly nonlinear to form undercutting, roll over, and finally droplet releasing. The entrained droplets causes a difficulty in the analysis to estimate the water penetrated into the reactor core to cool the nuclear fuels heated up. Unfortunately, these instabilities on the interface of the DVI liquid film have not been studied appropriately and the conservative

  19. Flow and dispersion in anisotropic porous media: a Lattice-Boltzmann study

    CERN Document Server

    Maggiolo, Dario; Guarnieri, Massimo

    2016-01-01

    Given their capability of spreading active chemical species and collecting electricity, porous media made of carbon fibers are extensively used as diffusion layers in energy storage systems, such as redox flow batteries. In spite of this, the dispersion dynamics of species inside porous media is still not well understood and often lends itself to different interpretations. Actually, the microscopic design of efficient porous media which can potentially and effectively improve the performances of flow batteries, is a still open challenge. The present study aims to investigate the effect of fibrous media micro-structure on dispersion, in particular the effect of fiber orientation on drag and dispersion dynamics. Several Lattice-Boltzmann simulations of {flows through} differently-oriented fibrous media coupled with Lagrangian simulations of particle tracers have been performed. Results show that orienting fibers preferentially along the streamwise direction minimizes the drag and maximizes the dispersion, which...

  20. Yielding and flow of cellulose microfibril dispersions in the presence of a charged polymer.

    Science.gov (United States)

    de Kort, Daan W; Veen, Sandra J; Van As, Henk; Bonn, Daniel; Velikov, Krassimir P; van Duynhoven, John P M

    2016-05-25

    The shear flow of microfibrillated cellulose dispersions is still not wholly understood as a consequence of their multi-length-scale heterogeneity. We added carboxymethyl cellulose, a charged polymer, that makes cellulose microfibril dispersions more homogeneous at the submicron and macro scales. We then compared the yielding and flow behavior of these dispersions to that of typical thixotropic yield-stress fluids. Despite the apparent homogeneity of the dispersions, their flow velocity profiles in cone-plate geometry, as measured by rheo-MRI velocimetry, differ strongly from those observed for typical thixotropic model systems: the viscosity across the gap is not uniform, despite a flat stress field across the gap. We describe these velocity profiles with a nonlocal model, and attribute the non-locality to persistent micron-scale structural heterogeneity.

  1. Multiphysics Simulations of Entrained Flow Gasification. Part I: Validating the Nonreacting Flow Solver and the Particle Turbulent Dispersion Model

    KAUST Repository

    Kumar, Mayank

    2012-01-19

    In this two-part paper, we describe the construction, validation, and application of a multiscale model of entrained flow gasification. The accuracy of the model is demonstrated by (1) rigorously constructing and validating the key constituent submodels against relevant canonical test cases from the literature and (2) validating the integrated model against experimental data from laboratory scale and commercial scale gasifiers. In part I, the flow solver and particle turbulent dispersion models are validated against experimental data from nonswirling flow and swirling flow test cases in an axisymmetric sudden expansion geometry and a two-phase flow test case in a cylindrical bluff body geometry. Results show that while the large eddy simulation (LES) performs best among all tested models in predicting both swirling and nonswirling flows, the shear stress transport (SST) k-ω model is the best choice among the commonly used Reynolds-averaged Navier-Stokes (RANS) models. The particle turbulent dispersion model is accurate enough in predicting particle trajectories in complex turbulent flows when the underlying turbulent flow is well predicted. Moreover, a commonly used modeling constant in the particle dispersion model is optimized on the basis of comparisons with particle-phase experimental data for the two-phase flow bluff body case. © 2011 American Chemical Society.

  2. Refractive indices of polymer-dispersed liquid-crystal film materials: Epoxy-based systems

    Science.gov (United States)

    Vaz, Nuno A.; Montgomery, G. Paul, Jr.

    1987-10-01

    Polymer-dispersed liquid crystal (PDLC) films are potentially useful in applications requiring electrically controllable light transmission. In these applications, both a high on-state transmittance and a strong off-state attenuation are often needed over a wide operating temperature range. These transmittance characteristics depend strongly on the refractive indices of the materials in the PDLC films. We have measured the temperature dependent refractive indices of typical PDLC film materials and the temperature dependent electro-optic transmittance of a PDLC film composed of liquid crystal microdroplets dispersed in an epoxy matrix. We show that our refractive index measurements can account for all the features in the measured transmittance characteristics and discuss several methods for controlling refractive indices to optimize electro-optic transmittance over an extended temperature range. We have also measured the room temperature refractive indices of mixtures of epoxy resins and hardeners as a function of composition. We discuss the problems associated with predicting the refractive indices of such mixtures in terms of either the volume fractions or mole fractions of the mixture components. These considerations are important in matching refractive indices of droplets and matrix materials to maximize on-state transmittance. The refractive indices of epoxy matrix materials increase monotonically with time during their chemical cure. The measured time dependence can be described by a simple model in which the concentrations of the reacting resin and hardener each decay exponentially in time with their own characteristic time constants while the concentration of the cured polymer increases. Finally, we relate the measured rates of index change with temperature to the coefficients of volume expansion of PDLC film materials; the results are used to discuss the mechanical stability of PDLC films.

  3. Modeling drop impacts on inclined flowing soap films

    Science.gov (United States)

    Basu, Saikat; Yawar, Ali; Concha, Andres; Bandi, Mahesh

    2015-11-01

    Small drops impinging on soap films flowing at an angle primarily exhibit three fundamental regimes of post-impact dynamics: (a) the drop bounces off the film surface, (b) it coalesces with the downstream flow, and (c) it pierces through the film. During impact, the drop deforms along with a simultaneous, almost elastic deformation of the film transverse to the stream direction. Hence, the governing dynamics for this interaction present the rare opportunity to explore the in-tandem effects of elasticity and hydrodynamics alike. In this talk, we outline the analytical framework to study the drop impact dynamics. The model assumes a deformable drop and a deformable three-dimensional soap film and invokes a parametric study to qualify the three mentioned impact types. The physical parameters include the impact angle, drop impact speed, and the diameters of the drop prior to and during impact when it deforms and spreads out. Our model system offers a path towards optimization of interactions between a spray and a flowing liquid.

  4. Droplets in annular-dispersed gas-liquid pipe-flows

    NARCIS (Netherlands)

    Van 't Westende, J.M.C.

    2008-01-01

    Annular-dispersed gas-liquid pipe-flows are commonly encountered in many industrial applications, and have already been studied for many decades. However, due to the great complexity of this type of flow, there are still many phenomena that are poorly understood. The aim of this thesis is to shed mo

  5. Numerical simulations of rarefied gas flows in thin film processes

    NARCIS (Netherlands)

    Dorsman, R.

    2007-01-01

    Many processes exist in which a thin film is deposited from the gas phase, e.g. Chemical Vapor Deposition (CVD). These processes are operated at ever decreasing reactor operating pressures and with ever decreasing wafer feature dimensions, reaching into the rarefied flow regime. As numerical

  6. Numerical simulations of rarefied gas flows in thin film processes

    NARCIS (Netherlands)

    Dorsman, R.

    2007-01-01

    Many processes exist in which a thin film is deposited from the gas phase, e.g. Chemical Vapor Deposition (CVD). These processes are operated at ever decreasing reactor operating pressures and with ever decreasing wafer feature dimensions, reaching into the rarefied flow regime. As numerical simulat

  7. Synthesis and investigation of PMMA films with homogeneously dispersed multiwalled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Pantoja-Castro, M.A., E-mail: m_pantojaq@yahoo.com.mx [Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Av. J. Múgica S/N Col., Villa Universidad, CP 58040 Morelia, Michoacán (Mexico); Pérez-Robles, J.F. [Centro de Investigación y de Estudios Avanzados del IPN, Unidad Querétaro, Libramiento Norponiente #2000, Fracc. Real de Juriquilla, CP 76230 Querétaro (Mexico); González-Rodríguez, H. [Facultad de Ingeniería Química, Universidad Michoacana de San Nicolás de Hidalgo, Av. J. Múgica S/N Col., Villa Universidad, CP 58040 Morelia, Michoacán (Mexico); Vorobiev-Vasilievitch, Y. [Centro de Investigación y de Estudios Avanzados del IPN, Unidad Querétaro, Libramiento Norponiente #2000, Fracc. Real de Juriquilla, CP 76230 Querétaro (Mexico); Martínez-Tejada, H.V. [Instituto de Energía, Materiales y Medio Ambiente, Universidad Pontificia Bolivariana, Circular 1 No. 70-01, Bloque 22, Medellín (Colombia); Velasco-Santos, C. [Centro de Física Aplicada y Tecnología Avanzada, Universidad Autónoma de México, Av. Boulevard Juriquilla, No. 3001 Juriquilla, CP 76230 Querétaro (Mexico)

    2013-07-15

    Multiwalled carbon nanotubes (MWNT) modified by 2.2′-azoiso-butyronitrile (AIBN) were incorporated into methyl methacrylate (MMA) by sonochemistry method, resulting in homogenous dispersion of MWNT, which makes possible to obtain flexible conductive polymer-matrix nanocomposites films of PMMA, with MWNT concentrations ranging from 0 to 0.5 wt%. Modified MWNT (AIBN-MWNT) were studied by Fourier transform infrared (FT-IR), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and through visual observations in order to compare the dispersion in 2-propanone and toluene with that of pristine MWNT. Synthesized PMMA-AIBN-MWNT films were studied by FT-IR and Raman spectroscopy. Using FT-IR for the AIBN-MWNT it was not possible to identify any group or groups attached to the nanotubes. Raman spectroscopy shows a small modification in the Lorentzian peaks ratio I{sub D/G} of AIBN-MWNT, meanwhile XPS showed that atomic compositions does not change for AIBN-MWNT compared to the pristine nanotubes. Also by impedance it was analyzed the conductivity of PMMA-MWNT films and the results showed a threshold percolation at 0.5 wt%. FT-IR and Raman analyses for PMMA-AIBN-MWNT composite indicate a covalent bonding between PMMA and MWNT due to the opening of π-bonds of the nanotubes, which is related with a possible proposed reaction scheme. - Graphical abstract: Display Omitted - Highlights: • We used sonochemistry-in situ polymerization to disperse MWNT very soon in PMMA. • A high and homogenous dispersion of MWNT in PMMA was achieved. • The modification of MWNT by AIBN was analyzed using Raman. • A covalent bonding between PMMA and MWNT was analyzed by FT-IR and Raman. • According to the results of PMMA-MWNT it was proposed a scheme reaction.

  8. Effect of varying nitrogen flow rates on the optical properties of amorphous-SiCN thin films

    Science.gov (United States)

    Rahman, Mohd Azam Abdul; Tong, Goh Boon; Mahmood, Mohamad Rusop; Siong, Chiu Wee; Yian, Haw Choon; Rahman, Saadah Abdul

    2016-11-01

    Series of amorphous silicon carbon nitride (a-SiCN) films are synthesized using RF-PECVD technique on glass and silicon substrates from precursor gas of silane, methane and nitrogen. In this work, the change in nitrogen flow rate from 0 sccm to 50 sccm is a mean used to vary the elemental composition and bonding properties which lead to change in optical properties. The films thickness varies between 327 nm to 944 nm. The changes for the stated properties are discussed against the change in the stated nitrogen flow rate. The optical properties are investigated by means of UV-VIS spectroscopy in the wavelength range of 190 nm to 2500 nm. The transmittance of the films at ultra-violet wavelength is found to increases with increase in nitrogen flow rate. The index of refraction, n obtained for SiCN films from transmittance and reflectance measurements is lower compared to SiC films. The films optical band gap increases from 1.74 eV to 2.08 eV before it decreases to 1.89 eV as nitrogen flow rate increases from 0 to 50 sccm. The optical dispersion parameters were determined according to Wemple and Didomenico method.

  9. Influence of processing and storage conditions on the mechanical and barrier properties of films cast from aqueous wheat gluten dispersions

    NARCIS (Netherlands)

    Lens, J.P.; Graaf, de L.A.; Stevels, W.M.; Dietz, C.H.J.T.; Verhelst, K.C.S.; Vereijken, J.M.; Kolster, P.

    2003-01-01

    A method was developed to prepare films based on industrial wheat gluten, from aqueous dispersion at neutral pH. An essential step in this procedure is to prepare aqueous dispersions in such a way that coagulation of the vital wheat gluten is prevented. In contrast to current procedures, adjustment

  10. Quantitative myocardial perfusion magnetic resonance imaging: the impact of pulsatile flow on contrast agent bolus dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Graafen, Dirk; Hamer, Julia; Weber, Stefan; Schreiber, Laura M, E-mail: graafen@uni-mainz.de [Section of Medical Physics, Department of Radiology, Johannes Gutenberg University Medical Center, Mainz (Germany)

    2011-08-21

    Myocardial blood flow (MBF) can be quantified using T{sub 1}-weighted first-pass magnetic resonance imaging (MRI) in combination with a tracer-kinetic model, like MMID4. This procedure requires the knowledge of an arterial input function which is usually estimated from the left ventricle (LV). Dispersion of the contrast agent bolus may occur between the LV and the tissue of interest. The aim of this study was to investigate the dispersion under conditions of physiological pulsatile blood flow, and to simulate its effect on MBF quantification. The dispersion was simulated in coronary arteries using a computational fluid dynamics (CFD) approach. Simulations were accomplished on straight vessels with stenosis of different degrees and shapes. The results show that dispersion is more pronounced under resting conditions than during hyperemia. Stenosis leads to a reduction of dispersion. In consequence, dispersion results in a systematic MBF underestimation between -0.4% and -9.3%. The relative MBF error depends not only on the dispersion but also on the actual MBF itself. Since MBF under rest is more underestimated than under stress, myocardial perfusion reserve is overestimated between 0.1% and 4.5%. Considering other sources of errors in myocardial perfusion MRI, systematic errors of MBF by bolus dispersion are relatively small.

  11. Mixed Platoon Flow Dispersion Model Based on Speed-Truncated Gaussian Mixture Distribution

    Directory of Open Access Journals (Sweden)

    Weitiao Wu

    2013-01-01

    Full Text Available A mixed traffic flow feature is presented on urban arterials in China due to a large amount of buses. Based on field data, a macroscopic mixed platoon flow dispersion model (MPFDM was proposed to simulate the platoon dispersion process along the road section between two adjacent intersections from the flow view. More close to field observation, truncated Gaussian mixture distribution was adopted as the speed density distribution for mixed platoon. Expectation maximum (EM algorithm was used for parameters estimation. The relationship between the arriving flow distribution at downstream intersection and the departing flow distribution at upstream intersection was investigated using the proposed model. Comparison analysis using virtual flow data was performed between the Robertson model and the MPFDM. The results confirmed the validity of the proposed model.

  12. Cellulose nanocrystal interactions probed by thin film swelling to predict dispersibility

    Science.gov (United States)

    Reid, Michael S.; Villalobos, Marco; Cranston, Emily D.

    2016-06-01

    The production of well-dispersed reinforced polymer nanocomposites has been limited due to poor understanding of the interactions between components. Measuring the cohesive particle-particle interactions and the adhesive particle-polymer interactions is challenging due to nanoscale dimensions and poor colloidal stability of nanoparticles in many solvents. We demonstrate a new cohesive interaction measurement method using cellulose nanocrystals (CNCs) as a model system; CNCs have recently gained attention in the composites community due to their mechanical strength and renewable nature. Multi-wavelength surface plasmon resonance spectroscopy (SPR) was used to monitor the swelling of CNC thin films to elucidate the primary forces between CNCs. This was achieved by measuring swelling in situ in water, acetone, methanol, acetonitrile, isopropanol, and ethanol and relating the degree of swelling to solvent properties. Films swelled the most in water where we estimate 1.2-1.6 nm spacings between CNCs (or 4-6 molecular layers of water). Furthermore, a correlation was found between film swelling and the solvent's Hildebrand solubility parameter (R2 = 0.9068). The hydrogen bonding component of the solubility parameters was more closely linked to swelling than the polar or dispersive components. The films remained intact in all solvents, and using DLVO theory we have identified van der Waals forces as the main cohesive interaction between CNCs. The trends observed suggest that solvents (and polymers) alone are not sufficient to overcome CNC-CNC cohesion and that external energy is required to break CNC agglomerates. This work not only demonstrates that SPR can be used as a tool to measure cohesive particle-particle interactions but additionally advances our fundamental understanding of CNC interactions which is necessary for the design of cellulose nanocomposites.The production of well-dispersed reinforced polymer nanocomposites has been limited due to poor understanding of

  13. Determination and analysis of dispersive optical constants of CuIn3S5 thin films

    Science.gov (United States)

    Khemiri, N.; Sinaoui, A.; Kanzari, M.

    2011-04-01

    CuIn3S5 thin films were prepared from powder by thermal evaporation under vacuum (10-6 mbar) onto glass substrates. The glass substrates were heated from 30 to 200 °C. The films were characterized for their optical properties using optical measurement techniques (transmittance and reflectance). We have determined the energy and nature of the optical transitions of films. The optical constants of the deposited films were determined in the spectral range 300-1800 nm from the analysis of transmission and reflection data. The Swanepoel envelope method was employed on the interference fringes of transmittance patterns for the determination of variation of refractive index with wavelength. Wemple-Di Domenico single oscillator model was applied to determine the optical constants such as oscillator energy E0 and dispersion energy Ed of the films deposited at different substrate temperatures. The electric free carrier susceptibility and the ratio of the carrier concentration to the effective mass were estimated according to the model of Spitzer and Fan.

  14. Refractive index dispersion of swift heavy ion irradiated BFO thin films using Surface Plasmon Resonance technique

    Science.gov (United States)

    Paliwal, Ayushi; Sharma, Savita; Tomar, Monika; Singh, Fouran; Gupta, Vinay

    2016-07-01

    Swift heavy ion irradiation (SHI) is an effective technique to induce defects for possible modifications in the material properties. There is growing interest in studying the optical properties of multiferroic BiFeO3 (BFO) thin films for optoelectronic applications. In the present work, BFO thin films were prepared by sol-gel spin coating technique and were irradiated using the 15 UD Pelletron accelerator with 100 MeV Au9+ ions at a fluence of 1 × 1012 ions cm-2. The as-grown films became rough and porous on ion irradiation. Surface Plasmon Resonance (SPR) technique has been identified as a highly sensitive and powerful technique for studying the optical properties of a dielectric material. Optical properties of BFO thin films, before and after irradiation were studied using SPR technique in Otto configuration. Refractive index is found to be decreasing from 2.27 to 2.14 on ion irradiation at a wavelength of 633 nm. Refractive index dispersion of BFO thin film (from 405 nm to 633 nm) before and after ion radiation was examined.

  15. GROWTH RATE DISPERSION (GRD OF THE (010 FACE OF BORAX CRYSTALS IN FLOWING SOLUTION

    Directory of Open Access Journals (Sweden)

    Suharso Suharso

    2010-06-01

    Full Text Available The growth rates of borax crystals from aqueous solutions in the (010 direction at various flow rates were measured. The observed variations of the growth rate can be represented by a normal distribution.  It was found that there is no correlation between growth rate distribution and solution flow under these experimental conditions.   Keywords: Growth rate dispersion (GRD, borax, flow rate

  16. Particle Dispersion Behaviors of Dense Gas-Particle Flows in Bubble Fluidized Bed

    OpenAIRE

    Xue Liu; Guohui Li; Sihao Lv

    2013-01-01

    An Euler-Euler two-fluid model incorporating a developed momentum transfer empirical coefficient is developed to study the particle dispersion behaviors of dense gas-particle flows in gas-fluidization reactor. In this model, the four-way couplings among gas-particles, particle-gas, and particle-particle collisions are fully considered based on kinetic theory of granular flows and an improved smooth continuous drag coefficient is utilized. Gas turbulent flow is solved by large eddy simulation....

  17. Influence of preparation conditions on the dispersion parameters of sprayed iron oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Akl, Alaa A., E-mail: alaaakl@link.net [Physics Department, Faculty of Science, El-Minia University, El-Minia 111955 (Egypt)

    2010-10-01

    Iron oxide thin films were prepared by spray pyrolysis technique (SPT) at various substrate temperatures (T{sub sub}) and different deposition time. X-ray diffraction (XRD) analysis showed that, at T{sub sub} {>=} 350 deg. C, a single phase of {alpha}-Fe{sub 2}O{sub 3} film is formed which has the rhombohedral structure. Moreover, the crystallinity was improved by increasing T{sub sub}. The effect of T{sub sub} as well as deposition time on the optical dispersion of these films has been investigated. The optical transmittance and reflectance measurements were performed by using spectrophotometer in the wavelength range from 300 to 2500 nm. The refractive index was determined by using Murmann's exact equation. It was observed that, the refractive index increased with increasing in both the T{sub sub} and film thickness. The optical dispersion parameters have been evaluated and analyzed by using Wemple-Didomenico equation. The obtained results showed that, the dielectric properties have weak dependencies of growth temperature and film thickness. At T{sub sub} {>=} 350 deg. C, the average values of oscillator energy, E{sub o} and dispersion energy, E{sub d} were found to be 5.96 and 34.08 eV. While at different thickness, the average values of dispersion energies were found to be 3.93 and 17.08 eV. Also, the average values of oscillator strength S{sub o} and single resonant frequency {omega}{sub o} were estimated 10.78 x 10{sup 13} m{sup -2} and 5.99 x 10{sup 15} Hz, while at different thickness were evaluating 4.81 x 10{sup 13} m{sup -2} and 6.11 x 10{sup 15} Hz. Furthermore, the optical parameters such as wavelength of single oscillator {lambda}{sub o}, plasma frequency {omega}{sub p}, and dielectric constant {epsilon} have been evaluated. The carrier concentration N{sub opt} by using Drud's theory was obtained the range of 5.07 x 10{sup 25} m{sup -3} to 1.04 x 10{sup 26} m{sup -3}.

  18. Thermo-osmotic flow in thin films

    CERN Document Server

    Bregulla, Andreas; Günther, Katrin; Mertig, Michael; Cichos, Frank

    2016-01-01

    We report on the first micro-scale observation of the velocity field imposed by a non-uniform heat content along the solid/liquid boundary. We determine both radial and vertical velocity components of this thermo-osmotic flow field by tracking single tracer nanoparticles. The measured flow profiles are compared to an approximate analytical theory and to numerical calculations. From the measured slip velocity we deduce the thermo-osmotic coefficient for both bare glass and Pluronic F-127 covered surfaces. The value for Pluronic F-127 agrees well with Soret data for polyethylene glycol, whereas that for glass differs from literature values and indicates the complex boundary layer thermodynamics of glass-water interfaces.

  19. Thermo-Osmotic Flow in Thin Films

    Science.gov (United States)

    Bregulla, Andreas P.; Würger, Alois; Günther, Katrin; Mertig, Michael; Cichos, Frank

    2016-05-01

    We report on the first microscale observation of the velocity field imposed by a nonuniform heat content along the solid-liquid boundary. We determine both radial and vertical velocity components of this thermo-osmotic flow field by tracking single tracer nanoparticles. The measured flow profiles are compared to an approximate analytical theory and to numerical calculations. From the measured slip velocity we deduce the thermo-osmotic coefficient for both bare glass and Pluronic F-127 covered surfaces. The value for Pluronic F-127 agrees well with Soret data for polyethylene glycol, whereas that for glass differs from literature values and indicates the complex boundary layer thermodynamics of glass-water interfaces.

  20. PIV Analysis of Ludwig Prandtl's Historic Flow Visualization Films

    CERN Document Server

    Willert, Christian

    2010-01-01

    Around 1930 Ludwig Prandtl and his colleagues O. Tietjens and W. M\\"uller published two films with visualizations of flows around surface piercing obstacles to illustrate the unsteady process of flow separation. These visualizations were achieved by recording the motion of fine particles sprinkled onto the water surface in water channels. The resulting images meet the relevant criteria of properly seeded recordings for particle image velocimetry (PIV). Processing these image sequences with modern PIV algorithms allows the visualization of flow quantities (e.g. vorticity) that were unavailable prior to the development of the PIV technique. The accompanying fluid dynamics video consists of selected original film sequences overlaid with visualizations obtained through PIV processing.

  1. Frequency dispersion of the magnetic anisotropy field in metallic magnetic films with the plane anisotropy of electrical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Zimin, A.B.; Kornev, Y.V.; Sementsova, T.M.; Sidorenkov, V.V.

    1986-07-01

    Presence of the frequency dispersion of the field of induced single axis magnetic anisotropy and the angular position of the axis of easy magnetization in the film plane has been determined in metallic magnetic films with plane anisotropy of electrical conductivity. Theoretical dependences have been obtained which given satisfactory agreement with experimental data for cobalt and permalloy films prepared by sputtering on glass substrates and using the incident molecular beam under an angle with the substrate.

  2. Gas phase dispersion in compost as a function of different water contents and air flow rates

    Science.gov (United States)

    Sharma, Prabhakar; Poulsen, Tjalfe G.

    2009-07-01

    Gas phase dispersion in a natural porous medium (yard waste compost) was investigated as a function of gas flow velocity and compost volumetric water content using oxygen and nitrogen as tracer gases. The compost was chosen because it has a very wide water content range and because it represents a wide range of porous media, including soils and biofilter media. Column breakthrough curves for oxygen and nitrogen were measured at relatively low pore gas velocities, corresponding to those observed in for instance soil vapor extraction systems or biofilters for air cleaning at biogas plants or composting facilities. Total gas mechanical dispersion-molecular diffusion coefficients were fitted from the breakthrough curves using a one-dimensional numerical solution to the advection-dispersion equation and used to determine gas dispersivities at different volumetric gas contents. The results showed that gas mechanical dispersion dominated over molecular diffusion with mechanical dispersion for all water contents and pore gas velocities investigated. Importance of mechanical dispersion increased with increasing pore gas velocity and compost water content. The results further showed that gas dispersivity was relatively constant at high values of compost gas-filled porosity but increased with decreasing gas-filled porosity at lower values of gas-filled porosity. Results finally showed that measurement uncertainty in gas dispersivity is generally highest at low values of pore gas velocity.

  3. A Study on Solute Dispersion in a Three Layer Blood-like Liquid Flowing through a Rigid Artery

    National Research Council Canada - National Science Library

    Sudip Debnath; Apu Kumar Saha; Ashis Kumar Roy

    2017-01-01

    The unsteady dispersion of a solute has been discussed by the method of generalized dispersion technique in a blood-like liquid flowing through a pipe under the combined effects of finite yield stress...

  4. Slip and flow dynamics of polydisperse thin polystyrene films.

    Science.gov (United States)

    Sabzevari, Seyed Mostafa; McGraw, Joshua D.; Jacobs, Karin; Wood-Adams, Paula M.

    2015-03-01

    We investigate the slip of binary and ternary mixtures of nearly monodisperse polystyrene samples on Teflon-coated (AF2400) silicon wafers using dewetting experiments. Binary mixtures of long and short chains along with ternary mixtures with a fixed weight-average molecular weight Mw but different number-average molecular weight Mn were prepared. Thin films of ca. 200 nm were spin coated on mica from polymer solutions and transferred to Teflon substrates. Above the glass transition temperature Tg the films break up via nucleation and growth of holes. The hole growth rate and rim morphology are monitored as a function of Mn and annealing protocol of the films before transfer to Teflon substrates. Slip properties, accessed using hydrodynamic models, and flow dynamics are then examined and compared. We found that the rim morphology and slip of polystyrene blends on Teflon depends on the molecular weight distribution. Similarly, flow dynamics is affected by the presence of short chains in mixture. Moreover, we can provoke differences in slip by choosing appropriate annealing and film transfer protocols for PS films that have first been spin cast on mica surfaces.

  5. The role of pair dispersion in turbulent flow

    DEFF Research Database (Denmark)

    Bourgoin, M.; Ouellette, N.T.; Xu, H.T.;

    2006-01-01

    Mixing and transport in turbulent flows - which have strong local concentration fluctuations - essential in many natural and industrial systems including reactions in chemical mixers, combustion in engines and burners, droplet formation in warm clouds, and biological odor detection and chemotaxis......, that the initial separation of the pair plays an important rote in the subsequent spreading of the fluid elements. These results have surprising consequences for the decay of concentration fluctuations and have applications to biological and chemical systems....

  6. Shear wave dispersion behaviors of soft, vascularized tissues from the microchannel flow model.

    Science.gov (United States)

    Parker, K J; Ormachea, J; McAleavey, S A; Wood, R W; Carroll-Nellenback, J J; Miller, R K

    2016-07-07

    The frequency dependent behavior of tissue stiffness and the dispersion of shear waves in tissue can be measured in a number of ways, using integrated imaging systems. The microchannel flow model, which considers the effects of fluid flow in the branching vasculature and microchannels of soft tissues, makes specific predictions about the nature of dispersion. In this paper we introduce a more general form of the 4 parameter equation for stress relaxation based on the microchannel flow model, and then derive the general frequency domain equation for the complex modulus. Dispersion measurements in liver (ex vivo) and whole perfused placenta (post-delivery) correspond to the predictions from theory, guided by independent stress relaxation measurements and consideration of the vascular tree structure.

  7. A new statistical model for subgrid dispersion in large eddy simulations of particle-laden flows

    Science.gov (United States)

    Muela, Jordi; Lehmkuhl, Oriol; Pérez-Segarra, Carles David; Oliva, Asensi

    2016-09-01

    Dispersed multiphase turbulent flows are present in many industrial and commercial applications like internal combustion engines, turbofans, dispersion of contaminants, steam turbines, etc. Therefore, there is a clear interest in the development of models and numerical tools capable of performing detailed and reliable simulations about these kind of flows. Large Eddy Simulations offer good accuracy and reliable results together with reasonable computational requirements, making it a really interesting method to develop numerical tools for particle-laden turbulent flows. Nonetheless, in multiphase dispersed flows additional difficulties arises in LES, since the effect of the unresolved scales of the continuous phase over the dispersed phase is lost due to the filtering procedure. In order to solve this issue a model able to reconstruct the subgrid velocity seen by the particles is required. In this work a new model for the reconstruction of the subgrid scale effects over the dispersed phase is presented and assessed. This innovative methodology is based in the reconstruction of statistics via Probability Density Functions (PDFs).

  8. Soap film flow visualization investigations of oscillating wing energy harvesters

    Science.gov (United States)

    Kirschmeier, Benjamin; Bryant, Matthew

    2015-03-01

    With increasing population and proliferation of wireless electronics, significant research attention has turned to harvesting energy from ambient sources such as wind and water flows at scales ranging from micro-watt to mega-watt levels. One technique that has recently attracted attention is the application of bio-inspired flapping wings for energy harvesting. This type of system uses a heaving and pitching airfoil to extract flow energy and generate electricity. Such a device can be realized using passive devices excited by aeroelastic flutter phenomena, kinematic mechanisms driven by mechanical linkages, or semi-active devices that are actively controlled in one degree of freedom and passively driven in another. For these types of systems, numerical simulations have showed strong dependence on efficiency and vortex interaction. In this paper we propose a new apparatus for reproducing arbitrary pitch-heave waveforms to perform flow visualization experiments in a soap film tunnel. The vertically falling, gravity driven soap film tunnel is used to replicate flows with a chord Reynolds number on the order of 4x104. The soap film tunnel is used to investigate leading edge vortex (LEV) and trailing edge vortex (TEV) interactions for sinusoidal and non-sinusoidal waveforms. From a qualitative analysis of the fluid structure interaction, we have been able to demonstrate that the LEVs for non-sinusoidal motion convect faster over the airfoil compared with sinusoidal motion. Signifying that optimal flapping frequency is dependent on the motion profile.

  9. Submicron writing by laser irradiation on metal nano-particle dispersed films toward flexible electronics

    Science.gov (United States)

    Watanabe, Akira; Aminuzzaman, Mohammod; Miyashita, Tokuji

    2009-02-01

    The requirement for microwiring technology by a wet process has significantly increased recently toward the achievement of printable and flexible electronics. We have developed the metal microwiring with a resolution higher than 1 μm by the laser direct writing technique using Ag and Cu nano-particle-dispersed films as precursors. The technique was applied to the microwiring on a flexible and transparent polymer film. The metallization is caused in a micro-region by focused laser beam, which reduces the thermal damage of the flexible polymer substrate during the metallization process. The laser direct writing technique is based on the efficient and fast conversion of photon energy to thermal energy by direct excitation of the plasmon absorption of a metal nano-particle, which provides Cu microwiring with a low resistivity owing to the inhibition of the surface oxidation of the Cu nano-particle.

  10. Disperse two-phase flows, with applications to geophysical problems

    CERN Document Server

    Berselli, Luigi Carlo; Iliescu, Traian

    2014-01-01

    In this paper we study the motion of a fluid with several dispersed particles whose concentration is very small (smaller than $10^{-3}$), with possible applications to problems coming from geophysics, meteorology, and oceanography. We consider a very dilute suspension of heavy particles in a quasi-incompressible fluid (low Mach number). In our case the Stokes number is small and --as pointed out in the theory of multiphase turbulence-- we can use an Eulerian model instead of a Lagrangian one. The assumption of low concentration allows us to disregard particle--particle interactions, but we take into account the effect of particles on the fluid (two-way coupling). In this way we can study the physical effect of particle inertia (and not only passive tracers), with a model similar to the Boussinesq equations. The resulting model is used in both direct numerical simulations and large eddy simulations of a dam-break (lock-exchange) problem, which is a well-known academic test case. Keywords: Dilute suspensions, E...

  11. Flow film boiling heat transfer for subcooled liquids flowing upward perpendicular to single horizontal cylinders

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Q.S. [Kobe Univ. of Mercantile Marine, Dept. of Nuclear Engineering (Japan); Shiotsu, M. [Kyoto Univ., Dept. of Energy Sci. and Tech. (Japan); Sakurai, A. [Kyoto Univ. (Japan)

    2001-07-01

    The knowledge of flow film boiling heat transfer on a horizontal cylinder in various liquids flowing upward perpendicular to the cylinder is important as the database for the safety evaluation of the accidents such as rapid power burst and pressure reduction in the nuclear power plants. Flow film boiling heat transfer from single horizontal cylinders in water and Freon-113 flowing upward perpendicular to the cylinder under subcooled conditions was measured under wide experimental conditions. The flow velocities ranged from 0 to 1 m/s, the system pressures ranged from 100 to 500 kPa, and the surface superheats were raised up to 800 K for water and 400 K for Freon-113, respectively. Platinum horizontal cylinders with diameters ranging from 0.7 to 5 mm were used as the test heaters. The test heater was heated by direct electric current. The experimental data of film boiling heat transfer coefficients show that they increase with the increase of flow velocity, liquid subcooling, system pressure and with the decrease of cylinder diameter. Based on the experimental data, a correlation for subcooled flow film boiling heat transfer including the effects of liquid subcooling and radiation was presented, which can describe the experimental data obtained within 20% for the flow velocities below 0.7 m/s, and within -30% to +20% for the higher flow velocities. The correlation also predicted well the data by Shigechi (1983), Motte and Bromley (1957), and Sankaran and Witte (1990) obtained for the larger diameter cylinders and higher flow velocities in various liquids at the pressures of near atmospheric. The Shigechi's data were in the range from about -20% to +15%, the data of Motte and Bromley were about 30%,and the data of Sankaran and Witte were within +20 % of the curves given by the corresponding predicted values. (authors)

  12. MHD Stability Analysis and Flow Controls of Liquid Metal Free Surface Film Flows as Fusion Reactor PFCs

    Science.gov (United States)

    Zhang, Xiujie; Pan, Chuanjie; Xu, Zengyu

    2016-12-01

    Numerical and experimental investigation results on the magnetohydrodynamics (MHD) film flows along flat and curved bottom surfaces are summarized in this study. A simplified modeling has been developed to study the liquid metal MHD film state, which has been validated by the existing experimental results. Numerical results on how the inlet velocity (V), the chute width (W) and the inlet film thickness (d0) affect the MHD film flow state are obtained. MHD stability analysis results are also provided in this study. The results show that strong magnetic fields make the stable V decrease several times compared to the case with no magnetic field, especially small radial magnetic fields (Bn) will have a significant impact on the MHD film flow state. Based on the above numerical and MHD stability analysis results flow control methods are proposed for flat and curved MHD film flows. For curved film flow we firstly proposed a new multi-layers MHD film flow system with a solid metal mesh to get the stable MHD film flows along the curved bottom surface. Experiments on flat and curved MHD film flows are also carried out and some firstly observed results are achieved. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2014GB125003 and 2013GB114002), National Natural Science Foundation of China (No. 11105044)

  13. Characterization of optical constants and dispersion parameters of highly transparent Ge20Se76Sn4 amorphous thin film

    Science.gov (United States)

    Abd-Elrahman, M. I.; Hafiz, M. M.; Abdelraheem, A. M.; Abu-Sehly, A. A.

    2015-12-01

    Amorphous chalcogenide Ge20Se76Sn4 thin films of six different thicknesses (50-350 nm) are prepared by the thermal evaporation technique. Optical transmission and reflection spectra, in the wavelength range of the incident photons from 250 to 2500 nm, are used to study the effect of the film thickness on some optical properties. It is found that the effect of film thickness leads to increase in the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The decrease in optical band gap energy with increasing the film thickness is attributed to the formation of a band tail which narrows down the band gap. Dispersion analyses of refractive index reveal a decrease in the single-oscillator energy and an increase in the dispersion energy with increase in film thickness.

  14. Thickness Dispersion of Surface Plasmon of Ag Nano-thin Films: Determination by Ellipsometry Iterated with Transmittance Method

    Science.gov (United States)

    Gong, Junbo; Dai, Rucheng; Wang, Zhongping; Zhang, Zengming

    2015-03-01

    Effective optical constants of Ag thin films are precisely determined with effective thickness simultaneously by using an ellipsometry iterated with transmittance method. Unlike the bulk optical constants in Palik's database the effective optical constants of ultrathin Ag films are found to strongly depend on the thickness. According to the optical data two branches of thickness dispersion of surface plasmon energy are derived and agreed with theoretical predication. The thickness dispersion of bulk plasmon is also observed. The influence of substrate on surface plasmon is verified for the first time by using ellipsometry. The thickness dependent effective energy loss function is thus obtained based on this optical method for Ag ultrathin films. This method is also applicable to other ultrathin films and can be used to establish an effective optical database for ultrathin films.

  15. Thickness-dependent dispersion parameters, energy gap and nonlinear refractive index of ZnSe thin films

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Deo [School of Computer Science & Engineering, Faculty of Engineering, SMVD University, Kakryal, Katra 182320, J& K (India); Shaaban, E.R., E-mail: esam_ramadan2008@yahoo.com [Physics Department, Faculty of Science, Al-Azhar University, Assiut 71542 (Egypt); Shapaan, M. [Department of Physics, Faculty of Science, Al-Azahar University, Cairo (Egypt); Mohamed, S.H. [Physics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); Othman, A.A. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Verma, K.D., E-mail: kdverma1215868@gmail.com [Material Science Research Laboratory, Department of Physics, S. V. College, Aligarh 202001, U.P. (India)

    2016-08-15

    Highlights: • Combined experimental and theoretical researches on ZnSe Thin Films. • The film thickness and refractive index were determined using envelope method. • The absorption coefficient and the energy gap were calculated. • Dispersion parameters were determined using Wemple-DiDomenico relation. • The third order susceptibility and nonlinear refractive index were calculated. - Abstract: Zinc selenide (ZnSe) thin films with different thicknesses were evaporated onto glass substrates using the thermal evaporation technique. X-ray diffraction analysis confirmed that both the film and powder have cubic zinc-blende structure. The fundamental optical parameters like absorption coefficient, extinction coefficient and band gap were evaluated in transparent region of transmittance and reflectance spectrum. The optical transition of the films was found to be allowed, where the energy gap increased from 2.576 to 2.702 eV with increasing film thickness. Also, the refractive index value increase with increasing film thickness. The refractive indices evaluated through envelope method were extrapolated by Cauchy dispersion relationship over the whole spectra range. Additionally, the dispersion of refractive index was determined in terms of Wemple-DiDomenico single oscillator model. Third order susceptibility and nonlinear refractive index were determined for different thickness of ZnSe thin films.

  16. Investigation of liquid phase axial dispersion in Taylor bubble flow by radiotracer residence time distribution analysis

    Directory of Open Access Journals (Sweden)

    Jin J.H.

    2013-05-01

    Full Text Available A gas-liquid Taylor bubble flow occurs in small diameter channels in which gas bubbles are separated by slugs of pure liquid. This type of flow regime is well suited for solid catalyzed gas-liquid reactors in which the reaction efficiency is a strong function of axial dispersion in the regions of pure liquid. This paper presents an experimental study of liquid phase axial dispersion in a Taylor bubble flow developed in a horizontal tube using high speed photography and radiotracer residence time distribution (RTD analysis. A parametric dependence of axial dispersion on average volume fraction of gas phase was also investigated by varying the relative volumetric flow rates of the two phases. 137mBa produced from a 137Cs/137mBa radionuclide generator was used as radiotracer and measurements were made using the NaI(Tl scintillation detectors. Validation of 137mBa in the form of barium chloride as aqueous phase radiotracer was also carried out. Axial Dispersion Model (ADM was used to simulate the hydrodynamics of the system and the results of the experiment are presented. It was observed that the system is characterized by very high values of Peclet Number (Pe∼102 which reveals an approaching plug type flow. The experimental and model estimated values of mean residence times were observed in agreement with each other.

  17. Rossby wave energy dispersion from tropical cyclone in zonal basic flows

    Science.gov (United States)

    Shi, Wenli; Fei, Jianfang; Huang, Xiaogang; Liu, Yudi; Ma, Zhanhong; Yang, Lu

    2016-04-01

    This study investigates tropical cyclone energy dispersion under horizontally sheared flows using a nonlinear barotropic model. In addition to common patterns, unusual features of Rossby wave trains are also found in flows with constant vorticity and vorticity gradients. In terms of the direction of the energy dispersion, the wave train can rotate clockwise and elongate southwestward under anticyclonic circulation (ASH), which contributes to the reenhancement of the tropical cyclone (TC). The wave train even splits into two obvious wavelike trains in flows with a southward vorticity gradient (WSH). Energy dispersed from TCs varies over time, and variations in the intensity of the wave train components typically occur in two stages. Wave-activity flux diagnosis and ray tracing calculations are extended to the frame that moves along with the TC to reveal the concrete progress of wave propagation. The direction of the wave-activity flux is primarily determined by the combination of the basic flow and the TC velocity. Along the flux, the distribution of pseudomomentum effectively illustrates the development of wave trains, particularly the rotation and split of wave propagation. Ray tracing involves the quantitative tracing of wave features along rays, which effectively coincide with the wave train regimes. Flows of a constant shear (parabolic meridional variation) produce linear (nonlinear) wave number variations. For the split wave trains, the real and complex wave number waves move along divergent trajectories and are responsible for different energy dispersion ducts.

  18. Harnessing Thin-Film Continuous-Flow Assembly Lines.

    Science.gov (United States)

    Britton, Joshua; Castle, Jared W; Weiss, Gregory A; Raston, Colin L

    2016-07-25

    Inspired by nature's ability to construct complex molecules through sequential synthetic transformations, an assembly line synthesis of α-aminophosphonates has been developed. In this approach, simple starting materials are continuously fed through a thin-film reactor where the intermediates accrue molecular complexity as they progress through the flow system. Flow chemistry allows rapid multistep transformations to occur via reaction compartmentalization, an approach not amenable to using conventional flasks. Thin film processing can also access facile in situ solvent exchange to drive reaction efficiency, and through this method, α-aminophosphonate synthesis requires only 443 s residence time to produce 3.22 g h(-1) . Assembly-line synthesis allows unprecedented reaction flexibility and processing efficiency. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Flow visualisation of the external flow from a converging slot-hole film-cooling geometry

    Science.gov (United States)

    Sargison, J. E.; Oldfield, M. L. G.; Guo, S. M.; Lock, G. D.; Rawlinson, A. J.

    2005-03-01

    This paper presents flow visualisation experiments for a novel film-cooling hole, the converging slot-hole or console for short. Previously published experimental results have demonstrated that the console improved both the heat transfer and the aerodynamic performance of turbine vane and rotor blade cooling systems. Flow visualisation data for a row of consoles were compared with that of cylindrical and fan-shaped holes and a slot at the same inclination angle of 35° to the surface, on a large-scale, flat-plate model at engine-representative Reynolds numbers in a low speed tunnel with ambient temperature mainstream flow. In the first set of experiments, the flow was visualised by using a fine nylon mesh covered with thermochromic liquid crystals, allowing the measurement of gas temperature contours in planes perpendicular to the flow. This data demonstrated that the console film was similar to a slot film, and remained thin and attached to the surface for the coolant-to-mainstream momentum flux ratios of 1.1 to 40 and for a case with no crossflow (infinite momentum flux ratio). A second set of flow visualisation experiments using water/dry-ice fog have confirmed these results and have shown that the flow through all coolant geometries is unsteady.

  20. Amplification, attenuation, and dispersion of sound in inhomogeneous flows. [of compressible gas

    Science.gov (United States)

    Kentzer, C. P.

    1975-01-01

    First order effects of gradients in nonuniform potential flows of a compressible gas are included in a dispersion relation for sound waves. Three nondimensional numbers, the ratio of the change in the kinetic energy in one wavelength to the thermal energy of the gas, the ratio of the change in the total energy in one wavelength to the thermal energy, and the ratio of the dilatation frequency (the rate of expansion per unit volume) to the acoustic frequency, play the dominant role permitting the separation of the effects of flow gradients into isotropic and anisotropic effects. Dispersion and attenuation (or amplification) of sound are proportional to the wavelength for small wavelength and depend on the direction of wave propagation relative to flow gradients. Modification of ray acoustics for the effects of flow gradients is suggested and conditions for amplification and attenuation of sound are discussed.

  1. Measurements in Film Cooling Flows with Periodic Wakes

    Science.gov (United States)

    2008-10-01

    camera, thermocouples, and constant current (cold- wire ) anemometry . Hot - wire anemometry was used for velocity measurements. The local film cooling...and constant temperature hot - wire anemometry were used to measure flow temperature and velocity, respectively. Boundary layer probes with 1.27 m...jet velocity and temperature were documented by Coulthard et al. 26 by traversing the constant current and hot - wire probes over the hole exit plane

  2. Modeling compressible multiphase flows with dispersed particles in both dense and dilute regimes

    Science.gov (United States)

    McGrath, T.; St. Clair, J.; Balachandar, S.

    2017-06-01

    Many important explosives and energetics applications involve multiphase formulations employing dispersed particles. While considerable progress has been made toward developing mathematical models and computational methodologies for these flows, significant challenges remain. In this work, we apply a mathematical model for compressible multiphase flows with dispersed particles to existing shock and explosive dispersal problems from the literature. The model is cast in an Eulerian framework, treats all phases as compressible, is hyperbolic, and satisfies the second law of thermodynamics. It directly applies the continuous-phase pressure gradient as a forcing function for particle acceleration and thereby retains relaxed characteristics for the dispersed particle phase that remove the constituent material sound velocity from the eigenvalues. This is consistent with the expected characteristics of dispersed particle phases and can significantly improve the stable time-step size for explicit methods. The model is applied to test cases involving the shock and explosive dispersal of solid particles and compared to data from the literature. Computed results compare well with experimental measurements, providing confidence in the model and computational methods applied.

  3. The energy-dispersive reflectometer at BESSY II: a challenge for thin film analysis

    CERN Document Server

    Pietsch, U; Geue, T; Neissendorfer, F; Brezsesinski, G; Symietz, C; Moehwald, H; Gudat, W

    2001-01-01

    Installed in 1999 the energy-dispersive reflectometer at the 13.2 bending magnet employs the exponentially decaying white X-ray emission spectrum of the 1.7 GeV storage ring of BESSY II outside the vacuum. Using an energy-dispersive detector specular and longitudinal-diffuse reflectivity spectra of thin films can be recorded simultaneously between 0.2 A sup - sup 1 films at room temperature and its change during annealing. At T=70 deg. C we observe an instantaneous decay of specular Bragg peaks accompanied with an increase of the diffuse scattering. This indicates the onset of the melting of 2D-ordered acid domains. The vertical diffusion coefficient is estimated to be about 2x10 sup - sup 2 sup 4 m sup 2 /s.

  4. Fluorescence photobleaching to evaluate flow velocity and hydrodynamic dispersion in nanoslits.

    Science.gov (United States)

    Cuenca, Amandine; Bodiguel, Hugues

    2012-05-01

    Velocity measurement is a key issue when studying flows below the micron scale, due to the lack of sensitivity of conventional detection techniques. We present an approach based on fluorescence photobleaching to evaluate flow velocity at the nanoscale by direct visualization. Solutions containing a fluorescent dye are injected into nanoslits. A photobleached line, created through laser beam illumination, moves through the channel due to the fluid flow. The velocity and effective diffusion coefficient are calculated from the temporal data of the line position and width respectively. The measurable velocity range is only limited by the diffusion rate of the fluorescent dye for low velocities and by the apparition of Taylor dispersion for high velocities. By controlling the pressure drop and measuring the velocity, we determine the fluid viscosity. The photobleached line spreads in time due to molecular diffusion and Taylor hydrodynamic dispersion. By taking into account the finite spatial and temporal extensions of the bleaching under flow, we determine the effective diffusion coefficient, which we find to be in good agreement with the expression of the two dimensional Taylor-Aris dispersion coefficient. Finally we analyze and discuss the role of the finite width of the rectangular slit on hydrodynamic dispersion.

  5. Interchain tube pressure effect in the flow dynamics of bi-disperse polymer melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.

    2015-01-01

    The constitutive equation as reported by Rasmussen and Huang (Rheologica Acta 53:199–208, 2014b), explaining the flow dynamics of oligomer (containing a least two Kuhn step)-diluted narrow molecular weight-distributed polymers were extended to general bi-disperse polymer melt system. It was assum...

  6. Method of calculation of a thermolysis and friction of a turbulent disperse flow in nozzles

    Science.gov (United States)

    Kovalnogov, Vladislav N.; Fedorov, Ruslan V.; Boyarkin, Mikhail S.

    2017-07-01

    The mathematical model and method of calculation of exchange processes in boundary layer of a carrying agent of a dispersible flow in nozzles which are adequately reflecting intensive aero mechanical and thermal influences of the condensed elements in the conditions of their directed cross movement in boundary layer and also effects of a laminarization of a current in a gradient stream.

  7. Flow induced dispersion analysis rapidly quantifies proteins in human plasma samples

    DEFF Research Database (Denmark)

    Poulsen, Nicklas N; Andersen, Nina Z; Østergaard, Jesper;

    2015-01-01

    to cumbersome and expensive assay development. In this work a new approach for quantification based on changes in diffusivity is presented. The apparent diffusivity of an indicator molecule interacting with the protein of interest is determined by Taylor Dispersion Analysis (TDA) in a hydrodynamic flow system...

  8. Backwards and forwards relative dispersion in turbulent flow: An experimental investigation

    DEFF Research Database (Denmark)

    Berg, J.; Lüthi, B.; Mann, J.;

    2006-01-01

    From particle tracking velocimetry we present an experimental measure of the ratio between backwards and forwards relative dispersion in an intermediate Reynolds number turbulent flow. Lack of time-reversal symmetry implies that their ratio may be different from 1. From a stochastic model, this has...

  9. Human-aided and natural dispersal drive gene flow across the range of an invasive mosquito.

    Science.gov (United States)

    Medley, Kim A; Jenkins, David G; Hoffman, Eric A

    2015-01-01

    Human-aided transport is responsible for many contemporary species introductions, yet the contribution of human-aided transport to dispersal within non-native regions is less clear. Understanding dispersal dynamics for invasive species can streamline mitigation efforts by targeting routes that contribute disproportionally to spread. Because of its limited natural dispersal ability, rapid spread of the Asian tiger mosquito (Aedes albopictus) has been attributed to human-aided transport, but until now, the relative roles of human-aided and natural movement have not been rigorously evaluated. Here, we use landscape genetics and information-theoretic model selection to evaluate 52 models representing 9240 pairwise dispersal paths among sites across the US range for Ae. albopictus and show that recent gene flow reflects a combination of natural and human-aided dispersal. Highways and water availability facilitate dispersal at a broad spatial scale, but gene flow is hindered by forests at the current distributional limit (range edge) and by agriculture among sites within the mosquito's native climatic niche (range core). Our results show that highways are important to genetic structure between range-edge and range-core pairs, suggesting a role for human-aided mosquito transport to the range edge. In contrast, natural dispersal is dominant at smaller spatial scales, reflecting a shifting dominance to natural movement two decades after introduction. These conclusions highlight the importance of (i) early intervention for species introductions, particularly those with readily dispersed dormant stages and short generation times, and (ii) strict monitoring of commercial shipments for transported immature stages of Ae. albopictus, particularly towards the northern edge of the US range.

  10. Surface self-assembly of fluorosurfactants during film formation of MMA/nBA colloidal dispersions.

    Science.gov (United States)

    Dreher, W R; Urban, M W

    2004-11-23

    These studies focus on the behavior of fluorosurfactants (FS) containing hydrophobic and ionic entities in the presence of methyl methacrylate/n-butyl acrylate (MMA/nBA) colloidal dispersions stabilized by sodium dodecyl sulfate (SDS). The presence of FS significantly not only alters the mobility of SDS in MMA/nBA films, but their hydrophobic and ionic nature results in self-assembly near the film-air (F-A) interface leading to different surface morphologies. Spherical islands and rodlike morphologies are formed which diminish the kinetic coefficient of friction of films by at least 3 orders of magnitude, and the presence of dual hydrophobic tails and an anionic head appears to have the largest effect on the surface friction. Using internal reflection IR imaging, these studies show that structural and chemical features of FS are directly related to their ability to migrate to the F-A interface and self-assemble to form specific morphological features. While the anionic nature of FS allows for SDS migration to the F-A interface and the formation of stable domains across the surface, intermolecular cohesion of nonionic FS allows for the formation of rodlike structures due to inability to form mixed micelles with SDS. These studies also establish the relationship between surface morphologies, kinetic coefficient of friction, and structural features of surfactants in the complex environments.

  11. Optical properties of Au-dispersed ZrO2 thin films

    Science.gov (United States)

    Huang, Weimin; Arizpe-Chávez, Humberto; Ramírez-Bon, Rafael; Espinoza-Beltrán, Francisco

    2002-03-01

    The optical absorption of gold nanoparticles dispersed within mesoporous zirconia thin films has been investigated. The samples of this material were prepared by the sol-gel technique. TEM studies showed Au nanoparticles with sizes in the range from 5 to 20 nm, embedded into the zirconia matrix. Also, XR diffraction spectra showed Au diffraction peaks corresponding to metallic nanoparticles with sizes in the range 7-9 nm. The accepted surface plasma resonance value for gold is 556 nm. The absorption spectra showed a red shift on the SPR position for samples thermally annealed. Also, a red shift is observed for samples treated with monoethanolamine (MEA) vapor. A lowering in the intensities of the absorption peaks for the treated samples is observed. On the other hand, larger gold dopping produces a blue shift in the absorption spectra, with an increment in the intensity of the absorption peaks. The Tauc-Lorentz fitting model allowed us to measure changes in the dielectric function of the material. Therefore, we conclude that not only the particle size drives the optical absorption spectra in gold-doped films. The observed opposite results can be explained if we introduce changes in the dielectric constant of the films.

  12. Can we trace biotic dispersals back in time? Introducing backward flow connectivity

    Directory of Open Access Journals (Sweden)

    Alessandro Ferrarini

    2014-06-01

    Full Text Available Connectivity in ecology deals with the problem of how species dispersal will happen given actual landscape and species presence/absence over such landscape. Hence it can be considered a forward (ahead in time scientific problem. I observe here that a backward theory of connectivity could be of deep interest as well: given the actual species presence/absence on the landscape, where with the highest probability such species is coming from? In other words, can we trace biotic dispersals back in time? Recently I have introduced a modelling and theoretical approach to ecological connectivity that is alternative to circuit theory and is able to fix the weak point of the "from-to" connectivity approach. The proposed approach holds also for mountain and hilly landscapes. In addition, it doesn't assume any intention for a species to go from source points to sink ones, because the expected path for the species is determined locally (pixel by pixel by landscape features. In this paper, I introduce a new theoretical and modelling approach called "backward flow connectivity". While flow connectivity predicts future species dispersal by minimizing at each step the potential energy due to fictional gravity over a frictional landscape, backward flow connectivity does exactly the opposite, i.e. maximizes potential energy at each step sending back the species to higher levels of potential energy due to fictional gravity on the frictional landscape. Using backward flow connectivity, one has at hand a new tool to revert timeline of species dispersal, hence being able to trace backward biotic dispersals. With few modifications, the applications of backward flow connectivity can be countless, for instance tracing back-in-time not only plants and animals but also ancient human migrations and viral paths.

  13. Three-dimensional dispersion induced by extreme tensile strain in La2-xSrxCuO4 films

    Science.gov (United States)

    Cloetta, D.; Ariosa, D.; Cancellieri, C.; Abrecht, M.; Mitrovic, S.; Pavuna, D.

    2006-07-01

    The electronic band structure probed by angle-resolved photoemission spectroscopy on thin epitaxial La2-xSrxCuO4 films under extreme tensile strain shows anomalous features compatible with c -axis dispersion. This result is in striking contrast with the usual quasi-two-dimensional (2D) dispersion observed up to now in most superconducting cuprates, including relaxed and compressively strained La2-xSrxCuO4 films grown under the same conditions. The data were analyzed using a 3D tight-binding dispersion for a body-centered-tetragonal lattice. We relate the enhancement of the c -axis dispersion to the significant displacement of the apical oxygen induced by epitaxial strain.

  14. Quantifying the effect of squirt flow dispersion from compliant clay porosity in clay bearing sandstones

    DEFF Research Database (Denmark)

    Sørensen, Morten Kanne; Fabricius, Ida Lykke

    2013-01-01

    Compliant porosity in the form of cracks is known to cause significant attenuation and velocity dispersion through pore pressure gradients and consequent relaxation, dubbed squirt flow. Squirt flow from cracks vanish at high confining stress due to crack closing. Studies on clay bearing sandstones......-squirt flow on the bulk modulus of a clay bearing sandstone. The predicted magnitude of the clay-squirt effect on the bulk modulus is compared with experimental data. The clay-squirt effect is found to possibly account for a significant portion of the deviances from Gassmann fluid substitution in claybearing...

  15. Hybrid Multiphase CFD Solver for Coupled Dispersed/Segregated Flows in Liquid-Liquid Extraction

    Directory of Open Access Journals (Sweden)

    Kent E. Wardle

    2013-01-01

    Full Text Available The flows in stage-wise liquid-liquid extraction devices include both phase segregated and dispersed flow regimes. As a additional layer of complexity, for extraction equipment such as the annular centrifugal contactor, free-surface flows also play a critical role in both the mixing and separation regions of the device and cannot be neglected. Traditionally, computional fluid dynamics (CFD of multiphase systems is regime dependent—different methods are used for segregated and dispersed flows. A hybrid multiphase method based on the combination of an Eulerian multifluid solution framework (per-phase momentum equations and sharp interface capturing using Volume of Fluid (VOF on selected phase pairs has been developed using the open-source CFD toolkit OpenFOAM. Demonstration of the solver capability is presented through various examples relevant to liquid-liquid extraction device flows including three-phase, liquid-liquid-air simulations in which a sharp interface is maintained between each liquid and air, but dispersed phase modeling is used for the liquid-liquid interactions.

  16. Formation of Tough Films by Evaporation of Water from Dispersions of Elastomer Microspheres Crosslinked with Rotaxane Supramolecules.

    Science.gov (United States)

    Hiroshige, Seina; Kureha, Takuma; Aoki, Daichi; Sawada, Jun; Aoki, Daisuke; Takata, Toshikazu; Suzuki, Daisuke

    2017-06-22

    Compared to rigid microspheres that consist, for example, of polystyrene or silica, soft and deformable elastomer microspheres can be used to generate colorless transparent films upon evaporating the solvent from microsphere-containing dispersions. To obtain tough films, a post-polymerization reaction to crosslink the microspheres is usually necessary, which requires extra additives during the drying process. This restriction renders this film-formation technology complex and rather unsuitable for applications in which impurities are undesirable. In the present study, it is demonstrated that tough elastomer microspheres that are crosslinked with rotaxanes can form tough bulk films upon evaporation of water from microsphere dispersions, so that post-polymerization reactions are not required. The results of this study should thus lead to new applications including coatings for biomaterials that need complete removal of all impurities from the materials prior to use. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Transitional phenomenon of particle dispersion in gas-solid two-phase flows

    Institute of Scientific and Technical Information of China (English)

    LUO Kun; FAN JianRen; CEN KeFa

    2007-01-01

    Without using any turbulent model, direct numerical simulation of a three-dimensional gas-solid two-phase turbulent jet was performed by finite volume method. The effects on dispersion of particles with different Stokes numbers by the transitional behavior of turbulent structures were investigated. To produce high-resolution results and reduce the computation and storage, the fractional-step projection algorithm was used to solve the governing equations of gas phase fluid. The low-storage, three-order Runge-Kutta scheme was used for time integration. The governing equations of particles were solved in the Lagrangian framework. These numerical schemes were validated by the good agreement between the statistical results of flow field and the related experimental data. In the study of particle dispersion, it was found that the effects on particle dispersion by the spanwise vortex structures were prominent. The new behaviors of particle dispersion were also observed during the evolution of the flow field, i.e. the transitional phenomenon of particle dispersion occurs for the particles with small and intermediate Stokes numbers.

  18. three-step model of dispersed flow heat transfer (post chf vertical flow)

    African Journals Online (AJOL)

    user

    The resulting equation gives the total heat transferred to the flow in terms of the mass flux, flow quality, .... superheated vapour, helps of course to desuperheat ... differential evaporation around the drop. The ... Thus we must first obtain the total.

  19. Microvascular blood flow resistance: Role of red blood cell migration and dispersion.

    Science.gov (United States)

    Katanov, Dinar; Gompper, Gerhard; Fedosov, Dmitry A

    2015-05-01

    Microvascular blood flow resistance has a strong impact on cardiovascular function and tissue perfusion. The flow resistance in microcirculation is governed by flow behavior of blood through a complex network of vessels, where the distribution of red blood cells across vessel cross-sections may be significantly distorted at vessel bifurcations and junctions. In this paper, the development of blood flow and its resistance starting from a dispersed configuration of red blood cells is investigated in simulations for different hematocrit levels, flow rates, vessel diameters, and aggregation interactions between red blood cells. Initially dispersed red blood cells migrate toward the vessel center leading to the formation of a cell-free layer near the wall and to a decrease of the flow resistance. The development of cell-free layer appears to be nearly universal when scaled with a characteristic shear rate of the flow. The universality allows an estimation of the length of a vessel required for full flow development, lc ≲ 25D, for vessel diameters in the range 10 μm red blood cell dispersion at vessel bifurcations and junctions on the flow resistance may be significant in vessels which are shorter or comparable to the length lc. Aggregation interactions between red blood cells generally lead to a reduction of blood flow resistance. The simulations are performed using the same viscosity for both external and internal fluids and the RBC membrane viscosity is not considered; however, we discuss how the viscosity contrast may affect the results. Finally, we develop a simple theoretical model which is able to describe the converged cell-free-layer thickness at steady-state flow with respect to flow rate. The model is based on the balance between a lift force on red blood cells due to cell-wall hydrodynamic interactions and shear-induced effective pressure due to cell-cell interactions in flow. We expect that these results can also be used to better understand the flow

  20. Influence of the disorder on tracer dispersion in a flow channel

    CERN Document Server

    Charette, V J; Chertcoff, R; Auradou, H; Hulin, J P; Ippolito, I; Charette, Victor Javier; Evangelista, Elisa; Chertcoff, Ricardo; Auradou, Harold; Hulin, Jean-Pierre; Ippolito, Irene

    2006-01-01

    Tracer dispersion is studied experimentally in periodic or disordered arrays of beads in a capillary tube. Dispersion is measured from light absorption variations near the outlet following a steplike injection of dye at the inlet. Visualizations using dye and pure glycerol are also performed in similar geometries. Taylor dispersion is dominant both in an empty tube and for a periodic array of beads: the dispersivity $l\\_d$ increases with the P\\'eclet number $Pe$ respectively as $Pe$ and $Pe^{0.82}$ and is larger by a factor of 8 in the second case. In a disordered packing of smaller beads (1/3 of the tube diameter) geometrical dispersion associated to the disorder of the flow field is dominant with a constant value of $l\\_d$ reached at high P\\'eclet numbers. The minimum dispersivity is slightly higher than in homogeneous nonconsolidated packings of small grains, likely due heterogeneities resulting from wall effects. In a disordered packing with the same beads as in the periodic configuration, $l\\_d$ is up to...

  1. Generalized Hasimoto Transform of One-Dimensional Dispersive Flows into Compact Riemann Surfaces

    Directory of Open Access Journals (Sweden)

    Eiji Onodera

    2008-05-01

    Full Text Available We study the structure of differential equations of one-dimensional dispersive flows into compact Riemann surfaces. These equations geometrically generalize two-sphere valued systems modeling the motion of vortex filament. We define a generalized Hasimoto transform by constructing a good moving frame, and reduce the equation with values in the induced bundle to a complex valued equation which is easy to handle. We also discuss the relationship between our reduction and the theory of linear dispersive partial differential equations.

  2. Experimental evidence of conformal invariance in soap film turbulent flows

    CERN Document Server

    Thalabard, S; Artana, G; Mininni, P D; Pouquet, A

    2010-01-01

    We present experimental evidence of statistical conformal invariance in isocontours of fluid thickness in experiments of two-dimensional turbulence using soap films. A Schlieren technique is used to visualize regions of the flow with constant film thickness, and association of isocontours with Schramm-L\\"owner evolution (SLE) is used to identify conformal invariance. In experiments where an inverse energy cascade develops, statistical evidence is consistent with such an association. The diffusivity of the associated one-dimensional Brownian process is close to 8/3, a value previously identified in isocontours of vorticity in high-resolution numerical simulations of two-dimensional turbulence (D. Bernard et al., Nature Phys. 2, 124, 2006). In experiments where the inverse energy cascade is not sufficiently developed, no statistical evidence of conformal invariance is found.

  3. Vibrating cantilever beam in a flowing soap film

    Science.gov (United States)

    Sajjanapu, Veera; Ward, Thomas

    2016-11-01

    We present an experimental study of the interaction between a flexible cantilever beam and a flowing fluid medium using a soap film. The vertically falling soap film is capable of attaining speeds ranging from 1.5 - 3 m/s with an operating test section width of 7.5 cm. Experiments were conducted for flexible cantilever beams of length L wake with a high-speed camera. Assuming small vibrational amplitudes, we consider the Euler-Bernoulli beam theory to understand the dynamics. From the analysis we find that the normalized average displacement is linear with respect to the square of the free-stream velocity. The vibrational amplitude is also discussed using a similar scaling. Finally, visualization of the downstream vortex structure is related to a beams displacement and vibrational frequency using dimensional analysis.

  4. Lagrangian filtered density function for LES-based stochastic modelling of turbulent dispersed flows

    CERN Document Server

    Innocenti, A; Chibbaro, S

    2016-01-01

    The Eulerian-Lagrangian approach based on Large-Eddy Simulation (LES) is one of the most promising and viable numerical tools to study turbulent dispersed flows when the computational cost of Direct Numerical Simulation (DNS) becomes too expensive. The applicability of this approach is however limited if the effects of the Sub-Grid Scales (SGS) of the flow on particle dynamics are neglected. In this paper, we propose to take these effects into account by means of a Lagrangian stochastic SGS model for the equations of particle motion. The model extends to particle-laden flows the velocity-filtered density function method originally developed for reactive flows. The underlying filtered density function is simulated through a Lagrangian Monte Carlo procedure that solves for a set of Stochastic Differential Equations (SDEs) along individual particle trajectories. The resulting model is tested for the reference case of turbulent channel flow, using a hybrid algorithm in which the fluid velocity field is provided b...

  5. Polarization holographic recording in Disperse Red1 doped polyurethane polymer film

    Science.gov (United States)

    Aleksejeva, J.; Gerbreders, A.; Gertners, U.; Reinfelde, M.; Teteris, J.

    2011-06-01

    In this report holographic recording of polarisation and surface relief gratings in Disperse Red 1 (DR1) doped polyurethane polymer films was studied. In this material DR1 is chemically bounded to polyurethane polymer main chain. Polarization holographic recording was performed by two orthogonal circularly polarized 532 nm laser beams. Photoinduced birefringence is a precondition for polarization holograms recording, therefore a detailed study of a photoinduced birefringence and changes of optical properties was performed. The lasers with wavelengths of 375nm, 448nm, 532 nm and 632.8 nm were used as pumping beam for sample excitation. The photoinduced birefringence Δn was measured at 532 nm and 632.8 nm wavelengths. The photoinduced birefringence dependence on the pumping beam wavelength and intensity was investigated. Surface relief grating (SRG) formation was observed during polarization holographic recording process. A profile of SRG was studied by AFM. A relationship between SRG formation and photoinduced birefringence has been discussed.

  6. High-order optical nonlinearities in nanocomposite films dispersed with semiconductor quantum dots at high concentrations

    Science.gov (United States)

    Tomita, Yasuo; Matsushima, Shun-suke; Yamagami, Ryu-ichi; Jinzenji, Taka-aki; Sakuma, Shohei; Liu, Xiangming; Izuishi, Takuya; Shen, Qing

    2017-06-01

    We describe the nonlinear optical properties of inorganic-organic nanocomposite films in which semiconductor CdSe quantum dots as high as 6.8 vol.% are dispersed. Open/closed Z-scan measurements, degenerate multi-wave mixing and femtosecond pump-probe/transient grating measurements are conducted. It is shown that the observed fifth-order optical nonlinearity has the cascaded third-order contribution that becomes prominent at high concentrations of CdSe QDs. It is also shown that there are picosecond-scale intensity-dependent and nanosecond-scale intensity-independent decay components in absorptive and refractive nonlinearities. The former is caused by the Auger process, while the latter comes from the electron-hole recombination process.

  7. Low-dispersion electrokinetic flows for expanded separation channels in microfluidic systems: multiple faceted interfaces.

    Science.gov (United States)

    Fiechtner, Gregory J; Cummings, Eric B

    2004-02-20

    A novel methodology to design on-chip conduction channels is presented for expansion of low-dispersion separation channels. Designs are examined using two-dimensional numerical solutions of the Laplace equation with a Monte Carlo technique to model diffusion. The design technique relies on trigonometric relations that apply for ideal electrokinetic flows. Flows are rotated and stretched along the abrupt interface between adjacent regions having differing specific permeability. Multiple interfaces can be placed in series along a channel. The resulting channels can be expanded to extreme widths while minimizing dispersion of injected analyte bands. These channels can provide a long path length for line-of-sight optical absorption measurements. Expanded sections can be reduced to enable point detection at the exit section of the channel. Designed to be shallow, these channels have extreme aspect ratios in the wide section, greatly increasing the surface-to-volume ratio to increase heat removal and decrease unwanted pressure-driven flow. The use of multiple interfaces is demonstrated by considering several three-interface designs. Faceted flow splitters can be constructed to divide channels into any number of exit channels while minimizing dispersion. The resulting manifolds can be used to construct medians for structural support in wide, shallow channels.

  8. Polar polymeric structures as wax dispersant flow improvers for paraffinic distillate fuels

    Energy Technology Data Exchange (ETDEWEB)

    El-Gamal, I.M.; Khidr, T.T.; Ghuiba, F.M. (Egyptian Petroleum Research Inst., Cairo (Egypt))

    1999-01-01

    Three (oxygen-based) and two (nitrogen + oxygen)-based polar polymeric structures were synthesized. The five copolymers were used as wax dispersant flow improver bifunctional additives (WDFI 1-5) for improving the cold flow properties of a paraffinic gas oil through cloud point (CP), cold filter plugging point (CFPP) and pour point (PP) tests. Results showed that the prepared additives exhibited high dispersing potential in terms of filterability improvement ([Delta]CFPP) correlated with the incorporated polar functional groups into their structures. On the contrary, their flowability in terms of ([Delta]PP) as flow improvers was not affected by polarity and appeared to depend primarily on the alkyl matching between copolymer alkyl chain moiety and average carbon number of wax content in the fuel. The prepared additives exhibited good compatibility with both natural wax dispersants and a commercial flow improver. The combined (nitrogen + oxygen)-based additive WDFI 5 has shown higher activity than oxygen-based ones and achieved the optimum effectiveness to the extent of 2, 8 and 15 C as [Delta]CP, [Delta]CFPP and [Delta]PP respectively. (orig.)

  9. Polar polymeric structures as wax dispersant flow improvers for paraffinic distillate fuels

    Energy Technology Data Exchange (ETDEWEB)

    El-Gamal, I.M.; Khidr, T.T.; Ghuiba, F.M. [Egyptian Petroleum Research Inst., Cairo (Egypt)

    1999-11-01

    Three (oxygen-based) and two (nitrogen + oxygen)-based polar polymeric structures were synthesized. The five copolymers were used as wax dispersant flow improver bifunctional additives (WDFI 1-5) for improving the cold flow properties of a paraffinic gas oil through cloud point (CP), cold filter plugging point (CFPP) and pour point (PP) tests. Results showed that the prepared additives exhibited high dispersing potential in terms of filterability improvement ({Delta}CFPP) correlated with the incorporated polar functional groups into their structures. On the contrary, their flowability in terms of ({Delta}PP) as flow improvers was not affected by polarity and appeared to depend primarily on the alkyl matching between copolymer alkyl chain moiety and average carbon number of wax content in the fuel. The prepared additives exhibited good compatibility with both natural wax dispersants and a commercial flow improver. The combined (nitrogen + oxygen)-based additive WDFI 5 has shown higher activity than oxygen-based ones and achieved the optimum effectiveness to the extent of 2, 8 and 15 C as {Delta}CP, {Delta}CFPP and {Delta}PP respectively. (orig.)

  10. Numerical simulations of a filament in a flowing soap film

    Science.gov (United States)

    Farnell, D. J. J.; David, T.; Barton, D. C.

    2004-01-01

    Experiments concerning the properties of soap films have recently been carried out and these systems have been proposed as experimental versions of theoretical two-dimensional liquids. A silk filament introduced into a flowing soap film, was seen to demonstrate various stable modes, and these were, namely, a mode in which the filament oscillates and one in which the filament is stationary and aligns with the flow of the liquid. The system could be forced from the oscillatory mode into the non- oscillatory mode by varying the length of the filament. In this article we use numerical and computational techniques in order to simulate the strongly coupled behaviour of the filament and the fluid. Preliminary results are presented for the specific case in which the filament is seen to oscillate continuously for the duration of our simulation. We also find that the filament oscillations are strongly suppressed when we reduce the effective length of the filament. We believe that these results are reminiscent of the different oscillatory and non-oscillatory modes observed in experiment. The numerical solutions show that, in contrast to experiment, vortices are created at the leading edge of the filament and are preferentially grown in the curvature of the filament and are eventually released from the trailing edge of the filament. In a similar manner to oscillating hydrofoils, it seems that the oscillating filaments are in a minimal energy state, extracting sufficient energy from the fluid to oscillate. In comparing numerical and experimental results it is possible that the soap film does have an effect on the fluid flow especially in the boundary layer where surface tension forces are large.

  11. Random lasing in dye-doped polymer dispersed liquid crystal film

    Science.gov (United States)

    Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

    2016-09-01

    A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

  12. Detecting barriers and facilities to species dispersal: Introducing sloping flow connectivity

    Directory of Open Access Journals (Sweden)

    Alessandro Ferrarini

    2014-09-01

    Full Text Available Connectivity in ecology deals with the problem of how biotic dispersals can happen, given actual landscape properties and species presence/absence over such landscape. Recently I have introduced a modelling approach (flow connectivity to ecological connectivity that is alternative to circuit theory, and is able to fix the weak point of the "from-to" connectivity approach. In addition, I've introduced "reverse flow connectivity" that couples evolutionary algorithms to partial differential equations in order to fix the problem of subjectivity in the attribution of friction values to landscape categories. I've also showed that flow connectivity can be used to predict biotic movements happened in the past (backward flow connectivity. To date, there has been little effort by conservation scientists towards detecting restoration opportunities by mapping barriers that strongly reduce movement potential. In this paper, I introduce a new kind of theoretical and modelling approach called "sloping flow connectivity". The goal of such proposal is to individuate and map barriers and facilities to species dispersals over the landscape. I define here a barrier as a landscape feature that impedes biotic movements, the removal of which would increase the potential for biotic shifts. Using sloping flow connectivity, it's possible to plan greenways and ecological networks in an effective manner, since it is able to enhance the real potential of each landscape elements to facilitate or obstruct both directional and overall species movements.

  13. Dispersion of nonlinear refractive index in layered WS2 and WSe2 semiconductor films induced by two-photon absorption.

    Science.gov (United States)

    Dong, Ningning; Li, Yuanxin; Zhang, Saifeng; McEvoy, Niall; Zhang, Xiaoyan; Cui, Yun; Zhang, Long; Duesberg, Georg S; Wang, Jun

    2016-09-01

    Both the nonlinear absorption and nonlinear refraction properties of WS2 and WSe2 semiconductor films have been characterized by using Z-scan technique with femtosecond pulses at the wavelength of 1040 nm. It is found that these films have two-photon absorption response with the nonlinear absorption coefficient of ∼103  cm GW-1, and a dispersion of nonlinear refractive index in the WS2 films that translated from positive in the monolayer to negative in bulk materials.

  14. Batchelor Scaling in Fast-Flowing Soap Films

    Science.gov (United States)

    Amarouchene, Y.; Kellay, H.

    2004-11-01

    The dynamics of a passive scalar such as a dye in the far dissipative range of fluid turbulence is a central problem in nonlinear physics. An important prediction for this problem was made by Batchelor over 40years ago and is known as Batchelor's scaling law. We here present strong evidence in favor of this law for the thickness fluctuations in the flow of a soap film past a flat plate. The results also capture the dissipative range of the scalar which turns out to have universal features. The probability density function of the scalar increments and their structure functions come out in nice agreement with theoretical predictions.

  15. Microstructured Thin Film Nitinol for a Neurovascular Flow-Diverter

    Science.gov (United States)

    Chen, Yanfei; Howe, Connor; Lee, Yongkuk; Cheon, Seongsik; Yeo, Woon-Hong; Chun, Youngjae

    2016-03-01

    A cerebral aneurysm occurs as a result of a weakened blood vessel, which allows blood to flow into a sac or a ballooned section. Recent advancement shows that a new device, ‘flow-diverter’, can divert blood flow away from the aneurysm sac. People found that a flow-diverter based on thin film nitinol (TFN), works very effectively, however there are no studies proving the mechanical safety in irregular, curved blood vessels. Here, we study the mechanical behaviors and structural safety of a novel microstructured TFN membrane through the computational and experimental studies, which establish the fundamental aspects of stretching and bending mechanics of the structure. The result shows a hyper-elastic behavior of the TFN with a negligible strain change up to 180° in bending and over 500% in radial stretching, which is ideal in the use in neurovascular curved arteries. The simulation determines the optimal joint locations between the TFN and stent frame. In vitro experimental test qualitatively demonstrates the mechanical flexibility of the flow-diverter with multi-modal bending. In vivo micro X-ray and histopathology study demonstrate that the TFN can be conformally deployed in the curved blood vessel of a swine model without any significant complications or abnormalities.

  16. Thermal degradation behaviour of nanoamphiphilic chitosan dispersed poly (lactic acid) bionanocomposite films.

    Science.gov (United States)

    Pal, Akhilesh Kumar; Katiyar, Vimal

    2017-02-01

    In the present study, nano-amphiphilic chitosan termed as chitosan-grafted-oligo l-lactic acid (CH-g-OLLA), is synthesized by microwave initiated insitu condensation polymerization. The synthesized CH-g-OLLA becomes hydrophobic in nature due to chemical bond formation between chitosan backbone and OLLA chains. Further, CH-g-OLLA (30%) bionanocomposite is used as a nanofiller in poly (lactic acid)/chitosan-grafted-oligo l-lactic acid (PLA/CH-g-OLLA) bionanocomposite films. Surface morphology shows a homogeneous dispersion of CH-g-OLLA in the form of spherical aggregates, which vary in the range of ∼20 to 150nm. Non-isothermal degradation kinetics, proposed by Kissinger, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Augis & Bennett models, are utilized to estimate the activation energies (Ea) for PLA, which are 254.1, 260.2, 257.0 and 259.1kJmol(-1) respectively. The reduction in Ea values of bionanocomposite films may be elucidated by intermolecular distance and enrichment in chain mobility. The evolved gaseous products like hydrocarbons, carbon dioxide, carbon monoxide and cyclic oligomers are successfully identified with TG-FTIR analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Numerical and Experimental Studies on Flow and Pollutant Dispersion in Urban Street Canyons

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this study numerical simulations and water tank experiments were used to investigate the flow and pollutant dispersion in an urban street canyon. Two types of canyon geometry were tested. The studies indicate that in a step-up notch canyon (higher buildings on the downstream side of the canyon), the height and shape of the upstream lower buildings plays an important role in flow pattern and pollutant dispersion,while in a step-down notch canyon (lower buildings on the downstream side), the downstream lower buildings have little influence. The studies also show that the substitution of tall towers for parallelepiped buildings on one side of the canyon may enhance the street ventilation and decrease the pollutant concentration emitted by motor vehicles.

  18. Laboratory experiments on dispersive transport across interfaces: The role of flow direction

    Energy Technology Data Exchange (ETDEWEB)

    Berkowitz, B.; Cortis, A.; Dror, I.; Scher, H.

    2009-04-01

    We present experimental evidence of asymmetrical dispersive transport of a conservative tracer across interfaces between different porous materials. Breakthrough curves are measured for tracer pulses that migrate in a steady state flow field through a column that contains adjacent segments of coarse and fine porous media. The breakthrough curves show significant differences in behavior, with tracers migrating from fine medium to coarse medium arriving significantly faster than those from coarse medium to fine medium. As the flow rate increases, the differences between the breakthrough curves diminish. We argue that this behavior indicates the occurrence of significant, time-dependent tracer accumulation in the resident concentration profile across the heterogeneity interface. Conventional modeling using the advection-dispersion equation is demonstrated to be unable to capture this asymmetric behavior. However, tracer accumulation at the interface has been observed in particle-tracking simulations, which may be related to the asymmetry in the observed breakthrough curves.

  19. Thickness dependence of dispersion parameters of the MoO{sub x} thin films prepared using the vacuum evaporation technique

    Energy Technology Data Exchange (ETDEWEB)

    Akın, Ümmühan, E-mail: uakin@selcuk.edu.tr; Şafak, Haluk

    2015-10-25

    The optical behaviors of molybdenum oxide thin films are highly important due to their widespread applications. In the present paper, the effect of thickness on the structure, morphology and optical properties of molybdenum oxide (MoO{sub x}) thin films prepared on Corning glass substrates using thermal evaporation technique was studied. The structure and morphology of films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively, while their optical properties were investigated by UV-VIS-NIR spectrophotometry in the spectral range from 300 to 2500 nm. It was observed that whole films have amorphous structure and also they showed rather high transmittance values reached nearly up to 90%. Absorption analysis showed two types of electronic transitions; both direct and indirect interband transition energy values of films decrease from 4.47 to 3.45 eV and from 3.00 to 2.75 eV, respectively, with increasing the film thickness, while the width of the localized states tail increases with thickness. This decrease in the band gap value can be attributed to the rising oxygen-ion vacancy densities with the thickness. The refractive indices of films were calculated from Sellmeier coefficients determined by nonlinear curve fitting method based on the measured transmittance spectral data. The dispersion of the refractive index was discussed in terms of the Wemple-DiDomenico single-oscillator model. The dispersion parameters such as average oscillator energy, E{sub o}, the dispersion energy, E{sub d}, and static refractive index n{sub o} were evaluated and they found to vary significantly with the film thickness. - Highlights: • MoO{sub x} thin films with different thickness were prepared using the vacuum evaporation technique. • The variation of fundamental absorption edge with the film thickness was determined. • A detailed dispersion analysis based on the Wemple-DiDomenico model was performed. • The dependence of all

  20. Determination of Diffusion and Dispersion Parameters for Flow in Porous Media

    OpenAIRE

    Kohno, Iichiro; Nishigaki, Makoto

    1982-01-01

    The purposes of this research is an investigation of the intrusion of sea water into coastal aquifers. For this subject, this paper deals with proposing rational methods of getting diffusion coefficient and dispersion parameter for flow in porous media in a laboratory. These parameters of soil are indispensable in order to apply an analytical approach or a numerical approach to actual salt water intrusion problems. Experimental apparatuses were constructed and test procedures were also develo...

  1. On the Motion of an Annular Film in Microgravity Gas-Liquid Flow

    Science.gov (United States)

    McQuillen, John B.

    2002-01-01

    Three flow regimes have been identified for gas-liquid flow in a microgravity environment: Bubble, Slug, and Annular. For the slug and annular flow regimes, the behavior observed in vertical upflow in normal gravity is similar to microgravity flow with a thin, symmetrical annular film wetting the tube wall. However, the motion and behavior of this film is significantly different between the normal and low gravity cases. Specifically, the liquid film will slow and come to a stop during low frequency wave motion or slugging. In normal gravity vertical upflow, the film has been observed to slow, stop, and actually reverse direction until it meets the next slug or wave.

  2. CO$_2$ dissolution controlled by buoyancy driven shear dispersion in a background hydrological flow

    CERN Document Server

    Unwin, H Juliette T; Woods, Andrew W

    2015-01-01

    We present an analytical and numerical study of the long-time flow which controls the dissolution of a plume of CO$_2$ following injection into an anticline structure in a deep saline aquifer of finite vertical extent. Over times of tens to thousands of years, some of the CO$_2$ will dissolve into the underlying groundwater to produce a region of relatively dense, CO$_2$ saturated water directly below the plume of CO$_2$. Continued dissolution then requires the supply of CO$_2$ unsaturated aquifer water. This may be provided by a background hydrological flow or buoyancy driven flow caused by the density contrast between the CO$_2$ saturated and unsaturated water in the aquifer. At long times, the interaction of the cross-layer diffusive mixing with the buoyancy, leads to buoyancy driven shear dispersion of the CO$_2$. With a background hydrological flow, the upstream transport of dissolved CO$_2$ by this dispersion becomes balanced by the oncoming hydrological flow so that CO$_2$ rich water can only spread a ...

  3. Pore scale mixing and macroscopic solute dispersion regimes in polymer flows inside 2D model networks

    CERN Document Server

    D'Angelo, M V; Allain, C; Hulin, J P; Angelo, Maria Veronica D'; Auradou, Harold; Allain, Catherine; Hulin, Jean-Pierre

    2006-01-01

    A change of solute dispersion regime with the flow velocity has been studied both at the macroscopic and pore scales in a transparent array of capillary channels using an optical technique allowing for simultaneous local and global concentration mappings. Two solutions of different polymer concentrations (500 and 1000 ppm) have been used at different P\\'eclet numbers. At the macroscopic scale, the displacement front displays a diffusive spreading: for $Pe \\leq 10$, the dispersivity $l\\_d$ is constant with $Pe$ and increases with the polymer concentration; for $Pe > 10$, $l\\_d$ increases as $Pe^{1.35}$ and is similar for the two concentrations. At the local scale, a time lag between the saturations of channels parallel and perpendicular to the mean flow has been observed and studied as a function of the flow rate. These local measurements suggest that the change of dispersion regime is related to variations of the degree of mixing at the junctions. For $Pe \\leq 10$, complete mixing leads to pure geometrical di...

  4. Characterization of the optical constants and dispersion parameters of chalcogenide Te40Se30S30 thin film: thickness effect

    Science.gov (United States)

    Abd-Elrahman, M. I.; Hafiz, M. M.; Qasem, Ammar; Abdel-Rahim, M. A.

    2016-02-01

    Chalcogenide Te40Se30S30 thin films of different thickness (100-450 nm) are prepared by thermal evaporation of the Te40Se30S30 bulk. X-ray examination of the film shows some prominent peaks relate to crystalline phases indicating the crystallization process. The calculated particles of crystals from the X-ray diffraction peaks are found to be from 11 to 26 nm. As the thickness increases, the transmittance decreases and the reflectance increases. This could be attributed to the increment of the absorption of photons as more states will be available for absorbance in the case of thicker films. The decrease in the direct band gap with thickness is accompanied with an increase in energy of localized states. The obtained data for the refractive index could be fit to the dispersion model based on the single oscillator equation. The single-oscillator energy decreases, while the dispersion energy increases as the thickness increases.

  5. Changing the flux flow state in weak pinning superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Leo, A., E-mail: antoleo@sa.infn.it [Physics Department E.R. Caianiello, University of Salerno, Via Giovanni Paolo II, 132, Stecca 9, I-84084 Fisciano, SA (Italy); CNR-SPIN Salerno, Via Giovanni Paolo II, 132, Stecca 9, I-84084 Fisciano, SA (Italy); Grimaldi, G. [CNR-SPIN Salerno, Via Giovanni Paolo II, 132, Stecca 9, I-84084 Fisciano, SA (Italy); Nigro, A. [Physics Department E.R. Caianiello, University of Salerno, Via Giovanni Paolo II, 132, Stecca 9, I-84084 Fisciano, SA (Italy); CNR-SPIN Salerno, Via Giovanni Paolo II, 132, Stecca 9, I-84084 Fisciano, SA (Italy); Bruno, E.; Priolo, F. [Matis IMM-CNR and Physics-Astronomy Department, Catania University, CT 95123 (Italy); Pace, S. [Physics Department E.R. Caianiello, University of Salerno, Via Giovanni Paolo II, 132, Stecca 9, I-84084 Fisciano, SA (Italy); CNR-SPIN Salerno, Via Giovanni Paolo II, 132, Stecca 9, I-84084 Fisciano, SA (Italy)

    2014-08-15

    Highlights: • We analyzed the effect of light ion irradiation on weak pinning superconductors. • We found the light ion irradiation has a strong impact on current currying stability. • We compared the results to the ones of the case of moderate strong pinning materials. - Abstract: The current carrying dissipative state well above the critical current it is known to be related to the pinning properties of the material and to the microscopic mechanisms of vortex dynamics. Moreover, it has been demonstrated that in low temperature superconducting films exhibiting moderately strong pinning the light ion irradiation has the effect of changing the distribution of the pinning centers without changing their pinning strength and this results into an increase of current stability in the flux flow state. Here we present the results of light ion irradiation on weak pinning superconducting films focusing on the influence of pinning properties of the material in the flux flow state. We realize that the possibility to switch to low dissipations by changing weak pinning is not straightforward.

  6. Dense bubble flow in a silo: An unusual flow of a dispersed medium

    Science.gov (United States)

    Bertho, Yann; Becco, Christophe; Vandewalle, Nicolas

    2006-05-01

    The dense flow of air bubbles in a two-dimensional silo (through an aperture D ) filled with a liquid is studied experimentally. A particle tracking technique has been used to bring out the main properties of the flow: displacements of the bubbles, transverse, and axial velocities. The behavior of the air bubbles is observed to present similarities with nondeformable solid grains in a granular flow. Nevertheless, a correlation between the bubble velocities and their deformations has been evidenced. Moreover, a new discharge law (Beverloo like) must be considered for such a system, where the flow rate is observed to vary as D1/2 and depends on the deformability of the particles.

  7. Thin liquid films with time-dependent chemical reactions sheared by an ambient gas flow

    Science.gov (United States)

    Bender, Achim; Stephan, Peter; Gambaryan-Roisman, Tatiana

    2017-08-01

    Chemical reactions in thin liquid films are found in many industrial applications, e.g., in combustion chambers of internal combustion engines where a fuel film can develop on pistons or cylinder walls. The reactions within the film and the turbulent outer gas flow influence film stability and lead to film breakup, which in turn can lead to deposit formation. In this work we examine the evolution and stability of a thin liquid film in the presence of a first-order chemical reaction and under the influence of a turbulent gas flow. Long-wave theory with a double perturbation analysis is used to reduce the complexity of the problem and obtain an evolution equation for the film thickness. The chemical reaction is assumed to be slow compared to film evolution and the amount of reactant in the film is limited, which means that the reaction rate decreases with time as the reactant is consumed. A linear stability analysis is performed to identify the influence of reaction parameters, material properties, and environmental conditions on the film stability limits. Results indicate that exothermic reactions have a stabilizing effect whereas endothermic reactions destabilize the film and can lead to rupture. It is shown that an initially unstable film can become stable with time as the reaction rate decreases. The shearing of the film by the external gas flow leads to the appearance of traveling waves. The shear stress magnitude has a nonmonotonic influence on film stability.

  8. Structure, optical spectroscopy and dispersion parameters of ZnGa2Se4 thin films at different annealing temperatures

    Science.gov (United States)

    Fadel, M.; Yahia, I. S.; Sakr, G. B.; Yakuphanoglu, F.; Shenouda, S. S.

    2012-06-01

    Thin films of ZnGa2Se4 were deposited by thermal evaporation method of pre-synthesized ingot material onto highly cleaned microscopic glass substrates. The chemical composition of the investigated compound thin film form was determined by means of energy-dispersive X-ray spectroscopy. X-ray diffraction XRD analysis revealed that the powder compound is polycrystalline and the as-deposited and the annealed films at Ta = 623 and 673 K have amorphous phase, while that annealed at Ta = 700 K is polycrystalline with a single phase of a defective chalcopyrite structure similar to that of the synthesized material. The unit-cell lattice parameters were determined and compared with the reported data. Also, the crystallite size L, the dislocation density δ and the main internal strain ɛ were calculated. Analyses of the AFM images confirm the nanostructure of the prepared annealed film at 700 K. The refractive index n and the film thickness d were determined from optical transmittance data using Swanepoel's method. It was found that the refractive index dispersion data obeys the single oscillator model from which the dispersion parameters were determined. The electric susceptibility of free carriers and the carrier concentration to the effective mass ratio were determined according to the model of Spitzer and Fan. The analysis of the optical absorption revealed both the indirect and direct energy gaps. The indirect optical gaps are presented in the amorphous films (as-deposited, annealed at 623 and 673 K), while the direct energy gap characterized the polycrystalline film at 700 K. Graphical representations of ɛ1, ɛ2, tan δ, - Im[1/ɛ*] and - Im[(1/ɛ* + 1)] are also presented. ZnGa2Se4 is a good candidate for optoelectronic and solar cell devices.

  9. Flow-Angle and Airspeed Sensor System (FASS) Using Flush-Mounted Hot-Films Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Micron-thin surface hot-film signatures will be used to simultaneously obtain airspeed and flow direction. The flow-angle and airspeed sensor system (FASS) will...

  10. Preparation and Characterization of Sol-Gel Derived Au Nanoparticle Dispersed Y2O3:Eu Films

    Institute of Scientific and Technical Information of China (English)

    Guo Hai; Zhang Weiping; Dong Ning; Lou Liren; Yin Min; Tillement O; Mugnier J; Bernstein E; Brevet P F

    2005-01-01

    Gold nanoparticles dispersed Y2O3 films were prepared through a sol-gel method by using yttrium acetate and Au nanoparticles colloid as precursors. The films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-VIS absorption spectra. XRD patterns and TEM images of Y2O3+Au films give the same results on structure and particle size as that of pure Y2O3 films. The surface plasma resonance (SPR) of Au nanoparticles in Y2O3+Au film was observed around 550 nm in the absorption spectrum and its position shifts to red with increasing annealing temperature is caused by the increase of dielectric constant of Y2O3 matrix and the size of Au nanoparticles. The second and third order nonlinear optical effects of Y2O3+Au films were also observed. The photoluminescent properties of Y2O3:Eu+Au films were investigated and results indicate that there exist an energy transfer from Eu3+ to Au nanoparticles and this energy transfer decreases the emission of Eu3+ in Y2O3:Eu+Au film.

  11. Dispersion in the large-deviation regime. Part I: shear flows and periodic flows

    CERN Document Server

    Haynes, P H

    2014-01-01

    The dispersion of a passive scalar in a fluid through the combined action of advection and molecular diffusion is often described as a diffusive process, with an effective diffusivity that is enhanced compared to the molecular value. However, this description fails to capture the tails of the scalar concentration distribution in initial-value problems. To remedy this, we develop a large-deviation theory of scalar dispersion that provides an approximation to the scalar concentration valid at much larger distances away from the centre of mass, specifically distances that are $O(t)$ rather than $O(t^{1/2})$, where $t \\gg 1$ is the time from the scalar release. The theory centres on the calculation of a rate function obtained by solving a one-parameter family of eigenvalue problems which we derive using two alternative approaches, one asymptotic, the other probabilistic. We emphasise the connection between large deviations and homogenisation: a perturbative solution of the eigenvalue problems reduces at leading o...

  12. Monodisperse granular flows in viscous dispersions in a centrifugal acceleration field

    Science.gov (United States)

    Cabrera, Miguel Angel; Wu, Wei

    2016-04-01

    Granular flows are encountered in geophysical flows and innumerable industrial applications with particulate materials. When mixed with a fluid, a complex network of interactions between the particle- and fluid-phase develops, resulting in a compound material with a yet unclear physical behaviour. In the study of granular suspensions mixed with a viscous dispersion, the scaling of the stress-strain characteristics of the fluid phase needs to account for the level of inertia developed in experiments. However, the required model dimensions and amount of material becomes a main limitation for their study. In recent years, centrifuge modelling has been presented as an alternative for the study of particle-fluid flows in a reduced scaled model in an augmented acceleration field. By formulating simple scaling principles proportional to the equivalent acceleration Ng in the model, the resultant flows share many similarities with field events. In this work we study the scaling principles of the fluid phase and its effects on the flow of granular suspensions. We focus on the dense flow of a monodisperse granular suspension mixed with a viscous fluid phase, flowing down an inclined plane and being driven by a centrifugal acceleration field. The scaled model allows the continuous monitoring of the flow heights, velocity fields, basal pressure and mass flow rates at different Ng levels. The experiments successfully identify the effects of scaling the plastic viscosity of the fluid phase, its relation with the deposition of particles over the inclined plane, and allows formulating a discussion on the suitability of simulating particle-fluid flows in a centrifugal acceleration field.

  13. Effect of solution molarity on optical dispersion energy parameters and electrochromic performance of Co3O4 films

    Science.gov (United States)

    Dhas, C. Ravi; Venkatesh, R.; Sivakumar, R.; Raj, A. Moses Ezhil; Sanjeeviraja, C.

    2017-10-01

    Co3O4 films were deposited on glass and FTO (F:SnO2) substrates by different solution molarities (0.05-0.20 M) through nebulizer spray technique. The crystalline quality of the films was evaluated by X-ray diffraction. The morphological variation of Co3O4 films for different solution concentration was observed from scanning electron microscopy. Optical constants (n and k) and dispersion energy parameters were calculated by fitting the transmittance curves using Swanepoel envelope method. The electrical parameters such as sheet resistance and activation energy were estimated using four probe method. The electrochromic performance of the films was analyzed by electrochemical measurements such as cyclic voltammetry, chronoamperometry, chronocoulometry and optical contrast studies.

  14. Dispersion of a suspension plug in oscillatory pressure-driven flow

    Science.gov (United States)

    Cui, Francis R.; Howard, Amanda A.; Maxey, Martin R.; Tripathi, Anubhav

    2017-09-01

    We investigate the dispersion of finite lengths of concentrated suspended particles, or suspension plugs, in a microcapillary as they are sheared in an oscillating pressure-driven flow. In the experiments, plugs of neutrally buoyant, noncolloidal particles (90-μ m mean diameter) suspended in viscous fluid at low and high concentrations are observed for various values of applied strain of this cyclic shearing flow. No significant increase in the overall plug length is seen near the centerline after numerous cycles. However, significant streamwise particle migration was observed near the walls of the capillary, becoming more pronounced with increasing strain amplitude. Related numerical simulations for a suspension plug sheared in a planar channel show similar results and elucidate the dynamics for this strongly inhomogeneous flow and the anomalous particle fluxes that develop.

  15. Constant gradient PFG sequence and automated cumulant analysis for quantifying dispersion in flow through porous media

    Science.gov (United States)

    Scheven, U. M.

    2013-12-01

    This paper describes a new variant of established stimulated echo pulse sequences, and an analytical method for determining diffusion or dispersion coefficients for Gaussian or non-Gaussian displacement distributions. The unipolar displacement encoding PFGSTE sequence uses trapezoidal gradient pulses of equal amplitude g and equal ramp rates throughout while sampling positive and negative halves of q-space. Usefully, the equal gradient amplitudes and gradient ramp rates help to reduce the impact of experimental artefacts caused by residual amplifier transients, eddy currents, or ferromagnetic hysteresis in components of the NMR magnet. The pulse sequence was validated with measurements of diffusion in water and of dispersion in flow through a packing of spheres. The analytical method introduced here permits the robust determination of the variance of non-Gaussian, dispersive displacement distributions. The noise sensitivity of the analytical method is shown to be negligible, using a demonstration experiment with a non-Gaussian longitudinal displacement distribution, measured on flow through a packing of mono-sized spheres.

  16. A carbon-free lithium-ion solid dispersion redox couple with low viscosity for redox flow batteries

    Science.gov (United States)

    Qi, Zhaoxiang; Koenig, Gary M.

    2016-08-01

    A new type of non-aqueous redox couple without carbon additives for flow batteries is proposed and the target anolyte chemistry is demonstrated. The so-called "Solid Dispersion Redox Couple" incorporates solid electroactive materials dispersed in organic lithium-ion battery electrolyte as its flowing suspension. In this work, a unique and systematic characterization approach has been used to study the flow battery redox couple in half cell demonstrations relative to a lithium electrode. An electrolyte laden with Li4Ti5O12 (LTO) has been characterized in multiple specially designed lithium half cell configurations. The flow battery redox couple described in this report has relatively low viscosity, especially in comparison to other flow batteries with solid active materials. The lack of carbon additive allows characterization of the electrochemical properties of the electroactive material in flow without the complication of conductive additives and unambiguous observation of the electrorheological coupling in these dispersed particle systems.

  17. Effect of Argon/Oxygen Flow Rate Ratios on DC Magnetron Sputtered Nano Crystalline Zirconium Titanate Thin Films

    Science.gov (United States)

    Rani, D. Jhansi; Kumar, A. GuruSampath; Sarmash, T. Sofi; Chandra Babu Naidu, K.; Maddaiah, M.; Rao, T. Subba

    2016-06-01

    High transmitting, non absorbent, nano crystalline zirconium titanate (ZT) thin films suitable for anti reflection coatings (ARC) were deposited on to glass substrates by direct current (DC) magnetron reactive sputtering technique, under distinct Argon to Oxygen (Ar/O2) gas flow rate ratios of 31/1, 30/2, 29/3 and 28/4, with a net gas flow (Ar + O2) of 32sccm, at an optimum substrate temperature of 250°C. The influence of the gas mixture ratio on the film properties has been investigated by employing x-ray diffraction (XRD), ultra violet visible (UV-vis) spectroscopy, atomic force microscopy (AFM), energy dispersive x-ray analysis (EDX) and four point probe methods. The films showed a predominant peak at 30.85° with (111) orientation. The crystallite size reduced from 22.94 nm to 13.5 nm and the surface roughness increased from 11.53 nm to 50.58 nm with increase in oxygen content respectively. The films deposited at 31/1 and 30/2 showed almost similar chemical composition. Increased oxygen content results an increase in electrical resistivity from 3.59 × 103 to 2.1 × 106 Ωm. The film deposited at Ar/O2 of 28/4 exhibited higher average optical transmittance of 91%, but its refractive index is higher than that of what is required for ARC. The films deposited at 31/1 and 30/2 of Ar/O2 possess higher transmittance (low absorbance) apart from suitable refractive index. Thus, these films are preferable candidates for ARC.

  18. The role of wind in the dispersal of floating seeds in slow-flowing or stagnant water bodies

    NARCIS (Netherlands)

    Sarneel, Judith M.|info:eu-repo/dai/nl/304836923; Beltman, Boudewijn|info:eu-repo/dai/nl/069582548; Buijze, Anneke; Groen, Roderick; Soons, Merel B.|info:eu-repo/dai/nl/255636792

    QuestionWhat is the role of wind in the dispersal of waterborne seeds in slow-flowing and stagnant water bodies at different temporal and spatial scales? (i) Is there a direct effect of wind on seed dispersal speed and distance? (ii) Are prevailing wind conditions reflected in the seed deposition

  19. Influence of oxygen flow rate on the structural, optical and electrical properties of ZnO films grown by DC magnetron sputtering

    Science.gov (United States)

    Gobbiner, Chaya Ravi; Ali Avanee Veedu, Muhammed; Kekuda, Dhananjaya

    2016-04-01

    Zinc oxide thin films were deposited on glass substrates at different oxygen flow rates by DC reactive magnetron sputtering. The oxygen flow rate was found to be one of the crucial parameters which influence structural, optical and electrical properties of grown films. The structural and optical characterization of the deposited films was carried out using X-ray diffraction and UV-visible spectroscopy, respectively. Swanepoel envelope and Drude-Lorentz (DL) models were applied to extract the optoelectronic parameters such as refractive index, dispersion energy and plasma frequency. Structurally, grain size was found to decrease with increase in oxygen flow rate during deposition. Moreover, all the films exhibited preferred (002) orientation confirming c-axis orientation of the films perpendicular to the substrate. For a particular range of oxygen flow rates, columnar growth was achieved. Marginal increase in the optical band gap from 3.14 to 3.22 eV was observed as the oxygen flow rate increased from 3 to 10 sccm. Calculated plasma frequency from the DL model was found to be in the infrared region. It has decreased as oxygen flow rate increased with the value from 1.625 × 1014 rad/s (862 cm-1) to 1.072 × 1014 rad/s (568 cm-1).

  20. Optimizing processes of dispersant concentration and post-treatments for fabricating single-walled carbon nanotube transparent conducting films

    Science.gov (United States)

    Gao, Jing; Wang, Wen-Yi; Chen, Li-Ting; Cui, Li-Jun; Hu, Xiao-Yan; Geng, Hong-Zhang

    2013-07-01

    This study evaluated the effect of sodium dodecyl benzene sulfonate (SDBS) as dispersant for the dispersion of purified single-walled carbon nanotubes (SWCNTs) in water in terms of dispersibility dependence on electrical conductivity of SWCNT transparent conducting film (TCF) performance. SWCNT TCFs were prepared by different proportions of CNTs/SDBS solution to find out the optimum SDBS concentration according to the film resistance of pristine and after post-treatment by nitric acid. TCFs fabricated with the aqueous solution by the ratio of CNTs/SDBS 1:5 gave the lowest sheet resistance and the highest transmittance. The TCFs were then further treated with thionyl chloride to improve their conductivity. Low sheet resistance (86 Ω/□, 80%T) was achieved. The dispersion condition of CNTs/SDBS aqueous solution was characterized by field-emission scanning electron microscopy, while the X-ray photoelectron spectroscopy and Raman spectroscopy confirmed the dispersion and doping mechanism treated with nitric acid and thionyl chloride.

  1. Dispersion enhancement and damping by buoyancy driven flows in 2D networks of capillaries

    CERN Document Server

    D'Angelo, Maria Veronica; Allain, Catherine; Rosen, Marta; Hulin, Jean-Pierre

    2008-01-01

    The influence of a small relative density difference on the displacement of two miscible liquids is studied experimentally in transparent 2D networks of micro channels. Both stable displacements in which the denser fluid enters at the bottom of the cell and displaces the lighter one and unstable displacements in which the lighter fluid is injected at the bottom and displaces the denser one are realized. Except at the lowest mean flow velocity U, the average $C(x,t)$ of the relative concentration satisfies a convection-dispersion equation. The dispersion coefficient is studied as function of the relative magnitude of fluid velocity and of the velocity of buoyancy driven fluid motion. A model is suggested and its applicability to previous results obtained in 3D media is discussed.

  2. CVFEM for Multiphase Flow with Disperse and Interface Tracking, and Algorithms Performances

    Directory of Open Access Journals (Sweden)

    M. Milanez

    2015-12-01

    Full Text Available A Control-Volume Finite-Element Method (CVFEM is newly formulated within Eulerian and spatial averaging frameworks for effective simulation of disperse transport, deposit distribution and interface tracking. Their algorithms are implemented alongside an existing continuous phase algorithm. Flow terms are newly implemented for a control volume (CV fixed in a space, and the CVs' equations are assembled based on a finite element method (FEM. Upon impacting stationary and moving boundaries, the disperse phase changes its phase and the solver triggers identification of CVs with excess deposit and their neighboring CVs for its accommodation in front of an interface. The solver then updates boundary conditions on the moving interface as well as domain conditions on the accumulating deposit. Corroboration of the algorithms' performances is conducted on illustrative simulations with novel and existing Eulerian and Lagrangian solutions, such as (- other, i. e. external methods with analytical and physical experimental formulations, and (- characteristics internal to CVFEM.

  3. Asymmetric coupling and dispersion of surface-plasmon-polariton waves on a periodically patterned anisotropic metal film

    CERN Document Server

    Dutta, Jhuma; Lakhtakia, Akhlesh

    2014-01-01

    The morphology of a columnar thin film (CTF) of silver renders it an effectively biaxially anisotropic continuum. CTFs of silver deposited on one-dimensional gratings of photoresist showed strong blazing action and asymmetrically coupled optical radiation to surface plasmon-polariton (SPP) waves propagating only along one direction supported by either the CTF/photoresist or the CTF/air interfaces. Homogenization of the CTFs using the Bruggeman formalism revealed them to display hyperbolic dispersion, and the dispersion of SPP waves was adequately described thereby.

  4. Asymmetric coupling and dispersion of surface-plasmon-polariton waves on a periodically patterned anisotropic metal film

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Jhuma; Ramakrishna, S. Anantha [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Lakhtakia, Akhlesh, E-mail: akhlesh@psu.edu [Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2015-01-07

    The morphology of a columnar thin film (CTF) of silver renders it an effectively biaxially anisotropic continuum. CTFs of silver deposited on one-dimensional gratings of photoresist showed strong blazing action and asymmetrically coupled optical radiation to surface-plasmon-polariton (SPP) waves propagating only along one direction supported by either the CTF/photoresist or the CTF/air interfaces. Homogenization of the CTFs using the Bruggeman formalism revealed them to display hyperbolic dispersion, and the dispersion of SPP waves was adequately described thereby.

  5. Equilibrium-eulerian les model for turbulent poly-dispersed particle-laden flow

    KAUST Repository

    Icardi, Matteo

    2013-04-01

    An efficient Eulerian method for poly-dispersed particles in turbulent flows is implemented, verified and validated for a channel flow. The approach couples a mixture model with a quadrature-based moment method for the particle size distribution in a LES framework, augmented by an approximate deconvolution method to reconstructs the unfiltered velocity. The particle velocity conditioned on particle size is calculated with an equilibrium model, valid for low Stokes numbers. A population balance equation is solved with the direct quadrature method of moments, that efficiently represents the continuous particle size distribution. In this first study particulate processes are not considered and the capability of the model to properly describe particle transport is investigated for a turbulent channel flow. First, single-phase LES are validated through comparison with DNS. Then predictions for the two-phase system, with particles characterised by Stokes numbers ranging from 0.2 to 5, are compared with Lagrangian DNS in terms of particle velocity and accumulation at the walls. Since this phenomenon (turbophoresis) is driven by turbulent fluctuations and depends strongly on the particle Stokes number, the approximation of the particle size distribution, the choice of the sub-grid scale model and the use of an approximate deconvolution method are important to obtain good results. Our method can be considered as a fast and efficient alternative to classical Lagrangian methods or Eulerian multi-fluid models in which poly-dispersity is usually neglected.

  6. Population genetic structure, gene flow and sex-biased dispersal in frillneck lizards (Chlamydosaurus kingii).

    Science.gov (United States)

    Ujvari, Beata; Dowton, Mark; Madsen, Thomas

    2008-08-01

    By using both mitochondrial and nuclear multiloci markers, we explored population genetic structure, gene flow and sex-specific dispersal of frillneck lizards (Chlamydosaurus kingii) sampled at three locations, separated by 10 to 50 km, in a homogenous savannah woodland in tropical Australia. Apart from a recombinant lizard, the mitochondrial analyses revealed two nonoverlapping haplotypes/populations, while the nuclear markers showed that the frillneck lizards represented three separate clusters/populations. Due to the small population size of the mtDNA, fixation may occur via founder effects and/or drift. We therefore suggest that either of these two processes, or a combination of the two, are the most likely causes of the discordant results obtained from the mitochondrial and the nuclear markers. In contrast to the nonoverlapping mitochondrial haplotypes, in 12 out of 74 lizards, mixed nuclear genotypes were observed, hence revealing a limited nuclear gene flow. Although gene flow should ultimately result in a blending of the populations, we propose that the distinct nuclear population structure is maintained by frequent fires resulting in local bottlenecks, and concomitant spatial separation of the frillneck lizard populations. Limited mark-recapture data and the difference in distribution of the mitochondrial and nuclear markers suggest that the mixed nuclear genotypes were caused by juvenile male-biased dispersal.

  7. Investigation of nonionic diazo dye-doped polymer dispersed liquid crystal film

    Indian Academy of Sciences (India)

    Farzana Ahmad; Muhammad Jamil; Young Jae Jeon; Lee Jin Woo; Jae Eun Jung; Jae Eun Jang

    2012-04-01

    Sudan black B (SBB) was used to investigate as the nonionic diazo dye-doped in polymer dispersed liquid crystal (PDLC) display, by polymerization-induced phase separation (PIPS) method. The maximum absorbance, contrast ratio, dichroic ratio and the order parameter of nonionic diazo dye in nemetic host (TL203) were investigated using UV–Vis polarized spectroscopy. The orientation of the dye molecules was controlled by electric field, which enabled the contrast ratio of the dye to be obtained by electrically switching. The change occurring on droplet morphologies and electro-optical properties of PDLC film with the change in contents of Sudan black dye and liquid crystals (LC) contents was investigated. We found an increase in LC droplet sizes with the increase of diazo dye and LC contents. Moreover the addition of small amount of nonionic diazo dye reduced the threshold voltage (Vth), increased off-state transmittance, enhanced the contrast ratio and decreased the response time of dye-doped PDLC. Additionally the change in transition temperature of LC and changes in LC droplet morphologies with the addition of dye were also observed. Such changes were observed with the images taken by polarized optical microscope (POM). The detail discussions on such behaviours were also made.

  8. High flux pinning efficiency by columnar defects dispersed in three directions in YBCO thin films

    Science.gov (United States)

    Sueyoshi, Tetsuro; Nishimura, Takahiro; Fujiyoshi, Takanori; Mitsugi, Fumiaki; Ikegami, Tomoaki; Ishikawa, Norito

    2016-10-01

    A systematic investigation of flux pinning by widely direction-dispersed columnar defects (CDs) in YBa2Cu3O y thin films was carried out by using heavy-ion irradiation: a parallel configuration of CDs aligned along the c-axis, and two trimodal splay configurations composed of CDs crossing at 0° and ± 45° relative to the c-axis, where the splay plane defined by the three irradiation angles is perpendicular (trimodal-A) or parallel (trimodal-B) to the transport current direction. The trimodal configurations show high pinning efficiency over a wide range of magnetic field orientations compared to the parallel one at low magnetic field. In particular, trimodal-B shows the higher critical current density of the two trimodal configurations. The crossed CDs at ± 45° in the trimodal configurations provide uncorrelated flux pinning at B || c due to the large tilting angle off the c-axis, which effectively reinforce the flux pinning of CDs parallel to the c-axis. This assist effect is more remarkable for trimodal-B: a kink sliding motion of flux lines along the CDs is more effectively reduced by the splay plane, not only at B || c but also at inclined magnetic fields off the c-axis.

  9. Paraffin dispersant application for cleaning subsea flow lines in the deep water Gulf of Mexico cottonwood development

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, David; White, Jake; Pogoson, Oje [Baker Hughes Inc., Houston, TX (United States); Barros, Dalmo; Ramachandran, Kartik; Bonin, George; Waltrich, Paulo; Shecaira, Farid [PETROBRAS America, Houston, TX (United States); Ziglio, Claudio [Petroleo Brasileiro S.A. (CENPES/PETROBRAS), Rio de Janeiro, RJ (Brazil). Centro de Pesquisa e Desenvolvimento

    2012-07-01

    This paper discusses a paraffin dispersant (in seawater) application to clean paraffin deposition from a severely restricted 17.4-mile dual subsea flow line system in the Gulf of Mexico Cottonwood development. In principle, dispersant treatments are simple processes requiring effective dispersant packages and agitation to break-up and disperse deposition. Dispersants have been used onshore for treating wax deposition for decades. Implementation of a treatment in a long deep water production system, however, poses numerous challenges. The Cottonwood application was one of the first ever deep water dispersant applications. The application was designed in four separate phases: pre-treatment displacement for hydrate protection, dispersant treatment for paraffin deposition removal, pigging sequence for final flow line cleaning, and post-treatment displacement for hydrate protection. In addition, considerable job planning was performed to ensure the application was executed in a safe and environmentally responsible manner. Two dynamically positioned marine vessels were used for pumping fluids and capturing returns. The application was extremely successful in restoring the deep water flow lines back to near pre-production state. Final pigging operations confirmed the flow lines were cleaned of all restrictions. Significant paraffin deposition was removed in the application. Approximately 900 bbls of paraffin sludge was recovered from the 4000 bbl internal volume flow line loop. Furthermore, the application was completed with zero discharge of fluids. The application provided significant value for the Cottonwood development. It allowed production from wells to be brought on-line at a higher capacity, thereby generating increased revenue. It also allowed resumption of routine pigging operations. As such, the Cottonwood dispersant application illustrates that with proper planning and execution, paraffin dispersant treatments can be highly effective solutions for cleaning

  10. Modeling flow around bluff bodies and predicting urban dispersion using large eddy simulation.

    Science.gov (United States)

    Tseng, Yu-Heng; Meneveau, Charles; Parlange, Marc B

    2006-04-15

    Modeling air pollutant transport and dispersion in urban environments is especially challenging due to complex ground topography. In this study, we describe a large eddy simulation (LES) tool including a new dynamic subgrid closure and boundary treatment to model urban dispersion problems. The numerical model is developed, validated, and extended to a realistic urban layout. In such applications fairly coarse grids must be used in which each building can be represented using relatively few grid-points only. By carrying out LES of flow around a square cylinder and of flow over surface-mounted cubes, the coarsest resolution required to resolve the bluff body's cross section while still producing meaningful results is established. Specifically, we perform grid refinement studies showing that at least 6-8 grid points across the bluff body are required for reasonable results. The performance of several subgrid models is also compared. Although effects of the subgrid models on the mean flow are found to be small, dynamic Lagrangian models give a physically more realistic subgrid-scale (SGS) viscosity field. When scale-dependence is taken into consideration, these models lead to more realistic resolved fluctuating velocities and spectra. These results set the minimum grid resolution and subgrid model requirements needed to apply LES in simulations of neutral atmospheric boundary layer flow and scalar transport over a realistic urban geometry. The results also illustrate the advantages of LES over traditional modeling approaches, particularly its ability to take into account the complex boundary details and the unsteady nature of atmospheric boundary layer flow. Thus LES can be used to evaluate probabilities of extreme events (such as probabilities of exceeding threshold pollutant concentrations). Some comments about computer resources required for LES are also included.

  11. Determining the refractive index dispersion and thickness of hot-pressed chalcogenide thin films from an improved Swanepoel method

    DEFF Research Database (Denmark)

    Fang, Y. Z.; Jayasuriya, D.; Furniss, David

    2017-01-01

    The well-known method presented by Swanepoel can be used to determine the refractive index dispersion of thin films in the near-infrared region from wavelength values at maxima and minima, only, of the transmission interference fringes. In order to extend this method into the mid-infrared spectral...... by a hot-pressing technique. The refractive index dispersion of the chalcogenide thin films is determined by the improved method with a standard deviation of less than 0.0027. The accuracy of the method is shown to be better than 0.4% at a wavelength of 3.1 µm by comparison with a benchmark refractive...... index value obtained from prism measurements on Ge16As24Se15.5Te44.5 material taken from the same batch....

  12. Dispersive Stabilization of Liquid Crystal-in-Water with Acrylamide Copolymer/Surfactant Mixture: Nematic Curvilinear Aligned Phase Composite Film.

    Science.gov (United States)

    Park; Lee

    1999-11-01

    The effect of nonionic surfactant, (H(OCH(2)-CH(2))(8)-OC(6)H(4)-C(9)H(19)), on the dispersion stabilization of liquid crystal (LC)-in-water with acrylamide copolymer containing the related nonylphenyl groups was studied. It was observed that the addition of nonionic surfactant increases the stability of LC dispersions and improves the electrooptical properties of the nematic curvilinear aligned phase (NCAP) composite film. On the basis of the surface tension, reduced viscosity, cloud point, and coalescence time measurements, it was proposed that formation of an integrated structure induced by interactions between hydrophobic groups in the polymer chains is probably important to fabrication of a polymer composite film made of LC and polymer matrix. Copyright 1999 Academic Press.

  13. Effect of particle inertia on fluid turbulence in gas-solid disperse flow

    Science.gov (United States)

    Mito, Yoichi

    2016-11-01

    The effect of particle inertia on the fluid turbulence in gas-solid disperse flow through a vertical channel has been examined by using a direct numerical simulation, to calculate the gas velocities seen by the particles, and a simplified non-stationary flow model, in which a uniform distribution of solid spheres of density ratio of 1000 are added into the fully-developed turbulent gas flow in an infinitely wide channel. The gas flow is driven downward with a constant pressure gradient. The frictional Reynolds number defined with the frictional velocity before the addition of particles, v0*, is 150. The feedback forces are calculated using a point force method. Particle diameters of 0.95, 1.3 and 1.9, which are made dimensionless with v0* and the kinematic viscosity, and volume fractions, ranging from 1 ×10-4 to 2 ×10-3 , in addition to the one-way coupling cases, are considered. Gravitational effect is not clearly seen where the fluid turbulence is damped by feedback effect. Gas flow rate increases with the decrease in particle inertia, that causes the increase in feedback force. Fluid turbulence decreases with the increase in particle inertia, that causes the increase in diffusivity of feedback force and of fluid turbulence. This work was supported by JSPS KAKENHI Grant Number 26420097.

  14. Implications of Small-Scale Flow Features to Modeling Dispersion over Complex Terrain.

    Science.gov (United States)

    Banta, R. M.; Olivier, L. D.; Gudiksen, P. H.; Lange, R.

    1996-03-01

    Small-scale, topographically forced wind systems often have a strong influence on flow over complex terrain. A problem is that these systems are very difficult to measure, because of their limited spatial and temporal extent. They can be important, however, in the atmospheric transport of hazardous materials. For example, a nocturnal exit jet-a narrow stream of cold air-which flowed from Eldorado Canyon at the interface between the Rocky Mountains and the Colorado plains near the Rocky Flats Plant (RFP), swept over RFP for about 3 h in the middle of the night of 4 5 February 1991. It extended in depth from a few tens of meters to approximately 800 m above the ground. Because the jet was so narrow (2 km wide), it was poorly sampled by the meteorological surface mesonet, but it did prove to have an effect on the dispersion of tracer material released from RFP, producing a secondary peak in measured concentration to the southeast of RFP. The existence and behavior of the jet was documented by Environment Technology Laboratoy's Doppler lidar system, a scanning, active remote-sensing system that provides fine-resolution wind measurements. The lidar was deployed as a part of a wintertime study of flow and dispersion in the RFP vicinity during February 1993.The MATHEW-ADPIC atmospheric dispersion model was run using the case study data from this night. It consists of three major modules: an interpolation scheme; MATHEW, a diagnostic wind-flow algorithm that calculates a mass-consistent interpolated flow; and ADPIC, a diffusion algorithm. The model did an adequate job of representing the main lobe of the tracer transport, but the secondary lobe resulting from the Eldorado Canyon exit jet was absent from the model result. Because the jet was not adequately represented in the input data, it did not appear in the modeled wind field. Thus, the effects of the jet on the transport of tracer material were not properly simulated by the diagnostic model.

  15. Pore-scale simulation of fluid flow and solute dispersion in three-dimensional porous media

    KAUST Repository

    Icardi, Matteo

    2014-07-31

    In the present work fluid flow and solute transport through porous media are described by solving the governing equations at the pore scale with finite-volume discretization. Instead of solving the simplified Stokes equation (very often employed in this context) the full Navier-Stokes equation is used here. The realistic three-dimensional porous medium is created in this work by packing together, with standard ballistic physics, irregular and polydisperse objects. Emphasis is placed on numerical issues related to mesh generation and spatial discretization, which play an important role in determining the final accuracy of the finite-volume scheme and are often overlooked. The simulations performed are then analyzed in terms of velocity distributions and dispersion rates in a wider range of operating conditions, when compared with other works carried out by solving the Stokes equation. Results show that dispersion within the analyzed porous medium is adequately described by classical power laws obtained by analytic homogenization. Eventually the validity of Fickian diffusion to treat dispersion in porous media is also assessed. © 2014 American Physical Society.

  16. On the dissipation and dispersion of entropy waves in heat transferring channel flows

    Science.gov (United States)

    Fattahi, A.; Hosseinalipour, S. M.; Karimi, N.

    2017-08-01

    This paper investigates the hydrodynamic and heat transfer effects on the dissipation and dispersion of entropy waves in non-reactive flows. These waves, as advected density inhomogeneities downstream of unsteady flames, may decay partially or totally before reaching the exit nozzle, where they are converted into sound. Attenuation of entropy waves dominates the significance of the subsequent acoustic noise generation. Yet, the extent of this decay process is currently a matter of contention and the pertinent mechanisms are still largely unexplored. To resolve this issue, a numerical study is carried out by compressible large eddy simulation of the wave advection in a channel subject to convective and adiabatic thermal boundary conditions. The dispersion, dissipation, and spatial correlation of the wave are evaluated by post-processing of the numerical results. This includes application of the classical coherence function as well as development of nonlinear quantitative measures of wave dissipation and dispersion. The analyses reveal that the high frequency components of the entropy wave are always strongly damped. The survival of the low frequency components heavily depends on the turbulence intensity and thermal boundary conditions of the channel. In general, high turbulence intensities and particularly heat transfer intensify the decay and destruction of the spatial coherence of entropy waves. In some cases, they can even result in the complete annihilation of the wave. The current work can therefore resolve the controversies arising over the previous studies of entropy waves with different thermal boundary conditions.

  17. Effects of oxygen partial pressure and annealing on dispersive optical nonlinearity in NiO thin films

    Science.gov (United States)

    Chouhan, Romita; Baraskar, Priyanka; Agrawal, Arpana; Gupta, Mukul; Sen, Pranay K.; Sen, Pratima

    2017-07-01

    We report annealing induced sign reversal of dispersive optical nonlinearity in ion beam sputtered NiO thin films deposited at 30% and 70% oxygen partial pressures. In the Ultraviolet-visible spectra of the samples, the transmission peak corresponding to d-d transitions is observed near 2 eV. A shift in this peak towards higher energy was observed when the same films were annealed at 523 K. The near resonant photoinduced transitions produced giant nonlinear optical susceptibilities of both third- and fifth- orders when the annealed film was irradiated by a continuous wave 632.8 nm He-Ne laser. The role of the thermo-optic effect has been examined critically. Experimental studies further reveal that the oxygen partial pressure influences the growth direction of the grains in the thin films. The well known Z-scan experimental procedure has been followed for measurements of optical nonlinearities in all the NiO films. The nonlinear refractive indices of both the as-deposited and annealed NiO thin films are defined in terms of the thermo-optic coefficients (d/nd T ) T =T0 and (d/2nd T2 ) T =T0 .

  18. Effect of a Polymercaptan Material on the Electro-Optical Properties of Polymer-Dispersed Liquid Crystal Films

    Directory of Open Access Journals (Sweden)

    Yujian Sun

    2016-12-01

    Full Text Available Polymer-dispersed liquid crystal (PDLC films were prepared by the ultraviolet-light-induced polymerization of photopolymerizable monomers in nematic liquid crystal/chiral dopant/thiol-acrylate reaction monomer composites. The effects of the chiral dopant and crosslinking agents on the electro-optical properties of the PDLC films were systematically investigate. While added the chiral dopant S811 into the PDLC films, the initial off-state transmittance of the films was decreased. It was found that the weight ratio among acrylate monomers, thiol monomer PETMP and the polymercaptan Capcure 3-800 showed great influence on the properties of the fabricated PDLC films because of the existence of competition between thiol-acrylate reaction and acrylate monomer polymerization reaction. While adding polymercaptans curing agent Capcure 3-800 with appropriate concentration into the PDLC system, lower driven voltage and higher contrast ratio were achieved. This made the polymer network and electro-optical properties of the PDLC films easily tunable by the introduction of the thiol monomers.

  19. Relationship between Supplied Oil Flow Rates and Oil Film Thicknesses under Starved Elastohydrodynamic Lubrication

    Directory of Open Access Journals (Sweden)

    Taisuke Maruyama

    2015-04-01

    Full Text Available Many studies have already considered starved lubrication. However, there have been no reports on the oil film thicknesses under steady starved EHL (elastohydrodynamic lubrication, where the ultra-low volume of oil supplied per unit time is uniform. The present study examined the relationship between the supplied oil flow rate and oil film thickness under steady starved lubrication. A ball-on-disk testing machine was used in experiments to measure the oil film thickness by means of optical interferometry. A microsyringe pump was used to accurately control the supplied oil flow rate. The supplied oil flow rate was kept constant, and the minimum oil film thickness was measured for 1 h after the start of the tests to determine the relationship between the supplied oil flow rate and oil film thickness.

  20. Improvement of Dispersion and Color Effect of Organic Pigments in Polymeric Films via Microencapsulation by the Miniemulsion Technique

    Directory of Open Access Journals (Sweden)

    Dongming Qi

    2013-01-01

    Full Text Available Three primary pigment/poly(n-butyl acrylate-co-styrene (P(BA+St nanocomposites were prepared via encapsulation of the corresponding organic pigments via the miniemulsion technique. The resulting latexes of the P(BA+St/pigment nanocomposites were filmed in a PTFE mould or printed onto cotton fabric. The morphology of the P(BA+St/pigment nanocomposites and the dispersion of pigment particles in the latex film and on the printed fabric surface, as well as the adhesion between pigment and adhesive film, were evaluated by transmission electron microscopy (TEM, field emission scanning electron microscopy (FESEM, 3D digital microscope system (3D-POM, and printing results tests. Attributing to the preprotection of adhesive polymer shell, the self-adhesive P(BA+St/pigment nanocomposites were homogeneously and firmly dispersed both in the thin latex film and in the adhesive layer on the fiber surface. As a result, the color strength, color fastness, and handle of the fabrics printed by the P(BA+St/pigment nanocomposites latex were significantly improved, compared to the fabrics printed by the conventional pigment blended latex.

  1. Universal dispersion model for characterization of optical thin films over a wide spectral range: application to hafnia.

    Science.gov (United States)

    Franta, Daniel; Nečas, David; Ohlídal, Ivan

    2015-11-01

    A dispersion model capable of expressing the dielectric response of a broad class of optical materials in a wide spectral range from far IR to vacuum UV is described in detail. The application of this universal dispersion model to a specific material is demonstrated using the ellipsometric and spectrophotometric characterization of a hafnia film prepared by vacuum evaporation on silicon substrate. The characterization utilizes simultaneous processing of data from multiple techniques and instruments covering the wide spectral range and includes the characterization of roughness, nonuniformity, transition layer, and native oxide layer on the back of the substrate. It is shown how the combination of measurements in light reflected from both sides of the sample and transmitted light allows the separation of weak absorption in films and substrates. This approach is particularly useful in the IR region where the absorption structures in films and substrates often overlap and a prior measurement of the bare substrate may be otherwise necessary for precise separation. Individual phenomena that contribute to the dielectric response, i.e., interband electronic transitions, electronic excitations involving the localized states, and phonon absorption, are discussed in detail. A quantitative analysis of absorption on localized states, permitting the separation of transitions between localized states from transitions between localized and extended states, is utilized to obtain estimates of the density of localized states and film stoichiometry.

  2. PREPARATION OF POLYIMIDE-BaTiO3 HYBRID FILMS BY A DISPERSION PROCESS AND THEIR MICROSTRUCTURE

    Institute of Scientific and Technical Information of China (English)

    Yue-sheng Li; Yue-jin Tong; Kai Jing; Meng-xian Ding

    2001-01-01

    Barium titanate (BaTiO3) powders with particle sizes of 30~50 nm were prepared from barium stearate, titanium alkoxides and stearic acid by stearic acid-gel method. Dispersing the agglomerate of BaTiO3 nanoparticles into poly(amic acid) solution followed by curing led to the formation of polyimide hybrid films. The hybrid films were transparent and well distributed with BaTiO3 nanoparticles when the BaTiO3 content was less than 1 wt%. Highly loaded hybrid film containing 30 wt % BaTiO3 was tough, had a smooth surface and possessed much higher dielectric and piezoelectric constants than the parent polyimide.

  3. Theory and Simulation of Cholesteric Film Formation Flows of Dilute Collagen Solutions.

    Science.gov (United States)

    Aguilar Gutierrez, O F; Rey, Alejandro D

    2016-11-15

    Dilute isotropic collagen solutions are usually flow processed into monodomain chiral nematic thin films for obtaining highly ordered materials by a multistep process that starts with complex inhomogeneous flow kinematics. Here we present rigorous theory and simulation of the initial precursors during flow steps in cholesteric collagen film formation. We first extract the molecular shape parameter and rotational diffusivity from previously reported simple shear data of dilute collagen solutions, where the former leads the reactive parameter (tumbling function) which determines the net effect of vorticity and strain rate on the average orientation and where the latter establishes the intensity of strain required for flow-birefringence, both crucial quantities for controlled film formation flow. We find that the tumbling function is similar to those of rod-like lyotropic liquid crystalline polymers and hence it is predicted that they would tumble in the ordered high concentration state leading to flow-induced texturing. The previously reported experimental data is well fitted with rotational diffusivities whose order of magnitude is consistent to those of other biomacromolecules. We then investigate the response of the tensor order parameter to complex flow kinematics, ranging from pure vorticity, through simple shear, to extensional flow, as may arise in typical flow casting and film flows. The chosen control variable to produce precursor cholesteric films is the director or average orientation, since the nematic order is set close to typical values found in concentrated cholesteric type I collagen solutions. Using the efficient four-roll mill kinematics, we summarize the para-nematic structure-flow process diagram in terms of the director orientation and flow type. Using analysis and computation, we provide a parametric envelope that is necessary to eventually produce well-aligned cholesteric films. We conclude that extensional flow is an essential ingredient of

  4. Large eddy simulations of turbulent flows on graphics processing units: Application to film-cooling flows

    Science.gov (United States)

    Shinn, Aaron F.

    Computational Fluid Dynamics (CFD) simulations can be very computationally expensive, especially for Large Eddy Simulations (LES) and Direct Numerical Simulations (DNS) of turbulent ows. In LES the large, energy containing eddies are resolved by the computational mesh, but the smaller (sub-grid) scales are modeled. In DNS, all scales of turbulence are resolved, including the smallest dissipative (Kolmogorov) scales. Clusters of CPUs have been the standard approach for such simulations, but an emerging approach is the use of Graphics Processing Units (GPUs), which deliver impressive computing performance compared to CPUs. Recently there has been great interest in the scientific computing community to use GPUs for general-purpose computation (such as the numerical solution of PDEs) rather than graphics rendering. To explore the use of GPUs for CFD simulations, an incompressible Navier-Stokes solver was developed for a GPU. This solver is capable of simulating unsteady laminar flows or performing a LES or DNS of turbulent ows. The Navier-Stokes equations are solved via a fractional-step method and are spatially discretized using the finite volume method on a Cartesian mesh. An immersed boundary method based on a ghost cell treatment was developed to handle flow past complex geometries. The implementation of these numerical methods had to suit the architecture of the GPU, which is designed for massive multithreading. The details of this implementation will be described, along with strategies for performance optimization. Validation of the GPU-based solver was performed for fundamental bench-mark problems, and a performance assessment indicated that the solver was over an order-of-magnitude faster compared to a CPU. The GPU-based Navier-Stokes solver was used to study film-cooling flows via Large Eddy Simulation. In modern gas turbine engines, the film-cooling method is used to protect turbine blades from hot combustion gases. Therefore, understanding the physics of

  5. Film Flow Dominated Simultaneous Flow of Two Viscous Incompressible Fluids Through a Porous Medium

    Directory of Open Access Journals (Sweden)

    Olav eAursjø

    2014-11-01

    Full Text Available We present an experimental study of two-phase flow in a quasi-two-dimensional porous medium. The two phases, a water-glycerol solution and a commercial food grade rapeseed/canola oil, having an oil to water-glycerol viscosity ratio of 1.3, are injected simultaneously into a Hele-Shaw cell with a mono-layer of randomly distributed glass beads. The two liquids are injected into the model from alternating point inlets. Initially, the porous model is filled with the water-glycerol solution. We observe that after an initial transient state, an overall static cluster configuration is obtained. While the oil is found to create a connected system spanning cluster, a large part of the water-glycerol clusters left behind the initial invasion front is observed to remain immobile throughout the rest of the experiment. This could suggest that the water-glycerol flow-dynamics is largely dominated by film flow. The flow pathways are thus given through the dynamics of the initial invasion. This behavior is quite different from that observed in systems with large viscosity differences between the two fluids, and where compressibility plays an important part of the process.

  6. Marangoni effect of cracked liquid film of an aqueous electrolyte flowing over a vertical heated plate

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An experimental investigation was performed on Marangoni effect of cracked liquid film of aqueous Na2SO4 flowing over a vertical heated plate by using a sensitive infrared imaging technique. The results show that the thermal and solutal Marangoni effects, which result from the non-uniform distributions of surface temperature and concentration of the film, respectively, occur in the streamwise and transverse directions of the film, generating different influences on the film heat transfer. Taking account of the Marangoni number (Ma) and the solution concentration (c0), a correlation of the Nusselt number (Nu) for the cracked liquid film is proposed.

  7. A comparison of Flow and Kodak dental X-ray films by means of perceptibility curves

    Energy Technology Data Exchange (ETDEWEB)

    Svenson, B.; Petersson, A. (Centre of Oral Health Sciences, Univ. of Lund, Malmoe (Sweden))

    1993-01-01

    Flow D- and E-speed group dental X-ray films (DX-58 and EX-58) have recently been introduced to the market. By means of perceptibility curves these films were compared with commonly used dental X-ray films (Kodak Ultraspeed and Ektaspeed). No major differences between the films were found with regard to contrast and the subjectively assessed number of small contrast differences. The exposure for EX-58 had to be lowered by 66% and Ektaspeed by 39% compared with Ultraspeed film to obtain the same density. DX-58 and Ultraspeed were of the same sensitivity. 26 refs., 3 figs., 3 tabs.

  8. Assessment of particle-tracking models for dispersed particle-laden flows implemented in OpenFOAM and ANSYS FLUENT

    Directory of Open Access Journals (Sweden)

    Franziska Greifzu

    2016-01-01

    Full Text Available In the present study two benchmark problems for turbulent dispersed particle-laden flow are investigated with computational fluid dynamics (CFD. How the CFD programs OpenFOAM and ANSYS FLUENT model these flows is tested and compared. The numerical results obtained with Lagrangian–Eulerian (LE point-particle (PP models for Reynolds-averaged Navier–Stokes (RANS simulations of the fluid flow in steady state and transient modes are compared with the experimental data available in the literature. The effect of the dispersion model on the particle motion is investigated in particular, as well as the order of coupling between the continuous carrier phase and the dispersed phase. First, a backward-facing step (BFS case is validated. As a second case, the confined bluff body (CBB is used. The simulated fluid flows correspond well with the experimental data for both test cases. The results for the dispersed solid phase reveal a good accordance between the simulation results and the experiments. It seems that particle dispersion is slightly under-predicted when ANSYS FLUENT is used, whereas the applied solver in OpenFOAM overestimates the dispersion somewhat. Only minor differences between the coupling schemes are detected due to the low volume fractions and mass loadings that are investigated. In the BFS test case the importance of the spatial dimension of the numerical model is demonstrated. Even if it is reasonable to assume a two-dimensional fluid flow structure, it is crucial to simulate the turbulent particle-laden flow with a three-dimensional model since the turbulent dispersion of the particles is three-dimensional.

  9. Effect of Fatty acids and beeswax addition on properties of sodium caseinate dispersions and films.

    Science.gov (United States)

    Fabra, M J; Jiménez, A; Atarés, L; Talens, P; Chiralt, A

    2009-06-08

    Edible films based on sodium caseinate and different saturated fatty acids, oleic acid, or beeswax were formulated. Film-forming emulsions were characterized in terms of particle size distribution, rheological behavior and surface tension. In order to evaluate the influence of lipids on sodium caseinate matrices, mechanical, optical, and water vapor barrier properties were studied, taking into account the effect of water content and film structure on such properties. Saturated fatty acids affected the film properties in a particular way due to the formation of bilayer structures which limited water vapor permeability, giving rise to nonflexible and more opaque films. Oleic acid and beeswax were less effective as water vapor barriers, although the former imparted more flexibility to the caseinate films and did not reduce the film transparency notably.

  10. High Luminescence White LEDs Prepared with 2D Island-Pattern of Quantum Dots Dispersed Photopolymer Films

    Directory of Open Access Journals (Sweden)

    Hyun-Guk Hong

    2015-01-01

    Full Text Available Since the reabsorption loss among different size quantum dots (QDs is a critical issue in the QD based white LEDs, we proposed and fabricated new film structure of 2D island-patterns consisting of separate green and red QDs dispersed photopolymer patterns in a zigzag form. A small air-gap such as 60 μm between QD islands helps to control the optical path at the interface to reduce the lateral reabsorption loss to enhance the optical efficiency of white LED. The 2D island-patterns of QD phosphor film were fabricated using a UV imprinting process and compared the optical efficiency with the other QD film structure prepared with same QD concentrations and thicknesses such as a mixed and separately layered QD structure. Experimental and simulation analysis were performed to confirm the better optical efficiency from the 2D island-patterns of QD films due to the reduced reabsorption loss. High luminescence white LED was finally realized with 2D island-patterns of QD film, resulting in a luminous efficiency of 62.2 lm/W and CRI of 83 with CCT of 4537 K at the operation current of 60 mA.

  11. Determination and analysis of dispersive optical constants of CuIn{sub 3}S{sub 5} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Khemiri, N., E-mail: naoufel_khemiri@yahoo.f [Laboratoire de Photovoltaique et Materiaux Semiconducteurs-ENIT, Universite Tunis, ElManar BP 37, Le belvedere, 1002 Tunis (Tunisia); Sinaoui, A.; Kanzari, M. [Laboratoire de Photovoltaique et Materiaux Semiconducteurs-ENIT, Universite Tunis, ElManar BP 37, Le belvedere, 1002 Tunis (Tunisia)

    2011-04-15

    CuIn{sub 3}S{sub 5} thin films were prepared from powder by thermal evaporation under vacuum (10{sup -6} mbar) onto glass substrates. The glass substrates were heated from 30 to 200 {sup o}C. The films were characterized for their optical properties using optical measurement techniques (transmittance and reflectance). We have determined the energy and nature of the optical transitions of films. The optical constants of the deposited films were determined in the spectral range 300-1800 nm from the analysis of transmission and reflection data. The Swanepoel envelope method was employed on the interference fringes of transmittance patterns for the determination of variation of refractive index with wavelength. Wemple-Di Domenico single oscillator model was applied to determine the optical constants such as oscillator energy E{sub 0} and dispersion energy E{sub d} of the films deposited at different substrate temperatures. The electric free carrier susceptibility and the ratio of the carrier concentration to the effective mass were estimated according to the model of Spitzer and Fan.

  12. Effect of different dispersing additives on the morphology and the properties of polyethylene-based nanocomposite films

    Directory of Open Access Journals (Sweden)

    2011-10-01

    Full Text Available In this work, the use of a polar wax, e.g. amphiphilic Tegomer® E 525 (TEG is investigated with the aim of modifying, and possibly improving, the dispersion of an organically modified nanoclay (OMMT, loaded at 5 wt%, in a polyethylene matrix (PE at relatively low loading levels. We have indeed found that the incorporation of low loadings, e.g. 0.5 wt%, of TEG, an amphiphilic block co-polymer, into a PE/OMMT sample results in a substantial improvement of the clay dispersion in the nanocomposite and, consequently, of the mechanical and thermomechanical properties of the films. The achieved results are comparable to those obtained for systems containing traditional dispersing agents such as maleated PE (PEgMA and ethylene-acrylic acid copolymer (EAA, at higher loadings, i.e. at 5 wt%. It has also been found that by increasing the polar wax content, i.e. 1–5 wt%, no useful improvement in the mechanical behaviour and morphology of the PE films was obtained. At high loadings of the polar wax relatively the short chains are arranged into the clay particles galleries and intercalation of the polyethylene chains between the clay platelets may be hindered. Additionally at high TEG loadings, the presence of the new polar groups of the wax also on external surfaces of the clay particles is expected to promote aggregation of the clay particles, with a loss of the beneficial effect of the more dispersed clay particles on the polymer mechanical/thermomechanical properties. The reported results strongly indicate that the amphiphilic TEG dispersing additive, may advantageously be used, at substantially lower loadings, as an alternative to incumbent PEgMA in the formulation of nanocomposites to improve their macroscopic performances.

  13. Numerical study on modeling of liquid film flow under countercurrent flow limitation in volume of fluid method

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Taro, E-mail: watanabe_t@qe.see.eng.osaka-u.ac.jp [Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita-shi, Osaka 565-7895 (Japan); Takata, Takashi, E-mail: takata.takashi@jaea.go.jp [Japan Atomic Energy Agency, 4002 Narita-chou, Oarai-machi, Higashi-Ibaraki-gun, Ibaraki 331-1393 (Japan); Yamaguchi, Akira, E-mail: yamaguchi@n.t.u-tokyo.ac.jp [Graduate School of Engineering, The University of Tokyo, 2-22 Shirakata-Shirane, Tokai-mura, Naka-gun, Ibaraki 319-1188 (Japan)

    2017-03-15

    Highlights: • Thin liquid film flow under CCFL was modeled and coupled with the VOF method. • The difference of the liquid flow rate in experiments of CCFL was evaluated. • The proposed VOF method can quantitatively predict CCFL with low computational cost. - Abstract: Countercurrent flow limitation (CCFL) in a heat transfer tube at a steam generator (SG) of pressurized water reactor (PWR) is one of the important issues on the core cooling under a loss of coolant accident (LOCA). In order to improve the prediction accuracy of the CCFL characteristics in numerical simulations using the volume of fluid (VOF) method with less computational cost, a thin liquid film flow in a countercurrent flow is modeled independently and is coupled with the VOF method. The CCFL characteristics is evaluated analytically in condition of a maximizing down-flow rate as a function of a void fraction or a liquid film thickness considering a critical thickness. Then, we have carried out numerical simulations of a countercurrent flow in a vertical tube so as to investigate the CCFL characteristics and compare them with the previous experimental results. As a result, it has been concluded that the effect of liquid film entrainment by upward gas flux will cause the difference in the experiments.

  14. Particle Dispersion Behaviors of Dense Gas-Particle Flows in Bubble Fluidized Bed

    Directory of Open Access Journals (Sweden)

    Sihao Lv

    2013-01-01

    Full Text Available An Euler-Euler two-fluid model incorporating a developed momentum transfer empirical coefficient is developed to study the particle dispersion behaviors of dense gas-particle flows in gas-fluidization reactor. In this model, the four-way couplings among gas-particles, particle-gas, and particle-particle collisions are fully considered based on kinetic theory of granular flows and an improved smooth continuous drag coefficient is utilized. Gas turbulent flow is solved by large eddy simulation. The particle fraction, the time-averaged axial particle velocity, the histogram of particle fluctuation velocity, and the wavelet analysis of pressure signals are obtained. The results are in good agreement with experimental measurements. The mean value and the variance of axial particle velocity are greater than those of radial particle velocities. Particle collision frequencies at bubble vibrant movement regions along axial direction are much higher than those of radial direction and attenuated along height increase. Low-frequency component of pressure signal indicating the bubble movement behaviors in the center of reactor is stronger than wall regions. Furthermore, the negative values represent the passed bubble and positive peak values disclose the continuous motion of single bubble.

  15. Solution of the Burger’s Equation for Longitudinal Dispersion Phenomena Occurring in Miscible Phase Flow through Porous Media

    Directory of Open Access Journals (Sweden)

    Monika N. Mehta

    2012-04-01

    Full Text Available An approximate solution of longitudinal dispersion phenomena occurring in two phase miscible fluid flow through porous media has been obtained by using the group theoretic approach. The longitudinal dispersion coefficient is assumed to be directly proportional to the concentration of the fluid for a distance x and at any time t > 0. The graphical representation for the concentration of the fluid for a distance x and at time t > 0 has been obtained using Mat lab coding.

  16. Large Eddy Simulation of Inertial Particle Preferential Dispersion in a Turbulent Flow over a Backward-Facing Step

    Directory of Open Access Journals (Sweden)

    Bing Wang

    2013-01-01

    Full Text Available Large eddy simulation of inertial particle dispersion in a turbulent flow over a backward-facing step was performed. The numerical results of both instantaneous particle dispersion and two-phase velocity statistics were in good agreement with the experimental measurements. The analysis of preferential dispersion of inertial particles was then presented by a wavelets analysis method for decomposing the two-phase turbulence signal obtained by numerical simulations, showing that the inertial particle concentration is separation from the Gaussian random distribution with very strong intermittencies. The statistical PDF of vorticity seen by particles shows that the inertial particles tend to accumulate in low vorticity regions where ∇u: ∇u is larger than zero. The concentration distribution of particle preferential dispersion preserves the historical effects. The research conclusions are useful for further understanding the two-phase turbulence physics and establishing accurate engineering prediction models of particle dispersion.

  17. EXPERIMENTAL MEASUREMENT AND NUMERICAL SIMULATION FOR FLOW FIELD AND FILM COOLING EFFECTIVENESS IN FILM-COOLED TURBINE

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Numerical simulation of three-dimensional flow field and film cooling effectiveness in film-cooled turbine rotor and stationary turbine cascade were carried out by using the κ-ε turbulence model, and the predictions of the three-dimensional velocities were compared with the measured results by Laser-Doppler Velocimetry (LDV). Results reveal the secondary flow near the blade surface in the wake region behind the jet hole. Compared with the stationary cascade, there are the centrifugal force and Coriolis force existing in the flow field of the turbine rotor, and these forces make the three-dimensional flow field change in the turbine rotor, especially for the radial velocity. The effect of rotation on the flow field and the film cooling effectiveness on the pressure side is more apparent than that on the suction side as is shown in the computational and measured results, and the low film cooling effectiveness appears on the pressure surface of the turbine rotor blade compared with that of the stationary cascade.

  18. Evaluation of Antibacterial Enrofloxacin in Eggs by Matrix Solid Phase Dispersion-Flow Injection Chemiluminescence

    Directory of Open Access Journals (Sweden)

    Xiaocui Duan

    2014-01-01

    Full Text Available The study based on the chemiluminescence (CL reaction of potassium ferricyanide and luminol in sodium hydroxide medium, enrofloxacin (ENRO could dramatically enhance CL intensities and incorporated with matrix solid-phase dispersion (MSPD technique (Florisil used as dispersant, dichloromethane eluted the target compounds. A simple flow injection chemiluminescence (FL-CL method with MSPD technique for determination of ENRO in eggs was described. Under optimal conditions, the CL intensities were linearly related to ENRO concentration ranging from 4.0×10-8 g.L−1 to 5.0×10-5 g.L−1, with a correlation coefficient of 0.9989 and detection limit of 5.0×10-9 g.L−1. The relative standard deviation was 3.6% at an ENRO concentration of 2.0×10-6 g.L−1. Our testing technique can help ensure food safety, and thus, protect public health.

  19. Cauchy problem for a class of nonlinear dispersive wave equations arising in elasto-plastic flow

    Science.gov (United States)

    Zhijian, Yang

    2006-01-01

    The paper studies the existence, both locally and globally in time, stability, decay estimates and blowup of solutions to the Cauchy problem for a class of nonlinear dispersive wave equations arising in elasto-plastic flow. Under the assumption that the nonlinear term of the equations is of polynomial growth order, say [alpha], it proves that when [alpha]>1, the Cauchy problem admits a unique local solution, which is stable and can be continued to a global solution under rather mild conditions; when [alpha][greater-or-equal, slanted]5 and the initial data is small enough, the Cauchy problem admits a unique global solution and its norm in L1,p(R) decays at the rate for 2

  20. Analysis of Nonlinear Dispersion of a Pollutant Ejected by an External Source into a Channel Flow

    Directory of Open Access Journals (Sweden)

    T. Chinyoka

    2010-01-01

    Full Text Available This paper focuses on the transient analysis of nonlinear dispersion of a pollutant ejected by an external source into a laminar flow of an incompressible fluid in a channel. The influence of density variation with pollutant concentration is approximated according to the Boussinesq approximation, and the nonlinear governing equations of momentum and pollutant concentration are obtained. The problem is solved numerically using a semi-implicit finite difference method. Solutions are presented in graphical form and given in terms of fluid velocity, pollutant concentration, skin friction, and wall mass transfer rate for various parametric values. The model can be a useful tool for understanding the polluting situations of an improper discharge incident and evaluating the effects of decontaminating measures for the water body.

  1. GPU-centric resolved-particle disperse two-phase flow simulation using the Physalis method

    Science.gov (United States)

    Sierakowski, Adam J.

    2016-10-01

    We present work on a new implementation of the Physalis method for resolved-particle disperse two-phase flow simulations. We discuss specifically our GPU-centric programming model that avoids all device-host data communication during the simulation. Summarizing the details underlying the implementation of the Physalis method, we illustrate the application of two GPU-centric parallelization paradigms and record insights on how to best leverage the GPU's prioritization of bandwidth over latency. We perform a comparison of the computational efficiency between the current GPU-centric implementation and a legacy serial-CPU-optimized code and conclude that the GPU hardware accounts for run time improvements up to a factor of 60 by carefully normalizing the run times of both codes.

  2. Flow-Angle and Airspeed Sensor System (FASS) Using Flush-Mounted Hot-Films Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Micron-thin surface hot-film gages are used to develop flow-angle and airspeed sensor system (FASS). Unlike Pitot-static and other pressure-based devices, which...

  3. Developing flow of a power-law liquid film on an inclined plane

    Science.gov (United States)

    Weinstein, Steven J.; Ruschak, Kenneth J.; Ng, Kam C.

    2003-10-01

    Developing flow of a liquid film along a stationary inclined wall is analyzed for a power-law constitutive equation. For films with appreciable inertia and therefore small interfacial slopes, the boundary-layer approximation may be used. The boundary-layer equations are solved numerically through the von Mises transformation that gives a partial differential equation over a semi-infinite strip and approximately by the method of von Kármán and Polhausen that gives an ordinary differential equation for the film thickness, called a film equation. Film equations derived from self-similar velocity profiles fail when the film thickens and the flow undergoes a supercritical to subcritical transition; a nonremovable singularity arises at the critical point, the location of the flow transition. A film equation is developed that accommodates this transition. Predictions exhibit a standing wave where hydrostatic pressure becomes important and opposes inertia. This thickening effect is accentuated for small angles of inclination at moderate Reynolds numbers. In the limit of small film thickness in which gravitational effects are negligible, the thickness profile is nonlinear in agreement with an independent and new similarity solution. This result contrasts with the established linear thickness profile for a Newtonian liquid. The circumstances in which the film equation gives results close to the full boundary layer equation are identified.

  4. Investigating flow pathways and transit times for the dispersal of hydrocarbon pollution on Rabots glacier, Kebnekaise

    Science.gov (United States)

    Clason, Caroline; Rosqvist, Gunhild; Coch, Caroline; Jarsjö, Jerker; Brugger, Keith

    2014-05-01

    On March 15th 2012 a Royal Norwegian Air Force Lockheed Martin C-130J Super Hercules aircraft crashed into the western face of Kebnekaise in northern Sweden, approximately 50 m below the mountain ridge, during a military exercise. It was carrying c.14000 l of kerosene jet fuel when it left Narvik, and an estimated minimum of 8 m3 of fuel was deposited on the mountain wall. Along with a large amount of debris from the wreckage, the fuel was subsequently buried by an avalanche in a north-west facing cirque on Rabots glacier. To assess the fate of the hydrocarbon pollution, a field campaign was organised to both monitor traces of pollution in the snowpack and the proglacial river system, and to quantify the preferential pathways and transit time for pollution dispersal from the crash source zone, through the glacier, to the proglacial outlet. An intensive series of dye tracing experiments were conducted as a proxy for potential pollution flow pathways during the 2013 ablation season. Percolation pathways through the snowpack and flow rates in the basal saturated layer were investigated in the vicinity of the crash site using rhodamine dye. Flow patterns across the slush and ice surface immediately downstream of the snowline were also investigated in terms of dye dispersion and the speed with which meltwater reaches the englacial system after emerging from the snowpack. The breakthrough of dye following injection in moulins was examined throughout the melt season, with injection sites situated along two longitudinal profiles of the glacier to investigate drainage efficiency with distance from the front. These experiments revealed a drainage axis in the glacial hydrological system, ending in two proglacial outlets of distinctly different turbidity. Furthermore, englacial dye tracing immediately downstream of the crash cirque snowpack revealed storage of dye over a long time period, followed by fast, efficient release of meltwater. This may suggest that pollution is

  5. Analogy Between Hydraulic Jump in Films Formed by Impinging Liquid Jet and Critical Flow in Internal Flows

    Institute of Scientific and Technical Information of China (English)

    Jaroslaw Mikielewicz

    2003-01-01

    Formulated are simple models for the flow in liquid film, formed by impinging jet, and a two-phase downward flow in pipe. The models are based on simplified equations of mass, momentum and energy. The solutions of such conservation equations may have regular points belonging to one integral curve only as well as turning points can be found amongst them, which refer to extreme values in the appropriate co-ordinate system. The solutions can also have singular points belonging to none or more than one integral curve. Both the turning and singular points have a clear physical meaning. They could be linked to critical flow conditions in the pipe flow or to the so-called hydraulic jump. Analogy existing between critical conditions in the pipe and the flow of liquid films formed by the liquid jet have been shown in the paper.

  6. Experimental study on two-dimensional film flow with local measurement methods

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Jin-Hwa, E-mail: evo03@snu.ac.kr [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Cho, Hyoung-Kyu [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kim, Seok [Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Euh, Dong-Jin, E-mail: djeuh@kaeri.re.kr [Korea Atomic Energy Research Institute, 989-111, Daedeok-daero, Yuseong-gu, Daejeon 305-600 (Korea, Republic of); Park, Goon-Cherl [Nuclear Thermal-Hydraulic Engineering Laboratory, Seoul National University, Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of)

    2015-12-01

    Highlights: • An experimental study on the two-dimensional film flow with lateral air injection was performed. • The ultrasonic thickness gauge was used to measure the local liquid film thickness. • The depth-averaged PIV (Particle Image Velocimetry) method was applied to measure the local liquid film velocity. • The uncertainty of the depth-averaged PIV was quantified with a validation experiment. • Characteristics of two-dimensional film flow were classified following the four different flow patterns. - Abstract: In an accident condition of a nuclear reactor, multidimensional two-phase flows may occur in the reactor vessel downcomer and reactor core. Therefore, those have been regarded as important issues for an advanced thermal-hydraulic safety analysis. In particular, the multi-dimensional two-phase flow in the upper downcomer during the reflood phase of large break loss of coolant accident appears with an interaction between a downward liquid and a transverse gas flow, which determines the bypass flow rate of the emergency core coolant and subsequently, the reflood coolant flow rate. At present, some thermal-hydraulic analysis codes incorporate multidimensional modules for the nuclear reactor safety analysis. However, their prediction capability for the two-phase cross flow in the upper downcomer has not been validated sufficiently against experimental data based on local measurements. For this reason, an experimental study was carried out for the two-phase cross flow to clarify the hydraulic phenomenon and provide local measurement data for the validation of the computational tools. The experiment was performed in a 1/10 scale unfolded downcomer of Advanced Power Reactor 1400 (APR1400). Pitot tubes, a depth-averaged PIV method and ultrasonic thickness gauge were applied for local measurement of the air velocity, the liquid film velocity and the liquid film thickness, respectively. The uncertainty of the depth-averaged PIV method for the averaged

  7. Early stage phase separation in pharmaceutical solid dispersion thin films under high humidity: improved spatial understanding using probe-based thermal and spectroscopic nanocharacterization methods.

    Science.gov (United States)

    Qi, Sheng; Moffat, Jonathan G; Yang, Ziyi

    2013-03-04

    Phase separation in pharmaceutical solid dispersion thin films under high humidity is still poorly understood on the submicrometer scale. This study investigated the phase separation of a model solid dispersion thin film, felodipine-PVP K29/32, prepared by spin-coating and analyzed using probe-based methods including atomic force microscopy, nanothermal analysis, and photothermal infrared microspectroscopy. The combined use of these techniques revealed that the phase separation process occurring in the thin films under high humidity is different from that in dry conditions reported previously. The initial stage of phase separation is primarily initiated in the bulk of the films as amorphous drug domains. Drug migration toward the surface of the solid dispersion film was then observed to occur under exposure to increased humidity. PVP cannot prevent phase separation of felodipine under high humidity but can minimize the crystallization of amorphous felodipine domains in the solid dispersion thin films. This study demonstrates the unique abilities of these nanocharacterization methods for studying, in three dimensions, the phase separation of thin films for pharmaceutical applications.

  8. Holographic storage of three-dimensional image and data using photopolymer and polymer dispersed liquid crystal films

    Science.gov (United States)

    Gao, Hong-Yue; Liu, Pan; Zeng, Chao; Yao, Qiu-Xiang; Zheng, Zhiqiang; Liu, Jicheng; Zheng, Huadong; Yu, Ying-Jie; Zeng, Zhen-Xiang; Sun, Tao

    2016-09-01

    We present holographic storage of three-dimensional (3D) images and data in a photopolymer film without any applied electric field. Its absorption and diffraction efficiency are measured, and reflective analog hologram of real object and image of digital information are recorded in the films. The photopolymer is compared with polymer dispersed liquid crystals as holographic materials. Besides holographic diffraction efficiency of the former is little lower than that of the latter, this work demonstrates that the photopolymer is more suitable for analog hologram and big data permanent storage because of its high definition and no need of high voltage electric field. Therefore, our study proposes a potential holographic storage material to apply in large size static 3D holographic displays, including analog hologram displays, digital hologram prints, and holographic disks. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474194, 11004037, and 61101176) and the Natural Science Foundation of Shanghai, China (Grant No. 14ZR1415500).

  9. Sensor for monitoring the vibration of a laser beam based on holographic polymer dispersed liquid crystal films.

    Science.gov (United States)

    Li, Ming Shian; Wu, Shing Trong; Fuh, Andy Ying-Guey

    2010-12-06

    A continuous multiple exposure diffraction grating (CMEDG) is fabricated holographically on polymer dispersed liquid crystal (PDLC) films using two-beam interference with multiple exposures. The grating is fabricated by exposing a PDLC film to 18 repeated exposure/non-exposure cycles with an angular step of ~10°/10° while it revolves a circle on a rotation stage. The structure of the sample thus formed is analyzed using a scanning electron microscope (SEM) and shows arc-ripples around the center. From the diffraction patterns of the formed grating obtained using a normally incident laser beam, some or all of the 18 recorded arc beams can be reconstructed, as determined by the probing location. Thus, it can be applied for use as a beam-vibration sensor for a laser.

  10. Influence of total gas flow rate on microcrystalline silicon films prepared by VHF-PECVD

    Institute of Scientific and Technical Information of China (English)

    Gao Yan-Tao; Zhang Xiao-Dan; Zhao Ying; Sun Jian; Zhu Feng; Wei Chang-Chun; Chen Fei

    2006-01-01

    Hydrogenated microcrystalline silicon (μc-Si:H) films are fabricated by very high frequency plasma enhanced chemical vapour deposition (VHF-PECVD) at a silane concentration of 7% and a varying total gas flow rate (H2+SiH4).Relations between the total gas flow rate and the electrical and structural properties as well as deposition rate of the films are studied. The results indicate that with the total gas flow rate increasing the photosensitivity and deposition rate increase, but the crystalline volume fraction (Xc) and dark conductivity decrease. And the intensity of (220) peak first increases then decreases with the increase of the total gas flow rate. The cause for the changes in the structure and deposition rate of the films with the total gas flow rate is investigated using optical emission spectroscopy (OES).

  11. A Mathematical Model for the Flow Resistance and the Related Hydrodynamic Dispersion Induced by River Dunes

    Directory of Open Access Journals (Sweden)

    Marilena Pannone

    2013-01-01

    Full Text Available Present work is aimed at the derivation of a simply usable equation for the total flow resistance associated with river bedforms, by a unifying approach allowing for bypassing some of the limiting restrictions usually adopted in similar types of studies. Specifically, we focused on the effect induced by the out-of-phase free surface undulations appearing in presence of sand dunes. The proposed expression, obtained by combining the balance of momentum referred to the control volume whose longitudinal dimension coincides with the dune wavelength and the energy balance integrated between its extreme sections, was tested by comparison with some laboratory experimental measurements available in the literature and referred to steady flow past fixed, variably rough bedforms. In terms of shear stress or friction factor, the proposed theory provides estimates in good agreement with the real data, especially if evaluated against the performances provided by other classical similar approaches. Moreover, when analyzed in terms of hydrodynamic dispersive properties as a function of the skin roughness on the basis of a previously derived analytical solution, the dune-covered beds seem to behave like meandering channels, responsible for a globally enhanced fluid particles longitudinal spreading, with a relatively reduced effect in the presence of less pronounced riverbed modelling.

  12. Particle morphology as a control of permeation in polymer films obtained from MMA/nBA colloidal dispersions.

    Science.gov (United States)

    Lestage, David J; Urban, Marek W

    2004-07-20

    The combination of precision-controlled weight loss measurements and spectroscopic surface FT-IR analysis allowed us to identify unique behaviors of poly(methyl methacrylate) (p-MMA). When MMA and n-butyl acrylate (nBA) are polymerized into p-MMA and p-nBA homopolymer blends, MMA/nBA random copolymers, and p-MMA/p-nBA core-shell morphologies, a controlled mobility and stratification of low molecular weight components occurs in films formed from coalesced colloidal dispersions. Due to different affinities toward water, p-MMA and p-nBA are capable of releasing water at different rates, depending upon particle morphological features of initial dispersions. As coalescence progresses, water molecules are released from the high free volume p-nBA particles, whereas p-MMA retains water molecules for the longest time due to its hydrophilic nature. As a result, water losses at extended coalescence times are relatively small for p-MMA. MMA/nBA copolymer and p-MMA/p-nBA blends follow the same trends, although the magnitudes of changes are not as pronounced. The p-MMA/p-nBA core-shell behavior resembles that of p-nBA homopolymer, which is attributed to significantly lower content of the p-MMA component in particles. Annealing of coalesced colloidal films at elevated temperatures causes migration of SDOSS to the F-A interface, but for films containing primarily p-nBA, reverse diffusion back into the bulk is observed. These studies illustrate that the combination of different particle morphologies and temperatures leads to controllable permeation processes through polymeric films. Copyright 2004 American Chemical Society

  13. Between-site differences in the scale of dispersal and gene flow in red oak.

    Directory of Open Access Journals (Sweden)

    Emily V Moran

    Full Text Available BACKGROUND: Nut-bearing trees, including oaks (Quercus spp., are considered to be highly dispersal limited, leading to concerns about their ability to colonize new sites or migrate in response to climate change. However, estimating seed dispersal is challenging in species that are secondarily dispersed by animals, and differences in disperser abundance or behavior could lead to large spatio-temporal variation in dispersal ability. Parentage and dispersal analyses combining genetic and ecological data provide accurate estimates of current dispersal, while spatial genetic structure (SGS can shed light on past patterns of dispersal and establishment. METHODOLOGY AND PRINCIPAL FINDINGS: In this study, we estimate seed and pollen dispersal and parentage for two mixed-species red oak populations using a hierarchical bayesian approach. We compare these results to those of a genetic ML parentage model. We also test whether observed patterns of SGS in three size cohorts are consistent with known site history and current dispersal patterns. We find that, while pollen dispersal is extensive at both sites, the scale of seed dispersal differs substantially. Parentage results differ between models due to additional data included in bayesian model and differing genotyping error assumptions, but both indicate between-site dispersal differences. Patterns of SGS in large adults, small adults, and seedlings are consistent with known site history (farmed vs. selectively harvested, and with long-term differences in seed dispersal. This difference is consistent with predator/disperser satiation due to higher acorn production at the low-dispersal site. While this site-to-site variation results in substantial differences in asymptotic spread rates, dispersal for both sites is substantially lower than required to track latitudinal temperature shifts. CONCLUSIONS: Animal-dispersed trees can exhibit considerable spatial variation in seed dispersal, although patterns may

  14. Detailed hydrodynamic characterization of harmonically excited falling-film flows: A combined experimental and computational study

    Science.gov (United States)

    Charogiannis, Alexandros; Denner, Fabian; van Wachem, Berend G. M.; Kalliadasis, Serafim; Markides, Christos N.

    2017-01-01

    We present results from the simultaneous application of planar laser-induced fluorescence (PLIF), particle image velocimetry (PIV) and particle tracking velocimetry (PTV), complemented by direct numerical simulations, aimed at the detailed hydrodynamic characterization of harmonically excited liquid-film flows falling under the action of gravity. The experimental campaign comprises four different aqueous-glycerol solutions corresponding to four Kapitza numbers (Ka=14 , 85, 350, 1800), spanning the Reynolds number range Re=2.3 -320 , and with forcing frequencies fw=7 and 10 Hz . PLIF was employed to generate spatiotemporally resolved film-height measurements, and PIV and PTV to generate two-dimensional velocity-vector maps of the flow field underneath the wavy film interface. The latter allows for instantaneous, highly localized velocity-profile, bulk-velocity, and flow-rate data to be retrieved, based on which the effect of local film topology on the flow field underneath the waves is studied in detail. Temporal sequences of instantaneous and local film height and bulk velocity are generated and combined into bulk flow-rate time series. The time-mean flow rates are then decomposed into steady and unsteady components, the former represented by the product of the mean film height and mean bulk velocity and the latter by the covariance of the film-height and bulk-velocity fluctuations. The steady terms are found to vary linearly with the flow Re, with the best-fit gradients approximated closely by the kinematic viscosities of the three examined liquids. The unsteady terms, typically amounting to 5 %-10 % of the mean and peaking at approximately 20 % , are found to scale linearly with the film-height variance. And, interestingly, the instantaneous flow rate is found to vary linearly with the instantaneous film height. Both experimental and numerical flow-rate data are closely approximated by a simple analytical relationship with only minor deviations. This relationship

  15. In situ characterization by SAXS of concentration polarization layers during cross-flow ultrafiltration of Laponite dispersions.

    Science.gov (United States)

    Pignon, F; Abyan, M; David, C; Magnin, A; Sztucki, M

    2012-01-17

    The structural organization inside the concentration polarization layer during cross-flow membrane separation process of Laponite colloidal dispersions has been characterized for the first time by in situ time-resolved small-angle X-ray scattering (SAXS). Thanks to the development of new "SAXS cross-flow filtration cells", concentration profiles have been measured as a function of the distance z from the membrane surface with 50 μm accuracy and linked to the permeation flux, cross-flow, and transmembrane pressure registered simultaneously. Different rheological behaviors (thixotropic gel with a yield stress or shear thinning sol) have been explored by controlling the mutual interactions between the particles as a result on the addition of peptizer. The structural reversibility of the concentration polarization layer has been demonstrated being in agreement with permeation flux measurements. These observations were related to structure of the dispersions under flow and their osmotic pressure.

  16. A quantitative comparison between the flow factor approach model and the molecular dynamics simulation results for the flow of a confined molecularly thin fluid film

    Science.gov (United States)

    Zhang, Yongbin

    2015-06-01

    Quantitative comparisons were made between the flow factor approach model and the molecular dynamics simulation (MDS) results both of which describe the flow of a molecularly thin fluid film confined between two solid walls. Although these two approaches, respectively, calculate the flow of a confined molecularly thin fluid film by different ways, very good agreements were found between them when the Couette and Poiseuille flows, respectively, calculated from them were compared. It strongly indicates the validity of the flow factor approach model in modeling the flow of a confined molecularly thin fluid film.

  17. Dispersion in oscillatory electro-osmotic flow through a parallel-plate channel with kinetic sorptive exchange at walls

    Institute of Scientific and Technical Information of China (English)

    吴朝安

    2014-01-01

    Dispersion in time-oscillatory electro-osmotic flows in a slit micro-channel under the effect of kinetic sorptive exchange at walls is theoretically investigated using the homogenization method. The two walls of the channel are considered to be made up of different materials, and therefore have different zeta potentials and sorption coefficients. A general expression for the Taylor disper-sion coefficient under different zeta potentials as well as various sorption conditions at the walls is derived analytically. The disper-sion coefficient is found to be dependent on the oscillation frequency, the Debye parameter, the species partition coefficient, the rea-ction kinetics and the ratio of the wall potentials. The results demonstrate that the presence of wall sorption tends to enhance the dispersion when the oscillation frequency is low, but the effect is negligible in high-frequency oscillatory flows. Moreover, it is found that the dispersion coefficient could be significantly changed by adjusting the relative wall potentials for low-frequency flows.

  18. Closure of the Averaged Equations for Disperse Two-Phase Flow by Direct Numerical Simulation: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Andrea Prosperetti

    2006-03-24

    The report briefly describes the activities carried out in the course of the project. A first line of research was the development of systematic closure relations for averaged equations for disperse multiphase flow. A second line was the development of efficient numerical methods for the simulation of Navier-Stokes flows with many suspended particles. The report also lists the 21 journal articles in which this work is more fully decsribed.

  19. LES/FDF simulation of particle dispersion in a gas-particle two phase plane wake flow

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A filtered density function (FDF) transport equation was derived for the fluid velocity seen by the particles in gas-particle two-phase flow. An LES/FDF simulation of a two-phase plane wake flow was carried out. The simulation results were compared with both the experimental photograph and the simulation results without using the FDF model, and proved that the LES/FDF model can clearly improve the spatial dispersion of the particle phase.

  20. Film Thickness and Flow Properties of Resin-Based Cements at Different Temperatures

    Directory of Open Access Journals (Sweden)

    Bagheri R.

    2013-06-01

    Full Text Available Statement of Problem: For a luting agent to allow complete seating of prosthetic restorations, it must obtain an appropriate flow rate maintaining a minimum film thickness. The performance of recently introduced luting agents in this regard has not been evaluated. Purpose: To measure and compare the film thickness and flow properties of seven resin-containing luting cements at different temperatures (37°C, 25°C and10°C. Material and Methods: Specimens were prepared from five resin luting cements; seT (SDI, Panavia F (Kuraray, Varioloink II (Ivoclar, Maxcem (Kerr, Nexus2 (Kerr and two resin-modified glass-ionomer luting cements (RM-GICs; GC Fuji Plus (GC Corporation, and RelyX Luting 2 (3 M/ESPE. The film thickness and flow rate of each cement (n=15 was determined using the test described in ISO at three different temperatures. Results: There was a linear correlation between film thickness and flow rate for most of the materials. Cooling increased fluidity of almost all materials while the effect of temperature on film thickness was material dependent. At 37°C, all products revealed a film thickness of less than 25µm except for GC Fuji Plus. At 25°C, all cements pro-duced a film thickness of less than 27 µm except for seT. At 10°C, apart from seT and Rely X Luting 2, the remaining cements showed a film thickness smaller than 20 µm.Conclusion: Cooling increased fluidity of almost all materials, however. the film thickness did not exceed 35 µm in either condition, in spite of the lowest film thickness being demonstrated at the lowest temperature.

  1. Effect of Static Deformation on Basic Flow Patterns in Thermocapillary-Driven Free Liquid Film

    Science.gov (United States)

    Fei, Linhao; Ikebukuro, Koichi; Katsuta, Takeshi; Kaneko, Toshihiro; Ueno, Ichiro; Pettit, Donald R.

    2016-11-01

    A series of terrestrial, parabolic-flight and on-orbit experiments on thermocapillary-driven flows in free liquid films are carried out. We focus on the basic flow patterns induced in the film formed in a rectangular hole by varying the film volume in order to make a comparison with the results of the fluid physics experiments under microgravity conditions conducted by one of the authors, Pettit, on the International Space Station. The free liquid film is formed in a rectangular hole of O(0.1 mm) in thickness under a designated temperature difference between the end walls. The temperature dependence of the surface tension results in a non-uniform surface tension distribution over the free surfaces. A liquid generally has a negative temperature coefficient of surface tension; i.e., the fluid over a free surface is driven from a higher-temperature region to a lower-temperature region. In the case of a thin free liquid film with two free surfaces, however, an unusual flow pattern is realized. That is, the fluid seems to be driven toward the heated region from a colder region. In order to understand the physical mechanism of this behavior in the free liquid film, a series of on-orbit and ground experiments were conducted. We indicate several flow patterns in the film and corresponding film profiles as well as the surface temperature distribution. We also try to illustrate the cross-sectional flow structures in the thin free liquid film with two free surfaces.

  2. Effect of Static Deformation on Basic Flow Patterns in Thermocapillary-Driven Free Liquid Film

    Science.gov (United States)

    Fei, Linhao; Ikebukuro, Koichi; Katsuta, Takeshi; Kaneko, Toshihiro; Ueno, Ichiro; Pettit, Donald R.

    2017-02-01

    A series of terrestrial, parabolic-flight and on-orbit experiments on thermocapillary-driven flows in free liquid films are carried out. We focus on the basic flow patterns induced in the film formed in a rectangular hole by varying the film volume in order to make a comparison with the results of the fluid physics experiments under microgravity conditions conducted by one of the authors, Pettit, on the International Space Station. The free liquid film is formed in a rectangular hole of O(0.1 mm) in thickness under a designated temperature difference between the end walls. The temperature dependence of the surface tension results in a non-uniform surface tension distribution over the free surfaces. A liquid generally has a negative temperature coefficient of surface tension; i.e., the fluid over a free surface is driven from a higher-temperature region to a lower-temperature region. In the case of a thin free liquid film with two free surfaces, however, an unusual flow pattern is realized. That is, the fluid seems to be driven toward the heated region from a colder region. In order to understand the physical mechanism of this behavior in the free liquid film, a series of on-orbit and ground experiments were conducted. We indicate several flow patterns in the film and corresponding film profiles as well as the surface temperature distribution. We also try to illustrate the cross-sectional flow structures in the thin free liquid film with two free surfaces.

  3. Generation of strength in a drying film: How fracture toughness depends on dispersion properties

    Science.gov (United States)

    Birk-Braun, Natalie; Yunus, Kamran; Rees, Eric J.; Schabel, Wilhelm; Routh, Alexander F.

    2017-02-01

    The fracture toughness of colloidal films is measured by characterizing cracks which form during directional drying. Images from a confocal microscope are processed to measure the crack width as a function of distance from the crack tip. Applying theory for thin elastic films the fracture toughness is extracted. It is found that the fracture toughness scales with the particle size to the -0.8 power and that the critical energy release rate scales with the particle size to the -1.3 power. In addition, the fracture toughness is found to increase at lower evaporation rates, but the film thickness does not have a significant effect.

  4. Synthesis of polyhedral oligomeric silsesquioxane (POSS) functionalized carbon nanotubes for improved dispersion in polyurethane films

    Science.gov (United States)

    Kou, Xiaonan

    Carbon nanotube (CNT) polymer nanocomposites are promising advanced materials. These materials exhibit the advantages of traditional polymeric materials, such as being light weight and easy to process, combined with the potential to exhibit enhanced mechanical, thermal and electrical properties compared to pure polymers. To achieve substantial improvement of composite properties at low CNT loading, uniform dispersion of CNTs in the polymer matrix and strong CNT-polymer interfacial interaction are needed. However, it is difficult to achieve adequate dispersion and interfacial interactions due to the inert nature of CNTs. In this project, polyhedral oligomeric silsequioxane (POSS) will be used as a dispersing agent for multi-walled carbon nanotubes (MWNTs) in polyurethane (PU) matrices. This dissertation consists of six chapters. Chapter I provides a detailed introduction of the fundamental knowledge of CNTs, PU, and POSS. At the end of this chapter, the motivation and rationale of this research are given. Chapter II establishes the overall goal and specific objectives of this research. Chapter III describes the synthesis and characterization of three POSS modified CNTs and one organosilane modified CNT. Grafting efficiency of the different grafted molecules are calculated and compared. Chapter IV discusses the dispersion behavior of four covalently modified CNTs in both solvents and PU matrices. Differences in dispersion behaviors of the modified CNTs are correlated to the solubility parameters of the grafting molecules and the surface structures of modified CNTs. Chapter V provides further discussion of the dispersion of POSS and silane modified CNTs by reviewing the assessment of the physical properties of PU composites containing the modified CNTs. Morphological, thermal, mechanical and electrical properties are used to estimate the interactions of the modified CNTs with the PU matrix. Chapter VI explores the function of the trisilanolphenyl POSS lithium salt

  5. Effects of cation compositions on the electronic properties and optical dispersion of indium zinc tin oxide thin films by electron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Denny, Yus Rama [Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Seo, Soonjoo [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-806 (Korea, Republic of); Lee, Kangil; Oh, Suhk Kun [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Kang, Hee Jae, E-mail: hjkang@cbu.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Heo, Sung; Chung, Jae Gwan; Lee, Jae Cheol [Analytical Engineering Center, Samsung Advanced Institute of Technology, Suwon 440-600 (Korea, Republic of); Tougaard, Sven [Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, DK-5230 Odense M. (Denmark)

    2015-02-15

    Highlights: • REELS analysis can provide optical dispersion and electronic properties of oxide materials. • The band gap varied with In/Zn/Sn compositions and increased after annealing. • The optical properties were examined using REELS in conjunction with the Tougaard–Yubero model. • The dispersion parameters were determined by a single-oscillator Wemple–DiDomenico model. • The Zn and Sn contents play a crucial role in determining the single-oscillator constant and dispersion energy of IZTO thin films. - Abstract: The electronic properties and optical dispersion of indium zinc tin oxide (IZTO) films with different cation compositions were investigated by reflection electron energy loss spectroscopy (REELS). The REELS spectra of IZTO films revealed that the band gap varied with different Sn/Zn ratios and In content. The optical properties were examined with REELS data using Tougaard–Yubero model and the results were compared with the envelope of the transmission spectra obtained using a UV-spectrometer. The dispersion behavior of the refractive index from REELS results was studied in terms of the single-oscillator Wemple–DiDomenico model. The results showed that the different compositions of In/Zn/Sn caused a change in the dispersion parameters of IZTO thin films in contrast to the static values of refractive indices and dielectric constant which remained the same. Our work demonstrated that REELS is an efficient tool to study the optical properties of a material by obtaining the optical parameters.

  6. Hot-Film and Hot-Wire Anemometry for a Boundary Layer Active Flow Control Test

    Science.gov (United States)

    Lenahan, Keven C.; Schatzman, David M.; Wilson, Jacob Samuel

    2013-01-01

    Unsteady active flow control (AFC) has been used experimentally for many years to minimize bluff-body drag. This technology could significantly improve performance of rotorcraft by cleaning up flow separation. It is important, then, that new actuator technologies be studied for application to future vehicles. A boundary layer wind tunnel was constructed with a 1ft-x-3ft test section and unsteady measurement instrumentation to study how AFC manipulates the boundary layer to overcome adverse pressure gradients and flow separation. This unsteady flow control research requires unsteady measurement methods. In order to measure the boundary layer characteristics, both hot-wire and hot-film Constant Temperature Anemometry is used. A hot-wire probe is mounted in the flow to measure velocity while a hot-film array lays on the test surface to measure skin friction. Hot-film sensors are connected to an anemometer, a Wheatstone bridge circuit with an output that corresponds to the dynamic flow response. From this output, the time varying flow field, turbulence, and flow reversal can be characterized. Tuning the anemometers requires a fan test on the hot-film sensors to adjust each output. This is a delicate process as several variables drastically affect the data, including control resistance, signal input, trim, and gain settings.

  7. Controlling the dispersion and configuration of nanofillers in electrically driven polymer jets with and without air flow

    Science.gov (United States)

    Zhmayev, Yevgen; Joo, Yong; Park, Jay; Fei, Ling; Kaur, Prabhleen; Liu, Hongshen

    2015-03-01

    Controlling the dispersion of nanofillers in polymer matrices has a significant effect on their properties. Employing circumferentially uniform air flow through the sheath layer of the concentric coaxial nozzle, the gas-assisted electrospinning utilizes both high electric field and controlled air flow which can offer i) enhanced stretching of fluid jet and thus much higher throughput and thinner fibers, and ii) better control of dispersion and configuration of nanofillers in a polymer matrix even at high loadings. The ability to tailor the distribution of various nanofillers (1.85-12.92 vol. % of spherical SiO2\\ and Si nanoparticles and rod/tube-like carbon nanotubes and carbon nanoribbons) in a polyvinyl alcohol (PVA) jet was demonstrated by varying electric potentials in conventional electrospinning and air flow rates in gas-assisted electrospinning. The distribution of nanofillers in nanofibers was measured by transmission electron microscopy (TEM), and analyzed using an image processing software to obtain concentration profiles. By increasing the electric potential in conventional electrospinning from 80 to 125 kV/m, we observed almost a twofold improvement in NP distribution. The further enhancement of nanoparticle dispersion was observed in gas-assisted electrospinning: Our analysis indicated an additional 70 percent improvement with the application of high, but controlled air flow. Lastly, the enhanced performance by the resulting nanofibers with controlled nanofiller dispersion will also be addressed in Li-ion battery anode applications. Axium battery, AZ Electronic Materials.

  8. Regional gene flow and population structure of the wind-dispersed plant species Hypochaeris radicata (Asteraceae) in an agricultural landscape

    NARCIS (Netherlands)

    Mix, C.; Arens, P.F.P.; Rengelink, R.; Smulders, M.J.M.; Groenendael, van J.M.; Ouburg, J.

    2006-01-01

    Using microsatellites, we investigated population structure and gene flow of the short-lived, wind-dispersed plant species Hypochaeris radicata in a fragmented agricultural landscape where more than 99% of the nutrient-poor grasslands have disappeared over the last century. We sampled populations in

  9. Bulk flow coupled to a viscous interfacial film sheared by a rotating knife edge

    Science.gov (United States)

    Raghunandan, Aditya; Rasheed, Fayaz; Hirsa, Amir; Lopez, Juan

    2015-11-01

    The measurement of the interfacial properties of highly viscous biofilms, such as DPPC (the primary component of lung surfactant), present on the surface of liquids (bulk phase) continues to attract significant attention. Most measurement techniques rely on shearing the interfacial film and quantifying its viscous response in terms of a surface (excess) viscosity at the air-liquid interface. The knife edge viscometer offers a significant advantage over other approaches used to study highly viscous films as the film is directly sheared by a rotating knife edge in direct contact with the film. However, accurately quantifying the viscous response is non-trivial and involves accounting for the coupled interfacial and bulk phase flows. Here, we examine the nature of the viscous response of water insoluble DPPC films sheared in a knife edge viscometer over a range of surface packing, and its influence on the strength of the coupled bulk flow. Experimental results, obtained via Particle Image Velocimetry in the bulk and at the surface (via Brewster Angle Microscopy), are compared with numerical flow predictions to quantify the coupling across hydrodynamic flow regimes, from the Stokes flow limit to regimes where flow inertia is significant. Supported by NNX13AQ22G, National Aeronautics and Space Administration.

  10. Hypergeometric steady solution of hydromagnetic nano liquid film flow over an unsteady stretching sheet

    Science.gov (United States)

    Metri, Prashant G.; Narayana, Mahesha; Silvestrov, Sergei

    2017-01-01

    In this paper, we examine the hydromagnetic boundary layer flow and heat transfer characteristics of a laminar nanoliquid film over an unsteady stretching sheet is presented. The highly nonlinear partial differential equations governing flow and heat transport are simplified using similarity transformation. The analytical solutions of the resulting ODEs are obtained for some special case of nano liquid film using hypergeometric power series functions, and from which the analytical solutions of the original problem are presented. The influence of pertinent parameters such as the magnetic parameter, the solid volume fraction of nanoparticles and the type of nanofluid on the flow, heat transfer, Nusselt number and skin friction coefficient is discussed analytically.

  11. Sex-biased dispersal and spatial heterogeneity affect landscape resistance to gene flow in fisher

    Science.gov (United States)

    Jody M. Tucker; Fred W. Allendorf; Richard L. Truex; Michael K. Schwartz

    2017-01-01

    Genetic connectivity results from the dispersal and reproduction of individuals across landscapes. Mammalian populations frequently exhibit sex-biased dispersal, but this factor has rarely been addressed in individual-based landscape genetics research. In this study, we evaluate the effects of sexbiased dispersal and landscape heterogeneity on genetic connectivity in a...

  12. Recovery of rectified signals from hot-wire/film anemometers due to flow reversal in oscillating flows.

    Science.gov (United States)

    Yang, Yingchen; Jones, Douglas L; Liu, Chang

    2010-01-01

    Hot-wire/film anemometers have been broadly used in experimental studies in fluid mechanics, acoustics, and ocean engineering. Yet, it is well known that hot-wire/film anemometers rectify the signal outputs due to the lack of sensitivity to flow direction. This main drawback, in turn, makes them less useful for diverse fluctuating flow measurements. To solve this issue, a rectification recovery method has been developed based on reconstruction of the Fourier series expansion in conjunction with signal-squaring approach. This signal recovery method was experimentally examined and proven to be successful for both conventional and microfabricated hot-wire/film anemometers. The method was further applied to dipole field measurements, with data from recovered signals perfectly matching the analytical model of the dipole field.

  13. Heat and mass transfer in two-phase flow - A mathematical model for laminar film flow and its experimental validation

    Science.gov (United States)

    Conder, J. R.; Gunn, D. J.; Shaikh, M. A.

    1982-08-01

    A mathematical model is presented for the vaporisation of liquid from a laminar film flowing down the inside surface of a smooth tube into a countercurrent laminar flow of gas. The partial differential equations that describe temperature and composition distributions are integrated across the tube to give a set of four coupled ordinary differential equations. A numerical method for the solution of the equations is proposed and examined; the method is posed to solve the transient response for heat and mass transfer. A satisfactory solution is found for a range of space and time intervals. The mathematical model has been validated by experimental measurements on a falling film evaporator with evaporation occurring at sub-boiling temperatures from a laminar liquid film into a laminar gas stream. The performance of the evaporator is assessed.

  14. Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow.

    Science.gov (United States)

    Hu, L H; Huo, R; Yang, D

    2009-07-15

    The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) x 18 m (height) x 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103-113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89-103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213-3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons--a large eddy simulation, Atmos. Environ. 38 (2004) 6883-6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934-949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire.

  15. Large-eddy simulation of atmospheric boundary layer flow and passive scalar dispersion over idealized urban surfaces

    Science.gov (United States)

    Cheng, Wai Chi; Porté-Agel, Fernando

    2015-04-01

    Accurate prediction of atmospheric boundary layer (ABL) flow and its interaction with urban surfaces is critical for understanding the transport of momentum and scalars within and above cities. This, in turn, is essential for predicting the local climate and pollutant dispersion patterns in urban areas. Large-eddy simulation (LES) explicitly resolves the large-scale turbulent eddy motions and, therefore, can potentially provide improved understanding and prediction of flows and scalar transport inside and above urban canopies. In this study, LES is used to simulate the dispersion of passive scalar over idealized urban surfaces represented by uniform arrays of cubes. A modulated gradient subgird-scale (SGS) model is used to parametrize the SGS fluxes of momentum and scalar, and an immersed boundary method is used to model the presence of cubes. A similar LES framework for flow was validated in our previous studies in simulations of turbulent boundary-layer flow past a 2D block and a uniform array of cubes. Here, the LES framework is further validated with wind tunnel experimental data of passive scalar dispersion within and above a staggered array of cubes with a localized scalar source at ground level. Good agreement between the simulation results and experimental data are found in the vertical and horizontal profiles of scalar concentration in different streamwise locations. After the validation, the LES framework is used to simulate the scalar transport at rural-to-urban flow transition region and the results obtained are presented.

  16. The determination of the thickness and the optical dispersion property of gold film using spectroscopy of a surface plasmon in the frequency domain

    Institute of Scientific and Technical Information of China (English)

    Huang Yan; Ye Hong-An; Li Song-Quan; Dou Yin-Feng

    2013-01-01

    We propose to use wavelength modulation approach,i.e.,the spectroscopy of a surface plasmon in the frequency domain,to characterize the optical dispersion property of gold film.Using this method,we determine the dispersion relationship of gold film in a wavelength range from 537.12 nm to 905.52 nm,and our results accord well with the reported results by other authors.This method is particularly suited for studying the optical dispersion properties of thin metal films,because a series of dielectric constants over a wide spectral range can be determined simultaneously via only a single scan of the incident angle,thereby avoiding the repeated measurements required when using the angular modulation approach.

  17. Large eddy simulation of atmospheric boundary layer flows and application to pollen dispersal

    Science.gov (United States)

    Chamecki, Marcelo

    This work presents a framework for simulating pollen dispersal by wind based on Large Eddy Simulation. Important phenomena such as pollen emission by plants and ground deposition are modeled through the boundary condition. An expression for the vertical equilibrium concentration profile of pollen particles, including the effect of the canopy on the eddy diffusivity as well as corrections for atmospheric stability, is proposed for this purpose. This expression is validated against measurements of vertical concentration profiles of corn pollen above a corn field. The numerical discretization of the evolution equations follows a new approach in which different discretization schemes are used for the velocity and concentration fields. A new interpolation scheme is proposed to couple the two discretizations. The numerical model is validated against previously published experiments of point-source releases of glass beads and pollen grains in the atmospheric boundary layer. The numerical model is used together with experimental data of pollen emission and downwind deposition from a natural field obtained near Washington DC in the summer of 2006. The combined analysis of experimental and numerical data elucidates the emission, transport, and deposition processes in considerable detail. In particular, the relative fractions of pollen deposited inside the source field and airborne at the edge of the field can be quantified. Investigations based on experimental data and direct numerical simulation of the effects of the local structure of the flow on subgrid scale models for simulations of the atmospheric boundary layer are also presented.

  18. Google-Earth Based Visualizations for Environmental Flows and Pollutant Dispersion in Urban Areas

    Science.gov (United States)

    Liu, Daoming; Kenjeres, Sasa

    2017-01-01

    In the present study, we address the development and application of an efficient tool for conversion of results obtained by an integrated computational fluid dynamics (CFD) and computational reaction dynamics (CRD) approach and their visualization in the Google Earth. We focus on results typical for environmental fluid mechanics studies at a city scale that include characteristic wind flow patterns and dispersion of reactive scalars. This is achieved by developing a code based on the Java language, which converts the typical four-dimensional structure (spatial and temporal dependency) of data results in the Keyhole Markup Language (KML) format. The visualization techniques most often used are revisited and implemented into the conversion tool. The potential of the tool is demonstrated in a case study of smog formation due to an intense traffic emission in Rotterdam (The Netherlands). It is shown that the Google Earth can provide a computationally efficient and user-friendly means of data representation. This feature can be very useful for visualization of pollution at street levels, which is of great importance for the city residents. Various meteorological and traffic emissions can be easily visualized and analyzed, providing a powerful, user-friendly tool for traffic regulations and urban climate adaptations. PMID:28257078

  19. Google-Earth Based Visualizations for Environmental Flows and Pollutant Dispersion in Urban Areas.

    Science.gov (United States)

    Liu, Daoming; Kenjeres, Sasa

    2017-03-02

    In the present study, we address the development and application of an efficient tool for conversion of results obtained by an integrated computational fluid dynamics (CFD) and computational reaction dynamics (CRD) approach and their visualization in the Google Earth. We focus on results typical for environmental fluid mechanics studies at a city scale that include characteristic wind flow patterns and dispersion of reactive scalars. This is achieved by developing a code based on the Java language, which converts the typical four-dimensional structure (spatial and temporal dependency) of data results in the Keyhole Markup Language (KML) format. The visualization techniques most often used are revisited and implemented into the conversion tool. The potential of the tool is demonstrated in a case study of smog formation due to an intense traffic emission in Rotterdam (The Netherlands). It is shown that the Google Earth can provide a computationally efficient and user-friendly means of data representation. This feature can be very useful for visualization of pollution at street levels, which is of great importance for the city residents. Various meteorological and traffic emissions can be easily visualized and analyzed, providing a powerful, user-friendly tool for traffic regulations and urban climate adaptations.

  20. Google-Earth Based Visualizations for Environmental Flows and Pollutant Dispersion in Urban Areas

    Directory of Open Access Journals (Sweden)

    Daoming Liu

    2017-03-01

    Full Text Available In the present study, we address the development and application of an efficient tool for conversion of results obtained by an integrated computational fluid dynamics (CFD and computational reaction dynamics (CRD approach and their visualization in the Google Earth. We focus on results typical for environmental fluid mechanics studies at a city scale that include characteristic wind flow patterns and dispersion of reactive scalars. This is achieved by developing a code based on the Java language, which converts the typical four-dimensional structure (spatial and temporal dependency of data results in the Keyhole Markup Language (KML format. The visualization techniques most often used are revisited and implemented into the conversion tool. The potential of the tool is demonstrated in a case study of smog formation due to an intense traffic emission in Rotterdam (The Netherlands. It is shown that the Google Earth can provide a computationally efficient and user-friendly means of data representation. This feature can be very useful for visualization of pollution at street levels, which is of great importance for the city residents. Various meteorological and traffic emissions can be easily visualized and analyzed, providing a powerful, user-friendly tool for traffic regulations and urban climate adaptations.

  1. Gas dispersion and immobile gas volume in solid and porous particle biofilter materials at low air flow velocities.

    Science.gov (United States)

    Sharma, Prabhakar; Poulsen, Tjalfe G

    2010-07-01

    Gas-phase dispersion in granular biofilter materials with a wide range of particle sizes was investigated using atmospheric air and nitrogen as tracer gases. Two types of materials were used: (1) light extended clay aggregates (LECA), consisting of highly porous particles, and (2) gravel, consisting of solid particles. LECA is a commercial material that is used for insulation, as a soil conditioner, and as a carrier material in biofilters for air cleaning. These two materials were selected to have approximately the same particle shape. Column gas transport experiments were conducted for both materials using different mean particle diameters, different particle size ranges, and different gas flow velocities. Measured breakthrough curves were modeled using the advection-dispersion equation modified for mass transfer between mobile and immobile gas phases. The results showed that gas dispersivity increased with increasing mean particle diameter for LECA but was independent of mean particle diameter for gravel. Gas dispersivity also increased with increasing particle size range for both media. Dispersivities in LECA were generally higher than for gravel. The mobile gas content in both materials increased with increasing gas flow velocity but it did not show any strong dependency on mean particle diameter or particle size range. The relative fraction of mobile gas compared with total porosity was highest for gravel and lowest for LECA likely because of its high internal porosity.

  2. Effects of germane flow rate in electrical properties of a-SiGe:H films for ambipolar thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Dominguez, Miguel, E-mail: madominguezj@gmail.com [Centro de Investigaciones en Dispositivos Semiconductores, Instituto de Ciencias, Benemerita Universidad Autonoma de Puebla (BUAP), Puebla 72570 (Mexico); Rosales, Pedro, E-mail: prosales@inaoep.mx [National Institute for Astrophysics, Optics and Electronics (INAOE), Electronics Department, Luis Enrique Erro No. 1, Puebla 72840 (Mexico); Torres, Alfonso [National Institute for Astrophysics, Optics and Electronics (INAOE), Electronics Department, Luis Enrique Erro No. 1, Puebla 72840 (Mexico); Flores, Francisco [Centro de Investigaciones en Dispositivos Semiconductores, Instituto de Ciencias, Benemerita Universidad Autonoma de Puebla (BUAP), Puebla 72570 (Mexico); Molina, Joel; Moreno, Mario [National Institute for Astrophysics, Optics and Electronics (INAOE), Electronics Department, Luis Enrique Erro No. 1, Puebla 72840 (Mexico); Luna, Jose [Centro de Investigaciones en Dispositivos Semiconductores, Instituto de Ciencias, Benemerita Universidad Autonoma de Puebla (BUAP), Puebla 72570 (Mexico); Orduña, Abdu [Centro de Investigación en Biotecnología Aplicada (CIBA), IPN, Tlaxcala, Tlaxcala 72197 (Mexico)

    2014-07-01

    In this work, the study of germane flow rate in electrical properties of a-SiGe:H films is presented. The a-SiGe:H films deposited by low frequency plasma-enhanced chemical vapor deposition at 300 °C were characterized by Fourier transform infrared spectroscopy, measurements of temperature dependence of conductivity and UV–visible spectroscopic ellipsometry. After finding the optimum germane flow rate conditions, a-SiGe:H films were deposited at 200 °C and analyzed. The use of a-SiGe:H films at 200 °C as active layer of low-temperature ambipolar thin-film transistors (TFTs) was demonstrated. The inverted staggered a-SiGe:H TFTs with Spin-On Glass as gate insulator were fabricated. These results suggest that there is an optimal Ge content in the a-SiGe:H films that improves its electrical properties. - Highlights: • As the GeH{sub 4} flow rate increases the content of oxygen decreases. • Ge-H bonds show the highest value in a-SiGe:H films with GeH{sub 4} flow of 105 sccm. • Films with GeH{sub 4} flow of 105 sccm show the highest activation energy. • An optimum incorporation of germanium is obtained with GeH{sub 4} flow rate of 105 sccm. • At 200 °C the optimum condition of the a-SiGe:H films remain with no changes.

  3. Simulation and modeling of turbulent non isothermal vapor-droplet dispersed flow

    Energy Technology Data Exchange (ETDEWEB)

    Baalbaki, Daoud

    2011-12-15

    One of the reference accident that may occur in PWR (Pressurized Water Reactor) is LOCA (Loss of Coolant Accident). The LOCA is studied to design some emergency systems implemented in the basic nuclear installations. The LOCA corresponds to the break of a pipe in the primary loop. This accident is associated with a loss of pressure which leads to the vaporization of the water in the reactor core and then to the rise of the temperature of the assemblies. In this study, we focus on the area of vapor-droplet flow, where the cooling effectiveness of such a mixture is a major concern. The droplets act as heat sinks for the vapor and control the vapor temperature profile which, in turn, determines the wall heat transfer rate. Our general objective is to ameliorate the modeling of the vapor-droplet flow (i.e. at CFD scale). Particularly the estimation of the radial distribution of the droplets. The volume fraction distribution of the two phases depends on the size and dispersion of the droplets in the flow. The size of the droplets is controlled by the rupture and coalescence mechanisms and the interfacial mass transfer (evaporation/condensation). The distribution of the droplets is controlled by the transfer of momentum between the two phases. Our study focuses particularly on the latter point. We are restricted to flows where the liquid water flows under the form of non-deformable spherical droplets that do not interact with each other. Both phases are treated by a two-fluid approach Euler-Euler. In chapter 2, a description of two-phase flow model is presented, using separate mass, momentum, and energy equations for the two phases. These separate balance equations are obtained in an averaging process starting from the local instantaneous conservation equations of the individual phases. During the averaging process, important information on local flow processes are lost and, consequently, additional correlations are needed in order to close the system of equations. The

  4. The flow of a thin liquid film on a stationary and rotating disk. I - Experimental analysis and flow visualization

    Science.gov (United States)

    Thomas, S.; Faghri, A.; Hankey, W.

    1990-01-01

    The mean thickness of a thin liquid film of deionized water with a free surface on a stationary and rotating horizontal disk has been measured with a nonobtrusive capacitance technique. The measurements were taken when the rotational speed was 0-300 RPM and the flow rate was 7.0-15.0 LPM. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. When the disk was stationary, a circular hydraulic jump was present on the disk. Surface waves were found in the supercritical and subcritical regions at all flow rates studied. When the rotational speed of the disk is low, a standing wave at the edge of the disk was present. As the rotational speed increased, the surface waves changed from the wavy-laminar region to a region in which the waves ran nearly radially across the disk on top of a thin substrate of fluid.

  5. Film boiling on spheres in single- and two-phase flows.

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.; Theofanous, T. G.

    2000-08-29

    Film boiling on spheres in single- and two-phase flows was studied experimentally and theoretically with an emphasis on establishing the film boiling heat transfer closure law, which is useful in the analysis of nuclear reactor core melt accidents. Systematic experimentation of film boiling on spheres in single-phase water flows was carried out to investigate the effects of liquid subcooling (from 0 to 40 C), liquid velocity (from 0 to 2 m/s), sphere superheat (from 200 to 900 C), sphere diameter (from 6 to 19 mm), and sphere material (stainless steel and brass) on film boiling heat transfer. Based on the experimental data a general film boiling heat transfer correlation is developed. Utilizing a two-phase laminar boundary-layer model for the unseparated front film region and a turbulent eddy model for the separated rear region, a theoretical model was developed to predict the film boiling heat transfer in all single-phase regimes. The film boiling from a sphere in two-phase flows was investigated both in upward two-phase flows (with void fraction from 0.2 to 0.65, water velocity from 0.6 to 3.2 m/s, and steam velocity from 3.0 to 9.0 m/s) and in downward two-phase flows (with void fraction from 0.7 to 0.95, water velocity from 1.9 to 6.5 m/s, and steam velocity from 1.1 to 9.0 m/s). The saturated single-phase heat transfer correlation was found to be applicable to the two-phase film boiling data by making use of the actual water velocity (water phase velocity), and an adjustment factor of (1 - {alpha}){sup 1/4} (with a being the void fraction) for downward flow case only. Slight adjustments of the Reynolds number exponents in the correlation provided an even better interpretation of the two-phase data. Preliminary experiments were also conducted to address the influences of multi-sphere structure on the film boiling heat transfer in single- and two-phase flows.

  6. Rheological effect on thermocapillary flow of a liquid film jet painted on a moving boundary

    Institute of Scientific and Technical Information of China (English)

    HU; Wenrui(胡文瑞); HUI; W.H.(许为厚)

    2002-01-01

    In the present paper, a liquid (or melt) film of relatively high temperature ejected from a vessel and painted on the moving solid film is analyzed by using the second-order fluid model of the non-Newtonian fluid. The thermocapillary flow driven by the temperature gradient on the free surface of a Newtonian liquid film was discussed before. The effect of rheological fluid on thermocapillary flow is considered in the present paper. The analysis is based on the approximations of lubrication theory and perturbation theory. The equation of liquid height and the process of thermal hydrodynamics of the non-Newtonian liquid film are obtained, and the case of weak effect of the rheological fluid is solved in detail.

  7. Flow field distribution of liquid film of water lubricated bearing-rotor coupling systems

    Science.gov (United States)

    Hu, Q. L.; Hu, J. N.; Ye, X. Y.; Zhang, D. S.; Zheng, J. B.

    2016-05-01

    According to the desalination high-pressure pump water lubricated bearing-rotor coupling systems flow field distribution of liquid film in the starting transient process and its power transmission mechanism can lay the foundation of further exploring and judging lubrication state at the boot process. By using the computational fluid dynamics Fluent secondary development platform and calling the relevant DEFINE macro function to achieve the translation and rotation movement of the journal, we will use the dynamic grid technique to realize the automatic calculation and grid update of water lubricated bearings 3d unsteady liquid film flow field, and finally we will dispose the results of numerical simulation and get the pressure. When the eccentricity is large, film thickness was negatively correlated with the pressure, and positive with the velocity. Differential pressure was negatively correlated with velocity. When the eccentricity is small, film thickness is no significant relationship with differential pressure and velocity. Differential pressure has little difference with velocity.

  8. Microstructure and optical dispersion characterization of nanocomposite sol-gel TiO₂-SiO₂ thin films with different compositions.

    Science.gov (United States)

    Kermadi, S; Agoudjil, N; Sali, S; Zougar, L; Boumaour, M; Broch, L; En Naciri, A; Placido, F

    2015-06-15

    Nanocomposite TiO2-SiO2 thin films with different compositions (from 0 to 100 mol% TiO2) were deposited by sol-gel dip-coating method on silicon substrate. Crystal structure, chemical bonding configuration, composition and morphology evolutions with composition were followed by Raman scattering, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy respectively. The refractive index and the extinction coefficient were derived in a broad band wavelength (250-900 nm) from spectroscopic ellipsometry data with high accuracy and correlated with composition and microstructure. Results showed an anatase structure for 100% TiO2 with a grain size in 6-10nm range. Whereas, the inclusion of SiO2 enlarges the optical band gap and suppresses the grain growth up to 4 nm in size. High TiO2 dispersion in SiO2 matrix was observed for all mixed materials. The refractive index (at λ=600 nm) increases linearly with composition from 1.48 (in 100% SiO2) to 2.22 (in 100% TiO2) leading to lower dense material, its dispersion being discussed in terms of the Wemple-DiDomenico single oscillator model. Hence, the optical parameters, such optical dispersion energies E0 and Ed, the average oscillators, strength S0 and wavelength λ0 and the ratio of the carrier concentration to the effective mass N/m(∗) have been derived. The analysis revealed a strong dependence on composition and structure. The optical response was also investigated in term of complex optical conductivity (σ) and both volume and surface energy loss functions (VELF and SELF).

  9. In vitro/in vivo evaluation of an optimized fast dissolving oral film containing olanzapine co-amorphous dispersion with selected carboxylic acids.

    Science.gov (United States)

    Maher, Eman Magdy; Ali, Ahmed Mahmoud Abdelhaleem; Salem, Heba Farouk; Abdelrahman, Ahmed Abdelbary

    2016-10-01

    Improvement of water solubility, dissolution rate, oral bioavailability, and reduction of first pass metabolism of OL (OL), were the aims of this research. Co-amorphization of OL carboxylic acid dispersions at various molar ratios was carried out using rapid solvent evaporation. Characterization of the dispersions was performed using differential scanning calorimetry (DSC), Fourier transform infrared spectrometry (FTIR), X-ray diffractometry (XRD), and scanning electron microscopy (SEM). Dispersions with highest equilibrium solubility were formulated as fast dissolving oral films. Modeling and optimization of film formation were undertaken using artificial neural networks (ANNs). The results indicated co-amorphization of OL-ascorbic acid through H-bonding. The co-amorphous dispersions at 1:2 molar ratio showed more than 600-fold increase in solubility of OL. The model optimized fast dissolving film prepared from the dispersion was physically and chemically stable, demonstrated short disintegration time (8.5 s), fast dissolution (97% in 10 min) and optimum tensile strength (4.9 N/cm(2)). The results of in vivo data indicated high bioavailability (144 ng h/mL) and maximum plasma concentration (14.2 ng/mL) compared with the marketed references. Therefore, the optimized co-amorphous OL-ascorbic acid fast dissolving film could be a valuable solution for enhancing the physicochemical and pharmacokinetic properties of OL.

  10. Gold film-catalysed benzannulation by Microwave-Assisted, Continuous Flow Organic Synthesis (MACOS

    Directory of Open Access Journals (Sweden)

    Gjergji Shore

    2009-07-01

    Full Text Available Methodology has been developed for laying down a thin gold-on-silver film on the inner surface of glass capillaries for the purpose of catalysing benzannulation reactions. The cycloaddition precursors are flowed through these capillaries while the metal film is being heated to high temperatures using microwave irradiation. The transformation can be optimized rapidly, tolerates a wide number of functional groups, is highly regioselective, and proceeds in good to excellent conversion.

  11. Electrical Capacitance Tomography Measurement of Flow Patterns and Film Thickness in a Thermosyphon

    Institute of Scientific and Technical Information of China (English)

    Jingtao LI; Qi CHEN; Xiangyuan DONG; Shi LIU

    2005-01-01

    An experimental study was performed to evaluate the suitability of using an electrical capacitance tomography (ECT) system to visualize the flow patterns, and to measure the film thickness of the annular flow in a two-phase closed thermosyphon (TPCT). The performance of the ECT system was examined over a range of flow conditions.The experimental data were compared with the visual observations and existing correlations. Results indicated that the ECT system, with the linear back projection (LBP) algorithm, could be used to give an on-line qualitative image of the flow patterns. The Landweber iteration algorithm with optimal step length was implemented off-line to reconstruct high-resolution images. Then, the images were analyzed to obtain the film thickness of the annular flow. The experimental data compared well with the Nusselt's equation in low vapor velocity range, but showed an increasing deficiency with the increase of vapor velocity.

  12. Optimally controlled heating of solid particles in a fluidised bed with a dispersive flow of the solid

    Directory of Open Access Journals (Sweden)

    Poświata Artur

    2016-03-01

    Full Text Available In this study the authors minimise the total process cost for the heating of solid particles in a horizontal fluidised bed by an optimal choice of the inlet heating gas temperature profile and the total gas flow. Solid particles flowed along the apparatus and were heated by a hot gas entering from the bottom of the fluidised apparatus. The hydrodynamics of the fluidised bed is described by a two-phase Kunii - Levenspiel model. We assumed that the gas was flowing only vertically, whereas solid particles were flowing horizontally and because of dispersion they could be additionally mixed up in the same direction. The mixing rate was described by the axial dispersion coefficient. As any economic values of variables describing analysing process are subject to local and time fluctuations, the accepted objective function describes the total cost of the process expressed in exergy units. The continuous optimisation algorithm of the Maximum Principle was used for calculations. A mathematical model of the process, including boundary conditions in a form convenient for optimisation, was derived and presented. The optimization results are presented as an optimal profile of inlet gas temperature. The influence of heat transfer kinetics and dispersion coefficients on optimal runs of the heating process is discussed. Results of this discussion constitute a novelty in comparison to information presented in current literature.

  13. Bifurcation in a thin liquid film flowing over a locally heated surface

    CERN Document Server

    Katkar, Harshwardhan H

    2014-01-01

    We investigate the non-linear dynamics of a two-dimensional film flowing down a finite heater, for a non-volatile and a volatile liquid. An oscillatory instability is predicted beyond a critical value of Marangoni number using linear stability theory. Continuation along the Marangoni number using non-linear evolution equation is used to trace bifurcation diagram associated with the oscillatory instability. Hysteresis, a characteristic attribute of a sub-critical Hopf bifurcation, is observed in a critical parametric region. The bifurcation is universally observed for both, a non-volatile film and a volatile film.

  14. [Hyperspectral Detection Model for Soil Dispersion in Zhouqu Debris Flow Source Region].

    Science.gov (United States)

    Wang, Qin-jun; Wei, Yong-ming; Chen, Yu; Chen, Jia-ge; Lin, Qi-zhong

    2016-02-01

    Sensitive band positions, models and the principles of soil dispersion detected by hyperspectral remote sensing were firstly discussed according to the results of soil dispersive hyperspectral remote sensing experiment. Results showed that, (1) signals and noises could be separated by Fourier transformation. A finely mineral identification system was developed to remove spectral noises and provide highly accurate data for establishing soil dispersive model; (2) Soil dispersive hyperspectral remote sensing model established by the multiple linear regression method was good at soil dispersion forecasting for the high correlation between sensitive bands and the soil dispersions. (3) According to mineral spectra, soil minerals and their absorbed irons were reflected by sensitive bands which revealed reasons causing soils to be dispersive. Sodium was the closest iron correlated with soil dispersion. The secondary was calcite, montmorillonite and illite. However, the correlation between soil dispersion and chlorite, kaolinite, PH value, quartz, potassium feldspar, plagioclase was weak. The main reason was probably that sodium was low in ionic valence, small ionic radius and strong hydration forces; calcite was high water soluble and illite was weak binding forces between two layers under high pH value.

  15. Rod-like particles matching algorithm based on SOM neural network in dispersed two-phase flow measurements

    Science.gov (United States)

    Abbasi Hoseini, Afshin; Zavareh, Zahra; Lundell, Fredrik; Anderson, Helge I.

    2014-04-01

    A matching algorithm based on self-organizing map (SOM) neural network is proposed for tracking rod-like particles in 2D optical measurements of dispersed two-phase flows. It is verified by both synthetic images of elongated particles mimicking 2D suspension flows and direct numerical simulations-based results of prolate particles dispersed in a turbulent channel flow. Furthermore, the potential benefit of this algorithm is evaluated by applying it to the experimental data of rod-like fibers tracking in wall turbulence. The study of the behavior of elongated particles suspended in turbulent flows has a practical importance and covers a wide range of applications in engineering and science. In experimental approach, particle tracking velocimetry of the dispersed phase has a key role together with particle image velocimetry of the carrier phase to obtain the velocities of both phases. The essential parts of particle tracking are to identify and match corresponding particles correctly in consecutive images. The present study is focused on the development of an algorithm for pairing non-spherical particles that have one major symmetry axis. The novel idea in the algorithm is to take the orientation of the particles into account for matching in addition to their positions. The method used is based on the SOM neural network that finds the most likely matching link in images on the basis of feature extraction and clustering. The fundamental concept is finding corresponding particles in the images with the nearest characteristics: position and orientation. The most effective aspect of this two-frame matching algorithm is that it does not require any preliminary knowledge of neither the flow field nor the particle behavior. Furthermore, using one additional characteristic of the non-spherical particles, namely their orientation, in addition to its coordinate vector, the pairing is improved both for more reliable matching at higher concentrations of dispersed particles and

  16. Pinning effects on flux flow instability in epitaxial Nb thin films

    Science.gov (United States)

    Dobrovolskiy, Oleksandr V.; Shklovskij, Valerij A.; Hanefeld, Marc; Zörb, Markus; Köhs, Lukas; Huth, Michael

    2017-08-01

    The flux flow properties of epitaxial niobium films with different pinning strengths are investigated by dc electrical resistance measurements and mapped to results derived within the framework of a theoretical model. The cases of weak random pinning in as-grown films, strong random pinning in Ga ion-irradiated films, and strong periodic pinning induced by a nanogroove array milled by a focused ion beam are investigated. The generic feature of the current-voltage curves of the films consists of instability jumps to the normal state at some instability current density j * as the vortex lattice reaches its critical velocity v *. While {v}* (B) monotonically decreases for as-grown films, the irradiated films exhibit a non-monotonic dependence {v}* (B) attaining a maximum in the low-field range. In the case of nanopatterned films, this broad maximum is accompanied by a much sharper maximum in both {v}* (B) and {j}* (B), which we attribute to the commensurability effect when the spacing between the vortex rows coincides with the location of the grooves. We argue that the observed behavior of {v}* (B) can be explained by the pinning effect on the vortex flow instability and support our claims by fitting the experimental data to theoretical expressions derived within a model accounting for the field dependence of the depinning current density.

  17. Turbulent flow mwasurements with a triple-split hot-film probe

    Science.gov (United States)

    Doiron, M. D.; Zingg, D. W.

    1994-09-01

    Complex turbulent shear flows occur in many aerospace applications, such as aerodynamic devices and gas turbine engines. Measurements of mean and fluctuating velocity components can greatly aid our understanding of such flows. Experimental data are particularly useful in assessing and validating turbulence models used in computational fluid dynamics codes. Velocity measurements are generally made using a pitot-static tube, a constant temperature hot-wire anemometer, or a laser Doppler anemometer (LDA). For separated turbulent flows, pitot-static tubes and conventional hot-wire probes are generally inapplicable. Because of the high cost of LDA measurements, modified hot-wire techniques have been developed which are suitable for reversed flows. These include pulsed hot wires and flying hot wires. Disadvantages of these approaches are discussed by Nakayama. Triple-split hot-film probes are a potentially useful alternative for velocity measurements in separated turbulent flows. Such probes typically consist of three separate films deposited on a cylinder. The operating principle is based on the variation of the local heat transfer coefficient on a cylinder with the magnitude and direction of the oncoming flow velocity. Most studies involving split-film anemometry have been with double-split hot-film probes. These operate on the same principle but retain the directional ambiguity of conventional hot wires and, hence, are not applicable to separated turbulent flows. The results of these studies indicate that split-film probes provide comparable accuracy to hot-wire probes for mean velocities but have a more limited frequency response. Despite their potential, especially for measurements of mean velocities, triple-split hot-film probes have received little use. The only example of their use known to the authors is reported by Modera, who used a triple-split probe for low-frequency reversed flow measurements over a 0 - 8 m/s flow speed range. The purpose of this Note is to

  18. Theory for source-responsive and free-surface film modeling of unsaturated flow

    Science.gov (United States)

    Nimmo, J.R.

    2010-01-01

    A new model explicitly incorporates the possibility of rapid response, across significant distance, to substantial water input. It is useful for unsaturated flow processes that are not inherently diffusive, or that do not progress through a series of equilibrium states. The term source-responsive is used to mean that flow responds sensitively to changing conditions at the source of water input (e.g., rainfall, irrigation, or ponded infiltration). The domain of preferential flow can be conceptualized as laminar flow in free-surface films along the walls of pores. These films may be considered to have uniform thickness, as suggested by field evidence that preferential flow moves at an approximately uniform rate when generated by a continuous and ample water supply. An effective facial area per unit volume quantitatively characterizes the medium with respect to source-responsive flow. A flow-intensity factor dependent on conditions within the medium represents the amount of source-responsive flow at a given time and position. Laminar flow theory provides relations for the velocity and thickness of flowing source-responsive films. Combination with the Darcy-Buckingham law and the continuity equation leads to expressions for both fluxes and dynamic water contents. Where preferential flow is sometimes or always significant, the interactive combination of source-responsive and diffuse flow has the potential to improve prediction of unsaturated-zone fluxes in response to hydraulic inputs and the evolving distribution of soil moisture. Examples for which this approach is efficient and physically plausible include (i) rainstorm-generated rapid fluctuations of a deep water table and (ii) space- and time-dependent soil water content response to infiltration in a macroporous soil. ?? Soil Science Society of America.

  19. Detection of H2O2 at a composite film modified electrode with highly dispersed Ag nanoparticles in Nafion

    Institute of Scientific and Technical Information of China (English)

    Mei Xiu Kan; Xue Ji Wang; Hui Min Zhang

    2011-01-01

    Ag nanoparticles were prepared by using the ion-exchange of Nafion combined with electrochemical reduction on the electrode. Ag nanoparticles are highly dispersed in Nafion film with an average size of 4.0 ± 0.2 nm. The amount of Ag nanoparticles can be readily controlled by the amount of Nafion coated on the electrode. Thus obtained Ag nanoparticles exhibit good catalytic activity for the reduction of H2O2 with a linear response to H2O2 in the concentration range of 0.04-8.0 mmol/L with a sensitivity of 0.34 μA/mmol/L and a detection limit of 1.0×10-8 mol/L.

  20. Stable Stratification Effects on Flow and Pollutant Dispersion in Boundary Layers Entering a Generic Urban Environment

    Science.gov (United States)

    Tomas, J. M.; Pourquie, M. J. B. M.; Jonker, H. J. J.

    2016-05-01

    Large-eddy simulations (LES) are used to investigate the effect of stable stratification on rural-to-urban roughness transitions. Smooth-wall turbulent boundary layers are subjected to a generic urban roughness consisting of cubes in an in-line arrangement. Two line sources of pollutant are added to investigate the effect on pollutant dispersion. Firstly, the LES method is validated with data from wind-tunnel experiments on fully-developed flow over cubical roughness. Good agreement is found for the vertical profiles of the mean streamwise velocity component and mean Reynolds stress. Subsequently, roughness transition simulations are done for both neutral and stable conditions. Results are compared with fully-developed simulations with conventional double-periodic boundary conditions. In stable conditions, at the end of the domain the streamwise velocity component has not yet reached the fully-developed state even though the surface forces are nearly constant. Moreover, the internal boundary layer is shallower than in the neutral case. Furthermore, an investigation of the turbulence kinetic energy budget shows that the buoyancy destruction term is reduced in the internal boundary layer, above which it is equal to the undisturbed (smooth wall) value. In addition, in stable conditions pollutants emitted above the urban canopy enter the canopy farther downstream due to decreased vertical mixing. Pollutants emitted below the top of the urban canopy are 85 % higher in concentration in stable conditions mostly due to decreased advection. If this is taken into account concentrations remain 17 % greater in stable conditions due to less rapid internal boundary-layer growth. Finally, it is concluded that in the first seven streets the vertical advective pollutant flux is significant, in contrast to the fully-developed case.

  1. Direct writing of conductive silver micropatterns on flexible polyimide film by laser-induced pyrolysis of silver nanoparticle-dispersed film

    Energy Technology Data Exchange (ETDEWEB)

    Aminuzzaman, Mohammod; Watanabe, Akira, E-mail: watanabe@tagen.tohoku.ac.jp; Miyashita, Tokuji [Tohoku University, Institute of Multidisciplinary Research for Advanced Materials (IMRAM) (Japan)

    2010-03-15

    This article describes fabrication of Ag micropatterns on a flexible polyimide (PI) film by laser direct writing using an Ag nanoparticle-dispersed film as a precursor. Ag micropatterns are characterized by optical microscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), surface profilometry, and resistivity measurements. The line width of Ag micropatterns can be effectively controlled by altering the experimental parameters of laser direct writing especially laser intensity, objective lens, and laser beam scanning speed etc. Using an objective lens of 100x and laser intensity of 170.50 kW/cm{sup 2}, Ag micropatterns with a line width of about 6 {mu}m have been achieved. The Ag micropatterns show strong adhesion to polyimide surface as evaluated by Scotch-tape test. The resistivity of the Ag micropatterns is determined to be 4.1 x 10{sup -6} {Omega} cm using two-point probe method. This value is comparable with the resistivity of bulk Ag (1.6 x 10{sup -6} {Omega} cm).

  2. An automatic, vigorous-injection assisted dispersive liquid-liquid microextraction technique for stopped-flow spectrophotometric detection of boron.

    Science.gov (United States)

    Alexovič, Michal; Wieczorek, Marcin; Kozak, Joanna; Kościelniak, Paweł; Balogh, Ioseph S; Andruch, Vasil

    2015-02-01

    A novel automatic vigorous-injection assisted dispersive liquid-liquid microextraction procedure based on the use of a modified single-valve sequential injection manifold (SV-SIA) was developed and applied for determination of boron in water samples. The major novelties in the procedure are the achieving of efficient dispersive liquid-liquid microextraction by means of single vigorous-injection (250 µL, 900 µL s(-1)) of the extraction solvent (n-amylacetate) into aqueous phase resulting in the effective dispersive mixing without using dispersive solvent and after self-separation of the phases, as well as forwarding of the extraction phase directly to a Z-flow cell (10 mm) without the use of a holding coil for stopped-flow spectrophotometric detection. The calibration working range was linear up to 2.43 mg L(-1) of boron at 426nm wavelength. The limit of detection, calculated as 3s of a blank test (n=10), was found to be 0.003 mg L(-1), and the relative standard deviation, measured as ten replicable concentrations at 0.41 mg L(-1) of boron was determined to be 5.6%. The validation of the method was tested using certified reference material.

  3. Quantifying oil degradation processes by flow, microbes and dispersant using digital holographic interferometry and micro-bioassay

    Science.gov (United States)

    Sheng, Jian; Jalali, Maryam; Brock, Larry

    2016-11-01

    The unceasing demand of hydrocarbons has led and will lead to the future events of releasing crude into marine environment like Deep Horizon oil spill. The burning question to scientific community after the spill was the fate of oil spill especially with high concentration of dispersant. It is found that various physical processes such as wind, wave, turbulence, compounded with dispersants, break oil into suspension of micro-droplets. It is widely accepted that dispersant reduces interfacial tension and results in increased surface to volume ratio and subsequently improve biodegradation. Due to complexity of oil composition, key mechanisms differ substantially from well-studied laboratory system, especially in the presence of other environmental factors such as flow shear and microbes. To investigate these mechanisms at oil water interface qualitatively, we have developed a micro-bioassay consisting of microfluidics with a substrate printed with oil droplet array and a digital holographic interferometer (DHI). The degradation of micro-droplets is evaluated with the change of shape and volume measured in real time by DHI at a 2-minute interval over 100 hours. Time resolved experiments are performed to study effects of droplet size, dispersant concentrations, flow shear, and different bacteria species on the rate of degradation. The details on the rate and mechanisms will be provided in the talk.

  4. Transitional dispersive scenarios driven by mesoscale flows on complex terrain under strong dry convective conditions

    Directory of Open Access Journals (Sweden)

    J. L. Palau

    2009-01-01

    Full Text Available By experimentation and modelling, this paper analyses the atmospheric dispersion of the SO2 emissions from a power plant on complex terrain under strong convective conditions, describing the main dispersion features as an ensemble of "stationary dispersive scenarios" and reformulating some "classical" dispersive concepts to deal with the systematically monitored summer dispersive scenarios in inland Spain. The results and discussions presented arise from a statistically representative study of the physical processes associated with the multimodal distribution of pollutants aloft and around a 343-m-tall chimney under strong dry convective conditions in the Iberian Peninsula. This paper analyses the importance of the identification and physical implications of transitional periods for air quality applications. The indetermination of a transversal plume to the preferred transport direction during these transitional periods implies a small (or null physical significance of the classical definition of horizontal standard deviation of the concentration distribution.

  5. Free convection film flows and heat transfer laminar free convection of phase flows and models for heat-transfer analysis

    CERN Document Server

    Shang, De-Yi

    2012-01-01

    This book presents recent developments in our systematic studies of hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, as well as accelerating film flow of non-Newtonian power-law fluids (FFNF). These new developments provided in this book are (i) novel system of analysis models based on the developed New Similarity Analysis Method; (ii) a system of advanced methods for treatment of gas temperature- dependent physical properties, and liquid temperature- dependent physical properties; (iii) the organically combined models of the governing mathematical models with those on treatment model of variable physical properties; (iv) rigorous approach of overcoming a challenge on accurate solution of three-point boundary value problem related to two-phase film boiling and condensation; and (v) A pseudo-similarity method of dealing with thermal boundary layer of FFNF for greatly simplifies the heat-transfer analysis and numerical calculati...

  6. Determination of optical constant and dispersion parameters of Se75Sb10In15 thin film characterized by wide band gap

    Science.gov (United States)

    Abd-Elrahman, M. I.; Abu-Sehly, A. A.; El-sonbaty, Sherouk Sh.; Hafiz, M. M.

    2017-02-01

    Chalcogenide Se75Sb10In15 thin films of different thickness (50-300 nm) are deposited using thermal evaporation technique. The thermogram of the chalcogenide bulk Se75Sb10In15 is obtained using a differential scanning calorimetry (DSC). The crystallization temperature T c, peak crystallization temperature T p and melting temperature T m, are identified. The X-ray diffraction (XRD) examination indicates the crystallinity of the as-deposited film decreases with increasing of thickness. Optical transmission and reflection spectra are recorded in the wavelength range of the incident photons from 250 to 2500 nm. It is found that the film thickness affects the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The absorption mechanism of the as-deposited films is a direct allowed transition. The optical band gap energy ( E g) decreases from 3.31 to 2.51 eV with increasing the film thickness from 50 to 300 nm. The behavior of E g is explained on the basis of the structure disorders in the thicker films. The effect of the film thickness on the single-oscillator and dispersion energies is studied by the dispersion analyses of the refractive index.

  7. Determination of optical constant and dispersion parameters of Se{sub 75}Sb{sub 10}In{sub 15} thin film characterized by wide band gap

    Energy Technology Data Exchange (ETDEWEB)

    Abd-Elrahman, M.I.; Abu-Sehly, A.A.; El-sonbaty, Sherouk Sh.; Hafiz, M.M. [Assiut University, Physics Department, Faculty of Science, Assiut (Egypt)

    2017-02-15

    Chalcogenide Se{sub 75}Sb{sub 10}In{sub 15} thin films of different thickness (50-300 nm) are deposited using thermal evaporation technique. The thermogram of the chalcogenide bulk Se{sub 75}Sb{sub 10}In{sub 15} is obtained using a differential scanning calorimetry (DSC). The crystallization temperature T{sub c}, peak crystallization temperature T{sub p} and melting temperature T{sub m}, are identified. The X-ray diffraction (XRD) examination indicates the crystallinity of the as-deposited film decreases with increasing of thickness. Optical transmission and reflection spectra are recorded in the wavelength range of the incident photons from 250 to 2500 nm. It is found that the film thickness affects the absorption coefficient, refractive index, extinction coefficient and the width of the tails of localized states in the gap region. The absorption mechanism of the as-deposited films is a direct allowed transition. The optical band gap energy (E{sub g}) decreases from 3.31 to 2.51 eV with increasing the film thickness from 50 to 300 nm. The behavior of E{sub g} is explained on the basis of the structure disorders in the thicker films. The effect of the film thickness on the single-oscillator and dispersion energies is studied by the dispersion analyses of the refractive index. (orig.)

  8. Imaging internal flows in a drying sessile polymer dispersion drop using Spectral Radar Optical Coherence Tomography (SR-OCT).

    Science.gov (United States)

    Manukyan, Selin; Sauer, Hans M; Roisman, Ilia V; Baldwin, Kyle A; Fairhurst, David J; Liang, Haida; Venzmer, Joachim; Tropea, Cameron

    2013-04-01

    In this work, we present the visualization of the internal flows in a drying sessile polymer dispersion drop on hydrophilic and hydrophobic surfaces with Spectral Radar Optical Coherence Tomography (SR-OCT). We have found that surface features such as the initial contact angle and pinning of the contact line, play a crucial role on the flow direction and final shape of the dried drop. Moreover, imaging through selection of vertical slices using optical coherence tomography offers a feasible alternative compared to imaging through selection of narrow horizontal slices using confocal microscopy for turbid, barely transparent fluids.

  9. Drift flux model as approximation of two fluid model for two phase dispersed and slug flow in tube

    Energy Technology Data Exchange (ETDEWEB)

    Nigmatulin, R.I.

    1995-09-01

    The analysis of one-dimensional schematizing for non-steady two-phase dispersed and slug flow in tube is presented. Quasi-static approximation, when inertia forces because of the accelerations of the phases may be neglected, is considered. Gas-liquid bubbly and slug vertical upward flows are analyzed. Non-trivial theoretical equations for slip velocity for these flows are derived. Juxtaposition of the derived equations for slip velocity with the famous Zuber-Findlay correlation as cross correlation coefficients is criticized. The generalization of non-steady drift flux Wallis theory taking into account influence of wall friction on the bubbly or slug flows for kinematical waves is considered.

  10. Amino-functionalized breath-figure cavities in polystyrene-alumina hybrid films: effect of particle concentration and dispersion.

    Science.gov (United States)

    V, Lakshmi; Raju, Annu; V G, Resmi; Pancrecious, Jerin K; T P D, Rajan; C, Pavithran

    2016-03-14

    We report the formation of breath-figure (BF) patterns with amino-functionalized cavities in a BF incompatible polystyrene (PS) by incorporating functionalized alumina nanoparticles. The particles were amphiphilic-modified and the modifier ratio was regulated to achieve a specific hydrophobic/hydrophilic balance of the particles. The influence of the physical and chemical properties of the particles like particle concentration, the hydrophobic/hydrophilic balance, etc., on particle dispersion in solvents having different polarity and the corresponding changes in the BF patterns have been studied. The amphiphilic-modified alumina particles could successfully assist the BF mechanism, generating uniform patterns in polystyrene films with the cavity walls decorated with the functionalized alumina particles, even from water-miscible solvents like THF. The possibility of fabricating free-standing micropatterned films by casting and drying the suspension under ambient conditions was also demonstrated. The present method opens up a simple route for producing functionalized BF cavities, which can be post-modified by a chemical route for various biological applications.

  11. Small-angle light scattering symmetry breaking in polymer-dispersed liquid crystal films with inhomogeneous electrically controlled interface anchoring

    Science.gov (United States)

    Loiko, V. A.; Konkolovich, A. V.; Zyryanov, V. Ya.; Miskevich, A. A.

    2017-03-01

    We have described the method of analyzing and reporting on the results of calculation of the small-angle structure of radiation scattered by a polymer-dispersed liquid crystal film with electrically controlled interfacial anchoring. The method is based on the interference approximation of the wave scattering theory and the hard disk model. Scattering from an individual liquid crystal droplet has been described using the anomalous diffraction approximation extended to the case of droplets with uniform and nonuniform interface anchoring at the droplet-polymer boundary. The director field structure in an individual droplet is determined from the solution of the problem of minimizing the volume density of the free energy. The electrooptical effect of symmetry breaking in the angular distribution of scattered radiation has been analyzed. This effect means that the intensities of radiation scattered within angles +θ s and-θ s relative to the direction of illumination in the scattering plane can be different. The effect is of the interference origin and is associated with asymmetry of the phase shift of the wavefront of an incident wave from individual parts of the droplet, which appears due to asymmetry of the director field structure in the droplet, caused by nonuniform anchoring of liquid crystal molecules with the polymer on its surface. This effect is analyzed in the case of normal illumination of the film depending on the interfacial anchoring at the liquid crystal-polymer interface, the orientation of the optical axes of droplets, their concentration, sizes, anisometry, and polydispersity.

  12. Small-angle light scattering symmetry breaking in polymer-dispersed liquid crystal films with inhomogeneous electrically controlled interface anchoring

    Energy Technology Data Exchange (ETDEWEB)

    Loiko, V. A., E-mail: loiko@ifanbel.bas-net.by; Konkolovich, A. V. [National Academy of Sciences of Belarus, Stepanov Institute of Physics (Belarus); Zyryanov, V. Ya. [Russian Academy of Sciences, Kirensky Institute of Physics, Federal Research Center “Krasnoyarsk Scientific Center,” Siberian Branch (Russian Federation); Miskevich, A. A. [National Academy of Sciences of Belarus, Stepanov Institute of Physics (Belarus)

    2017-03-15

    We have described the method of analyzing and reporting on the results of calculation of the small-angle structure of radiation scattered by a polymer-dispersed liquid crystal film with electrically controlled interfacial anchoring. The method is based on the interference approximation of the wave scattering theory and the hard disk model. Scattering from an individual liquid crystal droplet has been described using the anomalous diffraction approximation extended to the case of droplets with uniform and nonuniform interface anchoring at the droplet–polymer boundary. The director field structure in an individual droplet is determined from the solution of the problem of minimizing the volume density of the free energy. The electrooptical effect of symmetry breaking in the angular distribution of scattered radiation has been analyzed. This effect means that the intensities of radiation scattered within angles +θ{sub s} and–θ{sub s} relative to the direction of illumination in the scattering plane can be different. The effect is of the interference origin and is associated with asymmetry of the phase shift of the wavefront of an incident wave from individual parts of the droplet, which appears due to asymmetry of the director field structure in the droplet, caused by nonuniform anchoring of liquid crystal molecules with the polymer on its surface. This effect is analyzed in the case of normal illumination of the film depending on the interfacial anchoring at the liquid crystal–polymer interface, the orientation of the optical axes of droplets, their concentration, sizes, anisometry, and polydispersity.

  13. Glucose biosensor based on functionalized ZnO nanowire/graphite films dispersed on a Pt electrode

    Science.gov (United States)

    Gallay, P.; Tosi, E.; Madrid, R.; Tirado, M.; Comedi, D.

    2016-10-01

    We present a glucose biosensor based on ZnO nanowire self-sustained films grown on compacted graphite flakes by the vapor transport method. Nanowire/graphite films were fragmented in water, filtered to form a colloidal suspension, subsequently functionalized with glucose oxidase and finally transferred to a metal electrode (Pt). The obtained devices were evaluated using scanning electron microscopy, energy-dispersive x-ray spectroscopy, cyclic voltammetry and chronoamperometry. The electrochemical responses of the devices were determined in buffer solutions with successive glucose aggregates using a tripolar electrode system. The nanostructured biosensors showed excellent analytical performance, with linear response to glucose concentrations, high sensitivity of up to ≈17 μA cm-2 mM-1 in the 0.03-1.52 mM glucose concentration range, relatively low Michaelis-Menten constant, excellent reproducibility and a fast response. The detection limits are more than an order of magnitude lower than those achievable in commercial biosensors for glucose control, which is promising for the development of glucose monitoring methods that do not require blood extraction from potentially diabetic patients. The strong detection enhancements provided by the functionalized nanostructures are much larger than the electrode surface-area increase and are discussed in terms of the physical and chemical mechanisms involved in the detection and transduction processes.

  14. Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

    Science.gov (United States)

    Braman, K. E.; Ruf, J. H.

    2015-01-01

    Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated using RANS and URANS for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and for four approximations of the supersonic film injection geometry, each of which was created with a different simplification of the test article geometry. The results show that although a reasonable match to experiment can be obtained with varying levels of geometric fidelity, the modeling choices made do not fully represent the physics of flow separation in a TIC nozzle with film cooling.

  15. Measurement and simulation of the turbulent dispersion of a radioactive tracer in a two-phase flow system

    Energy Technology Data Exchange (ETDEWEB)

    Hensel, F.; Rohde, U.

    1998-10-01

    The turbulent dispersion of a radiotracer in an experimental setup with a natural convection liquid-gaseous flow was investigated. A liquid-gaseous bubbly flow was generated in a narrow tank by injection of pressurized air into water or by catalytic disintegration of H{sub 2}O{sub 2}. Turbulent Prandtl numbers for gas and tracer dispersion were varied. In the case of higher gas superficial velocities (J{sub gas}{approx}5-15 mm/s), a reasonable agreement was achieved between calculated and measured tracer transport velocity and dispersion coefficient values. A nearly linear correlation between j{sub gas} and D was found in agreement with other authors. The calculation results contribute to a better understanding of the phenomena and interpretation of the measurement results as well as to the validation of the CFD code for turbulent two-phase flow applications. Further investigations are necessary to improve the agreement in the cases of H{sub 2}O{sub 2} disintegration and low gas superficial velocities. (orig.)

  16. Experimental analysis and flow visualization of a thin liquid film on a stationary and rotating disk

    Science.gov (United States)

    Thomas, S.; Faghri, A.; Hankey, W.

    1991-01-01

    The mean thickness of a thin liquid film of deionized water with a free surface on a stationary and rotating horizontal disk has been measured with a nonobtrusive capacitance technique. The measurements were taken when the rotational speed ranged from 0-300 rpm and the flow rate varied from 7.0-15.0 lpm. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. When the disk was stationary, a circular hydraulic jump was present on the disk. Upstream from the jump, the film thickness was determined by the inertial and frictional forces on the fluid, and the radial spreading of the film. The surface tension at the edge of the disk affected the film thickness downstream from the jump. For the rotating disk, the film thickness was dependent upon the inertial and frictional forces near the center of the disk and the centrifugal forces near the edge of the disk.

  17. Multi-layer film flow down an inclined plane: experimental investigation

    KAUST Repository

    Henry, Daniel

    2014-11-19

    We report the results from an experimental study of the flow of a film down an inclined plane where the film itself is comprised of up to three layers of different liquids. By measuring the total film thickness for a broad range of parameters including flow rates and liquid physical properties, we provide a thorough and systematic test of the single-layer approximation for multi-layer films for Reynolds numbers Re = ρQ/μ≈0.03-60. In addition, we also measure the change in film thickness of individual layers as a function of flow rates for a variety of experimental configurations. With the aid of high-speed particle tracking, we derive the velocity fields and free-surface velocities to compare to the single-layer approximation. Furthermore, we provide experimental evidence of small capillary ridge formations close to the point where two layers merge and compare our experimental parameter range for the occurrence of this phenomenon to those previously reported.

  18. Effect of decomposition and organic residues on resistivity of copper films fabricated via low-temperature sintering of complex particle mixed dispersions.

    Science.gov (United States)

    Yong, Yingqiong; Nguyen, Mai Thanh; Tsukamoto, Hiroki; Matsubara, Masaki; Liao, Ying-Chih; Yonezawa, Tetsu

    2017-03-24

    Mixtures of a copper complex and copper fine particles as copper-based metal-organic decomposition (MOD) dispersions have been demonstrated to be effective for low-temperature sintering of conductive copper film. However, the copper particle size effect on decomposition process of the dispersion during heating and the effect of organic residues on the resistivity have not been studied. In this study, the decomposition process of dispersions containing mixtures of a copper complex and copper particles with various sizes was studied. The effect of organic residues on the resistivity was also studied using thermogravimetric analysis. In addition, the choice of copper salts in the copper complex was also discussed. In this work, a low-resistivity sintered copper film (7 × 10(-6) Ω·m) at a temperature as low as 100 °C was achieved without using any reductive gas.

  19. Flow of a thin liquid film coating a horizontal stationary cylinder.

    Science.gov (United States)

    Cachile, M; Aguirre, M A; Lenschen, M; Calvo, A

    2013-12-01

    An experimental and theoretical study of the flow of liquid films around a stationary horizontal cylinder is reported. The film presents two different behaviors: The flow is stable in the upper zone (up to ∼150° with the vertical) and Rayleigh-Taylor-like instabilities appear in the lower zone. For the stable region, film thickness evolution could be described by numerically integrating an evolution equation obtained using a lubrication approximation. For the unstable region, a linear stability analysis allows us to determine the maximum growth wavelength for the Rayleigh-Taylor instability. Approximate analytical solutions were obtained for generatrices at an angle with the vertical θ=0 (stable region) and θ=π (where the instability appears).

  20. Mixed convection film condensation from downward flowing vapors onto a sphere with variable wall temperature

    Science.gov (United States)

    Hsu, C.-H.; Yang, S.-A.

    A model is developed for the study of mixed- convection film condensation from downward flowing vapors onto a sphere with variable wall temperature. The model combined natural convection dominated and forced convection dominated film condensation, concerning effects of pressure gradient (P), interfacial vapor shear drag and non-uniform wall temperature variation (A), has been investigated and solved numerically. The effect of pressure gradient on the dimensionless mean heat transfer, NuRe-1/2 will remain almost uniform with increasing P until P={2 / 9} F for various corresponding available values of F. Meanwhile, the dimensionless mean heat transfer, NuRe-1/2 is increasing significantly with F for its corresponding available values of P. Although the non-uniform wall temperature variation has an appreciable influence on the local film flow and heat transfer; however, the dependence of mean heat transfer on A can be almost negligible.

  1. A Cahn-Hilliard framework for thin-film flows in the partial-wetting regime

    Science.gov (United States)

    Pahlavan, A. A.; Chen, M.; Cueto-Felgueroso, L.; McKinley, G. H.; Juanes, R.

    2014-12-01

    Traditional mathematical descriptions of multiphase flow in porous media rely on a multiphase extension of Darcy's law, and lead to nonlinear second-order (advection-diffusion) partial differential equations for fluid saturations. Here, we study horizontal redistribution of immiscible fluids. The traditional Darcy-flow model predicts that the spreading of a finite amount of liquid in a horizontal porous medium never stops; a prediction that is not substantiated by observation. To help guide the development of new models of multiphase flow in porous media [1], we draw an analogy with the flow of thin films. The flow of thin films over flat surfaces has been the subject of much theoretical, experimental and computational research [2]. Under the lubrication approximation, the classical mathematical model for these flows takes the form of a nonlinear fourth-order PDE, where the fourth-order term models the effect of surface tension [3]. This classical model, however, effectively assumes that the film is perfectly wetting to the substrate and, therefore, does not capture the partial wetting regime. Partial wetting is responsible for stopping the spread of a liquid puddle. Here, we present experiments of (large-volume) liquid spreading over a flat horizontal substrate in the partial wetting regime, and characterize the spreading regimes that we observe. We extend our previous theoretical work of two-phase flow in a capillary tube [4], and develop a macroscopic phase-field model of thin-film flows with partial wetting. Our model naturally accounts for the dynamic contact angle at the contact line, and therefore permits modeling thin-film flows without invoking a precursor film, leading to compactly-supported solutions that reproduce the spreading dynamics and the static equilibrium configuration observed in the experiments. We anticipate that this modeling approach will provide a natural mathematical framework to describe spreading and redistribution of immiscible fluids

  2. Thin layer flow and film decay modeling for grease lubricated rolling bearings

    NARCIS (Netherlands)

    Venner, Cornelis H.; van Zoelen, M.T.; Lugt, Pieter Martin

    2012-01-01

    A model is presented to predict lubricant supply layer changes on tracks in rolling bearings due to centrifugal forces and elastohydrodynamic contact pressure. Experimental validation is shown for centrifugal force driven free surface flow, and layer thickness (film thickness) decay in single elasto

  3. Burnout and distribution of liquid between the flow core and wall films in narrow slot channels

    Science.gov (United States)

    Boltenko, E. A.; Shpakovskii, A. A.

    2010-03-01

    Previous works on studying distribution of liquid between the flow core and wall films in narrow slot channels are briefly reviewed. Interrelation between mass transfer processes and burnout is shown. A procedure for calculating burnout on convex and concave heat-transfer surfaces in narrow slot channels is presented.

  4. Vortex wakes of a flapping foil in a flowing soap film

    DEFF Research Database (Denmark)

    We present an experimental study of an oscillating, symmetric foil in a vertically flowing soap film. By varying frequency and amplitude of the oscillation we explore and visualize a variety of wake structures, including von K´arm´an wake, reverse von K´arm´an wake, 2P wake, and 2P+2S wake. We...

  5. Aggregation of cationic p-phenylene ethynylenes on Laponite clay in aqueous dispersions and solid films.

    Science.gov (United States)

    Hill, Eric H; Zhang, Yue; Whitten, David G

    2015-07-01

    Previous studies of cationic p-phenylene ethynylenes oligomers (OPEs) have revealed strong antimicrobial activity and strong photophysical changes upon their aggregation that can be utilized for sensing various chemicals and biomolecules. In this article, the adsorption of two types of OPEs with different placement of charged groups onto the synthetic clay Laponite is studied, and the changes to photophysical properties, photochemical degradation efficiency, and biocidal effectiveness are determined. In addition to solution-phase studies, the material and biocidal properties of solid films formed from the OPE-Laponite complex were assessed. The results of this study suggest that OPEs aggregate on Laponite and induce aggregation between Laponite discs, leading to drastic changes to their photophysical and material properties. Solid OPE-Laponite films were shown to have fair resistance to dissolution in aqueous solution compared with Laponite alone, and adhesion and minor killing of both Gram-negative and Gram-positive bacteria on the surface was observed. The results of this study give insight into controlling the colloidal phases of Laponite via molecular aggregation, may be useful for development of sensors and biocides involving Laponite as a scaffold, and lead to further control over slow-release and surface interactions of biocidal materials.

  6. Effect of the oxygen flow rate on the structure and the properties of Ag-Cu-O sputtered films deposited using a Ag/Cu target with eutectic composition

    Energy Technology Data Exchange (ETDEWEB)

    Pierson, J.F. [Laboratoire de Science et Genie des Surfaces (UMR CNRS 7570), Ecole des Mines, Parc de Saurupt, CS 14234, 54042 Nancy Cedex (France)], E-mail: jean-francois.pierson@mines.inpl-nancy.fr; Rolin, E.; Clement-Gendarme, C.; Petitjean, C.; Horwat, D. [Laboratoire de Science et Genie des Surfaces (UMR CNRS 7570), Ecole des Mines, Parc de Saurupt, CS 14234, 54042 Nancy Cedex (France)

    2008-08-15

    Ag-Cu-O films were deposited on glass substrates by reactive sputtering of a composite Ag{sub 60}Cu{sub 40} target in various Ar-O{sub 2} mixtures. The films were characterised by energy dispersive X-ray analysis, X-ray diffraction, UV-visible spectroscopy and using the four point probe method. The structure of the films is strongly dependent on the oxygen flow rate introduced in the deposition chamber. The variation of the oxygen flow rate allows the deposition of the following structures: Ag-Cu-(O) solid solution, nc-Ag + nc-Cu{sub 2}O, nc-Ag + nc-(Ag,Cu){sub 2}O and finally X-ray amorphous. UV-visible reflectance measurements confirm the occurrence of metallic silver into the deposited films. The increase of the oxygen flow rate induces a continuous increase of the film oxygen concentration that can be correlated to the evolution of the film reflectance and the film electrical resistivity. Finally, the structural changes vs. the oxygen content are discussed in terms of reactivity of sputtered atoms with oxygen.

  7. Numerical and experimental modeling of liquid metal thin film flows in a quasi-coplanar magentic field

    Energy Technology Data Exchange (ETDEWEB)

    Morley, Neil B. [Univ. of California, Los Angeles, CA (United States)

    1994-01-01

    Liquid metal film protection of plasma-facing surfaces in fusion reactors is proposed in an effort to counter the adverse effects of high heat and particle fluxes from the burning plasma. Concerns still exist about establishing the required flow in presence of strong magnetic fields and plasma momentum flux typical of a reactor environment. In this work, the flow behavior of the film is examined under such conditions. Analysis of MHD equations as they apply to liquid metal flows with a free surface in the fully-developed limit was undertaken. Solution yields data for velocity profiles and uniform film heights vs key design parameters (channel size, magnetic field magnitude/orientation, channel slope, wall conductivity). These results are compared to previous models to determine accuracy of simplifying assumptions, in particular Hartmann averaging of films along {rvec B}. Effect of a plasma momentum flux on the thin films is also analyzed. The plasma momentum is strong enough in the cases examined to seriously upset the film, especially for lighter elements like Li. Ga performed much better and its possible use is bolstered by calculations. In an experiment in the MeGA-loop MHD facility, coplanar, wide film flow was found to be little affected by the magnetic field due to the elongated nature of the film. Both MHD drag and partial laminarization are observed, supporting the fully- developed film model predictions of the onset of MHD drag and duct flow estimations for flow laminarization.

  8. Dispersive shock waves in Bose-Einstein condensates and nonlinear nano-oscillators in ferromagnetic thin films

    Science.gov (United States)

    Hoefer, Mark A.

    This thesis examines nonlinear wave phenomena, in two physical systems: a Bose-Einstein condensate (BEC) and thin film ferromagnets where the magnetization dynamics are excited by the spin momentum transfer (SMT) effect. In the first system, shock waves generated by steep gradients in the BEC wavefunction are shown to be of the disperse type. Asymptotic and averaging methods are used to determine shock speeds and structure in one spatial dimension. These results are compared with multidimensional numerical simulations and experiment showing good, qualitative agreement. In the second system, a model of magnetization dynamics due to SMT is presented. Using this model, nonlinear oscillating modes---nano-oscillators---are found numerically and analytically using perturbative methods. These results compare well with experiment. A Bose-Einstein condensate (BEC) is a quantum fluid that gives rise to interesting shock wave nonlinear dynamics. Experiments depict a BEC that exhibits behavior similar to that of a shock wave in a compressible gas, e.g. traveling fronts with steep gradients. However, the governing Gross-Pitaevskii (GP) equation that describes the mean field of a BEC admits no dissipation hence classical dissipative shock solutions do not explain the phenomena. Instead, wave dynamics with small dispersion is considered and it is shown that this provides a mechanism for the generation of a dispersive shock wave (DSW). Computations with the GP equation are compared to experiment with excellent agreement. A comparison between a canonical 1D dissipative and dispersive shock problem shows significant differences in shock structure and shock front speed. Numerical results associated with laboratory experiments show that three and two-dimensional approximations are in excellent agreement and one dimensional approximations are in qualitative agreement. The interaction of two DSWs is investigated analytically and numerically. Using one dimensional DSW theory it is argued

  9. The flow of a thin liquid film on a stationary and rotating disk. II - Theoretical prediction

    Science.gov (United States)

    Rahman, M. M.; Faghri, A.; Hankey, W. L.

    1990-01-01

    The existing theoretical models are improved and a systematic procedure to compute the free surface flow of a thin liquid film is suggested. The solutions for axisymmetric radial flow on a stationary horizontal disk and for the disk rotating around its axis are presented. The theoretical predictions are compared with the experimental data presented in Part I of this report. The analysis shows results for both supercritical and subcritical flows and the flow structure in the vicinity of a hydraulic jump which isolates these two flow types. The detailed flow structure in a hydraulic jump was computed and shown to contain regions of separation including a 'surface roller'. The effects of surface tension are found to be important near the outer edge of the disk where the fluid experiences a free fall. At other locations, the surface tension is negligible. For a rotating disk, the frictional resistance in the angular direction is found to be as important as that in the radial direction.

  10. Effect of acetylene flow rate on morphology and structure of carbon nanotube thick films grown by thermal chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    CAO Zhangyi; SUN Zhuo; GUO Pingsheng; CHEN Yiwei

    2007-01-01

    Carbon nanotube (CNT) films were grown on nickel foil substrates by thermal chemical vapor deposition (CVD) with acetylene and hydrogen as the precursors. The morphology and structure of CNTs depending on the acetylene flow rate were characterized by a scanning electron microscope (SEM),a transmission electron microscope (TEM) and a Raman spectrometer,respectively.The effect of acetylene flow rate on the morphology and structure of CNT films was investigated.By increasing the acetylene flow rate from 10 to 90 sccm (standard cubic centimeter perminute),the yield and the diameter of CNTs increase.Also, the defects and amorphous phase in CNT films increase with increasing acetylene flow rate.

  11. Effect of oxygen flow on the structure and optical properties of the Gd2O3 optical films

    Science.gov (United States)

    Wang, Siyu; Ma, Ping; Pu, Yunti; Qiao, Zhao; Zhang, Mingxiao; Lu, Zhongwen; Peng, Dongxu

    2016-10-01

    Gd2O3 thin films were deposited by Ion-beam sputtering (IBS) under the oxygen flow of 0 sccm~30 sccm. The structure and optical properties of the Gd2O3 optical films were investigated by Lambdar950 spectrophotometer, laser calorimetry and atomic force microscopy (AFM). When oxygen flow was less than 10 sccm, with the increase of oxygen flow, the transmittance of the films increased, at the same time absorptance and the surface roughness of the films decreased. While the flow was more than 10 sccm, with the increase of the flow rate, the surface roughness of the films increased, but the transmittance and absorptance did not show any apparent change. The results show that both the structure and optical properties are closely related to the flow of oxygen. XPS measurements demonstrated that when the oxygen flow increase from 0 sccm to 10 sccm, the defect oxygen decreases. But when the oxygen flow increase from 10 sccm to 30 sccm, the defect oxygen increase. The XPS spectra show that when the oxygen flow was 10 sccm, the defect oxygen was the least. Thus when the oxygen flow was 10 sccm, the structure and optical properties of the Gd2O3 optical films were the best.

  12. Filming the invisible - time-resolved visualization of compressible flows

    Science.gov (United States)

    Kleine, H.

    2010-04-01

    Essentially all processes in gasdynamics are invisible to the naked eye as they occur in a transparent medium. The task to observe them is further complicated by the fact that most of these processes are also transient, often with characteristic times that are considerably below the threshold of human perception. Both difficulties can be overcome by combining visualization methods that reveal changes in the transparent medium, and high-speed photography techniques that “stop” the motion of the flow. The traditional approach is to reconstruct a transient process from a series of single images, each taken in a different experiment at a different instant. This approach, which is still widely used today, can only be expected to give reliable results when the process is reproducible. Truly time-resolved visualization, which yields a sequence of flow images in a single experiment, has been attempted for more than a century, but many of the developed camera systems were characterized by a high level of complexity and limited quality of the results. Recent advances in digital high-speed photography have changed this situation and have provided the tools to investigate, with relative ease and in sufficient detail, the true development of a transient flow with characteristic time scales down to one microsecond. This paper discusses the potential and the limitations one encounters when using density-sensitive visualization techniques in time-resolved mode. Several examples illustrate how this approach can reveal and explain a number of previously undetected phenomena in a variety of highly transient compressible flows. It is demonstrated that time-resolved visualization offers numerous advantages which normally outweigh its shortcomings, mainly the often-encountered loss in resolution. Apart from the capability to track the location and/or shape of flow features in space and time, adequate time-resolved visualization allows one to observe the development of deliberately

  13. Controlling flux flow dissipation by changing flux pinning in superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Grimaldi, G.; Leo, A.; Nigro, A.; Pace, S. [CNR SPIN Salerno and Dipartimento di Fisica ' ' E. R. Caianiello' ' , Universita degli Studi di Salerno, via Ponte Don Melillo, 84084 Fisciano (Italy); Silhanek, A. V. [Department de Physique, Universite de Liege, B-4000 Sart Tilman (Belgium); INPAC-Institute for Nanoscale Physics and Chemistry, Nanoscale Superconductivity and Magnetism Group, K. U. Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Verellen, N.; Moshchalkov, V. V. [INPAC-Institute for Nanoscale Physics and Chemistry, Nanoscale Superconductivity and Magnetism Group, K. U. Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Milosevic, M. V. [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Casaburi, A.; Cristiano, R. [Istituto di Cibernetica ' ' E. Caianiello' ' , CNR, 80078 Pozzuoli (Italy)

    2012-05-14

    We study the flux flow state in superconducting materials characterized by rather strong intrinsic pinning, such as Nb, NbN, and nanostructured Al thin films, in which we drag the superconducting dissipative state into the normal state by current biasing. We modify the vortex pinning strength either by ion irradiation, by tuning the measuring temperature or by including artificial pinning centers. We measure critical flux flow voltages for all materials and the same effect is observed: switching to low flux flow dissipations at low fields for an intermediate pinning regime. This mechanism offers a way to additionally promote the stability of the superconducting state.

  14. Wake structure of an oscillating cylinder in a flowing soap film

    Science.gov (United States)

    Stremler, Mark; Yang, Wenchao

    2016-11-01

    When a circular cylinder oscillates with respect to a uniform background flow, a variety of wake patterns can be observed in which multiple vortices are generated during each shedding cycle. Thorough investigations of the possible wake patterns behind a cylinder undergoing forced oscillations have been conducted by C.H.K. Williamson using two-dimensional characterization of a three-dimensional flow. Attempts to reproduce the structural bifurcations using two-dimensional computational models have been only moderately successful. A flowing soap film, an experimental system with quasi-two-dimensional flow, provides an alternative method for investigating the role of system dimensionality in the structure and dynamics of complex vortex wakes. Wake patterns are observed directly through interference fringes caused by thickness variations in the soap film. Such systems have been used for decades to visualize wake structure, but they have not previously been used to conduct an analog of Williamson's work. We will discuss the results of an ongoing parametric study of the wake structure produced by a circular cylinder undergoing forced oscillations transverse to the background flow in an inclined soap film system.

  15. Numerical Analysis of Supersonic Film Cooling in Supersonic Flow in Hypersonic Inlet with Isolator

    Directory of Open Access Journals (Sweden)

    Silong Zhang

    2014-02-01

    Full Text Available Supersonic film cooling is an efficient method to cool the engine with extremely high heat load. In order to study supersonic film cooling in a real advanced engine, a two-dimensional model of the hypersonic inlet in a scramjet engine with supersonic film cooling in the isolator is built and validated through experimental data. The simulation results show that the cooling effect under different coolant injection angles does not show clear differences; a small injection angle can ensure both the cooling effect and good aerodynamic performances (e.g., flow coefficient of the hypersonic inlet. Under selected coolant injection angle and inlet Mach number, the cooling efficiency increases along with the injection Mach number of the coolant flow, only causing a little total pressure loss in the isolator. Along with the increase of the inlet Mach number of the hypersonic inlet, the cooling efficiency does not present a monotonic change because of the complex shock waves. However, the wall temperature shows a monotonic increase when the inlet Mach number increases. The mass flow rate of coolant flow should be increased to cool the engine more efficiently according to the mass flow rate of the main stream when the inlet Mach number increases.

  16. Estimating dispersal and gene flow in the neotropical freshwater turtle Hydromedusa maximiliani (Chelidae by combining ecological and genetic methods

    Directory of Open Access Journals (Sweden)

    Souza Franco L.

    2002-01-01

    Full Text Available Hydromedusa maximiliani is a vulnerable neotropical freshwater turtle endemic to mountainous regions of the Atlantic rainforest in southeastern Brazil. Random amplified polymorphic DNA (RAPD was used to estimate the gene flow and dispersal for individuals inhabiting rivers and streams within a drainage. Nine primers generated 27 scoreable bands, of which 9 (33% were polymorphic and produced 12 RAPD phenotypes. The gene flow estimates (Nm among turtles inhabiting different rivers and streams were variable, ranging from 0.09 to 3.00 (mean: 0.60. For some loci, the rates of gene flow could offset population differentiation (Nm > 1, whereas for others random genetic drift could result in population divergence (Nm < 1. Since the genetic variation of this turtle seems to be structured according to the natural hierarchical system of rivers and streams within drainages, management programs involving translocations between different regions across the geographical range of H. maximiliani should be viewed with caution.

  17. Dispersion in the large-deviation regime. Part II: cellular flow at large P\\'eclet number

    CERN Document Server

    Haynes, P H

    2014-01-01

    A standard model for the study of scalar dispersion through advection and molecular diffusion is a two-dimensional periodic flow with closed streamlines inside periodic cells. Over long time scales, the dispersion of a scalar in this flow can be characterised by an effective diffusivity that is a factor $\\mathrm{Pe}^{1/2}$ larger than molecular diffusivity when the P\\'eclet number $\\mathrm{Pe}$ is large. Here we provide a more complete description of dispersion in this regime by applying the large-deviation theory developed in Part I of this paper. We derive approximations to the rate function governing the scalar concentration at large time $t$ by carrying out an asymptotic analysis of the relevant family of eigenvalue problems. We identify two asymptotic regimes and make predictions for the rate function and spatial structure of the scalar. Regime I applies to distances from the release point that satisfy $|\\boldsymbol{x}| = O(\\mathrm{Pe}^{1/4} t)$ . The concentration in this regime is isotropic at large sc...

  18. Study on heat transfer for falling liquid film flow with consideration of interfacial evaporation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The interfacial evaporative heat transfer was included in the semi-empirical study of the heat transfer for the falling liquid film flow. The investigations showed that, the inclusion of the interfacial evaporative heat transfer in the turbulent model would lower the predicted convective heat transfer coefficient. Predictions of the new model resulted in a prominent deviation from that predictions of the normal model in the case of large mass flow rate and low wall heat flux. This deviation will be decreased with increasing wall heat flux, such that it will be asymptotic zero at very high wall heat flux. Predictions of the new model agreed well with the current experimental measurements. This study has verified that the Reynolds number is not the sole crucial parameter for heat transfer of falling liquid film flow, and wall heat flux will be another important independent parameter. This result is consistent with our previous studies.

  19. Stabilising falling liquid film flows using feedback control

    CERN Document Server

    Thompson, Alice B; Pavliotis, Grigorios A; Papageorgiou, Demetrios T

    2015-01-01

    The flow of a fluid layer with one interface exposed to the air and the other an inclined planar wall becomes unstable due to inertial effects when the fluid layer is sufficiently thick or the slope sufficiently steep. This free surface flow of a single fluid layer has industrial applications including coating and heat transfer, which benefit from smooth and wavy interfaces, respectively. Here we discuss how the dynamics of the system are altered by introducing deliberately spatially-varying or time-dependent perturbations via the injection and suction of fluid through the wall. We find that injection and suction is a remarkably effective control mechanism: the controls can be used to drive the system towards arbitrary steady states and travelling waves, and the qualitative effects are independent of the details of the flow modelling. Furthermore, the system can still be successfully controlled even if the feedback must be applied via a set of localised actuators, and only a small number of system observation...

  20. Lubricant film flow and depletion characteristics at head/disk storage interface

    Science.gov (United States)

    Ao, Hong-Rui; Han, Zhi-Ying; Zhang, Kai; Jiang, Hong-Yuan

    2016-12-01

    The characteristics of lubricant film at head/disk interface (HDI) are essential to the stability of hard disk drives. In this study, the theoretical models of the lubricant flow and depletion are deduced based on Navier-Stokes (NS) and continuity equations. The air bearing pressure on the surface of the lubrication film is solved by the modified Reynolds equation based on Fukui and Kaneko (FK) model. Then the lubricant film deformations for a plane slider and double-track slider are obtained. The equation of lubricant film thickness is deduced with the consideration of van der Waals force, the air bearing pressure, the surface tension, and the external stresses. The lubricant depletion under heat source is simulated and the effects of different working conditions including initial thickness, flying height and the speed of the disk on lubricant depletion are discussed. The main factors that cause the lubricant flow and depletion are analyzed and the ways to reduce the film thickness deformation are proposed. The simulation results indicate that the shearing stress is the most important factor that causes the thickness deformation and other terms listed in the equation have little influence. The thickness deformation is dependent on the working parameter, and the thermal condition evaporation is the most important factor. Project supported by the National Natural Science Foundation of China (Grant No. 51275124).

  1. Thin-Film Air-Mass-Flow Sensor of Improved Design Developed

    Science.gov (United States)

    Fralick, Gustave C.; Wrbanek, John D.; Hwang, Danny P.

    2003-01-01

    Researchers at the NASA Glenn Research Center have developed a new air-mass-flow sensor to solve the problems of existing mass flow sensor designs. NASA's design consists of thin-film resistors in a Wheatstone bridge arrangement. The resistors are fabricated on a thin, constant-thickness airfoil to minimize disturbance to the airflow being measured. The following photograph shows one of NASA s prototype sensors. In comparison to other air-mass-flow sensor designs, NASA s thin-film sensor is much more robust than hot wires, causes less airflow disturbance than pitot tubes, is more accurate than vane anemometers, and is much simpler to operate than thermocouple rakes. NASA s thin-film air-mass-flow sensor works by converting the temperature difference seen at each leg of the thin-film Wheatstone bridge into a mass-flow rate. The following figure shows a schematic of this sensor with air flowing around it. The sensor operates as follows: current is applied to the bridge, which increases its temperature. If there is no flow, all the arms are heated equally, the bridge remains in balance, and there is no signal. If there is flow, the air passing over the upstream legs of the bridge reduces the temperature of the upstream legs and that leads to reduced electrical resistance for those legs. After the air has picked up heat from the upstream legs, it continues and passes over the downstream legs of the bridge. The heated air raises the temperature of these legs, increasing their electrical resistance. The resistance difference between the upstream and downstream legs unbalances the bridge, causing a voltage difference that can be amplified and calibrated to the airflow rate. Separate sensors mounted on the airfoil measure the temperature of the airflow, which is used to complete the calculation for the mass of air passing by the sensor. A current application for air-mass-flow sensors is as part of the intake system for an internal combustion engine. A mass-flow sensor is

  2. Effect of sodium dodecyl sulfate on flow and electrokinetic properties of Na-activated bentonite dispersions

    Indian Academy of Sciences (India)

    E Günıster; S İşçı; A Alemdar; N Güngör

    2004-06-01

    The present study reports the effect of anionic surfactant sodium dodecyl sulfate (SDS, C12H25 OSO3Na) upon the electrokinetic (electrophoretic mobility, zeta potential) and rheological (viscosity, yield value) properties of the Ca-bentonitic clay found in Turkey and its Na-activated form. The SDS dispersant was added in different concentrations in the range of 1 × 10-5-5 × 10-2 mol/l. The results show that the viscosity and zeta potential values of bentonite dispersion are affected by the addition of anionic surfactant. The obtained data are analysed by considering the kind of exchangeable cations. Thixotropic property effect was observed in bentonite dispersions.

  3. Electrically driven convection in a thin annular film undergoing Couette flow

    CERN Document Server

    Daya, Z A; Morris, S W; Daya, Zahir A.; Morris, Stephen W.

    1998-01-01

    We investigate the linear stability of a thin, suspended, annular film of conducting fluid with a voltage difference applied between its inner and outer edges. For a sufficiently large voltage, such a film is unstable to radially-driven electroconvection due to charges which develop on its free surfaces. The film can also be subjected to a Couette shear by rotating its inner edge. This combination is experimentally realized using films of smectic A liquid crystals. In the absence of shear, the convective flow consists of a stationary, azimuthally one-dimensional pattern of symmetric, counter-rotating vortex pairs. When Couette flow is applied, an azimuthally traveling pattern results. When viewed in a co-rotating frame, the traveling pattern consists of pairs of asymmetric vortices. We calculate the neutral stability boundary for arbitrary radius ratio $\\alpha$ and Reynolds number ${R e}$ of the shear flow, and obtain the critical control parameter $R_c (\\alpha, {R e})$ and the critical azimuthal mode number ...

  4. Film boiling heat transfer from a wire to upward flow of liquid hydrogen and liquid nitrogen

    Science.gov (United States)

    Shiotsu, M.; Shirai, Y.; Horie, Y.; Shigeta, H.; Higa, D.; Tatsumoto, H.; Hata, K.; Kobayashi, H.; Nonaka, S.; Naruo, Y.; Inatani, Y.

    2015-11-01

    Film boiling heat transfer coefficients in liquid hydrogen were measured for the heater surface superheats to 300 K under pressures from 0.4 to 1.1 MPa, liquid subcoolings to 11 K and flow velocities to 8 m/s. Two test wires were both 1.2 mm in diameter, 120 mm and 200 mm in lengths and were made of PtCo alloy. The test wires were located on the center of 8 mm and 5 mm diameter conduits of FRP (Fiber Reinforced Plastics). Furthermore film boiling heat transfer coefficients in liquid nitrogen were measured only for the 200 mm long wire. The film boiling heat transfer coefficients are higher for higher pressure, higher subcooling, and higher flow velocity. The experimental data were compared with a conventional equation for forced flow film boiling in a wide channel. The data for the 8 mm diameter conduit were about 1.7 times and those for the 5 mm conduit were about 1.9 times higher than the predicted values by the equation. A new equation was presented modifying the conventional equation based on the liquid hydrogen and liquid nitrogen data. The experimental data were expressed well by the equation.

  5. Patterning of ultrathin polymethylmethacrylate films by in-situ photodirecting of the Marangoni flow

    Science.gov (United States)

    Elashnikov, Roman; Fitl, Premysl; Svorcik, Vaclav; Lyutakov, Oleksiy

    2017-02-01

    Laser heating and Marangoni flow result in the formation of surface structures with different geometries and shape on thin polymer films. By laser beam irradiation combined with a sample movement the solid polymethylmethacrylate (PMMA) films are heated and undergo phase transition which leads to a material flow. Since the laser beam has a non-linear distribution of energy, the PMMA film is heated inhomogeneously and a surface tension gradient in a lateral direction is introduced. During this procedure additional phenomena such as "reversible" or cyclic polymer flow also take place. The careful choice of experimental conditions enables the preparation of patterns with sophisticated geometries and with hierarchical pattern organization. Depending on initial PMMA film thickness and speed of the sample movement line arrays are created, which can subsequently be transformed into the crimped lines or system of circular holes. In addition, the introduction of a constant acceleration in the sample movement or a laser beam distortion enables the preparation of regularly crimped lines, ordered hexagonal holes or overlapped plates.

  6. Flow regimes and traveling waves for a model of gravity-driven film flows in cylindrical domains

    Science.gov (United States)

    Ogrosky, H. Reed; Camassa, Roberto; Marzuola, Jeremy; Vaughn, Nathan

    2016-11-01

    Families of traveling wave solutions will be presented for a model of a falling viscous film on the interior of a vertical rigid tube. Each family contains a single solution at a 'turnaround point' with larger film thickness than all others in the family. It was previously conjectured that this turnaround point may represent a critical thickness separating two distinct flow regimes observed in physical experiments as well as two distinct types of behavior in transient solutions to the model. We will verify these hypotheses over a range of parameter values using a combination of numerical and analytical techniques. The linear stability of these solutions will also be discussed; both large- and small-amplitude solutions will be shown to be unstable, though the instability mechanisms are different for each wave type. Specifically, for small-amplitude waves, the region of relatively flat film away from the localized wave crest is subject to the same instability that makes the trivial flat-film solution unstable; for large-amplitude waves, this mechanism is present but dwarfed by a much stronger tendency to relax to a regime close to that followed by small-amplitude waves. This research has been supported in part by funding from the NSF and NIEHS.

  7. A cost-effective method for simulating city-wide air flow and pollutant dispersion at building resolving scale

    Science.gov (United States)

    Berchet, Antoine; Zink, Katrin; Muller, Clive; Oettl, Dietmar; Brunner, Juerg; Emmenegger, Lukas; Brunner, Dominik

    2017-06-01

    A cost-effective method is presented allowing to simulate the air flow and pollutant dispersion in a whole city over multiple years at the building-resolving scale with hourly time resolution. This combination of high resolution and long time span is critically needed for epidemiological studies and for air pollution control, but still poses a great challenge for current state-of-the-art modelling techniques. The presented method relies on the pre-computation of a discrete set of possible weather situations and corresponding steady-state flow and dispersion patterns. The most suitable situation for any given hour is then selected by matching the simulated wind patterns to meteorological observations in and around the city. The catalogue of pre-computed situations corresponds to different large-scale forcings in terms of wind speed, wind direction and stability. A meteorological model converts these forcings into realistic mesoscale flow patterns accounting for the effects of topography and land-use contrasts in a domain covering the city and its surroundings. These mesoscale patterns serve as boundary conditions for a microscale urban flow model which finally drives a Lagrangian air pollutant dispersion model. The method is demonstrated with the modelling system GRAMM/GRAL v14.8 for two Swiss cities in complex terrain, Zurich and Lausanne. The mesoscale flow patterns in the two regions of interest, dominated by land-lake breezes and driven by the partly steep topography, are well reproduced in the simulations matched to in situ observations. In particular, the combination of wind measurements at different locations around the city appeared to be a robust approach to deduce the stability class for the boundary layer within the city. This information is critical for predicting the temporal variability of pollution concentration within the city, regarding their relationship with the intensity of horizontal and vertical dispersion and of turbulence. In the vicinity of

  8. Dielectric dispersion of BaxSr1-xTiO3 thin film with parallel-plate and coplanar interdigital electrodes

    Science.gov (United States)

    Zhang, Xiao-Yu; Song, Qing; Xu, Feng; Sheng, Su; Wang, Peng; Ong, C. K.

    2009-03-01

    Ferroelectric BaxSr1-xTiO3 (BST) thin films with x = 0.25 and 0.5 were grown by pulsed laser deposition on single crystal LaAlO3 and Pt/Ti/SiO2/Si substrates, respectively. Capacitors were then fabricated from the BST thin films based on coplanar interdigital electrodes (CIEs) and parallel-plate electrodes (PPEs). The dielectric properties of the BST film with CIE and PPE were investigated and compared over a wide frequency range from 100 Hz to 10 GHz. The dielectric dispersion in PPE configuration, caused by the interfacial polarization in film/electrode interfaces, exhibited a strong dependence on frequency. However, the permittivity ɛCIE in CIE configuration shows a gentle variation with the frequency indicating interfacial polarization substantially suppressed. The influence upon the dielectric properties of the columnar BST grains due to the use of different forms of electrodes was discussed.

  9. Measurement and applications of dispersion in epitaxial II-VI semiconductor thin films and multilayers

    Science.gov (United States)

    Peiris, Frank Channa

    In this thesis we investigate the dispersion of the indices of refraction of II-VI semiconductors, and explore a series of materials combinations which are suited for the fabrication of distributed Bragg reflectors (DBRs). A prism coupler method and reflectivity measurements were used to determine the indices of refraction n of II-VI semiconductor ternary alloys of various compositions prepared by molecular beam epitaxy (MBE). We show that the prism coupler technique, which is capable of measuring n with an accuracy of at least 0.1% at discrete wavelengths, and simultaneously to determine the thickness of the layers with an uncertainty of less than 0.5%, is a very reliable, convenient, and accurate tool for determining compositions and growth rates for MBE. Using the highly accurate values of n obtained from the prism coupler and reflectivity measurements, we have fabricated several DBRs using different II-VI materials. From our work on DBRs, we have obtained a structure (i.e., a 20-period ZnMgSe/ZnCdSe multilayer) which yields 98% reflectivity. This is to our knowledge the highest reflectivity reported for a DBR in the II-VI semiconductor camp. Motivated by this work, we show preliminary results of monolithic microcavities which are fabricated by integrating these high-reflectivity DBRs.

  10. Wavelength dependence of reversible photodegradation of disperse orange 11 dye-doped PMMA thin films

    CERN Document Server

    Anderson, Benjamin R; Kuzyk, Mark G

    2015-01-01

    Using transmittance imaging microscopy we measure the wavelength dependence of reversible photodegradation in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA). The reversible and irreversible inverse quantum efficiencies (IQEs) are found to be constant over the spectral region investigated, with the average reversible IQE being $\\overline{B}_\\alpha= 8.70 (\\pm 0.38)\\times 10^5$ and the average irreversible IQE being $\\overline{B}_\\epsilon= 1.396 (\\pm 0.031)\\times 10^8$. The large difference between the IQEs is hypothesized to be due to the reversible decay channel being a direct decay mechanism of the dye, while the irreversible decay channel is an indirect mechanism, with the dye first absorbing light, then heating the surrounding environment causing polymer chain scission and cross linking. Additionally, the DO11/PMMA's irreversible IQE is found to be among the largest of those reported for organic dyes, implying that the system is highly photostable. We also find that the recovery rate i...

  11. Regional gene flow and population structure of the wind-dispersed plant species Hypochaeris radicata (Asteraceae) in an agricultural landscape.

    Science.gov (United States)

    Mix, C; Arens, P F P; Rengelink, R; Smulders, M J M; Van Groenendael, J M; Ouborg, N J

    2006-06-01

    Using microsatellites, we investigated population structure and gene flow of the short-lived, wind-dispersed plant species Hypochaeris radicata in a fragmented agricultural landscape where more than 99% of the nutrient-poor grasslands have disappeared over the last century. We sampled populations in the few remaining high density populations in conservation areas, as well as individuals that occurred, with lower densities, in linear landscape elements, at two spatial scales. In a re-inventory of the landscape, after 3 years, both extinctions and colonizations of populations were observed. Contrary to expectations, no differences in genetic diversity between high and low density populations were observed. Both types of populations had relatively high levels of diversity. Overall genetic differentiation (theta) was 0.04 and significantly different from zero (P aerodynamic models on seed dispersal of H. radicata. We discuss the consequences of these results for an evaluation of the probability of persistence of this species in the fragmented landscape.

  12. Flow-directed assembly of non-spherical titania nanoparticles into superhydrophilic thin films

    Science.gov (United States)

    Ojha, Abhijeet; Thakker, Manish; Shah, Dinesh O.; Thareja, Prachi

    2016-03-01

    Superhydrophilic thin films of 21 nm sized non-spherical titania nanoparticles are fabricated from a colloidal suspension by fixed blade flow coating without UV illumination. At a blade angle of a = 36° and a gap of d = 300 µm, hierarchically structured films with increasing surface roughness along with microscopic voids are formed depending on the substrate velocity and the titania volume fraction. Increasing the roughness is shown to be concomitant to an increase in the hydrophilicity, eventually leading to superhydrophilicity or water contact angle less than 5°.

  13. Film Cooling Optimization Using Numerical Computation of the Compressible Viscous Flow Equations and Simplex Algorithm

    Directory of Open Access Journals (Sweden)

    Ahmed M. Elsayed

    2013-01-01

    Full Text Available Film cooling is vital to gas turbine blades to protect them from high temperatures and hence high thermal stresses. In the current work, optimization of film cooling parameters on a flat plate is investigated numerically. The effect of film cooling parameters such as inlet velocity direction, lateral and forward diffusion angles, blowing ratio, and streamwise angle on the cooling effectiveness is studied, and optimum cooling parameters are selected. The numerical simulation of the coolant flow through flat plate hole system is carried out using the “CFDRC package” coupled with the optimization algorithm “simplex” to maximize overall film cooling effectiveness. Unstructured finite volume technique is used to solve the steady, three-dimensional and compressible Navier-Stokes equations. The results are compared with the published numerical and experimental data of a cylindrically round-simple hole, and the results show good agreement. In addition, the results indicate that the average overall film cooling effectiveness is enhanced by decreasing the streamwise angle for high blowing ratio and by increasing the lateral and forward diffusion angles. Optimum geometry of the cooling hole on a flat plate is determined. In addition, numerical simulations of film cooling on actual turbine blade are performed using the flat plate optimal hole geometry.

  14. Relaxation and Flow of Polymer Thin Films in Isothermal Temperature Jump Measurements

    Science.gov (United States)

    Beaucage, G.; Banach, M. J.; Vaia, R. A.

    2000-03-01

    The dynamic behavior of thin polymer films is of interest in fabrication of microelectronics, optoelectronics and for the coatings industry. It is known that polymer relaxation is effected by film thickness and by the particular substrate/polymer pair. Recently, we have used a spectroscopic ellipsometer to investigate the glass transition in thin films. In addition to information on modification of thermal transitions, the spectroscopic ellipsometer allows for direct observation of the isothermal dimensions of a thin polymer film as a function of time following a rapid temperature change. Recent results will be presented on the observation of time dependence in film-normal thickness and normalized, in-plane, lateral dimension (explained in talk) as well as simple fits to this relaxation behavior in terms of a normalized viscosity and relaxation time. Initial results support a highly asymmetric initial thermal expansion followed by close to isotropic relaxation and anisotropic flow. These features may elucidate models for chain orientation in thin polymer films. Beaucage, G.; Composto, R.; Stein, R.S. (1993). J. Poly. Sci., Polym. Phys. Ed., 31 319. Kovacs, A. J.; Hutchinson, J. M.; Aklonis, J. J. (1977) in "The Structure of Non-Crystalline Materials", Ed. P. H. Gaskell, Taylor and Francis, London. Banach, M. J.; Clarson, S. J.; Beaucage, G.; Kramer, E. J.; Benkoski, J.; Vaia, R. Submitted Macromolecules (1999). Beaucage, G.; Banach, M. J.; Vaia, R. A. Submitted Macromolecules (1999).

  15. Symplectic Exact Solution for Stokes Flow in the Thin Film Coating Applications

    Directory of Open Access Journals (Sweden)

    Yan Wang

    2014-01-01

    Full Text Available The symplectic analytical method is introduced to solve the problem of the stokes flow in the thin film coating applications. Based on the variational principle, the Lagrangian function of the stokes flow is established. By using the Legendre transformation, the dual variables of velocities and the Hamiltonian function are derived. Considering velocities and stresses as the basic variables, the equations of stokes flow problems are transformed into Hamiltonian system. The method of separation of variables and expansion of eigenfunctions are developed to solve the governing equations in Hamiltonian system, and the analytical solutions of the stokes flow are obtained. Several numerical simulations are carried out to verify the analytical solutions in the present study and discuss the effects of the driven lids of the square cavity on the dynamic behavior of the flow structure.

  16. Flow Characteristics of Film Flow over 3D Corrugations Column Plate%三维波纹结构塔板上薄膜流体的流动特性研究

    Institute of Scientific and Technical Information of China (English)

    童仲尧; 洪伟荣; 郭雅琼; 李杰

    2015-01-01

    Film flow is often employed to improve the mass transfer between gas and liquid in chemical industry application. Corrugations on packing surface are used to alter the flow characteristics of liquid film to enhance the mass transfer efficiency. In this investigation, film flow over three dimensional corrugations was simulated with numerical method. The effect of three dimensional corrugations on film flow was studied and the flow characteristics relating to the mass transfer was analyzed. In the numerical simulations, a multiphase solver in the open source computational fluid dynamics software OpenFOAM was used to track the free surface position with VOF method. The simulated results were validated by the PIV based experimental data published in literature. After the validation of the numerical model, an analysis of the velocity field in the liquid film was conducted. The results show that three dimensional corrugations can induce disturbance not only in the vertical direction, but also in the cross direction in film flow, which is not found in film flow over two dimensional corrugations. For film flow over three dimensional corrugations, fluid is converged at the troughs of the three dimensional waves and dispersed on the wave crest. This flow behavior is helpful for the mixing of fluids with different concentrations and dramatically enhances the mass transfer efficiency between the gas and liquid.%在化工传质过程中,薄膜流体(film flow)经常被用来改善液体与气体间的质量传递。填料板上的波纹结构能引起液体薄膜流动特性的改变,从而提高薄膜流体的传质效率。在本次研究中,作者对三维波纹结构塔板上的液体薄膜进行数值仿真,研究了三维波纹结构对液体薄膜流动特性的影响,并分析流动特性与气液两相间传质的联系。数值仿真中使用了开源计算流体力学软件 OpenFOAM中基于VOF(volume of fluid)法的多相流求解器计算薄膜流体自

  17. Flow characterization on a thin film spinning apparatus

    Science.gov (United States)

    Alvarado, Alonso A.

    In industrial milling operations that use comminution and wet-comminution techniques, the reduction of the particle size is usually achieved through crushing the sample with a material harder than the product. These methods are convenient when the required median particle size is above 400 um. However, to obtain post-milling particle distributions with 85% sub-micron particles (in number) is both energy intensive, and time consuming. For conventional milling machines, to have the required output in several ton/hr of a product, having a large number of particles in the micron or sub-micron sizes at an affordable rate is cumbersome. Here, a wet-comminution machine that has shown to achieve the aforementioned milestones in the laboratory scale is studied. However, when the machine is scaled to industrial processes, it was recorded that some of the product variables are difficult to scale. In these studies, we attempt to understand the mechanisms by which this machine operates in order to achieve successful scaling. The apparatus operates completely on fluid mechanics principles, it consists of two concentric cylinders, the inner cylinder that has a smaller radius than the outer, rotates while the larger is held stationary. The inner cylinder is also shorter in length than outer, hollow in the inside and has transversal holes where the shaft attaches to the apparatus. The apparatus can operate in batch condition, where the liquid volume is much less than the volume of the apparatus, typically 0.V3T,0.42VT and 0.54V T. In addition, the apparatus can operate with throughflow, which the upper plate covering the apparatus is reduced in radius. Two component Laser Doppler Velocimetry (LDV) was used to obtain even-time averaged statistics of the azimuthal and axial velocities, in the gap and underneath the impeller. Also, Flow Visualization using Kalliroscopic particles was performed as means of observing large scale structures in the gap. Moreover, single plane Particle

  18. Two-phase flow equations for a dilute dispersion of gas bubbles in liquid

    NARCIS (Netherlands)

    Biesheuvel, A.; Wijngaarden, van L.

    1984-01-01

    Equations of motion correct to the first order of the gas concentration by volume are derived for a dispersion of gas bubbles in liquid through systematic averaging of the equations on the microlevel. First, by ensemble averaging, an expression for the average stress tensor is obtained, which is non

  19. Construction and Validation of an Urban Area Flow and Dispersion Model on Building Scales

    Institute of Scientific and Technical Information of China (English)

    陈笔澄; 刘树华; 缪育聪; 王姝; 李源

    2013-01-01

    This paper presents a numerical model that simulates the wind fields, turbulence fields, and dispersion of gaseous substances in urban areas on building to city block scales. A Computational Fluid Dynamics (CFD) approach using the steady-state, Reynolds-Averaged Navier-Stokes (RANS) equations with the standard k-ε turbulence model within control volumes of non-uniform cuboid shapes has been employed. Dispersion field is computed by solving an unsteady transport equation of passive scalar. Another approach based on Gaussian plume model is used to correct the turbulent Schmidt number of tracer, in order to improve the dispersion simulation. The experimental data from a wind tunnel under neutral conditions are used to validate the numerical results of velocity, turbulence, and dispersion fields. The numerical results show a reasonable agreement with the wind tunnel data. The deviation of concentration between the simulation with corrected turbulent Schmidt number and the wind tunnel experiments may arise from 1) imperfect point sources, 2) heterogeneous turbulent diffusivity, and 3) the constant turbulent Schmidt assumption used in the model.

  20. Analysis of flow development in centrifugal atomization: Part I. Film thickness of a fully spreading melt

    Science.gov (United States)

    Zhao, Y. Y.

    2004-09-01

    Centrifugal atomization of metal melts is a cost-effective process for powder production and spray deposition. The properties of the as-produced powder and deposit are determined primarily by the characteristics of the atomized droplets, which in turn are largely dependent on the flow development of the melt on the atomizer. This paper develops a model for analysing the flow development of a fully spreading melt on and off the atomizing cup. The model can be used to calculate the velocity and film thickness of the melt as a function of melt volume flow rate, cup rotation speed, cup radius and cup slope angle, as well as to predict the trajectory of the spray off the cup. The model implies that the disintegration of a fully spreading melt takes place in the region just off the cup edge and the film thickness at the cup edge is a critical factor determining the sizes of the resultant droplets. The film thickness at the cup edge is shown to decrease with decreasing volume flow rate, with increasing cup rotation speed, with increasing cup radius and with decreasing cup slope angle.

  1. Numerical Simulation of Reactive Flows in Overexpanded Supersonic Nozzle with Film Cooling

    Directory of Open Access Journals (Sweden)

    Mohamed Sellam

    2015-01-01

    Full Text Available Reignition phenomena occurring in a supersonic nozzle flow may present a crucial safety issue for rocket propulsion systems. These phenomena concern mainly rocket engines which use H2 gas (GH2 in the film cooling device, particularly when the nozzle operates under over expanded flow conditions at sea level or at low altitudes. Consequently, the induced wall thermal loads can lead to the nozzle geometry alteration, which in turn, leads to the appearance of strong side loads that may be detrimental to the rocket engine structural integrity. It is therefore necessary to understand both aerodynamic and chemical mechanisms that are at the origin of these processes. This paper is a numerical contribution which reports results from CFD analysis carried out for supersonic reactive flows in a planar nozzle cooled with GH2 film. Like the experimental observations, CFD simulations showed their ability to highlight these phenomena for the same nozzle flow conditions. Induced thermal load are also analyzed in terms of cooling efficiency and the results already give an idea on their magnitude. It was also shown that slightly increasing the film injection pressure can avoid the reignition phenomena by moving the separation shock towards the nozzle exit section.

  2. The fluid flow and heat transfer performance of thermoplastic microcapillary films

    Science.gov (United States)

    Hornung, Christian H.; Hallmark, Bart; Hesketh, Robert P.; Mackley, Malcolm R.

    2006-02-01

    This paper is concerned with the evaluation of microcapillary films (MCFs) for microfluidic applications. MCFs are a novel type of low cost plastic film containing continuous arrays of microcapillaries that are extruded from thermoplastics where the capillaries within these films can be round or elliptical with diameters between 30 and 500 µm. The hydrodynamic response of MCFs has been investigated in a series of experiments where the flow within each capillary was laminar with Reynolds numbers up to a maximum of 1800. Pressure drop measurements were consistent with standard laminar flow predictions. A set of experiments involving single- and two-flow systems were conducted to characterize the heat transfer performance of MCFs and the efficacy of heat transfer was found to rank close to that of metallic microfluidic devices. The experimental heat transfer measurements were compared to finite-element model predictions for the MCF geometry and the modelling results were in good agreement with experiment. The overall results demonstrate the viable performance of MCFs for low cost application to examples such as flow within capillaries where temperature profiling is required along the length of the capillaries.

  3. How large grains increase bulk friction in bi-disperse granular chute flows

    Science.gov (United States)

    Staron, Lydie; Phillips, Jeremy C.

    2016-07-01

    In this contribution, we apply contact dynamics discrete simulations to explore how the mechanical properties of simple bi-dimensional granular chute flows are affected by the existence of two grain sizes. Computing partial stress tensors for the phases of small and large grains, we show that the phase of large grain exhibits a much larger shear strength than the phase of small grains. This difference translates in terms of the flow internal friction: adopting the μ (I) dependence to describe the flow frictional properties, we establish that the flow mean friction coefficient increases with the volume fraction of large grains. Hence, while the presence of large grains may induce lubrication in 3D unconfined flows due to the self-channelisation and levées formation, the effect of large grains on the bulk properties is to decrease the flow mobility.

  4. Exploitation of pulsed flows for on-line dispersive liquid-liquid microextraction: Spectrophotometric determination of formaldehyde in milk.

    Science.gov (United States)

    Nascimento, Carina F; Brasil, Marcos A S; Costa, Susana P F; Pinto, Paula C A G; Saraiva, Maria Lúcia M F S; Rocha, Fábio R P

    2015-11-01

    Formaldehyde is often added to foods as a preservative, but it is highly toxic to humans, having been identified as a carcinogenic substance. It has also been used for the adulteration of milk in order to diminish the bacteria count and increase the shelf life of the product. Herein, we present a green dispersive liquid-liquid microextraction procedure in a flow-batch system for the determination of formaldehyde in milk. Pulsed flows were exploited for the first time to improve the dispersion of the extractant in the aqueous phase. The Hantzsch reaction was used for the derivatization of formaldehyde and the product was extracted with the ionic liquid (IL) trihexyltetradecylphosphonium chloride with methanol as the disperser. The flow-batch chamber was made of stainless steel with the facility for resistive heating to speed up the derivatization reaction. Spectrophotometric measurements were directly carried out in the organic phase using an optical fiber spectrophotometer. The limit of detection and coefficient of variation were 100 μg L(-1) and 3.1% (n=10), respectively, with a linear response from 0.5 to 5.0 mg L(-1), described by the equation A=0.088+0.116CF (mg L(-1)) in which A is absorbance and CF is formaldehyde concentration in mg L(-1). The estimated recoveries of formaldehyde from spiked milk samples ranged from 91% to 106% and the slopes of the analytical curves obtained with reference solutions in water or milk were in agreement, thus indicating the absence of matrix effects. Accuracy was demonstrated by the agreement of the results with those achieved by the reference fluorimetric procedure at the 95% confidence level. The proposed procedure allows for 10 extractions per hour, with minimized reagent consumption (120 μL of IL and 3.5 μL acetylacetone) and generation of only 6.7 mL waste per determination, which contribute to the eco-friendliness of the procedure.

  5. Stability of Wavy Films in Gas-Liquid Two-Phase Flows at Normal and Microgravity Conditions

    Science.gov (United States)

    Balakotaiah, V.; Jayawardena, S. S.

    1996-01-01

    For flow rates of technological interest, most gas-liquid flows in pipes are in the annular flow regime, in which, the liquid moves along the pipe wall in a thin, wavy film and the gas flows in the core region. The waves appearing on the liquid film have a profound influence on the transfer rates, and hence on the design of these systems. We have recently proposed and analyzed two boundary layer models that describe the characteristics of laminar wavy films at high Reynolds numbers (300-1200). Comparison of model predictions to 1-g experimental data showed good agreement. The goal of our present work is to understand through a combined program of experimental and modeling studies the characteristics of wavy films in annular two-phase gas-liquid flows under normal as well as microgravity conditions in the developed and entry regions.

  6. Application of the lattice-Boltzmann method to study flow and dispersion in channels with and without expansion and contraction geometry

    Science.gov (United States)

    Kumar, Rajinder; Nivarthi, Sriram S.; Davis, H. Ted; Kroll, D. M.; Maier, Robert S.

    1999-11-01

    The lattice-Boltzmann (LB) method, derived from lattice gas automata, is a relatively new technique for studying transport problems. The LB method is investigated for its accuracy to study fluid dynamics and dispersion problems. Two problems of relevance to flow and dispersion in porous media are addressed: (i) Poiseuille flow between parallel plates (which is analogous to flow in pore throats in two-dimensional porous networks), and (ii) flow through an expansion-contraction geometry (which is analogous to flow in pore bodies in two-dimensional porous networks). The results obtained from the LB simulations are compared with analytical solutions when available, and with solutions obtained from a finite element code (FIDAP) when analytical results are not available. Excellent agreement is found between the LB results and the analytical/FIDAP solutions in most cases, indicating the utility of the lattice-Boltzmann method for solving fluid dynamics and dispersion problems. Copyright

  7. Experiments on the Flow of a Thin Liquid Film Over a Horizontal Stationary and Rotating Disk Surface

    Science.gov (United States)

    Ozar, B.; Cetegen, B. M.; Faghri, A.

    2003-01-01

    Experiments on characterization of thin liquid films flowing over stationary and rotating disk surfaces are described. The thin liquid film was created by introducing deionized water from a flow collar at the center of an aluminum disk with a known initial film thickness and uniform radial velocity. Radial film thickness distribution was measured using a non-intrusive laser light interface reflection technique that enabled the measurement of the instantaneous film thickness over a finite segment of the disk. Experiments were performed for a range of flow rates between 3.01pm and 15.01pm, corresponding to Reynolds numbers based on the liquid inlet gap height and velocity between 238 and 1,188. The angular speed of the disk was varied from 0 rpm to 300 rpm. When the disk was stationary, a circular hydraulic jump was present in the liquid film. The liquid-film thickness in the subcritical region (down-stream of the hydraulic jump) was an order of magnitude greater than that in the supercritical region (upstream of the hydraulic jump) which was of the order of 0.3 mm. As the Reynolds number increased, the hydraulic jump migrated toward the edge of the disk. In the case of rotation, the liquid-film thickness exhibited a maximum on the disk surface. The liquid-film inertia and friction influenced the inner region where the film thickness progressively increased. The outer region where the film thickness decreased was primarily affected by the centrifugal forces. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. At high rotational speeds, spiral waves were observed on the liquid film. It was also determined that the angle of the waves which form on the liquid surface was a function of the ratio of local radial to tangential velocity.

  8. Predicting chaotic dispersion with Eulerian symmetry measures: Wavy Taylor-vortex flow

    Science.gov (United States)

    King, G. P.; Rowlands, G.; Rudman, Murray; Yannacopoulos, A. N.

    2001-09-01

    In a recent investigation of particle transport in numerically computed wavy Taylor-vortex flow, Rudman estimated an effective axial diffusion coefficient, Dz, to characterize the enhanced mixing due to chaotic advection [AIChE J. 44, 1015 (1998)]. We find that Dz is proportional to the product of two measures of symmetry deviation. The first is a measure of the average deviation of the flow from rotational symmetry, and the second is a measure of the average deviation from flexion-free flow (a flow where the curl of the vorticity is zero). Because these quantities are obtained directly from the velocity field, we call them Eulerian symmetry measures. Thus, we show that the macroscopic transport behavior in a flow can be quantified directly in terms of the velocity field and its gradients, and hence provides a connection between Eulerian and Lagrangian pictures of transport—a problem of fundamental and widespread interest.

  9. Film-cooled turbine endwall in a transonic flow field; Filmgekuehlte Turbinenplattform in transsonischem Stroemungsfeld

    Energy Technology Data Exchange (ETDEWEB)

    Nicklas, M.

    2000-11-01

    Aero and thermodynamic measurements at the endwall of a turbine nozzle guide vane were carried out. These investigations are the first where the complete blade passage at the endwall in a transonic flow field is analysed for heat transfer and adiabatic film-cooling effectiveness. The aerodynamic measurements identify an intensive interaction between the coolant air and the secondary flow field. Similarly strong variations in heat transfer and film-cooling effectiveness were found. Analysis of the heat transfer measurements indicates that the heat transfer represents an indispensable tool for the evaluation of platform film-cooling design. On the basis of infrared temperature measurements, a procedure for accurate analysis of heat transfer and film-cooling effectiveness in a complex transonic flow field was developed. This measurement technique combines high accuracy with flexibility of application. These investigations have led to design improvements for film-cooling systems at the platform. (orig.) [German] Aero- und thermodynamische Messungen an einer Plattform eines Turbinenleitrads werden beschrieben. Erstmals wird in einem transsonischen Stroemungsfeld die komplette Seitenwand bezueglich des Waermeuebergangs und der adiabaten Filmkuehleffektivitaet untersucht. Die aerodynamischen Messungen zeigen eine intensive Wechselwirkung der Kuehlluft mit dem Sekundaerstroemungsfeld. Daraus resultierend treten starke Aenderungen des Waermeuebergangs und der Filmkuehleffektivitaet auf. Die Resultate der Waermeuebergangsmessungen zeigen, dass der Waermeuebergang eine wichtige Groesse fuer die Bewertung eines Filmkuehldesigns an einer Plattform darstellt. Ein Messverfahren auf der Grundlage von Infrarot-Temperaturmessungen fuer eine genaue Analyse des Waermeuebergangs und der Filmkuehleffektivitaet in den komplexen Verhaeltnissen einer transsonischen Stroemung wurde entwickelt. Mit der verwendeten Messtechnik wird eine hohe Genauigkeit bei der Ermittlung der quantitativen

  10. Turbine endwall film cooling with combustor-turbine interface gap leakage flow: Effect of incidence angle

    Science.gov (United States)

    Zhang, Yang; Yuan, Xin

    2013-04-01

    This paper is focused on the film cooling performance of combustor-turbine leakage flow at off-design condition. The influence of incidence angle on film cooling effectiveness on first-stage vane endwall with combustor-turbine interface slot is studied. A baseline slot configuration is tested in a low speed four-blade cascade comprising a large-scale model of the GE-E3Nozzle Guide Vane (NGV). The slot has a forward expansion angle of 30 deg. to the endwall surface. The Reynolds number based on the axial chord and inlet velocity of the free-stream flow is 3.5 × 105 and the testing is done in a four-blade cascade with low Mach number condition (0.1 at the inlet). The blowing ratio of the coolant through the interface gap varies from M = 0.1 to M = 0.3, while the blowing ratio varies from M = 0.7 to M = 1.3 for the endwall film cooling holes. The film-cooling effectiveness distributions are obtained using the pressure sensitive paint (PSP) technique. The results show that with an increasing blowing ratio the film-cooling effectiveness increases on the endwall. As the incidence angle varies from i = +10 deg. to i = -10 deg., at low blowing ratio, the averaged film-cooling effectiveness changes slightly near the leading edge suction side area. The case of i = +10 deg. has better film-cooling performance at the downstream part of this region where the axial chord is between 0.15 and 0.25. However, the disadvantage of positive incidence appears when the blowing ratio increases, especially at the upstream part of near suction side region where the axial chord is between 0 and 0.15. On the main passage endwall surface, as the incidence angle changes from i = +10 deg. to i = -10 deg., the averaged film-cooling effectiveness changes slightly and the negative incidence appears to be more effective for the downstream part film cooling of the endwall surface where the axial chord is between 0.6 and 0.8.

  11. Indoor Airflow Patterns, Dispersion of Human Exhalation Flow and Risk of Airborne Cross-infection between People in a Room

    DEFF Research Database (Denmark)

    Olmedo, Inés

    In recent years, an interest in understanding the mechanisms of cross-infection between people in the same room has increased significantly. The SARS (Severe Acute Respiratory Syndrome) outbreak occurred in Asia in 2003 reopened the study of the airborne disease transmission as one of the most...... in the air. These tiny particles or droplet nuclei can follow the air flow pattern in the room and produce high contaminant concentration in different areas of the indoor environment. This fact can provoke a high exposure to exhaled contaminants and a risk of cross-infection to a susceptible person situated...... in the same room. Abundant evidence shows that the air flow distribution systems play a crucial role in the dispersion of these human exhaled contaminants. However, there are many parameters that influence the cross-infection risk between people situated close to each other in a ventilated room, such as...

  12. Indoor Airflow Patterns, Dispersion of Human Exhalation Flow and Risk of Airborne Cross-Infection between People in a Room

    DEFF Research Database (Denmark)

    Olmedo, Inés

    In recent years, an interest in understanding the mechanisms of cross-infection between people in the same room has increased significantly. The SARS (Severe Acute Respiratory Syndrome) outbreak occurred in Asia in 2003 reopened the study of the airborne disease transmission as one of the most...... in the air. These tiny particles or droplet nuclei can follow the air flow pattern in the room and produce high contaminant concentration in different areas of the indoor environment. This fact can provoke a high exposure to exhaled contaminants and a risk of cross-infection to a susceptible person situated...... in the same room. Abundant evidence shows that the air flow distribution systems play a crucial role in the dispersion of these human exhaled contaminants. However, there are many parameters that influence the cross-infection risk between people situated close to each other in a ventilated room, such as...

  13. The effect of oxygen flow rate on refractive index of aluminum oxide film deposited by electron beam evaporation technique

    Directory of Open Access Journals (Sweden)

    R Shakouri

    2016-02-01

    Full Text Available The effects of oxygen flow rate on refractive index of aluminum oxide film have been investigated. The Al2O3 films are deposited by electron beam on glass substrate at different oxygen flow rates. The substrate was heated to reach  and the temperature was constant during the thin film growth. The transmittance spectrum of samples was recorded in the wavelength 400-800 nm.  Then, using the maxima and minima of transmittance the refractive index and the extinction coefficient of samples were determined. It has been found that if we reduce the oxygen flow, while the evaporation rate is kept constant, the refractive index of Al2O3 films increases. On the other hand, reduced oxygen pressure causes the Al2O3 films to have some absorption.

  14. NUMERICAL SIMULATION FOR SHALLOW FLOW AND POLLUTANT DISPERSION BASED ON QUAD-TREE MESHES

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-dong; HUA Zu-lin

    2006-01-01

    A 2D depth-averaged flow-pollutant coupled model based on quad-tree meshes was established to accurately simulate flows in water areas with irregular natural boundaries in this paper. The grids were generated by recursive subdivision about seeding points. A new neighbor-finding algorithm was presented. The governing equations were discretized in collocated conservative variables by using the finite volume method, and the normal flux of mass, momentum and pollutants across the interface between cells were computed by a Godunov-type Flux Difference Splitting (FDS) scheme. The model was applied to simulate flow fields around a groin. The computed values are in agreement with observed data. The results indicate that quad-tree meshes have fine local resolution, high efficiency and easy local refinement. It is clear that the quad-tree grid model can offer gains in efficiency when applied to complex flow domains or strong shear flows. Finally, the model is applied to flow fields and concentration fields simulation in Jiangsu Haizhou Bay. The simulated polluted area is matched well with observations. Therefore, this model can be used to predict flow and concentration fields of actual water area with irregular natural land boundaries.

  15. CFD simulations of flow and dust dispersion in a realistic urban area

    Directory of Open Access Journals (Sweden)

    Kun Luo

    2016-01-01

    Full Text Available Fluid flow and dust transportation in a realistic urban residential community under dust storm weather conditions are investigated using computational fluid dynamics (CFD with a grid resolution of several meters. The dust transportation and concentration distribution are obtained through the Lagrangian-formulated discrete particle model by integrating the particle velocity between certain time intervals. The fluid flow is solved by the realizable $ k - \\varepsilon $ model. It is found that the dust transportation and distribution are very closely related to the flow field. The flow field in a real residential community is very complicated. When the building axes are perpendicular to the wind direction, the flows resemble the classic street canyon flow. Places with a low wind speed and high vorticity usually have a high dust concentration. As the wind direction changes, the fluid flow and dust distribution differ from case to case, but the general features are kept. In addition, the building shape and particle-wall interaction conditions have additional effects on the dust distribution, which need further study in the future.

  16. Analysis of thin film flow over a vertical oscillating belt with a second grade fluid

    Directory of Open Access Journals (Sweden)

    Taza Gul

    2015-06-01

    Full Text Available An analysis is performed to study the unsteady thin film flow of a second grade fluid over a vertical oscillating belt. The governing equation for velocity field with appropriate boundary conditions is solved analytically using Adomian decomposition method (ADM. Expressions for velocity field have been obtained. Optimal asymptotic method (OHAM has also been used for comparison. The effects of Stocks number, frequency parameter and pressure gradient parameters have been sketched graphically and discussed.

  17. Demonstration of a plasma mirror based on a laminar flow water film

    Energy Technology Data Exchange (ETDEWEB)

    Panasenko, Dmitriy; Shu, Anthony; Gonsalves, Anthony; Nakamura, Kei; Matlis, Nicholas; Toth, Csaba; Leemans, Wim

    2011-07-22

    A plasma mirror based on a laminar water film with low flow speed 0.5-2 cm/s has been developed and characterized, for use as an ultrahigh intensity optical reflector. The use of flowing water as atarget surface automatically results in each laser pulse seeing a new interaction surface and avoids the need for mechanical scanning of the target surface. In addition, the breakdown of water does notproduce contaminating debris that can be deleterious to vacuum chamber conditions and optics, such as is the case when using conventional solid targets. The mirror exhibits 70percent reflectivity, whilemaintaining high-quality of the reflected spot.

  18. Optical and Compositional Properties of SiO x Films Deposited by HFCVD: Effect of the Hydrogen Flow

    Science.gov (United States)

    Luna López, J. A.; Vázquez Valerdi, D. E.; Benítez Lara, A.; García Salgado, G.; Hernández-de la Luz, A. D.; Morales Sánchez, A.; Flores Gracia, F. J.; Dominguez, M. A.

    2017-04-01

    In this work, the effect of hydrogen flow and thermal annealing on the compositional and optical properties of non-stoichiometric silicon oxide (SiO x) films with embedded silicon nanocrystals is reported. The SiO x films are obtained by hot filament chemical vapor deposition technique at three different hydrogen flow levels, namely, 50 sccm, 100 sccm, and 150 sccm. The SiO x films are characterized by different techniques. It is found by x-ray photoelectron spectroscopy (XPS) that with increasing hydrogen flow, the SiO x films contain higher silicon (Si) concentration. When the hydrogen flow decreases, the absorption edge of the as-grown SiO x films, as obtained from the transmittance spectra, shifts from 300 nm to 500 nm, and this opens the possibility of band gap tuning. Increasing the hydrogen flow level in turn means that the SiO x films contain higher Si concentration, as confirmed by the XPS profile composition measured in the SiO x films. After thermal annealing, the SiO x films transmittance spectra showed a further shift of the absorption edge toward larger wavelengths. The Fourier transform infrared (FTIR) spectroscopy reveals film composition changes induced by the hydrogen flow variations. In addition, the FTIR spectra reveal the bands attributed to the hydrogen presence in the as-grown SiO x films. The bands become more intense with increasing hydrogen flow, but they rapidly disappear after the thermal annealing. The as-grown SiO x films exhibit wide band photoluminescence (PL) spectra with the main components at 688 nm, 750 nm, and 825 nm. The SiO x film deposited at 100 sccm hydrogen flow level shows the strongest PL intensity. According to PL results, the thermal annealing of the SiO x films generates the PL quenching in all samples due to hydrogen evaporation. The defects such as OH and Si-H groups in the as-grown SiOx films not only modify the optical band gap structure, but they also play the role of passivating non-radiative defects, which

  19. Polymer melt rheology and flow simulations applied to cast film extrusion die design: An industrial perspective

    Science.gov (United States)

    Catherine, Olivier

    2017-05-01

    This article is an overview of the techniques used today in the area of rheology and flow simulation, on the industrial level, for cast film extrusion die design. This industry has made significant progress over the past three decades and die and feedblock design and optimization certainly have been instrumental in the overall improvement. Dies and coextrusion feedblocks are a critical aspect of the process due to the layering and forming function, which drive the final product economics and properties. Polymer melt rheology is a key aspect to consider when optimizing the flow patterns in the extrusion equipment. Not only is rheology critical for the flow channel design when aiming at obtaining a uniform flow distribution at the die exit, but also it is playing a major role in the thermal aspect of the flow due to the strong mechanical and thermal coupling. This coupling comes, on one hand, from the occurrence of viscous dissipation in the flow and on the other hand from the significant temperature dependency of melt viscosity. Viscous dissipation is due to relatively high melt viscosities and strain rates, especially with today's processes which involve formidable extrusion speeds. The third aspect discussed in this paper is the complexity of residence time distribution in modern flow channels, which is evaluated with advanced three-dimensional flow simulation and particle tracking.

  20. Modeling Film-Coolant Flow Characteristics at the Exit of Shower-Head Holes

    Science.gov (United States)

    Garg, Vijay K.; Gaugler, R. E. (Technical Monitor)

    2000-01-01

    The coolant flow characteristics at the hole exits of a film-cooled blade are derived from an earlier analysis where the hole pipes and coolant plenum were also discretized. The blade chosen is the VKI rotor with three staggered rows of shower-head holes. The present analysis applies these flow characteristics at the shower-head hole exits. A multi-block three-dimensional Navier-Stokes code with Wilcox's k-omega model is used to compute the heat transfer coefficient on the film-cooled turbine blade. A reasonably good comparison with the experimental data as well as with the more complete earlier analysis where the hole pipes and coolant plenum were also gridded is obtained. If the 1/7th power law is assumed for the coolant flow characteristics at the hole exits, considerable differences in the heat transfer coefficient on the blade surface, specially in the leading-edge region, are observed even though the span-averaged values of h (heat transfer coefficient based on T(sub o)-T(sub w)) match well with the experimental data. This calls for span-resolved experimental data near film-cooling holes on a blade for better validation of the code.

  1. High gene flow due to pelagic larval dispersal among South Pacific archipelagos in two amphidromous gastropods (Neritomorpha: Neritidae).

    Science.gov (United States)

    Crandall, E D; Taffel, J R; Barber, P H

    2010-06-01

    The freshwater stream fauna of tropical oceanic islands is dominated by amphidromous species, whose larvae are transported to the ocean and develop in the plankton before recruiting back to freshwater habitat as juveniles. Because stream habitat is relatively scarce and unstable on oceanic islands, this life history would seem to favor either the retention of larvae to their natal streams, or the ability to delay metamorphosis until new habitat is encountered. To distinguish between these hypotheses, we used population genetic methods to estimate larval dispersal among five South Pacific archipelagos in two amphidromous species of Neritid gastropod (Neritina canalis and Neripteron dilatatus). Sequence data from mitochondrial cytochrome oxidase I (COI) revealed that neither species is genetically structured throughout the Western Pacific, suggesting that their larvae have a pelagic larval duration (PLD) of at least 8 weeks, longer than many marine species. In addition, the two species have recently colonized isolated Central Pacific archipelagos in three independent events. Since colonization, there has been little or no gene flow between the Western and Central Pacific archipelagos in N. canalis, and high levels of gene flow across the same region in N. dilatatus. Both species show departures from neutrality and recent dates for colonization of the Central Pacific archipelagos, which is consistent with frequent extinction and recolonization of stream populations in this area. Similar results from other amphidromous species suggest that unstable freshwater habitats promote long-distance dispersal capabilities.

  2. Diagnostics of two-phase flows with high concentration of a solid dispersed phase using fiber-optic sensors

    Science.gov (United States)

    Evseev, A. R.

    2016-10-01

    This paper is focused on the physical modeling of two-phase flows with high concentration of the dispersed phase. The fiber-optical sensors and their calibration procedure were developed for bubble concentration measurements in the fluidized bed apparatus (FB). Distributions of bubble concentration in the 2D and 3D FB apparatuses, which determine the quality of fluidization and local density of filling material, were obtained. The techniques of particle velocity and concentration measurements in the circulating fluidized bed (CFB) was developed using three-fiber sensor (the differential scheme of LDA) operated in backscattering regime. Sensor operation was analyzed and the main systematic measurement errors were determined; the original construction of the sensor was designed. The data on the velocity and concentration profiles of dispersed phase in a large-scale CFB apparatus were obtained for fluidization of particles by air. It was found that with increasing circulation velocity in the CFB apparatus, the particle concentration increases in the near-wall region much higher than in the flow core. The method of particle velocity measurements in a liquid was developed using the laser Doppler fiber anemometer (LDFA-1), operating in the backscattering regime. The signal to noise ratio was obtained for particles of different size and material in test measurements. The rates of consolidated precipitation of cryolite particles in a sedimentation apparatus with the inclined walls were measured.

  3. Analysis of Turbine Blade Relative Cooling Flow Factor Used in the Subroutine Coolit Based on Film Cooling Correlations

    Science.gov (United States)

    Schneider, Steven J.

    2015-01-01

    Heat transfer correlations of data on flat plates are used to explore the parameters in the Coolit program used for calculating the quantity of cooling air for controlling turbine blade temperature. Correlations for both convection and film cooling are explored for their relevance to predicting blade temperature as a function of a total cooling flow which is split between external film and internal convection flows. Similar trends to those in Coolit are predicted as a function of the percent of the total cooling flow that is in the film. The exceptions are that no film or 100 percent convection is predicted to not be able to control blade temperature, while leaving less than 25 percent of the cooling flow in the convection path results in nearing a limit on convection cooling as predicted by a thermal effectiveness parameter not presently used in Coolit.

  4. Seismic wave attenuation and dispersion due to wave-induced fluid flow in rocks with strong permeability fluctuations.

    Science.gov (United States)

    Germán Rubino, J; Monachesi, Leonardo B; Müller, Tobias M; Guarracino, Luis; Holliger, Klaus

    2013-12-01

    Oscillatory fluid movements in heterogeneous porous rocks induced by seismic waves cause dissipation of wave field energy. The resulting seismic signature depends not only on the rock compressibility distribution, but also on a statistically averaged permeability. This so-called equivalent seismic permeability does not, however, coincide with the respective equivalent flow permeability. While this issue has been analyzed for one-dimensional (1D) media, the corresponding two-dimensional (2D) and three-dimensional (3D) cases remain unexplored. In this work, this topic is analyzed for 2D random medium realizations having strong permeability fluctuations. With this objective, oscillatory compressibility simulations based on the quasi-static poroelasticity equations are performed. Numerical analysis shows that strong permeability fluctuations diminish the magnitude of attenuation and velocity dispersion due to fluid flow, while the frequency range where these effects are significant gets broader. By comparing the acoustic responses obtained using different permeability averages, it is also shown that at very low frequencies the equivalent seismic permeability is similar to the equivalent flow permeability, while for very high frequencies this parameter approaches the arithmetic average of the permeability field. These seemingly generic findings have potentially important implications with regard to the estimation of equivalent flow permeability from seismic data.

  5. Influence of nitrogen flow on structure and magnetic properties of magnetron-sputtered FeCo/TiN multilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Klever, Christian; Seemann, Klaus [Forschungszentrum Karlsruhe, Institute of Materials Research I, Eggenstein-Leopoldshafen (Germany)

    2009-07-01

    Soft magnetic thin films with appropriate high frequency properties are interesting for applications, e.g., as core material for microinductors and for magnetoelastic sensors/actuators. For the use in such devices, tailoring of the magnetic film properties (e. g. saturation magnetization M{sub S}, coercitive field H{sub C}, anisotropy field H{sub K}) is necessary. In this study, multilayer films consisting of FeCo as the magnetic constituent and TiN as diffusion barrier are developed. The films are grown by sequential magnetron sputter deposition using a FeCo and a TiN target in an Ar atmosphere with an additional N{sub 2} flow between 0 and 5 % of the total gas flow. The films are annealed ex-situ in a static magnetic field. The static and dynamic macroscopic magnetic properties of the films are determined by means of a vibrating sample magnetometer and a strip-line permeameter connected to a vector network analyzer, respectively. The microstructure and constitution of the films are examined by XRD, XRR, TEM and AES depth profiling. It is shown that films with a coercitive field below 0.2 mT and a sufficient high frequency response can be produced by defining appropriate growth and film annealing conditions. Furthermore, the correlation between the nanoscale coating architecture, the films' microstructure and its macroscopic magnetic properties is presented.

  6. Thin-film flow in helically wound shallow channels of arbitrary cross-sectional shape

    Science.gov (United States)

    Arnold, D. J.; Stokes, Y. M.; Green, J. E. F.

    2017-01-01

    We consider the steady, gravity-driven flow of a thin film of viscous fluid down a helically wound shallow channel of arbitrary cross-sectional shape with arbitrary torsion and curvature. This extends our previous work [D. J. Arnold et al., "Thin-film flow in helically-wound rectangular channels of arbitrary torsion and curvature," J. Fluid Mech. 764, 76-94 (2015)] on channels of rectangular cross section. The Navier-Stokes equations are expressed in a novel, non-orthogonal coordinate system fitted to the channel bottom. By assuming that the channel depth is small compared to its width and that the fluid depth in the vertical direction is also small compared to its typical horizontal extent, we are able to solve for the velocity components and pressure analytically. Using these results, a differential equation for the free surface shape is obtained, which must in general be solved numerically. Motivated by the aim of understanding flows in static spiral particle separators used in mineral processing, we investigate the effect of cross-sectional shape on the secondary flow in the channel cross section. We show that the competition between gravity and inertia in non-rectangular channels is qualitatively similar to that in rectangular channels, but that the cross-sectional shape has a strong influence on the breakup of the secondary flow into multiple clockwise-rotating cells. This may be triggered by small changes to the channel geometry, such as one or more bumps in the channel bottom that are small relative to the fluid depth. In contrast to the secondary flow which is quite sensitive to small bumps in the channel bottom, the free-surface profile is relatively insensitive to these. The sensitivity of the flow to the channel geometry may have important implications for the design of efficient spiral particle separators.

  7. Characterisation of DLC films deposited using titanium isopropoxide (TIPOT) at different flow rates.

    Science.gov (United States)

    Said, R; Ali, N; Ghumman, C A A; Teodoro, O M N D; Ahmed, W

    2009-07-01

    In recent years, there has been growing interest in the search for advanced biomaterials for biomedical applications, such as human implants and surgical cutting tools. It is known that both carbon and titanium exhibit good biocompatibility and have been used as implants in the human body. It is highly desirable to deposit biocompatible thin films onto a range of components in order to impart biocompatibility and to minimise wear in implants. Diamond like carbon (DLC) is a good candidate material for achieving biocompatibility and low wear rates. In this study, thin films of diamond-like-carbon DLC were deposited onto stainless steel (316) substrates using C2H2, argon and titanium isopropoxide (TIPOT) precursors. Argon was used to generate the plasma in the plasma enhanced vapour deposition (PECVD) system. A critical coating feature governing the performance of the component during service is film thickness. The as-grown films were in the thickness range 90-100 nm and were found to be dependent on TIPOT flow rate. Atomic force microscopy (AFM) was used to characterise the surface roughness of the samples. As the flow rate of TIPOT increased the average roughness was found to increase in conjunction with the film thickness. Raman spectroscopy was used to investigate the chemical structure of amorphous carbon matrix. Surface tension values were calculated using contact angle measurements. In general, the trend of the surface tension results exhibited an opposite trend to that of the contact angle. The elemental composition of the samples was characterised using a VG ToF SIMS (IX23LS) instrument and X-ray photoelectron spectroscopy (XPS). Surprisingly, SIMS and XPS results showed that the DLC samples did not show evidence of titanium since no peaks representing to titanium appeared on the SIMS/XPS spectra.

  8. A Novel Thin Film Nitinol Covered Neurovascular Stent Significantly Decreases Intra-Aneurysmal Flow In Vitro

    Science.gov (United States)

    Chun, Youngjae; Hur, Soojung; Shayan, Mahdis; Kealey, Colin; Levi, Daniel; Mohanchandra, Kp; di Carlo, Dino; Carman, Gregory

    2013-11-01

    A novel thin film nitinol (TFN) stent has been developed to promote aneurysm quiescence by diminishing flow across the aneurysm's neck. Laboratory aneurysm models were used to assess the flow changes produced by stents covered with different patterns of TFN. Flow diversion stents were constructed by covering Wingspan stents (Boston Scientific, DxL:4x20mm) with TFNs (i.e., 77 and 82 percent porosity). The flow changes that occur after deployment of two different porous TFN covered stent in intracranial aneurysm models were evaluated in vitro. The 82 percent porous TFN covered stent reduced the intra-aneurysmal mean flow velocity by 86.42 percent, while a 77 percent porous TFN covered stent reduced to intra-aneurysmal mean flow velocity to 93.44 percent compared to a nonstented model. Local wall shear rates were also significantly reduced in wide-neck aneurysm model (i.e., 97.52 - 98.92 percent) with TFN stent placement. The results showed that TFN covered stents significantly reduced intra-aneurysmal flow velocity magnitudes and local wall shear rates. This suggests that TFN covered stents with both 77 and 82 percent porosity have great potential to promote thrombosis in both wide-necked and fusiform aneurysm sacs.

  9. DENSE MULTIPHASE FLOW SIMULATION: CONTINUUM MODEL FOR POLY-DISPERSED SYSTEMS USING KINETIC THEORY

    Energy Technology Data Exchange (ETDEWEB)

    Moses Bogere

    2011-08-31

    The overall objective of the project was to verify the applicability of the FCMOM approach to the kinetic equations describing the particle flow dynamics. For monodispersed systems the fundamental equation governing the particle flow dynamics is the Boltzmann equation. During the project, the FCMOM was successfully applied to several homogeneous and in-homogeneous problems in different flow regimes, demonstrating that the FCMOM has the potential to be used to solve efficiently the Boltzmann equation. However, some relevant issues still need to be resolved, i.e. the homogeneous cooling problem (inelastic particles cases) and the transition between different regimes. In this report, the results obtained in homogeneous conditions are discussed first. Then a discussion of the validation results for in-homogeneous conditions is provided. And finally, a discussion will be provided about the transition between different regimes. Alongside the work on development of FCMOM approach studies were undertaken in order to provide insights into anisotropy or particles kinetics in riser hydrodynamics. This report includes results of studies of multiphase flow with unequal granular temperatures and analysis of momentum re-distribution in risers due to particle-particle and fluid-particle interactions. The study of multiphase flow with unequal granular temperatures entailed both simulation and experimental studies of two particles sizes in a riser and, a brief discussion of what was accomplished will be provided. And finally, a discussion of the analysis done on momentum re-distribution of gas-particles flow in risers will be provided. In particular a discussion of the remaining work needed in order to improve accuracy and predictability of riser hydrodynamics based on two-fluid models and how they can be used to model segregation in risers.

  10. Experiments on Heat Transfer in a Thin Liquid Film Flowing Over a Rotating Disk

    Science.gov (United States)

    Sankaran, Subramanian (Technical Monitor); Ozar, B.; Cetegen, B. M.; Faghri, A.

    2004-01-01

    An experimental study of heat transfer into a thin liquid film on a rotating heated disk is described. Deionized water was introduced at the center of a heated. horizontal disk with a constant film thickness and uniform radial velocity. Radial distribution of the disk surface temperatures was measured using a thermocouple/slip ring arrangement. Experiments were performed for a range of liquid flow rates between 3.01pm and 15.01pm. The angular speed of the disk was varied from 0 rpm to 500 rpm. The local heat transfer coefficient was determined based on the heat flux supplied to the disk and the temperature difference between the measured disk surface temperature and the liquid entrance temperature onto the disk. The local heat transfer coefficient was seen to increase with increasing flow rate as well as increasing angular velocity of the disk. Effect of rotation on heat transfer was largest for the lower liquid flow rates with the effect gradually decreasing with increasing liquid flow rates. Semi-empirical correlations are presented in this study for the local and average Nusselt numbers.

  11. Effect of oxygen to argon flow ratio on the properties of Al-doped ZnO films for amorphous silicon thin film solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yang-Shih [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan, ROC (China); Lien, Shui-Yang, E-mail: syl@mdu.edu.tw [Department of Materials Science and Engineering, MingDao University, ChangHua 52345, Taiwan, ROC (China); Huang, Yung-Chuan [Department of Materials Science and Engineering, MingDao University, ChangHua 52345, Taiwan, ROC (China); Wang, Chao-Chun [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan, ROC (China); Liu, Chueh-Yang [Department of Materials Science and Engineering, MingDao University, ChangHua 52345, Taiwan, ROC (China); Nautiyal, Asheesh [Department of Mechanical Engineering, Yuan Ze University, 135 Yuan-Tung Road, Chungli, 320 Taoyuan, Taiwan, ROC (China); Wuu, Dong-Sing [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan, ROC (China); Lee, Shuo-Jun [Department of Mechanical Engineering, Yuan Ze University, 135 Yuan-Tung Road, Chungli, 320 Taoyuan, Taiwan, ROC (China)

    2013-02-01

    Transparent conductive oxide thin films in solar cell fabrication have attracted much attention due to their high conductivity and transmittance. In this paper, we have investigated the aluminum-doped zinc oxide (AZO) thin films prepared by radiofrequency magnetron sputtering on Asahi U-type SnO{sub 2} glass with different O{sub 2}/Ar flow ratios in vacuum chamber. Furthermore, the micro-structural, electrical, and optical properties of AZO/SnO{sub 2} films were studied. The change in O{sub 2}/Ar flow ratios is found to significantly affect the haze value, and slightly affect electrical resistivity and transmittance of the films. Afterward, the fabricated AZO thin films with different O{sub 2}/Ar flow ratios were used for building the solar cell devices. The current–voltage and external quantum efficiency characteristics were investigated for the solar cell devices. The optimized O{sub 2}/Ar flow ratio of 3 for solar device shows the best efficiency of 10.41%, and a 20% increase in short-circuit current density compared to typical Asahi solar cells. - Highlights: ► A thin Al-doped zinc oxide (AZO) film has been deposited on SnO{sub 2} substrates. ► The AZO film deposited at an O{sub 2}/Ar ratio of 3 shows low resistivity and high haze. ► The AZO film contains tiny grains that enhance light scattering. ► The amorphous silicon solar cell with the AZO layer shows a 20% increase in Jsc.

  12. A constitutive-relationship model for film flow on rough fracture surfaces

    Science.gov (United States)

    Liu, H. H.

    Film flow on fracture surfaces may be an important mechanism for fast flow in unsaturated fractured rocks. Incorporating this mechanism into a numerical model requires knowledge of constitutive relationships for film flow. Based on fractal concepts and a conceptual argument of Tokunaga et al. that water films could be treated as analogues to water in unsaturated porous media, a simple constitutive-relationship model has been developed. The validity of the model is supported by excellent agreements between calculation results and experimental observations for two different fracture surfaces. L'écoulement en film sur les surfaces de fracture peut être un mécanisme important pour l'écoulement rapide dans les roches fracturées non saturées. L'incorporation de ce mécanisme dans un modèle numérique nécessite la connaissance des relations fondamentales pour l'écoulement en film. Basé sur des concepts fractals et sur un argument conceptuel de Tokunaga et al. selon lequel des films d'eau peuvent être considérés comme des analogues de l'eau en milieu poreux non saturé, un modèle simple des relations fondamentales a été développé. La validité de ce modèle est confirmée grâce à une excellente concordance entre les résultats du calcul et les observations expérimentales pour deux surfaces différentes de fractures. El flujo pelicular en la superficie de las fracturas puede ser un mecanismo importante para el flujo rápido en rocas fracturadas no saturadas. Incorporarlo en un modelo numérico requiere conocer las relaciones constitutivas del flujo pelicular. Se ha desarrollado un modelo de una relación constitutiva sencilla partiendo de conceptos fractales y de un argumento conceptual de Tokunaga et al., según el cual las películas de agua pueden ser tratadas como análogos del agua en medios porosos no saturados. La validez del modelo es corroborada por los excelentes ajustes entre los resultados numéricos y las observaciones experimentales en dos

  13. The direct enstrophy cascade of two-dimensional soap film flows

    CERN Document Server

    Rivera, Mike; Ecke, Robert

    2013-01-01

    We investigate the direct enstrophy cascade of two-dimensional decaying turbulence in a flowing soap film channel. We use a coarse-graining approach that allows us to resolve the nonlinear dynamics and scale-coupling simultaneously in scale and in space. From our data, we calculate the transfer of enstrophy across scale $\\ell$ at every point $\\bx$ in the flow domain. We verify an exact relation due to Eyink (1995) between traditional 3rd-order structure function and the enstrophy flux obtained by coarse-graining. We also present experimental evidence that enstrophy cascades to smaller (larger) scales with a 60% (40%) probability, in support of theoretical predictions by Merilees & Warn (1975). Using an Eulerian coherent structure identification technique, we then determine the effect of flow topology on the enstrophy cascade. A key finding is that "centers" are inefficient at transferring enstrophy between scales, in contrast to "saddle" regions which transfer enstrophy to small scales with high efficienc...

  14. Note: Signal conditioning of a hot-film anemometer for a periodic flow rate monitoring system.

    Science.gov (United States)

    Mantovani, Federico; Tagliaferri, Cristian

    2011-12-01

    A flow monitoring system based on a constant temperature hot-film anemometer is presented. The device has been designed to monitor a dispensing process of extremely low quantities of adhesive material. The monitoring device presented in this paper is useful in industrial applications where exact flow speed tracking is not needed, but reliability and tolerance to parameters variability are essential. During the design of the device, problems related to the physical characteristic of the calorimetric sensor, in particular its thermal capacitance, and to the periodic nature of the monitored flow have been taken into account and suitable solutions have been implemented. The schematic representation of the monitoring device together with the experimental results obtained by monitoring fluids with different physical characteristics are presented.

  15. Theory for particle settling and shear-induced migration in thin-film liquid flow.

    Science.gov (United States)

    Cook, Benjamin P

    2008-10-01

    Particles suspended in a film flow can either settle out of the flow, remain well mixed, or even advance faster than the fluid, accumulating at the moving contact line. Recent experiments by Zhou et al. [Phys. Rev. Lett. 94, 117803 (2005)] have demonstrated that these three settling behaviors can be achieved by control of the average particle concentration phi and inclination angle theta . This work presents a theory for determining the settling behavior in the Stokes regime by calculating the depth profile of phi and the depth-averaged velocities of the liquid and particle phases. It is found that shear-induced particle fluxes can lead to an inversely stratified flow, in which the particles move on average faster than the liquid. The theory is directly compared to Zhou et al.'s experimental data, and the implications of stratification for lubrication-type models are also discussed.

  16. Physics of microstructures enhancement of thin film evaporation heat transfer in microchannels flow boiling

    Science.gov (United States)

    Bigham, Sajjad; Fazeli, Abdolreza; Moghaddam, Saeed

    2017-03-01

    Performance enhancement of the two-phase flow boiling heat transfer process in microchannels through implementation of surface micro- and nanostructures has gained substantial interest in recent years. However, the reported results range widely from a decline to improvements in performance depending on the test conditions and fluid properties, without a consensus on the physical mechanisms responsible for the observed behavior. This gap in knowledge stems from a lack of understanding of the physics of surface structures interactions with microscale heat and mass transfer events involved in the microchannel flow boiling process. Here, using a novel measurement technique, the heat and mass transfer process is analyzed within surface structures with unprecedented detail. The local heat flux and dryout time scale are measured as the liquid wicks through surface structures and evaporates. The physics governing heat transfer enhancement on textured surfaces is explained by a deterministic model that involves three key parameters: the drying time scale of the liquid film wicking into the surface structures (τd), the heating length scale of the liquid film (δH) and the area fraction of the evaporating liquid film (Ar). It is shown that the model accurately predicts the optimum spacing between surface structures (i.e. pillars fabricated on the microchannel wall) in boiling of two fluids FC-72 and water with fundamentally different wicking characteristics.

  17. Physics of microstructures enhancement of thin film evaporation heat transfer in microchannels flow boiling.

    Science.gov (United States)

    Bigham, Sajjad; Fazeli, Abdolreza; Moghaddam, Saeed

    2017-03-17

    Performance enhancement of the two-phase flow boiling heat transfer process in microchannels through implementation of surface micro- and nanostructures has gained substantial interest in recent years. However, the reported results range widely from a decline to improvements in performance depending on the test conditions and fluid properties, without a consensus on the physical mechanisms responsible for the observed behavior. This gap in knowledge stems from a lack of understanding of the physics of surface structures interactions with microscale heat and mass transfer events involved in the microchannel flow boiling process. Here, using a novel measurement technique, the heat and mass transfer process is analyzed within surface structures with unprecedented detail. The local heat flux and dryout time scale are measured as the liquid wicks through surface structures and evaporates. The physics governing heat transfer enhancement on textured surfaces is explained by a deterministic model that involves three key parameters: the drying time scale of the liquid film wicking into the surface structures (τd), the heating length scale of the liquid film (δH) and the area fraction of the evaporating liquid film (Ar). It is shown that the model accurately predicts the optimum spacing between surface structures (i.e. pillars fabricated on the microchannel wall) in boiling of two fluids FC-72 and water with fundamentally different wicking characteristics.

  18. Physics of microstructures enhancement of thin film evaporation heat transfer in microchannels flow boiling

    Science.gov (United States)

    Bigham, Sajjad; Fazeli, Abdolreza; Moghaddam, Saeed

    2017-01-01

    Performance enhancement of the two-phase flow boiling heat transfer process in microchannels through implementation of surface micro- and nanostructures has gained substantial interest in recent years. However, the reported results range widely from a decline to improvements in performance depending on the test conditions and fluid properties, without a consensus on the physical mechanisms responsible for the observed behavior. This gap in knowledge stems from a lack of understanding of the physics of surface structures interactions with microscale heat and mass transfer events involved in the microchannel flow boiling process. Here, using a novel measurement technique, the heat and mass transfer process is analyzed within surface structures with unprecedented detail. The local heat flux and dryout time scale are measured as the liquid wicks through surface structures and evaporates. The physics governing heat transfer enhancement on textured surfaces is explained by a deterministic model that involves three key parameters: the drying time scale of the liquid film wicking into the surface structures (τd), the heating length scale of the liquid film (δH) and the area fraction of the evaporating liquid film (Ar). It is shown that the model accurately predicts the optimum spacing between surface structures (i.e. pillars fabricated on the microchannel wall) in boiling of two fluids FC-72 and water with fundamentally different wicking characteristics. PMID:28303952

  19. Effect of Nitrogen Flow Rate on Structure and Adhesion Strength of Magnetron Sputtered Ti-Si-N Nanocomposite Films

    Directory of Open Access Journals (Sweden)

    He Chunlin

    2016-01-01

    Full Text Available Ti-Si-N nanocomposite films were prepared by co-sputtering Ti and Si targets in Ar/N2 gas atmosphere. The effect of N2 flow rate on the structure, adhesion strength and friction coefficient of the deposited films was studied by using X-ray diffraction, atom force microscope, field emission scanning electron microscopy and multi-functional tester for material surface properties. The Ti-Si-N films had a fine, smooth and compact structure with TiN nanograins embedded in an amorphous Si3N4 matrix. The nanocomposite films exhibited (200, (111, (220 and (222 reflections with a dominant orientation of the (200 reflection. When the N2 flow rate increased, the film structure was refined. It was found that both interfacial adhesion strength and friction coefficient depended on the N2 flow rate, and the best values were exhibited by the nanocomposite film produced at N2 flow rate of 15 sccm, perhaps contributed to a finer and smoother structure of this deposited film.

  20. Effect of silane flow rate on structural, electrical and optical properties of silicon thin films grown by VHF PECVD technique

    Energy Technology Data Exchange (ETDEWEB)

    Gope, Jhuma [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Department of Physics, Banaras Hindu University, Varanasi 221005 (India); Kumar, Sushil, E-mail: skumar@nplindia.org [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Sudhakar, S.; Rauthan, C.M.S. [Physics of Energy Harvesting Division, CSIR-Network of Institutes for Solar Energy, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Srivastava, P.C. [Department of Physics, Banaras Hindu University, Varanasi 221005 (India)

    2013-08-15

    Hydrogenated silicon thin films deposited by VHF PECVD process for various silane flow rates have been investigated. The silane flow rate was varied from 5 sccm to 30 sccm, maintaining all other parameters constant. The electrical, structural and optical properties of these films were systematically studied as a function of silane flow rate. These films were characterized by Raman spectroscopy, Scanning Electron Microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy and UV–visible (UV–Vis) spectroscopy. Different crystalline volume fraction (22%–60%) and band gap (∼1.58 eV–∼1.96 eV) were achieved for silicon thin films by varying the silane concentration. A transition from amorphous to nanocrystalline silicon has been confirmed by Raman and FTIR analysis. The film grown at this transition region shows the high conductivity in the order of 10{sup −4} Ω{sup −1} cm{sup −1}. - Highlights: • Silicon films grown using VHF PECVD at various F{sub silane} (silane flow rate). • Amorphous to nanocrystalline silicon transition at F{sub silane} ∼5 sccm–10 sccm. • Deposition rate increases with the increase of F{sub silane}. • Powder formation occurred beyond 20 sccm of F{sub silane}. • Film grown at 20 sccm shows max. crystalline fraction ∼60% with E{sub g} ∼1.58 eV.

  1. Traveling waves for a model of gravity-driven film flows in cylindrical domains

    Science.gov (United States)

    Camassa, Roberto; Marzuola, Jeremy L.; Ogrosky, H. Reed; Vaughn, Nathan

    2016-10-01

    Traveling wave solutions are studied for a recently-derived model of a falling viscous film on the interior of a vertical rigid tube. By identifying a Hopf bifurcation and using numerical continuation software, families of non-trivial traveling wave solutions may be traced out in parameter space. These families all contain a single solution at a 'turnaround point' with larger film thickness than all others in the family. In an earlier paper, it was conjectured that this turnaround point may represent a critical thickness separating two distinct flow regimes observed in physical experiments as well as two distinct types of behavior in transient solutions to the model. Here, these hypotheses are verified over a range of parameter values using a combination of numerical and analytical techniques. The linear stability of these solutions is also discussed; both large- and small-amplitude solutions are shown to be unstable, though the instability mechanisms are different for each wave type. Specifically, for small-amplitude waves, the region of relatively flat film away from the localized wave crest is subject to the same instability that makes the trivial flat-film solution unstable; for large-amplitude waves, this mechanism is present but dwarfed by a much stronger tendency to relax to a regime close to that followed by small-amplitude waves.

  2. Thermocapillary flow of thin Cu-water nanoliquid film during spin coating process

    Science.gov (United States)

    Maity, Susanta

    2017-01-01

    Unsteady flow of thin Cu-water nanoliquid film over a horizontal rotating disk is studied numerically using finite difference technique under the assumption of planar interface. It is also assumed that the disk is cooling axisymmetrically from below. The effects of the nanolayer thickness and nanoparticle radius are considered for investigation. It is found that the film thinning rate decreases with increase of the nanoparticle volume fraction. It is also found that thickness of liquid decreases with increase of the thermocapillary parameter. The results show that the rate of film thinning is more for the thermal conductivity model of Yu and Choi [47] compared to the model of Maxwell [46]. It is observed that the film thinning rate increases with increase of nanolayer thickness but it decreases with the nanoparticle radius. A curve R=R_c(z,t) in R-z plane is delineated along which temperature gradient T_z is zero and positive or negative according to RR_c respectively. Furthermore, it is shown that the region for T_z>0 enlarges with increase of the nanoparticle volume fraction and the nanolayer thickness.

  3. Wash flow disturbance and summer wash flow in the Mojave Desert: Influence on dispersion, production, and physiological functioning of dominant shrubs

    Science.gov (United States)

    Newlander, April

    In many Mojave Desert ecosystems, water infiltrates to root-zones in greatest proportion via washes. As such, washes have a pronounced effect on plant dispersion and size across these landscapes. Desert roads alter the natural spatial patterns of washes on alluvial fans (locally called bajadas) and potentially affect plant production and distribution. As a winter-rainfall dominated ecosystem, climate changes in the Mojave Desert that increase summer precipitation may also play an important role in altering vegetation processes influenced by washes. Road effects on the spatial distribution of desert plants on a Mojave Desert bajada were examined using remotely sensed LiDAR data and ground based measurements of plant size. Plant physiological responses to summer wash flow were also quantified by measuring gas exchange and water status of two dominant perennial species, Larrea tridentata and Ambrosia dumosa. Larrea and Ambrosia plants were nearly 7x and 4x larger where wash flow has been enhanced by road culverts, relative to undisturbed areas and areas where flow has been cut-off by the presence of a road/railroad. Clustering of large plants occurred along wash margins, with clustering most pronounced in areas of enhanced wash flow. No clustering was found where wash flow has been eliminated. For ecophysiological traits, both species showed pronounced responses to the pulse of water; however, these responses varied as a function of distance from wash. Larrea plants within 3 m and Ambrosia plants within ca. 2 m from the wash responded to the pulse of water. Leaf phenology dictated the timing of carbon gain as Larrea experienced a rapid but short-lived increase in stomatal conductance compared to a significant response for over a month following the pulse for Ambrosia. These results indicate that disturbance of desert washes has a pronounced impact on vegetation structure, and changing climatic conditions that impact plant function could potentially lead to even

  4. Particle-laden flows forced by the disperse phase: Comparison between Lagrangian and Eulerian simulations

    OpenAIRE

    Vié, Aymeric; Pouransari, Hadi; Zamansky, Rémi; Mani, Ali

    2015-01-01

    International audience; The goal of the present work is to assess the ability of Eulerian moment methods to reproduce the physics of two-way coupled particle-laden turbulent flow systems. Previous investigations have been focused on effects such as preferential concentration, and turbulence modulation, but in regimes in which turbulence is sustained by an imposed external forcing. We show that in such regimes, Eulerian methods need resolutions finer than nominal Kolmogorov scale in order to c...

  5. Large-eddy simulation of heavy particle dispersion in wall-bounded turbulent flows

    Science.gov (United States)

    Salvetti, M. V.

    2015-03-01

    Capabilities and accuracy issues in Lagrangian tracking of heavy particles in velocity fields obtained from large-eddy simulations (LES) of wall-bounded turbulent flows are reviewed. In particular, it is shown that, if no subgrid scale (SGS) model is added to the particle motion equations, particle preferential concentration and near-wall accumulation are significantly underestimated. Results obtained with SGS modeling for the particle motion equations based on approximate deconvolution are briefly recalled. Then, the error purely due to filtering in particle tracking in LES flow fields is singled out and analyzed. The statistical properties of filtering errors are characterized in turbulent channel flow both from an Eulerian and a Lagrangian viewpoint. Implications for stochastic SGS modeling in particle motion equations are briefly outlined. The author is retracting this article due to a significant overlap in content from three previously published papers [Phys. Fluids 20, 040603 (2008); Phys. Fluids 24, 045103 (2012); Acta Mech. 201(1-4), 277 (2008)], which constitutes dual publication. The author would like to apologize for any inconvenience this has caused. The article is retracted from the scientific record with effect from 12 January 2017.

  6. Directional dispersal between mid-ocean ridges: deep-ocean circulation and gene flow in Ridgeia piscesae.

    Science.gov (United States)

    Young, C R; Fujio, S; Vrijenhoek, R C

    2008-04-01

    This study examined relationships between bathymetrically induced deep-ocean currents and the dispersal of the hydrothermal vent tubeworm Ridgeia piscesae along the northeast Pacific ridge system. A robust diagnostic model of deep-ocean circulation in this region predicted strong southeasterly currents following contours of the Blanco Transform Fault, a 450-km lateral offset that separates the Gorda and Juan de Fuca ridge systems. Such currents should facilitate the southward dispersal of R. piscesae larvae. Immigration rates for populations north and south of the Blanco Transform Fault were estimated from molecular population genetic data. Mitochondrial DNA evidence revealed population subdivision across the Blanco Transform Fault, and a strong directional bias in gene flow that was consistent with predictions of the circulation model. The distribution of mitochondrial diversity between the northern and southern populations of R. piscesae suggests that the Gorda Ridge tubeworms have maintained larger effective population sizes than the northern populations, a pattern that also exists in co-occurring limpets. Together, these data suggest that the northern vent fields may experience a higher frequency of habitat turnover and consequently more rapid losses of genetic diversity.

  7. A stochastic asymptotic-preserving scheme for a kinetic-fluid model for disperse two-phase flows with uncertainty

    Science.gov (United States)

    Jin, Shi; Shu, Ruiwen

    2017-04-01

    In this paper we consider a kinetic-fluid model for disperse two-phase flows with uncertainty. We propose a stochastic asymptotic-preserving (s-AP) scheme in the generalized polynomial chaos stochastic Galerkin (gPC-sG) framework, which allows the efficient computation of the problem in both kinetic and hydrodynamic regimes. The s-AP property is proved by deriving the equilibrium of the gPC version of the Fokker-Planck operator. The coefficient matrices that arise in a Helmholtz equation and a Poisson equation, essential ingredients of the algorithms, are proved to be positive definite under reasonable and mild assumptions. The computation of the gPC version of a translation operator that arises in the inversion of the Fokker-Planck operator is accelerated by a spectrally accurate splitting method. Numerical examples illustrate the s-AP property and the efficiency of the gPC-sG method in various asymptotic regimes.

  8. Effect of double dispersion on non-Darcy mixed convective flow over vertical surface embedded in porous medium

    Institute of Scientific and Technical Information of China (English)

    A. A. AFIFY; N. S. ELGAZERY

    2013-01-01

    A numerical study of a non-Darcy mixed convective heat and mass transfer flow over a vertical surface embedded in a porous medium under the effects of double dispersion, melting, and thermal radiation is investigated. The set of governing boundary layer equations and the boundary conditions is transformed into a set of coupled nonlinear ordinary differential equations with the relevant boundary conditions. The transformed equations are solved numerically by using the Chebyshev pseudospectral method. Com-parisons of the present results with the existing results in the literature are made, and good agreement is found. Numerical results for the velocity, temperature, concentration profiles, and local Nusselt and Sherwood numbers are discussed for various values of phys-ical parameters.

  9. A stochastic asymptotic-preserving scheme for a kinetic-fluid model for disperse two-phase flows with uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Shi, E-mail: sjin@wisc.edu [Department of Mathematics, University of Wisconsin–Madison, Madison, WI 53706 (United States); Institute of Natural Sciences, School of Mathematical Science, MOELSEC and SHL-MAC, Shanghai Jiao Tong University, Shanghai 200240 (China); Shu, Ruiwen, E-mail: rshu2@math.wisc.edu [Department of Mathematics, University of Wisconsin–Madison, Madison, WI 53706 (United States)

    2017-04-15

    In this paper we consider a kinetic-fluid model for disperse two-phase flows with uncertainty. We propose a stochastic asymptotic-preserving (s-AP) scheme in the generalized polynomial chaos stochastic Galerkin (gPC-sG) framework, which allows the efficient computation of the problem in both kinetic and hydrodynamic regimes. The s-AP property is proved by deriving the equilibrium of the gPC version of the Fokker–Planck operator. The coefficient matrices that arise in a Helmholtz equation and a Poisson equation, essential ingredients of the algorithms, are proved to be positive definite under reasonable and mild assumptions. The computation of the gPC version of a translation operator that arises in the inversion of the Fokker–Planck operator is accelerated by a spectrally accurate splitting method. Numerical examples illustrate the s-AP property and the efficiency of the gPC-sG method in various asymptotic regimes.

  10. Effectiveness of non-volatile falling film absorbers with solution and coolant in counter-flow

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.S. [Austrian Institute of Technology, Dept. Energy, Giefinggasse 2, 1210 Vienna (Austria); Infante Ferreira, C.A. [Delft University of Technology, Engineering Thermodynamics, Leeghwaterstraat 44, 2628 CA Delft (Netherlands)

    2010-01-15

    Effectiveness equations are developed for non-volatile falling film absorbers with solution and coolant in counter-flow. It is shown how mixture thermodynamics and film theory can be used to simplify the problem to give eigenvalue solutions for temperature and concentration profiles and how heat and mass transfer effectiveness equations can be derived from such solutions. The results indicate that the transfer process in an absorber is driven by two driving forces, i.e. the difference between bulk solution and cooling water temperatures and the initial deviation of bulk solution from its equilibrium state. Asymptotic effectiveness equations are derived for a few limiting cases to show that they approach their counterparts in single-phase heat transfer and isothermal absorption processes. (author)

  11. Influence of flow rate on different properties of diamond-like nanocomposite thin films grown by PECVD

    Directory of Open Access Journals (Sweden)

    T. S. Santra

    2012-06-01

    Full Text Available Diamond-like nanocomposite (DLN thin films were deposited on pyrex glass substrate using different flow rate of haxamethyldisiloxane (HMDSO based liquid precursor with nitrogen gas as a glow discharged decomposition by plasma enhanced chemical vapor deposition (PECVD technique. The significant influence of different precursor flow rates on refractive index and thickness of the DLN films was measured by using spectroscopic filmatrics and DEKTAK profilometer. Optical transparency of the DLN thin films was analyzed by UV-VIS-NIR spectrometer. FTIR spectroscopy, provides the information about shifted bonds like SiC2, Si-C, Si-O, C-C, Si-H, C-H, N-H, and O-H with different precursor flow rate. We have estimated the hardness of the DLN films from Raman spectroscopy using Gaussian deconvolution method and tried to investigate the correlation between hardness, refractive index and thickness of the films with different precursor flow rates. The composition and surface morphology of the DLN films were investigated by X-ray photo electron spectroscopy (XPS and atomic force microscopy (AFM respectively. We have analyzed the hardness by intensity ratio (ID/IG of D and G peaks and correlates with hardness measurement by nanoindentation test where hardness increases from 27.8 μl/min to 80.6μl/min and then decreases with increase of flow rate from 80.6μl/min to 149.5μl/min. Finally, we correlates different parameters of structural, optical and tribological properties like film-thickness, refractive index, light transmission, hardness, surface roughness, modulus of elasticity, contact angle etc. with different precursor flow rates of DLN films.

  12. Influence of flow rate on different properties of diamond-like nanocomposite thin films grown by PECVD

    Science.gov (United States)

    Santra, T. S.; Bhattacharyya, T. K.; Tseng, F. G.; Barik, T. K.

    2012-06-01

    Diamond-like nanocomposite (DLN) thin films were deposited on pyrex glass substrate using different flow rate of haxamethyldisiloxane (HMDSO) based liquid precursor with nitrogen gas as a glow discharged decomposition by plasma enhanced chemical vapor deposition (PECVD) technique. The significant influence of different precursor flow rates on refractive index and thickness of the DLN films was measured by using spectroscopic filmatrics and DEKTAK profilometer. Optical transparency of the DLN thin films was analyzed by UV-VIS-NIR spectrometer. FTIR spectroscopy, provides the information about shifted bonds like SiC2, Si-C, Si-O, C-C, Si-H, C-H, N-H, and O-H with different precursor flow rate. We have estimated the hardness of the DLN films from Raman spectroscopy using Gaussian deconvolution method and tried to investigate the correlation between hardness, refractive index and thickness of the films with different precursor flow rates. The composition and surface morphology of the DLN films were investigated by X-ray photo electron spectroscopy (XPS) and atomic force microscopy (AFM) respectively. We have analyzed the hardness by intensity ratio (ID/IG) of D and G peaks and correlates with hardness measurement by nanoindentation test where hardness increases from 27.8 μl/min to 80.6μl/min and then decreases with increase of flow rate from 80.6μl/min to 149.5μl/min. Finally, we correlates different parameters of structural, optical and tribological properties like film-thickness, refractive index, light transmission, hardness, surface roughness, modulus of elasticity, contact angle etc. with different precursor flow rates of DLN films.

  13. Kinetic Effects on Self-Assembly and Function of Protein-Polymer Bioconjugates in Thin Films Prepared by Flow Coating

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Dongsook [Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave Cambridge MA 02142 USA; Huang, Aaron [Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave Cambridge MA 02142 USA; Olsen, Bradley D. [Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave Cambridge MA 02142 USA

    2016-11-04

    The self-assembly of nanostructured globular protein arrays in thin films is demonstrated using protein–polymer block copolymers based on a model protein mCherry and the polymer poly(oligoethylene glycol acrylate) (POEGA). Conjugates are flow coated into thin films on a poly(ethylene oxide) grafted Si surface, forming self-assembled cylindrical nanostructures with POEGA domains selectively segregating to the air–film interface. Long-range order and preferential arrangement of parallel cylinders templated by selective surfaces are demonstrated by controlling relative humidity. Long-range order increases with coating speed when the film thicknesses are kept constant, due to reduced nucleation per unit area of drying film. Fluorescence emission spectra of mCherry in films prepared at <25% relative humidity shows a small shift suggesting that proteins are more perturbed at low humidity than high humidity or the solution state.

  14. On the effect of water film on flow-induced pulsations in closed side branches in tandem configuration

    NARCIS (Netherlands)

    Sanna, F.; Golliard, J.; Belfroid, S.P.C.

    2015-01-01

    Previous studies demonstrate that the presence of liquid strongly influences the pressure pulsation amplitudes of flow induced pulsations. In particular, in case of annular flow (thin liquid film on the walls) the pulsations can be eliminated. The present study aims at evaluating the contribution of

  15. Burn-out, Circumferential Film Flow Distribution and Pressure Drop for an Eccentric Annulus with Heated Rod

    DEFF Research Database (Denmark)

    Andersen, P. S.; Jensen, A.; Mannov, G.

    1974-01-01

    Measurements of (1) burn-out, (2) circumferential film flow distribution, and (3) pressure drop in a 17 × 27.2 × 3500 mm concentric and eccentric annulus geometry are presented. The eccentric displacement was varied between 0 and 3 mm. The working fluid was water. Burn-out curves at 70 bar...... flow variation on burn-out is discussed....

  16. Dynamics of a thin film flowing down a heated wall with finite thermal diffusivity

    Science.gov (United States)

    Dallaston, Michael C.; Tseluiko, Dmitri; Kalliadasis, Serafim

    2016-11-01

    Consider the dynamics of a thin film flowing down a heated substrate. The substrate heating generates a temperature distribution on the free surface, which in turn induces surface-tension gradients and corresponding thermocapillary stresses that affect the free surface and therefore the fluid flow. We study here the effect of finite substrate thermal diffusivity on the film dynamics. Linear stability analysis of the full Navier-Stokes and heat transport equations indicates if the substrate diffusivity is sufficiently small, the film becomes unstable at a finite wavelength and at a Reynolds number smaller than that predicted in the long-wavelength limit. This property is captured in a reduced-order system of equations derived using a weighted-residual integral-boundary-layer method. This reduced-order model is also used to compute the bifurcation diagrams of solution branches connecting the trivial flat film to traveling waves including solitary pulses. The effect of finite diffusivity is to separate a simultaneous Hopf-transcritical bifurcation into its individual component bifurcations. The appropriate Hopf bifurcation then connects only to the solution branch of negative-hump pulses, with wave speed less than the linear wave speed, while the branch of positive-single-hump pulses merges with the branch of positive-two-hump pulses at a supercritical Reynolds number. In the regime where finite-wavelength instability occurs, there exists a Hopf-bifurcation pair connected by a branch of periodic solutions, whose period cannot be increased indefinitely. Numerical simulation of the reduced-order system shows the development of a train of coherent structures, each of which resembles a stationary positive-hump pulse, and, in the regime of finite-wavelength instability, wavelength selection and saturation to periodic traveling waves.

  17. Film stability in a vertical rotating tube with a core-gas flow.

    Science.gov (United States)

    Sarma, G. S. R.; Lu, P. C.; Ostrach, S.

    1971-01-01

    The linear hydrodynamic stability of a thin-liquid layer flowing along the inside wall of a vertical tube rotating about its axis in the presence of a core-gas flow is examined. The stability problem is formulated under the conditions that the liquid film is thin, the density and viscosity ratios of gas to liquid are small and the relative (axial) pressure gradient in the gas is of the same order as gravity. The resulting eigenvalue problem is first solved by a perturbation method appropriate to axisymmetric long-wave disturbances. The damped nature (to within the thin-film and other approximations made) of the nonaxisymmetric and short-wave disturbances is noted. In view of the limitations on a truncated perturbation solution when the disturbance wavenumber is not small, an initial value method using digital computer is presented. Stability characteristics of neutral, growing, and damped modes are presented showing the influences of rotation, surface tension, and the core-gas flow. Energy balance in a neutral mode is also illustrated.

  18. Characterization of Dispersive Fluxes in Mesoscale Models Using LES of Flow over an Array of Cubes

    Directory of Open Access Journals (Sweden)

    Adil Rasheed

    2013-01-01

    Full Text Available Field studies have shown that local climate is strongly influenced by urban structures. This influences both energy consumption and the pedestrian comfort. It is thus useful to be able to simulate the urban environment to take these effects into account in building and urban design. But for computational reasons, conventional computational fluid dynamics (CFD codes cannot be used directly on a grid fine enough to resolve all scales found in a city. For this, we use mesoscale models, variants of CFD codes in which the 3D conservation equations are solved on grids having a resolution of a few kilometers. At this resolution, the effects of subgrid scales need implicit representations. In other words, phenomena such as momentum and energy exchanges averaged over the mesoscale grid contribute necessary sources/sinks to the corresponding equations. Such spatial averaging results in additional terms called dispersive fluxes. Until now these fluxes have been ignored. To better understand these fluxes, we have conducted large eddy simulations (LESs over an array of cubes for different inter-cube spacings. The study shows that these fluxes are as important as the turbulent fluxes and exhibit trends which are related to the eddy formations inside the canopies.

  19. Linear stability analysis of immiscible two-phase flow in porous media with capillary dispersion and density variation

    Science.gov (United States)

    Riaz, Amir; Tchelepi, Hamdi A.

    2004-12-01

    Linear stability analysis of immiscible displacements is carried out for both viscously and gravitationally unstable two-phase flows in porous media with very large adverse viscosity ratios. Capillary dispersion is the proper dissipative mechanism in this case which sets both the preferred length scale and the band width of the spectrum of unstable length scales. The growth rate, the most dangerous and the cutoff wavenumbers, all scale linearly with the capillary number. We show that the instability is governed by fluid properties across the shock rather than those across the full Buckley-Leverett profile. The shock total mobility ratio provides a sufficient condition for the onset of instability; however, it is not an appropriate criterion for predicting the magnitude of the growth rate, particularly for large viscosity ratios. The details of the relative permeability functions are observed to have a significant influence on the stability characteristics. For neutrally buoyant flows the maximum growth rate scales linearly with the viscosity ratio while the most dangerous and the cutoff wavenumbers scale with the square root of the viscosity ratio. In the case of displacements with density contrast, the maximum growth rate scales with the square of the unstable gravity number while the most dangerous and the cutoff wavenumbers scale with an exponent of 1.2, for all viscosity ratios. A marginal stability curve is computed for stable and unstable regions in the parameter space of the viscosity ratio and the gravity number. It is found that flows with unstable viscosity contrasts are more readily stabilized with buoyancy as compared to the viscous stabilization of gravitationally unstable flows.

  20. Optimization of hydrogen dispersion in thermophilic up-flow reactors for ex situ biogas upgrading

    DEFF Research Database (Denmark)

    Bassani, Ilaria; Kougias, Panagiotis; Treu, Laura

    2017-01-01

    This study evaluates the efficiency of four novel up-flow reactors for ex situ biogas upgrading converting externally provided CO2 and H2 to CH4, via hydrogenotrophic methanogenesis. The gases were injected through stainless steel diffusers combined with alumina ceramic sponge or through alumina...... and CO2, up to 3.6L/LREACTOR·d H2 loading rate. Specifically, reactors' CH4 content increased from 23 to 96% and the CH4 yield reached 0.25LCH4/LH2. High throughput 16S rRNA gene sequencing revealed predominance of bacteria belonging to Anaerobaculum genus and to uncultured order MBA08. Additionally...

  1. New Approaches in Modeling Multiphase Flows and Dispersion in Turbulence, Fractal Methods and Synthetic Turbulence

    CERN Document Server

    Nicolleau, FCGA; Redondo, J-M

    2012-01-01

    This book contains a collection of the main contributions from the first five workshops held by Ercoftac Special Interest Group on Synthetic Turbulence Models (SIG42. It is intended as an illustration of the sig's activities and of the latest developments in the field. This volume investigates the use of Kinematic Simulation (KS) and other synthetic turbulence models for the particular application to environmental flows. This volume offers the best syntheses on the research status in KS, which is widely used in various domains, including Lagrangian aspects in turbulence mixing/stirring, partic

  2. Studies on effect of oxygen flow rate in textured grain growth of ZnO thin films

    Science.gov (United States)

    Thomas, Deepu; Vattappalam, Sunil C.; Mathew, Sunny; Augustine, Simon

    2015-02-01

    ZnO thin films were deposited on glass substrate by Successive Ionic Layer Adsorption Reaction (SILAR) method. Effect of oxygen flow rate in textured grain growth, resistance and band gap of the thin films have been done. Textured grain growth of the samples were measured by comparing the peak intensities from XRD. Textured grain growth was found to be maximum when the oxygen flow rate is 2.5 litre/minute. It is found that as the oxygen flow rate increases above this limit, textured grain growth decreases and resistance the samples increases. The optical band gap of ZnO film was found to be increased with the increase of oxygen flow rate.

  3. Optimization of hydrogen dispersion in thermophilic up-flow reactors for ex situ biogas upgrading.

    Science.gov (United States)

    Bassani, Ilaria; Kougias, Panagiotis G; Treu, Laura; Porté, Hugo; Campanaro, Stefano; Angelidaki, Irini

    2017-06-01

    This study evaluates the efficiency of four novel up-flow reactors for ex situ biogas upgrading converting externally provided CO2 and H2 to CH4, via hydrogenotrophic methanogenesis. The gases were injected through stainless steel diffusers combined with alumina ceramic sponge or through alumina ceramic membranes. Pore size, input gas loading and gas recirculation flow rate were modulated to optimize gas-liquid mass transfer, and thus methanation efficiency. Results showed that larger pore size diffusion devices achieved the best kinetics and output-gas quality converting all the injected H2 and CO2, up to 3.6L/LREACTOR·d H2 loading rate. Specifically, reactors' CH4 content increased from 23 to 96% and the CH4 yield reached 0.25LCH4/LH2. High throughput 16S rRNA gene sequencing revealed predominance of bacteria belonging to Anaerobaculum genus and to uncultured order MBA08. Additionally, the massive increase of hydrogenotrophic methanogens, such as Methanothermobacter thermautotrophicus, and syntrophic bacteria demonstrates the selection-effect of H2 on community composition. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Thin film flow in MHD third grade fluid on a vertical belt with temperature dependent viscosity.

    Directory of Open Access Journals (Sweden)

    Taza Gul

    Full Text Available In this work, we have carried out the influence of temperature dependent viscosity on thin film flow of a magnetohydrodynamic (MHD third grade fluid past a vertical belt. The governing coupled non-linear differential equations with appropriate boundary conditions are solved analytically by using Adomian Decomposition Method (ADM. In order to make comparison, the governing problem has also been solved by using Optimal Homotopy Asymptotic Method (OHAM. The physical characteristics of the problem have been well discussed in graphs for several parameter of interest.

  5. Thin film flow in MHD third grade fluid on a vertical belt with temperature dependent viscosity.

    Science.gov (United States)

    Gul, Taza; Islam, Saed; Shah, Rehan Ali; Khan, Ilyas; Shafie, Sharidan

    2014-01-01

    In this work, we have carried out the influence of temperature dependent viscosity on thin film flow of a magnetohydrodynamic (MHD) third grade fluid past a vertical belt. The governing coupled non-linear differential equations with appropriate boundary conditions are solved analytically by using Adomian Decomposition Method (ADM). In order to make comparison, the governing problem has also been solved by using Optimal Homotopy Asymptotic Method (OHAM). The physical characteristics of the problem have been well discussed in graphs for several parameter of interest.

  6. Vortex lattice ordering in the flux flow state of Nb thin films

    Energy Technology Data Exchange (ETDEWEB)

    Grimaldi, Gaia, E-mail: gaia.grimaldi@cnr.i [CNR-SPIN, V. Ponte Don Melillo, Fisciano I-84084 (Italy); Leo, Antonio [CNR-SPIN, V. Ponte Don Melillo, Fisciano I-84084 (Italy); Nigro, Angela; Pace, Sandro [CNR-SPIN, V. Ponte Don Melillo, Fisciano I-84084 (Italy); Physics Department ' E. R. Caianiello' , University of Salerno, V. Ponte Don Melillo, Fisciano I-84084 (Italy)

    2010-10-01

    We measure current-voltage characteristics at high driving currents for different magnetic fields and temperatures in Nb thin films of rather strong pinning. In a definite range of the B-T phase diagram we find that a current induced transition occurs in the flux flow motion of the vortex lattice, namely a dynamic ordering (DO). Contrary to the case of weaker pinning materials, DO is observed only at low fields, due to the stronger intrinsic disorder that can deform plastically the moving vortex lattice even for small applied fields.

  7. Study of flow and dispersion of pollutants in the Igap\\'o I Lake

    CERN Document Server

    Romeiro, Neyva Maria Lopes; Natti, Paulo Laerte

    2010-01-01

    This work proposes a mathematical model on the water quality for Igap\\'o I Lake, located in Londrina, Paran\\'a. A qualitative analysis on the pollution of the lake is carried out through numerical simulations which provide informations for the understanding of the processes involved. For the hydrodynamic flow of the lake, a horizontal two-dimensional model is considered. The hydrodynamic velocity field is simulated by the Navier-Stokes and pressure equations, supposing an incompressible newtonian fluid. This hydrodynamic velocity field is inserted in the reactive-transport model. The reactive part of this model considers only the carbon-nitrogen cycle, described by the QUAL2E model. A qualitative and quantitative analysis of the numerical simulations conducted in function of the deficit of dissolved oxygen, of the biochemical oxygen demand and of the load of pollutants provided a better understanding of the hydrology and of the water quality in the Igap\\'o I Lake.

  8. Pulsing frequency induced change in optical constants and dispersion energy parameters of WO{sub 3} films grown by pulsed direct current magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Punitha, K. [Department of Physics, Alagappa University, Karaikudi 630 004 (India); Sivakumar, R., E-mail: krsivakumar1979@yahoo.com [Directorate of Distance Education, Alagappa University, Karaikudi 630 004 (India); Sanjeeviraja, C. [Department of Physics, Alagappa Chettiar College of Engineering and Technology, Karaikudi 630 004 (India)

    2014-03-21

    In this work, we present the pulsing frequency induced change in the structural, optical, vibrational, and luminescence properties of tungsten oxide (WO{sub 3}) thin films deposited on microscopic glass and fluorine doped tin oxide (SnO{sub 2}:F) coated glass substrates by pulsed dc magnetron sputtering technique. The WO{sub 3} films deposited on SnO{sub 2}:F substrate belongs to monoclinic phase. The pulsing frequency has a significant influence on the preferred orientation and crystallinity of WO{sub 3} film. The maximum optical transmittance of 85% was observed for the film and the slight shift in transmission threshold towards higher wavelength region with increasing pulsing frequency revealed the systematic reduction in optical energy band gap (3.78 to 3.13 eV) of the films. The refractive index (n) of films are found to decrease (1.832 to 1.333 at 550 nm) with increasing pulsing frequency and the average value of extinction coefficient (k) is in the order of 10{sup −3}. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (E{sub d}) parameters, dielectric constants, plasma frequency, oscillator strength, and oscillator energy (E{sub o}) of WO{sub 3} films were calculated and reported for the first time due to variation in pulsing frequency during deposition by pulsed dc magnetron sputtering. The E{sub o} is change between 6.30 and 3.88 eV, while the E{sub d} varies from 25.81 to 7.88 eV, with pulsing frequency. The Raman peak observed at 1095 cm{sup −1} attributes the presence of W-O symmetric stretching vibration. The slight shift in photoluminescence band is attributed to the difference in excitons transition. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.

  9. Comparison of Surfactant Distributions in Pressure-Sensitive Adhesive Films Dried from Dispersion under Lab-Scale and Industrial Drying Conditions.

    Science.gov (United States)

    Baesch, S; Siebel, D; Schmidt-Hansberg, B; Eichholz, C; Gerst, M; Scharfer, P; Schabel, W

    2016-03-01

    Film-forming latex dispersions are an important class of material systems for a variety of applications, for example, pressure-sensitive adhesives, which are used for the manufacturing of adhesive tapes and labels. The mechanisms occurring during drying have been under intense investigations in a number of literature works. Of special interest is the distribution of surfactants during the film formation. However, most of the studies are performed at experimental conditions very different from those usually encountered in industrial processes. This leaves the impact of the drying conditions and the resulting influence on the film properties unclear. In this work, two different 2-ethylhexyl-acrylate (EHA)-based adhesives with varying characteristics regarding glass transition temperature, surfactants, and particle size distribution were investigated on two different substrates. The drying conditions, defined by film temperature and mass transfer in the gas phase, were varied to emulate typical conditions encountered in the laboratory and industrial processes. Extreme conditions equivalent to air temperatures up to 250 °C in a belt dryer and drying rates of 12 g/(m(2)·s) were realized. The surfactant distributions were measured by means of 3D confocal Raman spectroscopy in the dry film. The surfactant distributions were found to differ significantly with drying conditions at moderate film temperatures. At elevated film temperatures the surfactant distributions are independent of the investigated gas side transport coefficients: the heat and mass transfer coefficient. Coating on substrates with significantly different surface energies has a large impact on surfactant concentration gradients, as the equilibrium between surface and bulk concentration changes. Dispersions with higher colloidal stability showed more homogeneous lateral surfactant distributions. These results indicate that the choice of the drying conditions, colloidal stability, and substrates is crucial

  10. Impact of polymer film thickness and cavity size on polymer flow during embossing : towards process design rules for nanoimprint lithography.

    Energy Technology Data Exchange (ETDEWEB)

    Schunk, Peter Randall; King, William P. (Georgia Institute of Technology, Atlanta, GA); Sun, Amy Cha-Tien; Rowland, Harry D. (Georgia Institute of Technology, Atlanta, GA)

    2006-08-01

    This paper presents continuum simulations of polymer flow during nanoimprint lithography (NIL). The simulations capture the underlying physics of polymer flow from the nanometer to millimeter length scale and examine geometry and thermophysical process quantities affecting cavity filling. Variations in embossing tool geometry and polymer film thickness during viscous flow distinguish different flow driving mechanisms. Three parameters can predict polymer deformation mode: cavity width to polymer thickness ratio, polymer supply ratio, and Capillary number. The ratio of cavity width to initial polymer film thickness determines vertically or laterally dominant deformation. The ratio of indenter width to residual film thickness measures polymer supply beneath the indenter which determines Stokes or squeeze flow. The local geometry ratios can predict a fill time based on laminar flow between plates, Stokes flow, or squeeze flow. Characteristic NIL capillary number based on geometry-dependent fill time distinguishes between capillary or viscous driven flows. The three parameters predict filling modes observed in published studies of NIL deformation over nanometer to millimeter length scales. The work seeks to establish process design rules for NIL and to provide tools for the rational design of NIL master templates, resist polymers, and process parameters.

  11. Determination and analysis of dispersive optical constant of TiO{sub 2} and Ti{sub 2}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Aziz, M.M. [Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt)]. E-mail: melaziz@link.net; Yahia, I.S. [Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Wahab, L.A. [Physics Department, National Center for Radiation Research and Technology, Naser City, Cairo (Egypt); Fadel, M. [Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Afifi, M.A. [Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt)

    2006-09-30

    Electron beam evaporation technique was used to prepare TiO{sub 2} and Ti{sub 2}O{sub 3} thin films onto glass substrates of thicknesses 50, 500 and 1000nm for each sample. The structural investigations revealed that the as-deposited films are amorphous in nature. Transmittance measurements in the wavelength range (350-2000nm) were used to calculate the refractive index n and the absorption index k using Swanepoel's method. The optical constants such as optical band gap E{sub g}{sup opt}, optical conductivity {sigma}{sub opt}, complex dielectric constant, relaxation time {tau} and dissipation factor tan{delta} were determined. The analysis of the optical absorption data revealed that the optical band gap E{sub g} was indirect transitions. The optical dispersion parameters E{sub o} and E{sub d} were determined according to Wemple and Didomenico method.

  12. Optical band gap and refractive index dispersion parameters of As x Se70Te30- x (0≤ x≤30 at.%) amorphous films

    Science.gov (United States)

    Aly, Kamal A.

    2010-06-01

    Amorphous As x Se70Te30- x thin films with (0≤ x≤30 at.%) were deposited onto glass substrates by using thermal evaporation method. The transmission spectra T( λ) of the films at normal incidence were measured in the wavelength range 400-2500 nm. A straightforward analysis proposed by Swanepoel based on the use of the maxima and minima of the interference fringes has been used to drive the film thickness, d, the complex index of refraction, n, and the extinction coefficient, k. The dispersion of the refractive index is discussed in terms of the single-oscillator Wemple and DiDomenico model (WDD). Increasing As content is found to affect the refractive index and the extinction coefficient of the As x Se70Te30- x films. With increasing As content the optical band gap increases while the refractive index decreases. The optical absorption is due to allowed indirect transition. The chemical bond approach has been applied successfully to interpret the increase of the optical gap with increasing As content.

  13. Highly sensitive response to dopamine at a modified electrode involving a composite film with Au nanoparticles dispersed in a fluorocarbon polymer

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A new approach for the highly sensitive detection of dopamine by a novel composite film involving gold nanoparticles trapped in a negatively-charged fluorocarbon polymer (Nafion) on a glassy carbon (GC) electrode fabricated by a simple method is described. Gold nanoparticles with an average diameter of 2.3 nm ± 0.2 nm are dispersed throughout the whole Nafion film. The introduction of gold nanoparticles into the Nafion film not only gives a highly active electrode surface area but also increases the conductivity of the Nafion film and the resulting Au/Nafion/GC electrode combines the advantages of the properties of gold nanoparticles and the selective pre-concentration ability of Nafion. For positively charged dopamine, the results show a decrease in the redox peak separation and a high sensitivity. The oxidation peak current of dopamine was shown to vary linearly with dopamine concentration over a wide range from 0.4 to 50.0 μmol/L with a detection limit of 0.3 μmol/L. Negatively charged ascorbic acid shows no redox waves at concentrations up to 1.0 ×10-4 mol/L.

  14. Acid yellow 9 as a dispersing agent for carbon nanotubes: preparation of redox polymer-carbon nanotube composite film and its sensing application towards ascorbic acid and dopamine.

    Science.gov (United States)

    Kumar, S Ashok; Wang, Sea-Fue; Yang, Thomas C-K; Yeh, Chun-Ting

    2010-08-15

    In this study, we show that acid yellow 9 (4-amino-1-1'-azobenzene-3,4'-disulfonicacid, AY) is a good stabilizing agent for multi-walled carbon nanotubes (MWCNTs). MWCNTs dispersed in AY solution was remained stable about three months and even remained stable after centrifugation at 10,000 rpm for 30 min. Using MWCNTs/AY dispersion, thin-films were prepared on indium tin oxide coated glass electrode and glassy carbon electrodes. Further, dried films of MWCNTs/AY were subjected to electropolymerization in 0.1M H(2)SO(4) solution. Adsorbed AY molecules on MWCNTs get polymerized and they yield a polymer-MWCNTs nanocomposite film on electrode surface which is found to be electrochemically active in wide pH range (1-11). Characterization studies were performed using cyclic voltammetry and SEM. These studies are supported that hybrid material PAY/MWCNTs was obtained. Moreover, newly synthesized PAY-MWCNTs composite film showed excellent electrocatalytic activity towards oxidation of dopamine (DA) and ascorbic acid (AA) with high sensitivity in physiological pH. Linear sweep voltammetry was employed to the determination of DA in the presence of AA in the range of 2x10(-7) to 1.4x10(-6) M. Amperometry was employed to determination of AA at 0.0 V in the range from 1x10(-6) to 5.6x10(-5) M, and DA, uric acid are not interfered on the steady-state current of AA. In addition, real samples such as dopamine injection and AA spiked into human urine were analyzed using PAY/MWCNTs composite modified electrode and satisfactory results were obtained.

  15. Appliance of Inertial Gas-Dynamic Separation of Gas-Dispersion Flows in the Curvilinear Convergent-Divergent Channels for Compressor Equipment Reliability Improvement

    Science.gov (United States)

    Liaposhchenko, O. O.; Sklabinskyi, V. I.; Zavialov, V. L.; Pavlenko, I. V.; Nastenko, O. V.; Demianenko, M. M.

    2017-08-01

    The new methods of vibration and inertial gas-dynamic separation of gas-condensate and dusty flows and the corresponding separation devices are proposed in order to avoid emergencies and premature wear of parts and components of the compressor equipment. The formation of the gas flow and disperse particles in the curvilinear convergent-divergent channels are investigated. The optimizing hydrodynamic profiling of a geometrical configuration of curvilinear separation channels with rigid and flexible walls of baffles is carried out.

  16. Global Skin-Friction Measurements Using Particle Image Surface FLow Visualization and a Luminescent Oil-Film

    Science.gov (United States)

    Husen, Nicholas; Roozeboom, Nettie; Liu, Tianshu; Sullivan, John P.

    2015-01-01

    A quantitative global skin-friction measurement technique is proposed. An oil-film is doped with a luminescent molecule and thereby made to fluoresce in order to resolve oil-film thickness, and Particle Image Surface Flow Visualization is used to resolve the velocity field of the surface of the oil-film. Skin-friction is then calculated at location x as (x )xh, where x is the displacement of the surface of the oil-film and is the dynamic viscosity of the oil. The data collection procedure and data analysis procedures are explained, and preliminary experimental skin-friction results for flow over the wing of the CRM are presented.

  17. Electroanalysis of tetracycline using nickel-implanted boron-doped diamond thin film electrode applied to flow injection system.

    Science.gov (United States)

    Treetepvijit, Surudee; Chuanuwatanakul, Suchada; Einaga, Yasuaki; Sato, Rika; Chailapakult, Orawon

    2005-05-01

    The electrochemical analysis of tetracycline was investigated using nickel-implanted boron-doped diamond thin film electrode by cyclic voltammetry and amperometry with a flow injection system. Cyclic voltammetry was used to study the electrochemical oxidation of tetracycline. Comparison experiments were carried out using as-deposited boron-doped diamond thin film electrode (BDD). Nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) provided well-resolved oxidation irreversible cyclic voltammograms. The current signals were higher than those obtained using the as-deposited BDD electrode. Results using nickel-implanted boron-doped diamond thin film electrode in flow injection system coupled with amperometric detection are presented. The optimum potential for tetracycline was 1.55 V versus Ag/AgCl. The linear range of 1.0 to 100 microM and the detection limit of 10 nM were obtained. In addition, the application for drug formulation was also investigated.

  18. Instabilities of a liquid film flowing down an inclined porous plane

    Science.gov (United States)

    Liu, Rong; Liu, Qiusheng

    2009-09-01

    The problem of a film flowing down an inclined porous layer is considered. The fully developed basic flow is driven by gravitation. A careful linear instability analysis is carried out. We use Darcy’s law to describe the porous layer and solve the coupling equations of the fluid and the porous medium rather than the decoupled equations of the one-sided model used in previous works. The eigenvalue problem is solved by means of a Chebyshev collocation method. We compare the instability of the two-sided model with the results of the one-sided model. The result reveals a porous mode instability which is completely neglected in previous works. For a falling film on an inclined porous plane there are three instability modes, i.e., the surface mode, the shear mode, and the porous mode. We also study the influences of the depth ratio d̂ , the Darcy number δ , and the Beavers-Joseph coefficient αBJ on the instability of the system.

  19. Intercomparison of dispersed radiation readings among film dosimetry, electronic and OSL with X-rays for low dose; Intercomparacion de lecturas de radiacion dispersa entre dosimetria film, electronica y OSL con rayos X para dosis bajas

    Energy Technology Data Exchange (ETDEWEB)

    Andisco, D. [Universidad de Buenos Aires, Facultad de Medicina, Paraguay 2155, C1121AAA Buenos Aires (Argentina); Blanco, S. [CONICET, Saavedra 15, C1083ACA Buenos Aires (Argentina); Bourel, V.; Schmidt, L. [Universidad Favaloro, Facultad de Ciencias e Ingenieria, Solis 453, C1078AAI, Buenos Aires (Argentina); Di Risio, C., E-mail: dandisco@fmed.uba.ar [Universidad de Belgrano, Facultad de Ingenieria, Zabala 1837, C1426DQG, Buenos Aires (Argentina)

    2014-08-15

    One of the personal dosimetry methods more used for several decades is the dosimetry type film, characterized to possess readings with certain margin of trust. Today other methods exist that many times are presupposed more reliable due to the nature of the detection like the electronic dosimeters or the OSL (Optically Stimulated Luminescence) dosimetry. With the purpose of comparing different methods and to can determining the existent differences among each method has been carried out an intercomparison assay. The different dosimeters have been exposed to dispersed radiation generated by a Hemodynamics equipment of the type -arch in C- and a dispersing system of the primary beam. Film dosimeters have been used; OSL (In Light), OSL (Nano Dots) and Electronic with the purpose of knowing and to valorize the existent differences among its readings. Always, the intercomparison exercises have demonstrated to be an useful tool when establishing the measurement capacity and the quality of the results emitted by the laboratories of personal dosimetry services. Also, this type of assays allows obtaining quality indicators of the laboratory performance and they are habitual part of the procedures for accreditation of the same ones. The Optically Stimulated Luminescence is a technology that has grown in Argentina so much in the area of personal dosimetry as in dosimetry in vivo (radiotherapy area). In this intercomparison study, the answers corresponding to each technology were looked for oneself irradiation of the disperse type, that is to say, of very low energy. (Author)

  20. Steady film flow over 2D topography with air inclusion formed inside the trench

    Science.gov (United States)

    Tsamopoulos, John; Varchanis, Stylianos; Dimakopoulos, Yannis

    2016-11-01

    Liquid film flow along an inclined, solid substrate featuring periodic rectangular trenches may either completely wet the trench floor (Wenzel state) or pin on the entrance and exit corners of the trench (Cassie state) or assume any other configuration in between these two extremes. In the intermediate cases a second gas-liquid interface inside the trench is formed, which adheres to the walls of the trench forming two three-phase contact lines, and encloses a different amount of air under different physical conditions. The Galerkin finite element method is used to solve the Navier-Stokes equations in a physical domain, which is adaptively re-meshed. Multiple steady solutions, connected by turning points and transcritical bifurcations as well as isolated solution branches, are revealed by pseudo arc-length continuation. Two possible cases of a single air inclusion inside the trench are examined. The penetration of the liquid inside the trench is enhanced primarily by increasing either the wettability of the substrate or the capillarity or by decreasing the flow rate. Flow hysteresis may occur when the liquid does not penetrate deep enough inside the trench leading to different flow patterns. The interplay of inertia, viscous, gravity and capillary forces along with substrate wettability determines the volume of the air encapsulated in the trench and the extent of free surface deformation. GSRT of Greece via the program "Excellence" and the LIMMAT foundation.

  1. Effect of Coolant Temperature and Mass Flow on Film Cooling of Turbine Blades

    Science.gov (United States)

    Garg, Vijay K.; Gaugler, Raymond E.

    1997-01-01

    A three-dimensional Navier Stokes code has been used to study the effect of coolant temperature, and coolant to mainstream mass flow ratio on the adiabatic effectiveness of a film-cooled turbine blade. The blade chosen is the VKI rotor with six rows of cooling holes including three rows on the shower head. The mainstream is akin to that under real engine conditions with stagnation temperature = 1900 K and stagnation pressure = 3 MPa. Generally, the adiabatic effectiveness is lower for a higher coolant temperature due to nonlinear effects via the compressibility of air. However, over the suction side of shower-head holes, the effectiveness is higher for a higher coolant temperature than that for a lower coolant temperature when the coolant to mainstream mass flow ratio is 5% or more. For a fixed coolant temperature, the effectiveness passes through a minima on the suction side of shower-head holes as the coolant to mainstream mass flow, ratio increases, while on the pressure side of shower-head holes, the effectiveness decreases with increase in coolant mass flow due to coolant jet lift-off. In all cases, the adiabatic effectiveness is highly three-dimensional.

  2. Flow injection analysis using carbon film resistor electrodes for amperometric determination of ambroxol.

    Science.gov (United States)

    Felix, Fabiana S; Brett, Christopher M A; Angnes, Lúcio

    2008-06-30

    Flow injection analysis (FIA) using a carbon film sensor for amperometric detection was explored for ambroxol analysis in pharmaceutical formulations. The specially designed flow cell designed in the lab generated sharp and reproducible current peaks, with a wide linear dynamic range from 5x10(-7) to 3.5x10(-4) mol L(-1), in 0.1 mol L(-1) sulfuric acid electrolyte, as well as high sensitivity, 0.110 Amol(-1) L cm(-2) at the optimized flow rate. A detection limit of 7.6x10(-8) mol L(-1) and a sampling frequency of 50 determinations per hour were achieved, employing injected volumes of 100 microL and a flow rate of 2.0 mL min(-1). The repeatability, expressed as R.S.D. for successive and alternated injections of 6.0x10(-6) and 6.0x10(-5) mol L(-1) ambroxol solutions, was 3.0 and 1.5%, respectively, without any noticeable memory effect between injections. The proposed method was applied to the analysis of ambroxol in pharmaceutical samples and the results obtained were compared with UV spectrophotometric and acid-base titrimetric methods. Good agreement between the results utilizing the three methods and the labeled values was achieved, corroborating the good performance of the proposed electrochemical methodology for ambroxol analysis.

  3. Numerical simulation of fluid flow and heat transfer in a thin liquid film over a rotating disk

    Science.gov (United States)

    Rahman, M. M.; Faghri, A.

    1992-01-01

    The results of a numerical simulation of the flow field and associated heat transfer coefficient are presented for the free surface flow of a thin liquid film adjacent to a horizontal rotating disk. The computation has been performed for different flow rates and rotational velocities using a three-dimensional boundary-fitted coordinate system. Since the geometry of the free surface is unknown and dependent on flow rate, rate of rotation, and other parameters, an interative procedure had to be used to ascertain its location. The computed film height agreed well with existing experimental measurements. The flow was dominated by inertia near the entrance and close to the free surface, and dominated by centrifugal force at larger radii and adjacent to the disk. The rotation enhanced the heat transfer coefficient by a significant amount.

  4. Numerical Simulation of Particle Mixing in Dispersed Gas-Liquid-Solid Flows using a Combined Volume of Fluid and Discrete Particle Approach

    NARCIS (Netherlands)

    Deen, Niels G.; Sint Annaland, van Martin; Kuipers, J.A.M.

    2007-01-01

    In this paper a hybrid model is presented for the numerical simulation of gas-liquid-solid flows using a combined Volume Of Fluid (VOF) and Discrete Particle (DP) approach applied for respectively dispersed gas bubbles and solid particles present in the continuous liquid phase. The hard sphere DP mo

  5. Direct numerical simulation of particle mixing in dispersed gas-liquid-solid flows using a combined volume of fluid and discrete particle approach

    NARCIS (Netherlands)

    Deen, Niels G.; Sint Annaland, van Martin; Kuipers, J.A.M.

    2006-01-01

    In this paper a hybrid model is presented for the numerical simulation of gas-liquid-solid flows using a combined Volume Of Fluid (VOF) and Discrete Particle (DP) approach applied for respectively dispersed gas bubbles and solid particles present in the continuous liquid phase. The hard sphere DP mo

  6. Fabrication of hydrogenated amorphous silicon carbide films by decomposition of hexamethyldisilane with microwave discharge flow of Ar

    Science.gov (United States)

    Ito, Haruhiko; Kumakura, Motoki; Suzuki, Tsuneo; Niibe, Masahito; Kanda, Kazuhiro; Saitoh, Hidetoshi

    2016-06-01

    Hydrogenated amorphous silicon carbide films have been fabricated by the decomposition of hexamethyldisilane with a microwave discharge flow of Ar. Mechanically hard films were obtained by applying radio-frequency (RF) bias voltages to the substrate. The atomic compositions of the films were analyzed by a combination of Rutherford backscattering and elastic recoil detection, X-ray photoelectron spectroscopy (XPS), and glow discharge optical emission spectroscopy. The chemical structure was analyzed by carbon-K near-edge X-ray absorption fine structure spectroscopy, high-resolution XPS, and Fourier transform infrared absorption spectroscopy. The structural changes upon the application of RF bias were investigated, and the concentration of O atoms near the film surface was found to play a key role in the mechanical hardness of the present films.

  7. Using Radiochromic Films to Characterize the Dispersion of ZrO{sub 2} Nano-sized Grain Clusters in Protective Polymer Composites

    Energy Technology Data Exchange (ETDEWEB)

    Fontainha, C.C.P.; Nolasco, A.V. [Depto. de Engenharia Nuclear - DEN / UFMG - MG, Av. Antonio Carlos 6627, 31270-970 Belo Horizonte, MG (Brazil); Santos, A.P.; Faria, L.O. [Centro de Desenvolvimento da Tecnologia Nuclear, Av. Antonio Carlos 6627, C.P. 941, 30270-901, Belo Horizonte, MG (Brazil)

    2015-07-01

    . This result is discussed in terms of the high Z halides added to the sensitive layer of EB3 film, once the main components are C (42.3%), H (39.7%) and O (16.0%)1-2. Based on the above results, we have speculated about the abilities of XR-AQ films in the detection of the distribution of nano-sized particles that has high mass-energy attenuation coefficients for low energy x-rays, in polymer composites. In another investigation we tested the ability of XR-QA2 Gafchromic{sup R} films to evaluate the dispersion of ZrO{sub 2} nano-sized grain clusters in protective composites. The P(VDFTrFE)/ ZrO{sub 2} film was sandwiched between two XR-QA2 radiochromic films. In this setup, one radiochromic film is directly exposed to 100 mGy of the x-rays beam and another one measures the attenuated beam. After storage for 24 hours at room temperature under no light conditions, the irradiated radiochromic films were scanned under the same conditions in order to obtain a more reliable result. All films were scanned using the same size ROI in high resolution mode and saved as tagged image file format (TIFF). The untreated scanned image of the XR-AQ2 film directed exposed to the X-ray beam and the correspondent treated image with digital filters are shown. The untreated and treated image of the XR-AQ2 film that was exposed to the attenuated x-ray beam is shown. The image treated with digital filters seems to reproduce the dispersion of ZrO{sub 2} nano-sized grain clusters in the P(VDF-TrFE) copolymer matrix. This result is also discussed in terms of the high Z halides added to the sensitive layer of XR-AQ2 film and compared to the MEV images obtained from the P(VDF-TrFE)/ZrO{sub 2} composites. The results indicate a clear correlation between the 2D radiochromic image and the MEV photography.

  8. All-optical logic gate based on transient grating from disperse red 1 doped organic-inorganic hybrid films with an improved figure of merit

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Tianxi; Que, Wenxiu, E-mail: wxque@mail.xjtu.edu.cn; Shao, Jinyou [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, International Center for Dielectric Research, School of Electronic and Information Engineering, State Key Laboratory for Manufacturing Systems Engineering, Xi' an Jiaotong University, Xi' an 710049, Shaanxi (China); Wang, Yushu [School of Materials Science and Engineering, Georgia Institute of Technology, 500 Tenth Street NW, Atlanta, Georgia 30318 (United States)

    2015-10-21

    Azobenzene dyes have large refractive index near their main resonance, but the poor figure of merit (FOM) limits their potential for all-optical applications. To improve this situation, disperse red 1 (DR1) molecules were dispersed in a sol-gel germanium/Ormosil organic-inorganic hybrid matrix. Z-scan measurement results showed a good compatibility between the dopant and the matrix, and also, an improved FOM was obtained as compared to the DR1/polymer films reported previously. To demonstrate the all-optical signal processing effect, a cw Nd:YAG laser emitting at 532 nm and a He-Ne laser emitting at 632.8 nm were used as pump and probe beams, respectively. DR1 acts as an initiator of the photo-induced transient holographic grating, which is attributed to the trans-cis-trans photoisomerization. Thus, a three inputs AND all-optical logic gate was achieved by using choppers with different frequencies. The detailed mechanism of operation is discussed. These results indicate that the DR1 doped germanium/Ormosil organic-inorganic hybrid film with an improved FOM has a great potential in all-optical devices around its main resonance.

  9. The effect of cores and coating dispersion composition on the mechanical and adhesion properties of hydroxypropyl methylcellulose films.

    Science.gov (United States)

    Banovec, M; Planinsek, O; Vrecer, F

    2014-08-01

    The influence of different additives on the mechanical properties of hydroxypropyl methylcellulose (HPMC) free films was studied using tensile testing. Free films were prepared using the cast method and sliced into bands, and their tensile strength and maximal elongation at break was measured. The results showed that the addition of PEG 400 and polysorbate 80 into the coating formulation had the most influence on the films' mechanical properties compared to the HPMC film used as a control. Tablet cores composed of microcrystalline cellulose and lactose with and without Mg stearate and compressed at three different compression forces were tested for wettability with coating formulations containing PEG 400 and polysorbate 80. For formulations with no Mg stearate added, the contact angle decreased with increasing core hardness and it also coincided with greater adhesion force of the coating. The addition of Mg stearate in the core led to reduced adhesion of the film coating with PEG 400, whereas the influence on the adhesion force of the film coating containing polysorbate 80 was negligible. The results also show that the adhesion force, regardless of the tablet core formulation, is highest at medium core hardness.

  10. Crystal structure and composition of BAlN thin films: Effect of boron concentration in the gas flow

    Science.gov (United States)

    Wang, Shuo; Li, Xiaohang; Fischer, Alec M.; Detchprohm, Theeradetch; Dupuis, Russell D.; Ponce, Fernando A.

    2017-10-01

    We have investigated the microstructure of BxAl1-xN films grown by flow-modulated epitaxy at 1010 °C, with B/(B + Al) gas-flow ratios ranging from 0.06 to 0.18. The boron content obtained from X-ray diffraction (XRD) patterns ranges from x = 0.02 to 0.09. On the other hand, boron content deduced from the aluminum signal in the Rutherford backscattering spectra (RBS) ranges from x = 0.06 to 0.16, closely following the gas-flow ratios. Transmission electron microscopy indicates the sole presence of a wurtzite crystal structure in the BAlN films, and a tendency towards columnar growth for B/(B + Al) gas-flow ratios below 0.12. For higher ratios, the BAlN films exhibit a tendency towards twin formation and finer microstructure. Electron energy loss spectroscopy has been used to profile spatial variations in the composition of the films. The RBS data suggest that the incorporation of B is highly efficient for our growth method, while the XRD data indicate that the epitaxial growth may be limited by a solubility limit in the crystal phase at about 9%, for the range of B/(B + Al) gas-flow ratios that we have studied, which is significantly higher than previously thought.

  11. Crystal structure and composition of BAlN thin films: Effect of boron concentration in the gas flow

    KAUST Repository

    Wang, Shuo

    2017-07-20

    We have investigated the microstructure of BxAl1-xN films grown by flow-modulated epitaxy at 1010 oC, with B/(B+Al) gas-flow ratios ranging from 0.06 to 0.18. The boron content obtained from X-ray diffraction (XRD) patterns ranges from x = 0.02 to 0.09. On the other hand, boron content deduced from the aluminum signal in the Rutherford backscattering spectra (RBS) ranges x = 0.06 to 0.16, closely following gas-flow ratios. Transmission electron microscopy indicates the sole presence of wurtzite crystal structure in the BAlN films, and a tendency towards columnar growth for B/(B+Al) gas-flow ratios below 0.12. For higher ratios, the BAlN films exhibit a tendency towards twin formation and finer microstructure. Electron energy loss spectroscopy has been used to profile spatial variations in the composition of the films.The RBS data suggest that the incorporation of B is highly efficient for our growth method, while the XRD data indicate that the epitaxial growth may be limited by a solubility limit in the crystal phase at about 9%, for the range of B/(B+Al) gas-flow ratios that we used, which is significantly higher than previously thought.

  12. A pancake droplet translating in a Hele-Shaw cell: lubrication film and flow field

    CERN Document Server

    Zhu, Lailai

    2016-01-01

    We adopt a boundary integral method to study the dynamics of a translating droplet confined in a Hele-Shaw cell in the Stokes regime. The droplet is driven by an ambient fluid with the same viscosity. We characterise the three-dimensional (3D) nature of the droplet interface and of the flow field. The interface develops an arc-shaped ridge near the rear-half rim with a protrusion in the rear and a laterally symmetric pair of higher peaks; this pair of protrusions has been identified by the recent experiments (Huerre et al. 2015) and predicted asymptotically (Burgess & Foster 1990). The mean film thickness is well predicted by the extended Bretherton model (Klaseboer et al. 2014) with fitting parameters. The flow in the streamwise wall-normal middle plane is featured with recirculating zones, which are partitioned by stagnation points closely resembling those of a two-dimensional droplet in a channel. Recirculation is absent in the wall-parallel, unconfined, planes, in sharp contrast to the interior flow i...

  13. Bridging amount of spin-glasses over ferromagnetic/antiferromagnetic thin films and bit-cell dispersion of exchange bias in corresponding TA-MRAM devices

    Science.gov (United States)

    Akmaldinov, Kamil; Ducruet, Clarisse; Alvarez-Herault, Jeremy; Baltz, Vincent

    2015-03-01

    For thermally-assisted magnetic random access memories (TA-MRAM), lowering bit-cells dispersions of exchange bias is necessary. In this study, we prove that spin-glass-like phases (SG) spread over the ferromagnetic/antiferromagnetic (F/AF) storage layer are the main cause of such distributions once the film is nanofabricated into a device. In particular, we show that the less the SG, the lower the bit-cell dispersion. More precisely, the amount of SG was varied from sample to sample by sputtering various AFs: IrMn, FeMn and their alloys. Blocking temperature distributions were measured to quantify the amount of SG at the wafer level. The wafers were then patterned to obtain 1kb devices and all the cells were tested electrically. Finally, the resulting loop shift cumulative distribution functions accounting for the bit-cell dispersions were correlated to the initial amount of SG. In addition to bridging the gap between fundamental SG and a technological application, we also demonstrated that blocking temperature distributions are a versatile method to qualify TA-MRAM production batches before processing. Univ. Grenoble-Alpes/CNRS/INAC-CEA, 38000 Grenoble, France.

  14. Flux pinning effects of Y{sub 2}O{sub 3} nanoparticulate dispersions in multilayered YBCO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, T.A. [Air Force Research Laboratory, Propulsion Directorate, AFRL/PRPG, 1950 Fifth Street, Building 450, Wright-Patterson AFB, OH 45433 (United States); Haugan, T.J. [Air Force Research Laboratory, Propulsion Directorate, AFRL/PRPG, 1950 Fifth Street, Building 450, Wright-Patterson AFB, OH 45433 (United States); Maartense, I. [University of Dayton Research Institute, Dayton, OH (United States); Murphy, J. [University of Dayton Research Institute, Dayton, OH (United States); Brunke, L. [University of Dayton Research Institute, Dayton, OH (United States); Barnes, P.N. [Air Force Research Laboratory, Propulsion Directorate, AFRL/PRPG, 1950 Fifth Street, Building 450, Wright-Patterson AFB, OH 45433 (United States)]. E-mail: paul.barnes@wpafb.af.mil

    2005-06-15

    The flux pinning effects of Y{sub 2}O{sub 3} nanoparticulate inclusions in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (Y123 or YBCO) thin films using (Y{sub 2}O{sub 3}/Y123) x N multilayer structures were studied. The multilayer films were made with pulsed laser deposition (PLD) on SrTiO{sub 3} and LaAlO{sub 3} substrates with a Y{sub 2}O{sub 3} nanoparticulate 'pseudo-layer' thickness ranging from 0.2 to 1.4 nm, and YBCO layer thickness varying from 7 to 50 nm. Scanning electron microscopy images showed well-defined nanoparticle formation on film surfaces, with an approximate number density of (0.8-1.6) x 10{sup 11} particles/cm{sup 2} depending on Y{sub 2}O{sub 3} thickness. Minor reductions in the critical temperature (T {sub c}) were measured for each increase in Y{sub 2}O{sub 3} pseudo-layer thickness. Transport critical currents (77 K, self-field) of 3-5 MA/cm{sup 2} were consistently achieved for composite films with 0.6 nm Y{sub 2}O{sub 3} pseudo-layer thicknesses. Magnetic J {sub c} measurements using vibrating sample magnetometry (H 9 T, at 70 and 77 K) showed a degradation of film properties for Y{sub 2}O{sub 3} pseudo-layer thickness greater than 0.6 nm. A comparison to Y211/Y123 multilayer films showed the thinner Y{sub 2}O{sub 3} pseudo-layer films exhibited similar properties.

  15. Effect of substrate temperature on the structure of amorphous oxygenated hydrocarbon films grown with a pulsed supersonic methane plasma flow

    Energy Technology Data Exchange (ETDEWEB)

    Fedoseeva, Yu. V., E-mail: fedoseeva@niic.nsc.ru [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Pozdnyakov, G.A. [Khristianovich Institute of Theoretical and Applied Mechanics, SB RAS, Novosibirsk 630090 (Russian Federation); Okotrub, A.V.; Kanygin, M.A. [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Nastaushev, Yu. V. [Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk 630090 (Russian Federation); Vilkov, O.Y. [St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Bulusheva, L.G. [Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation)

    2016-11-01

    Highlights: • A deposition of supersonic methane plasma flow on silicon substrate produces amorphous oxygenated hydrocarbon (CO{sub x}H{sub y}) film. • The thickness, composition, and wettability of the film depend on the substrate temperature. • A rise of the substrate temperature from 500 to 700 °C promotes the sp{sup 3}-hybridization carbon formation. - Abstract: Since amorphous oxygenated hydrocarbon (CO{sub x}H{sub y}) films are promising engineering materials a study of the structure and composition of the films depending on the conditions of synthesis is important for controlling of their physicochemical properties. Here, we used the methods of scanning and transmission electron microscopy, X-ray photoelectron, near-edge X-ray absorption fine structure, Fourier transform infrared and Raman spectroscopy to reveal changes in the chemical connectivity of CO{sub x}H{sub y} films grown on silicon substrates heated to 300, 500, and 700 °C using a supersonic flow of methane plasma. It was found that the CO{sub x}H{sub y} films, deposited at 300 and 500 °C, were mainly composed of the sp{sup 2}-hybridized carbon areas with various oxygen species. A rise of the substrate temperature caused an increase of the portion of tetrahedral carbon atoms as well as carboxyl and hydroxyl groups. With growth of the substrate temperature, the film thickness reduced monotonically from 400 to 180 nm, while the film adhesion improved substantially. The films, deposited at lower temperatures, showed high hydrophilicity due to porosity and presence of oxygenated groups both at the surface and in the bulk.

  16. SIMULATION OF THE TWO PHASE FLOW OF DROPLET IMPINGEMENT ON LIQUID FILM BY THE LATTICE BOLTZMANN METHOD

    Institute of Scientific and Technical Information of China (English)

    GUO Jia-hong; WANG Xiao-yong

    2012-01-01

    A Lattice Boltzmann Method (LBM) with two-distribution functions is employed for simulating the two-phase flow induced by a liquid droplet impinging onto the film of the same liquid on solid surface.The model is suitable for solution of twophase flow problem at high density and viscosity ratios of liquid to vapor and phase transition between liquid and its vapor.The roles of the vapor flow,the density ratio of liquid to vapor and the surface tension of the droplet in the splashing formation are discussed.It is concluded that the vapour flow induced by the droplet fall and splash in the whole impinging process may affect remarkably the splash behaviour.For the case of large density ratio of liquid to vapor a crown may engender after the droplet collides with the film.However,for the case of small density ratio of liquid to vapor a “bell” like splash may be observed.

  17. The flow across a street canyon of variable width—Part 2:. Scalar dispersion from a street level line source

    Science.gov (United States)

    Simoëns, Serge; Wallace, James M.

    As described in Part 1 [Simoëns et al., 2007. The flow across a street canyon of variable width—Part 1: kinematic description. Atmospheric Environment 41, 9002-9017] measurements have been made of the velocity field around and within the canyon formed by two obstacles placed on the wall of a turbulent boundary layer. Here in Part 2 measurements of the scalar dispersion of smoke released from a two-dimensional slot in the wall perpendicular to the mean flow and located parallel to and midway between these two square obstacles are presented. The Reynolds number of the boundary layer at the slot location without the obstacles in place was Rθ≈980. Statistical properties of the concentration field and the scalar fluxes in the streamwise plane are reported here for canyon openings that have been chosen based on characteristics of the kinematic description. These opening widths, expressed as multiples of the obstacle height, are 1 h, 4 h and 8 h. The mean concentration field revealed that the much of the scalar is trapped on the leeward side of the upstream obstacle before some of it escapes the canyon and is entrained on the roof of the upstream obstacle. It then is spread downstream by the turbulence in the wake of this obstacle. Surprisingly, the root mean square (rms) concentration field reveals that high concentration fluctuations exist in a zone where velocity field turbulence is very low. Measured streamwise scalar fluxes were found to be negative above the obstacles, whereas they are mainly positive between the obstacles. The measured wall normal scalar fluxes have an inverse behavior. Within the canyon, the scalar fluxes are greatest in the region between the large primary vortex, evident in the kinematic field, and the secondary vortex located in the corner of the leeward side of the upstream obstacle. In the flow above the obstacle roofs the wake of the upstream obstacle seems to dominate the scalar transport. Between the obstacles in and above the canyon

  18. 聚合物分散液晶膜的压光效应%Piezo-Optical Effect of Polymer Dispersed Liquid Crystal Films

    Institute of Scientific and Technical Information of China (English)

    范志新; 解一军; 魏向东; 解会杰; 宋新华; 王丹; 孙玉宝

    2011-01-01

    报道了一种聚合物分散液晶(PDLC)膜在压力作用下从散射膜变为透明膜的实验现象,建议称之为PDLC膜的压光效应.介绍了与压光效应相关的PDLC的应变液晶、剪切液晶和拉伸液晶等概念;给出PDLC压光效应膜样品照片,偏光显微镜照片,电光特性光谱分析和压光效应光谱分析.提出PDLC膜压光效应的原理猜想,给出对PDLC膜光学性质的重新认识,认为只要每个液晶微滴中液晶分子取向一致了,无论不同微滴间液晶分子取向一致与否,PDLC膜都将透明.PDLC膜压光效应将对液晶基础科学提出新课题,将在许多不用加电的新型压光器件(按压窗、功能玻璃和光纤压力传感器等)领域有应用前景.%It is reported that polymer dispersed liquid crystal (PDLC) films are transparency when pressed, and it is called piezo-optical effect of PDLC films. The concepts of stressed liquid crystal, sheared liquid crystal and stretched liquid crystal for PDLC films are described respectively. The pictures of piezo-optical effect, polarized photographs of PDLC films, spectral analysis of electro-optical property and spectral analysis of piezo-optical effect are given. The principle of piezo-optical effect of PDLC films is also proposed, which believes that only if liquid crystal molecules in each micro-droplet are well orientated, the PDLC films will show transparency, no matter liquid crystal molecules in different droplets are well orientated or not. The piezo-optical effect of PDLC films poses questions to basic sciences of liquid crystal and may be applied in a lot of new press-optical applications without electricity (press-windows,functional glass, optical fiber press sensor, etc. ).

  19. Film formation from aqueous polyurethane dispersions of reactive hydrophobic and hydrophilic components; spectroscopic studies and Monte Carlo simulations.

    Science.gov (United States)

    Otts, Daniel B; Cueva-Parra, Luis A; Pandey, Ras B; Urban, Marek W

    2005-04-26

    Film formation of waterborne two-component polyurethanes is exceedingly complex due to the heterogeneous nature along with simultaneous progression of several parallel physicochemical processes which include water evaporation, cross-linking reactions, phase separation, and droplet coalescence, to name a few. While internal reflection infrared imaging (IRIRI) spectroscopy clearly facilitates analysis of chemical changes resulting from film formation, the complexity of processes leading to formation of specific surface/interfacial entities is a major experimental challenge. For this reason, we combined a spectrum of surface/interfacial analytical approaches including IRIRI, atomic force microscopy, and attenuated total reflectance Fourier transform infrared spectroscopy with Monte Carlo computer simulations to advance the limited knowledge of how temperature, stoichiometry, concentration levels, and reactivities of individual components affect the development of surface morphologies and compositional gradients across the film thickness. These studies show that in heterogeneous systems having both hydrophobic and hydrophilic components stratification of individual components to the film-air (F-A) interface is ultimately responsible for formation of rough surface topographies. These studies show that simultaneous stratification of hydrophobic components along with water evaporation to the F-A interface results in metastable interfacial layers, leading to surface dewetting. Subsequently, surface roughness is enhanced by higher concentrations of water in the cross-linking film.

  20. MHD Thin Film Flows of a Third Grade Fluid on a Vertical Belt with Slip Boundary Conditions

    OpenAIRE

    Taza Gul; Rehan Ali Shah; Saeed Islam; Muhammad Arif

    2013-01-01

    The problem of heat transfer analysis is considered in electrically conducting thin film flows with slip boundary conditions. The flow is assumed to be obeying the nonlinear rheological constitutive equation of a third grade fluid. We have solved the governing nonlinear equations of present problems using the traditional Adomian decomposition method (ADM). Particular attention is given to the combined effect of heat and MHD on the velocity field. The results include the profile of velocity, v...

  1. Effects of oxygen flow rate on the electrical stability of zinc oxynitride thin-film transistors

    Science.gov (United States)

    Kim, Dae-Hwan; Jeong, Hwan-Seok; Jeong, Chan-Yong; Song, Sang-Hun; Kwon, Hyuck-In

    2017-02-01

    We investigated the effects of the oxygen flow rate (OFR) during the deposition of a zinc oxynitride (ZnON) channel layer on the electrical performance and stability of high-mobility ZnON thin-film transistors (TFTs). The ZnON TFTs prepared at a lower OFR exhibited higher electrical performance characteristics and a higher electrical stability under positive gate bias stresses than those prepared at a higher OFR, but showed a lower electrical stability under negative gate bias stresses. The lower density of subgap states within the channel layer and the higher hole concentration due to the small bandgap were considered as physical mechanisms responsible for the observed phenomena, respectively.

  2. An investigation of an Emden-Fowler equation from thin film flow

    Science.gov (United States)

    Momoniat, Ebrahim

    2012-04-01

    A third-order ordinary differential equation (ODE) for thin film flow with both Neumann and Dirichlet boundary conditions is transformed into a second-order nonlinear ODE with Dirichlet boundary conditions. Numerical solutions of the nonlinear second-order ODE are investigated using finite difference schemes. A finite difference formulation to an Emden-Fowler representation of the second-order nonlinear ODE is shown to converge faster than a finite difference formulation of the standard form of the second-order nonlinear ODE. Both finite difference schemes satisfy the von Neumann stability criteria. When mapping the numerical solution of the second-order ODE back to the variables of the original third-order ODE we recover the position of the contact line. A nonlinear relationship between the position of the contact line and physical parameters is obtained.

  3. A dynamical systems' approach for the contact-line singularity in thin-film flows

    CERN Document Server

    Belgacem, Fethi Ben; Kuehn, Christian

    2016-01-01

    We are interested in a complete characterization of the contact-line singularity of thin-film flows for zero and nonzero contact angles. By treating the model problem of source-type self-similar solutions, we demonstrate that this singularity can be understood by the study of invariant manifolds of a suitable dynamical system. In particular, we prove regularity results for singular expansions near the contact line for a wide class of mobility exponents and for zero and nonzero dynamic contact angles. Key points are the reduction to center manifolds and identifying resonance conditions at equilibrium points. The results are extended to radially-symmetric source-type solutions in higher dimensions. Furthermore, we give dynamical systems' proofs for the existence and uniqueness of self-similar droplet solutions in the nonzero dynamic contact-angle case.

  4. An investigation of an Emden-Fowler equation from thin film flow

    Institute of Scientific and Technical Information of China (English)

    Ebrahim Momoniat

    2012-01-01

    A third-order ordinary differential equation (ODE)for thin film flow with both Neumann and Dirichlet boundary conditions is transformed into a second-order nonlinear ODE with Dirichlet boundary conditions.Numerical solutions of the nonlinear second-order ODE are investigated using finite difference schemes.A finite difference formulation to an Emden-Fowler representation of the second-order nonlinear ODE is shown to converge faster than a finite difference formulation of the standard form of the second-order nonlinear ODE.Both finite difference schemes satisfy the yon Neumann stability criteria.When mapping the numerical solution of the second-order ODE back to the variables of the original third-order ODE we recover the position of the contact line.A nonlinear relationship between the position of the contact line and physical parameters is obtained.

  5. Pinning effects on hot-electron vortex flow instability in superconducting films

    Science.gov (United States)

    Shklovskij, Valerij A.

    2017-07-01

    The hot-electron vortex flow instability in superconducting films in magnetic field B at substrate temperature T0 ≪ Tc is theoretically considered in the presence of pinning. The magnetic field dependences of the instability critical parameters (electric field E*, current density j*, resistivity ρ*, power density P* and vortex velocity v*) are derived for a cosine and a saw-tooth washboard pinning potential and compared with the results obtained earlier by M. Kunchur [Phys. Rev. Lett. 89 (2002) 137005] in absence of pinning. It is shown that the B-behavior of E*, j* and ρ* is monotonic, whereas the B-dependence of v* is quite different, namely dv*/dB may change its sign twice, as sometimes observed in experiments. The simplest heat balance equation for electrons in low-Tc superconducting films is considered within the framework of the two-fluid model. A theoretical analysis reveals that the instability critical temperature T* ≈ 5Tc/6 at T0 < T*/2 with T* being independent of B.

  6. Laminar film condensation from downward flowing superheated vapors onto a non-isothermal sphere

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, C.H. [Dept. of Mold and Die Engineering, National Kaohsiung Univ. of Applied Sciences, Kaohsiung (Taiwan)

    2001-11-01

    A model is developed for the study of mixed convection film condensation from downward flowing superheated vapors onto a sphere with variable wall temperature. The model combined natural convection dominated and forced convection dominated film condensation, including effects of superheated vapor, pressure gradient and wall temperature variation can be solved numerically by the fourth-order Runge-Kutta technique. By the present numerical approach, the mean heat transfer is evaluated up to the critical angle of the condensate layer, {phi}{sub c}. In general, the result of mean heat transfer shows that, as A, the wall-temperature amplitude, increases, the value of NuRe{sup -1/2} with inclusion of P, the pressure gradient effect, goes down slightly, however, the value of NuRe{sup -1/2} with the pressure gradient effect ignored will remain almost uniform. Further, for P=2.0, the mean heat transfer coefficient increases significantly, by 8.6-23.9%, depending on A, as the superheat parameter, Sp, increases within a practical range. (orig.)

  7. Stability of viscous film flow coating the interior of a vertical tube with a porous wall

    Science.gov (United States)

    Liu, Rong; Ding, Zijing

    2017-05-01

    The stability of the gravity-driven flow of a viscous film coating the inside of a tube with a porous wall is studied theoretically. We used Darcy's law to describe the motion of fluids in a porous medium. The Beaver-Joseph condition is used to describe the discontinuity of velocity at the porous-fluid interface. We derived an evolution equation for the film thickness using a long-wave approximation. The effect of velocity slip at the porous wall is identified by a parameter β . We examine the effect of β on the temporal stability, the absolute-convective instability (AI-CI), and the nonlinear evolution of the interface deformation. The results of the temporal stability reveal that the effect of velocity slip at the porous wall is destabilizing. The parameter β plays an important role in determining the AI-CI behavior and the nonlinear evolution of the interface. The presence of the porous wall promotes the absolute instability and the formation of the plug in the tube.

  8. The effect of holes in the dispersion relation of propagative surface plasmon modes of nanoperforated semitransparent metallic films

    Energy Technology Data Exchange (ETDEWEB)

    Kekesi, R., E-mail: renata.kekesi@csic.es; Meneses-Rodríguez, D.; García-Pérez, F.; González, M. U.; García-Martín, A.; Cebollada, A.; Armelles, G., E-mail: gaspar@imm.cnm.csic.es [IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, PTM, E-28760 Tres Cantos, Madrid (Spain)

    2014-10-07

    We have analysed the effect that holes have on the properties of propagative surface plasmon modes in semitransparent nanoperforated Au films. The modes have been excited in Kretschmann configuration. Contrary to continuous films, where only one mode is excited, two modes are observed in Au nanohole array. The origin of this different behavior is discussed using effective optical properties for the nanoperforated films. The presence of the holes affects the effective optical constants of the membranes in two ways: it changes the contribution of the free electrons, and it gives rise to a localized transition due to a hole induced plasmon resonance. This localized transition interacts with the propagative surface plasmon modes, originating the two detected modes.

  9. Thin power law film flow down an inclined plane: consistent shallow water models and stability under large scale perturbations

    CERN Document Server

    Noble, Pascal

    2012-01-01

    In this paper we derive consistent shallow water equations for thin films of power law fluids down an incline. These models account for the streamwise diffusion of momentum which is important to describe accurately the full dynamic of the thin film flows when instabilities like roll-waves arise. These models are validated through a comparison with Orr Sommerfeld equations for large scale perturbations. We only consider laminar flow for which the boundary layer issued from the interaction of the flow with the bottom surface has an influence all over the transverse direction to the flow. In this case the concept itself of thin film and its relation with long wave asymptotic leads naturally to flow conditions around a uniform free surface Poiseuille flow. The apparent viscosity diverges at the free surface which, in turn, introduces a singularity in the formulation of the Orr-Sommerfeld equations and in the derivation of shallow water models. We remove this singularity by introducing a weaker formulation of Cauc...

  10. Investigations of spherical Cu NPs in sodium lauryl sulphate with Tb{sup 3+} ions dispersed in PVA films

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Brijesh; Kaur, Gagandeep, E-mail: gagandeep_bhu@yahoo.com; Rai, S.B., E-mail: sbrai49@yahoo.co.in

    2016-03-15

    Highlights: • Cu NPs were prepared in SDS using 1064 nm laser radiation at fluence 37, 64 and 88 J/cm{sup 2}. • Spherical Cu NPs with average diameter varying between 10 and 50 nm atdifferent fluence. • PL of Tb3+ ions in PVA polymer film is maximum with Cu NPS at fluence 37 J/cm{sup 2}. • PVA films of Cu NPs displayed a highly temperature-dependent electrical conductivity. • These copper NPs embedded PVA films can be used as novel, low-cost sensor materials. - Abstract: Cu nanoparticles (NPs) have been prepared in SDS solution using 1064 nm laser radiation at different fluence 37 J/cm{sup 2}, 64 J/cm{sup 2} and 88 J/cm{sup 2} and structurally characterized. The TEM measurements reveal the presence of nanoparticles of spherical shape with different size. The size of the nanoparticles and their concentration increases with the increase of fluence.The effect of these Cu nanoparticles on the emissive properties of Tb{sup 3+} ion in polymer films has been studied. It is found that emission intensity of Tb{sup 3+} first increases and then deceases both with concentration of Cu NPs as well as with sizes. The PL intensity of Tb{sup 3+} ions is minimum for Cu NPs prepared with highest fluence. It has been explained in term of local field effect. This was also verified by life time measurements. These thin PVA films of copper nanoparticles displayed a highly temperature-dependent electrical conductivity with sensitivity at least comparable to commercial materials which suggest the use of these copper NPs embedded PVA films as novel, low-cost sensor materials.

  11. A micromachined thin-film gas flow sensor for microchemical reactors

    Science.gov (United States)

    Shin, W. C.; Besser, R. S.

    2006-04-01

    As microchemical systems (MCS) have gained in importance since their introduction in the last decade, it has become recognized that appropriate sensing and control capabilities are needed if MCS are to reach their potential. In this context, we present a study of the working behavior of a novel thin-film micro flow sensor which is integrated with a silicon microreactor with a submillimeter channel. A simple-to-fabricate device based on the concept of calorimetric sensing was chosen as a model structure to understand the important factors controlling sensor performance. Various design options for the sensor were explored by the use of computational fluid dynamics simulations. We found that sensitivity depends strongly on certain design factors. In summary, sensitivity is improved with (a) higher values of the resistors that detect flow-induced temperature changes, (b) shorter distances between the resistor that provides a source of heat and the thermally sensitive resistors and (c) higher input power to the heating resistor. Item (a) was found to have by far the strongest effect of the three. Reproducibility tests were conducted and the sensor exhibited consistent performance throughout the entire test range of 0-20 sccm which is an appropriate fit to the flow capacity of the microchannel. Finally, response time was assessed by simulating the transient behavior of the sensor with a thermal capacitance model, which yielded an accurate prediction of the experimental response of the device. The response time is approximately 70 ms at a typical flow rate of 10 sccm. According to the understanding gained from the model, the sensor response time can be improved by reducing the substrate thickness, using a lower density substrate material, and increasing the convective heat transfer coefficient in the channel.

  12. Composition variations in Cu{sub 2}ZnSnSe{sub 4} thin films analyzed by X-ray diffraction, energy dispersive X-ray spectroscopy, particle induced X-ray emission, photoluminescence, and Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Dahyun [Department of Physics, Sogang University, Seoul 121-742 (Korea, Republic of); Opanasyuk, A.S.; Koval, P.V.; Ponomarev, A.G. [Department of Electronics and Computer Technology, Sumy State University, Sumy UA-40007 (Ukraine); Jeong, Ah Reum; Kim, Gee Yeong; Jo, William [Department of Physics, Ewha Womans University, Seoul 120-750 (Korea, Republic of); Cheong, Hyeonsik, E-mail: hcheong@sogang.ac.kr [Department of Physics, Sogang University, Seoul 121-742 (Korea, Republic of)

    2014-07-01

    Compositional and structural studies of Cu{sub 2}ZnSnSe{sub 4} (CZTSe) thin films were carried out by X-ray diffraction, energy dispersive X-ray spectroscopy (EDS), particle induced X-ray emission (PIXE), photoluminescence, and Raman spectroscopy. CZTSe thin films with different compositions were deposited on sodalime glass by co-evaporation. The composition of the films measured by two different methods, EDS and PIXE, showed significant differences. Generally, the Zn/Sn ratio measured by EDS is larger than that measured by PIXE. Both the micro-PIXE and the micro-Raman imaging results indicated the compositional and structural inhomogeneity of the sample. - Highlights: • Particle induced X-ray emission was used to analyze the composition of CZTSe films. • Energy dispersive X-ray spectroscopy tends to underestimate the Sn composition. • Local Raman intensity is related with the composition rather than the crystallinity.

  13. 溶胶-凝胶法制备金属铂高分散的二氧化钛薄膜%Preparation of Titania Thin Film with Highly-Dispersed Platinum Metal by Sol-Gel Method

    Institute of Scientific and Technical Information of China (English)

    黄妙良; 伴隆幸; 大矢丰; 高桥康隆

    2001-01-01

    Uniform and crack-free TiO2 thin films with highly-dispersed platinum were p repared from i-PrOH-TTIP-DEA-H2O system containing H2PtCl6*6H 2O as metal source by sol-gel method. The microstructure and morphology of th e films were characterized by TEM and XRD respectively. It was found that the Pt particles dispersed in the films and had a homogeneous distribution in the shap e of sphere with an average size of about 5 nm. This study also showed that the doping with few percent of Pt resulted in the formation of pure rutile phase at a temperature as low as 550 ℃, whereas the same pure phase was formed at the te mperature higher than 650 ℃ in TiO2 or Au/TiO2 thin films.

  14. Influence of long-distance seed dispersal on the genetic diversity of seed rain in fragmented Pinus densiflora populations relative to pollen-mediated gene flow.

    Science.gov (United States)

    Ozawa, Hajime; Watanabe, Atsushi; Uchiyama, Kentaro; Saito, Yoko; Ide, Yuji

    2013-01-01

    Long-distance dispersal (LDD) of seeds has a critical impact on species survival in patchy landscapes. However, relative to pollen dispersal, empirical data on how seed LDD affects genetic diversity in fragmented populations have been poorly reported. Thus, we attempted to indirectly evaluate the influence of seed LDD by estimating maternal and paternal inbreeding in the seed rain of fragmented 8 Pinus densiflora populations. In total, the sample size was 458 seeds and 306 adult trees. Inbreeding was estimated by common parentage analysis to evaluate gene flow within populations and by sibship reconstruction analysis to estimate gene flow within and among populations. In the parentage analysis, the observed probability that sampled seeds had the same parents within populations was significantly larger than the expected probability in many populations. This result suggested that gene dispersal was limited to within populations. In the sibship reconstruction, many donors both within and among populations appeared to contribute to sampled seeds. Significant differences in sibling ratios were not detected between paternity and maternity. These results suggested that seed-mediated gene flow and pollen-mediated gene flow from outside population contributed some extent to high genetic diversity of the seed rain (H E > 0.854). We emphasize that pine seeds may have excellent potential for gene exchange within and among populations.

  15. Deduction and Validation of an Eulerian-Eulerian Model for Turbulent Dilute Two-Phase Flows by Means of the Phase Indicator Function Disperse Elements Probability Density Function

    Institute of Scientific and Technical Information of China (English)

    SantiagoLain; RicardoAliod

    2000-01-01

    A statistical formalism overcoming some conceptual and practical difficulties arising in existing two-phase flow (2PHF) mathematical