WorldWideScience

Sample records for laminar separation caused

  1. Aerodynamics and Percolation: Unfolding Laminar Separation Bubble on Airfoils

    Science.gov (United States)

    Traphan, Dominik; Wester, Tom T. B.; Gülker, Gerd; Peinke, Joachim; Lind, Pedro G.

    2018-04-01

    As a fundamental phenomenon of fluid mechanics, recent studies suggested laminar-turbulent transition belonging to the universality class of directed percolation. Here, the onset of a laminar separation bubble on an airfoil is analyzed in terms of the directed percolation model using particle image velocimetry data. Our findings indicate a clear significance of percolation models in a general flow situation beyond fundamental ones. We show that our results are robust against fluctuations of the parameter, namely, the threshold of turbulence intensity, that maps velocimetry data into binary cells (turbulent or laminar). In particular, this percolation approach enables the precise determination of the transition point of the laminar separation bubble, an important problem in aerodynamics.

  2. Experimental Study of Unsteady Flow Separation in a Laminar Boundary Layer

    Science.gov (United States)

    Bonacci, Andrew; Lang, Amy; Wahidi, Redha; Santos, Leonardo

    2017-11-01

    Flow separation, caused by an adverse pressure gradient, is a major problem in many applications. Reversing flow near the wall is the first sign of incipient separation and can bristle shark scales which may be linked to a passive, flow actuated separation control mechanism. An investigation of how this backflow forms and how it interacts with shark skin is of interest due to the fact that this could be used as a bioinspired means of initiating flow control. A water tunnel experiment aims to study unsteady separation with a focus on the reversing flow development near the wall within a flat plate laminar boundary layer (Re on order of 105) as an increasing adverse pressure gradient is induced by a rotating cylinder. Unsteady reversing flow development is documented using DPIV. Funding was provided by the National Science Foundation under the Research Experience for Undergraduates (REU) program (EEC 1659710) and the Army Research Office.

  3. Effects of laminar separation bubbles and turbulent separation on airfoil stall

    Energy Technology Data Exchange (ETDEWEB)

    Dini, P. [Carleton College, Northfield, MN (United States); Coiro, D.P. [Universita di Napoli (Italy)

    1997-12-31

    An existing two-dimensional, interactive, stall prediction program is extended by improving its laminar separation bubble model. The program now accounts correctly for the effects of the bubble on airfoil performance characteristics when it forms at the mid-chord and on the leading edge. Furthermore, the model can now predict bubble bursting on very sharp leading edges at high angles of attack. The details of the model are discussed in depth. Comparisons of the predicted stall and post-stall pressure distributions show excellent agreement with experimental measurements for several different airfoils at different Reynolds numbers.

  4. Active flow control of the laminar separation bubble on a plunging airfoil near stall

    Science.gov (United States)

    Pande, Arth; Agate, Mark; Little, Jesse; Fasel, Hermann

    2017-11-01

    The effects of small amplitude (A/c = 0.048) high frequency (πfc/U∞ = 0.70) plunging motion on the X-56A airfoil are examined experimentally at Re = 200,000 for 12° angle of attack (CL,MAX = 12.25°) . The purpose of this research is to study the aerodynamic influence of structural motion when the wing is vibrating close to its eigenfrequency near static stall. Specific focus is placed on the laminar separation bubble (LSB) near the leading edge and its control via plasma actuation. In the baseline case, the leading edge bubble bursts during the oscillation cycle causing moment stall. A collaborative computational effort has shown that small amplitude forcing at a frequency that is most amplified by the primary instability of the LSB (FLSB+= 1, Fc+= 52) generates coherent spanwise vortices that entrain freestream momentum, thus reducing separation all while maintaining a laminar flow state. Results (PIV and surface pressure) indicate that a similar control mechanism is effective in the experiments. This is significant given the existence of freestream turbulence in the wind tunnel which has been shown to limit the efficacy of this active flow control technique in a model problem using Direct Numerical Simulation. The implications of these results are discussed.

  5. Unsteady Characteristics of Laminar Separation Bubbles; An Experimental and Numerical Investigation

    NARCIS (Netherlands)

    Baragona, M.

    2004-01-01

    Laminar separation bubbles may occur in a wide range of engineering applications such as turbomachinery flows, wind turbines, hydrofoils etc. Much attention has been given to their effect on the flow over airfoils because of the importance for an accurate prediction of lift, drag and heat transfer.

  6. Use of laminar chromatographic methods for determination of separation conditions in column extraction chromatography

    International Nuclear Information System (INIS)

    Ghersini, G.; Cerrai, E.

    1978-01-01

    Possibilities of using laminar chromatographic methods (paper and thin-layer chromatography) to determine optimal separation conditions in column extraction chromatography are analysed. Most of the given laminar methods are presented as Rf-spectra, i.e. as dependences of Rf found experimentally on eluating solution component concentration. Interrelation between Rf and distribution coefficients of corresponding liquid extraction systems and retention volumes of chromatographic columns is considered. Literature data on extraction paper and thin-layer chromatography of elements with various immovable phases are presented

  7. Passive Flap Actuation by Reversing Flow in Laminar Boundary Layer Separation

    Science.gov (United States)

    Parsons, Chase; Lang, Amy; Santos, Leo; Bonacci, Andrew

    2017-11-01

    Reducing the flow separation is of great interest in the field of fluid mechanics in order to reduce drag and improve the overall efficiency of aircraft. This project seeks to investigate passive flow control using shark inspired microflaps in laminar boundary layer separation. This study aims to show that whether a flow is laminar or turbulent, laminar and 2D or turbulent and 3D, microflaps actuated by reversing flow is a robust means of controlling flow separation. In order to generate a controlled adverse pressure gradient, a rotating cylinder induces separation at a chosen location on a flat plate boundary layer with Re above 10000. Within this thick boundary layer, digital particle image velocimetry is used to map the flow. This research can be used in the future to better understand the nature of the bristling shark scales and its ability to passively control separation. Results show that microflaps successfully actuated due to backflow and that this altered the formation of flow separation. I would like to thank the NSF for REU Grant EEC 1659710 and the Army Research Office for funding this project.

  8. Spalart–Allmaras model apparent transition and RANS simulations of laminar separation bubbles on airfoils

    International Nuclear Information System (INIS)

    Crivellini, Andrea; D’Alessandro, Valerio

    2014-01-01

    Highlights: • RANS simulation of laminar separation bubbles. • Spalart–Allamaras unexpected capability. • Straightforward implementation of our SA modifications. • Applications of a high order DG incompressible solver. - Abstract: The present paper deals with the Reynolds Averaged Navier–Stokes (RANS) simulation of Laminar Separation Bubble (LSB). This phenomenon is of large interest in several engineering fields, such as the study of wind turbines, unmanned aerial vehicles (UAV) and micro-air vehicles (MAV) characterized by a low operating Reynolds number. In such contexts a laminar boundary layer separation followed by a turbulent transition and afterwards by a turbulent reattachment may appear in the flow-field. The main novelty of this work is that an almost standard Spalart–Allmaras (SA) model, without additional equations for transition modeling, was successfully employed. The result achieved is very surprising being the model not developed for this purpose, but for fully-turbulent flows or for cases with imposed transition location. This result is of large interest, since the SA model is widely used in commercial, open-source and research codes. However, our approach cannot be advocated to predict natural transition within an attached boundary layer, indeed it is only able to deal with transitions triggered by a separated flow. The reliability and accuracy of our approach are here proved computing, by means of a high-order Discontinuous Galerkin (DG) incompressible solver, the flow-field over two airfoils at different flow regimes showing the formation of a LSB

  9. Scanning PIV investigation of the laminar separation bubble on a SD7003 airfoil

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei [Technische Universitaet Braunschweig, Institut fuer Stroemungsmechanik, Braunschweig (Germany); Iowa State University, Department of Aerospace Engineering, Ames, IA (United States); Hain, Rainer [Technische Universitaet Braunschweig, Institut fuer Stroemungsmechanik, Braunschweig (Germany); Institut fuer Aerodynamik und Stroemungstechnik, Deutsches Zentrum fuer Luft- und Raumfahrt e.V. (DLR), Braunschweig (Germany); Kaehler, Christian J. [Technische Universitaet Braunschweig, Institut fuer Stroemungsmechanik, Braunschweig (Germany); Universitaet der Bundeswehr Muenchen, Institut fuer Stroemungsmechanik und Aerodynamik, Neubiberg (Germany)

    2008-10-15

    A laminar separation bubble occurs on the suction side of the SD7003 airfoil at an angle of attack {alpha}=4-8 and a low Reynolds number less than 100,000, which brings about a significant adverse aerodynamic effect. The spatial and temporal structure of the laminar separation bubble was studied using the scanning PIV method at {alpha}=4 and Re=60,000 and 20,000. Of particular interest are the dynamic vortex behavior in transition process and the subsequent vortex evolution in the turbulent boundary layer. The flow was continuously sampled in a stack of parallel illuminated planes from two orthogonal views with a frequency of hundreds Hz, and PIV cross-correlation was performed to obtain the 2D velocity field in each plane. Results of both the single-sliced and the volumetric presentations of the laminar separation bubble reveal vortex shedding in transition near the reattachment region at Re=60,000. In a relatively long distance vortices characterized by paired wall-normal vorticity packets retain their identities in the reattached turbulent boundary layer, though vortices interact through tearing, stretching and tilting. Compared with the restricted LSB at Re=60,000, the flow at Re=20,000 presents an earlier separation and a significantly increased reversed flow region followed by ''huge'' vortical structures. (orig.)

  10. Membraneless laminar flow cell for electrocatalytic CO2 reduction with liquid product separation

    International Nuclear Information System (INIS)

    Monroe, Morgan M; Lobaccaro, Peter; Lum, Yanwei; Ager, Joel W

    2017-01-01

    The production of liquid fuel products via electrochemical reduction of CO 2 is a potential path to produce sustainable fuels. However, to be practical, a separation strategy is required to isolate the fuel-containing electrolyte produced at the cathode from the anode and also prevent the oxidation products (i.e. O 2 ) from reaching the cathode. Ion-conducting membranes have been applied in CO 2 reduction reactors to achieve this separation, but they represent an efficiency loss and can be permeable to some product species. An alternative membraneless approach is developed here to maintain product separation through the use of a laminar flow cell. Computational modelling shows that near-unity separation efficiencies are possible at current densities achievable now with metal cathodes via optimization of the spacing between the electrodes and the electrolyte flow rate. Laminar flow reactor prototypes were fabricated with a range of channel widths by 3D printing. CO 2 reduction to formic acid on Sn electrodes was used as the liquid product forming reaction, and the separation efficiency for the dissolved product was evaluated with high performance liquid chromatography. Trends in product separation efficiency with channel width and flow rate were in qualitative agreement with the model, but the separation efficiency was lower, with a maximum value of 90% achieved. (paper)

  11. Unsteady separation and vortex shedding from a laminar separation bubble over a bluff body

    Science.gov (United States)

    Das, S. P.; Srinivasan, U.; Arakeri, J. H.

    2013-07-01

    Boundary layers are subject to favorable and adverse pressure gradients because of both the temporal and spatial components of the pressure gradient. The adverse pressure gradient may cause the flow to separate. In a closed loop unsteady tunnel we have studied the initiation of separation in unsteady flow past a constriction (bluff body) in a channel. We have proposed two important scalings for the time when boundary layer separates. One is based on the local pressure gradient and the other is a convective time scale based on boundary layer parameters. The flow visualization using a dye injection technique shows the flow structure past the body. Nondimensional shedding frequency (Strouhal number) is calculated based on boundary layer and momentum thicknesses. Strouhal number based on the momentum thickness shows a close agreement with that for flat plate and circular cylinder.

  12. Investigation of unsteady, hypersonic, laminar separated flows over a double cone geometry using a kinetic approach

    Science.gov (United States)

    Tumuklu, Ozgur; Levin, Deborah A.; Theofilis, Vassilis

    2018-04-01

    Shock-dominated hypersonic laminar flows over a double cone are investigated using time accurate direct simulation Monte Carlo combined with the residuals algorithm for unit Reynolds numbers gradually increasing from 9.35 × 104 to 3.74 × 105 m-1 at a Mach number of about 16. The main flow features, such as the strong bow-shock, location of the separation shock, the triple point, and the entire laminar separated region, show a time-dependent behavior. Although the separation shock angle is found to be similar for all Re numbers, the effects of Reynolds number on the structure and extent of the separation region are profound. As the Reynolds number is increased, larger pressure values in the under-expanded jet region due to strong shock interactions form more prominent λ-shocklets in the supersonic region between two contact surfaces. Likewise, the surface parameters, especially on the second cone surface, show a strong dependence on the Reynolds number, with skin friction, pressure, and surface heating rates increasing and velocity slip and temperature jump values decreasing for increasing Re number. A Kelvin-Helmholtz instability arising at the shear layer results in an unsteady flow for the highest Reynolds number. These findings suggest that consideration of experimental measurement times is important when it comes to determining the steady state surface parameters even for a relatively simple double cone geometry at moderately large Reynolds numbers.

  13. The effects of tonal and broadband acoustic excitation on the transition process within a laminar separation bubble

    Science.gov (United States)

    Yarusevych, Serhiy; Kurelek, John; Kotsonis, Marios

    2017-11-01

    The effects of controlled acoustic excitation on the transition process in a laminar separation bubble formed on the suction side of a NACA 0018 airfoil at a chord Reynolds number of 125,000 and an angle of attack of 4 degrees are studied experimentally. The investigation is carried out using time-resolved, planar, two-component Particle Image Velocimetry. Two types of excitation are considered: (i) tonal excitation at the frequency of the most unstable disturbances in the natural flow, and (ii) broadband excitation consisting bandpass filtered to the natural unstable frequency range, modelling two common types of airfoil self-noise production. For equal energy input levels, the results show that tonal and broadband types of excitation have equivalent effects on the mean flow field. Specifically, both cause the streamwise extent and height of the bubble to decrease. However, further analysis reveals notable differences in the underlying physics. For the tonal case, the transition process is dominated by the growth of disturbances at the excitation frequency that damps the growth of all other disturbances, leading to the formation of strongly coherent vortices in the aft portion of the separation bubble. On the other hand, broadband excitation promotes more moderate growth of all disturbances within the unstable frequency band, producing less coherent shear layer structures that experience earlier breakdown. Thus, the frequency content of acoustic excitation has a strong influence on the transition process in laminar separation bubbles. The authors gratefully acknowledge the Natural Sciences and Engineering Research Council of Canada (NSERC) for funding this work.

  14. Heat transfer in a laminar separation bubble affected by oscillating external flow

    International Nuclear Information System (INIS)

    Wissink, J.G.; Michelassi, V.; Rodi, W.

    2004-01-01

    A three-dimensional Direct Numerical Simulation (DNS) of passive heat transfer in a Laminar Separation Bubble (LSB) over a flat plate affected by oscillating external flow is presented. The oscillation imposes a periodicity which is employed for phase-averaging. The flat plate is kept at a uniform, low temperature. The local Nusselt number, Nu, is determined as a function of phase. In the dead-air region of the bubble Nu is found to be relatively small, while it peaks in the recirculation region where hot outer fluid gets entrained and is transported towards the flat plate. Each period a new separation bubble is formed, that merges with the old separation bubble. The reverse flow inside the separation bubble reaches values of up to 60% of the local free-stream velocity, which is sufficient to make the separation bubble absolutely unstable such that self-sustained turbulence can exist. For the phase-averaged flow, neither the turbulent viscosity hypothesis nor the temperature gradient-diffusion hypothesis is found to hold

  15. TRANSIENT LAMINAR SEPARATED FLOW AROUND AN IMPULSIVELY STARTED SPHERICAL PARTICLE AT 20≤RE≤1000

    Directory of Open Access Journals (Sweden)

    FARIDA BENABBAS

    2015-12-01

    Full Text Available Numerical simulations of the axisymmetric laminar flow characteristics past a rigid sphere impulsively started are presented for Reynolds numbers from 20 to 1000. The results are obtained by solving the complete time dependant Navier-Stokes equations in vorticity and stream function formulation. A fourth order compact method is used to discretize the Poisson equation of stream function while the vorticity transport equation is solved by an alternating direction implicit method. Time evolution of flow separation angle and length of the vortex behind the sphere are reported. Time variation of the axial velocity in the vortex and the wall vorticity around the sphere are also examined. Secondary vortices are seen to be initiated at Reynolds number of 610 and for dimensionless time t about 5. Comparisons with previously published simulations and experimental data for steady state conditions show very good agreement.

  16. Effect of synthetic jet modulation schemes on the reduction of a laminar separation bubble

    Science.gov (United States)

    Seo, J. H.; Cadieux, F.; Mittal, R.; Deem, E.; Cattafesta, L.

    2018-03-01

    The response of a laminar separation bubble to synthetic jet forcing with various modulation schemes is investigated via direct numerical simulations. A simple sinusoidal waveform is considered as a reference case, and various amplitude modulation schemes, including the square-wave "burst" modulation, are employed in the simulations. The results indicate that burst modulation is less effective at reducing the length of the flow separation than the sinusoidal forcing primarily because burst modulation is associated with a broad spectrum of input frequencies that are higher than the target frequency for the flow control. It is found that such high-frequency forcing delays vortex roll-up and promotes vortex pairing and merging, which have an adverse effect on reducing the separation bubble length. A commonly used amplitude modulation scheme is also found to have reduced effectiveness due to its spectral content. A new amplitude modulation scheme which is tailored to impart more energy at the target frequency is proposed and shown to be more effective than the other modulation schemes. Experimental measurements confirm that modulation schemes can be preserved through the actuator and used to enhance the energy content at the target modulation frequency. The present study therefore suggests that the effectiveness of synthetic jet-based flow control could be improved by carefully designing the spectral content of the modulation scheme.

  17. Serial MR observation of cortical laminar necrosis caused by brain infarction

    Energy Technology Data Exchange (ETDEWEB)

    Komiyama, M.; Nakajima, H.; Nishikawa, M.; Yasui, T. [Department of Neurosurgery, Osaka City General Hospital (Japan)

    1998-12-01

    To examine the chronological changes characteristic of cortical laminar necrosis caused by brain infarction, 16 patients were repeatedly examined using T1-, T2-weighted spin-echo, T2{sup *}-weighted gradient echo, fluid attenuated inversion recovery (FLAIR) images, and contrast enhanced T1-weighted images at 1.0 or 1.5 T. High intensity cortical lesions were visible on the T1-weighted images from 2 weeks after ictus and became prominent at 1 to 3 months, then became less apparent, but occasionally remained at high intensity for 2 years. High intensity cortical lesions on FLAIR images became prominent from 1 month, and then became less prominent from 1 year, but occasionally remained at high intensity for 2 years. Subcortical lesions did not display high intensity on T1-weighted images at any stage. On FLAIR images, subcortical lesions initially showed slightly high intensity and then low intensity from 6 months due to encephalomalacia. Cortical lesions showed prominent contrast enhancement from 2 weeks to 3 months, but subcortical lesions were prominent from 2 weeks only up to 1 month. T2*-weighted images disclosed haemosiderin in 3 of 7 patients, but there was no correlation with cortical short T1 lesions. Cortical laminar necrosis showed characteristic chronological signal changes on T1-weighted images and FLAIR images. Cortical short T1 lesions were found not to be caused by haemorrhagic infarction. (orig.) With 5 figs., 1 tab., 9 refs.

  18. Experiments on transition process of laminar separation bubble on airfoils. Yokukeijo ni shozuru soryu hakuri ho naibu no sen prime i katei ni tsuiteno jikken

    Energy Technology Data Exchange (ETDEWEB)

    Rinoie, K [National Aerospace Lab., Tokyo (Japan); Sato, J [The Univ. of Tokyo., Tokyo (Japan). Faculty of Engineering

    1990-07-05

    Experiments have been done to investigate the transition process of the laminar separation bubble on airfoils. Measurements of the power spectrum density distribution of the streamwise velocity fluctuation was made. Three airfoils which have different steplike pressure distributions were used for measurements. A discrete spectrum and its sub and higher harmonics were observed. The frequeny of the discrete spectrum was in good agreement with that predicted by the linear stability theory of the separated free shear layer. From results, it is concluded that the velocity disturbance observed initially in the amnner separation bubble for the three airfoils shows similar characteristic to that in the separeted free shear layer. For the airfoil whose design pressure recovery is minimum among three airfoils, however, another kind of the discrete spectrum was also observed. This is interpreted to be caused by the interference with the external cyclic disturbance. 11 refs., 11 figs.

  19. Effects of free-stream turbulence intensity on transition in a laminar separation bubble formed over an airfoil

    Science.gov (United States)

    Istvan, Mark S.; Yarusevych, Serhiy

    2018-03-01

    The laminar-to-turbulent transition process in a laminar separation bubble formed over a NACA 0018 airfoil is investigated experimentally. All experiments are performed for an angle of attack of 4°, chord Reynolds numbers of 80,000 and 125,000, and free-stream turbulence intensities between 0.06 and 1.99%. The results show that increasing the level of free-stream turbulence intensity leads to a decrease in separation bubble length, attributed to a downstream shift in mean separation and an upstream shift in mean reattachment, the later ascribed to an upstream shift in mean transition. Maximum spatial amplification rates of disturbances in the separated shear layer decrease with increasing free-stream turbulence intensity, implying that the larger initial amplitudes of disturbances are solely responsible for the upstream shift in mean transition and as a result mean reattachment. At the baseline level of turbulence intensity, coherent structures forming in the aft portion of the bubble are characterized by strong spanwise coherence at formation, and undergo spanwise deformations leading to localized breakup in the vicinity of mean reattachment. As the level of free-stream turbulence intensity is increased, the spanwise coherence of the shear layer rollers is reduced, and spanwise undulations in the vortex filaments start to take place at the mean location of roll-up. At the highest level of turbulence intensity investigated, streamwise streaks originating in the boundary layer upstream of the separation bubble are observed within the bubble. These streaks signify an onset of bypass transition upstream of the separation bubble, which gives rise to a highly three-dimensional shear layer roll-up. A quantitative analysis of the associated changes in salient characteristics of the coherent structures is presented, connecting the effect of elevated free-stream turbulence intensity on the time-averaged and dynamic characteristics of the separation bubble.

  20. Two-dimensional fluid dynamics in a sharply bent channel: Laminar flow, separation bubble, and vortex dynamics

    Science.gov (United States)

    Matsumoto, Daichi; Fukudome, Koji; Wada, Hirofumi

    2016-10-01

    Understanding the hydrodynamic properties of fluid flow in a curving pipe and channel is important for controlling the flow behavior in technologies and biomechanics. The nature of the resulting flow in a bent pipe is extremely complicated because of the presence of a cross-stream secondary flow. In an attempt to disentangle this complexity, we investigate the fluid dynamics in a bent channel via the direct numerical simulation of the Navier-Stokes equation in two spatial dimensions. We exploit the absence of secondary flow from our model and systematically investigate the flow structure along the channel as a function of both the bend angle and Reynolds number of the laminar-to-turbulent regime. We numerically suggest a scaling relation between the shape of the separation bubble and the flow conductance, and construct an integrated phase diagram.

  1. Separation-induced boundary layer transition: Modeling with a non-linear eddy-viscosity model coupled with the laminar kinetic energy equation

    International Nuclear Information System (INIS)

    Vlahostergios, Z.; Yakinthos, K.; Goulas, A.

    2009-01-01

    We present an effort to model the separation-induced transition on a flat plate with a semi-circular leading edge, using a cubic non-linear eddy-viscosity model combined with the laminar kinetic energy. A non-linear model, compared to a linear one, has the advantage to resolve the anisotropic behavior of the Reynolds-stresses in the near-wall region and it provides a more accurate expression for the generation of turbulence in the transport equation of the turbulence kinetic energy. Although in its original formulation the model is not able to accurately predict the separation-induced transition, the inclusion of the laminar kinetic energy increases its accuracy. The adoption of the laminar kinetic energy by the non-linear model is presented in detail, together with some additional modifications required for the adaption of the laminar kinetic energy into the basic concepts of the non-linear eddy-viscosity model. The computational results using the proposed combined model are shown together with the ones obtained using an isotropic linear eddy-viscosity model, which adopts also the laminar kinetic energy concept and in comparison with the existing experimental data.

  2. Inspection of the dynamic properties of laminar separation bubbles: free-stream turbulence intensity effects for different Reynolds numbers

    Science.gov (United States)

    Simoni, Daniele; Lengani, Davide; Ubaldi, Marina; Zunino, Pietro; Dellacasagrande, Matteo

    2017-06-01

    The effects of free-stream turbulence intensity (FSTI) on the transition process of a pressure-induced laminar separation bubble have been studied for different Reynolds numbers (Re) by means of time-resolved (TR) PIV. Measurements have been performed along a flat plate installed within a double-contoured test section, designed to produce an adverse pressure gradient typical of ultra-high-lift turbine blade profiles. A test matrix spanning 3 FSTI levels and 3 Reynolds numbers has been considered allowing estimation of cross effects of these parameters on the instability mechanisms driving the separated flow transition process. Boundary layer integral parameters, spatial growth rate and saturation level of velocity fluctuations are discussed for the different cases in order to characterize the base flow response as well as the time-mean properties of the Kelvin-Helmholtz instability. The inspection of the instantaneous velocity vector maps highlights the dynamics of the large-scale structures shed near the bubble maximum displacement, as well as the low-frequency motion of the fore part of the separated shear layer. Proper Orthogonal Decomposition (POD) has been implemented to reduce the large amount of data for each condition allowing a rapid evaluation of the group velocity, spatial wavelength and dominant frequency of the vortex shedding process. The dimensionless shedding wave number parameter makes evident that the modification of the shear layer thickness at separation due to Reynolds number variation mainly drives the length scale of the rollup vortices, while higher FSTI levels force the onset of the shedding phenomenon to occur upstream due to the higher velocity fluctuations penetrating into the separating boundary layer.

  3. Root cause analysis of thermal sleeve separation

    Energy Technology Data Exchange (ETDEWEB)

    Jo, J. C.; Jhung, M. J.; Yu, S. O.; Kim, H. J.; Yune, Y. K.; Park, J. Y

    2006-01-15

    Thermal sleeves in the shape of thin wall cylinder seated inside the nozzle part of each Safety Injection (SI) line at Pressurized Water Reactors (PWRs) have such functions as prevention and relief of potential excessive transient thermal stress in the wall of SI line nozzle part which is initially heated up with hot water flowing in the primary coolant piping system when cold water is injected into the system through the SI nozzles during the SI operation mode. Recently, mechanical failures that the sleeves were separated from the SI branch pipe and fell into the connected cold leg main pipe occurred in sequence at some typical PWR plants in Korea. To find out the root cause of thermal sleeve breakaway failures, the flow situation in the junction of primary coolant main pipe and SI branch pipe, and the vibration modal characteristics of the thermal sleeve are investigated in detail by using both Computational Fluid Dynamic (CFD) code and structure analysis finite element code. As the results, the transient response in fluid force exerting on the local part of thermal sleeve wall surface to the primary coolant flow through the pipe junction area during the normal reactor operation mode shows oscillatory characteristics with frequencies ranging from 17 to 18, which coincide with one of the lower mode natural frequencies of thermal sleeve having a pinned support condition on the circumferential prominence on the outer surface of thermal sleeve which is put into the circumferential groove on the inner surface of SI nozzle at the mid-height of the thermal sleeve. In addition, the variation of force on the thermal sleeve surface yields alternating torques in the directions of two rectangular axes which are perpendicular to the longitudinal axis of cylindrical thermal sleeve, which cause rolling, pitching and rotating motions of the thermal sleeve. Consequently, it is seen that this flow situation surrounding the thermal sleeve during the normal reactor operation can

  4. Centrifugal Separation Device Based on Two-Layer Laminar Flow in Microchannels for High-Throughput and Continuous Blood Cell/Plasma Separation

    Science.gov (United States)

    Taizo Kobayashi,; Taisuke Funamoto,; Makoto Hosaka,; Satoshi Konishi,

    2010-07-01

    This paper presents a novel type of centrifugation device that is based on the two-layer laminar flow in micro flow channels for continuous blood cell/plasma separation. We propose to rotate the flow channels which are arranged along the circumference around the rotational axis. Downsizing the channel width reduced both the cell sedimentation time and the required centrifugal force, because the channel width corresponds to the centrifugal sedimentation length. First, plasma and cells were continuously extracted from pig blood in each of the branch channels using a milled acrylic prototype device (channel width = 800 μm, volume = 150 μl). Next, the relationship between the channel width (125, 250, and 500 μm) and the sedimentation time taken for various centrifugal forces (2.3, 9, 36, and 145 G) was evaluated using the downsized microchannels fabricated by hot-embossing and thermal bonding technologies. Using downsized microchannels with a width of 125 μm successfully reduced the sedimentation time to 85 s as compared to the sedimentation time of 270 s for a channel of a width of 500 μm, when a centrifugal force of 2.3 G was applied. The use of the proposed device did not result in obvious hemolysis at the centrifugal forces lower than 335 G.

  5. Heat-transfer and pressure distributions for laminar separated flows downstream of rearward-facing steps with and without mass suction

    Science.gov (United States)

    Brown, R. D.; Jakubowski, A. K.

    1974-01-01

    Heat-transfer and pressure distributions were measured for laminar separated flows downstream of rearward-facing steps with and without mass suction. The flow conditions were such that the boundary-layer thickness was comparable to or larger than the step height. For both suction and no-suction cases, an increase in the step height resulted in a sharp decrease in the initial heat-transfer rates behind the step. Downstream, however, the heat transfer gradually recovered back to less than or near attached-flow values. Mass suction from the step base area increased the local heat-transfer rates; however, this effect was relatively weak for the laminar flows considered. Even removal of the entire approaching boundary layer raised the post-step heat-transfer rates only about 10 percent above the flatplate values. Post-step pressure distributions were found to depend on the entrainment conditions at separation. In the case of the solid-faced step, a sharp pressure drop behind the step was followed by a very short plateau and relatively fast recompression. For the slotted-step connected to a large plenum but without suction, the pressure drop at the base was much smaller and the downstream recompression more gradual than that for solid-faced step.

  6. Development of Tollmien-Schlichting disturbances in the presence of laminar separation bubbles on an unswept infinite wavy wing

    Science.gov (United States)

    Thomas, Christian; Mughal, Shahid; Ashworth, Richard

    2017-04-01

    The effect of long-wavelength sinusoidal surface waviness on the development of Tollmien-Schlichting (TS) wave instabilities is investigated. The analysis is based on the compressible flow that forms over an unswept infinite wavy wing with surface variations of variable amplitude, wavelength, and phase. Boundary layer profiles are extracted directly from solutions of a Navier-Stokes solver, which allows a thorough parametric analysis to be undertaken. Many wavy surface configurations are examined that can be sufficient to establish localized pockets of separated flow. Linear stability analysis is undertaken using parabolized stability equations (PSE) and linearized Navier-Stokes (LNS) methods, and surface waviness is generally found to enhance unstable behavior. Results of the two schemes are compared and criteria for PSE to establish accurate solutions in separated flows are determined, which are based on the number of TS waves per wavelength of the surface deformation. Relationships are formulated, relating the instability variations to the surface parameters, which are consistent with previous observations regarding the growth of TS waves on a flat plate. Additionally, some long-wavelength surface deformations are found to stabilize TS disturbances.

  7. High-grain diet feeding altered the composition and functions of the rumen bacterial community and caused the damage to the laminar tissues of goats.

    Science.gov (United States)

    Zhang, R Y; Jin, W; Feng, P F; Liu, J H; Mao, S Y

    2018-03-19

    In the current intensive production system, ruminants are often fed high-grain (HG) diets. However, this feeding pattern often causes rumen metabolic disorders and may further trigger laminitis, the exact mechanism is not clear. This study investigated the effect of HG diet feeding on fermentative and microbial changes in the rumen and on the expression of pro-inflammatory cytokines and matrix metalloproteinases (MMPs) in the lamellar tissue. In all, 12 male goats were fed a hay diet (0% grain; n=6) or an HG diet (56.5% grain; n=6). On day 50 of treatment, samples of blood, rumen content, and lamellar tissue of hooves of goats were collected. The data showed that compared with the hay group, HG-fed goats had lower (Pdiet feeding altered the composition of rumen bacterial community, and correspondingly, the results suggested that their functions in the HG group were also altered. HG diet feeding increased (Pbacterial community, and lead to higher levels of LPS in the peripheral blood, and further activated the inflammatory response in lamellar tissues, which may progress to the level of laminar damage.

  8. [Endodontic treatment of a periapical lesion causing root separation].

    Science.gov (United States)

    Canalda Sahli, C

    1990-01-01

    A case is presented of a periapical lesion of a rather large size, which produced an important separation of two inferior incisor roots. The root canal was treated, with calcium hydroxide overextending the apex. Clinic and radiographic control after two years complete reparation of the periapex.

  9. Effects of ship motions on laminar flow in tubes

    Energy Technology Data Exchange (ETDEWEB)

    Yan, B.H., E-mail: yanbh1986@163.co [Department of Nuclear Science and Engineering, Naval University of Engineering, 717 Jiefang Street, Wuhan 430033 (China); Yu, L. [Department of Nuclear Science and Engineering, Naval University of Engineering, 717 Jiefang Street, Wuhan 430033 (China); Yang, Y.H. [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai 200240 (China)

    2010-01-15

    The thermal-hydraulics of barge-mounted floating nuclear desalination plants is the incentive for this study. Laminar flow in tubes in heaving motion is modeled. The friction factor and heat transfer coefficient are obtained. All the equations of laminar flow in steady state are applicable for heeling motion. The effect of ship motions on the laminar developing region is also analyzed. The ship motions can weaken the boundary layer in the laminar developing region and strengthen the laminar frictional resistance. The effect of ship motions on the instability of laminar flow is also investigated. The ship motions do not affect the instability point, but they can shorten the distance between the instability point and the transition point, and cause the transition from laminar flow to turbulent flow to occur earlier.

  10. Laminar separation bubbles: Dynamics and control

    Indian Academy of Sciences (India)

    e-mail: {diwan,onr}@aero.iisc.ernet.in. Abstract. ... of thin aerofoils, on gas turbine blades and on low Reynolds number micro-aero-vehicle wings. ... Surface and smoke flow visualisation techniques were employed to measure the length and ...

  11. Root cause analysis of SI line-seated thermal sleeve separation failures

    International Nuclear Information System (INIS)

    Jo, Jong Chull; Jhung, Myung Jo; Kim, Hho Jung

    2004-01-01

    At conventional pressurized water reactors, a thermal sleeve (named simply 'sleeve' hereafter) is seated inside the nozzle part of each Safety Injection (SI) branch pipe to prevent and relieve potential excessive transient thermal stress in the nozzle wall when a cold water is injected during the safety injection mode Recently, mechanical failures that the sleeves are separated from the SI branch pipe and fall into the connected cold leg main pipe were occurred in sequence at Yonggwang units 5 and 6 and Ulchin unit 5. There were many activities and efforts to figure out the causes of those failures with experts' reasoning, but the proposed causes were derived from superficial views rather than physically concrete grounds or analysis results. The prerequisites to find out the root causes of failure mechanism will be to identify the flow situation in the pipe junction area connecting the cold leg with the SI pipe and to know the vibration characteristics of sleeves. This paper investigates the flow field in the pipe junction thru a numerical simulation and vibration characteristics of thermal sleeves thru a modal analysis, from which the root causes of sleeve separation mechanism are analyzed

  12. Reversing flow causes passive shark scale actuation in a separating turbulent boundary layer

    Science.gov (United States)

    Lang, Amy; Gemmell, Bradford; Motta, Phil; Habegger, Laura; Du Clos, Kevin; Devey, Sean; Stanley, Caleb; Santos, Leo

    2017-11-01

    Control of flow separation by shortfin mako skin in experiments has been demonstrated, but the mechanism is still poorly understood yet must be to some extent Re independent. The hypothesized mechanisms inherent in the shark skin for controlling flow separation are: (1) the scales, which are capable of being bristled only by reversing flow, inhibit flow reversal events from further development into larger-scale separation and (2) the cavities formed when scales bristle induces mixing of high momentum flow towards the wall thus energizing the flow close to the surface. Two studies were carried out to measure passive scale actuation caused by reversing flow. A small flow channel induced an unsteady, wake flow over the scales prompting reversing flow events and scale actuation. To resolve the flow and scale movements simultaneously we used specialized optics at high magnification (1 mm field of view) at 50,000 fps. In another study, 3D printed models of shark scales, or microflaps (bristling capability up to 50 degrees), were set into a flat plate. Using a tripped, turbulent boundary layer grown over the long flat plate and a localized adverse pressure gradient, a separation bubble was generated within which the microflaps were placed. Passive flow actuation of both shark scales and microflaps by reversing flow was observed. Funding from Army Research Office and NSF REU site Grant.

  13. Segmental and laminar organization of the spinal neurons projecting to the periaqueductal gray (PAG) in the cat suggests the existence of at least five separate clusters of spino-PAG neurons

    NARCIS (Netherlands)

    Mouton, Leonora J.; Holstege, Gert

    2000-01-01

    The present retrograde tracing study in the cat describes the spinal cord projections to the periaqueductal gray (PAC), taking into account different regions of the PAG and all spinal segments. Results show that injecting different parts of the PAC leads to different laminar and segmental

  14. Aerodynamic study of a small wind turbine with emphasis on laminar and transition flows

    Science.gov (United States)

    Niculescu, M. L.; Cojocaru, M. G.; Crunteanu, D. E.

    2016-06-01

    The wind energy is huge but unfortunately, wind turbines capture only a little part of this enormous green energy. Furthermore, it is impossible to put multi megawatt wind turbines in the cities because they generate a lot of noise and discomfort. Instead, it is possible to install small Darrieus and horizontal-axis wind turbines with low tip speed ratios in order to mitigate the noise as much as possible. Unfortunately, the flow around this wind turbine is quite complex because the run at low Reynolds numbers. Therefore, this flow is usually a mixture of laminar, transition and laminar regimes with bubble laminar separation that is very difficult to simulate from the numerical point of view. Usually, transition and laminar regimes with bubble laminar separation are ignored. For this reason, this paper deals with laminar and transition flows in order to provide some brightness in this field.

  15. MRI of laminar heterotopic grey matter

    International Nuclear Information System (INIS)

    Vahldiek, G.; Terwey, B.; Hanefeld, F.; Sperner, J.

    1990-01-01

    In one baby and 2 infants who presented with psychomotor retardation and epilepsy laminar heterotopic grey matter was demonstrated via magnetic resonance imaging. Laminar heterotopia is a rare migrational disorder with bilateral symmetric ribbons of grey matter within the centrum semiovale, separated from ventricular walls and from obviously normal-sized cortex by broad layers of white matter. The heterotopic grey matter has a signal intensity which is isointense compared with that of normal cortex irrespective of image weighting. On account of this signal behaviour differentiation against other white matter diseases is easy. The knowledge of these pathognomonic findings facilitates correct diagnosis, especially during the first and the second year of life, when signal intensities of white and grey matter differ from normal findings because of the occasionally delayed myelination process. Therefore, further diagnostic procedures can be avoided and early counseling of parents is possible. (orig.) [de

  16. Mobile bank conditions for laminar microrivers

    OpenAIRE

    Devauchelle , Olivier; Josserand , Christophe; Lagrée , Pierre-Yves; Zaleski , Stéphane

    2008-01-01

    International audience; The present study aims to establish a simple mechanistic model for river bank erosion. Recent experiments demonstrate that small-scale laminar flumes can develop erosion structures similar to those encountered in Nature. From the Saint-Venant Equations, a classical sediment transport law and a simple avalanche model, it is shown that bank failure caused by flow erosion can be represented through simple boundary conditions. These conditions are able to deal with the wat...

  17. Controlling Separation in Turbomachines

    Science.gov (United States)

    Evans, Simon; Himmel, Christoph; Power, Bronwyn; Wakelam, Christian; Xu, Liping; Hynes, Tom; Hodson, Howard

    2010-01-01

    Four examples of flow control: 1) Passive control of LP turbine blades (Laminar separation control). 2) Aspiration of a conventional axial compressor blade (Turbulent separation control). 3) Compressor blade designed for aspiration (Turbulent separation control). 4.Control of intakes in crosswinds (Turbulent separation control).

  18. Genetic Separation of Listeria monocytogenes Causing Central Nervous System Infections in Animals

    Directory of Open Access Journals (Sweden)

    Lisandra Aguilar-Bultet

    2018-02-01

    Full Text Available Listeria monocytogenes is a foodborne pathogen that causes abortion, septicemia, gastroenteritis and central nervous system (CNS infections in ruminants and humans. L. monocytogenes strains mainly belong to two distinct phylogenetic groups, named lineages I and II. In general, clinical cases in humans and animals, in particular CNS infections, are caused by lineage I strains, while most of the environmental and food strains belong to lineage II. Little is known about why lineage I is more virulent than lineage II, even though various molecular factors and mechanisms associated with pathogenesis are known. In this study, we have used a variety of whole genome sequence analyses and comparative genomic tools in order to find characteristics that distinguish lineage I from lineage II strains and CNS infection strains from non-CNS strains. We analyzed 225 strains and identified single nucleotide variants between lineages I and II, as well as differences in the gene content. Using a novel approach based on Reads Per Kilobase per Million Mapped (RPKM, we identified 167 genes predominantly absent in lineage II but present in lineage I. These genes are mostly encoding for membrane-associated proteins. Additionally, we found 77 genes that are largely absent in the non-CNS associated strains, while 39 genes are especially lacking in our defined “non-clinical” group. Based on the RPKM analysis and the metadata linked to the L. monocytogenes strains, we identified 6 genes potentially associated with CNS cases, which include a transcriptional regulator, an ABC transporter and a non-coding RNA. Although there is not a clear separation between pathogenic and non-pathogenic strains based on phylogenetic lineages, the presence of the genes identified in our study reveals potential pathogenesis traits in ruminant L. monocytogenes strains. Ultimately, the differences that we have found in our study will help steer future studies in understanding the virulence

  19. Genetic Separation of Listeria monocytogenes Causing Central Nervous System Infections in Animals

    Science.gov (United States)

    Aguilar-Bultet, Lisandra; Nicholson, Pamela; Rychener, Lorenz; Dreyer, Margaux; Gözel, Bulent; Origgi, Francesco C.; Oevermann, Anna; Frey, Joachim; Falquet, Laurent

    2018-01-01

    Listeria monocytogenes is a foodborne pathogen that causes abortion, septicemia, gastroenteritis and central nervous system (CNS) infections in ruminants and humans. L. monocytogenes strains mainly belong to two distinct phylogenetic groups, named lineages I and II. In general, clinical cases in humans and animals, in particular CNS infections, are caused by lineage I strains, while most of the environmental and food strains belong to lineage II. Little is known about why lineage I is more virulent than lineage II, even though various molecular factors and mechanisms associated with pathogenesis are known. In this study, we have used a variety of whole genome sequence analyses and comparative genomic tools in order to find characteristics that distinguish lineage I from lineage II strains and CNS infection strains from non-CNS strains. We analyzed 225 strains and identified single nucleotide variants between lineages I and II, as well as differences in the gene content. Using a novel approach based on Reads Per Kilobase per Million Mapped (RPKM), we identified 167 genes predominantly absent in lineage II but present in lineage I. These genes are mostly encoding for membrane-associated proteins. Additionally, we found 77 genes that are largely absent in the non-CNS associated strains, while 39 genes are especially lacking in our defined “non-clinical” group. Based on the RPKM analysis and the metadata linked to the L. monocytogenes strains, we identified 6 genes potentially associated with CNS cases, which include a transcriptional regulator, an ABC transporter and a non-coding RNA. Although there is not a clear separation between pathogenic and non-pathogenic strains based on phylogenetic lineages, the presence of the genes identified in our study reveals potential pathogenesis traits in ruminant L. monocytogenes strains. Ultimately, the differences that we have found in our study will help steer future studies in understanding the virulence mechanisms of the

  20. Factors influencing flow steadiness in laminar boundary layer shock interactions

    Science.gov (United States)

    Tumuklu, Ozgur; Levin, Deborah A.; Gimelshein, Sergey F.; Austin, Joanna M.

    2016-11-01

    The Direct Simulation Monte Carlo method has been used to model laminar shock wave boundary interactions of hypersonic flow over a 30/55-deg double-wedge and "tick-shaped" model configurations studied in the Hypervelocity Expansion Tube facility and T-ADFA free-piston shock tunnel, respectively. The impact of thermochemical effects on these interactions by changing the chemical composition from nitrogen to air as well as argon for a stagnation enthalpy of 8.0 MJ/kg flow are investigated using the 2-D wedge model. The simulations are found to reproduce many of the classic features related to Edney Type V strong shock interactions that include the attached, oblique shock formed over the first wedge, the detached bow shock from the second wedge, the separation zone, and the separation and reattachment shocks that cause complex features such as the triple point for both cases. However, results of a reacting air flow case indicate that the size of the separation length, and the movement of the triple point toward to the leading edge is much less than the nitrogen case.

  1. Cubierta laminar prefabricada, Suiza

    Directory of Open Access Journals (Sweden)

    Hossdorf, Heinz

    1964-04-01

    Full Text Available The roof constructed recently near Olten, in Switzerland, consists of a series of cylindrical shell surfaces, with skylights between the successive shells. It covers an area of 13.500 m2, and the building is to be used as a storehouse and servicing installation for the Federation of Consumer Goods Society. The general nature of the design made it logical, from the outset, to construct the roof as a number of similar prefabricated units. This method had evident economic advantages. The repetition of similar cylindrical roof sections made it possible to reiterate also the particular constructive process which was adopted in this case. The prefabricated shell units have been reinforced with lateral ribs, which make them sufficiently stiff to be handled at the working site. Each unit is 25.20 m long and spans a width of 1.40 ms. The roof is made up of 18 such elements. A feature of this roof is that it has been subjected to a prestressing process, applied by cables, running along the extrados of the cylindrical surface of each unit. This improves the stability and strength of the shells, and induces favourable stresses which counteract noticeably the effects of the shear forces and bending moments. The edges of these shells have been reinforced by increasing the thickness of the ribs, thereby improving the end anchorage. In order to check the theoretical calculations for this structure, several tests were carried out on scale models.La cubierta recientemente construida en las cercanías de Olten (Suiza, de tipo laminar, especial, curvada, constituida por una serie de superficies cilíndricas sucesivas y con lucernario en las soluciones de continuidad que cada par de superficies parciales cilíndricas motiva, tiene por principal objeto cubrir una superficie de 13.500 m2 edificados con destino a los servicios y explotación de un almacén de la Federación de Sociedades de Consumo. Debido a las ideas generales básicas del proyecto se impuso, desde un

  2. Adsorption of a novel reagent scheme on scheelite and calcite causing an effective flotation separation.

    Science.gov (United States)

    Gao, Yuesheng; Gao, Zhiyong; Sun, Wei; Yin, Zhigang; Wang, Jianjun; Hu, Yuehua

    2018-02-15

    The efficient separation of scheelite from calcium-bearing minerals, especially calcite, remains a challenge in practice. In this work, a novel reagent scheme incorporating a depressant of sodium hexametaphosphate (SHMP) and a collector mixture of octyl hydroxamic acid (HXMA-8) and sodium oleate (NaOl) was employed in both single and mixed binary mineral flotation, and it proved to be highly effective for the separation. Furthermore, the role of the pH value in the separation was evaluated. Additionally, the mechanism of the selective separation was investigated systemically via zeta potential measurements, fourier transform infrared (FTIR) spectroscopy analysis, X-ray photoelectron (XPS) spectroscopy analysis and crystal chemistry calculations. It turns out that the selective chemisorption of SHMP on calcite (in the form of complexation between H 2 PO 4 - /HPO 4 2- and Ca 2+ ) over scheelite is ascribed to the stronger reactivity and higher density of Ca ions on the commonly exposed surfaces of calcite minerals. The intense adsorption of HXMA-8 on scheelite over calcite due to the match of the OO distances in WO 4 2- of scheelite and CONHOH of HXMA-8 holds the key to the successful separation. We were also interested in warranting the previous claim that NaOl is readily adsorbed on both minerals via chemisorption. Our results provided valuable insights into the application of mixed collectors and an effective depressant for flotation separation. Copyright © 2017 Elsevier Inc. All rights reserved.

  3. Dietary choline during periadolescence attenuates cognitive damage caused by neonatal maternal separation in male rats.

    Science.gov (United States)

    Moreno Gudiño, Hayarelis; Carías Picón, Diamela; de Brugada Sauras, Isabel

    2017-07-01

    Choline (Ch) is an essential nutrient that acts as a cognitive facilitator when administered during perinatal periods, and it has been recognised as a 'pharmacological' agent that can ease cognitive dysfunctions provoked by exposure to damaging stimuli during early developmental stages. The aim of the present work is to determine whether providing a diet rich in Ch would reduce the severity of the memory deficit provoked by a neonatal stress episode in male adult rats. The effect of Ch on memory was measured using memory tasks such as object and place recognition. Ontogenetic manipulations were conducted during two sensitive developmental periods. During the first post-natal (PN) 14 days, only the male rat pups were selected and half of them were separated from the mother, group maternal separation (MS). Subsequently, during periadolescence (PN 21-60), the rats were exposed to a deficient (DEF = 0 g/kg Ch chloride), sufficient (CON = 1.1 g/kg Ch chloride), or supplemented (SUP = 5 g/kg Ch chloride) diets for this nutrient. The results indicated that for group MS, only rats fed with the SUP diet were able to recognise the familiar object and place that had been experienced 24 hours before, unlike groups DEF and CON. In addition, whereas rats in the non-separated group (No-MS) recognised the object independently of the diet, only rats that received a DEF diet failed to recognise the place, showing that a Ch deficit affects spatial memory tasks. These results show that Ch supplementation during periadolescence can attenuate the memory deficit provoked by extended neonatal stress.

  4. Hilar Mossy Cell Degeneration Causes Transient Dentate Granule Cell Hyperexcitability and Impaired Pattern Separation

    Science.gov (United States)

    Jinde, Seiichiro; Zsiros, Veronika; Jiang, Zhihong; Nakao, Kazuhito; Pickel, James; Kohno, Kenji; Belforte, Juan E.; Nakazawa, Kazu

    2012-01-01

    Summary Although excitatory mossy cells of the hippocampal hilar region are known to project both to dentate granule cells and to interneurons, it is as yet unclear whether mossy cell activity’s net effect on granule cells is excitatory or inhibitory. To explore their influence on dentate excitability and hippocampal function, we generated a conditional transgenic mouse line, using the Cre/loxP system, in which diphtheria toxin receptor was selectively expressed in mossy cells. One week after injecting toxin into this line, mossy cells throughout the longitudinal axis were degenerated extensively, theta wave power of dentate local field potentials increased during exploration, and deficits occurred in contextual discrimination. By contrast, we detected no epileptiform activity, spontaneous behavioral seizures, or mossy-fiber sprouting 5–6 weeks after mossy cell degeneration. These results indicate that the net effect of mossy cell excitation is to inhibit granule cell activity and enable dentate pattern separation. PMID:23259953

  5. Ratchet Transport of Chiral Particles Caused by the Transversal Asymmetry: Current Reversals and Particle Separation

    Science.gov (United States)

    Liu, Jian-li; Lu, Shi-cai; Ai, Bao-quan

    2018-06-01

    Due to the chirality of active particles, the transversal asymmetry can induce the the longitudinal directed transport. The transport of chiral active particles in a periodic channel is investigated in the presence of two types of the transversal asymmetry, the transverse force and the transverse rigid half-circle obstacles. For all cases, the counterclockwise and clockwise particles move to the opposite directions. For the case of the only transverse force, the chiral active particles can reverse their directions when increasing the transverse force. When the transverse rigid half-circle obstacles are introduced, the transport behavior of particles becomes more complex and multiple current reversals occur. The direction of the transport is determined by the competition between two types of the transversal asymmetry. For a given chirality, by suitably tailoring parameters, particles with different self-propulsion speed can move in different directions and can be separated.

  6. Arsenic contamination of underground water in Bangladesh: cause, effect, separation, determination and remedy

    International Nuclear Information System (INIS)

    Ahmed, M.J.

    2003-01-01

    Arsenic contamination of underground water of Bangladesh has become the gravest concern for the lives of millions of people of this land. Probable causes and effects of arsenic contamination of underground water of Bangladesh have been extensively discussed. The extent of current knowledge regarding the specification of arsenic in environmental waters in delineated. A simple, non-extractive, highly sensitive and selective quench photometric methods for the rapid determination of arsenic at trace levels in aqueous medium has been developed. This paper also presents a short review of the technologies used for arsenic removal of underground water in Bangladesh. (author)

  7. Notes on the Prediction of Shock-induced Boundary-layer Separation

    Science.gov (United States)

    Lange, Roy H.

    1953-01-01

    The present status of available information relative to the prediction of shock-induced boundary-layer separation is discussed. Experimental results showing the effects of Reynolds number and Mach number on the separation of both laminar and turbulent boundary layer are given and compared with available methods for predicting separation. The flow phenomena associated with separation caused by forward-facing steps, wedges, and incident shock waves are discussed. Applications of the flat-plate data to problems of separation on spoilers, diffusers, and scoop inlets are indicated for turbulent boundary layers.

  8. Reye's syndrome with cortical laminar necrosis: MRI

    International Nuclear Information System (INIS)

    Kinoshita, T.; Takahashi, S.; Ishii, K.; Higano, S.; Matsumoto, K.; Sakamoto, K.; Haginoya, K.; Iinuma, K.

    1996-01-01

    Serial MRI findings are described in two patients with Reye's syndrome, demonstrating diffuse cortical and white matter changes. In the acute stage, T2-weighted images showed subtle but definite laminar high signal and contrast-enhanced T1-weighted images laminar enhancement, along the entire cerebral cortex bilaterally. In the chronic stage, unenhanced T1-weighted images showed diffuse cortical laminar high signal. These characteristic MRI features seemed very similar to those of laminar cortical necrosis in hypoxic brain damage. MRI also displayed delayed white matter changes with cerebral atrophy. (orig.)

  9. Heat transfer of pulsating laminar flow in pipes with wall thermal inertia

    International Nuclear Information System (INIS)

    Yuan, Hongsheng; Tan, Sichao; Wen, Jing; Zhuang, Nailiang

    2016-01-01

    The effects of wall thermal inertia on heat transfer of pulsating laminar flow with constant power density within the pipe wall are investigated theoretically. The energy equation of the fully developed flow and heat transfer is solved by separation of variables and Green's function. The effects of the pulsation amplitude and frequency, the Prandtl number and the wall heat capacity on heat transfer features characterized by temperature, heat flux and Nusselt number are analyzed. The results show that the oscillation of wall heat flux increases along with the wall thermal inertia, while the oscillation of temperature and Nusselt number is suppressed by the wall thermal inertia. The influence of pulsation on the average Nusselt number is also obtained. The pulsating laminar flow can reduce the average Nusselt number. The Nusselt number reduction of pipe flow are a little more remarkable than that of flow between parallel plates, which is mainly caused by differences in hydraulic and thermal performances of the channels. (authors)

  10. Mobile Bank Conditions for Laminar Micro-Rivers

    OpenAIRE

    Devauchelle, Olivier; Josserand, Christophe; Lagrée, Pierre-Yves; Zaleski, Stéphane

    2008-01-01

    International audience; The present study aims to establish a simple mechanistic model for river bank erosion. Recent experiments demonstrate that small-scale laminar flumes can develop erosion structures similar to those encountered in Nature. From Saint-Venant's Equations, a classical sediment transport law and a simple avalanche model, it is shown that bank failure caused by flow erosion can be represented through simple boundary conditions. These conditions are able to deal with the water...

  11. Large Spatial and Temporal Separations of Cause and Effect in Policy Making - Dealing with Non-linear Effects

    Science.gov (United States)

    McCaskill, John

    There can be large spatial and temporal separation of cause and effect in policy making. Determining the correct linkage between policy inputs and outcomes can be highly impractical in the complex environments faced by policy makers. In attempting to see and plan for the probable outcomes, standard linear models often overlook, ignore, or are unable to predict catastrophic events that only seem improbable due to the issue of multiple feedback loops. There are several issues with the makeup and behaviors of complex systems that explain the difficulty many mathematical models (factor analysis/structural equation modeling) have in dealing with non-linear effects in complex systems. This chapter highlights those problem issues and offers insights to the usefulness of ABM in dealing with non-linear effects in complex policy making environments.

  12. Cigarette smoke extract counteracts atheroprotective effects of high laminar flow on endothelial function

    Directory of Open Access Journals (Sweden)

    Sindy Giebe

    2017-08-01

    Full Text Available Tobacco smoking and hemodynamic forces are key stimuli in the development of endothelial dysfunction and atherosclerosis. High laminar flow has an atheroprotective effect on the endothelium and leads to a reduced response of endothelial cells to cardiovascular risk factors compared to regions with disturbed or low laminar flow. We hypothesize that the atheroprotective effect of high laminar flow could delay the development of endothelial dysfunction caused by cigarette smoking. Primary human endothelial cells were stimulated with increasing dosages of aqueous cigarette smoke extract (CSEaq. CSEaq reduced cell viability in a dose-dependent manner. The main mediator of cellular adaption to oxidative stress, nuclear factor erythroid 2-related factor 2 (NRF2 and its target genes heme oxygenase (decycling 1 (HMOX1 or NAD(PH quinone dehydrogenase 1 (NQO1 were strongly increased by CSEaq in a dose-dependent manner. High laminar flow induced elongation of endothelial cells in the direction of flow, activated the AKT/eNOS pathway, increased eNOS expression, phosphorylation and NO release. These increases were inhibited by CSEaq. Pro-inflammatory adhesion molecules intercellular adhesion molecule-1 (ICAM1, vascular cell adhesion molecule-1 (VCAM1, selectin E (SELE and chemokine (C-C motif ligand 2 (CCL2/MCP-1 were increased by CSEaq. Low laminar flow induced VCAM1 and SELE compared to high laminar flow. High laminar flow improved endothelial wound healing. This protective effect was inhibited by CSEaq in a dose-dependent manner through the AKT/eNOS pathway. Low as well as high laminar flow decreased adhesion of monocytes to endothelial cells. Whereas, monocyte adhesion was increased by CSEaq under low laminar flow, this was not evident under high laminar flow.This study shows the activation of major atherosclerotic key parameters by CSEaq. Within this process, high laminar flow is likely to reduce the harmful effects of CSEaq to a certain degree. The

  13. Vasorelaxation responses to insulin in laminar vessel rings from healthy, lean horses.

    Science.gov (United States)

    Wooldridge, A A; Waguespack, R W; Schwartz, D D; Venugopal, C S; Eades, S C; Beadle, R E

    2014-10-01

    Hyperinsulinemia causes laminitis experimentally and is a risk factor for naturally occurring laminitis. The aim of this study was to investigate the effects of insulin on laminar vascular relaxation and to induce insulin-associated vascular dysfunction in vitro. Relaxation responses of isolated laminar arterial and venous rings to acetylcholine and insulin were evaluated. To alter vascular function in response to insulin, all vessel rings were incubated with insulin or vehicle, submaximally contracted, administered insulin again and relaxation responses recorded. Laminar arteries were also incubated with the mitogen-activated protein kinase (MAPK) inhibitor, PD-98059. Relaxation in response to acetylcholine was not different between arteries and veins, but veins relaxed less in response to insulin than arteries. In arteries incubated with insulin, the subsequent relaxation response to insulin was blunted. Veins had minimal relaxation to insulin regardless of incubation. Arteries incubated with PD-98059 relaxed more in response to insulin than arteries not exposed to PD-98059, indicating that MAPK plays a role in maintenance of basal tone in laminar arteries. A differing response of laminar veins and arteries to insulin-induced relaxation may be important in understanding the link between hyperinsulinemia and laminitis. In vitro induction of vascular dysfunction in response to insulin in laminar arteries may be useful for testing therapeutic interventions and for understanding the pathophysiology of laminitis. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Separation of flow

    CERN Document Server

    Chang, Paul K

    2014-01-01

    Interdisciplinary and Advanced Topics in Science and Engineering, Volume 3: Separation of Flow presents the problem of the separation of fluid flow. This book provides information covering the fields of basic physical processes, analyses, and experiments concerning flow separation.Organized into 12 chapters, this volume begins with an overview of the flow separation on the body surface as discusses in various classical examples. This text then examines the analytical and experimental results of the laminar boundary layer of steady, two-dimensional flows in the subsonic speed range. Other chapt

  15. Laminar iridium coating produced by pulse current electrodeposition from chloride molten salt

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Li’an, E-mail: mr_zla@163.com; Bai, Shuxin; Zhang, Hong; Ye, Yicong

    2013-10-01

    Due to the unique physical and chemical properties, Iridium (Ir) is one of the most promising oxidation-resistant coatings for refractory materials above 1800 °C in aerospace field. However, the Ir coatings prepared by traditional methods are composed of columnar grains throughout the coating thickness. The columnar structure of the coating is considered to do harm to its oxidation resistance. The laminar Ir coating is expected to have a better high-temperature oxidation resistance than the columnar Ir coating does. The pulse current electrodeposition, with three independent parameters: average current density (J{sub m}), duty cycle (R) and pulse frequency (f), is considered to be a promising method to fabricate layered Ir coating. In this study, laminar Ir coatings were prepared by pulse current electrodeposition in chloride molten salt. The morphology, roughness and texture of the coatings were determined by scanning electron microscope (SEM), profilometer and X-ray diffraction (XRD), respectively. The results showed that the laminar Ir coatings were composed of a nucleation layer with columnar structure and a growth layer with laminar structure. The top surfaces of the laminar Ir coatings consisted of cauliflower-like aggregates containing many fine grains, which were separated by deep grooves. The laminar Ir coating produced at the deposition condition of 20 mA/cm{sup 2} (J{sub m}), 10% (R) and 6 Hz (f) was quite smooth (R{sub a} 1.01 ± 0.09 μm) with extremely high degree of preferred orientation of 〈1 1 1〉, and its laminar structure was well developed with clear boundaries and uniform thickness of sub-layers.

  16. Drag Reduction by Laminar Flow Control

    Directory of Open Access Journals (Sweden)

    Nils Beck

    2018-01-01

    Full Text Available The Energy System Transition in Aviation research project of the Aeronautics Research Center Niedersachsen (NFL searches for potentially game-changing technologies to reduce the carbon footprint of aviation by promoting and enabling new propulsion and drag reduction technologies. The greatest potential for aerodynamic drag reduction is seen in laminar flow control by boundary layer suction. While most of the research so far has been on partial laminarization by application of Natural Laminar Flow (NLF and Hybrid Laminar Flow Control (HLFC to wings, complete laminarization of wings, tails and fuselages promises much higher gains. The potential drag reduction and suction requirements, including the necessary compressor power, are calculated on component level using a flow solver with viscid/inviscid coupling and a 3D Reynolds-Averaged Navier-Stokes (RANS solver. The effect on total aircraft drag is estimated for a state-of-the-art mid-range aircraft configuration using preliminary aircraft design methods, showing that total cruise drag can be halved compared to today’s turbulent aircraft.

  17. What is the role of laminar cirrus cloud on regulating the cross-tropopause water vapor transport?

    Science.gov (United States)

    Wu, D. L.; Gong, J.; Tsai, V.

    2016-12-01

    Laminar cirrus is an extremely thin ice cloud found persistently inhabit in the tropical and subtropical tropopause. Due to its sub-visible optical depth and high formation altitude, knowledge about the characteristics of this special type of cloud is very limited, and debates are ongoing about its role on regulating the cross-tropopause transport of water vapor. The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the CALIPSO satellite has been continuously providing us with unprecedented details of the laminar cirrus since its launch in 2006. In this research, we adapted Winker and Trepte (1998)'s eyeball detection method. A JAVA-based applet and graphical user interface (GUI) is developed to manually select the laminar, which then automatically record the cloud properties, such as spatial location, shape, thickness, tilt angle, and whether its isolated or directly above a deep convective cloud. Monthly statistics of the laminar cirrus are then separately analyzed according to the orbit node, isolated/convective, banded/non-banded, etc. Monthly statistics support a diurnal difference in the occurring frequency and formation height of the laminar cirrus. Also, isolated and convective laminars show diverse behaviors (height, location, distribution, etc.), which strongly implies that their formation mechanisms and their roles on depleting the upper troposphere water vapor are distinct. We further study the relationship between laminar characteristics and collocated and coincident water vapor gradient measurements from Aura Microwave Limb Sounder (MLS) observations below and above the laminars. The identified relationship provides a quantitative answer to the role laminar cirrus plays on regulating the water vapor entering the stratosphere.

  18. A Study of Laminar Backward-Facing Step Flow

    DEFF Research Database (Denmark)

    Davidson, Lars; Nielsen, Peter V.

    The laminar flow for a backwards facing step is studied. This work was initially part of the work presented in. In that work low-Reynolds number effects was studied, and the plan was also to include laminar flow. However, it turned out that when the numerical predictions of the laminar flow (Re...

  19. Discrete-Roughness-Element-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers

    Science.gov (United States)

    Malik, Mujeeb; Liao, Wei; Li, Fei; Choudhari, Meelan

    2015-01-01

    Nonlinear parabolized stability equations and secondary-instability analyses are used to provide a computational assessment of the potential use of the discrete-roughness-element technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural-laminar-flow airfoil with a leading-edge sweep angle of 34.6 deg, freestream Mach number of 0.75, and chord Reynolds numbers of 17 × 10(exp 6), 24 × 10(exp 6), and 30 × 10(exp 6) suggest that discrete roughness elements could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small-wavelength stationary crossflow disturbances (i.e., discrete roughness element) also suppresses the growth of most amplified traveling crossflow disturbances.

  20. DRE-Enhanced Swept-Wing Natural Laminar Flow at High Reynolds Numbers

    Science.gov (United States)

    Malik, Mujeeb; Liao, Wei; Li, Fe; Choudhari, Meelan

    2013-01-01

    Nonlinear parabolized stability equations and secondary instability analyses are used to provide a computational assessment of the potential use of the discrete roughness elements (DRE) technology for extending swept-wing natural laminar flow at chord Reynolds numbers relevant to transport aircraft. Computations performed for the boundary layer on a natural laminar flow airfoil with a leading-edge sweep angle of 34.6deg, free-stream Mach number of 0.75 and chord Reynolds numbers of 17 x 10(exp 6), 24 x 10(exp 6) and 30 x 10(exp 6) suggest that DRE could delay laminar-turbulent transition by about 20% when transition is caused by stationary crossflow disturbances. Computations show that the introduction of small wavelength stationary crossflow disturbances (i.e., DRE) also suppresses the growth of most amplified traveling crossflow disturbances.

  1. Accounting for Laminar Run & Trip Drag in Supersonic Cruise Performance Testing

    Science.gov (United States)

    Goodsell, Aga M.; Kennelly, Robert A.

    1999-01-01

    An improved laminar run and trip drag correction methodology for supersonic cruise performance testing was derived. This method required more careful analysis of the flow visualization images which revealed delayed transition particularly on the inboard upper surface, even for the largest trip disks. In addition, a new code was developed to estimate the laminar run correction. Once the data were corrected for laminar run, the correct approach to the analysis of the trip drag became evident. Although the data originally appeared confusing, the corrected data are consistent with previous results. Furthermore, the modified approach, which was described in this presentation, extends prior historical work by taking into account the delayed transition caused by the blunt leading edges.

  2. Proportional feedback control of laminar flow over a hemisphere

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jung Il [Dept. of Mechanical Engineering, Ajou University, Suwon (Korea, Republic of); Son, Dong Gun [Severe Accident and PHWR Safety Research Division, Korea Atomic Energy Research Institute (KAERI), Daejeon (Korea, Republic of)

    2016-08-15

    In the present study, we perform a proportional feedback control of laminar flow over a hemisphere at Re = 300 to reduce its lift fluctuations by attenuating the strength of the vortex shedding. As a control input, blowing/suction is distributed on the surface of hemisphere before the separation, and its strength is linearly proportional to the transverse velocity at a sensing location in the centerline of the wake. The sensing location is determined based on a correlation function between the lift force and the time derivative of sensing velocity. The optimal proportional gains for the proportional control are obtained for the sensing locations considered. The present control successfully attenuates the velocity fluctuations at the sensing location and three dimensional vertical structures in the wake, resulting in the reduction of lift fluctuations of hemisphere.

  3. Vortex Formation During Unsteady Boundary-Layer Separation

    Science.gov (United States)

    Das, Debopam; Arakeri, Jaywant H.

    1998-11-01

    Unsteady laminar boundary-layer separation is invariably accompanied by the formation of vortices. The aim of the present work is to study the vortex formation mechanism(s). An adverse pressure gradient causing a separation can be decomposed into a spatial component ( spatial variation of the velocity external to the boundary layer ) and a temporal component ( temporal variation of the external velocity ). Experiments were conducted in a piston driven 2-D water channel, where the spatial component could be be contolled by geometry and the temporal component by the piston motion. We present results for three divergent channel geometries. The piston motion consists of three phases: constant acceleration from start, contant velocity, and constant deceleration to stop. Depending on the geometry and piston motion we observe different types of unsteady separation and vortex formation.

  4. Versatile Sensor for Transition, Separation, and Shock Detection, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovation is a simple, robust, sensor array for the detection of laminar/turbulent transition location, areas of flowfield separation, and shock wave...

  5. Morphodynamic modeling of erodible laminar channels.

    Science.gov (United States)

    Devauchelle, Olivier; Josserand, Christophe; Lagrée, Pierre-Yves; Zaleski, Stéphane

    2007-11-01

    A two-dimensional model for the erosion generated by viscous free-surface flows, based on the shallow-water equations and the lubrication approximation, is presented. It has a family of self-similar solutions for straight erodible channels, with an aspect ratio that increases in time. It is also shown, through a simplified stability analysis, that a laminar river can generate various bar instabilities very similar to those observed in natural rivers. This theoretical similarity reflects the meandering and braiding tendencies of laminar rivers indicated by F. Métivier and P. Meunier [J. Hydrol. 27, 22 (2003)]. Finally, we propose a simple scenario for the transition between patterns observed in experimental erodible channels.

  6. Remediation of water pollution caused by pharmaceutical residues based on electrochemical separation and degradation technologies: a review.

    Science.gov (United States)

    Sirés, Ignasi; Brillas, Enric

    2012-04-01

    In the last years, the decontamination and disinfection of waters by means of direct or integrated electrochemical processes are being considered as a very appealing alternative due to the significant improvement of the electrode materials and the coupling with low-cost renewable energy sources. Many electrochemical technologies are currently available for the remediation of waters contaminated by refractory organic pollutants such as pharmaceutical micropollutants, whose presence in the environment has become a matter of major concern. Recent reviews have focused on the removal of pharmaceutical residues upon the application of other important methods like ozonation and advanced oxidation processes. Here, we present an overview on the electrochemical methods devised for the treatment of pharmaceutical residues from both, synthetic solutions and real pharmaceutical wastewaters. Electrochemical separation technologies such as membrane technologies, electrocoagulation and internal micro-electrolysis, which only isolate the pollutants from water, are firstly introduced. The fundamentals and experimental set-ups involved in technologies that allow the degradation of pharmaceuticals, like anodic oxidation, electro-oxidation with active chlorine, electro-Fenton, photoelectro-Fenton and photoelectrocatalysis among others, are further discussed. Progress on the promising solar photoelectro-Fenton process devised and further developed in our laboratory is especially highlighted and documented. The abatement of total organic carbon or reduction of chemical oxygen demand from contaminated waters allows the comparison between the different methods and materials. The routes for the degradation of the some pharmaceuticals are also presented. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Estructuras laminares en España

    Directory of Open Access Journals (Sweden)

    Coello de Portugal, Fray

    1968-02-01

    Full Text Available This article deals with three interesting thin shell structures that serve as roofs for churches in various parts of Spain. The excellent functional properties of these shells is worth noting as well as their spectacular aspect and relatively low cost, especially if their complex geometry and striking structural effectiveness are taken into account. The Portuguese architect Fray Coello provided the general pattern of the designs, and the firm Construcciones Laminares, S. L., was responsible for the supervision of the construction, the calculations, plans, details and the actual construction. This paper was submited to lASS, 1967, in Mexico.Se exponen aquí tres interesantes cubiertas laminares para respectivas iglesias situadas en diferentes puntos de la geografía hispana. Se han de resaltar sus magníficos resultados y comportamiento, así como la gran espectacularidad conseguida y su bajo costo relativo, sobre todo a la vista de la plasticidad formal y el dramatismo estructural de las soluciones adoptadas. El arquitecto Fray Coello de Portugal aportó las ideas generales de diseño, encargándose el proyecto, supervisión, cálculo, planos, detalles, e incluso la construcción en algunos casos, a Construcciones Laminares, S. L. Este trabajo fue presentado en la IASS-1967 de México.

  8. Understanding the neural control of ingestive behaviors: helping to separate cause from effect with dehydration-associated anorexia.

    Science.gov (United States)

    Watts, A G

    2000-06-01

    Eating and drinking are motivated behaviors that are made up of coordinated sets of neuroendocrine, autonomic, and behavioral motor events. Although the spinal cord, hindbrain, and hypothalamus contain the motor neurons and circuitry sufficient to maintain the reflex parts of these motor events, inputs from the telencephalon are required to furnish the behavioral components with a motivated (goal-directed) character. Each of these motor events derives from the complex interaction of a variety of sensory inputs with groups of neural networks whose components are distributed throughout the brain and collectively support motor expression and coordination. At a first approximation based on a variety of data, these networks can be divided into three groups: networks that stimulate, those that inhibit, and those that disinhibit motor functions. A fourth contributor is the circadian timing signal that originates in the hypothalamic suprachiasmatic nucleus and provides the temporal anchor for the expression of all behaviors. This article discusses the nature of these networks using neuroanatomical (tract-tracing and neuropeptide in situ hybridization), endocrine, and behavioral evidence from a variety of experimental models. A persistent problem when studying the control of food intake from a neural systems perspective has been the difficulty in separating those neuronal changes that result in hunger from those that are as a consequence of eating. To address this problem, dehydration-associated anorexia is presented as a particularly useful experimental model because it can be used to distinguish between neural mechanisms underlying anorexia and those changes that occur as a consequence of anorexia. The article concludes by highlighting the potential role of neuropeptidergic action in the operation of these networks, using forebrain neuropeptidergic innervation of the parabrachial nucleus as an example. Copyright 2000 Academic Press.

  9. NUMERICAL SIMULATION OF UJONG SEUDEUN LAND SEPARATION CAUSED BY THE 2004 INDIAN OCEAN TSUNAMI, ACEH-INDONESIA

    Directory of Open Access Journals (Sweden)

    Musa Al'ala

    2015-07-01

    Full Text Available The Aceh province in Indonesia, located around the Sumatra subduction area, was one of the worst hit areas with respect to damage from the impact of the 2004 Indian Ocean tsunami. A 9.15 Mw earthquake triggered the tsunami. One of the impacts was the disconnection of several areas from their mainland, thus creating new small islands. This happened around Ujong Seudeun village in Aceh Jaya District. Prior to the tsunami, the village had approximately 500 residents. However, after the tsunami, the area was severely eroded and a small strait had been inserted between the village and the Sumatra Island mainland. This study investigates the magnitude of the tsunami wave forces that separated the area to yield a newly deserted small island. This study was conducted by numerical simulations and by coupling the COMCOT (Cornell Multi-grid Coupled Tsunami Model and Delft3D models. These tools have specific advantages, namely, COMCOT’s linear modeling is based on a series of earthquake mechanisms and Delft3D uses non-linear morphological dynamic modeling. Their software includes the explicit leapfrog finite difference scheme (COMCOT and the non-linear shallow water equation (Delft3D. Bathymetry data fromnewly formed coastline and the small island’s shape were digitized using 2005 Quickbird Images. Results from this research reveal the estimated tsunami wave heights and forces that disconnected the small island of Ujong Seuden from the Sumatra Island mainland. These results can be used to further develop the COMCOT model to incorporate sediment modules.

  10. Design and fabrication of a micro fluidic circuit for the separation of micron sized particles

    CSIR Research Space (South Africa)

    Khumalo, F

    2009-07-01

    Full Text Available The development of a micro fluidic circuit for the separation of micro particles is being investigated. There are a wide range of available separation techniques such as acoustic, laminar flow, split flow, optical trapping and centrifugal forces...

  11. Numerical analysis of laminar forced convection in a spherical annulus

    International Nuclear Information System (INIS)

    Tuft, D.B.

    1980-01-01

    Calculations of steady laminar incompressible fluid-flow and heat transfer in a spherical annulus are presented. Steady pressures, temperatures, velocities, and heat transfer coefficients are calculated for an insulated outer sphere and a 0 0 C isothermal inner sphere with 50 0 C heated water flowing in the annulus. The inner sphere radius is 13.97 cm, the outer sphere radius is 16.83 cm and the radius ratio is 1.2. The transient axisymmetric equations of heat, mass, and momentum conservation are solved numerically in spherical coordinates. The transient solution is carried out in time until steady state is achieved. A variable mesh is used to improve resolution near the inner sphere where temperature and velocity gradients are steep. It is believed that this is the first fully two-dimensional analysis of forced flow in a spherical annulus. Local and bulk Nusselt numbers are presented for Reynolds numbers from 4.4 to 440. Computed bulk Nusselt numbers ranged from 2 to 50 and are compared to experimental results from the literature. Inlet flow jetting off the inner sphere and flow separation are predicted by the analysis. The location of wall jet separation was found to be a function of Reynolds number, indicating the location of separation depends upon the ratio of inertia to viscous forces. Wall jet separation has a pronounced effect on the distribution of local heat flux. The area between inlet and separation was found to be the most significant area for heat transfer. Radial distributions of azimuthal velocity and temperature are presented for various angles beginning at the inlet. Inner sphere pressure distribution is presented and the effect on flow separation is discussed

  12. Experimental Study of Cavitation in Laminar Flow

    OpenAIRE

    Croci , Kilian; Ravelet , Florent; ROBINET , Jean-Christophe; Danlos , Amélie

    2017-01-01

    An experimental setup has been especially developed in order to observe cavitation in laminar flows. Experiments have been carried out with a silicon oil of viscosity υ = 100cSt passing through a Venturi-type geometry with 18°/8° convergent/divergent angles respectively. The range of Reynolds numbers at the inlet section is between 350 and 1000. Two dynamic regimes are identified. They are characterized by two critical Reynolds numbers, induced by major hydrodynamic changes in the flow, in ad...

  13. Bifurcation in a buoyant horizontal laminar jet

    Science.gov (United States)

    Arakeri, Jaywant H.; Das, Debopam; Srinivasan, J.

    2000-06-01

    The trajectory of a laminar buoyant jet discharged horizontally has been studied. The experimental observations were based on the injection of pure water into a brine solution. Under certain conditions the jet has been found to undergo bifurcation. The bifurcation of the jet occurs in a limited domain of Grashof number and Reynolds number. The regions in which the bifurcation occurs has been mapped in the Reynolds number Grashof number plane. There are three regions where bifurcation does not occur. The various mechanisms that prevent bifurcation have been proposed.

  14. Flocculation kinetics and aggregate structure of kaolinite mixtures in laminar tube flow.

    Science.gov (United States)

    Vaezi G, Farid; Sanders, R Sean; Masliyah, Jacob H

    2011-03-01

    Flocculation is commonly used in various solid-liquid separation processes in chemical and mineral industries to separate desired products or to treat waste streams. This paper presents an experimental technique to study flocculation processes in laminar tube flow. This approach allows for more realistic estimation of the shear rate to which an aggregate is exposed, as compared to more complicated shear fields (e.g. stirred tanks). A direct sampling method is used to minimize the effect of sampling on the aggregate structure. A combination of aggregate settling velocity and image analysis was used to quantify the structure of the aggregate. Aggregate size, density, and fractal dimension were found to be the most important aggregate structural parameters. The two methods used to determine aggregate fractal dimension were in good agreement. The effects of advective flow through an aggregate's porous structure and transition-regime drag coefficient on the evaluation of aggregate density were considered. The technique was applied to investigate the flocculation kinetics and the evolution of the aggregate structure of kaolin particles with an anionic flocculant under conditions similar to those of oil sands fine tailings. Aggregates were formed using a well controlled two-stage aggregation process. Detailed statistical analysis was performed to investigate the establishment of dynamic equilibrium condition in terms of aggregate size and density evolution. An equilibrium steady state condition was obtained within 90 s of the start of flocculation; after which no further change in aggregate structure was observed. Although longer flocculation times inside the shear field could conceivably cause aggregate structure conformation, statistical analysis indicated that this did not occur for the studied conditions. The results show that the technique and experimental conditions employed here produce aggregates having a well-defined, reproducible structure. Copyright © 2011

  15. Numerical calculation of the main variables of the laminar flow around a circunferential square obstacle at the wall of a circular pipe

    International Nuclear Information System (INIS)

    Nogueira, A.C.R.

    1981-10-01

    The numerical calculation of the main variables of the laminar, incompressible, axissimmetric, steady flow around a circunferential square obstacle placed at the wall of a circular pipe, is done. The velocity profiles, the separating length and the shape of the separating streamline are compared with experimental available data and a good agreement is achieved. (E.G.) [pt

  16. Modified laminar flow biological safety cabinet.

    Science.gov (United States)

    McGarrity, G J; Coriell, L L

    1974-10-01

    Tests are reported on a modified laminar flow biological safety cabinet in which the return air plenum that conducts air from the work area to the high efficiency particulate air filters is under negative pressure. Freon gas released inside the cabinet could not be detected outside by a freon gas detection method capable of detecting 10(-6) cc/s. When T3 bacteriophage was aerosolized 5 cm outside the front opening in 11 tests, no phage could be detected inside the cabinet with the motor-filter unit in operation. An average of 2.8 x 10(5) plaque-forming units (PFU)/ft(3) (ca. 0.028 m(3)) were detected with the motor-filter unit not in operation, a penetration of 0.0%. Aerosolization 5 cm inside the cabinet yielded an average of 10 PFU/ft(3) outside the cabinet with the motor-filter unit in operation and an average of 4.1 x 10(5) PFU/ft(3) with the motor-filter unit not in operation, a penetration of 0.002%. These values are the same order of effectiveness as the positive-pressure laminar flow biological safety cabinets previously tested. The advantages of the negative-pressure return plenum design include: (i) assurance that if cracks or leaks develop in the plenum it will not lead to discharge of contaminated air into the laboratory; and (ii) the price is lower due to reduced manufacturing costs.

  17. Gliding swifts attain laminar flow over rough wings.

    Directory of Open Access Journals (Sweden)

    David Lentink

    Full Text Available Swifts are among the most aerodynamically refined gliding birds. However, the overlapping vanes and protruding shafts of their primary feathers make swift wings remarkably rough for their size. Wing roughness height is 1-2% of chord length on the upper surface--10,000 times rougher than sailplane wings. Sailplanes depend on extreme wing smoothness to increase the area of laminar flow on the wing surface and minimize drag for extended glides. To understand why the swift does not rely on smooth wings, we used a stethoscope to map laminar flow over preserved wings in a low-turbulence wind tunnel. By combining laminar area, lift, and drag measurements, we show that average area of laminar flow on swift wings is 69% (n = 3; std 13% of their total area during glides that maximize flight distance and duration--similar to high-performance sailplanes. Our aerodynamic analysis indicates that swifts attain laminar flow over their rough wings because their wing size is comparable to the distance the air travels (after a roughness-induced perturbation before it transitions from laminar to turbulent. To interpret the function of swift wing roughness, we simulated its effect on smooth model wings using physical models. This manipulation shows that laminar flow is reduced and drag increased at high speeds. At the speeds at which swifts cruise, however, swift-like roughness prolongs laminar flow and reduces drag. This feature gives small birds with rudimentary wings an edge during the evolution of glide performance.

  18. The Turbulent-Laminar Transition on the Rocket Surface During the Injection

    Directory of Open Access Journals (Sweden)

    I. I. Yurchenko

    2014-01-01

    Full Text Available The variety of turbulent-laminar transition criteria in such environments as the launch vehicle injection points to the essential influence of spherical nose roughness, which is included in one form or another in the critical Reynolds numbers for a lot of explorers of blunt bodies. Some of researchers of the reentry bodies have founded the correlation functions between the momentum thickness Reynolds number and Max number as the transition criteria.In this article we have considered results of flight tests carried out using launch vehicles to define boundary layer regime on the payload fairing surface. The measurements were carried out using specially designed complex of gages consisted of calorimeters, surface temperature gages, and pressure gages. The turbulent-laminar transition was defined in accordance with the sharp change of calorimeter readings and flow separation pressure gages indication.The universal criterion of turbulent-laminar transition has been identified for blunted payload fairings i.e. Reynolds number Reek based on the boundary layer edge parameters in the sonic point of the payload fairing spherical nose and surface roughness height k, which gives the best correlation of all data of flight experiment conducted to define turbulent-laminar transition in boundary layer. The criterion allows defining time margins when boundary layer regime is turbulent at Reek=20±14 existing on space head surfaces and at Reek=6±5 the boundary layer regime is totally laminar.It was defined that under conditions when there are jointly high background disturbances of free stream flux at operation of main launch vehicle engines and influence of the surface roughness the critical value of Reynolds number is an order-diminished value as compared to the values obtained in wind tunnels and in free flight.It was found that with decreasing of roughness influence in growing boundary layer the flow disturbances evolution wide apart the payload fairing

  19. Extinction of counterflow premixed laminar flames

    International Nuclear Information System (INIS)

    Smooke, M.D.; Giovangigli, V.

    1987-01-01

    Problems in combustion and heat and mass transfer often depend upon one or more physical/chemical parameters. In many cases the combustion scientist is interested in knowing how the solution will behave if one or more of these parameters is varied. For some parameter regimes the governing equations can produce multiple solutions and the branches of the solution curve are linked via singular points. It is at these singular points, however that the system exhibits special behavior. To be able to predict the solution structure in the neighborhood of these points, the authors employ a phase-space, pseudo arclength, continuation method that utilizes Newton-like iterations and adaptive gridding techniques. The authors apply the method in the solution of counterflow premixed laminar flames

  20. Laminar turbulent transition in heated free jet

    International Nuclear Information System (INIS)

    Krejci, L.; Marsik, F.; Nenicka, V.

    1998-01-01

    The evolution of heat and mass transfer in the initial region of a transitional plasma plume is investigated and discussed. The results show that these transport processes are controlled and limited by the plume shear layer instability. The process of laminar-turbulent transition is consecutively controlled by the plume core shear layer instability where interrelation of the effective thickness of the shear temperature and density layers play decisive role. When the absolute instability occurs the resonances in the jet and arc chamber must be taken into account. These processes are manifested in three events. Between the first and second phase, there is a maximum of arc heater exit average enthalpy. The other two thresholds occur at maximum and minimum stagnation heat flux from the plume core. It seems that these processes also influence the thermal energy production in the arc chamber cavity. (author)

  1. Laminar-Turbulent transition on Wind Turbines

    DEFF Research Database (Denmark)

    Martinez Hernandez, Gabriel Gerardo

    The present thesis deals with the study of the rotational effects on the laminar-turbulent transition on wind turbine blades. Linear stability theory is used to formulate the stability equations that include the effect of rotation. The mean flow required as an input to stability computations...... parametrized and adapted to an wind turbine rotor geometry. The blade is resolved in radial sections along which calculations are performed. The obtained mean flow is classified according to the parameters used on the rotating configuration, geometry and operational conditions. The stability diagrams have been...... to define the resultant wave magnitude and direction. The propagation of disturbances in the boundary layers in three dimensional flows is relatively a complicated phenomena. The report discusses the available methods and techniques used to predict the transition location. Some common wind turbine airfoils...

  2. Arc Voltage Fluctuation in DC Laminar and Turbulent Plasma Jets Generation

    International Nuclear Information System (INIS)

    Pan Wenxia; Meng Xian; Wu Chengkang

    2006-01-01

    Arc voltage fluctuations in a direct current (DC) non-transferred arc plasma generator are experimentally studied, in generating a jet in the laminar, transitional and turbulent regimes. The study is with a view toward elucidating the mechanism of the fluctuations and their relationship with the generating parameters, arc root movement and flow regimes. Results indicate that the existence of a 300 Hz alternating current (AC) component in the power supply ripples does not cause the transition of the laminar plasma jet into a turbulent state. There exists a high frequency fluctuation at 4 kHz in the turbulent jet regime. It may be related to the rapid movement of the anode attachment point of the arc

  3. Chemical kinetic model uncertainty minimization through laminar flame speed measurements

    Science.gov (United States)

    Park, Okjoo; Veloo, Peter S.; Sheen, David A.; Tao, Yujie; Egolfopoulos, Fokion N.; Wang, Hai

    2016-01-01

    Laminar flame speed measurements were carried for mixture of air with eight C3-4 hydrocarbons (propene, propane, 1,3-butadiene, 1-butene, 2-butene, iso-butene, n-butane, and iso-butane) at the room temperature and ambient pressure. Along with C1-2 hydrocarbon data reported in a recent study, the entire dataset was used to demonstrate how laminar flame speed data can be utilized to explore and minimize the uncertainties in a reaction model for foundation fuels. The USC Mech II kinetic model was chosen as a case study. The method of uncertainty minimization using polynomial chaos expansions (MUM-PCE) (D.A. Sheen and H. Wang, Combust. Flame 2011, 158, 2358–2374) was employed to constrain the model uncertainty for laminar flame speed predictions. Results demonstrate that a reaction model constrained only by the laminar flame speed values of methane/air flames notably reduces the uncertainty in the predictions of the laminar flame speeds of C3 and C4 alkanes, because the key chemical pathways of all of these flames are similar to each other. The uncertainty in model predictions for flames of unsaturated C3-4 hydrocarbons remain significant without considering fuel specific laminar flames speeds in the constraining target data set, because the secondary rate controlling reaction steps are different from those in the saturated alkanes. It is shown that the constraints provided by the laminar flame speeds of the foundation fuels could reduce notably the uncertainties in the predictions of laminar flame speeds of C4 alcohol/air mixtures. Furthermore, it is demonstrated that an accurate prediction of the laminar flame speed of a particular C4 alcohol/air mixture is better achieved through measurements for key molecular intermediates formed during the pyrolysis and oxidation of the parent fuel. PMID:27890938

  4. Early postnatal maternal separation causes alterations in the expression of β3-adrenergic receptor in rat adipose tissue suggesting long-term influence on obesity

    International Nuclear Information System (INIS)

    Miki, Takanori; Liu, Jun-Qian; Ohta, Ken-ichi; Suzuki, Shingo; Kusaka, Takashi; Warita, Katsuhiko; Yokoyama, Toshifumi; Jamal, Mostofa; Ueki, Masaaki; Yakura, Tomiko; Tamai, Motoki; Sumitani, Kazunori; Hosomi, Naohisa; Takeuchi, Yoshiki

    2013-01-01

    Highlights: •High-fat diet intake following maternal separation did not cause body weight gain. •However, levels of metabolism-related molecules in adipose tissue were altered. •Increased levels of prohibitin mRNA in white fat were observed. •Attenuated levels of β3-adrenergic receptor mRNA were observed in brown fat. •Such alterations in adipose tissue may contribute to obesity later in life. -- Abstract: The effects of early postnatal maternal deprivation on the biological characteristics of the adipose tissue later in life were investigated in the present study. Sprague–Dawley rats were classified as either maternal deprivation (MD) or mother-reared control (MRC) groups. MD was achieved by separating the rat pups from their mothers for 3 h each day during the 10–15 postnatal days. mRNA levels of mitochondrial uncoupling protein 1 (UCP-1), β3-adrenergic receptor (β3-AR), and prohibitin (PHB) in the brown and white adipose tissue were determined using real-time RT-PCR analysis. UCP-1, which is mediated through β3-AR, is closely involved in the energy metabolism and expenditure. PHB is highly expressed in the proliferating tissues/cells. At 10 weeks of age, the body weight of the MRC and MD rats was similar. However, the levels of the key molecules in the adipose tissue were substantially altered. There was a significant increase in the expression of PHB mRNA in the white adipose tissue, while the β3-AR mRNA expression decreased significantly, and the UCP-1 mRNA expression remained unchanged in the brown adipose tissue. Given that these molecules influence the mitochondrial metabolism, our study indicates that early postnatal maternal deprivation can influence the fate of adipose tissue proliferation, presumably leading to obesity later in life

  5. Early postnatal maternal separation causes alterations in the expression of β3-adrenergic receptor in rat adipose tissue suggesting long-term influence on obesity

    Energy Technology Data Exchange (ETDEWEB)

    Miki, Takanori, E-mail: mikit@med.kagawa-u.ac.jp [Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University (Japan); Liu, Jun-Qian; Ohta, Ken-ichi; Suzuki, Shingo [Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University (Japan); Kusaka, Takashi [Department of Pediatrics, Faculty of Medicine, Kagawa University (Japan); Warita, Katsuhiko [Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University (Japan); Yokoyama, Toshifumi [Department of Bioresource and Agrobiosciences, Graduate School of Science and Technology, Kobe University (Japan); Jamal, Mostofa [Department of Forensic Medicine, Faculty of Medicine, Kagawa University (Japan); Ueki, Masaaki [Department of Anesthesia, Nishiwaki Municipal Hospital (Japan); Yakura, Tomiko; Tamai, Motoki [Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University (Japan); Sumitani, Kazunori [Department of Medical Education, Faculty of Medicine, Kagawa University (Japan); Hosomi, Naohisa [Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical Sciences (Japan); Takeuchi, Yoshiki [Department of Anatomy and Neurobiology, Faculty of Medicine, Kagawa University (Japan)

    2013-12-06

    Highlights: •High-fat diet intake following maternal separation did not cause body weight gain. •However, levels of metabolism-related molecules in adipose tissue were altered. •Increased levels of prohibitin mRNA in white fat were observed. •Attenuated levels of β3-adrenergic receptor mRNA were observed in brown fat. •Such alterations in adipose tissue may contribute to obesity later in life. -- Abstract: The effects of early postnatal maternal deprivation on the biological characteristics of the adipose tissue later in life were investigated in the present study. Sprague–Dawley rats were classified as either maternal deprivation (MD) or mother-reared control (MRC) groups. MD was achieved by separating the rat pups from their mothers for 3 h each day during the 10–15 postnatal days. mRNA levels of mitochondrial uncoupling protein 1 (UCP-1), β3-adrenergic receptor (β3-AR), and prohibitin (PHB) in the brown and white adipose tissue were determined using real-time RT-PCR analysis. UCP-1, which is mediated through β3-AR, is closely involved in the energy metabolism and expenditure. PHB is highly expressed in the proliferating tissues/cells. At 10 weeks of age, the body weight of the MRC and MD rats was similar. However, the levels of the key molecules in the adipose tissue were substantially altered. There was a significant increase in the expression of PHB mRNA in the white adipose tissue, while the β3-AR mRNA expression decreased significantly, and the UCP-1 mRNA expression remained unchanged in the brown adipose tissue. Given that these molecules influence the mitochondrial metabolism, our study indicates that early postnatal maternal deprivation can influence the fate of adipose tissue proliferation, presumably leading to obesity later in life.

  6. Heat transfer of laminar mixed convection of liquid

    CERN Document Server

    Shang, De-Yi

    2016-01-01

    This book presents a new algorithm to calculate fluid flow and heat transfer of laminar mixed convection. It provides step-by-step tutorial help to learn quickly how to set up the theoretical and numerical models of laminar mixed convection, to consider the variable physical properties of fluids, to obtain the system of numerical solutions, to create a series of formalization equations for the convection heat transfer by using a curve-fitting approach combined with theoretical analysis and derivation. It presents the governing ordinary differential equations of laminar mixed convection, equivalently transformed by an innovative similarity transformation with the description of the related transformation process. A system of numerical calculations of the governing ordinary differential equations is presented for the water laminar mixed convection. A polynomial model is induced for convenient and reliable treatment of variable physical properties of liquids. The developed formalization equations of mixed convec...

  7. Response to acoustic forcing of laminar coflow jet diffusion flames

    KAUST Repository

    Chrystie, Robin; Chung, Suk-Ho

    2014-01-01

    Toward the goal of understanding and controlling instability in combustion systems, we present a fundamental characterization of the interaction of the buoyancy-induced instability in flickering flames with forced excitation of fuel supply. Laminar

  8. A New Approach to Laminar Flowmeters

    Directory of Open Access Journals (Sweden)

    Alvaro Deibe

    2010-11-01

    Full Text Available After studying the performance and characteristics of actual laminar flowmeters a new disposition for this type of sensors is proposed in such a way that the measurement errors introduced by the intrinsic nature of the device can be minimized. The preliminary study shows that the developing entry region introduces non-linearity effects in all these devices. These effects bring about not only errors, but also a change in the slope of the linear calibration respect of the Poiseuille relation. After a subsequent analysis on how these non-linearity errors can be reduced, a new disposition of this type of flowmeters is introduced. This device makes used of flow elements having pressure taps at three locations along its length and connected to three isolated chambers. In this way, the static pressure can be measured at three locations and contributed to by the pressure taps at the level of each chamber. Thus the linearization error is reduced with an additional advantage of producing a reduced pressure drop.

  9. Laminar flow resistance in short microtubes

    Energy Technology Data Exchange (ETDEWEB)

    Phares, D.J. [Texas A and M University, College Station, TX (United States). Dept. of Mechanical Engineering; Smedley, G.T.; Zhou, J. [Glaukos Corp., Laguna Hills, CA (United States). Dept. of Research and Development

    2005-06-01

    We have measured the pressure drop for the flow of liquid through a series of short microtubes ranging from 80 to 150 {mu}m in diameter with aspect ratios between L/D = 2 and L/D = 5. These dimensions were selected to resemble lumens of implantable microstents that are under consideration for the treatment of glaucoma. For physiologically relevant pressure drops and flow rates, we have determined that a fully-developed laminar pipe flow may be assumed throughout the microtube when (L/D) > 0.20Re, where Re is the Reynolds number based on the diameter, D, and L is the length of the tube. We have examined flow rates between 0.1 and 10 {mu}L/s, corresponding to Reynolds numbers between 1 and 150. For smooth microtubes, no difference from macroscopic flow is observed for the tube sizes considered. However, flow resistance is found to be sensitive to the relative surface roughness of the tube walls. (author)

  10. Steady laminar flow of fractal fluids

    Energy Technology Data Exchange (ETDEWEB)

    Balankin, Alexander S., E-mail: abalankin@ipn.mx [Grupo Mecánica Fractal, ESIME, Instituto Politécnico Nacional, México D.F., 07738 (Mexico); Mena, Baltasar [Laboratorio de Ingeniería y Procesos Costeros, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Sisal, Yucatán, 97355 (Mexico); Susarrey, Orlando; Samayoa, Didier [Grupo Mecánica Fractal, ESIME, Instituto Politécnico Nacional, México D.F., 07738 (Mexico)

    2017-02-12

    We study laminar flow of a fractal fluid in a cylindrical tube. A flow of the fractal fluid is mapped into a homogeneous flow in a fractional dimensional space with metric induced by the fractal topology. The equations of motion for an incompressible Stokes flow of the Newtonian fractal fluid are derived. It is found that the radial distribution for the velocity in a steady Poiseuille flow of a fractal fluid is governed by the fractal metric of the flow, whereas the pressure distribution along the flow direction depends on the fractal topology of flow, as well as on the fractal metric. The radial distribution of the fractal fluid velocity in a steady Couette flow between two concentric cylinders is also derived. - Highlights: • Equations of Stokes flow of Newtonian fractal fluid are derived. • Pressure distribution in the Newtonian fractal fluid is derived. • Velocity distribution in Poiseuille flow of fractal fluid is found. • Velocity distribution in a steady Couette flow is established.

  11. Laminar nanofluid flow in microheat-sinks

    Energy Technology Data Exchange (ETDEWEB)

    Koo, J.; Kleinstreuer, C. [North Carolina State University, Raleigh, NC (United States). Dept. of Mechanical and Aerospace Engineering

    2005-06-01

    In response to the ever increasing demand for smaller and lighter high-performance cooling devices, steady laminar liquid nanofluid flow in microchannels is simulated and analyzed. Considering two types of nanofluids, i.e., copper-oxide nanospheres at low volume concentrations in water or ethylene glycol, the conjugated heat transfer problem for microheat-sinks has been numerically solved. Employing new models for the effective thermal conductivity and dynamic viscosity of nanofluids, the impact of nanoparticle concentrations in these two mixture flows on the microchannel pressure gradients, temperature profiles and Nusselt numbers are computed, in light of aspect ratio, viscous dissipation, and enhanced temperature effects. Based on these results, the following can be recommended for microheat-sink performance improvements: Use of large high-Prandtl number carrier fluids, nanoparticles at high volume concentrations of about 4% with elevated thermal conductivities and dielectric constants very close to that of the carrier fluid, microchannels with high aspect ratios, and treated channel walls to avoid nanoparticle accumulation. (Author)

  12. Review of hybrid laminar flow control systems

    Science.gov (United States)

    Krishnan, K. S. G.; Bertram, O.; Seibel, O.

    2017-08-01

    The aeronautic community always strived for fuel efficient aircraft and presently, the need for ecofriendly aircraft is even more, especially with the tremendous growth of air traffic and growing environmental concerns. Some of the important drivers for such interests include high fuel prices, less emissions requirements, need for more environment friendly aircraft to lessen the global warming effects. Hybrid laminar flow control (HLFC) technology is promising and offers possibility to achieve these goals. This technology was researched for decades for its application in transport aircraft, and it has achieved a new level of maturity towards integration and safety and maintenance aspects. This paper aims to give an overview of HLFC systems research and associated flight tests in the past years both in the US and in Europe. The review makes it possible to distinguish between the successful approaches and the less successful or outdated approaches in HLFC research. Furthermore, the technology status shall try to produce first estimations regarding the mass, power consumption and performance of HLFC systems as well as estimations regarding maintenance requirements and possible subsystem definitions.

  13. Full-thickness thoracic laminar erosion after posterior spinal fusion associated with late-presenting infection.

    Science.gov (United States)

    Tribus, Clifford B; Garvey, Kathleen E

    2003-05-15

    A case report describes unilateral complete laminar erosion of the caudal thoracic spine and late-presenting infection in a patient 10 years after anteroposterior reconstruction for scoliosis. To present an unusual but significant complication that may occur after implantation of spinal instrumentation. The reported patient presented with a deep infection and persistent back pain 10 years after successful anteroposterior reconstruction for adult idiopathic scoliosis. Delayed onset infections after implantation of spinal instrumentation are infrequent, yet when present, often require hardware removal. The case of a 51-year-old woman who underwent irrigation and debridement for a late-presenting infection and removal of posterior hardware 10 years after her index procedure is presented. Interoperatively, it was noted that full-thickness laminar erosion was present from T4 to T12. The patient was taken to the operating room for wound irrigation, debridement, and hardware removal. It was discovered that a Cotrel-Dubousset rod placed on the convexity of the curve had completely eroded through the lamina of T7-T12. Infectious material was found along the entire length of both the convex and concave Cotrel-Dubousset rods. Intraoperative cultures grew Staphylococcus epidermidis and Propionibacterium acnes. Intravenous and oral antibiotics were administered, resulting in resolution of the infection and preoperative pain. The exact role of late-presenting infection with regard to the laminar erosion and rod migration seen in this case remains to be elucidated. However, the authors believe the primary cause of bony erosion was mechanical in origin. Regardless, most spine surgeons will treat many patients who have had posterior spinal implants and will perform hardware removal on a significant number of these patients during their careers. A full-thickness laminar erosion exposes the spinal cord to traumatic injury during hardware removal and debridement. This case is

  14. Copy number variation of two separate regulatory regions upstream of SOX9 causes isolated 46,XY or 46,XX disorder of sex development.

    Science.gov (United States)

    Kim, Gwang-Jin; Sock, Elisabeth; Buchberger, Astrid; Just, Walter; Denzer, Friederike; Hoepffner, Wolfgang; German, James; Cole, Trevor; Mann, Jillian; Seguin, John H; Zipf, William; Costigan, Colm; Schmiady, Hardi; Rostásy, Moritz; Kramer, Mildred; Kaltenbach, Simon; Rösler, Bernd; Georg, Ina; Troppmann, Elke; Teichmann, Anne-Christin; Salfelder, Anika; Widholz, Sebastian A; Wieacker, Peter; Hiort, Olaf; Camerino, Giovanna; Radi, Orietta; Wegner, Michael; Arnold, Hans-Henning; Scherer, Gerd

    2015-04-01

    SOX9 mutations cause the skeletal malformation syndrome campomelic dysplasia in combination with XY sex reversal. Studies in mice indicate that SOX9 acts as a testis-inducing transcription factor downstream of SRY, triggering Sertoli cell and testis differentiation. An SRY-dependent testis-specific enhancer for Sox9 has been identified only in mice. A previous study has implicated copy number variations (CNVs) of a 78 kb region 517-595 kb upstream of SOX9 in the aetiology of both 46,XY and 46,XX disorders of sex development (DSD). We wanted to better define this region for both disorders. By CNV analysis, we identified SOX9 upstream duplications in three cases of SRY-negative 46,XX DSD, which together with previously reported duplications define a 68 kb region, 516-584 kb upstream of SOX9, designated XXSR (XX sex reversal region). More importantly, we identified heterozygous deletions in four families with SRY-positive 46,XY DSD without skeletal phenotype, which define a 32.5 kb interval 607.1-639.6 kb upstream of SOX9, designated XY sex reversal region (XYSR). To localise the suspected testis-specific enhancer, XYSR subfragments were tested in cell transfection and transgenic experiments. While transgenic experiments remained inconclusive, a 1.9 kb SRY-responsive subfragment drove expression specifically in Sertoli-like cells. Our results indicate that isolated 46,XY and 46,XX DSD can be assigned to two separate regulatory regions, XYSR and XXSR, far upstream of SOX9. The 1.9 kb SRY-responsive subfragment from the XYSR might constitute the core of the Sertoli-cell enhancer of human SOX9, representing the so far missing link in the genetic cascade of male sex determination. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  15. A combined PHREEQC-2/parallel fracture model for the simulation of laminar/non-laminar flow and contaminant transport with reactions

    Science.gov (United States)

    Masciopinto, Costantino; Volpe, Angela; Palmiotta, Domenico; Cherubini, Claudia

    2010-09-01

    A combination of a parallel fracture model with the PHREEQC-2 geochemical model was developed to simulate sequential flow and chemical transport with reactions in fractured media where both laminar and turbulent flows occur. The integration of non-laminar flow resistances in one model produced relevant effects on water flow velocities, thus improving model prediction capabilities on contaminant transport. The proposed conceptual model consists of 3D rock-blocks, separated by horizontal bedding plane fractures with variable apertures. Particle tracking solved the transport equations for conservative compounds and provided input for PHREEQC-2. For each cluster of contaminant pathways, PHREEQC-2 determined the concentration for mass-transfer, sorption/desorption, ion exchange, mineral dissolution/precipitation and biodegradation, under kinetically controlled reactive processes of equilibrated chemical species. Field tests have been performed for the code verification. As an example, the combined model has been applied to a contaminated fractured aquifer of southern Italy in order to simulate the phenol transport. The code correctly fitted the field available data and also predicted a possible rapid depletion of phenols as a result of an increased biodegradation rate induced by a simulated artificial injection of nitrates, upgradient to the sources.

  16. Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. I. Theory

    Energy Technology Data Exchange (ETDEWEB)

    Rogachevskii, Igor; Kleeorin, Nathan [Department of Mechanical Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel); Ruchayskiy, Oleg [Discovery Center, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Boyarsky, Alexey [Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, Niels Bohrweg 2, 2333 CA Leiden (Netherlands); Fröhlich, Jürg [Institute of Theoretical Physics, ETH Hönggerberg, CH-8093 Zurich (Switzerland); Brandenburg, Axel; Schober, Jennifer, E-mail: gary@bgu.ac.il [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

    2017-09-10

    The magnetohydrodynamic (MHD) description of plasmas with relativistic particles necessarily includes an additional new field, the chiral chemical potential associated with the axial charge (i.e., the number difference between right- and left-handed relativistic fermions). This chiral chemical potential gives rise to a contribution to the electric current density of the plasma ( chiral magnetic effect ). We present a self-consistent treatment of the chiral MHD equations , which include the back-reaction of the magnetic field on a chiral chemical potential and its interaction with the plasma velocity field. A number of novel phenomena are exhibited. First, we show that the chiral magnetic effect decreases the frequency of the Alfvén wave for incompressible flows, increases the frequencies of the Alfvén wave and of the fast magnetosonic wave for compressible flows, and decreases the frequency of the slow magnetosonic wave. Second, we show that, in addition to the well-known laminar chiral dynamo effect, which is not related to fluid motions, there is a dynamo caused by the joint action of velocity shear and chiral magnetic effect. In the presence of turbulence with vanishing mean kinetic helicity, the derived mean-field chiral MHD equations describe turbulent large-scale dynamos caused by the chiral alpha effect, which is dominant for large fluid and magnetic Reynolds numbers. The chiral alpha effect is due to an interaction of the chiral magnetic effect and fluctuations of the small-scale current produced by tangling magnetic fluctuations (which are generated by tangling of the large-scale magnetic field by sheared velocity fluctuations). These dynamo effects may have interesting consequences in the dynamics of the early universe, neutron stars, and the quark–gluon plasma.

  17. Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. I. Theory

    International Nuclear Information System (INIS)

    Rogachevskii, Igor; Kleeorin, Nathan; Ruchayskiy, Oleg; Boyarsky, Alexey; Fröhlich, Jürg; Brandenburg, Axel; Schober, Jennifer

    2017-01-01

    The magnetohydrodynamic (MHD) description of plasmas with relativistic particles necessarily includes an additional new field, the chiral chemical potential associated with the axial charge (i.e., the number difference between right- and left-handed relativistic fermions). This chiral chemical potential gives rise to a contribution to the electric current density of the plasma ( chiral magnetic effect ). We present a self-consistent treatment of the chiral MHD equations , which include the back-reaction of the magnetic field on a chiral chemical potential and its interaction with the plasma velocity field. A number of novel phenomena are exhibited. First, we show that the chiral magnetic effect decreases the frequency of the Alfvén wave for incompressible flows, increases the frequencies of the Alfvén wave and of the fast magnetosonic wave for compressible flows, and decreases the frequency of the slow magnetosonic wave. Second, we show that, in addition to the well-known laminar chiral dynamo effect, which is not related to fluid motions, there is a dynamo caused by the joint action of velocity shear and chiral magnetic effect. In the presence of turbulence with vanishing mean kinetic helicity, the derived mean-field chiral MHD equations describe turbulent large-scale dynamos caused by the chiral alpha effect, which is dominant for large fluid and magnetic Reynolds numbers. The chiral alpha effect is due to an interaction of the chiral magnetic effect and fluctuations of the small-scale current produced by tangling magnetic fluctuations (which are generated by tangling of the large-scale magnetic field by sheared velocity fluctuations). These dynamo effects may have interesting consequences in the dynamics of the early universe, neutron stars, and the quark–gluon plasma.

  18. An Investigation of Parallel Post-Laminar Flow through Coarse Granular Porous Media with the Wilkins Equation

    Directory of Open Access Journals (Sweden)

    Ashes Banerjee

    2018-02-01

    Full Text Available Behaviour of flow resistance with velocity is still undefined for post-laminar flow through coarse granular media. This can cause considerable errors during flow measurements in situations like rock fill dams, water filters, pumping wells, oil and gas exploration, and so on. Keeping the non-deviating nature of Wilkins coefficients with the hydraulic radius of media in mind, the present study further explores their behaviour to independently varying media size and porosity, subjected to parallel post-laminar flow through granular media. Furthermore, an attempt is made to simulate the post-laminar flow conditions with the help of a Computational Fluid Dynamic (CFD Model in ANSYS FLUENT, since conducting large-scale experiments are often costly and time-consuming. The model output and the experimental results are found to be in good agreement. Percentage deviations between the experimental and numerical results are found to be in the considerable range. Furthermore, the simulation results are statistically validated with the experimental results using the standard ‘Z-test’. The output from the model advocates the importance and applicability of CFD modelling in understanding post-laminar flow through granular media.

  19. Basal electric and magnetic fields of celestial bodies come from positive-negative charge separation caused by gravitation of quasi-Casimir pressure in weak interaction

    Science.gov (United States)

    Chen, Shao-Guang

    According to f =d(mv)/dt=m(dv/dt)+ v(dm/dt), a same gravitational formula had been de-duced from the variance in physical mass of QFT and from the variance in mass of inductive energy-transfer of GR respectively: f QF T = f GR = -G (mM/r2 )((r/r)+(v/c)) when their interaction-constants are all taken the experimental values (H05-0029-08, E15-0039-08). f QF T is the quasi-Casimir pressure. f GR is equivalent to Einstein's equation, then more easy to solve it. The hypothesis of the equivalent principle is not used in f QF T , but required by f GR . The predictions of f QF T and f GR are identical except that f QF T has quantum effects but f GR has not and f GR has Lense-Thirring effect but f QF T has not. The quantum effects of gravitation had been verified by Nesvizhevsky et al with the ultracold neutrons falling in the earth's gravitational field in 2002. Yet Lense-Thirring effect had not been measured by GP-B. It shows that f QF T is essential but f GR is phenomenological. The macro-f QF T is the statistic average pressure collided by net virtual neutrinos ν 0 flux (after self-offset in opposite directions) and in direct proportion to the mass. But micro-f QF T is in direct proportion to the scattering section. The electric mass (in inverse proportion to de Broglie wavelength λ) far less than nucleonic mass and the electric scattering section (in direct proportion to λ2 ) far large than that of nucleon, then the net ν 0 flux pressure exerted to electron far large than that to nucleon and the electric displacement far large than that of nucleon, it causes the gravitational polarization of positive-negative charge center separation. Because the gravity far less than the electromagnetic binding force, in atoms the gravitational polarization only produces a little separation. But the net ν 0 flux can press a part freedom electrons in plasma of ionosphere into the earth's surface, the static electric force of redundant positive ions prevents electrons from further

  20. Soot Formation in Freely-Propagating Laminar Premixed Flames

    Science.gov (United States)

    Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

    1997-01-01

    Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

  1. Computational Analysis of the G-III Laminar Flow Glove

    Science.gov (United States)

    Malik, Mujeeb R.; Liao, Wei; Lee-Rausch, Elizabeth M.; Li, Fei; Choudhari, Meelan M.; Chang, Chau-Lyan

    2011-01-01

    Under NASA's Environmentally Responsible Aviation Project, flight experiments are planned with the primary objective of demonstrating the Discrete Roughness Elements (DRE) technology for passive laminar flow control at chord Reynolds numbers relevant to transport aircraft. In this paper, we present a preliminary computational assessment of the Gulfstream-III (G-III) aircraft wing-glove designed to attain natural laminar flow for the leading-edge sweep angle of 34.6deg. Analysis for a flight Mach number of 0.75 shows that it should be possible to achieve natural laminar flow for twice the transition Reynolds number ever achieved at this sweep angle. However, the wing-glove needs to be redesigned to effectively demonstrate passive laminar flow control using DREs. As a by-product of the computational assessment, effect of surface curvature on stationary crossflow disturbances is found to be strongly stabilizing for the current design, and it is suggested that convex surface curvature could be used as a control parameter for natural laminar flow design, provided transition occurs via stationary crossflow disturbances.

  2. Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces

    International Nuclear Information System (INIS)

    Brauner, N.; Rovinsky, J.; Maron, D.M.

    1995-01-01

    The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the 'flow monograms' describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the 'interface monograms', whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system 'operational monogram'. The 'operational monogram' enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop

  3. Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Brauner, N.; Rovinsky, J.; Maron, D.M. [Tel-Aviv Univ. (Israel)

    1995-09-01

    The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the `flow monograms` describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the `interface monograms`, whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system `operational monogram`. The `operational monogram` enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop.

  4. Analytic solutions to linear, time-dependent fission product deposition models for isothermal laminar, slug, or multiregion flow conditions

    International Nuclear Information System (INIS)

    Durkee, J.W. Jr.

    1983-01-01

    The time-dependent convective-diffusion equation with radioactive decay is solved analytically in axisymmetric cylindrical geometry for laminar and slug velocity profiles under isothermal conditions. Concentration dependent diffusion is neglected. The laminar flow solution is derived using the method of separation of variables and Frobenius' technique for constructing a series expansion about a regular singular point. The slug flow multiregion solution is obtained using the method of separation of variables. The Davidon Variable Metric Minimization algorithm is used to compute the coupling coefficients. These solutions, which describe the transport of fission products in a flowing stream, are then used to determine the concentration of radioactive material deposited on a conduit wall using a standard mass transfer model. Fission product deposition measurements for five diffusion tubes in a Fort St. Vrain High-Temperature Gas-Cooled reactor plateout probe are analyzed. Using single region slug and laminar models, the wall mass transfer coefficients, diffusion coefficients, and inlet concentrations are determined using least squares analysis. The diffusion coefficients and inlet concentrations are consistent between tubes. The derived diffusion coefficients and wall mass transfer coefficients are in relative agreement with known literature values

  5. Three-dimensional numerical study of heat transfer enhancement in separated flows

    Science.gov (United States)

    Kumar, Saurav; Vengadesan, S.

    2017-11-01

    The flow separation appears in a wide range of heat transfer applications and causes poor heat transfer performance. It motivates the study of heat transfer enhancement in laminar as well as turbulent flows over a backward facing step by means of an adiabatic fin mounted on the top wall. Recently, we have studied steady, 2-D numerical simulations in laminar flow and investigated the effect of fin length, location, and orientation. It revealed that the addition of fin causes enhancement of heat transfer and it is very effective to control the flow and thermal behavior. The fin is most effective and sensitive when it is placed exactly above the step. A slight displacement of the fin in upstream of the step causes the complete change of flow and thermal behavior. Based on the obtained 2-D results it is interesting to investigate the side wall effect in three-dimensional simulations. The comparison of two-dimensional and three-dimensional numerical simulations with the available experimental results will be presented. Special attention has to be given to capture unsteadiness in the flow and thermal field.

  6. Entropy Generation in Steady Laminar Boundary Layers with Pressure Gradients

    Directory of Open Access Journals (Sweden)

    Donald M. McEligot

    2014-07-01

    Full Text Available In an earlier paper in Entropy [1] we hypothesized that the entropy generation rate is the driving force for boundary layer transition from laminar to turbulent flow. Subsequently, with our colleagues we have examined the prediction of entropy generation during such transitions [2,3]. We found that reasonable predictions for engineering purposes could be obtained for flows with negligible streamwise pressure gradients by adapting the linear combination model of Emmons [4]. A question then arises—will the Emmons approach be useful for boundary layer transition with significant streamwise pressure gradients as by Nolan and Zaki [5]. In our implementation the intermittency is calculated by comparison to skin friction correlations for laminar and turbulent boundary layers and is then applied with comparable correlations for the energy dissipation coefficient (i.e., non-dimensional integral entropy generation rate. In the case of negligible pressure gradients the Blasius theory provides the necessary laminar correlations.

  7. Cortical laminar necrosis in brain infarcts: chronological changes on MRI

    Energy Technology Data Exchange (ETDEWEB)

    Komiyama, M. [Department of Neurosurgery, Osaka City General Hospital, 2-13-22, Miyakojima-Hondouri, Miyakojima, Osaka 534 (Japan); Nishikawa, M. [Department of Neurosurgery, Osaka City General Hospital, 2-13-22, Miyakojima-Hondouri, Miyakojima, Osaka 534 (Japan); Yasui, T. [Department of Neurosurgery, Osaka City General Hospital, 2-13-22, Miyakojima-Hondouri, Miyakojima, Osaka 534 (Japan)

    1997-07-10

    We studied the MRI characteristics of cortical laminar necrosis in ischaemic stroke. We reviewed 13 patients with cortical laminar high signal on T1-weighted images to analyse the chronological changes in signal intensity and contrast enhancement. High-density cortical lesions began to appear on T1-weighted images about 2 weeks after the ictus. At 1-2 months they were prominent. They began to fade from 3 months but could be seen up to 11 months. These cortical lesions showed isointensity or high intensity on T2-weighted images and did not show low intensity at any stage. Contrast enhancement of the laminar lesions was prominent at 1-2 months and became less apparent from 3 months, but could be seen up to 8 months. (orig.). With 6 figs., 1 tab.

  8. Optimization of recirculating laminar air flow in operating room air conditioning systems

    Directory of Open Access Journals (Sweden)

    Enver Yalcin

    2016-04-01

    Full Text Available The laminar flow air-conditioning system with 100% fresh air is used in almost all operating rooms without discrimination in Turkey. The laminar flow device which is working with 100% fresh air should be absolutely used in Type 1A operating rooms. However, there is not mandatory to use of 100% fresh air for Type 1B defined as places performed simpler operation. Compared with recirculating laminar flow, energy needs of the laminar flow with 100 % fresh air has been emerged about 40% more than re-circulated air flow. Therefore, when a recirculating laminar flow device is operated instead of laminar flow system with 100% fresh air in the Type 1B operating room, annual energy consumption will be reduced. In this study, in an operating room with recirculating laminar flow, optimal conditions have been investigated in order to obtain laminar flow form by analyzing velocity distributions at various supply velocities by using computational fluid dynamics method (CFD.

  9. Laminar shear stress inhibits endothelial cell metabolism via KLF2-mediated repression of PFKFB3

    NARCIS (Netherlands)

    Doddaballapur, Anuradha; Michalik, Katharina M.; Manavski, Yosif; Lucas, Tina; Houtkooper, Riekelt H.; You, Xintian; Chen, Wei; Zeiher, Andreas M.; Potente, Michael; Dimmeler, Stefanie; Boon, Reinier A.

    2015-01-01

    Cellular metabolism was recently shown to regulate endothelial cell phenotype profoundly. Whether the atheroprotective biomechanical stimulus elicited by laminar shear stress modulates endothelial cell metabolism is not known. Here, we show that laminar flow exposure reduced glucose uptake and

  10. Thermal development of the laminar flow of a Bingham fluid between two plane plates with viscous dissipation

    Energy Technology Data Exchange (ETDEWEB)

    Boualit, A.; Boualit, S. [Unite de recherche appliquee en energies renouvelables, Ghardaia (Algeria); Zeraibi, N. [Universite de Boumerdes, Faculte des hydrocarbures dept. Transport et equipement, Boumerdes (Algeria); Amoura, M. [Universite des Sciences et de la Technologie Houari Boumedienne, Faculte de Physique, Dept. Energetique, Alger (Algeria)

    2011-01-15

    The thermal development of the hydrodynamically developing laminar flow of a viscoplastic fluid (fluid of Bingham) between two plane plates maintained at a constant temperature has been studied numerically. This analysis has shown the effect caused by inertia and the rheological behaviour of the fluid on the velocity, pressure and temperature fields. The effects of Bingham and Peclet numbers on the Nusselt values with the inclusion of viscous dissipation are also discussed. (authors)

  11. Particle migration in laminar shear fields

    NARCIS (Netherlands)

    Schroën, Karin; Dinther, van Anna; Stockmann, Regine

    2017-01-01

    Particles and droplets of micrometre scale are present in many industrial products and processes, where they can be either part of the product (e.g. emulsion droplets), need to be separated in order to be further utilised in product formulations (e.g. starch particles of specific size or oil from

  12. Effects of preheated combustion air on laminar coflow diffusion flames under normal and microgravity conditions

    Science.gov (United States)

    Ghaderi Yeganeh, Mohammad

    Global energy consumption has been increasing around the world, owing to the rapid growth of industrialization and improvements in the standard of living. As a result, more carbon dioxide and nitrogen oxide are being released into the environment. Therefore, techniques for achieving combustion at reduced carbon dioxide and nitric oxide emission levels have drawn increased attention. Combustion with a highly preheated air and low-oxygen concentration has been shown to provide significant energy savings, reduce pollution and equipment size, and uniform thermal characteristics within the combustion chamber. However, the fundamental understanding of this technique is limited. The motivation of the present study is to identify the effects of preheated combustion air on laminar coflow diffusion flames. Combustion characteristics of laminar coflow diffusion flames are evaluated for the effects of preheated combustion air temperature under normal and low-gravity conditions. Experimental measurements are conducted using direct flame photography, particle image velocimetry (PIV) and optical emission spectroscopy diagnostics. Laminar coflow diffusion flames are examined under four experimental conditions: normal-temperature/normal-gravity (case I), preheated-temperature/normal gravity (case II), normal-temperature/low-gravity (case III), and preheated-temperature/low-gravity (case IV). Comparisons between these four cases yield significant insights. In our studies, increasing the combustion air temperature by 400 K (from 300 K to 700 K), causes a 37.1% reduction in the flame length and about a 25% increase in peak flame temperature. The results also show that a 400 K increase in the preheated air temperature increases CH concentration of the flame by about 83.3% (CH is a marker for the rate of chemical reaction), and also increases the C2 concentration by about 60% (C2 is a marker for the soot precursor). It can therefore be concluded that preheating the combustion air

  13. A generalized relationship for swirl decay in laminar pipe flow

    Indian Academy of Sciences (India)

    Swirling flow is of great importance in heat and mass transfer enhancements and in flow measurements. In this study, laminar swirling flow in a straight pipe was considered. Steady three-dimensional axisymmetric Navier–Stokes equations were solved numerically using a control volume approach. The swirl number ...

  14. A generalized relationship for swirl decay in laminar pipe flow

    Indian Academy of Sciences (India)

    MS received 24 July 2008; revised 28 January 2010; accepted 1 February 2010. Abstract. Swirling flow is of great importance in heat and mass transfer enhance- ments and in flow measurements. In this study, laminar swirling flow in a straight pipe was considered. Steady three-dimensional axisymmetric Navier–Stokes ...

  15. Energy fluxes and spectra for turbulent and laminar flows

    KAUST Repository

    Verma, Mahendra K.; Kumar, Abhishek; Kumar, Praveen; Barman, Satyajit; Chatterjee, Anando G.; Samtaney, Ravi

    2017-01-01

    spectrum $E(k)$ and energy flux $\\Pi(k)$ using spectral simulations on grids up to $4096^3$, and show consistency between the numerical results and predictions by the aforementioned models. We also construct a model for laminar flows that predicts $E(k

  16. Effect of Brinkman number and magnetic field on laminar convection ...

    African Journals Online (AJOL)

    The effect of Brinkman number and magnetic field on laminar convection in a vertical plate channel with uniform and asymmetric temperatures has been studied. The dimensionless form of momentum and energy balanced equations has been solved using one term perturbation series solution. The solution of the ...

  17. Accuracy of tracer stimulus response experiments in laminar flows

    Czech Academy of Sciences Publication Activity Database

    Chlup, Hynek; Novotný, Pavel; Žitný, R.

    2012-01-01

    Roč. 55, 23-24 (2012), s. 6458-6462 ISSN 0017-9310 Institutional research plan: CEZ:AV0Z20760514 Keywords : residence time distribution * tracer injection * laminar convective dominated flow Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 2.315, year: 2012 http://www.sciencedirect.com/science/article/pii/S001793101200470X

  18. Investigations of Sooting Laminar Coflow Diffusion Flames at Elevated Pressures

    KAUST Repository

    Steinmetz, Scott

    2016-01-01

    diameters are successfully measured in nitrogen-diluted ethylene-air laminar coflow flames at pressures of 4, 8, 12, and 16 atm. An increase in particle size with pressure is found up to 12 atm, where particle sizes plateau. Particle size in the annulus

  19. Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam

    International Nuclear Information System (INIS)

    Maschke, A. W.

    1985-01-01

    A charged particle accelerating assembly provided with a predetermined ratio of parametric structural characteristics and with related operating voltages applied to each of its linearly spaced focusing and accelerating quadrupoles, thereby to maintain a particle beam traversing the electrostatic fields of the quadrupoles in the assembly in an essentially laminar flow throughout the assembly

  20. Computational Optimization of a Natural Laminar Flow Experimental Wing Glove

    Science.gov (United States)

    Hartshom, Fletcher

    2012-01-01

    Computational optimization of a natural laminar flow experimental wing glove that is mounted on a business jet is presented and discussed. The process of designing a laminar flow wing glove starts with creating a two-dimensional optimized airfoil and then lofting it into a three-dimensional wing glove section. The airfoil design process does not consider the three dimensional flow effects such as cross flow due wing sweep as well as engine and body interference. Therefore, once an initial glove geometry is created from the airfoil, the three dimensional wing glove has to be optimized to ensure that the desired extent of laminar flow is maintained over the entire glove. TRANAIR, a non-linear full potential solver with a coupled boundary layer code was used as the main tool in the design and optimization process of the three-dimensional glove shape. The optimization process uses the Class-Shape-Transformation method to perturb the geometry with geometric constraints that allow for a 2-in clearance from the main wing. The three-dimensional glove shape was optimized with the objective of having a spanwise uniform pressure distribution that matches the optimized two-dimensional pressure distribution as closely as possible. Results show that with the appropriate inputs, the optimizer is able to match the two dimensional pressure distributions practically across the entire span of the wing glove. This allows for the experiment to have a much higher probability of having a large extent of natural laminar flow in flight.

  1. Flight tests of a supersonic natural laminar flow airfoil

    International Nuclear Information System (INIS)

    Frederick, M A; Banks, D W; Garzon, G A; Matisheck, J R

    2015-01-01

    A flight test campaign of a supersonic natural laminar flow airfoil has been recently completed. The test surface was an 80 inch (203 cm) chord and 40 inch (102 cm) span article mounted on the centerline store location of an F-15B airplane. The test article was designed with a leading edge sweep of effectively 0° to minimize boundary layer crossflow. The test article surface was coated with an insulating material to avoid significant heat transfer to and from the test article structure to maintain a quasi-adiabatic wall. An aircraft-mounted infrared camera system was used to determine boundary layer transition and the extent of laminar flow. The tests were flown up to Mach 2.0 and chord Reynolds numbers in excess of 30 million. The objectives of the tests were to determine the extent of laminar flow at high Reynolds numbers and to determine the sensitivity of the flow to disturbances. Both discrete (trip dots) and 2D disturbances (forward-facing steps) were tested. A series of oblique shocks, of yet unknown origin, appeared on the surface, which generated sufficient crossflow to affect transition. Despite the unwanted crossflow, the airfoil performed well. The results indicate that the sensitivity of the flow to the disturbances, which can translate into manufacturing tolerances, was similar to that of subsonic natural laminar flow wings. (paper)

  2. Formation of coherent structures in 3D laminar mixing flows

    NARCIS (Netherlands)

    Speetjens, M.F.M.; Clercx, H.J.H.

    2009-01-01

    Mixing under laminar flow conditions is key to a wide variety of industrial systems of size extending from microns to meters. Examples range from the traditional (and still very relevant) mixing of viscous fluids via compact processing equipment down to emerging micro-fluidics applications. Profound

  3. Sequence of neuron origin and neocortical laminar fate: relation to cell cycle of origin in the developing murine cerebral wall

    Science.gov (United States)

    Takahashi, T.; Goto, T.; Miyama, S.; Nowakowski, R. S.; Caviness, V. S. Jr

    1999-01-01

    Neurons destined for each region of the neocortex are known to arise approximately in an "inside-to-outside" sequence from a pseudostratified ventricular epithelium (PVE). This sequence is initiated rostrolaterally and propagates caudomedially. Moreover, independently of location in the PVE, the neuronogenetic sequence in mouse is divisible into 11 cell cycles that occur over a 6 d period. Here we use a novel "birth hour" method that identifies small cohorts of neurons born during a single 2 hr period, i.e., 10-20% of a single cell cycle, which corresponds to approximately 1.5% of the 6 d neuronogenetic period. This method shows that neurons arising with the same cycle of the 11 cycle sequence in mouse have common laminar fates even if they arise from widely separated positions on the PVE (neurons of fields 1 and 40) and therefore arise at different embryonic times. Even at this high level of temporal resolution, simultaneously arising cells occupy more than one cortical layer, and there is substantial overlap in the distributions of cells arising with successive cycles. We demonstrate additionally that the laminar representation of cells arising with a given cycle is little if at all modified over the early postnatal interval of histogenetic cell death. We infer from these findings that cell cycle is a neuronogenetic counting mechanism and that this counting mechanism is integral to subsequent processes that determine cortical laminar fate.

  4. Analyzing dendritic growth in a population of immature neurons in the adult dentate gyrus using laminar quantification of disjointed dendrites

    Directory of Open Access Journals (Sweden)

    Shira eRosenzweig

    2011-03-01

    Full Text Available In the dentate gyrus of the hippocampus, new granule neurons are continuously produced throughout adult life. A prerequisite for the successful synaptic integration of these neurons is the sprouting and extension of dendrites into the molecular layer of the dentate gyrus. Thus, studies aimed at investigating the developmental stages of adult neurogenesis often use dendritic growth as an important indicator of neuronal health and maturity. Based on the known topography of the dentate gyrus, characterized by distinct laminar arrangement of granule neurons and their extensions, we have developed a new method for analysis of dendritic growth in immature adult-born granule neurons. The method is comprised of laminar quantification of cell bodies, primary, secondary and tertiary dendrites separately and independently from each other. In contrast to most existing methods, laminar quantification of dendrites does not require the use of exogenous markers and does not involve arbitrary selection of individual neurons. The new method relies on immonuhistochemical detection of endogenous markers such as doublecortin to perform a comprehensive analysis of a sub-population of immature neurons. Disjointed, orphan dendrites that often appear in the thin histological sections are taken into account. Using several experimental groups of rats and mice, we demonstrate here the suitable techniques for quantifying neurons and dendrites, and explain how the ratios between the quantified values can be used in a comparative analysis to indicate variations in dendritic growth and complexity.

  5. Boundary layer control by a fish: Unsteady laminar boundary layers of rainbow trout swimming in turbulent flows.

    Science.gov (United States)

    Yanase, Kazutaka; Saarenrinne, Pentti

    2016-12-15

    The boundary layers of rainbow trout, Oncorhynchus mykiss [0.231±0.016 m total body length (L) (mean±s.d.); N=6], swimming at 1.6±0.09 L s -1 (N=6) in an experimental flow channel (Reynolds number, Re=4×10 5 ) with medium turbulence (5.6% intensity) were examined using the particle image velocimetry technique. The tangential flow velocity distributions in the pectoral and pelvic surface regions (arc length from the rostrum, l x =71±8 mm, N=3, and l x =110±13 mm, N=4, respectively) were approximated by a laminar boundary layer model, the Falkner-Skan equation. The flow regime over the pectoral and pelvic surfaces was regarded as a laminar flow, which could create less skin-friction drag than would be the case with turbulent flow. Flow separation was postponed until vortex shedding occurred over the posterior surface (l x =163±22 mm, N=3). The ratio of the body-wave velocity to the swimming speed was in the order of 1.2. This was consistent with the condition of the boundary layer laminarization that had been confirmed earlier using a mechanical model. These findings suggest an energy-efficient swimming strategy for rainbow trout in a turbulent environment. © 2016. Published by The Company of Biologists Ltd.

  6. NUMERICAL STUDY OF DEVELOPING LAMINAR FORCED CONVECTION OF A NANOFLUID HEAT TRANSFER IN AN ANNULAR HORIZONTAL PIPE

    Directory of Open Access Journals (Sweden)

    M BENKHEDDA

    2014-12-01

    Full Text Available This study reports numerical simulation for 3D laminar forced convection of a nanofluid flow in horizontal annulus with constant heat flux at the outer cylinder will the inner cylinder is considered adiabatic. The numerical model is carried out by solving the governing equation of continuity, momentum and energy using take account for thee finite volume method, with the assistance of SIMPLER algorithm. The results shows that for the Reynolds numbers and Prandtl fixed, the dimensionless velocity profile for the laminar forced convection of a nanofluid consisting of water does not vary with the volume concentration of nanoparticles while the effect of the concentration of nanoparticles on the temperature of the mass is significant nanofluid. These results are consistent with those found in the literature. In general the use of nanofluid with a volume concentration of nanoparticles causes a increase in the coefficient of heat transfer by convection.

  7. Simulation of Low Velocity Impact Induced Inter- and Intra-Laminar Damage of Composite Beams Based on XFEM

    Science.gov (United States)

    Sun, Wei; Guan, Zhidong; Li, Zengshan

    2017-12-01

    In this paper, the Inter-Fiber Fracture (IFF) criterion of Puck failure theory based on the eXtended Finite Element Method (XFEM) was implemented in ABAQUS code to predict the intra-laminar crack initiation of unidirectional (UD) composite laminate. The transverse crack path in the matrix can be simulated accurately by the presented method. After the crack initiation, the propagation of the crack is simulated by Cohesive Zoom Model (CZM), in which the displacement discontinuities and stress concentration caused by matrix crack is introduced into the finite element (FE) model. Combined with the usage of the enriched element interface, which can be used to simulate the inter-laminar delamination crack, the Low Velocity Impact (LVI) induced damage of UD composite laminate beam with a typical stacking of composite laminates [05/903]S is studied. A complete crack initiation and propagation process was simulated and the numerical results obtained by the XFEM are consistent with the experimental results.

  8. Conceptual design for a laminar-flying-wing aircraft

    Science.gov (United States)

    Saeed, T. I.

    The laminar-flying-wing aircraft appears to be an attractive long-term prospect for reducing the environmental impact of commercial aviation. In assessing its potential, a relatively straightforward initial step is the conceptual design of a version with restricted sweep angle. Such a design is the topic of this thesis. Subject to constraints, this research aims to; provide insight into the parameters affecting practical laminar-flow-control suction power requirements; identify a viable basic design specification; and, on the basis of this, an assessment of the fuel efficiency through a detailed conceptual design study. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss in the boundary layer. This requirement increases with aerofoil section thickness, but depends only weakly on Mach number and (for a thick, lightly-loaded laminar flying wing) lift coefficient. Deviation from the optimal suction distribution, due to a practical chamber-based architecture, is found to have very little effect on the overall suction coefficient. In the spanwise direction, through suitable choice of chamber depth, the pressure drop due to frictional and inertial effects may be rendered negligible. Finally, it is found that the pressure drop from the aerofoil surface to the pump collector ducts determines the power penalty. To identify the viable basic design specification, a high-level exploration of the laminar flying wing design space is performed. The characteristics of the design are assessed as a function of three parameters: thickness-to-chord ratio, wingspan, and unit Reynolds number. A feasible specification, with 20% thickness-to-chord, 80 m span and a unit Reynolds number of 8 x 106 m-1, is identified; it corresponds to a 187 tonne aircraft which cruises at Mach 0.67 and altitude 22,500 ft, with lift coefficient 0.14. On the basis of this specification, a detailed conceptual design is

  9. Assessment of CFD Capability for Hypersonic Shock Wave Laminar Boundary Layer Interactions

    Directory of Open Access Journals (Sweden)

    Mehrnaz Rouhi Youssefi

    2017-04-01

    Full Text Available The goal of this study is to assess CFD capability for the prediction of shock wave laminar boundary layer interactions at hypersonic velocities. More specifically, the flow field over a double-cone configuration is simulated using both perfect gas and non-equilibrium Navier–Stokes models. Computations are compared with recent experimental data obtained from measurements conducted in the LENS XX (Large Energy National Shock Expansion Tunnel Version 2 at the Calspan University of Buffalo Research Center (CUBRC. Four separate cases of freestream conditions are simulated to examine the models for a range of stagnation enthalpies from 5.44 MJ/kg to 21.77 MJ/kg and Mach numbers from 10.9 to 12.82.

  10. Numerical simulation of the laminar hydrogen flame in the presence of a quenching mesh

    International Nuclear Information System (INIS)

    Kudriakov, S.; Studer, E.; Bin, C.

    2011-01-01

    Recent studies of J.H. Song et al., and S.Y. Yang et al. have been concentrated on mitigation measures against hydrogen risk. The authors have proposed installation of quenching meshes between compartments or around the essential equipment in order to contain hydrogen flames. Preliminary tests were conducted which demonstrated the possibility of flame extinction using metallic meshes of specific size. Considerable amount of numerical and theoretical work on flame quenching phenomenon has been performed in the second half of the last century and several techniques and models have been proposed to predict the quenching phenomenon of the laminar flame system. Most of these models appreciated the importance of heat loss to the surroundings as a primary cause of extinguishment, in particular, the heat transfer by conduction to the containing wall. The supporting simulations predict flame-quenching structure either between parallel plates (quenching distance) or inside a tube of a certain diameter (quenching diameter). In the present study the flame quenching is investigated assuming the laminar hydrogen flame propagating towards a quenching mesh using two-dimensional configuration and the earlier developed models. It is shown that due to a heat loss to a metallic grid the flame can be quenched numerically. (authors)

  11. Flow instability in laminar jet flames driven by alternating current electric fields

    KAUST Repository

    Kim, Gyeong Taek

    2016-10-13

    The effect of electric fields on the instability of laminar nonpremixed jet flames was investigated experimentally by applying the alternating current (AC) to a jet nozzle. We aimed to elucidate the origin of the occurrence of twin-lifted jet flames in laminar jet flow configurations, which occurred when AC electric fields were applied. The results indicated that a twin-lifted jet flame originated from cold jet instability, caused by interactions between negative ions in the jet flow via electron attachment as O +e→O when AC electric fields were applied. This was confirmed by conducting systematic, parametric experiment, which included changing gaseous component in jets and applying different polarity of direct current (DC) to the nozzle. Using two deflection plates installed in parallel with the jet stream, we found that only negative DC on the nozzle could charge oxygen molecules negatively. Meanwhile, the cold jet instability occurred only for oxygen-containing jets. A shedding frequency of jet stream due to AC driven instability showed a good correlation with applied AC frequency exhibiting a frequency doubling. However, for the applied AC frequencies over 80Hz, the jet did not respond to the AC, indicating an existence of a minimum flow induction time in a dynamic response of negative ions to external AC fields. Detailed regime of the instability in terms of jet velocity, AC voltage and frequency was presented and discussed. Hypothesized mechanism to explain the instability was also proposed.

  12. The Role of Molecule Clustering by Hydrogen Bond in Hydrous Ethanol on Laminar Burning Velocity

    Directory of Open Access Journals (Sweden)

    I Made Suarta

    2016-01-01

    Full Text Available The role of hydrogen bond molecule clustering in laminar burning velocities was observed. The water in hydrous ethanol can change the interaction between water-ethanol molecules. A certain amount of water can become oxygenated which increases the burning velocity. The hydrogen bond interaction pattern of ethanol and water molecules was modeled. Based on the molecular model, azeotropic behavior emerges from ethanol-water hydrogen bond, which is at a 95.1%v composition. The interaction with water molecule causes the ethanol molecule to be clustered with centered oxygenated compound. So, it supplies extra oxygen and provides intermolecular empty spaces that are easily infiltrated by the air. In the azeotropic composition, the molecular bond chain is the shortest, so hypothetically the burning velocity is anticipated to increase. The laminar burning velocity of ethanol fuel was tested in a cylindrical explosion bomb in lean, stoichiometric, and rich mixtures. The experimental result showed that the maximum burning velocity occurred at hydrous ethanol of 95.5%v composition. This discrepancy is the result of the addition of energy from 7.7% free ethanol molecules that are not clustered. At the rich mixture, the burning velocity of this composition is higher than that of anhydrous ethanol.

  13. Analysis of Low Speed Stall Aerodynamics of a Swept Wing with Laminar Flow Glove

    Science.gov (United States)

    Bui, Trong T.

    2014-01-01

    Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) analysis was conducted to study the low-speed stall aerodynamics of a GIII aircraft's swept wing modified with a laminar-flow wing glove. The stall aerodynamics of the gloved wing were analyzed and compared with the unmodified wing for the flight speed of 120 knots and altitude of 2300 ft above mean sea level (MSL). The Star-CCM+ polyhedral unstructured CFD code was first validated for wing stall predictions using the wing-body geometry from the First American Institute of Aeronautics and Astronautics (AIAA) CFD High-Lift Prediction Workshop. It was found that the Star-CCM+ CFD code can produce results that are within the scattering of other CFD codes considered at the workshop. In particular, the Star-CCM+ CFD code was able to predict wing stall for the AIAA wing-body geometry to within 1 degree of angle of attack as compared to benchmark wind-tunnel test data. Current results show that the addition of the laminar-flow wing glove causes the gloved wing to stall much earlier than the unmodified wing. Furthermore, the gloved wing has a different stall characteristic than the clean wing, with no sharp lift drop-off at stall for the gloved wing.

  14. Analysis of Low-Speed Stall Aerodynamics of a Swept Wing with Laminar-Flow Glove

    Science.gov (United States)

    Bui, Trong T.

    2014-01-01

    Reynolds-Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) analysis was conducted to study the low-speed stall aerodynamics of a GIII aircraft's swept wing modified with a laminar-flow wing glove. The stall aerodynamics of the gloved wing were analyzed and compared with the unmodified wing for the flight speed of 120 knots and altitude of 2300 ft above mean sea level (MSL). The Star-CCM+ polyhedral unstructured CFD code was first validated for wing stall predictions using the wing-body geometry from the First American Institute of Aeronautics and Astronautics (AIAA) CFD High-Lift Prediction Workshop. It was found that the Star-CCM+ CFD code can produce results that are within the scattering of other CFD codes considered at the workshop. In particular, the Star-CCM+ CFD code was able to predict wing stall for the AIAA wing-body geometry to within 1 degree of angle of attack as compared to benchmark wind-tunnel test data. Current results show that the addition of the laminar-flow wing glove causes the gloved wing to stall much earlier than the unmodified wing. Furthermore, the gloved wing has a different stall characteristic than the clean wing, with no sharp lift drop-off at stall for the gloved wing.

  15. Forced underwater laminar flows with active magnetohydrodynamic metamaterials

    Science.gov (United States)

    Culver, Dean; Urzhumov, Yaroslav

    2017-12-01

    Theory and practical implementations for wake-free propulsion systems are proposed and proven with computational fluid dynamic modeling. Introduced earlier, the concept of active hydrodynamic metamaterials is advanced by introducing magnetohydrodynamic metamaterials, structures with custom-designed volumetric distribution of Lorentz forces acting on a conducting fluid. Distributions of volume forces leading to wake-free, laminar flows are designed using multivariate optimization. Theoretical indications are presented that such flows can be sustained at arbitrarily high Reynolds numbers. Moreover, it is shown that in the limit Re ≫102 , a fixed volume force distribution may lead to a forced laminar flow across a wide range of Re numbers, without the need to reconfigure the force-generating metamaterial. Power requirements for such a device are studied as a function of the fluid conductivity. Implications to the design of distributed propulsion systems underwater and in space are discussed.

  16. Energy fluxes and spectra for turbulent and laminar flows

    KAUST Repository

    Verma, Mahendra K.

    2017-05-14

    Two well-known turbulence models to describe the inertial and dissipative ranges simultaneously are by Pao~[Phys. Fluids {\\\\bf 8}, 1063 (1965)] and Pope~[{\\\\em Turbulent Flows.} Cambridge University Press, 2000]. In this paper, we compute energy spectrum $E(k)$ and energy flux $\\\\Pi(k)$ using spectral simulations on grids up to $4096^3$, and show consistency between the numerical results and predictions by the aforementioned models. We also construct a model for laminar flows that predicts $E(k)$ and $\\\\Pi(k)$ to be of the form $\\\\exp(-k)$, and verify the model predictions using numerical simulations. The shell-to-shell energy transfers for the turbulent flows are {\\\\em forward and local} for both inertial and dissipative range, but those for the laminar flows are {\\\\em forward and nonlocal}.

  17. Predictions of laminar natural convection in heated cavities

    International Nuclear Information System (INIS)

    Winters, K.H.

    1982-06-01

    Several examples of laminar, natural convection in heated cavities are discussed with illustrative calculations. These include convection in a square cavity at high Rayleigh number; in a narrow cavity at moderate aspect ratio; in a rectangular cavity heated from below; in a trapezoidal cavity, and in a rectangular cavity containing a conducting obstruction. The steady equations for the velocity, pressure and temperature are solved in the Boussinesq approximation, using a standard Galerkin formulation of the finite-element method. (author)

  18. Simulation of hypersonic shock wave - laminar boundary layer interactions

    Science.gov (United States)

    Kianvashrad, N.; Knight, D.

    2017-06-01

    The capability of the Navier-Stokes equations with a perfect gas model for simulation of hypersonic shock wave - laminar boundary layer interactions is assessed. The configuration is a hollow cylinder flare. The experimental data were obtained by Calspan-University of Buffalo (CUBRC) for total enthalpies ranging from 5.07 to 21.85 MJ/kg. Comparison of the computed and experimental surface pressure and heat transfer is performed and the computed §ow¦eld structure is analyzed.

  19. INCOMPRESSIBLE LAMINAR BOUNDARY LAYER CONTROL BY BLOWING AND SUCTION

    OpenAIRE

    AZZEDINE NAHOUI; LAKHDAR BAHI

    2013-01-01

    A two-dimensional incompressible laminar boundary layer and its control using blowing and suction over a flat plate and around the NACA 0012 and 661012 profiles, is studied numerically. The study is based on the Prandtl boundary layer model using the finite differences method and the Crank-Nicolson scheme. The velocity distribution, the boundary layer thickness and the friction coefficient, are determined and presented with and without control. The application of the control technique, has de...

  20. Nanocomposites transparentes multifuncionales de hidróxido doble laminares

    OpenAIRE

    Fernández Vilaber, Antonio

    2017-01-01

    Este trabajo trata sobre obtener una serie de materiales nanocompuestos en forma de película para usarlos como plásticos de invernadero. Para ello se sintetizarán hidróxidos dobles laminares modificados con un agente blanqueante óptico que mejorará las propiedades ópticas del material Escuela Técnica Superior de Ingeniería Industrial Universidad Politécnica de Cartagena

  1. Cold laminar galvanizing: a new anti-corrosion concept

    International Nuclear Information System (INIS)

    Bagnulo, L.H.

    1984-01-01

    Cold laminar galvanizing, a recent anticorrosion technology, now combines the most positive characteristics of the hot galvanizing protective systems. This patented technology has a zinc laminated foil (obtained by processing 99.9% pure zinc ingots) that is homogeneous and isotropic, with a standard thickness of 80-100μm. This foil is backed with an electro-conductive, selfadhesive glue prepared under an original formula. The zinc laminated foil offers excellent anchorage and elevated resistance to the main atmospheric agents

  2. Magnus effect on laminar flow around a rotating cylinder

    International Nuclear Information System (INIS)

    Amarante, J.C.A.

    1989-01-01

    The laminar flow around a rotating cylinder is studied, through the numerical solution of the full Navier-Stokes equations, for Reynolds number, based on cylinder radius, varying between 0.5 and 25 and for non-dimensional tangential velocities of the body surface between zero and 8. The Taylor and Hughes method is employed in the theoretical investigation. The Magnus lift coefficient and the drag coefficient are obtained and the presure and vorticity distribution are calculated. (author)

  3. Characteristics of laminar MHD fluid hammer in pipe

    International Nuclear Information System (INIS)

    Huang, Z.Y.; Liu, Y.J.

    2016-01-01

    As gradually wide applications of MHD fluid, transportation as well as control with pumps and valves is unavoidable, which induces MHD fluid hammer. The paper attempts to combine MHD effect and fluid hammer effect and to investigate the characteristics of laminar MHD fluid hammer. A non-dimensional fluid hammer model, based on Navier–Stocks equations, coupling with Lorentz force is numerically solved in a reservoir–pipe–valve system with uniform external magnetic field. The MHD effect is represented by the interaction number which associates with the conductivity of the MHD fluid as well as the external magnetic field and can be interpreted as the ratio of Lorentz force to Joukowsky force. The transient numerical results of pressure head, average velocity, wall shear stress, velocity profiles and shear stress profiles are provided. The additional MHD effect hinders fluid motion, weakens wave front and homogenizes velocity profiles, contributing to obvious attenuation of oscillation, strengthened line packing and weakened Richardson annular effect. Studying the characteristics of MHD laminar fluid hammer theoretically supplements the gap of knowledge of rapid-transient MHD flow and technically provides beneficial information for MHD pipeline system designers to better devise MHD systems. - Highlights: • Characteristics of laminar MHD fluid hammer are discussed by simulation. • MHD effect has significant influence on attenuation of wave. • MHD effect strengthens line packing. • MHD effect inhibits Richardson annular effect.

  4. Aerodynamics of wings at low Reynolds numbers: Boundary layer separation and reattachment

    Science.gov (United States)

    McArthur, John

    Due to advances in electronics technology, it is now possible to build small scale flying and swimming vehicles. These vehicles will have size and velocity scales similar to small birds and fish, and their characteristic Reynolds number will be between 104 and 105. Currently, these flying and swimming vehicles do not perform well, and very little research has been done to characterize them, or to explain why they perform so poorly. This dissertation documents three basic investigations into the performance of small scale lifting surfaces, with Reynolds numbers near 104. Part I. Low Reynolds number aerodynamics. Three airfoil shapes were studied at Reynolds numbers of 1 and 2x104: a flat plate airfoil, a circular arc cambered airfoil, and the Eppler 387 airfoil. Lift and drag force measurements were made on both 2D and 3D conditions, with the 3D wings having an aspect ratio of 6, and the 2D condition being approximated by placing end plates at the wing tips. Comparisons to the limited number of previous measurements show adequate agreement. Previous studies have been inconclusive on whether lifting line theory can be applied to this range of Re, but this study shows that lifting line theory can be applied when there are no sudden changes in the slope of the force curves. This is highly dependent on the airfoil shape of the wing, and explains why previous studies have been inconclusive. Part II. The laminar separation bubble. The Eppler 387 airfoil was studied at two higher Reynolds numbers: 3 and 6x10 4. Previous studies at a Reynolds number of 6x104 had shown this airfoil experiences a drag increase at moderate lift, and a subsequent drag decrease at high lift. Previous studies suggested that the drag increase is caused by a laminar separation bubble, but the experiments used to show this were conducted at higher Reynolds numbers and extrapolated down. Force measurements were combined with flow field measurements at Reynolds numbers 3 and 6x104 to determine whether

  5. On recent developments in marginal separation theory.

    Science.gov (United States)

    Braun, S; Scheichl, S

    2014-07-28

    Thin aerofoils are prone to localized flow separation at their leading edge if subjected to moderate angles of attack α. Although 'laminar separation bubbles' at first do not significantly alter the aerofoil performance, they tend to 'burst' if α is increased further or if perturbations acting upon the flow reach a certain intensity. This then either leads to global flow separation (stall) or triggers the laminar-turbulent transition process within the boundary layer flow. This paper addresses the asymptotic analysis of the early stages of the latter phenomenon in the limit as the characteristic Reynolds number [Formula: see text], commonly referred to as marginal separation theory. A new approach based on the adjoint operator method is presented that enables the fundamental similarity laws of marginal separation theory to be derived and the analysis to be extended to higher order. Special emphasis is placed on the breakdown of the flow description, i.e. the formation of finite-time singularities (a manifestation of the bursting process), and on its resolution being based on asymptotic arguments. The passage to the subsequent triple-deck stage is described in detail, which is a prerequisite for carrying out a future numerical treatment of this stage in a proper way. Moreover, a composite asymptotic model is developed in order for the inherent ill-posedness of the Cauchy problems associated with the current flow description to be resolved.

  6. The control effect in a detached laminar boundary layer of an array of normal synthetic jets

    Science.gov (United States)

    Valenzuela Calva, Fernando; Avila Rodriguez, Ruben

    2016-11-01

    In this work, 3D numerical simulations of an array of three normal circular synthetic jets embedded in an attached laminar boundary layer that separates under the influence of an inclined flap are performed for flow separation control. At the beginning of the present study, three cases are used to validate the numerical simulation with data obtained from experiments. The experimental data is chosen based on the cases which presented higher repeatability and reliability. Simulations showed reasonable agreement when compared with experiments. The simulations are undertaken at three synthetic jet operating conditions, i.e. Case A: L = 2, VR = 0.32; Case B: L = 4, VR = 0.64 and Case C: L = 6, VR = 0.96. The vortical structures produced for each synthetic jet operating condition are hairpin vortices for Case A and tilted vortices for Case B and C, respectively. By examining the spatial wall shear stress variations, the effect on the boundary layer prior to separation of the middle synthetic jet is evaluated. For effective flow control, produced at a relatively low the finding from this study suggests that hairpin vortical structures are more desirable structures. Universidad Nacional Autonoma de Mexico.

  7. Extinction of laminar partially premixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Aggarwal, Suresh K. [Department of Mechanical and Industrial Engineering, University of Illinois at Chicago, 842 W. Taylor Street, Room 2039, MC-251, Chicago, IL 60607-7022 (United States)

    2009-12-15

    Flame extinction represents one of the classical phenomena in combustion science. It is important to a variety of combustion systems in transportation and power generation applications. Flame extinguishment studies are also motivated from the consideration of fire safety and suppression. Such studies have generally considered non-premixed and premixed flames, although fires can often originate in a partially premixed mode, i.e., fuel and oxidizer are partially premixed as they are transported to the reaction zone. Several recent investigations have considered this scenario and focused on the extinction of partially premixed flames (PPFs). Such flames have been described as hybrid flames possessing characteristics of both premixed and non-premixed flames. This paper provides a review of studies dealing with the extinction of PPFs, which represent a broad family of flames, including double, triple (tribrachial), and edge flames. Theoretical, numerical and experimental studies dealing with the extinction of such flames in coflow and counterflow configurations are discussed. Since these flames contain both premixed and non-premixed burning zones, a brief review of the dilution-induced extinction of premixed and non-premixed flames is also provided. For the coflow configuration, processes associated with flame liftoff and blowout are described. Since lifted non-premixed jet flames often contain a partially premixed or an edge-flame structure prior to blowout, the review also considers such flames. While the perspective of this review is broad focusing on the fundamental aspects of flame extinction and blowout, results mostly consider flame extinction caused by the addition of a flame suppressant, with relevance to fire suppression on earth and in space environment. With respect to the latter, the effect of gravity on the extinction of PPFs is discussed. Future research needs are identified. (author)

  8. Non-laminar flow model for the impedance of a rod-pinch diode

    International Nuclear Information System (INIS)

    Ottinger, Paul F.; Schumer, Joseph W.; Strasburg, Sean D.; Swanekamp, Stephen B.; Oliver, Bryan V.

    2002-01-01

    A previous laminar flow model for the rod-pinch diode is extended to include a transverse pressure term to study the effects of non-laminar flow. The non-laminar nature of the flow has a significant impact on the diode impedance. Results show that the introduction of the transverse pressure decreases the diode impedance predicted by the model bringing it into better agreement with experimental data

  9. Laminar and Turbulent Flow Calculations for the Hifire-5B Flight Test

    Science.gov (United States)

    2017-11-01

    STATES AIR FORCE AFRL-RQ-WP-TP-2017-0172 LAMINAR AND TURBULENT FLOW CALCULATIONS FOR THE HIFIRE-5B FLIGHT TEST Roger L. Kimmel Hypersonic Sciences...stationary instabilities of the three-dimensional flow as the grid becomes finer. It may not be possible to obtain a strictly laminar basic state on a very...fine grid. A basic state solution was desired for the laminar flow calculations, and the oscillations observed in Fig. 3 were judged to be undesirable

  10. A note on high Schmidt number laminar buoyant jets discharged horizontally

    International Nuclear Information System (INIS)

    Dewan, A.; Arakeri, J.H.; Srinivasan, J.

    1992-01-01

    This paper reports on a new model, developed for the integral analysis of high Schmidt number (or equivalently high Prandtl number) laminar buoyant jets discharged horizontally. This model assumes top-hat density profile across the inner core of jet and Gaussian velocity profile. Entrainment coefficient corresponding to pure laminar jet has been taken in the analysis. The prediction of the jet trajectory agree well with experimental data in the regions where the jet remains laminar

  11. Convective heat transfer in foams under laminar flow in pipes and tube bundles.

    Science.gov (United States)

    Attia, Joseph A; McKinley, Ian M; Moreno-Magana, David; Pilon, Laurent

    2012-12-01

    The present study reports experimental data and scaling analysis for forced convection of foams and microfoams in laminar flow in circular and rectangular tubes as well as in tube bundles. Foams and microfoams are pseudoplastic (shear thinning) two-phase fluids consisting of tightly packed bubbles with diameters ranging from tens of microns to a few millimeters. They have found applications in separation processes, soil remediation, oil recovery, water treatment, food processes, as well as in fire fighting and in heat exchangers. First, aqueous solutions of surfactant Tween 20 with different concentrations were used to generate microfoams with various porosity, bubble size distribution, and rheological behavior. These different microfoams were flowed in uniformly heated circular tubes of different diameter instrumented with thermocouples. A wide range of heat fluxes and flow rates were explored. Experimental data were compared with analytical and semi-empirical expressions derived and validated for single-phase power-law fluids. These correlations were extended to two-phase foams by defining the Reynolds number based on the effective viscosity and density of microfoams. However, the local Nusselt and Prandtl numbers were defined based on the specific heat and thermal conductivity of water. Indeed, the heated wall was continuously in contact with a film of water controlling convective heat transfer to the microfoams. Overall, good agreement between experimental results and model predictions was obtained for all experimental conditions considered. Finally, the same approach was shown to be also valid for experimental data reported in the literature for laminar forced convection of microfoams in rectangular minichannels and of macrofoams across aligned and staggered tube bundles with constant wall heat flux.

  12. Motion of cells sedimenting on a solid surface in a laminar shear flow.

    Science.gov (United States)

    Tissot, O; Pierres, A; Foa, C; Delaage, M; Bongrand, P

    1992-01-01

    Cell adhesion often occurs under dynamic conditions, as in flowing blood. A quantitative understanding of this process requires accurate knowledge of the topographical relationships between the cell membrane and potentially adhesive surfaces. This report describes an experimental study made on both the translational and rotational velocities of leukocytes sedimenting of a flat surface under laminar shear flow. The main conclusions are as follows: (a) Cells move close to the wall with constant velocity for several tens of seconds. (b) The numerical values of translational and rotational velocities are inconsistent with Goldman's model of a neutrally buoyant sphere in a laminar shear flow, unless a drag force corresponding to contact friction between cells and the chamber floor is added. The phenomenological friction coefficient was 7.4 millinewton.s/m. (c) Using a modified Goldman's theory, the width of the gap separating cells (6 microns radius) from the chamber floor was estimated at 1.4 micron. (d) It is shown that a high value of the cell-to-substrate gap may be accounted for by the presence of cell surface protrusions of a few micrometer length, in accordance with electron microscope observations performed on the same cell population. (e) In association with previously reported data (Tissot, O., C. Foa, C. Capo, H. Brailly, M. Delaage, and P. Bongrand. 1991. Biocolloids and Biosurfaces. In press), these results are consistent with the possibility that cell-substrate attachment be initiated by the formation of a single molecular bond, which might be considered as the rate limiting step.

  13. Vortex dynamics of in-line twin synthetic jets in a laminar boundary layer

    Science.gov (United States)

    Wen, Xin; Tang, Hui; Duan, Fei

    2015-08-01

    An experimental investigation is conducted on the vortices induced by twin synthetic jets (SJs) in line with a laminar boundary layer flow over a flat plate. The twin SJs operating at four different phase differences, i.e., Δϕ = 0°, 90°, 180°, and 270°, are visualized using a stereoscopic color dye visualization system and measured using a two-dimensional particle image velocimetry (PIV) system. It is found that depending on the phase difference of twin SJs, three types of vortex structures are produced. At Δϕ = 90°, the two hairpin vortices interact in a very constructive way in terms of the vortex size, strength, and celerity, forming one combined vortex. At Δϕ = 270°, the two individual hairpin vortices do not have much interaction, forming two completely separated hairpin vortices that behave like doubling the frequency of the single SJ case. At Δϕ = 0° and 180°, the two hairpin vortices produced by the twin SJ actuators are close enough, with the head of one hairpin vortex coupled with the legs of the other, forming partially interacting vortex structures. Quantitative analysis of the twin SJs is conducted, including the time histories of vortex circulation in the mid-span plane as well as a selected spanwise-wall-normal plane, and the influence of the twin SJs on the boundary layer flow filed. In addition, dynamic mode decomposition analysis of the PIV data is conducted to extract representative coherent structures. Through this study, a better understanding in the vortex dynamics associated with the interaction of in-line twin SJs in laminar boundary layers is achieved, which provides useful information for future SJ-array applications.

  14. Axisymmetric thermoviscoelastoplastic state of branched laminar shells, taking account of transverse-shear and torsional deformation

    International Nuclear Information System (INIS)

    Galishin, A.Z.

    1995-01-01

    The nonaxisymmetric thermoelastic stress-strain state (SSS) of branched laminar orthotropic shells was considered; the axisymmetric thermoviscoelastic SSS of branched laminar orthotropic shells was considered; and the axisymmetric thermoviscoelastoplastic SSS of branched laminar isotropic shells was considered, taking into account of the transverse-shear deformation. In the present work, in contrast, the axisymmetric thermoviscoelastoplastic SSS of branched laminar isotropic shells is considered, taking account of transverse-shear and torsional deformation. Layers that are made from orthotropic materials and deform in the elastic region may be present

  15. Quality improvement of melt extruded laminar systems using mixture design.

    Science.gov (United States)

    Hasa, D; Perissutti, B; Campisi, B; Grassi, M; Grabnar, I; Golob, S; Mian, M; Voinovich, D

    2015-07-30

    This study investigates the application of melt extrusion for the development of an oral retard formulation with a precise drug release over time. Since adjusting the formulation appears to be of the utmost importance in achieving the desired drug release patterns, different formulations of laminar extrudates were prepared according to the principles of Experimental Design, using a design for mixtures to assess the influence of formulation composition on the in vitro drug release from the extrudates after 1h and after 8h. The effect of each component on the two response variables was also studied. Ternary mixtures of theophylline (model drug), monohydrate lactose and microcrystalline wax (as thermoplastic binder) were extruded in a lab scale vertical ram extruder in absence of solvents at a temperature below the melting point of the binder (so that the crystalline state of the drug could be maintained), through a rectangular die to obtain suitable laminar systems. Thanks to the desirability approach and a reliability study for ensuring the quality of the formulation, a very restricted optimal zone was defined within the experimental domain. Among the mixture components, the variation of microcrystalline wax content played the most significant role in overall influence on the in vitro drug release. The formulation theophylline:lactose:wax, 57:14:29 (by weight), selected based on the desirability zone, was subsequently used for in vivo studies. The plasma profile, obtained after oral administration of the laminar extruded system in hard gelatine capsules, revealed the typical trend of an oral retard formulation. The application of the mixture experimental design associated to a desirability function permitted to optimize the extruded system and to determine the composition space that ensures final product quality. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Leading edge effect in laminar boundary layer excitation by sound

    International Nuclear Information System (INIS)

    Leehey, P.; Shapiro, P.

    1980-01-01

    Essentially plane pure tone sound waves were directed downstream over a heavily damped smooth flat plate installed in a low turbulence (0.04%) subsonic wind tunnel. Laminar boundary layer disturbance growth rates were measured with and without sound excitation and compared with numerical results from spatial stability theory. The data indicate that the sound field and Tollmien-Schlichting (T-S) waves coexist with comparable amplitudes when the latter are damped; moreover, the response is linear. Higher early growth rates occur for excitation by sound than by stream turbulence. Theoretical considerations indicate that the boundary layer is receptive to sound excitation primarily at the test plate leading edge. (orig.)

  17. INCOMPRESSIBLE LAMINAR BOUNDARY LAYER CONTROL BY BLOWING AND SUCTION

    Directory of Open Access Journals (Sweden)

    AZZEDINE NAHOUI

    2013-12-01

    Full Text Available A two-dimensional incompressible laminar boundary layer and its control using blowing and suction over a flat plate and around the NACA 0012 and 661012 profiles, is studied numerically. The study is based on the Prandtl boundary layer model using the finite differences method and the Crank-Nicolson scheme. The velocity distribution, the boundary layer thickness and the friction coefficient, are determined and presented with and without control. The application of the control technique, has demonstrated its positive effect on the transition point and the friction coefficient. Both control procedures are compared for different lengths, speeds and angles of blowing and suction.

  18. High-Fidelity Aerodynamic Shape Optimization for Natural Laminar Flow

    Science.gov (United States)

    Rashad, Ramy

    To ensure the long-term sustainability of aviation, serious effort is underway to mitigate the escalating economic, environmental, and social concerns of the industry. Significant improvement to the energy efficiency of air transportation is required through the research and development of advanced and unconventional airframe and engine technologies. In the quest to reduce airframe drag, this thesis is concerned with the development and demonstration of an effective design tool for improving the aerodynamic efficiency of subsonic and transonic airfoils. The objective is to advance the state-of-the-art in high-fidelity aerodynamic shape optimization by incorporating and exploiting the phenomenon of laminar-turbulent transition in an efficient manner. A framework for the design and optimization of Natural Laminar Flow (NLF) airfoils is developed and demonstrated with transition prediction capable of accounting for the effects of Reynolds number, freestream turbulence intensity, Mach number, and pressure gradients. First, a two-dimensional Reynolds-averaged Navier-Stokes (RANS) flow solver has been extended to incorporate an iterative laminar-turbulent transition prediction methodology. The natural transition locations due to Tollmien-Schlichting instabilities are predicted using the simplified eN envelope method of Drela and Giles or, alternatively, the compressible form of the Arnal-Habiballah-Delcourt criterion. The boundary-layer properties are obtained directly from the Navier-Stokes flow solution, and the transition to turbulent flow is modeled using an intermittency function in conjunction with the Spalart-Allmaras turbulence model. The RANS solver is subsequently employed in a gradient-based sequential quadratic programming shape optimization framework. The laminar-turbulent transition criteria are tightly coupled into the objective and gradient evaluations. The gradients are obtained using a new augmented discrete-adjoint formulation for non-local transition

  19. DRAG REDUCTION IN LAMINAR FLOW BY LUBRICATION OF GROOVED WALLS

    OpenAIRE

    JULIO RAUL SIERRA VASQUEZ

    2009-01-01

    Objetivo: Uma parte significativa das reservas mundiais de petróleo é encontrada na forma de óleos pesados. Estes óleos pesados possuem alta viscosidade de 100 - 10000 cP, que torna seu transporte altamente complexo e custoso. Vários métodos foram desenvolvidos para reduzir a perda de carga de escoamentos laminares de óleos de alta viscosidade. Entre os mais utilizados, pode-se citar o bombeio de um fluido de baixa viscosidade perto da parede do tubo com o óleo viscoso sendo...

  20. Use of laminar flow patterning for miniaturised biochemical assays

    DEFF Research Database (Denmark)

    Regenberg, Birgitte; Krühne, Ulrich; Beyer, M.

    2004-01-01

    Laminar flow in microfluidic chambers was used to construct low (one dimensional) density arrays suitable for miniaturized biochemical assays. By varying the ratio of flows of two guiding streams flanking a sample stream, precise focusing and positioning of the latter was achieved, and reactive s...... species carried in the sample stream were deposited on functionalized chip surfaces as discrete 50 mm wide lanes. Using different model systems we have confirmed the method's suitability for qualitative screening and quantification tasks in receptor-ligand assays, recording biotin...

  1. Laminar phase flow for an exponentially tapered Josephson oscillator

    DEFF Research Database (Denmark)

    Benabdallah, A.; Caputo, J. G.; Scott, Alwyn C.

    2000-01-01

    Exponential tapering and inhomogeneous current feed were recently proposed as means to improve the performance of a Josephson flux flow oscillator. Extensive numerical results backed up by analysis are presented here that support this claim and demonstrate that exponential tapering reduces...... the small current instability region and leads to a laminar flow regime where the voltage wave form is periodic giving the oscillator minimal spectral width. Tapering also leads to an increased output power. Since exponential tapering is not expected to increase the difficulty of fabricating a flux flow...

  2. Surface Runoff in Watershed Modeling—Turbulent or Laminar Flows?

    Directory of Open Access Journals (Sweden)

    Mark E. Grismer

    2016-05-01

    Full Text Available Determination of overland sheet flow depths, velocities and celerities across the hillslope in watershed modeling is important towards estimation of surface storage, travel times to streams and soil detachment rates. It requires careful characterization of the flow processes. Similarly, determination of the temporal variation of hillslope-riparian-stream hydrologic connectivity requires estimation of the shallow subsurface soil hydraulic conductivity and soil-water retention (i.e., drainable porosities parameters. Field rainfall and runoff simulation studies provide considerable information and insight into these processes; in particular, that sheet flows are likely laminar and that shallow hydraulic conductivities and storage can be determined from the plot studies. Here, using a 1 m by 2 m long runoff simulation flume, we found that for overland flow rates per unit width of roughly 30–60 mm2/s and bedslopes of 10%–66% with varying sand roughness depths that all flow depths were predicted by laminar flow equations alone and that equivalent Manning’s n values were depth dependent and quite small relative to those used in watershed modeling studies. Even for overland flow rates greater than those typically measured or modeled and using Manning’s n values of 0.30–0.35, often assumed in physical watershed model applications for relatively smooth surface conditions, the laminar flow velocities were 4–5 times greater, while the laminar flow depths were 4–5 times smaller. This observation suggests that travel times, surface storage volumes and surface shear stresses associated with erosion across the landscape would be poorly predicted using turbulent flow assumptions. Filling the flume with fine sand and conducting runoff studies, we were unable to produce sheet flow, but found that subsurface flows were onflow rate, soil depth and slope dependent and drainable porosities were only soil depth and slope dependent. Moreover, both the sand

  3. Acute hepatic encephalopathy presenting as cortical laminar necrosis: Case report

    International Nuclear Information System (INIS)

    Choi, Jong Mun; Kim, Yoon Hee; Roh, Sook Young

    2013-01-01

    We report on a 55-year-old man with alcoholic liver cirrhosis who presented with status epilepticus. Laboratory analysis showed markedly elevated blood ammonia. Brain magnetic resonance imaging (MRI) showed widespread cortical signal changes with restricted diffusion, involving both temporo-fronto-parietal cortex, while the perirolandic regions and occipital cortex were uniquely spared. A follow-up brain MRI demonstrated diffuse cortical atrophy with increased signals on T1-weighted images in both the basal ganglia and temporal lobe cortex, representing cortical laminar necrosis. We suggest that the brain lesions, in our case, represent a consequence of toxic effect of ammonia.

  4. Acute hepatic encephalopathy presenting as cortical laminar necrosis: Case report

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jong Mun; Kim, Yoon Hee; Roh, Sook Young [Bundang Jesaeng General Hospital, Daejin Medical Center, Seongnam (Korea, Republic of)

    2013-04-15

    We report on a 55-year-old man with alcoholic liver cirrhosis who presented with status epilepticus. Laboratory analysis showed markedly elevated blood ammonia. Brain magnetic resonance imaging (MRI) showed widespread cortical signal changes with restricted diffusion, involving both temporo-fronto-parietal cortex, while the perirolandic regions and occipital cortex were uniquely spared. A follow-up brain MRI demonstrated diffuse cortical atrophy with increased signals on T1-weighted images in both the basal ganglia and temporal lobe cortex, representing cortical laminar necrosis. We suggest that the brain lesions, in our case, represent a consequence of toxic effect of ammonia.

  5. A separator

    Energy Technology Data Exchange (ETDEWEB)

    Prokopyuk, S.G.; Dyachenko, A.Ye.; Mukhametov, M.N.; Prokopov, O.I.

    1982-01-01

    A separator is proposed which contains separating slanted plates and baffle plates installed at a distance to them at an acute angle to them. To increase the effectiveness of separating a gas and liquid stream and the throughput through reducing the secondary carry away of the liquid drops and to reduce the hydraulic resistance, as well, openings are made in the plates. The horizontal projections of each opening from the lower and upper surfaces of the plate do not overlap each other.

  6. Is the Magnetic Field in the Heliosheath Sector Region and in the Outer Heliosheath Laminar?

    Science.gov (United States)

    Opher, M.; Drake, J. F.; Swisdak, M. M.; Toth, G.

    2010-12-01

    All the current global models of the heliosphere are based on the assumption that the magnetic field in the outer heliosheath close to the heliopause is laminar. We argue that in the outer heliosheath the heliospheric magnetic field is not laminar but instead consists of nested magnetic islands. Recently, we proposed (Drake et al. 2009) that the annihilation of the ``sectored'' magnetic field within the heliosheath as it is compressed on its approach to the heliopause produces the anomalous cosmic rays (ACRs) and also energetic electrons. As a product of the annihilation of the sectored magnetic field, densly-packed magnetic islands are produced. These magnetic islands will be convected with the ambient flows as the sector boundary is carried to higher latitudes filling the outer heliosheath. We further argue that the magnetic islands will develop upstream (but still within the heliosheath) where collisionless reconnection is unfavorable -- large perturbations of the sector structure near the heliopause will cause compressions of the current sheet upstream, triggering reconnection. As a result, the magnetic field in the heliosheath sector region will be disordered well upstream of the heliopause. We present a 3D MHD simulation with unprecedent numerical resolution that captures the sector boundary. We show that due to the high pressure of the interstellar magnetic field the disordered sectored region fills a large portion of the northern part of the heliosphere with a smaller extension in the southern hemisphere. We test these ideas with observations of energetic electrons, which because of their high velocity are most sensitive to the structure of the magnetic field. We suggest that within our scenario we can explain two significant anomalies in the observations of energetic electrons in the outer heliosphere: the sudden decrease in the intensity of low energy electrons (0.02-1.5MeV) from the LECP instrument on Voyager 2 in 2008 (Decker 2010); and the dramatic

  7. Numerical study of laminar, standing hydraulic jumps in a planar geometry.

    Science.gov (United States)

    Dasgupta, Ratul; Tomar, Gaurav; Govindarajan, Rama

    2015-05-01

    We solve the two-dimensional, planar Navier-Stokes equations to simulate a laminar, standing hydraulic jump using a Volume-of-Fluid method. The geometry downstream of the jump has been designed to be similar to experimental conditions by including a pit at the edge of the platform over which liquid film flows. We obtain jumps with and without separation. Increasing the inlet Froude number pushes the jump downstream and makes the slope of the jump weaker, consistent with experimental observations of circular jumps, and decreasing the Reynolds number brings the jump upstream while making it steeper. We study the effect of the length of the domain and that of a downstream obstacle on the structure and location of the jump. The transient flow which leads to a final steady jump is described for the first time to our knowledge. In the moderate Reynolds number regime, we obtain steady undular jumps with a separated bubble underneath the first few undulations. Interestingly, surface tension leads to shortening of wavelength of these undulations. We show that the undulations can be explained using the inviscid theory of Benjamin and Lighthill (Proc. R. Soc. London, Ser. A, 1954). We hope this new finding will motivate experimental verification.

  8. Water purification from cesium-137 and strontium-90 using natural and activated laminar and laminar-band silicates

    International Nuclear Information System (INIS)

    Kornilovich, B.Yu.; Pshinko, G.N.; Kosorukov, A.A.; Mas'ko, A.N.; Spasenova, L.N.; Dregval', T.N.

    1991-01-01

    Cesium-137 and strontium-90 radionuclides are studied for the process of their sorption from natural waters by basic representatives of disperse silicates: kaolinites of Glukhovetskoe and Glukhovskoe deposits (Ukraine), montmorillonites of the Cherkassy (Ukraine) and Oglanlin (Turkmenia) deposits, palygorskite and natural mixture of montmorillonite and palygorskite of the Cherkassy deposit. The best sorption properties are revealed for laminated silicates with a swelling structure (montmorillonites) and high-dispersive laminar-band silicates (palygorskite). It proved possible to improve sorption properties of silicate minerals for radionuclides by means of their mechanochemical activation

  9. Isotope separation

    International Nuclear Information System (INIS)

    Eerkens, J.W.

    1979-01-01

    A method of isotope separation is described which involves the use of a laser photon beam to selectively induce energy level transitions of an isotope molecule containing the isotope to be separated. The use of the technique for 235 U enrichment is demonstrated. (UK)

  10. Cortical laminar necrosis in dengue encephalitis-a case report.

    Science.gov (United States)

    Garg, Ravindra Kumar; Rizvi, Imran; Ingole, Rajan; Jain, Amita; Malhotra, Hardeep Singh; Kumar, Neeraj; Batra, Dhruv

    2017-04-20

    Dengue encephalitis is a rare neurological manifestation of dengue fever. Its clinical presentation is similar to other viral encephalitides and encephalopathy. No single specific finding on magnetic resonance imaging of dengue encephalitis has yet been documented. They are highly variable and atypical. A 15-year boy presented with fever, the headache and altered sensorium of 12-day duration. On neurological examination, his Glasgow Coma Scale score was 10 (E3M4V3). There was no focal neurological deficit. Laboratory evaluation revealed leukopenia and marked thrombocytopenia. Dengue virus IgM antibody was positive both in serum and cerebrospinal fluid. Magnetic resonance imaging of the brain revealed signal changes in bilateral parietooccipital and left frontal regions (left hemisphere more involved than the right hemisphere). There was gyriform enhancement bilateral parietooccipital regions consistent with cortical laminar necrosis. Bilaterally diffuse subcortical white matter was also involved and subtle T2 hyperintensity involving both basal ganglia was noted. Gradient echo sequence revealed presence of hemorrhage in the subcortical white matter. Patient was treated conservatively and received platelet transfusion. Patient became fully conscious after 7 days. In a patient with highly suggestive dengue e\\ephalitis, we describe an unusual magnetic resonance imaging finding. This report is possibly the first instance of cortical laminar necrosis in such a setting.

  11. Laminar burning velocities of acetone in air at room and elevated temperatures

    NARCIS (Netherlands)

    Nilsson, E.J.K.; Goey, de L.P.H.; Konnov, A.

    2013-01-01

    Laminar burning velocities of acetone + air mixtures at initial gas mixture temperatures of 298, 318, 338 and 358 K are reported. Non-stretched flames were stabilized on a perforated plate burner at 1 atm, and laminar burning velocities were determined using the heat flux method, at conditions where

  12. Do NiTi instruments show defects before separation? Defects caused by torsional fatigue in hand and rotary nickel-titanium (NiTi) instruments which lead to failure during clinical use.

    Science.gov (United States)

    Chakka, N V Murali Krishna; Ratnakar, P; Das, Sanjib; Bagchi, Anandamy; Sudhir, Sudhir; Anumula, Lavanya

    2012-11-01

    Visual and microscopic evaluation of defects caused by torsional fatigue in hand and rotary nickel titanium (NiTi) instruments. Ninety-six NiTi greater taper instruments which were routinely used for root canal treatment only in anterior teeth were selected for the study. The files taken include ProTaper for hand use, ProTaper Rotary files and Endowave rotary files. After every use, the files were observed visually and microscopically (Stereomicroscope at 10×) to evaluate the defects caused by torsional fatigue. Scoring was given according to a new classification formulated which gives an indication of the severity of the defect or damage. Data was statistically analyzed using KruskallWallis and Mann-Whitney U test. Number of files showing defects were more under stereomicroscope than visual examination. But, the difference in the evaluation methods was not statistically significant. The different types of defects observed were bent instrument, straightening/stretching of twist contour and partial reverse twisting. Endowave files showed maximum number of defects followed by ProTaper for hand use and least in ProTaper Rotary. Visible defects due to torsional fatigue do occur in NiTi instruments after clinical use. Both visual and microscopic examinations were efficient in detecting defects caused due to torsional fatigue. This study emphasizes that all files should be observed for any visible defects before and after every instrumentation cycle to minimize the risk of instrument separation and failure of endodontic therapy.

  13. Applications of Laminar Weak-Link Mechanisms for Ultraprecision Synchrotron Radiation Instruments

    International Nuclear Information System (INIS)

    Shu, D.; Toellner, T. S.; Alp, E. E.; Maser, J.; Ilavsky, J.; Shastri, S. D.; Lee, P. L.; Narayanan, S.; Long, G. G.

    2007-01-01

    Unlike traditional kinematic flexure mechanisms, laminar overconstrained weak-link mechanisms provide much higher structure stiffness and stability. Using a laminar structure configured and manufactured by chemical etching and lithography techniques, we are able to design and build linear and rotary weak-link mechanisms with ultrahigh positioning sensitivity and stability for synchrotron radiation applications. Applications of laminar rotary weak-link mechanism include: high-energy-resolution monochromators for inelastic x-ray scattering and x-ray analyzers for ultra-small-angle scattering and powder-diffraction experiments. Applications of laminar linear weak-link mechanism include high-stiffness piezo-driven stages with subnanometer resolution for an x-ray microscope. In this paper, we summarize the recent designs and applications of the laminar weak-link mechanisms at the Advanced Photon Source

  14. Application of laminar flow control to high-bypass-ratio turbofan engine nacelles

    Science.gov (United States)

    Wie, Y. S.; Collier, F. S., Jr.; Wagner, R. D.

    1991-01-01

    Recently, the concept of the application of hybrid laminar flow to modern commercial transport aircraft was successfully flight tested on a Boeing 757 aircraft. In this limited demonstration, in which only part of the upper surface of the swept wing was designed for the attainment of laminar flow, significant local drag reduction was measured. This paper addresses the potential application of this technology to laminarize the external surface of large, modern turbofan engine nacelles which may comprise as much as 5-10 percent of the total wetted area of future commercial transports. A hybrid-laminar-flow-control (HLFC) pressure distribution is specified and the corresponding nacelle geometry is computed utilizing a predictor/corrector design method. Linear stability calculations are conducted to provide predictions of the extent of the laminar boundary layer. Performance studies are presented to determine potential benefits in terms of reduced fuel consumption.

  15. CENTRIFUGAL SEPARATORS

    Science.gov (United States)

    Skarstrom, C.

    1959-03-10

    A centrifugal separator is described for separating gaseous mixtures where the temperature gradients both longitudinally and radially of the centrifuge may be controlled effectively to produce a maximum separation of the process gases flowing through. Tbe invention provides for the balancing of increases and decreases in temperature in various zones of the centrifuge chamber as the result of compression and expansions respectively, of process gases and may be employed effectively both to neutralize harmful temperature gradients and to utilize beneficial temperaturc gradients within the centrifuge.

  16. Microparticle Separation by Cyclonic Separation

    Science.gov (United States)

    Karback, Keegan; Leith, Alexander

    2017-11-01

    The ability to separate particles based on their size has wide ranging applications from the industrial to the medical. Currently, cyclonic separators are primarily used in agriculture and manufacturing to syphon out contaminates or products from an air supply. This has led us to believe that cyclonic separation has more applications than the agricultural and industrial. Using the OpenFoam computational package, we were able to determine the flow parameters of a vortex in a cyclonic separator in order to segregate dust particles to a cutoff size of tens of nanometers. To test the model, we constructed an experiment to separate a test dust of various sized particles. We filled a chamber with Arizona test dust and utilized an acoustic suspension technique to segregate particles finer than a coarse cutoff size and introduce them into the cyclonic separation apparatus where they were further separated via a vortex following our computational model. The size of the particles separated from this experiment will be used to further refine our model. Metropolitan State University of Denver, Colorado University of Denver, Dr. Randall Tagg, Dr. Richard Krantz.

  17. Isotopic separation

    International Nuclear Information System (INIS)

    Castle, P.M.

    1979-01-01

    This invention relates to molecular and atomic isotope separation and is particularly applicable to the separation of 235 U from other uranium isotopes including 238 U. In the method described a desired isotope is separated mechanically from an atomic or molecular beam formed from an isotope mixture utilising the isotropic recoil momenta resulting from selective excitation of the desired isotope species by radiation, followed by ionization or dissociation by radiation or electron attachment. By forming a matrix of UF 6 molecules in HBr molecules so as to collapse the V 3 vibrational mode of the UF 6 molecule the 235 UF 6 molecules are selectively excited to promote reduction of UF 6 molecules containing 235 U and facilitate separation. (UK)

  18. Isotopic separation

    International Nuclear Information System (INIS)

    Chen, C.L.

    1979-01-01

    Isotopic species in an isotopic mixture including a first species having a first isotope and a second species having a second isotope are separated by selectively exciting the first species in preference to the second species and then reacting the selectively excited first species with an additional preselected radiation, an electron or another chemical species so as to form a product having a mass different from the original species and separating the product from the balance of the mixture in a centrifugal separating device such as centrifuge or aerodynamic nozzle. In the centrifuge the isotopic mixture is passed into a rotor where it is irradiated through a window. Heavier and lighter components can be withdrawn. The irradiated mixture experiences a large centrifugal force and is separated in a deflection area into lighter and heavier components. (UK)

  19. Separations chemistry

    International Nuclear Information System (INIS)

    Anon.

    1976-01-01

    Results of studies on the photochemistry of aqueous Pu solutions and the stability of iodine in liquid and gaseous CO 2 are reported. Progress is reported in studies on: the preparation of macroporous bodies filled with oxides and sulfides to be used as adsorbents; the beneficiation of photographic wastes; the anion exchange adsorption of transition elements from thiosulfate solutions; advanced filtration applications of energy significance; high-resolution separations; and, the examination of the separation agents, octylphenylphosphoric acid (OPPA) and trihexyl phosphate (THP)

  20. Isotopic separation

    International Nuclear Information System (INIS)

    Chen, C.L.

    1982-01-01

    A method is described for separating isotopes in which photo-excitation of selected isotope species is used together with the reaction of the excited species with postive ions of predetermined ionization energy, other excited species, or free electrons to produce ions or ion fragments of the selected species. Ions and electrons are produced by an electrical discharge, and separation is achieved through radial ambipolar diffusion, electrostatic techniques, or magnetohydrodynamic methods

  1. Laminar forced convection in a cylindrical collinear ohmic sterilizer

    Directory of Open Access Journals (Sweden)

    Pesso Tommaso

    2017-01-01

    Full Text Available The present work deals with a thermo-fluid analysis of a collinear cylindrical ohmic heater in laminar flow. The geometry of interest is a circular electrically insulated glass pipe with two electrodes at the pipe ends. For this application, since the electrical conductivity of a liquid food depends strongly on the temperature, the thermal analysis of an ohmic heater requires the simultaneous solution of the electric and thermal fields. In the present work the analysis involves decoupling the previous fields by means of an iterative procedure. The thermal field has been calculated using an analytical solution, which leads to fast calculations for the temperature distribution in the heater. Some considerations of practical interest for the design are also given.

  2. F-16XL Ship #2 Laminar Flow Glove mounting

    Science.gov (United States)

    1995-01-01

    NASA's two-seat F-16XL research aircraft is shown in the modification hangar at NASA's Dryden Flight Research Center, Edwards, California, during installation of a titanium 'glove' on the upper surface of its modified left wing. The aircraft subsequently carried out a 13-month-long, 45-flight research program which investigated drawing off a small part of the boundary-layer air in order to provide laminar--or smooth--flow over a major portion of a wing flying at supersonic speeds. A turbo-compressor in the aircraft's fuselage provided suction to draw air through more than 10 million tiny laser-drilled holes in the glove via a manifold system employing 20 valves. Data obtained during the program could assist designers of future aircraft in developing a more efficient high-speed civil transport.

  3. Pressure drop coefficient of laminar Newtonian flow in axisymmetric diffusers

    International Nuclear Information System (INIS)

    Rosa, S.; Pinho, F.T.

    2006-01-01

    The laminar flow of Newtonian fluids in axisymmetric diffusers has been numerically investigated to evaluate the pressure-loss coefficient as a function of Reynolds number, diffusion angle and expansion ratio. The numerical simulations were carried out with a finite-volume based code using non-orthogonal collocated grids and second order accurate differencing schemes to discretize all terms of the transport equations. The calculations were carried out for Reynolds numbers between 2 and 200, diffusion angles from 0 deg. to 90 deg. and expansion ratios of 1.5 and 2 and the data are presented in tabular form and as correlations. A simplified 1D theoretical analysis helped explain the various contributions to the loss coefficient and its difference relative to the reversible pressure variation due to differences between the actual and fully developed friction losses, distortions of the velocity profiles and pressure non-uniformity upstream and downstream of the expansion section

  4. Pressure drop coefficient of laminar Newtonian flow in axisymmetric diffusers

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, S. [Escola Superior de Tecnologia e Gestao, Instituto Politecnico, Campus de Santa Apolonia, 5301-857 Braganca (Portugal)]. E-mail: srosa@ipb.pt; Pinho, F.T. [Centro de Estudos de Fenomenos de Transporte, DEM, Universidade do Minho, Campus de Azurem, 4800-058 Guimaraes (Portugal)]. E-mail: fpinho@fe.up.pt

    2006-04-15

    The laminar flow of Newtonian fluids in axisymmetric diffusers has been numerically investigated to evaluate the pressure-loss coefficient as a function of Reynolds number, diffusion angle and expansion ratio. The numerical simulations were carried out with a finite-volume based code using non-orthogonal collocated grids and second order accurate differencing schemes to discretize all terms of the transport equations. The calculations were carried out for Reynolds numbers between 2 and 200, diffusion angles from 0 deg. to 90 deg. and expansion ratios of 1.5 and 2 and the data are presented in tabular form and as correlations. A simplified 1D theoretical analysis helped explain the various contributions to the loss coefficient and its difference relative to the reversible pressure variation due to differences between the actual and fully developed friction losses, distortions of the velocity profiles and pressure non-uniformity upstream and downstream of the expansion section.

  5. Computer simulations of magnetic fluids in laminar pipe flows

    International Nuclear Information System (INIS)

    Ramos, D.M.; Cunha, F.R.; Sobral, Y.D.; Fontoura Rodrigues, J.L.A.

    2005-01-01

    Finite volume method is adapted to simulate momentum and magnetic coupled equations of a laminar magnetic fluid flow. An evolution equation is used to calculate the fluid magnetization. Pressure-driven flow under steady and oscillatory magnetic field is investigated. The magnetostatic limit of the Maxwell's equations is treated in terms of a Poisson equation numerically integrated. The SIMPLE algorithm is used to calculate the pressure-velocity coupling when the pressure field is not prescribed. Suitable boundary conditions for velocity, magnetization and field intensity on the pipe wall are described. Results are obtained for velocity and pressure response under several conditions of the identified physical parameters of the flow. The simulations are verified by comparing numerical results and asymptotic theory, and they show a very good agreement

  6. Cortical laminar necrosis in brain infarcts: serial MRI

    Energy Technology Data Exchange (ETDEWEB)

    Siskas, N.; Lefkopoulos, A.; Ioannidis, I.; Charitandi, A.; Dimitriadis, A.S. [Radiology Department, AHEPA University Hospital, Aristotele University of Thessaloniki (Greece)

    2003-05-01

    High-signal cortical lesions are observed on T1-weighted images in cases of brain infarct. Histological examination has demonstrated these to be ''cortical laminar necrosis'', without haemorrhage or calcification. We report serial MRI in this condition in 12 patients with brain infarcts. We looked at high-signal lesions on T1-weighted images, chronological changes in signal intensity and contrast enhancement. High-signal cortical lesions began to appear about 2 weeks after the ictus, were prominent at 1 - 2 months, then became less evident, but occasionally remained for up to 1.5 years. They gave high signal or were isointense on T2-weighted images and did not give low signal at any stage. Contrast enhancement of these lesions was prominent at 1 - 2 months, and less apparent from 3 months, but was seen up to 5 months. (orig.)

  7. Sensitivity analysis of time-dependent laminar flows

    International Nuclear Information System (INIS)

    Hristova, H.; Etienne, S.; Pelletier, D.; Borggaard, J.

    2004-01-01

    This paper presents a general sensitivity equation method (SEM) for time dependent incompressible laminar flows. The SEM accounts for complex parameter dependence and is suitable for a wide range of problems. The formulation is verified on a problem with a closed form solution obtained by the method of manufactured solution. Systematic grid convergence studies confirm the theoretical rates of convergence in both space and time. The methodology is then applied to pulsatile flow around a square cylinder. Computations show that the flow starts with symmetrical vortex shedding followed by a transition to the traditional Von Karman street (alternate vortex shedding). Simulations show that the transition phase manifests itself earlier in the sensitivity fields than in the flow field itself. Sensitivities are then demonstrated for fast evaluation of nearby flows and uncertainty analysis. (author)

  8. Heat transfer in laminar flow for a finned double - tube

    International Nuclear Information System (INIS)

    Colle, S.

    1977-01-01

    An analitical study of the steady-state heat transfer in laminar flow in finned double-tube heat exchangers is presented. The fins are plane, straight and continous, equally spaced and are fixed over the external surface of the inner tube. A constant peripheral temperature distribution is assumed to apply over the inner tube surface and each fin, and a constant peripheral heat flux is assumed to apply over the outer tube surface, while the overall heat flux is suposed to be uniform in the longitudinal direction of the duct. The prediction of the thermal performance of the finned double-tube is made by means of the relationship between the Nusselt number, the boundary conditions and the geometric characteristcs of the duct. (author) [pt

  9. Postfragmentation density function for bacterial aggregates in laminar flow.

    Science.gov (United States)

    Byrne, Erin; Dzul, Steve; Solomon, Michael; Younger, John; Bortz, David M

    2011-04-01

    The postfragmentation probability density of daughter flocs is one of the least well-understood aspects of modeling flocculation. We use three-dimensional positional data of Klebsiella pneumoniae bacterial flocs in suspension and the knowledge of hydrodynamic properties of a laminar flow field to construct a probability density function of floc volumes after a fragmentation event. We provide computational results which predict that the primary fragmentation mechanism for large flocs is erosion. The postfragmentation probability density function has a strong dependence on the size of the original floc and indicates that most fragmentation events result in clumps of one to three bacteria eroding from the original floc. We also provide numerical evidence that exhaustive fragmentation yields a limiting density inconsistent with the log-normal density predicted in the literature, most likely due to the heterogeneous nature of K. pneumoniae flocs. To support our conclusions, artificial flocs were generated and display similar postfragmentation density and exhaustive fragmentation. ©2011 American Physical Society

  10. Laminar resorption in modified osteo-odonto-keratoprosthesis procedure: a cause for concern.

    Science.gov (United States)

    Iyer, Geetha; Srinivasan, Bhaskar; Agarwal, Shweta; Rachapalle, Sudhir Reddi

    2014-08-01

    To analyze the cases of lamina resorption following the modified osteo-odonto-keratoprosthesis (MOOKP) procedure. Retrospective case series. Case records of 18 eyes (20 laminae) of 17 patients who showed evidence of lamina resorption out of the 85 eyes (87 laminae) of 82 patients that underwent MOOKP procedure between March 2003 and March 2013 were analyzed. Of the 17 patients (20 laminae), 1 underwent MOOKP procedure following multiple graft failures, 6 (7 laminae) belonged to the chemical injury group, and 10 (12 laminae) to the Stevens-Johnson syndrome (SJS) group. Resorption was noted in 20 out of 87 laminae (22.98%). The need for removal of lamina/extrusion was noted in 3 out of the 7 laminae in the chemical injury group and 8 out of the 12 laminae in the SJS group. The mean duration to the first sign suggestive of resorption among patients of SJS was 36.7 months and among patients of chemical injury was 43 months. Vitritis was the presenting feature (7 of 20 laminae, 35%) indicative of early resorption, and the occurrence of the same in eyes with lamina resorption was noted to be statistically significant in comparison to controls (P<.001). Sixteen out of 20 laminae showed evidence of resorption superiorly. Vitritis was the most common presenting feature of lamina resorption and could be an indicator of lamina resorption. Resorption of the laminae was noted to occur along the aspect with thinner bone support in all eyes. Incidence of severe resorption with extrusion of cylinder/requiring lamina removal was noted to be higher among patients with SJS. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Heat and mass transfer caused by a laminar channel flow equipped with a synthetic jet array

    Czech Academy of Sciences Publication Activity Database

    Trávníček, Zdeněk; Dančová, Petra; Kordík, Jozef; Vít, Tomáš; Pavelka, Miroslav

    2011-01-01

    Roč. 2, č. 4 (2011), 041006-041006 ISSN 1948-5085 R&D Projects: GA AV ČR(CZ) IAA200760801; GA ČR(CZ) GA101/09/1959 Institutional research plan: CEZ:AV0Z20760514 Keywords : synthetic jet * flow control * naphthalene sublimation Subject RIV: BK - Fluid Dynamics http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JTSEBV000002000004041006000001&idtype=cvips&gifs=yes

  12. The Role of Separation Bubbles on the Aerodynamic Characteristics of Airfoils, Including Stall and Post-Stall, at Low Reynolds Numbers

    Science.gov (United States)

    Chen, Hsun H.; Cebeci, Tuncer

    2007-01-01

    Airfoils at high Reynolds numbers, in general, have small separation bubbles that are usually confined to the leading edge. Since the Reynolds number is large, the turbulence model for the transition region between the laminar and turbulent flow is not important. Furthermore, the onset of transition occurs either at separation or prior to separation and can be predicted satisfactorily by empirical correlations when the incident angle is small and can be assumed to correspond to laminar separation when the correlations do not apply, i.e., at high incidence angles.

  13. Separation system

    International Nuclear Information System (INIS)

    Rubin, L.S.

    1986-01-01

    A disposal container is described for use in disposal of radioactive waste materials consisting of: top wall structure, bottom wall structure, and circumferential side wall structure interconnecting the top and bottom wall structures to define an enclosed container, separation structure in the container adjacent the inner surface of the side wall structure for allowing passage of liquid and retention of solids, inlet port structure in the top wall structure, discharge port structure at the periphery of the container in communication with the outer surface of the separation structure for receiving liquid that passes through the separation structure, first centrifugally actuated valve structure having a normal position closing the inlet port structure and a centrifugally actuated position opening the inlet port structure, second centrifugally actuated valve structure having a normal position closing the discharge port structure and a centrifugally actuated position opening the discharge port structure, and coupling structure integral with wall structure of the container for releasable engagement with centrifugal drive structure

  14. Separable algebras

    CERN Document Server

    Ford, Timothy J

    2017-01-01

    This book presents a comprehensive introduction to the theory of separable algebras over commutative rings. After a thorough introduction to the general theory, the fundamental roles played by separable algebras are explored. For example, Azumaya algebras, the henselization of local rings, and Galois theory are rigorously introduced and treated. Interwoven throughout these applications is the important notion of étale algebras. Essential connections are drawn between the theory of separable algebras and Morita theory, the theory of faithfully flat descent, cohomology, derivations, differentials, reflexive lattices, maximal orders, and class groups. The text is accessible to graduate students who have finished a first course in algebra, and it includes necessary foundational material, useful exercises, and many nontrivial examples.

  15. Mapeamento do potencial de erosão laminar na bacia do rio Japaratuba, SE, via SIG Mapping the laminar erosion potential for the Japaratuba river basin, SE via GIS

    Directory of Open Access Journals (Sweden)

    Ricardo de Aragão

    2011-07-01

    Full Text Available A erosão do solo é a principal causa do empobrecimento precoce de terras produtivas e dentre as suas formas está a erosão laminar. Esta se caracteriza não apenas pela remoção de uma camada relativamente uniforme da superfície, mas também por seus nutrientes, sendo intensificada, portanto, pelas ações antrópicas. Para evitar ou reduzir seus impactos, fazem-se necessárias diretrizes para a adequação do uso e da ocupação às condições de cobertura vegetal, tipo de solo e topografia, através de mapas do potencial erosivo laminar da região de interesse, obtidos via sistemas de informações geográficas (SIG. Neste trabalho foi desenvolvido o mapeamento do potencial erosivo laminar da bacia do rio Japaratuba, SE (1685 km²; trata-se de uma região sujeita a intensa atividade agrícola, pecuária e de mineração, onde só restam 6% da vegetação nativa. Os resultados mostram que 48,71% da área da bacia ficam nas classes de médio e alto potencial erosivo, indicando que a bacia está bastante impactada devido aos usos inadequados para as condições de solo e declividades.Soil erosion is a natural phenomenon that reduces soil fertility and causes a great impact on agricultural areas. Laminar erosion is characterized by the removal of the top soil fairly uniformly as well as its nutrients, which is accelerated by human activities. To minimize the impacts it is necessary to adopt an adequate soil management that takes into account the type of the soil, relief, and vegetation cover. The soil management can be aided by mapping the erosive potential of a region using GIS tools. In this work, the technique that was used for mapping the erosive potential in the Japaratuba River Basin (1685 km² located in the State of Sergipe is presented. The results show that 48.71% of the basin area lie within medium and high erosive potentials zones, suggesting the inadequate land use for the soil types and relief within the basin.

  16. Isotope separation

    International Nuclear Information System (INIS)

    Bartlett, R.J.; Morrey, J.R.

    1978-01-01

    A method and apparatus is described for separating gas molecules containing one isotope of an element from gas molecules containing other isotopes of the same element in which all of the molecules of the gas are at the same electronic state in their ground state. Gas molecules in a gas stream containing one of the isotopes are selectively excited to a different electronic state while leaving the other gas molecules in their original ground state. Gas molecules containing one of the isotopes are then deflected from the other gas molecules in the stream and thus physically separated

  17. A numerical investigation of the impact of surface topology on laminar boundary layers

    Science.gov (United States)

    Beratlis, Nikolaos; Squires, Kyle; Balaras, Elias

    2015-11-01

    Surface topology, such as dimples or trip wires, has been utilized in the past for passive separation control over bluff bodies. The majority of the work, however, has focused on the indirect effects on the drag and lift forces, while the details of the impact on the boundary layer evolution are not well understood. Here we report a series of DNS of flow over a single row of spherical and hexagonal dimples, as well as, circular grooves. The Reynolds number and the thickness of the incoming laminar boundary layer is carefully controlled. In all cases transition to turbulence downstream of the elements comes with reorientation of the spanwise vorticity into hairpin like vortices. Although qualitatively the transition mechanism amongst different dimples and grooves is similar, important quantitative differences exist: two-dimensional geometries such as the groove, are more stable than three-dimensional geometries. In addition, it was found that the cavity geometry controls the initial thickness of the boundary layer and practically results in a shift of the virtual origin of the turbulent boundary layer. Important differences in the momentum transport downstream of the dimples exist, but in all cases the boundary layer evolves in a self-similar manner.

  18. Method and apparatus for the separation of solid particles having different densities

    NARCIS (Netherlands)

    Rem, P.C.; Berkhout, S.P.M.

    2011-01-01

    A method and apparatus for separating solid particles of different densities, using a magnetic process fluid. The solid particles are thoroughly mixed in a small partial flow of the process fluid. The small turbulent partial flow is added to a large laminar partial flow of the process fluid, after

  19. The evaluation of hierarchical structured superhydrophobic coatings for the alleviation of insect residue to aircraft laminar flow surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kok, Mariana [Department of Mechanical, Aeronautical and Biomedical Engineering, University of Limerick, Limerick (Ireland); Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Young, Trevor M., E-mail: Trevor.Young@ul.ie [Department of Mechanical, Aeronautical and Biomedical Engineering, University of Limerick, Limerick (Ireland); Materials and Surface Science Institute, University of Limerick, Limerick (Ireland)

    2014-09-30

    Surface contamination caused by insects on laminar flow wing surfaces causes a disruption of the flow, resulting in an increase in drag and fuel consumption. Consequently, the use of superhydrophobic coatings to mitigate insect residue adhesion was investigated. A range of hierarchical superhydrophobic coatings with different surface chemistry and topography was examined. Candidate coatings were characterized in terms of their morphology and hydrophobic properties by scanning electron microscopy (SEM) and static and dynamic contact angle measurements, respectively. Arithmetic mean surface roughness (R{sub a}) values were measured using profilometry. Only superhydrophobic coatings with a specific topography showed complete mitigation against insect residue adhesion. A surface which exhibited a specific microstructure (R{sub a} = 5.26 μm) combined with a low sliding angle (SA = 7.6°) showed the best anti-contamination properties. The dynamics of an insect impact event and its influence on the wetting and adhesion mechanisms of insect residue to a surface were discussed.

  20. Proposal for the study of laminar relativistic electron beam generation by a foilless diode

    International Nuclear Information System (INIS)

    Jones, M.E.; Thode, L.E.

    1979-02-01

    The continuation of an analytical and numerical study of intense relativistic electron beam generation by foilless diodes is proposed. The investigation is aimed at optimizing the diode design to produce a laminar flow

  1. Laminar Boundary-Layer Instabilities on Hypersonic Cones: Computations for Benchmark Experiments

    National Research Council Canada - National Science Library

    Robarge, Tyler W; Schneider, Steven P

    2005-01-01

    .... The STABL code package and its PSE-Chem stability solver are used to compute first and second mode instabilities for both sharp and blunt cones at wind tunnel conditions, with laminar mean flows...

  2. Autoignited laminar lifted flames of methane/hydrogen mixtures in heated coflow air

    KAUST Repository

    Choi, Byungchul; Chung, Suk-Ho

    2012-01-01

    Autoignited lifted flame behavior in laminar jets of methane/hydrogen mixture fuels has been investigated experimentally in heated coflow air. Three regimes of autoignited lifted flames were identified depending on initial temperature and hydrogen

  3. Subcortical laminar heterotopia and lissencephaly in two families: a single X linked dominant gene.

    Science.gov (United States)

    Pinard, J M; Motte, J; Chiron, C; Brian, R; Andermann, E; Dulac, O

    1994-01-01

    Neuronal migration disorders can now be recognised by MRI. This paper reports two families in which the mothers had subcortical laminar heterotopia and four of their children had either similar heterotopia (two girls) or severe pachygyria or lissencephaly (two boys). Laminar heterotopia was more evident on MRI T2 weighted images. The patients had mild to severe epilepsy and mental retardation depending on the extent of cortical abnormalities. In these families, subcortical laminar heterotopia, pachygyria, and lissencephaly seem to share the same X linked or autosomal dominant gene. No chromosomal abnormalities, especially of chromosome 17, could be identified. For appropriate genetic counselling of the family of a child with lissencephaly or subcortical laminar heterotopia, MRI should be performed in parents or siblings with mental retardation or epilepsy. Images PMID:8057113

  4. Measurement of laminar burning velocities and Markstein lengths of diluted hydrogen-enriched natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Haiyan; Jiao, Qi; Huang, Zuohua; Jiang, Deming [State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Eng., Xi' an Jiaotong University (China)

    2009-01-15

    The laminar flame characteristics of natural gas-hydrogen-air-diluent gas (nitrogen/CO{sub 2}) mixtures were studied in a constant volume combustion bomb at various diluent ratios, hydrogen fractions and equivalence ratios. Both unstretched laminar burning velocity and Markstein length were obtained. The results showed that hydrogen fraction, diluent ratio and equivalence ratio have combined influence on laminar burning velocity and flame instability. The unstretched laminar burning velocity is reduced at a rate that is increased with the increase of the diluent ratio. The reduction effect of CO{sub 2} diluent gas is stronger than that of nitrogen diluent gas. Hydrogen-enriched natural gas with high hydrogen fraction can tolerate more diluent gas than that with low hydrogen fraction. Markstein length can either increase or decrease with the increase of the diluent ratio, depending on the hydrogen fraction of the fuel. (author)

  5. Electric fields effect on liftoff and blowoff of nonpremixed laminar jet flames in a coflow

    KAUST Repository

    Kim, Minkuk; Ryu, Seol; Won, Sanghee; Chung, Suk-Ho

    2010-01-01

    The stabilization characteristics of liftoff and blowoff in nonpremixed laminar jet flames in a coflow have been investigated experimentally for propane fuel by applying AC and DC electric fields to the fuel nozzle with a single

  6. An investigation of the effects of the propeller slipstream of a laminar wing boundary layer

    Science.gov (United States)

    Howard, R. M.; Miley, S. J.; Holmes, B. J.

    1985-01-01

    A research program is in progress to study the effects of the propeller slipstream on natural laminar flow. Flight and wind tunnel measurements of the wing boundary layer have been made using hot-film velocity sensor probes. The results show the boundary layer, at any given point, to alternate between laminar and turbulent states. This cyclic behavior is due to periodic external flow turbulence originating from the viscous wake of the propeller blades. Analytic studies show the cyclic laminar/turbulent boundary layer to result in a significantly lower wing section drag than a fully turbulent boundary layer. The application of natural laminar flow design philosophy yields drag reduction benefits in the slipstream affected regions of the airframe, as well as the unaffected regions.

  7. Electro-Magnetic Flow Control to Enable Natural Laminar Flow Wings

    Data.gov (United States)

    National Aeronautics and Space Administration — This research team has developed a solid-state electromagnetic device that, when embedded along the leading edge of an aircraft wing, can disrupt laminar air flow on...

  8. Laminar flow heat transfer studies in a twisted square duct for ...

    Indian Academy of Sciences (India)

    Department of Mechanical Engineering, Indian Institute of Technology,. Bombay 400 ... boundary conditions using commercially available software. ... Chang et al (1988) used numerical method to study laminar flow in a twisted elliptic tube for.

  9. A short remark on Stewart 1962 variational principle for laminar flow in a uniform duct

    Directory of Open Access Journals (Sweden)

    Liu Hong-Yan

    2016-01-01

    Full Text Available This paper concludes that Stewart 1962 variational principle for laminar flow in a uniform duct is for a differential-difference. Some generalized variational principles are elucidated with or without Stewart’s discrete treatment.

  10. Problems of making the laminar construction of the nuclear reactor safety hausing

    International Nuclear Information System (INIS)

    Ablewicz, Z.

    1980-01-01

    General specifications and operating conditions of a safety housing are followed by a characteristics of constructional materials and a description of basic problems connected with making the laminar structure of this housing. (author)

  11. Transport coefficients for laminar and turbulent flow through a four-cusp channel

    International Nuclear Information System (INIS)

    Souza Dutra, A. de; Parise, J.A.R.; Souza Mendes, P.R. de.

    1986-01-01

    The heat transfer coefficients for laminar and turbulent flow in a four-cusp channel were determined. A numerical solution was developed for laminar flow an and experimental study for turbulent flow was carried out. Systematic variations of the Reynolds number were done in the range 900-30000. The results show that the heat transfer coefficients for the four-cusp channel are much lower than the coefficients for the circular tube. (author) [pt

  12. Turbulence Modeling of Flows with Extensive Crossflow Separation

    Directory of Open Access Journals (Sweden)

    Argyris G. Panaras

    2015-07-01

    Full Text Available The reasons for the difficulty in simulating accurately strong 3-D shock wave/turbulent boundary layer interactions (SBLIs and high-alpha flows with classical turbulence models are investigated. These flows are characterized by the appearance of strong crossflow separation. In view of recent additional evidence, a previously published flow analysis, which attributes the poor performance of classical turbulence models to the observed laminarization of the separation domain, is reexamined. According to this analysis, the longitudinal vortices into which the separated boundary layer rolls up in this type of separated flow, transfer external inviscid air into the part of the separation adjacent to the wall, decreasing its turbulence. It is demonstrated that linear models based on the Boussinesq equation provide solutions of moderate accuracy, while non-linear ones and others that consider the particular structure of the flow are more efficient. Published and new Reynolds Averaged Navier–Stokes (RANS simulations are reviewed, as well as results from a recent Large Eddy Simulation (LES study, which indicate that in calculations characterized by sufficient accuracy the turbulent kinetic energy of the reverse flow inside the separation vortices is very low, i.e., the flow is almost laminar there.

  13. Gas separating

    Science.gov (United States)

    Gollan, A.

    1988-03-29

    Feed gas is directed tangentially along the non-skin surface of gas separation membrane modules comprising a cylindrical bundle of parallel contiguous hollow fibers supported to allow feed gas to flow from an inlet at one end of a cylindrical housing through the bores of the bundled fibers to an outlet at the other end while a component of the feed gas permeates through the fibers, each having the skin side on the outside, through a permeate outlet in the cylindrical casing. 3 figs.

  14. Isotope separation

    International Nuclear Information System (INIS)

    Rosevear, A.; Sims, H.E.

    1985-01-01

    sup(195m)Au for medical usage is separated from sup(195m)Hg in a solution containing ions of sup(195m)Hg by contacting the solution with an adsorbing agent to adsorb 195 Hgsup(H) thereon, followed by selective elution of sup(195m)Au generated by radioactive decay of the sup(195m)Hg. The adsorbing agent comprises a composite material in the form of an inert porous inorganic substrate (e.g. Kieselguhr),the pores of which are occupied by a hydrogel of a polysaccharide (e.g. agarose) carrying terminal thiol groups for binding Hgsup(H) ions. (author)

  15. Formation of free round jets with long laminar regions at large Reynolds numbers

    Science.gov (United States)

    Zayko, Julia; Teplovodskii, Sergey; Chicherina, Anastasia; Vedeneev, Vasily; Reshmin, Alexander

    2018-04-01

    The paper describes a new, simple method for the formation of free round jets with long laminar regions by a jet-forming device of ˜1.5 jet diameters in size. Submerged jets of 0.12 m diameter at Reynolds numbers of 2000-12 560 are experimentally studied. It is shown that for the optimal regime, the laminar region length reaches 5.5 diameters for Reynolds number ˜10 000 which is not achievable for other methods of laminar jet formation. To explain the existence of the optimal regime, a steady flow calculation in the forming unit and a stability analysis of outcoming jet velocity profiles are conducted. The shortening of the laminar regions, compared with the optimal regime, is explained by the higher incoming turbulence level for lower velocities and by the increase of perturbation growth rates for larger velocities. The initial laminar regions of free jets can be used for organising air curtains for the protection of objects in medicine and technologies by creating the air field with desired properties not mixed with ambient air. Free jets with long laminar regions can also be used for detailed studies of perturbation growth and transition to turbulence in round jets.

  16. Experimental study of transition from laminar to turbulent flow in vertical narrow channel

    International Nuclear Information System (INIS)

    Wang Chang; Gao Puzhen; Wang Zhanwei; Tan Sichao

    2012-01-01

    Highlights: ► The effect of wall heating on the laminar to turbulent transition is experimentally studied. ► The flow characteristic demonstrates that heating leads to the delay of transition from laminar to turbulent regimes. ► The heat transfer characteristics also indicates that heating leads to the delay of flow regime transition. - Abstract: Experimental investigation of flow and heat transfer characteristics of a vertical narrow channel with uniform heat flux condition are conducted to analysis the effect of wall heating on the laminar to turbulent transition. The friction factor in the heating condition is compared with that in the adiabatic condition and the results show that wall heating leads to the delay of laminar to turbulent transition. In addition, the heat transfer characteristic indicates that the critical Reynolds number at the point of laminar flow breakdown increases with the increase of fluid temperature difference, and the local Nusselt number at the point of laminar breakdown increases with the increase of the inlet Reynolds number. The analyses of the flow and heat transfer characteristics both indicate that the heating has a stabilizing effect on the water flow at present experimental scale.

  17. Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. II. Simulations

    Science.gov (United States)

    Schober, Jennifer; Rogachevskii, Igor; Brandenburg, Axel; Boyarsky, Alexey; Fröhlich, Jürg; Ruchayskiy, Oleg; Kleeorin, Nathan

    2018-05-01

    Using direct numerical simulations (DNS), we study laminar and turbulent dynamos in chiral magnetohydrodynamics with an extended set of equations that accounts for an additional contribution to the electric current due to the chiral magnetic effect (CME). This quantum phenomenon originates from an asymmetry between left- and right-handed relativistic fermions in the presence of a magnetic field and gives rise to a chiral dynamo. We show that the magnetic field evolution proceeds in three stages: (1) a small-scale chiral dynamo instability, (2) production of chiral magnetically driven turbulence and excitation of a large-scale dynamo instability due to a new chiral effect (α μ effect), and (3) saturation of magnetic helicity and magnetic field growth controlled by a conservation law for the total chirality. The α μ effect becomes dominant at large fluid and magnetic Reynolds numbers and is not related to kinetic helicity. The growth rate of the large-scale magnetic field and its characteristic scale measured in the numerical simulations agree well with theoretical predictions based on mean-field theory. The previously discussed two-stage chiral magnetic scenario did not include stage (2), during which the characteristic scale of magnetic field variations can increase by many orders of magnitude. Based on the findings from numerical simulations, the relevance of the CME and the chiral effects revealed in the relativistic plasma of the early universe and of proto-neutron stars are discussed.

  18. Response to acoustic forcing of laminar coflow jet diffusion flames

    KAUST Repository

    Chrystie, Robin

    2014-04-23

    Toward the goal of understanding and controlling instability in combustion systems, we present a fundamental characterization of the interaction of the buoyancy-induced instability in flickering flames with forced excitation of fuel supply. Laminar coflow diffusion flames were acoustically forced, whose frequency responses were recorded as a function of excitation frequency and amplitude. The evolving structure of such flames was also examined through the use of video analysis and particle imaging velocimetry (PIV). For specific combinations of excitation frequency and amplitude, the frequency response of the flames was found to couple to that of the forcing, where the contribution of natural puffing frequency disappears. Such instances of coupling exhibited many harmonics of the excitation frequency, related indirectly to the natural puffing frequency. We showed how such harmonics form, through application of PIV, and furthermore unveiled insight into the physics of how the flame couples to the forcing under certain conditions. Our frequency response characterization provides quantitative results, which are of utility for both modeling studies and active-control strategies. Copyright © Taylor & Francis Group, LLC.

  19. Frost Growth and Densification in Laminar Flow Over Flat Surfaces

    Science.gov (United States)

    Kandula, Max

    2011-01-01

    One-dimensional frost growth and densification in laminar flow over flat surfaces has been theoretically investigated. Improved representations of frost density and effective thermal conductivity applicable to a wide range of frost circumstances have been incorporated. The validity of the proposed model considering heat and mass diffusion in the frost layer is tested by a comparison of the predictions with data from various investigators for frost parameters including frost thickness, frost surface temperature, frost density and heat flux. The test conditions cover a range of wall temperature, air humidity ratio, air velocity, and air temperature, and the effect of these variables on the frost parameters has been exemplified. Satisfactory agreement is achieved between the model predictions and the various test data considered. The prevailing uncertainties concerning the role air velocity and air temperature on frost development have been elucidated. It is concluded that that for flat surfaces increases in air velocity have no appreciable effect on frost thickness but contribute to significant frost densification, while increase in air temperatures results in a slight increase the frost thickness and appreciable frost densification.

  20. Investigation of Hypersonic Laminar Heating Augmentation in the Stagnation Region

    Science.gov (United States)

    Marineau, Eric C.; Lewis, Daniel R.; Smith, Michael S.; Lafferty, John F.; White, Molly E.; Amar, Adam J.

    2012-01-01

    Laminar stagnation region heating augmentation is investigated in the AEDC Tunnel 9 at Mach 10 by performing high frequency surface pressure and heat transfer measurements on the Orion CEV capsule at zero degree angle-of-attack for unit Reynolds numbers between 0.5 and 15 million per foot. Heating augmentation increases with Reynolds number, but is also model size dependent as it is absent on a 1.25-inch diameter model at Reynolds numbers where it reaches up to 15% on a 7-inch model. Heat transfer space-time correlations on the 7-inch model show that disturbances convect at the boundary layer edge velocity and that the streamwise integral scale increases with distance. Therefore, vorticity amplification due to stretching and piling-up in the stagnation region appears to be responsible for the stagnation point heating augmentation on the larger model. This assumption is reinforced by the f(exp -11/3) dependence of the surface pressure spectrum compared to the f(exp -1) dependence in the free stream. Vorticity amplification does not occur on the 1.25- inch model because the disturbances are too large. Improved free stream fluctuation measurements will be required to determine if significant vorticity is present upstream or mostly generated behind the bow shock.

  1. Flamelet mathematical models for non-premixed laminar combustion

    Energy Technology Data Exchange (ETDEWEB)

    Carbonell, D.; Perez-Segarra, C.D.; Oliva, A. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), Colom 11, E-08222 Terrassa, Barcelona (Spain); Coelho, P.J. [Mechanical Engineering Department, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2009-02-15

    Detailed numerical calculations based on the solution of the full transport equations have been compared with flamelet calculations in order to analyse the flamelet concept for laminar diffusion flames. The goal of this work is to study the interactive (Lagrangian Flamelet Model and Interactive Steady Flamelet Model), and non-interactive (Steady Flamelet Model and Enthalpy Defect Flamelet Model) flamelet models considering both differential diffusion and non-differential diffusion situations, and adiabatic and non-adiabatic conditions. Moreover, a new procedure has been employed to obtain enthalpy defects in the flamelet library, the application of which has been found to be encouraging. The effect of using in-situ, local or stoichiometric scalar dissipation rate conditions, and also the effect of using local or stoichiometric conditions to evaluate the flamelet-like time has been analysed. To improve slow species predictions using the non-interactive models, their transport equations are solved with the reaction terms calculated from the flamelet library, also considering local or stoichiometric conditions in the so-called Extended Flamelet Models. (author)

  2. The formation of aromatics and PAH's in laminar flames

    International Nuclear Information System (INIS)

    Marinov, N M; Pitz, W J; Westbrook, C K

    1999-01-01

    The formation of aromatics and PAH's is an important problem in combustion. These compounds are believed to contribute to the formation of soot whose emission from diesel engines is regulated widely throughout the industrial world. Additionally, the United States Environmental Protection Agency regulates the emission of many aromatics and PAH species from stationary industrial burners, under the 1990 Clean Air Act Amendments. The above emission regulations have created much interest in understanding how these species are formed in combustion systems. Much previous work has been done on aromatics and PAH's. The work is too extensive to review here, but is reviewed in Reference 1. A few recent developments are highlighted here. McEnally, Pfefferle and coworkers have studied aromatic, PAH and soot formation in a variety of non-premixed flames with hydrocarbon additives[2-4]. They found additives that contain a C5 ring increase the concentration of aromatics and soot[4]. Howard and coworkers have studied the formation of aromatic and PAH's in low pressure, premixed, laminar hydrocarbon flames. They found the cyclopentadienyl radical to be a key species in naphthalene formation in a fuel-rich, benzene/Ar/O2 flame[5

  3. Direct numerical simulation of axisymmetric laminar low-density jets

    Science.gov (United States)

    Gomez Lendinez, Daniel; Coenen, Wilfried; Sevilla, Alejandro

    2017-11-01

    The stability of submerged laminar axisymmetric low-density jets has been investigated experimentally (Kyle & Sreenivasan 1993, Hallberg & Strykowski 2006) and with linear analysis (Jendoubi & Strykowski 1994, Coenen & Sevilla 2012, Coenen et al. 2017). These jets become globally unstable when the Reynolds number is larger than a certain critical value which depends on the density ratio and on the velocity profile at the injector outlet. In this work, Direct Numerical Simulations using FreeFEM + + (Hecht 2012) with P1 elements for pressure and P2 for velocity and density are performed to complement the above mentioned studies. Density and velocity fields are analyzed at long time showing the unforced space-time evolution of nonlinear disturbances propagating along the jet. Using the Stuart-Landau model to fit the numerical results for the self-excited oscillations we have computed a neutral stability curve that shows good agreement with experiments and stability theory. Thanks to Spanish MINECO under projects DPI2014-59292-C3-1-P and DPI2015-71901-REDT for financial support.

  4. A Laminar Organization for Selective Cortico-Cortical Communication

    Directory of Open Access Journals (Sweden)

    Rinaldo D. D’Souza

    2017-08-01

    Full Text Available The neocortex is central to mammalian cognitive ability, playing critical roles in sensory perception, motor skills and executive function. This thin, layered structure comprises distinct, functionally specialized areas that communicate with each other through the axons of pyramidal neurons. For the hundreds of such cortico-cortical pathways to underlie diverse functions, their cellular and synaptic architectures must differ so that they result in distinct computations at the target projection neurons. In what ways do these pathways differ? By originating and terminating in different laminae, and by selectively targeting specific populations of excitatory and inhibitory neurons, these “interareal” pathways can differentially control the timing and strength of synaptic inputs onto individual neurons, resulting in layer-specific computations. Due to the rapid development in transgenic techniques, the mouse has emerged as a powerful mammalian model for understanding the rules by which cortical circuits organize and function. Here we review our understanding of how cortical lamination constrains long-range communication in the mammalian brain, with an emphasis on the mouse visual cortical network. We discuss the laminar architecture underlying interareal communication, the role of neocortical layers in organizing the balance of excitatory and inhibitory actions, and highlight the structure and function of layer 1 in mouse visual cortex.

  5. Rheology of sediment transported by a laminar flow

    Science.gov (United States)

    Houssais, M.; Ortiz, C. P.; Durian, D. J.; Jerolmack, D. J.

    2016-12-01

    Understanding the dynamics of fluid-driven sediment transport remains challenging, as it occurs at the interface between a granular material and a fluid flow. Boyer, Guazzelli, and Pouliquen [Phys. Rev. Lett. 107, 188301 (2011)], 10.1103/PhysRevLett.107.188301 proposed a local rheology unifying dense dry-granular and viscous-suspension flows, but it has been validated only for neutrally buoyant particles in a confined and homogeneous system. Here we generalize the Boyer, Guazzelli, and Pouliquen model to account for the weight of a particle by addition of a pressure P0 and test the ability of this model to describe sediment transport in an idealized laboratory river. We subject a bed of settling plastic particles to a laminar-shear flow from above, and use refractive-index-matching to track particles' motion and determine local rheology—from the fluid-granular interface to deep in the granular bed. Data from all experiments collapse onto a single curve of friction μ as a function of the viscous number Iv over the range 3 ×10-5 ≤Iv≤2 , validating the local rheology model. For Ivcreeping regime where we observe a continuous decay of the friction coefficient μ ≤μs as Iv decreases. The rheology of this creep regime cannot be described by the local model, and more work is needed to determine whether a nonlocal rheology model can be modified to account for our findings.

  6. Building a Practical Natural Laminar Flow Design Capability

    Science.gov (United States)

    Campbell, Richard L.; Lynde, Michelle N.

    2017-01-01

    A preliminary natural laminar flow (NLF) design method that has been developed and applied to supersonic and transonic wings with moderate-to-high leading-edge sweeps at flight Reynolds numbers is further extended and evaluated in this paper. The modular design approach uses a knowledge-based design module linked with different flow solvers and boundary layer stability analysis methods to provide a multifidelity capability for NLF analysis and design. An assessment of the effects of different options for stability analysis is included using pressures and geometry from an NLF wing designed for the Common Research Model (CRM). Several extensions to the design module are described, including multiple new approaches to design for controlling attachment line contamination and transition. Finally, a modification to the NLF design algorithm that allows independent control of Tollmien-Schlichting (TS) and cross flow (CF) modes is proposed. A preliminary evaluation of the TS-only option applied to the design of an NLF nacelle for the CRM is performed that includes the use of a low-fidelity stability analysis directly in the design module.

  7. AC electric field induced vortex in laminar coflow diffusion flames

    KAUST Repository

    Xiong, Yuan; Cha, Min; Chung, Suk-Ho

    2014-01-01

    Experiments were performed by applying sub-critical high-voltage alternating current (AC) to the nozzle of laminar propane coflow diffusion flames. Light scattering, laser-induced incandescence and laser-induced fluorescence techniques were used to identify the soot zone, and the structures of OH and polycyclic aromatic hydrocarbons (PAHs). Particle image velocimetry was adopted to quantify the velocity field. Under certain AC conditions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered, leading to the formation of toroidal vortices. Increased residence time and heat recirculation inside the vortex resulted in appreciable formation of PAHs and soot near the nozzle exit. Decreased residence time along the jet axis through flow acceleration by the vortex led to a reduction in the soot volume fraction in the downstream sooting zone. Electromagnetic force generated by AC was proposed as a viable mechanism for the formation of the toroidal vortex. The onset conditions for the vortex formation supported the role of an electromagnetic force acting on charged particles in the flame zone. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  8. Dental imaging using laminar optical tomography and micro CT

    Science.gov (United States)

    Long, Feixiao; Ozturk, Mehmet S.; Intes, Xavier; Kotha, Shiva

    2014-02-01

    Dental lesions located in the pulp are quite difficult to identify based on anatomical contrast, and, hence, to diagnose using traditional imaging methods such as dental CT. However, such lesions could lead to functional and/or molecular optical contrast. Herein, we report on the preliminary investigation of using Laminar Optical Tomography (LOT) to image the pulp and root canals in teeth. LOT is a non-contact, high resolution, molecular and functional mesoscopic optical imaging modality. To investigate the potential of LOT for dental imaging, we injected an optical dye into ex vivo teeth samples and imaged them using LOT and micro-CT simultaneously. A rigid image registration between the LOT and micro-CT reconstruction was obtained, validating the potential of LOT to image molecular optical contrast deep in the teeth with accuracy, non-invasively. We demonstrate that LOT can retrieve the 3D bio-distribution of molecular probes at depths up to 2mm with a resolution of several hundred microns in teeth.

  9. AC electric field induced vortex in laminar coflow diffusion flames

    KAUST Repository

    Xiong, Yuan

    2014-09-22

    Experiments were performed by applying sub-critical high-voltage alternating current (AC) to the nozzle of laminar propane coflow diffusion flames. Light scattering, laser-induced incandescence and laser-induced fluorescence techniques were used to identify the soot zone, and the structures of OH and polycyclic aromatic hydrocarbons (PAHs). Particle image velocimetry was adopted to quantify the velocity field. Under certain AC conditions of applied voltage and frequency, the distribution of PAHs and the flow field near the nozzle exit were drastically altered, leading to the formation of toroidal vortices. Increased residence time and heat recirculation inside the vortex resulted in appreciable formation of PAHs and soot near the nozzle exit. Decreased residence time along the jet axis through flow acceleration by the vortex led to a reduction in the soot volume fraction in the downstream sooting zone. Electromagnetic force generated by AC was proposed as a viable mechanism for the formation of the toroidal vortex. The onset conditions for the vortex formation supported the role of an electromagnetic force acting on charged particles in the flame zone. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  10. Implementation of a correction factor for the Pohlhausen laminar boundary layer applied on the CEVA curved wall jet model

    Directory of Open Access Journals (Sweden)

    Valeriu DRAGAN

    2013-09-01

    Full Text Available Curved wall jets have many technical applications, ranging from aeronautical circulation controlled wings to micro-fluidics and cryogenics. This paper addresses the issue of correctly estimating the boundary layer separation for laminar curved wall jets. For this, the Pohlhausen model was used in conjunction with the CEVA wall jet model with a semi-empirical modification which increases the accuracy for very thin jets. The method is therefore a mix of analytical equations with curve fitted experimental data in order to produce a simple yet effective way of estimating the boundary layer velocity profile along the curved wall. In order to cross-check the results, Newman’s empirical equation – which only provides a separation location but no information regarding the velocity profile - for boundary layer separation was used with good results. The hereby model could be used as a pre-design tool for rapid assessment of aeronautical high-lift applications such as Upper Surface Blown (USB or entrainment wings.

  11. Hydrogen separation process

    Science.gov (United States)

    Mundschau, Michael [Longmont, CO; Xie, Xiaobing [Foster City, CA; Evenson, IV, Carl; Grimmer, Paul [Longmont, CO; Wright, Harold [Longmont, CO

    2011-05-24

    A method for separating a hydrogen-rich product stream from a feed stream comprising hydrogen and at least one carbon-containing gas, comprising feeding the feed stream, at an inlet pressure greater than atmospheric pressure and a temperature greater than 200.degree. C., to a hydrogen separation membrane system comprising a membrane that is selectively permeable to hydrogen, and producing a hydrogen-rich permeate product stream on the permeate side of the membrane and a carbon dioxide-rich product raffinate stream on the raffinate side of the membrane. A method for separating a hydrogen-rich product stream from a feed stream comprising hydrogen and at least one carbon-containing gas, comprising feeding the feed stream, at an inlet pressure greater than atmospheric pressure and a temperature greater than 200.degree. C., to an integrated water gas shift/hydrogen separation membrane system wherein the hydrogen separation membrane system comprises a membrane that is selectively permeable to hydrogen, and producing a hydrogen-rich permeate product stream on the permeate side of the membrane and a carbon dioxide-rich product raffinate stream on the raffinate side of the membrane. A method for pretreating a membrane, comprising: heating the membrane to a desired operating temperature and desired feed pressure in a flow of inert gas for a sufficient time to cause the membrane to mechanically deform; decreasing the feed pressure to approximately ambient pressure; and optionally, flowing an oxidizing agent across the membrane before, during, or after deformation of the membrane. A method of supporting a hydrogen separation membrane system comprising selecting a hydrogen separation membrane system comprising one or more catalyst outer layers deposited on a hydrogen transport membrane layer and sealing the hydrogen separation membrane system to a porous support.

  12. Investigations of Sooting Laminar Coflow Diffusion Flames at Elevated Pressures

    KAUST Repository

    Steinmetz, Scott A.

    2016-12-01

    Soot is a common byproduct of hydrocarbon based combustion systems. It poses a risk to human and environmental health, and can negatively or positively affect combustor performance. As a result, there is significant interest in understanding soot formation in order to better control it. More recently, the need to study soot formation in engine relevant conditions has become apparent. One engine relevant parameter that has had little focus is the ambient pressure. This body of work focuses on the formation of soot in elevated pressure environments, and a number of investigations are carried out with this purpose. Laminar coflow diffusion flames are used as steady, simple soot producers. First, a commonly studied flame configuration is further characterized. Coflow flames are frequently used for fundamental flame studies, particularly at elevated pressures. However, they are more susceptible to buoyancy induced instabilities at elevated pressures. The velocity of the coflow is known to have an effect on flame stability and soot formation, though these have not been characterized at elevated pressures. A series of flames are investigated covering a range of flowrates, pressures, and nozzle diameters. The stability limits of coflow flames in this range is investigated. Additionally, an alternative strategy for scaling these flames to elevated pressures is proposed. Finally, the effect of coflow rate on soot formation is evaluated. Identification of fundamental flames for coordinated research can facilitate our understanding of soot formation. The next study of this work focuses on adding soot concentration and particle size information to an existing fundamental flame dataset for the purpose of numerical model validation. Soot volume fraction and average particle diameters are successfully measured in nitrogen-diluted ethylene-air laminar coflow flames at pressures of 4, 8, 12, and 16 atm. An increase in particle size with pressure is found up to 12 atm, where particle

  13. Laminar Mixed Convection Heat Transfer Correlation for Horizontal Pipes

    International Nuclear Information System (INIS)

    Chae, Myeong Seon; Chung, Bum Jin

    2013-01-01

    This study aimed at producing experimental results and developing a new heat transfer correlation based upon a semi-empirical buoyancy coefficient. Mixed convection mass transfers inside horizontal pipe were investigated for the pipe of various length-to-diameters with varying Re. Forced convection correlation was developed using a very short cathode. With the length of cathode increase and Re decrease, the heat transfer rates were enhanced and becomes higher than that of forced convection. An empirical buoyancy coefficient was derived from correlation of natural convection and forced convection with the addition of L/D. And the heat transfer correlation for laminar mixed convection was developed using the buoyancy coefficient, it describes not only current results, but also results of other studies. Mixed convection occurs when the driving forces of both forced and natural convections are of comparable magnitude (Gr/Re 2 ∼1). It is classical problem but is still an active area of research for various thermal applications such as flat plate solar collectors, nuclear reactors and heat exchangers. The effect of buoyancy on heat transfer in a forced flow is varied by the direction of the buoyancy force. In a horizontal pipe the direction of the forced and buoyancy forces are perpendicular. The studies on the mixed convections of the horizontal pipes were not investigated very much due to the lack of practical uses compared to those of vertical pipes. Even the definitions on the buoyancy coefficient that presents the relative influence of the forced and the natural convections, are different by scholars. And the proposed heat transfer correlations do not agree

  14. Cálculo no lineal de estructuras reticuladas y laminares

    Directory of Open Access Journals (Sweden)

    Ortiz Herrera, Jesús

    1976-02-01

    Full Text Available By many of electronic calculus it is possible to approach the non linear analysis of bar constructions efficiently and without the limitations of the traditional plastic Calculus. In order to prove this statement, the author presents certains structural analysis that have been carried out by means of techniques and calculation programs of his own. Further, the non linear analysis of revolving sheets is presented to which algorithms of great formal similarity to those in the case of bar constructions are applicable. Both for these latter ones as weil as for laminated structures the programs elaborated by the author allow a great variety of anelastic analyses (and as a special case, of elastic analysis.Con la ayuda del cálculo electrónico, el análisis no lineal de estructuras de barras es abordable con eficiencia y sin caer en las limitaciones del cálculo plástico tradicional. Con objeto de probar esta afirmación, se presentan determinados análisis estructurales realizados mediante técnicas y programas de cálculo propios. Se presenta asimismo el análisis no lineal de láminas de revolución, a las cuales son aplicables algoritmos de gran similitud formal con los del caso de estructuras de barras. Tanto para estas últimas como para las estructuras laminares, los programas desarrollados por el autor permiten efectuar gran variedad de análisis inelásticos (y elásticos como caso particular.

  15. Separations chemistry

    International Nuclear Information System (INIS)

    Anon.

    1977-01-01

    Infrared spectra of Pu(IV) polymer show effects of CO 2 adsorption and of aging. Uv light (300 nm) increases the rate of reduction of PuO 2 2+ and Pu 4+ to Pu 3+ and the Pu--U separation factor using TBP. Distribution ratios for Zr and Hf between Dowex 50W--X8 resin and H 2 SO 4 solutions were found to decrease sharply with H 2 SO 4 content. Octylphenyl acid phosphate, a mixture of monooctylphenyl and dioctylphenyl phosphoric acids, is being studied for U recovery from wet-process phosphoric acid. A study of HNO 3 leaching of Ra from U ores was completed. Effects of particle size of the packed bed on the dispersion of the boundary of the miscible phase used in oil recovery are being studied. Effects of sulfonates on toluene--n-butanol--water phase relations were determined, as were the effects of salts and solutes on the max water content of 1:1 toluene--alcohol solutions. A study was begun of hydrocarbon solubility in water--surfactant--alcohol. The mechanism of the formation of hydrous ZrO 2 --polyacrylate membranes and their use for sulfate rejection were studied. Salt rejection through hyperfiltration by clay membranes (bentonite and kaolin) was also investigated. Preliminary results are given for hyperfiltration of wood-pulping wastes by ZrO 2 membranes. 13 figures

  16. Neurochemical, morphologic, and laminar characterization of cortical projection neurons in the cingulate motor areas of the macaque monkey

    Science.gov (United States)

    Nimchinsky, E. A.; Hof, P. R.; Young, W. G.; Morrison, J. H.; Bloom, F. E. (Principal Investigator)

    1996-01-01

    The primate cingulate gyrus contains multiple cortical areas that can be distinguished by several neurochemical features, including the distribution of neurofilament protein-enriched pyramidal neurons. In addition, connectivity and functional properties indicate that there are multiple motor areas in the cortex lining the cingulate sulcus. These motor areas were targeted for analysis of potential interactions among regional specialization, connectivity, and cellular characteristics such as neurochemical profile and morphology. Specifically, intracortical injections of retrogradely transported dyes and intracellular injection were combined with immunocytochemistry to investigate neurons projecting from the cingulate motor areas to the putative forelimb region of the primary motor cortex, area M1. Two separate groups of neurons projecting to area M1 emanated from the cingulate sulcus, one anterior and one posterior, both of which furnished commissural and ipsilateral connections with area M1. The primary difference between the two populations was laminar origin, with the anterior projection originating largely in deep layers, and the posterior projection taking origin equally in superficial and deep layers. With regard to cellular morphology, the anterior projection exhibited more morphologic diversity than the posterior projection. Commissural projections from both anterior and posterior fields originated largely in layer VI. Neurofilament protein distribution was a reliable tool for localizing the two projections and for discriminating between them. Comparable proportions of the two sets of projection neurons contained neurofilament protein, although the density and distribution of the total population of neurofilament protein-enriched neurons was very different in the two subareas of origin. Within a projection, the participating neurons exhibited a high degree of morphologic heterogeneity, and no correlation was observed between somatodendritic morphology and

  17. The blow-off mechanism of a bluff-body stabilized laminar premixed flame

    KAUST Repository

    Kedia, Kushal S.

    2015-04-01

    © 2014 The Combustion Institute. The objective of this work is to investigate the dynamics leading to blow-off of a laminar premixed flame stabilized on a confined bluff-body using high fidelity numerical simulations. We used unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. The flame-wall interaction between the hot reactants and the heat conducting bluff-body was accurately captured by incorporating the conjugate heat exchange between them. Simulations showed a shear-layer stabilized flame just downstream of the bluff-body, with a recirculation zone formed by the products of combustion. The flame was negatively stretched along its entire length, primarily dominated by the normal component of the strain. Blow-off was approached by decreasing the mixture equivalence ratio, at a fixed Reynolds number, of the incoming flow. A flame is stable (does not undergo blow-off) when (1) flame displacement speed is equal to the flow speed and (2) the gradient of the flame displacement speed normal to its surface is higher than the gradient of the flow speed along the same direction. As the equivalence ratio is reduced, the difference between the former and the latter shrinks until the dynamic stability condition (2) is violated, leading to blow-off. Blow-off initiates at a location where this is first violated along the flame. Our results showed that this location was far downstream from the flame anchoring zone, near the end of the recirculation zone. Blow-off started by flame pinching separating the flame into an upstream moving (carried within the recirculation zone) and a downstream convecting (detached from the recirculation zone) flame piece. Within the range of operating conditions investigated, the conjugate heat exchange with the bluff-body had no impact on the flame blow-off.

  18. Isotope separation process

    International Nuclear Information System (INIS)

    Kaldor, A.; Rabinowitz, P.

    1979-01-01

    A method of separating the isotopes of an element is described, which comprises the steps of (i) subjecting molecules of a gaseous compound of the element simultaneously to two infrared radiations of different wavelengths, the first radiation having a wavelength which corresponds to an absorption band of the compound, which in turn corresponds to a mode of molecular motion in which there is participation by atoms of the element, and the second radiation having a power density greater than 10 6 watts per cm 2 , thereby exciting molecules of the compound in an isotopically selective manner, this step being conducted in such manner that the excited molecules either receive a level of energy sufficient to cause them to undergo conversion by unimolecular decomposition or receive a level of energy sufficient to cause them to undergo conversion by reaction with molecules of another gas present for that purpose; and (ii) separating and recovering converted molecules from unconverted molecules. (author)

  19. History of Suction-Type Laminar-Flow Control with Emphasis on Flight Resrearch: Monographs in Aerospace History Number 13

    Science.gov (United States)

    Braslow, A. L.

    1999-01-01

    The paper contains the following sections: Foreword; Preface; Laminar-Flow Control Concepts and Scope of Monograph; Early Research on Suction-Type Laminar-Flow Control (Research from the 1930s through the War Years; Research from after World War II to the Mid-1960s); Post X-21 Research on Suction-Type Laminar-Flow Control; Status of Laminar-Flow Control Technology in the Mid-1990s; Glossary; Document 1-Aeronautics Panel, AACB, R&D Review, Report of the Subpanel on Aeronautic Energy Conservation/Fuels; Document 2-Report of Review Group on X-21A Laminar Flow Control Program; Document 3-Langley Research Center Announcement, Establishment of Laminar Flow Control Working Group; Document 4-Intercenter Agreement for Laminar Flow Control Leading Edge Glove Flights, LaRC and DFRC; Document 5-Flight Report NLF-144, of AFTIF-111 Aircraft with the TACT Wing Modified by a Natural Laminar Flow Glove; Document 6-Flight Record, F-16XL Supersonic Laminar Flow Control Aircraft; Index; and About the Author.

  20. Effects of N2 gas on preheated laminar LPG jet diffusion flame

    International Nuclear Information System (INIS)

    Mishra, D.P.; Kumar, P.

    2010-01-01

    This paper presents an experimental investigation of the inert gas effect on flame length, NO x and soot free length fraction (SFLF) in a laminar LPG diffusion flame. Besides this, flame radiant fraction and temperature are also measured to explain observed NO x emission and SFLF. The inert is added to both air and fuel stream at each base line condition by maintaining a constant mass flow rate in each stream. Results indicate that inert addition leads to a significant enhancement in flame length for air-diluted stream than fuel-diluted stream. However, the flame length is observed to reduce with increasing reactant temperature. It is also observed that the SFLF increases with addition of N 2 for fuel-diluted stream. In contrast, SFLF remains almost constant when N 2 is added to air stream. The decrease in fuel concentration and gas temperature caused by inert addition leads to reduction in soot volume fraction and hence enhances SFLF. Interestingly, the SFLF reduces with increasing reactant temperature, due to reduction in induction period of soot formation caused by enhanced flame temperature. Besides this, the reduction in NO x emission level with inert addition is also observed. For all the three cases, the air dilution proved to be much efficient in reducing NO x emission level as compared to fuel dilution. This can be attributed to the differences in reduced gas temperature and residence time between air and fuel-diluted streams. On the contrary, NO x emission level enhances significantly with increasing reactant temperature as a result of increase in thermal NO x through Zeldovich mechanism.

  1. Effects of N{sub 2} gas on preheated laminar LPG jet diffusion flame

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, D.P.; Kumar, P. [Department of Aerospace Engineering, Indian Institute of Technology, Kanpur 208 016 (India)

    2010-11-15

    This paper presents an experimental investigation of the inert gas effect on flame length, NO{sub x} and soot free length fraction (SFLF) in a laminar LPG diffusion flame. Besides this, flame radiant fraction and temperature are also measured to explain observed NO{sub x} emission and SFLF. The inert is added to both air and fuel stream at each base line condition by maintaining a constant mass flow rate in each stream. Results indicate that inert addition leads to a significant enhancement in flame length for air-diluted stream than fuel-diluted stream. However, the flame length is observed to reduce with increasing reactant temperature. It is also observed that the SFLF increases with addition of N{sub 2} for fuel-diluted stream. In contrast, SFLF remains almost constant when N{sub 2} is added to air stream. The decrease in fuel concentration and gas temperature caused by inert addition leads to reduction in soot volume fraction and hence enhances SFLF. Interestingly, the SFLF reduces with increasing reactant temperature, due to reduction in induction period of soot formation caused by enhanced flame temperature. Besides this, the reduction in NO{sub x} emission level with inert addition is also observed. For all the three cases, the air dilution proved to be much efficient in reducing NO{sub x} emission level as compared to fuel dilution. This can be attributed to the differences in reduced gas temperature and residence time between air and fuel-diluted streams. On the contrary, NO{sub x} emission level enhances significantly with increasing reactant temperature as a result of increase in thermal NO{sub x} through Zeldovich mechanism. (author)

  2. Laminar Flame Velocity and Temperature Exponent of Diluted DME-Air Mixture

    Science.gov (United States)

    Naseer Mohammed, Abdul; Anwar, Muzammil; Juhany, Khalid A.; Mohammad, Akram

    2017-03-01

    In this paper, the laminar flame velocity and temperature exponent diluted dimethyl ether (DME) air mixtures are reported. Laminar premixed mixture of DME-air with volumetric dilutions of carbon dioxides (CO2) and nitrogen (N2) are considered. Experiments were conducted using a preheated mesoscale high aspect-ratio diverging channel with inlet dimensions of 25 mm × 2 mm. In this method, flame velocities are extracted from planar flames that were stabilized near adiabatic conditions inside the channel. The flame velocities are then plotted against the ratio of mixture temperature and the initial reference temperature. A non-linear power law regression is observed suitable. This regression analysis gives the laminar flame velocity at the initial reference temperature and temperature exponent. Decrease in the laminar flame velocity and increase in temperature exponent is observed for CO2 and N2 diluted mixtures. The addition of CO2 has profound influence when compared to N2 addition on both flame velocity and temperature exponent. Numerical prediction of the similar mixture using a detailed reaction mechanism is obtained. The computational mechanism predicts higher magnitudes for laminar flame velocity and smaller magnitudes of temperature exponent compared to experimental data.

  3. Study on laminar burning velocity of syngas-air premixed flames in various mixing conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kee Man; Jeong, Byeong Gyu [Sunchon National University, Suncheon (Korea, Republic of); Lee, Seung Ro [Chonbuk National University, Jeonju (Korea, Republic of)

    2015-07-15

    The laminar burning velocity of syngas-air premixed flames was measured with various equivalence ratios from 0.5 to 5.0 and a mole fraction of H{sub 2} from 0.05 to 0.75. The laminar burning velocity was experimentally determined using a Bunsen flame according to the cone angle and surface area methods. A premixed code with a USC-II detailed reaction mechanism was used for the numerical calculations to predict the laminar burning velocity and to examine the relationship between the burning velocity enhancement and the hydrogen-related reactions. The results indicate that an appropriate method for the measurement of laminar burning velocity is necessary in the H{sub 2}/CO/air syngas premixed flame. In addition, the burning velocity linearly increased with the increase of the H{sub 2} mole fraction in the syngas mixture, although the burning velocity of H{sub 2} was 10 times larger than that of CO. This result is attributed to the rapid production of H-radicals at the early stage of combustion. Furthermore, the predicted mole fractions of H and OH radicals increased with the increase of H{sub 2} mole fraction for a lean syngas mixture. However, the mole fraction of OH radicals, an indicator of heat release rate, decreased for rich syngas mixture, resulting in a reduction of the laminar burning velocity, even with an increase of the H{sub 2} mole fraction.

  4. Study on laminar burning velocity of syngas-air premixed flames in various mixing conditions

    International Nuclear Information System (INIS)

    Lee, Kee Man; Jeong, Byeong Gyu; Lee, Seung Ro

    2015-01-01

    The laminar burning velocity of syngas-air premixed flames was measured with various equivalence ratios from 0.5 to 5.0 and a mole fraction of H 2 from 0.05 to 0.75. The laminar burning velocity was experimentally determined using a Bunsen flame according to the cone angle and surface area methods. A premixed code with a USC-II detailed reaction mechanism was used for the numerical calculations to predict the laminar burning velocity and to examine the relationship between the burning velocity enhancement and the hydrogen-related reactions. The results indicate that an appropriate method for the measurement of laminar burning velocity is necessary in the H 2 /CO/air syngas premixed flame. In addition, the burning velocity linearly increased with the increase of the H 2 mole fraction in the syngas mixture, although the burning velocity of H 2 was 10 times larger than that of CO. This result is attributed to the rapid production of H-radicals at the early stage of combustion. Furthermore, the predicted mole fractions of H and OH radicals increased with the increase of H 2 mole fraction for a lean syngas mixture. However, the mole fraction of OH radicals, an indicator of heat release rate, decreased for rich syngas mixture, resulting in a reduction of the laminar burning velocity, even with an increase of the H 2 mole fraction.

  5. Parametric Study on the Characteristics of Multiphase Laminar Flow with Density Difference in Various Microchannels

    International Nuclear Information System (INIS)

    Paek, Seung Ho; Kim, Dong Sung; Choi, Young Ki

    2009-01-01

    In this paper, we have performed a parametric study on the characteristics of multiphase laminar flow with density difference in various microchannels. The interface between multiphase fluids is rotated by the gravitational forces induced by density difference. The numerical simulations were carried out via commercial CFD package to study the characteristics of multiphase laminar flow. The results of the numerical simulations in this study were verified by comparing with the previously reported experimental results in the literature. We have also proposed a new dimensionless relationship between dimensionless rotation angle of interface and dimensionless parameters are proposed for square microchannels with various aspect ratios. The dimensionless relationship could be widely applied to the reliable design of various microfluidic devices dealing with multiphase laminar flow

  6. The use of laminar tube flow in the study of hydrodynamic and chemical influences on polymer flocculation of Escherichia coli.

    Science.gov (United States)

    Whittington, P N; George, N

    1992-08-05

    The optimization of microbial flocculation for subsequent biomass separation must relate the floc properties to separation process criteria. The effects of flocculant type, dose, and hydrodynamic conditions on floc formation in laminar tube flow were determined for an Escherichia coli system. Combined with an on-line aggregation sensor, this technique allows the flocculation process to be rapidly optimized. This is important, because interbatch variation in fermentation broth has consequences for flocculation control and subsequent downstream processing. Changing tube diameter and length while maintaining a constant flow rate allowed independent study of the effects of shear and time on the flocculation rate and floc characteristics. Tube flow at higher shear rates increased the rate and completeness of flocculation, but reduced the maximum floc size attained. The mechanism for this size limitation does not appear to be fracture or erosion of existing flocs. Rearrangement of particles within the flocs appears to be most likely. The Camp number predicted the extent of flocculation obtained in terms of the reduction in primary particle number, but not in terms of floc size.

  7. Convective heat transfer from rough surfaces with two-dimensional ribs - transitional and laminar flow

    International Nuclear Information System (INIS)

    Dalle Donne, M.; Meyer, L.

    1978-01-01

    Measurements of friction factor and heat transfer coefficients for two rods of 18.9 mm 0.D. with two-dimensional roughness, each in two different outer smooth tubes have been performed in turbulent and laminar flow. The turbulent flow results indicate that the flow was not thermally fully established, the isothermal data however agree reasonably well with our previously obtained general correlation. Laminar flow results can be correlated best when the Reynolds and Greatz numbers are evaluated at the temperature average between the temperature of the inner rod surface and of the outer smooth surface of the annulus, the average being weighted over the two surfaces. (orig.) [de

  8. Ictiosis congénita tipo laminar, reporte de un caso.

    OpenAIRE

    Joaquín Saavedra D.; María José Sierralta S.; Cristian Saavedra D; Vanesa Rivera C; Francisco Cerda C.

    2014-01-01

    RESUMEN INTRODUCCIÓN: La ictiosis tipo laminar es una enfermedad dermatológica infrecuente perteneciente al grupo de las llamadas genodermatosis. Es una forma de ictiosis congénita que es evidente desde el nacimiento. PRESENTACIÓN DEL CASO: Recién nacido por cesárea, sexo masculino, de 36 semanas de gestación, adecuado para la edad gestacional y con APGAR 8. Antecedentes familiares: padres no consanguíneos y hermano con ictiosis tipo laminar. Luego de nacer es hospital...

  9. Fabrication of MgAl2O4 spinel/niobium laminar composites by plasma spraying

    International Nuclear Information System (INIS)

    Boncoeur, M.; Lochet, N.; Miomandre, F.; Schnedecker, G.

    1994-01-01

    The feasibility of plasma spray manufacturing of laminar ceramic matrix composites made of alternate thin layers of a ceramic oxide and a metal is demonstrated with a composite made of 7 layers, each 0.2 mm thick, of MgAl 2 O 4 spinel and niobium. Microstructure and mechanical characteristics have been studied with both as-sprayed and heat-treated under vacuum at 1400 C conditions. It is shown that the as-sprayed composite is brittle but becomes pseudo-plastic after heat treatment. These laminar composites are very attractive for the manufacturing of large surface, few millimeter thick components. (from authors). 4 figs., 4 refs

  10. Simulation of laminar and turbulent concentric pipe flows with the isogeometric variational multiscale method

    KAUST Repository

    Ghaffari Motlagh, Yousef; Ahn, Hyungtaek; Hughes, Thomas Jr R; Calo, Victor M.

    2013-01-01

    We present an application of the residual-based variational multiscale modeling methodology to the computation of laminar and turbulent concentric annular pipe flows. Isogeometric analysis is utilized for higher-order approximation of the solution using Non-Uniform Rational B-Splines (NURBS). The ability of NURBS to exactly represent curved geometries makes NURBS-based isogeometric analysis attractive for the application to the flow through annular channels. We demonstrate the applicability of the methodology to both laminar and turbulent flow regimes. © 2012 Elsevier Ltd.

  11. Numerical Heat Transfer Prediction for Laminar Flow in a Circular Pipe with a 90° Bend

    Science.gov (United States)

    Patro, Pandaba; Rout, Ani; Barik, Ashok

    2018-06-01

    Laminar air flow in a 90° bend has been studied numerically to investigate convective heat transfer, which is of practical relevance to electronic systems and refrigeration piping layout. CFD simulations are performed for Reynolds number in the range 200 to 1000 at different bend radius ratios (5, 10 and 20). The heat transfer characteristics are found to be enhanced in the curved pipe compared to a straight pipe, which are subjected to the same flow rate. The curvature and buoyancy effectively increase heat transfer in viscous laminar flows. The correlation between the flow structure and the heat transfer is found to be strong.

  12. Theoretical research on laminar friction resistance in tubes in rolling motion

    International Nuclear Information System (INIS)

    Yan Binghuo; Yu Lei; Yang Yanhua

    2010-01-01

    The model of laminar flow in tubes in rolling motion is established. The dimensionless correlation of velocity is derived, and the correlation of frictional resistance coefficient is also obtained. Of all the additional forces, only the tangential force effects on the flow. The effect of centrifugal and Coriolis forces on the flow is counteracted. The correlation of average frictional resistance coefficient is the same with that of no rolling motion. The effect of rolling motion on frictional resistance coefficient of laminar flow diminishes with the increase of Reynolds number. (authors)

  13. Laminar flow and convective transport processes scaling principles and asymptotic analysis

    CERN Document Server

    Brenner, Howard

    1992-01-01

    Laminar Flow and Convective Transport Processes: Scaling Principles and Asymptotic Analysis presents analytic methods for the solution of fluid mechanics and convective transport processes, all in the laminar flow regime. This book brings together the results of almost 30 years of research on the use of nondimensionalization, scaling principles, and asymptotic analysis into a comprehensive form suitable for presentation in a core graduate-level course on fluid mechanics and the convective transport of heat. A considerable amount of material on viscous-dominated flows is covered.A unique feat

  14. Centrifugal gas separator

    Energy Technology Data Exchange (ETDEWEB)

    Kanagawa, A; Fujii, O; Nakamoto, H

    1970-03-09

    Counter currents in the rotary drum of a centrifugal gas separator are produced by providing, at either end of the drum in the vicinity of the circumferential and central positions, respectively, outflow and inflow holes with a communicating passage external to the drum there between whereby gaseous counter currents are caused to flow within the drum and travel through the passage which is provided with gas flow adjustment means. Furthermore, the space defined by the stationary portion of the passage and the rotor drum is additionally provided with a screw pump or throttling device at either its stationary side or drum side or both in order to produce a radially directed gas flow therewithin. A gas mixture is axially admitted into the drum while centrifugal force and a cooling element provided therebelow cause an increase in gas pressure along and a gaseous flow toward the wall member, whereupon the comparatively high pressured circumferentially distributed gas is extracted from the outlet holes, flows through the external gas passage and back into the lower pressured drum core through the inlet holes, thus producing the desired counter currents. The gases thus separated are withdrawn along axially provided discharge pipes. Accordingly, this invention permits heating elements which were formerly used to produce thermal convection currents to be disposed of and allows the length of the rotor drum to be more efficiently utilized to enhance separation efficiency.

  15. Measurements of velocity-fields and temperature-fields in laminar and turbulent free convection boundary layers

    International Nuclear Information System (INIS)

    Fieg, G.

    1975-02-01

    This work deals with the hydrodynamics of laminar and turbulent free convection boundary layers on a vertical flat isothermal plate. Both for the laminar and turbulent region there is a good agreement with previous experimental and theoretical investigations. From these experiments one can draw important conclusions to the growth of instabilities in the transition region which lead to turbulence. (orig.) [de

  16. Reynolds number and geometry effects in laminar axisymmetric isothermal counterflows

    KAUST Repository

    Scribano, Gianfranco

    2016-12-29

    The counterflow configuration is a canonical stagnation flow, featuring two opposed impinging round jets and a mixing layer across the stagnation plane. Although counterflows are used extensively in the study of reactive mixtures and other applications where mixing of two streams is required, quantitative data on the scaling properties of the flow field are lacking. The aim of this work is to characterize the velocity and mixing fields in isothermal counterflows over a wide range of conditions. The study features both experimental data from particle image velocimetry and results from detailed axisymmetric simulations. The scaling laws for the nondimensional velocity and mixture fraction are obtained as a function of an appropriate Reynolds number and the ratio of the separation distance of the nozzles to their diameter. In the range of flow configurations investigated, the nondimensional fields are found to depend primarily on the separation ratio and, to a lesser extent, the Reynolds number. The marked dependence of the velocity field with respect to the separation ratio is linked to a high pressure region at the stagnation point. On the other hand, Reynolds number effects highlight the role played by the wall boundary layer on the interior of the nozzles, which becomes less important as the separation ratio decreases. The normalized strain rate and scalar dissipation rate at the stagnation plane are found to attain limiting values only for high values of the Reynolds number. These asymptotic values depend markedly on the separation ratio and differ significantly from the values produced by analytical models. The scaling of the mixing field does not show a limiting behavior as the separation ratio decreases to the smallest practical value considered.

  17. Reynolds number and geometry effects in laminar axisymmetric isothermal counterflows

    KAUST Repository

    Scribano, Gianfranco; Bisetti, Fabrizio

    2016-01-01

    dependence of the velocity field with respect to the separation ratio is linked to a high pressure region at the stagnation point. On the other hand, Reynolds number effects highlight the role played by the wall boundary layer on the interior of the nozzles

  18. Characteristics of autoignited laminar lifted flames in heated coflow jets of carbon monoxide/hydrogen mixtures

    KAUST Repository

    Choi, Byungchul; Chung, Suk-Ho

    2012-01-01

    and then increased as the jet velocity increased. Based on the mechanism in which the autoignited laminar lifted flame is stabilized by ignition delay time, the liftoff height can be influenced not only by the heat loss, but also by the preferential diffusion between

  19. Posterior cervical spine arthrodesis with laminar screws. A report of two cases

    International Nuclear Information System (INIS)

    Nakanishi, Kazuo; Tanaka, Masato; Sugimoto, Yoshihisa; Ozaki, Toshifumi

    2007-01-01

    We performed fixation using laminar screws in 2 patients in whom lateral mass screws, pedicle screws or transarticular screws could not be inserted. One was a 56-year-old woman who had anterior atlantoaxial subluxation (AAS). When a guide wire was inserted using an imaging guide, the hole bled massively. We thought the re-insertion of a guide wire or screw would thus increase the risk of vascular injury, so we used laminar screws. The other case was an 18-year-old man who had a hangman fracture. Preoperative magnetic resonance angiography showed occlusion of the left vertebral artery. A laminar screw was inserted into the patent side (i.e., the right side of C2). Cervical pedicle screws are the most biomechanically stable screws. However, their use carries a high risk of neurovascular complications during screw insertion, because the cervical pedicle is small and is adjacent laterally to the vertebral artery, medially to the spinal cord, and vertically to the nerve roots. Lateral mass screws are also reported to involve a risk of neurovascular injuries. The laminar screw method was thus thought to be useful, since arterial injuries could thus be avoided and it could also be used as a salvage modality for the previous misinsertion. (author)

  20. Optimization of the THz radiation from superconductor at non-laminar regime

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Mehdi, E-mail: hosseini@sutech.ac.ir

    2016-10-15

    Highlights: • The terahertz radiation of a mesa structure at non laminar regime is considered here. • The non-laminarity of this media is modeled. • The equation of vortex motion and electromagnetic field is solved. • The radiated power is obtained and the parameter optimization for maximize the radiated power is done. - Abstract: The THz radiation due to the flux flow in a superconductor slab at non-laminar regime has been investigated and the radiated power spectrum has been calculated. The parameter (τ) is defined to show amount of non-laminarity. The results reveal that for small values of τ, the system radiated at the harmonics of famous washboard frequency. However, for large values of τ, the radiation spectrum will be changed and for extreme values of τ, the peaks will be flat. Therefore the washboard picture is not valid anymore. The results show that the radiation power is optimum for the special value of τ. Also, the results compared with other theoretical and experimental data.

  1. LAMINAR FLOW THROUGH A TUBE WITH AN EASILY PENETRABLE ROUGHNESS NEAR AXIS

    Directory of Open Access Journals (Sweden)

    Є.О. Гаєв

    2012-12-01

    Full Text Available  Mathematical model has been suggested and investigation carried out of laminar flow through a round tube with a porous insertion (easily penetrable roughness, EPR in its middle along the axis. Velocity and shear fields have been found analytically for stable flow region, as well as hydraulic resistance as functions of EPR density and its height.

  2. Modeling of confined and unconfined laminar premixed flames on slit and tube burners

    NARCIS (Netherlands)

    Mallens, R.M.M.; Lange, de H.C.; Ven, van de C.J.H.; Goey, de L.P.H.

    1995-01-01

    A model is presented for laminar premixed Bunsen flames on slit and cylindrical burners burning in a surrounding atmosphere. A comparison between modeling and experimental results shows that the model can reproduce the experimental results within 10% accuracy. The influence of a surrounding

  3. Laminar dispersion in parallel plate sections of flowing systems used in analytical chemistry and chemical engineering

    NARCIS (Netherlands)

    Kolev, S.D.; Kolev, Spas D.; van der Linden, W.E.

    1991-01-01

    An exact solution of the convective-diffusion equation for fully developed parallel plate laminar flow was obtained. It allows the derivation of theoretical relationships for calculating the Peclet number in the axially dispersed plug flow model and the concentration distribution perpendicular to

  4. Experimental study of laminar mixed convection in a rod bundle with mixing vane spacer grids

    Energy Technology Data Exchange (ETDEWEB)

    Mohanta, Lokanath, E-mail: lxm971@psu.edu [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Cheung, Fan-Bill [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Bajorek, Stephen M.; Tien, Kirk; Hoxie, Chris L. [Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001 (United States)

    2017-02-15

    Highlights: • Investigated the heat transfer during mixed laminar convection in a rod bundle with linearly varying heat flux. • The Nusselt number increases downstream of the inlet with increasing Richardson number. • Developed an enhancement factor to account for the effects of mixed convection over the forced laminar heat transfer. - Abstract: Heat transfer by mixed convection in a rod bundle occurs when convection is affected by both the buoyancy and inertial forces. Mixed convection can be assumed when the Richardson number (Ri = Gr/Re{sup 2}) is on the order of unity, indicating that both forced and natural convection are important contributors to heat transfer. In the present study, data obtained from the Rod Bundle Heat Transfer (RBHT) facility was used to determine the heat transfer coefficient in the mixed convection regime, which was found to be significantly larger than those expected assuming purely forced convection based on the inlet flow rate. The inlet Reynolds (Re) number for the tests ranged from 500 to 1300, while the Grashof (Gr) number varied from 1.5 × 10{sup 5} to 3.8 × 10{sup 6} yielding 0.25 < Ri < 4.3. Using results from RBHT test along with the correlation from the FLECHT-SEASET test program for laminar forced convection, a new correlation ​is proposed for mixed convection in a rod bundle. The new correlation accounts for the enhancement of heat transfer relative to laminar forced convection.

  5. Development of advanced stability theory suction prediction techniques for laminar flow control. [on swept wings

    Science.gov (United States)

    Srokowski, A. J.

    1978-01-01

    The problem of obtaining accurate estimates of suction requirements on swept laminar flow control wings was discussed. A fast accurate computer code developed to predict suction requirements by integrating disturbance amplification rates was described. Assumptions and approximations used in the present computer code are examined in light of flow conditions on the swept wing which may limit their validity.

  6. Mathematical modeling for laminar flow of power law fluid in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Renato A.; Mesquita, Maximilian S. [Universidade Federal do Espirito Santo (UFES), Sao Mateus, ES (Brazil). Centro Universitario Norte do Espirito Santo. Dept. de Engenharias e Computacao

    2010-07-01

    In this paper, the macroscopic equations for laminar power-law fluid flow is obtained for a porous medium starting from traditional equations (Navier-Stokes). Then, the volume averaging is applied in traditional transport equations with the power-law fluid model. This procedure leads to macroscopic transport equations set for non-Newtonian fluid. (author)

  7. Prevention of airborne contamination and cross-contamination in germ-free mice by laminar flow

    NARCIS (Netherlands)

    Waaij, D. van der; Andres, A.H.

    1971-01-01

    The efficacy of horizontal and vertical laminar flow units (equipped with high-efficiency air filters) in the prevention of cross-contamination between cages and of contamination from outside has been demonstrated. With germ-free mice and using germ-free standard techniques for sterilization and for

  8. Experimental test on aluminium rod submitted to a laminar water flow

    International Nuclear Information System (INIS)

    Britto Aghina, L.O. de; Cruz, J.R.B.

    1986-06-01

    The result obtained from a experiment with an aluminium rod submitted to a laminar water flow is compared to the result predicted by empirical correlations used in the vibration analysis of the RPR reactor fuel rods. (L.C.J.A.)

  9. Measurements of the laminar burning velocity of hydrogen-air premixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Pareja, Jhon; Burbano, Hugo J. [Science and Technology of Gases and Rational Use of Energy Group, Faculty of Engineering, University of Antioquia, Calle 67 N 53, 108 Bloque 20, 447 Medellin (Colombia); Ogami, Yasuhiro [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan)

    2010-02-15

    Experimental and numerical studies on laminar burning velocities of hydrogen-air mixtures were performed at standard pressure and room temperature varying the equivalence ratio from 0.8 to 3.0. The flames were generated using a contoured slot-type nozzle burner (4 mm x 10 mm). Measurements of laminar burning velocity were conducted using particle tracking velocimetry (PTV) combined with Schlieren photography. This technique provides the information of instantaneous local burning velocities in the whole region of the flame front, and laminar burning velocities were determined using the mean value of local burning velocities in the region of non-stretch. Additionally, average laminar burning velocities were determined using the angle method and compared with the data obtained with the PTV method. Numerical calculations were also conducted using detailed reaction mechanisms and transport properties. The experimental results from the PTV method are in good agreement with the numerical results at every equivalence ratio of the range of study. Differences between the results obtained with the angle method and those with the PTV method are reasonably small when the effects of flame stretch and curvature are reduced by using a contoured slot-type nozzle. (author)

  10. New method for the determination of precipitation kinetics using a laminar jet reactor

    NARCIS (Netherlands)

    Al Tarazi, M.Y.M.; Heesink, Albertus B.M.; Versteeg, Geert

    2005-01-01

    In this paper a new experimental method for determining the kinetics of fast precipitation reactions is introduced. Use is made of a laminar jet reactor, which is also frequently applied to determine the kinetics of homogeneous gas–liquid reactions. The liquid containing one or more of the

  11. New method for the determination of precipitation kinetics using a laminar jet reactor

    NARCIS (Netherlands)

    Al-Tarazi, Mousa; Heesink, A. Bert M.; Versteeg, Geert F.

    2005-01-01

    In this paper a new experimental method for determining the kinetics of fast precipitation reactions is introduced. Use is made of a laminar jet reactor, which is also frequently applied to determine the kinetics of homogeneous gas-liquid reactions. The liquid containing one or more of the

  12. Fabrication of free-standing replicas of fragile, laminar, chitinous biotemplates

    International Nuclear Information System (INIS)

    Lakhtakia, Akhlesh; Motyka, Michael A; MartIn-Palma, Raul J; Pantano, Carlo G

    2009-01-01

    The conformal-evaporated-film-by-rotation technique, followed by the dissolution of chitin in an aqueous solution of orthophosphoric acid, can be used to fabricate free-standing replicas of fragile, laminar, chitinous biotemplates. This novel approach was demonstrated using butterfly wings as biotemplates and GeSeSb chalcogenide glass for replicas. (communication)

  13. Experimental and computational study of scalar modes in a periodic laminar flow

    NARCIS (Netherlands)

    Baskan, O.; Speetjens, M.F.M.; Metcalfe, G.; Clercx, H.J.H.

    2015-01-01

    Scalar fields can evolve complex coherent structures under the action of periodic laminar flows. This comes about from the competition between chaotic advection working to create structure at ever finer length scales and diffusion working to eliminate fine-scale structure. Recently analysis of this

  14. Subcortical laminar heterotopia in two sisters and their mother : MRI, clinical findings and pathogenesis

    NARCIS (Netherlands)

    van der Valk, PHM; Snoeck, [No Value; Meiners, LC; des Portes, [No Value; Chelly, J; Pinard, JM; Ippel, PF; van Nieuwenhuizen, O

    MR imaging, clinical data and underlying pathogenesis of subcortical laminar heterotopia (SCLH), also known as band heterotopia, in two sisters and their mother are presented. On MR imaging a different degree of SCLH was found in all three affected family-members. The inversion recovery sequence was

  15. Fabrication of free-standing replicas of fragile, laminar, chitinous biotemplates

    Energy Technology Data Exchange (ETDEWEB)

    Lakhtakia, Akhlesh; Motyka, Michael A [Materials Research Institute and Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802 (United States); MartIn-Palma, Raul J; Pantano, Carlo G [Materials Research Institute and Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)], E-mail: akhlesh@psu.edu

    2009-09-01

    The conformal-evaporated-film-by-rotation technique, followed by the dissolution of chitin in an aqueous solution of orthophosphoric acid, can be used to fabricate free-standing replicas of fragile, laminar, chitinous biotemplates. This novel approach was demonstrated using butterfly wings as biotemplates and GeSeSb chalcogenide glass for replicas. (communication)

  16. Laminar Flame Speeds of Gasoline Surrogates Measured with the Flat Flame Method

    KAUST Repository

    Liao, Y.-H.; Roberts, William L.

    2016-01-01

    © 2016 American Chemical Society. The adiabatic, laminar flame speeds of gasoline surrogates at atmospheric pressure over a range of equivalence ratios of = 0.8-1.3 and unburned gas temperatures of 298-400 K are measured with the flat flame method

  17. Mapping Cortical Laminar Structure in the 3D BigBrain.

    Science.gov (United States)

    Wagstyl, Konrad; Lepage, Claude; Bludau, Sebastian; Zilles, Karl; Fletcher, Paul C; Amunts, Katrin; Evans, Alan C

    2018-07-01

    Histological sections offer high spatial resolution to examine laminar architecture of the human cerebral cortex; however, they are restricted by being 2D, hence only regions with sufficiently optimal cutting planes can be analyzed. Conversely, noninvasive neuroimaging approaches are whole brain but have relatively low resolution. Consequently, correct 3D cross-cortical patterns of laminar architecture have never been mapped in histological sections. We developed an automated technique to identify and analyze laminar structure within the high-resolution 3D histological BigBrain. We extracted white matter and pial surfaces, from which we derived histologically verified surfaces at the layer I/II boundary and within layer IV. Layer IV depth was strongly predicted by cortical curvature but varied between areas. This fully automated 3D laminar analysis is an important requirement for bridging high-resolution 2D cytoarchitecture and in vivo 3D neuroimaging. It lays the foundation for in-depth, whole-brain analyses of cortical layering.

  18. On the optimal choice of the laminar medium substance for ultrarelativistic particle transition radiation detectors

    International Nuclear Information System (INIS)

    Avakian, A.L.; Garibian, G.M.; Yang, C.

    1975-01-01

    The dependence of the X-ray transition yield in the energy region 10-20keV produced by an ultrarelativistic charged particle in various laminar media on the substance of the plates is investigated in detail. It is shown that in this case beryllium is the most optimal substance. Other energy regions of transition radiation quanta are also considered. (Auth.)

  19. Flow instability in laminar jet flames driven by alternating current electric fields

    KAUST Repository

    Kim, Gyeong Taek; Park, Daegeun; Cha, Min; Park, Jeong; Chung, Suk-Ho

    2016-01-01

    The effect of electric fields on the instability of laminar nonpremixed jet flames was investigated experimentally by applying the alternating current (AC) to a jet nozzle. We aimed to elucidate the origin of the occurrence of twin-lifted jet flames

  20. Segmental and laminar organization of the spinothalamic neurons in cat : Evidence for at least five separate clusters

    NARCIS (Netherlands)

    Klop, Esther Marije; Mouton, Leonora J.; Holstege, Gert

    2005-01-01

    The spinothalamic tract (STT), well known for its role in the relay of information about noxe, temperature, and crude touch, is usually associated with projections from lamina 1, but spinothalamic neurons in other laminae have also been reported. In cat, no complete overview exists of the precise

  1. How the venetian blind percept emerges from the laminar cortical dynamics of 3D vision.

    Science.gov (United States)

    Cao, Yongqiang; Grossberg, Stephen

    2014-01-01

    The 3D LAMINART model of 3D vision and figure-ground perception is used to explain and simulate a key example of the Venetian blind effect and to show how it is related to other well-known perceptual phenomena such as Panum's limiting case. The model proposes how lateral geniculate nucleus (LGN) and hierarchically organized laminar circuits in cortical areas V1, V2, and V4 interact to control processes of 3D boundary formation and surface filling-in that simulate many properties of 3D vision percepts, notably consciously seen surface percepts, which are predicted to arise when filled-in surface representations are integrated into surface-shroud resonances between visual and parietal cortex. Interactions between layers 4, 3B, and 2/3 in V1 and V2 carry out stereopsis and 3D boundary formation. Both binocular and monocular information combine to form 3D boundary and surface representations. Surface contour surface-to-boundary feedback from V2 thin stripes to V2 pale stripes combines computationally complementary boundary and surface formation properties, leading to a single consistent percept, while also eliminating redundant 3D boundaries, and triggering figure-ground perception. False binocular boundary matches are eliminated by Gestalt grouping properties during boundary formation. In particular, a disparity filter, which helps to solve the Correspondence Problem by eliminating false matches, is predicted to be realized as part of the boundary grouping process in layer 2/3 of cortical area V2. The model has been used to simulate the consciously seen 3D surface percepts in 18 psychophysical experiments. These percepts include the Venetian blind effect, Panum's limiting case, contrast variations of dichoptic masking and the correspondence problem, the effect of interocular contrast differences on stereoacuity, stereopsis with polarity-reversed stereograms, da Vinci stereopsis, and perceptual closure. These model mechanisms have also simulated properties of 3D neon

  2. Towards a unified theory of neocortex: laminar cortical circuits for vision and cognition.

    Science.gov (United States)

    Grossberg, Stephen

    2007-01-01

    A key goal of computational neuroscience is to link brain mechanisms to behavioral functions. The present article describes recent progress towards explaining how laminar neocortical circuits give rise to biological intelligence. These circuits embody two new and revolutionary computational paradigms: Complementary Computing and Laminar Computing. Circuit properties include a novel synthesis of feedforward and feedback processing, of digital and analog processing, and of preattentive and attentive processing. This synthesis clarifies the appeal of Bayesian approaches but has a far greater predictive range that naturally extends to self-organizing processes. Examples from vision and cognition are summarized. A LAMINART architecture unifies properties of visual development, learning, perceptual grouping, attention, and 3D vision. A key modeling theme is that the mechanisms which enable development and learning to occur in a stable way imply properties of adult behavior. It is noted how higher-order attentional constraints can influence multiple cortical regions, and how spatial and object attention work together to learn view-invariant object categories. In particular, a form-fitting spatial attentional shroud can allow an emerging view-invariant object category to remain active while multiple view categories are associated with it during sequences of saccadic eye movements. Finally, the chapter summarizes recent work on the LIST PARSE model of cognitive information processing by the laminar circuits of prefrontal cortex. LIST PARSE models the short-term storage of event sequences in working memory, their unitization through learning into sequence, or list, chunks, and their read-out in planned sequential performance that is under volitional control. LIST PARSE provides a laminar embodiment of Item and Order working memories, also called Competitive Queuing models, that have been supported by both psychophysical and neurobiological data. These examples show how

  3. Laminar burning velocities at elevated pressures for gasoline and gasoline surrogates associated with RON

    KAUST Repository

    Mannaa, Ossama

    2015-06-01

    The development and validation of a new gasoline surrogate using laminar flame speed as a target parameter is presented. Laminar burning velocities were measured using a constant-volume spherical vessel with ignition at the center of the vessel. Tested fuels included iso-octane, n-heptane, toluene, various mixtures of primary reference fuels (PRFs) and toluene reference fuels (TRFs) and three gasoline fuels of 70, 85 and 95 RON (FACE J, C and F) at the initial temperature of 358K and pressures up to 0.6MPa in the equivalence ratio ranging from 0.8 to 1.6. Normalized laminar burning velocity data were mapped into a tri-component mixture space at different experimental conditions to allocate different gasoline surrogates for different gasoline fuels, having RON of 70, 85 and 95. The surrogates of TRF-70-4 (17.94% iso-C8H18 +42.06% n-C7H16 +40% C7H8), TRF-85-1 (77.4% iso-C8H18 +17.6% n-C7H16 +5% C7H8), and TRF-95-1 (88.47% iso-C8H18 +6.53% n-C7H16 +5% C7H8) of RON 70, 85 and 95, respectively, are shown to successfully emulate the burning rate characteristics of the gasoline fuels associated with these RONs under the various experimental conditions investigated. An empirical correlation was derived to obtain laminar burning velocities at pressures that are experimentally unattainable as high as 3.0MPa. Laminar burning velocities were comparable to the simulated values for lean and stoichiometric flames but they were relatively higher than the simulated values for rich flames. A flame instability assessment was conducted by determining Markstein length, critical Pecklet number, and critical Karlovitz number at the onset of flame instability.

  4. Impact of laminar flow velocity of different acids on enamel calcium loss.

    Science.gov (United States)

    Attin, T; Becker, K; Wiegand, A; Tauböck, T T; Wegehaupt, F J

    2013-03-01

    The aim of the study was to evaluate the impact of flow velocity under laminar flow conditions of different acidic solutions on enamel erosion. A total of 240 bovine enamel specimens were prepared and allocated to 30 groups (n = 8 each). Samples of 18 groups were superfused in a flow chamber system with laminar flow behavior using 1 ml of citric acid or hydrochloric acid (HCl) of pH 2.0, 2.6 or 3.0. Flow rates in the sample chamber were adjusted to 10, 60 or 100 μl/min. To simulate turbulent flow behavior, samples of six groups were immersed in 1 ml of the respective solution, which was vortexed (15 min, 600 rpm). For simulating non-agitated conditions, specimens of the remaining six groups were immersed in 1 ml of the respective solution without stirring. Calcium in the solutions, released from the enamel samples, was determined using Arsenazo III method. For acidic solutions of pH 2.6 and 3.0, erosive potential of citric acid was equivalent to that of HCl at a flow of 100 μl/min. The same observation was made for the samples subjected to turbulent conditions at pH 3. At all other conditions, citric acid induced a significantly higher calcium loss than HCl. It is concluded that under slow laminar flow conditions, flow rate variations lead to higher erosive impact of citric acid compared to hydrochloric acid at pH 2.0, but not at pH ≥ 2.6 and increasing laminar flow or turbulent conditions. Erosive enamel dissolution under laminar flow conditions is a complex issue influenced by flow rate and acidic substrate.

  5. Operating Room Environment Control. Part A: a Valve Cannister System for Anesthetic Gas Adsorption. Part B: a State-of-the-art Survey of Laminar Flow Operating Rooms. Part C: Three Laminar Flow Experiments

    Science.gov (United States)

    Meyer, J. S.; Kosovich, J.

    1973-01-01

    An anesthetic gas flow pop-off valve canister is described that is airtight and permits the patient to breath freely. Once its release mechanism is activated, the exhaust gases are collected at a hose adapter and passed through activated coal for adsorption. A survey of laminar air flow clean rooms is presented and the installation of laminar cross flow air systems in operating rooms is recommended. Laminar flow ventilation experiments determine drying period evaporation rates for chicken intestines, sponges, and sections of pig stomach.

  6. Computational study of heat transfer from the inner surface of a circular tube to force high temperature liquid metal flow in laminar and transition regions

    Science.gov (United States)

    Hata, K.; Fukuda, K.; Masuzaki, S.

    2018-03-01

    Heat transfer through forced convection from the inner surface of a circular tube to force the flow of liquid sodium in the laminar and transition regions were numerically analysed for two types of tube geometries (concentric annular and circular tubes) and two types of equivalent diameters (hydraulic and thermal equivalent diameters). The unsteady laminar three-dimensional basic equations for forced convection heat transfer caused by a step heat flux were numerically solved until a steady state is attained. The code of the parabolic hyperbolic or elliptic numerical integration code series (PHOENICS) was used for calculations by considering relevant temperature dependent thermo-physical properties. The concentric annular tube has a test tube with inner and outer diameters of 7.6 and 14.3 mm, respectively, has a heated length of 52 mm, and an L/d of 6.84. The two circular tubes have inner diameters of 6.7 and 19.3 mm with L/d of 7.76 and 2.69, respectively, and a heated length of 52 mm. The inlet liquid temperature, inlet liquid velocity, and surface heat flux were equally set for each test tube as T in ≅573 to 585 K, u in = 0.0852 to 1 m/s, and q = 2×105 to 2.5×106 W/m2, respectively. The increase in temperature from the leading edge of the heated section to the outlet of the circular tubes (with a hydraulic diameter of d H = 6.7 mm and a thermal equivalent diameter d te = 19.3 mm) was approximately 2.70 and 1.21 times as large as the corresponding values of the concentric annular tube with an inner diameter of 7.6 mm and an outer diameter of 14.3 mm, respectively. A quantity in the laminar and transition regions was suggested as the dominant variable involved in the forced convection heat transfer in the circular tube. The values of the local and average Nusselt numbers, Nu z and Nu av , respectively, for a concentric annular tube with d H = 6.7 mm and for a circular tube with d H = 6.7 mm were calculated to examine the effects of q, T in , and Pe on heat

  7. Steam-water separator

    International Nuclear Information System (INIS)

    Modrak, T.M.; Curtis, R.W.

    1978-01-01

    The steam-water separator connected downstream of a steam generator consists of a vertical centrifugal separator with swirl blades between two concentric pipes and a cyclone separator located above. The water separated in the cyclone separator is collected in the inner tube of the centrifugal separator which is closed at the bottom. This design allows the overall height of the separator to be reduced. (DG) [de

  8. Unit Reynolds number, Mach number and pressure gradient effects on laminar-turbulent transition in two-dimensional boundary layers

    Science.gov (United States)

    Risius, Steffen; Costantini, Marco; Koch, Stefan; Hein, Stefan; Klein, Christian

    2018-05-01

    The influence of unit Reynolds number (Re_1=17.5× 106-80× 106 {m}^{-1}), Mach number (M= 0.35-0.77) and incompressible shape factor (H_{12} = 2.50-2.66) on laminar-turbulent boundary layer transition was systematically investigated in the Cryogenic Ludwieg-Tube Göttingen (DNW-KRG). For this investigation the existing two-dimensional wind tunnel model, PaLASTra, which offers a quasi-uniform streamwise pressure gradient, was modified to reduce the size of the flow separation region at its trailing edge. The streamwise temperature distribution and the location of laminar-turbulent transition were measured by means of temperature-sensitive paint (TSP) with a higher accuracy than attained in earlier measurements. It was found that for the modified PaLASTra model the transition Reynolds number (Re_{ {tr}}) exhibits a linear dependence on the pressure gradient, characterized by H_{12}. Due to this linear relation it was possible to quantify the so-called `unit Reynolds number effect', which is an increase of Re_{ {tr}} with Re_1. By a systematic variation of M, Re_1 and H_{12} in combination with a spectral analysis of freestream disturbances, a stabilizing effect of compressibility on boundary layer transition, as predicted by linear stability theory, was detected (`Mach number effect'). Furthermore, two expressions were derived which can be used to calculate the transition Reynolds number as a function of the amplitude of total pressure fluctuations, Re_1 and H_{12}. To determine critical N-factors, the measured transition locations were correlated with amplification rates, calculated by incompressible and compressible linear stability theory. By taking into account the spectral level of total pressure fluctuations at the frequency of the most amplified Tollmien-Schlichting wave at transition location, the scatter in the determined critical N-factors was reduced. Furthermore, the receptivity coefficients dependence on incidence angle of acoustic waves was used to

  9. Energy of ground state of laminar electron-hole liquid

    International Nuclear Information System (INIS)

    Andryushin, E.A.

    1976-01-01

    The problem of a possible existence of metal electron-hole liquid in semiconductors is considered. The calculation has been carried out for the following model: two parallel planes are separated with the distance on one of the planes electrons moving, on the other holes doing. Transitions between the planes are forbidden. The density of particles for both planes is the same. The energy of the ground state and correlation functions for such electron-and hole system are calculated. It is shown that the state of a metal liquid is more advantageous against the exciton gas. For the mass ratio of electrons and holes, msub(e)/msub(h) → 0 a smooth rearrangement of the system into a state with ordered heavy particles is observed

  10. Fictional Separation Logic

    DEFF Research Database (Denmark)

    Jensen, Jonas Buhrkal; Birkedal, Lars

    2012-01-01

    , separation means physical separation. In this paper, we introduce \\emph{fictional separation logic}, which includes more general forms of fictional separating conjunctions P * Q, where "*" does not require physical separation, but may also be used in situations where the memory resources described by P and Q...

  11. Experimental Investigation of Separated and Transitional Boundary Layers Under Low-Pressure Turbine Airfoil Conditions

    Science.gov (United States)

    Hultgren, Lennart S.; Volino, Ralph J.

    2002-01-01

    -stream turbulence level do not have a significant effect on the location of boundary-layer separation unless they are high enough to induce transition upstream of separation. The location and extent of the transition zone, in contrast, depend strongly on Re and TI. The beginning of reattachment closely follows the onset of transition. Under low free-stream turbulence conditions the boundary layer is laminar at separation and then begins to exhibit fluctuations in a finite frequency band in the shear layer over the separation bubble. These fluctuations are due to instability waves. The fluctuations grow in magnitude, higher harmonics are generated, and finally lead to a breakdown to turbulence. Transition begins in the shear layer, but quickly spreads to the near wall region and causes the boundary layer to reattach. The transition is rapid and the resulting turbulence contains a full range of high and low frequencies. Under high free-stream turbulence conditions, slowly growing low-frequency fluctuations are induced in the pretransitional boundary layer by the free-stream. The separation bubbles are considerably thinner than in the low TI cases, resulting in thinner boundary layers at the end of the test wall. At Re=50,000 and 100,000, the pre-transitional boundary layer separates at about the same location as in the low TI cases. Transition occurs through a bypass mode, begins upstream of the corresponding low-TI location, and proceeds in a manner similar to that of an attached boundary layer. Under high TI at Re=200,000 and 300,000, transition begins before separation. The boundary layer may separate, but if it does the separation bubble is very short and does not significantly affect the downstream development of the boundary layer. A comparison is made to previous work in a simulated cascade.

  12. Autoignition characteristics of laminar lifted jet flames of pre-vaporized iso-octane in heated coflow air

    KAUST Repository

    Al-Noman, Saeed M.; Choi, Sang Kyu; Chung, Suk-Ho

    2015-01-01

    The stabilization characteristics of laminar non-premixed jet flames of pre-vaporized iso-octane, one of the primary reference fuels for octane rating, have been studied experimentally in heated coflow air. Non-autoignited and autoignited lifted

  13. Separation Anxiety (For Parents)

    Science.gov (United States)

    ... Safe Videos for Educators Search English Español Separation Anxiety KidsHealth / For Parents / Separation Anxiety What's in this ... both of you get through it. About Separation Anxiety Babies adapt pretty well to other caregivers. Parents ...

  14. Tensile behavior of unnotched and notched tungsten--copper laminar composites

    International Nuclear Information System (INIS)

    Hoffman, C.A.

    1976-06-01

    Relations were studied between the tensile strengths of unnotched and of notched, and elastic moduli of unnotched laminar sheet or foil composites and the amounts of reinforcement. Tungsten was used as the reinforcement and copper as the matrix, and the tests were run at room temperature. Three thicknesses of tungsten (i.e., 0.00254, 0.0127, and 0.0254 cm (0.001, 0.005, and 0.010 in) were used, and the nominal volume fraction of tungsten was varied from about 0.05 to 0.95. It was found that the tensile strength of the unnotched specimens could be related to the amount of reinforcement, as could the elastic moduli, and that these values could be predicted by use of the rule of mixtures. The tensile strengths of the notched laminar composites could be predicted by use of the rule of mixtures using strengths for notched constituents, provided notch effects did not predominate. (Author)

  15. Experimental-theoretical analysis of laminar internal forced convection with nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Cerqueira, Ivana G.; Cotta, Renato M. [Lab. of Transmission and Technology of Heat-LTTC. Mechanical Eng. Dept. - POLI and COPPE/UFRJ, Rio de Janeiro, RJ (Brazil)], E-mail: cotta@mecanica.coppe.ufrj.br; Mota, Carlos Alberto A. [Conselho Nacional de Pesquisas - CNPq, Brasilia, DF (Brazil)], e-mail: carlosal@cnpq.br; Nunes, Jeziel S. [INPI, Rio de Janeiro, RJ (Brazil)], e-mail: jeziel@inpi.gov.br

    2010-07-01

    This work reports fundamental experimental-theoretical research related to heat transfer enhancement in laminar channel flow with nanofluids, which are essentially modifications of the base fluid with the dispersion of metal oxide nanoparticles. The theoretical work was performed by making use of mixed symbolic-numerical computation (Mathematica 7.0 platform) and a hybrid numerical-analytical methodology (Generalized Integral Transform Technique - GITT) in accurately handling the governing partial differential equations for the heat and fluid flow problem formulation with temperature dependency in all the thermophysical properties. Experimental work was also undertaken based on a thermohydraulic circuit built for this purpose, and sample results are presented to verify the proposed model. The aim is to illustrate detailed modeling and robust simulation attempting to reach an explanation of the controversial heat transfer enhancement observed in laminar forced convection with nanofluids. (author)

  16. A numerical investigation of laminar forced convection in a solar collector with non-circular duct

    Directory of Open Access Journals (Sweden)

    Teleszewski Tomasz Janusz

    2017-01-01

    Full Text Available This paper presents a two-dimensional numerical study to investigate laminar flow in a flat plate solar collector with non-circular duct (regular polygonal, elliptical, and Cassini oval shape featuring forced convection with constant axial wall heat flux and constant peripheral wall temperature (H1 condition. Applying the velocity profile obtained for the duct laminar flow, the energy equation was solved exactly for the constant wall heat flux using the Boundary Element Method (BEM. Poiseuille and Nusselt numbers were obtained for flows having a different number of geometrical factors. The results are presented and discussed in the form of tables and graphs. The area goodness factor and volume goodness factor are calculated. The predicted correlations for Poiseuille and Nusselt numbers may be a very useful resource for the design and optimization of solar collectors with non-circular ducts.

  17. Direct numerical simulation of laminar-turbulent flow over a flat plate at hypersonic flow speeds

    Science.gov (United States)

    Egorov, I. V.; Novikov, A. V.

    2016-06-01

    A method for direct numerical simulation of a laminar-turbulent flow around bodies at hypersonic flow speeds is proposed. The simulation is performed by solving the full three-dimensional unsteady Navier-Stokes equations. The method of calculation is oriented to application of supercomputers and is based on implicit monotonic approximation schemes and a modified Newton-Raphson method for solving nonlinear difference equations. By this method, the development of three-dimensional perturbations in the boundary layer over a flat plate and in a near-wall flow in a compression corner is studied at the Mach numbers of the free-stream of M = 5.37. In addition to pulsation characteristic, distributions of the mean coefficients of the viscous flow in the transient section of the streamlined surface are obtained, which enables one to determine the beginning of the laminar-turbulent transition and estimate the characteristics of the turbulent flow in the boundary layer.

  18. Autoignited laminar lifted flames of methane/hydrogen mixtures in heated coflow air

    KAUST Repository

    Choi, Byungchul

    2012-04-01

    Autoignited lifted flame behavior in laminar jets of methane/hydrogen mixture fuels has been investigated experimentally in heated coflow air. Three regimes of autoignited lifted flames were identified depending on initial temperature and hydrogen to methane ratio. At relatively high initial temperature, addition of a small amount of hydrogen to methane improved ignition appreciably such that the liftoff height decreased significantly. In this hydrogen-assisted autoignition regime, the liftoff height increased with jet velocity, and the characteristic flow time - defined as the ratio of liftoff height to jet velocity - correlated well with the square of the adiabatic ignition delay time. At lower temperature, the autoignited lifted flame demonstrated a unique feature in that the liftoff height decreased with increasing jet velocity. Such behavior has never been observed in lifted laminar and turbulent jet flames. A transition regime existed between these two regimes at intermediate temperature. © 2011 The Combustion Institute.

  19. Correlation of Water Frost Porosity in Laminar Flow over Flat Surfaces

    Science.gov (United States)

    Kandula, Max

    2011-01-01

    A dimensionless correlation has been proposed for water frost porosity expressing its dependence on frost surface temperature and Reynolds number for laminar forced flow over a flat surface. The correlation is presented in terms of a dimensionless frost surface temperature scaled with the cold plate temperature, and the freezing temperature. The flow Reynolds number is scaled with reference to the critical Reynolds number for laminar-turbulent transition. The proposed correlation agrees satisfactorily with the simultaneous measurements of frost density and frost surface temperature covering a range of plate temperature, ambient air velocity, humidity, and temperature. It is revealed that the frost porosity depends primarily on the frost surface and the plate temperatures and the flow Reynolds number, and is only weakly dependent on the relative humidity. The results also point out the general character of frost porosity displaying a decrease with an increase in flow Reynolds number.

  20. Investigation on the properties of a laminar grating as a soft x-ray beam splitter

    International Nuclear Information System (INIS)

    Liu Ying; Fuchs, Hans-Joerg; Liu Zhengkun; Chen Huoyao; He Shengnan; Fu Shaojun; Kley, Ernst-Bernhard; Tuennermann, Andreas

    2010-01-01

    Laminar-type gratings as soft x-ray beam splitters for interferometry are presented. Gold-coated grating beam splitters with 1000 lines/mm are designed for grazing incidence operation at 13.9nm. They are routinely fabricated using electron beam lithography and ion etching techniques. The laminar grating is measured to have almost equal absolute efficiencies of about 20% in the zeroth and -1st orders, which enables a fringe visibility up to 0.99 in the interferometer. The discrepancy of the grating profiles between the optimized theoretical and the experimental results is analyzed according to the comparison of the optimized simulation results and the measurement realization of the grating efficiencies. By a precise control of the grating profile, the grating efficiency in the -1st order and the fringe visibility could be improved to 25% and 1, respectively.

  1. Analysis of the flamelet concept in the numerical simulation of laminar partially premixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Consul, R.; Oliva, A.; Perez-Segarra, C.D.; Carbonell, D. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), Colom 11, E-08222, Terrassa, Barcelona (Spain); de Goey, L.P.H. [Eindhoven University of Technology, Department of Mechanical Engineering, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

    2008-04-15

    The aim of this work is to analyze the application of flamelet models based on the mixture fraction variable and its dissipation rate to the numerical simulation of partially premixed flames. Although the main application of these models is the computation of turbulent flames, this work focuses on the performance of flamelet concept in laminar flame simulations removing, in this way, turbulence closure interactions. A well-known coflow methane/air laminar flame is selected. Five levels of premixing are taken into account from an equivalence ratio {phi}={infinity} (nonpremixed) to {phi}=2.464. Results obtained using the flamelet approaches are compared to data obtained from the detailed solution of the complete transport equations using primitive variables. Numerical simulations of a counterflow flame are also presented to support the discussion of the results. Special emphasis is given to the analysis of the scalar dissipation rate modeling. (author)

  2. Biomimetic structures for fluid drag reduction in laminar and turbulent flows

    International Nuclear Information System (INIS)

    Jung, Yong Chae; Bhushan, Bharat

    2010-01-01

    Biomimetics allows one to mimic nature to develop materials and devices of commercial interest for engineers. Drag reduction in fluid flow is one of the examples found in nature. In this study, nano, micro, and hierarchical structures found in lotus plant surfaces, as well as shark skin replica and a rib patterned surface to simulate shark skin structure were fabricated. Drag reduction efficiency studies on the surfaces were systematically carried out using water flow. An experimental flow channel was used to measure the pressure drop in laminar and turbulent flows, and the trends were explained in terms of the measured and predicted values by using fluid dynamics models. The slip length for various surfaces in laminar flow was also investigated based on the measured pressure drop. For comparison, the pressure drop for various surfaces was also measured using air flow.

  3. Features of the laminar-turbulent transition in supersonic axisymmetric microjets

    Science.gov (United States)

    Maslov, A. A.; Aniskin, V. M.; Mironov, S. G.

    2016-10-01

    In this paper, a supersonic core length of microjets is studied in terms of laminar-turbulent transition in the microjet mixing layer. Previously, it was discovered that this transition has a determining influence on the supersonic core length. A possibility of simulation of microjet flows is estimated through the use of Reynolds number computed by the nozzle diameter and the nozzle exit gas parameters. These experimental data were obtained using Pitot tube when the jets escaping from the nozzle of 0.6 mm into the low-pressure space. This experiment made it possible to achieve a large jet pressure ratio when the Reynolds number values were low which specify the microjets' behavior. The supersonic core length, phase of the laminar-turbulent transition and flow characteristics in the space are obtained. Such an approach provides simulation of the characteristics of microjets and macrojets, and also explains preliminary proposition and some data obtained for microjets.

  4. Measurements and Experimental Database Review for Laminar Flame Speed Premixed Ch4/Air Flames

    Science.gov (United States)

    Zubrilin, I. A.; Matveev, S. S.; Matveev, S. G.; Idrisov, D. V.

    2018-01-01

    Laminar flame speed (SL ) of CH4 was determined at atmospheric pressure and initial gas temperatures in range from 298 to 358 K. The heat flux method was employed to measure the flame speed in non-stretched flames. The kinetic mechanism GRI 3.0 [1] were used to simulate SL . The measurements were compared with available literature results. The data determined with the heat flux method agree with some previous burner measurements and disagree with the data from some vessel closed method and counterflow method. The GRI 3.0 mechanism was able to reproduce the present experiments. Laminar flame speed was determined at pressures range from of 1 to 20 atmospheres through mechanism GRI 3.0. Based on experimental data and calculations was obtained SL dependence on pressure and temperature. The resulting of dependence recommended use during the numerical simulation of methane combustion.

  5. An experimental investigation of laminar free convection from a vertical flat plate at general boundary condition

    International Nuclear Information System (INIS)

    Aharon, J.; Lahav, C.; Kalman, H.; Shai, I.

    1996-01-01

    The present work deals with natural convection on a vertical flat plate, where one side of the plate is exposed to an environment of constant temperature - T a , with which heat is exchanged at an effective heat transfer coefficient, Glen. The other side of the plate is exposed to a fluid at a different temperature -T ∞ . The temperature gradient induces a natural convection in the fluid. The present investigation treats the heat transfer problem in the laminar cone in air (P r =1). An experimental apparatus has been constructed to confirm the heat transfer features predicted analytically in previous work. The local experimental Nusselt number was correlated with the modified Rayleigh number, for the laminar range. (authors)

  6. Effect of aspect ratio on the laminar-to-turbulent transition in rectangular channel

    International Nuclear Information System (INIS)

    Wang Chang; Gao Puzhen; Tan Sichao; Xu Chao

    2012-01-01

    Highlights: ► Effect of aspect ratio on the transition Reynolds number in rectangular channel is studied. ► Prediction correlation for transition Reynolds number is proposed. ► The initiation location of flow transition is studied. - Abstract: The critical Reynolds number of the laminar-to-turbulent transition in the rectangular channel is investigated based on the energy gradient method. The results show that the critical Reynolds number decreases with the increasing aspect ratio. However, the relative location of laminar breakdown does not migrate significantly with the variation of the aspect ratio. In addition, a theoretical correlation as a function of the aspect ratio is proposed to calculate the transition Reynolds number, and the predicted values are in good agreement with the experimental data obtained in the published literatures.

  7. Histopathological hoof laminar changes in horses with Pituitary Pars Intermedia Adenoma: cases report

    Directory of Open Access Journals (Sweden)

    L. M. Laskoski

    2015-10-01

    Full Text Available ABSTRACTLaminitis in horses is often associated with endocrine disorders, especially the pituitary pars intermedia dysfunction (PPID in older animals. Morphologic exams of the laminar tissue of the hoof were performed in two horses with suspected PPID, with no clinical signs of laminitis. Changes compatible with laminitis of endocrine origin were observed, such as rounding of the nuclei of the basal cells, thinning and stretching of the secondary epidermal laminae and tissue proliferation. PPID horses with no clinical signs of laminitis may be affected by lesions of the laminar tissue of the hoof that compromise the integrity of the dermal-epidermal junction and may develop clinical symptoms of the disease. It has been suggested that the development stage of endocrine laminitis is longer, but further studies should be conducted to confirm it.

  8. Laminar and Temporal Expression Dynamics of Coding and Noncoding RNAs in the Mouse Neocortex

    Directory of Open Access Journals (Sweden)

    Sofia Fertuzinhos

    2014-03-01

    Full Text Available The hallmark of the cerebral neocortex is its organization into six layers, each containing a characteristic set of cell types and synaptic connections. The transcriptional events involved in laminar development and function still remain elusive. Here, we employed deep sequencing of mRNA and small RNA species to gain insights into transcriptional differences among layers and their temporal dynamics during postnatal development of the mouse primary somatosensory neocortex. We identify a number of coding and noncoding transcripts with specific spatiotemporal expression and splicing patterns. We also identify signature trajectories and gene coexpression networks associated with distinct biological processes and transcriptional overlap between these processes. Finally, we provide data that allow the study of potential miRNA and mRNA interactions. Overall, this study provides an integrated view of the laminar and temporal expression dynamics of coding and noncoding transcripts in the mouse neocortex and a resource for studies of neurodevelopment and transcriptome.

  9. Laminar/transition sweeping flow-mixing model for wire-wrapped LMFBR assemblies

    International Nuclear Information System (INIS)

    Burns, K.F.; Rohsenow, W.M.; Todreas, N.E.

    1980-07-01

    Recent interest in analyzing the thermal hydraulic characteristics of LMFBR assemblies operating in the mixed convection regime motivates the extension of the aforementioned turbulent sweeping flow model to low Reynolds number flows. The accuracy to which knowledge of the mixing parameters is required has not been well determined, due to the increased influence of conduction and buoyancy effects with respect to energy transport at low Reynolds numbers. This study represents a best estimate attempt to correlate the existing low Reynolds number sweeping flow data. The laminar/transition model which is presented is expected to be useful in anayzing mixed convection conditions. However, the justification for making additional improvemements is contingent upon two factors. First, the ability of the proposed laminar/transition model to predict additional low Reynolds number sweeping flow data for other geometries needs to be investigated. Secondly, the sensitivity of temperature predictions to uncertainties in the values of the sweeping flow parameters should be quantified

  10. A numerical investigation of laminar forced convection in a solar collector with non-circular duct

    Science.gov (United States)

    Janusz Teleszewski, Tomasz

    2017-11-01

    This paper presents a two-dimensional numerical study to investigate laminar flow in a flat plate solar collector with non-circular duct (regular polygonal, elliptical, and Cassini oval shape) featuring forced convection with constant axial wall heat flux and constant peripheral wall temperature (H1 condition). Applying the velocity profile obtained for the duct laminar flow, the energy equation was solved exactly for the constant wall heat flux using the Boundary Element Method (BEM). Poiseuille and Nusselt numbers were obtained for flows having a different number of geometrical factors. The results are presented and discussed in the form of tables and graphs. The area goodness factor and volume goodness factor are calculated. The predicted correlations for Poiseuille and Nusselt numbers may be a very useful resource for the design and optimization of solar collectors with non-circular ducts.

  11. Assessment of CFD Capability for Hypersonic Shock Wave Laminar Boundary Layer Interactions

    OpenAIRE

    Mehrnaz Rouhi Youssefi; Doyle Knight

    2017-01-01

    The goal of this study is to assess CFD capability for the prediction of shock wave laminar boundary layer interactions at hypersonic velocities. More specifically, the flow field over a double-cone configuration is simulated using both perfect gas and non-equilibrium Navier–Stokes models. Computations are compared with recent experimental data obtained from measurements conducted in the LENS XX (Large Energy National Shock Expansion Tunnel Version 2) at the Calspan University of Buffalo Rese...

  12. Effective thermal conductivity of superfluid helium: laminar, turbulent and ballistic regimes

    Directory of Open Access Journals (Sweden)

    Sciacca Michele

    2016-06-01

    Full Text Available In this paper we extend previous results on the effective thermal conductivity of liquid helium II in cylindrical channels to rectangular channels with high aspect ratio. The aim is to compare the results in the laminar regime, the turbulent regime and the ballistic regime, all of them obtained within a single mesoscopic formalism of heat transport, with heat flux as an independent variable.

  13. Numerical analysis of a hypersonic turbulent and laminar flow using a commercial CFD solver

    OpenAIRE

    Pajčin Miroslav P.; Simonović Aleksandar M.; Ivanov Toni D.; Komarov Dragan M.; Stupar Slobodan N.

    2017-01-01

    Computational fluid dynamics computations for two hypersonic flow cases using the commercial ANSYS FLUENT 16.2 CFD software were done. In this paper, an internal and external hypersonic flow cases were considered and analysis of the hypersonic flow using different turbulence viscosity models available in ANSYS FLUENT 16.2 as well as the laminar viscosity model were done. The obtained results were after compared and commented upon. [Project of the Serbian Ministry of Education, Science and Tec...

  14. The construction of a laminar-flow cell for neutron reflection studies

    International Nuclear Information System (INIS)

    Haemers, S.; Efimova, Y.M.; Well, A.A. van

    2005-01-01

    The characteristic time scale of adsorption has an important contribution to the history of adsorbed protein layers. Control over this time scale is achieved by designing a measuring cell with well-defined laminar liquid flow in parallel plate geometry to be used on a neutron reflectometer. Results obtained from adsorption experiments with lysozyme clearly show that there is an effect of adsorption time scales on the properties of adsorbed layers

  15. Feasibility Demonstration of Exciplex Fluorescence Measurements in Evaporating Laminar Sprays of Diesel Fuel

    Science.gov (United States)

    2011-05-15

    code) 1 FEASIBILITY DEMONSTRATION OF EXCIPLEX FLUORESCENCE MEASUREMENTS IN EVAPORATING LAMINAR SPRAYS OF DIESEL FUEL Final Technical Report Grant...fluorescence is found to increase with temperature up to 538 K and then declines. Fluorescence from the liquid phase, i.e. the exciplex (Naphthalene+TMPD...to have as well characterized a description of the spray environment and assess conclusively the potential of the exciplex approach for more

  16. Simulations and experiments of laminar heat transfer for Therminol heat transfer fluids in a rifled tube

    International Nuclear Information System (INIS)

    Xu, Weiguo; Ren, Depeng; Ye, Qing; Liu, Guodong; Lu, Huilin; Wang, Shuai

    2016-01-01

    Graphical abstract: Predicted laminar Nusselt number using regression correlation of Therminol-55 heat transfer fluid is in agreement with experiments in the rifled tube. - Highlights: • Heat transfer coefficient and friction factor are measured and predicted in the rifled tube. • Correlations for Nusselt number and friction factor are proposed. • The roughness height of 0.425 mm in transition SST model is suggested as an input parameter. • k–kl–ω transition and transition SST models are recommended for laminar–turbulent transition. • Thermal enhancement factor and synergy angle are predicted in the rifled tube. - Abstract: Simulations and experiments of flow and heat transfer behavior of Therminol-55 heat transfer fluid have been conducted in a horizontal rifled tube with outer diameter and inner diameter 25.0 and 20.0 mm, pitch and rib height of 12.0 and 1.0 mm, respectively. Numerical simulations of three-dimensional flow behavior of Therminol-55 heat transfer fluid are carried out using FLUENT code in the rifled tube. Experimental results show that the heat transfer and thermal performance of Therminol-55 heat transfer fluid in the rifled tube are considerably improved compared to those of the smooth tube. The Nusselt number increases with the increase of Reynolds number, and is from 3.5 to 5.1 times over the smooth tube. Also, the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.2 and 4.2 times over the smooth tube. Predictive Nusselt number and friction factor correlations have been presented. The numerical results show that the laminar flow model is valid only at lower Reynolds number in the developed laminar flow of rifled tube. The k–kl–ω transition model and transition SST model with roughness of 0.425 mm are recommended for the predictions of transition process from laminar to turbulent flow in the rifled tube.

  17. Numerical solution of inviscid and viscous laminar and turbulent flow around the airfoil

    Directory of Open Access Journals (Sweden)

    Slouka Martin

    2016-01-01

    Full Text Available This work deals with the 2D numerical solution of inviscid compressible flow and viscous compressible laminar and turbulent flow around the profile. In a case of turbulent flow algebraic Baldwin-Lomax model is used and compared with Wilcox k-omega model. Calculations are done for NACA 0012 and RAE 2822 airfoil profile for the different angles of upstream flow. Numerical results are compared and discussed with experimental data.

  18. Determination of the critical Shields number for particle erosion in laminar flow

    OpenAIRE

    Ouriemi , Malika; Aussillous , Pascale; Medale , Marc; Peysson , Yannick; Guazzelli , Élisabeth

    2007-01-01

    International audience; We present reproducible experimental measurements for the onset of grain motion in laminar flow and find a constant critical Shields number for particle erosion, i.e., c = 0.12± 0.03, over a large range of small particle Reynolds number: 1.5 10 −5 Re p 0.76. Comparison with previous studies found in the literature is provided.

  19. Analogy of convective heat transfer between developing laminar secondary flows in pipes

    OpenAIRE

    Ishigaki, Hiroshi; 石垣 博

    1998-01-01

    Analogy of convective heat transfer between developing laminar flows in curved pipes and orthogonally rotating pipes is described through similarity arguments and numerical computation. Governing parameters and a dimensionless axial distance are properly used for the respective flows. When the second parameter is large in each flow, it is shown that the temperature profiles and the Nusselt numbers of the two flows are approximately similar for the same values of the governing parameter, Prand...

  20. Laminar pattern of cholinergic and adrenergic receptors in rat visual cortex using quantitative receptor autoradiography

    International Nuclear Information System (INIS)

    Schliebs, R.; Walch, C.

    1989-01-01

    The laminar distribution of muscarinic acetylcholine receptors, including the M1-receptor subtype, of beta-adrenergic receptors, and noradrenaline uptake sites, was studied in the adult rat visual, frontal, somatosensory and motor cortex, using quantitative receptor autoradiography. In the visual cortex, the highest density of muscarinic acetylcholine receptors was found in layer I. From layer II/III to layer V binding decreases continueously reaching a constant binding level in layers V and VI. This laminar pattern of muscarinic receptor density differs somewhat from that observed in the non-visual cortical regions examined: layer II/III contained the highest receptor density followed by layer I and IV: lowest density was found in layer V and VI. The binding profile of the muscarinic cholinergic M1-subtype through the visual cortex shows a peak in cortical layer II and in the upper part of layer VI, whereas in the non-visual cortical regions cited the binding level was high in layer II/III, moderate in layer I and IV, and low in layer VI. Layers I to IV of the visual cortex contained the highest beta-adrenergic receptor densities, whereas only low binding levels were observed in the deeper layers. A similar laminar distribution was found also in the frontal, somatosensory and motor cortex. The density of noradrenaline uptake sites was high in all layers of the cortical regions studied, but with noradrenaline uptake sites somewhat more concentrated in the superficial layers than in deeper ones. The distinct laminar pattern of cholinergic and noradrenergic receptor sites indicates a different role for acetylcholine and noradrenaline in the functional anatomy of the cerebral cortex, and in particular, the visual cortex. (author)

  1. Laminar pattern of cholinergic and adrenergic receptors in rat visual cortex using quantitative receptor autoradiography

    Energy Technology Data Exchange (ETDEWEB)

    Schliebs, R; Walch, C [Leipzig Univ. (German Democratic Republic). Bereich Medizin; Stewart, M G [Open Univ., Milton Keynes (UK)

    1989-01-01

    The laminar distribution of muscarinic acetylcholine receptors, including the M1-receptor subtype, of beta-adrenergic receptors, and noradrenaline uptake sites, was studied in the adult rat visual, frontal, somatosensory and motor cortex, using quantitative receptor autoradiography. In the visual cortex, the highest density of muscarinic acetylcholine receptors was found in layer I. From layer II/III to layer V binding decreases continueously reaching a constant binding level in layers V and VI. This laminar pattern of muscarinic receptor density differs somewhat from that observed in the non-visual cortical regions examined: layer II/III contained the highest receptor density followed by layer I and IV: lowest density was found in layer V and VI. The binding profile of the muscarinic cholinergic M1-subtype through the visual cortex shows a peak in cortical layer II and in the upper part of layer VI, whereas in the non-visual cortical regions cited the binding level was high in layer II/III, moderate in layer I and IV, and low in layer VI. Layers I to IV of the visual cortex contained the highest beta-adrenergic receptor densities, whereas only low binding levels were observed in the deeper layers. A similar laminar distribution was found also in the frontal, somatosensory and motor cortex. The density of noradrenaline uptake sites was high in all layers of the cortical regions studied, but with noradrenaline uptake sites somewhat more concentrated in the superficial layers than in deeper ones. The distinct laminar pattern of cholinergic and noradrenergic receptor sites indicates a different role for acetylcholine and noradrenaline in the functional anatomy of the cerebral cortex, and in particular, the visual cortex. (author).

  2. Apparatus for diffusion separation

    International Nuclear Information System (INIS)

    Nierenberg, W.A.; Pontius, R.B.

    1976-01-01

    The method of testing the separation efficiency of porous permeable membranes is described which comprises causing a stream of a gaseous mixture to flow into contact with one face of a finely porous permeable membrane under such conditions that a major fraction of the mixture diffuses through the membrane, maintaining a rectangular cross section of the gaseous stream so flowing past said membrane, continuously recirculating the gas that diffuses through said membrane and continuously withdrawing the gas that does not diffuse through said membrane and maintaining the volume of said recirculating gas constant by continuously introducing into said continuously recirculating gas stream a mass of gas equivalent to that which is continuously withdrawn from said gas stream and comparing the concentrations of the light component in the entering gas, the withdrawn gas and the recirculated gas in order to determine the efficiency of said membrane

  3. Separation of gases

    International Nuclear Information System (INIS)

    Wang, C.G.

    1980-01-01

    A process for separating gaseous mixtures of molecules of different mass comprises the steps of: causing a rotational nozzle to eject a contiguous plurality of successive groups of molecules into an evacuated space, the groups mutually overlapping to form a continuous stream of the mixture in the form of an Archimedean spiral, allowing the molecules of each group of molecules to move in accordance with their thermal velocities for a predetermined period of time following ejection, thereby to allow each group of molecules to form a generally spherical configuration the outer portion of which will be enriched, in molecules of lighter mass, relative to the inner portion thereof, using a deflector means co-rotating with the rotating nozzle to deflect molecules, which have been allowed to move for the predetermined period of time in accordance with their thermal velocities, from at least one desired portion of the stream and using a stationary collector means to collect the deflected molecules. The process is described with reference to the separation of isotopes of uranium hexafluoride. (author)

  4. Soot Formation in Laminar Premixed Methane/Oxygen Flames at Atmospheric Pressure

    Science.gov (United States)

    Xu, F.; Lin, K.-C.; Faeth, G. M.

    1998-01-01

    Flame structure and soot formation were studied within soot-containing laminar premixed mc1hane/oxygen flames at atmospheric pressure. The following measurements were made: soot volume fractions by laser extinction, soot temperatures by multiline emission, gas temperatures (where soot was absent) by corrected fine-wire thermocouples, soot structure by thermophoretic sampling and transmission electron microscope (TEM), major gas species concentrations by sampling and gas chromatography, and gas velocities by laser velocimetry. Present measurements of gas species concentrations were in reasonably good agreement with earlier measurements due to Ramer et al. as well as predictions based on the detailed mechanisms of Frenklach and co-workers and Leung and Lindstedt: the predictions also suggest that H atom concentrations are in local thermodynamic equilibrium throughout the soot formation region. Using this information, it was found that measured soot surface growth rates could be correlated successfully by predictions based on the hydrogen-abstraction/carbon-addition (HACA) mechanisms of both Frenklach and co-workers and Colket and Hall, extending an earlier assessment of these mechanisms for premixed ethylene/air flames to conditions having larger H/C ratios and acetylene concentrations. Measured primary soot particle nucleation rates were somewhat lower than the earlier observations for laminar premixed ethylene/air flames and were significantly lower than corresponding rates in laminar diffusion flames. for reasons that still must be explained.

  5. Experimental analysis of colloid capture by a cylindrical collector in laminar overland flow.

    Science.gov (United States)

    Wu, Lei; Gao, Bin; Muñoz-Carpena, Rafael

    2011-09-15

    Although colloid-facilitated contaminant transport in water flow is a well-known contamination process, little research has been conducted to investigate the transport of colloidal particles through emergent vegetation in overland flow. In this work, a series of laboratory experiments were conducted to measure the single-collector contact efficiency (η(0)) of colloid capture by a simulated plant stem in laminar lateral flow. Fluorescent microspheres of various sizes were used as experimental colloids. The colloid suspensions were applied to a glass cylinder installed in a small size flow chamber at different flow rates. Two cylinder sizes were tested in the experiment and silicone grease was applied to the cylinder surface to make it favorable for colloid deposition. Our results showed that increases in flow rate and collector size reduced the value of η(0) and a minimum value of η(0) might exist for a colloid size. The experimental data were compared to theoretical predictions of different single-collector contact efficiency models. The results indicated that existing single-collector contact efficiency models underestimated the η(0) of colloid capture by the cylinders in laminar overland flow. A regression equation of η(0) as a function of collector Reynolds number (Re(c)) and Peclet number (N(Pe)) was developed and fit the experimental data very well (R(2) > 0.98). This regression equation can be used to help construct and refine mathematical models of colloid transport and filtration in laminar overland flow on vegetated surfaces.

  6. Laminar and turbulent nozzle-jet flows and their acoustic near-field

    International Nuclear Information System (INIS)

    Bühler, Stefan; Obrist, Dominik; Kleiser, Leonhard

    2014-01-01

    We investigate numerically the effects of nozzle-exit flow conditions on the jet-flow development and the near-field sound at a diameter-based Reynolds number of Re D = 18 100 and Mach number Ma = 0.9. Our computational setup features the inclusion of a cylindrical nozzle which allows to establish a physical nozzle-exit flow and therefore well-defined initial jet-flow conditions. Within the nozzle, the flow is modeled by a potential flow core and a laminar, transitional, or developing turbulent boundary layer. The goal is to document and to compare the effects of the different jet inflows on the jet flow development and the sound radiation. For laminar and transitional boundary layers, transition to turbulence in the jet shear layer is governed by the development of Kelvin-Helmholtz instabilities. With the turbulent nozzle boundary layer, the jet flow development is characterized by a rapid changeover to a turbulent free shear layer within about one nozzle diameter. Sound pressure levels are strongly enhanced for laminar and transitional exit conditions compared to the turbulent case. However, a frequency and frequency-wavenumber analysis of the near-field pressure indicates that the dominant sound radiation characteristics remain largely unaffected. By applying a recently developed scaling procedure, we obtain a close match of the scaled near-field sound spectra for all nozzle-exit turbulence levels and also a reasonable agreement with experimental far-field data

  7. Laminar motion of the incompressible fluids in self-acting thrust bearings with spiral grooves.

    Science.gov (United States)

    Velescu, Cornel; Popa, Nicolae Calin

    2014-01-01

    We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the "pumping" direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances) and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc.), for the laminar and permanent motion regime.

  8. Laminar Motion of the Incompressible Fluids in Self-Acting Thrust Bearings with Spiral Grooves

    Directory of Open Access Journals (Sweden)

    Cornel Velescu

    2014-01-01

    Full Text Available We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the “pumping” direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc., for the laminar and permanent motion regime.

  9. 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.

  10. Transient convective heat transfer to laminar flow from a flat plate with constant heat capacity

    International Nuclear Information System (INIS)

    Hanawa, Juichi

    1980-01-01

    Most basic transient heat transfer problem is the transient response characteristics of forced convection heat transfer in the flow along a flat plate or in a tube. In case of the laminar flow along a flat plate, the profile method using steady temperature distribution has been mostly adopted, but its propriety has not been clarified yet. About the unsteady heat transfer in the laminar flow along a flat plate, the analysis or experiment evaluating the heat capacity of the flat plate exactly was never carried out. The purpose of this study is to determine by numerical calculation the unsteady characteristics of the boundary layer in laminar flow and to confirm them by experiment concerning the unsteady heat transfer when a flat plate with a certain heat capacity is placed in parallel in uniform flow and given a certain quantity of heat generation suddenly. The basic equation and the solution are given, and the method of numerical calculation and the result are explained. The experimental setup and method, and the experimental results are shown. Both results were in good agreement, and the response of wall temperature, the response of Nusselt number and the change of temperature distribution in course of time were able to be determined by applying Laplace transformation and numerical Laplace inverse transformation to the equation. (Kako, I.)

  11. EXPERIMENTAL AND MODELING STUDY OF PREMIXED LAMINAR FLAMES OF ETHANOL AND METHANE.

    Science.gov (United States)

    Tran, Luc-Sy; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique

    2013-04-18

    To better understand the chemistry of the combustion of ethanol, the structure of five low pressure laminar premixed flames has been investigated: a pure methane flame (φ=1), three pure ethanol flames (φ=0.7, 1.0, and 1.3), and an ethanol/methane mixture flames (φ=1). The flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 64.3 cm/s at 333 K. The results consist of mole fraction profiles of 20 species measured as a function of the height above the burner by probe sampling followed by online gas chromatography analyses. A mechanism for the oxidation of ethanol was proposed. The reactions of ethanol and acetaldehyde were updated and include recent theoretical calculations while that of ethenol, dimethyl ether, acetone, and propanal were added in the mechanism. This mechanism was also tested against experimental results available in the literature for laminar burning velocities and laminar premixed flame where ethenol was detected. The main reaction pathways of consumption of ethanol are analyzed. The effect of the branching ratios of reaction C 2 H 5 OH+OH→Products+H 2 O is also discussed.

  12. Laminar recordings in frontal cortex suggest distinct layers for maintenance and control of working memory.

    Science.gov (United States)

    Bastos, André M; Loonis, Roman; Kornblith, Simon; Lundqvist, Mikael; Miller, Earl K

    2018-01-30

    All of the cerebral cortex has some degree of laminar organization. These different layers are composed of neurons with distinct connectivity patterns, embryonic origins, and molecular profiles. There are little data on the laminar specificity of cognitive functions in the frontal cortex, however. We recorded neuronal spiking/local field potentials (LFPs) using laminar probes in the frontal cortex (PMd, 8A, 8B, SMA/ACC, DLPFC, and VLPFC) of monkeys performing working memory (WM) tasks. LFP power in the gamma band (50-250 Hz) was strongest in superficial layers, and LFP power in the alpha/beta band (4-22 Hz) was strongest in deep layers. Memory delay activity, including spiking and stimulus-specific gamma bursting, was predominately in superficial layers. LFPs from superficial and deep layers were synchronized in the alpha/beta bands. This was primarily unidirectional, with alpha/beta bands in deep layers driving superficial layer activity. The phase of deep layer alpha/beta modulated superficial gamma bursting associated with WM encoding. Thus, alpha/beta rhythms in deep layers may regulate the superficial layer gamma bands and hence maintenance of the contents of WM. Copyright © 2018 the Author(s). Published by PNAS.

  13. A uniform laminar air plasma plume with large volume excited by an alternating current voltage

    Science.gov (United States)

    Li, Xuechen; Bao, Wenting; Chu, Jingdi; Zhang, Panpan; Jia, Pengying

    2015-12-01

    Using a plasma jet composed of two needle electrodes, a laminar plasma plume with large volume is generated in air through an alternating current voltage excitation. Based on high-speed photography, a train of filaments is observed to propagate periodically away from their birth place along the gas flow. The laminar plume is in fact a temporal superposition of the arched filament train. The filament consists of a negative glow near the real time cathode, a positive column near the real time anode, and a Faraday dark space between them. It has been found that the propagation velocity of the filament increases with increasing the gas flow rate. Furthermore, the filament lifetime tends to follow a normal distribution (Gaussian distribution). The most probable lifetime decreases with increasing the gas flow rate or decreasing the averaged peak voltage. Results also indicate that the real time peak current decreases and the real time peak voltage increases with the propagation of the filament along the gas flow. The voltage-current curve indicates that, in every discharge cycle, the filament evolves from a Townsend discharge to a glow one and then the discharge quenches. Characteristic regions including a negative glow, a Faraday dark space, and a positive column can be discerned from the discharge filament. Furthermore, the plasma parameters such as the electron density, the vibrational temperature and the gas temperature are investigated based on the optical spectrum emitted from the laminar plume.

  14. Laminar shear stress modulates endothelial luminal surface stiffness in a tissue-specific manner.

    Science.gov (United States)

    Merna, Nick; Wong, Andrew K; Barahona, Victor; Llanos, Pierre; Kunar, Balvir; Palikuqi, Brisa; Ginsberg, Michael; Rafii, Shahin; Rabbany, Sina Y

    2018-04-17

    Endothelial cells form vascular beds in all organs and are exposed to a range of mechanical forces that regulate cellular phenotype. We sought to determine the role of endothelial luminal surface stiffness in tissue-specific mechanotransduction of laminar shear stress in microvascular mouse cells and the role of arachidonic acid in mediating this response. Microvascular mouse endothelial cells were subjected to laminar shear stress at 4 dynes/cm 2 for 12 hours in parallel plate flow chambers that enabled real-time optical microscopy and atomic force microscopy measurements of cell stiffness. Lung endothelial cells aligned parallel to flow, while cardiac endothelial cells did not. This rapid alignment was accompanied by increased cell stiffness. The addition of arachidonic acid to cardiac endothelial cells increased alignment and stiffness in response to shear stress. Inhibition of arachidonic acid in lung endothelial cells and embryonic stem cell-derived endothelial cells prevented cellular alignment and decreased cell stiffness. Our findings suggest that increased endothelial luminal surface stiffness in microvascular cells may facilitate mechanotransduction and alignment in response to laminar shear stress. Furthermore, the arachidonic acid pathway may mediate this tissue-specific process. An improved understanding of this response will aid in the treatment of organ-specific vascular disease. © 2018 John Wiley & Sons Ltd.

  15. Development of Advanced High Lift Leading Edge Technology for Laminar Flow Wings

    Science.gov (United States)

    Bright, Michelle M.; Korntheuer, Andrea; Komadina, Steve; Lin, John C.

    2013-01-01

    This paper describes the Advanced High Lift Leading Edge (AHLLE) task performed by Northrop Grumman Systems Corporation, Aerospace Systems (NGAS) for the NASA Subsonic Fixed Wing project in an effort to develop enabling high-lift technology for laminar flow wings. Based on a known laminar cruise airfoil that incorporated an NGAS-developed integrated slot design, this effort involved using Computational Fluid Dynamics (CFD) analysis and quality function deployment (QFD) analysis on several leading edge concepts, and subsequently down-selected to two blown leading-edge concepts for testing. A 7-foot-span AHLLE airfoil model was designed and fabricated at NGAS and then tested at the NGAS 7 x 10 Low Speed Wind Tunnel in Hawthorne, CA. The model configurations tested included: baseline, deflected trailing edge, blown deflected trailing edge, blown leading edge, morphed leading edge, and blown/morphed leading edge. A successful demonstration of high lift leading edge technology was achieved, and the target goals for improved lift were exceeded by 30% with a maximum section lift coefficient (Cl) of 5.2. Maximum incremental section lift coefficients ( Cl) of 3.5 and 3.1 were achieved for a blown drooped (morphed) leading edge concept and a non-drooped leading edge blowing concept, respectively. The most effective AHLLE design yielded an estimated 94% lift improvement over the conventional high lift Krueger flap configurations while providing laminar flow capability on the cruise configuration.

  16. A parametric study of AC electric field-induced toroidal vortex formation in laminar nonpremixed coflow flames

    KAUST Repository

    Xiong, Yuan

    2017-05-02

    This study presents an experimental work investigating the controlling parameters on the formation of an electrically-induced inner toroidal vortex (ITV) near a nozzle rim in small, laminar nonpremixed coflow flames, when an alternating current is applied to the nozzle. A systematic parametric study was conducted by varying the flow parameters of the fuel and coflowing-air velocities, and the nozzle diameter. The fuels tested were methane, ethylene, ethane, propane, n-butane, and i-butane, each representing different ion-generation characteristics and sooting tendencies. The results showed that the fluid dynamic effects on ITV formation were weak, causing only mild variation when altering flow velocities. However, increased fuel velocity resulted in increased polycyclic aromatic hydrocarbon (PAH) formation, which promoted ITV formation. When judging the ITV-formation tendency based on critical applied voltage and frequency, it was qualitatively well correlated with the PAH concentration and the relative location of PAHs to the nozzle rim. The sooting tendency of the fuels did not affect the results much. A change in the nozzle diameter highlighted the importance of the relative distance between the PAH zone and the nozzle rim, indicating the role of local electric-field intensity on ITV formation. Detailed onset conditions, characteristics of near-nozzle flow patterns, and PAH distributions are also discussed.

  17. New separation technique. Catalytically functionated separation membrane

    Energy Technology Data Exchange (ETDEWEB)

    Urgami, Tadashi [Kansai Univ., Osaka (Japan)

    1989-02-01

    This report introduces research examples, showing the fundamental principle of the membrane by separating the catalytically functionated separation membrane into enzyme fixing separation membrane, polymerized metal complex separation membrane and polymer catalyst separation membrane. This membrane can achieve both functions of separation and catalytic reaction simultaneously and has sufficient possibility to combine powerful functions. Enzyme fixing separation membrane is prepared by carrier combination method, bridging method or covering method and the enzyme fixing method with polymerized complex in which enzyme is controlled to prevent the activity lowering as much as possible and enzyme is fixed from an aqueous solution into polymer membrane. This membrane is applied to the continuous manufacturing of invert sugar from cane sugar and adsorption and removing of harmful substances from blood by utilizing both micro-capsuled urease and active carbon. Alginic acid-copper (II) complex membrane is used for the polymerized metal complex membrane and polystyrene sulfonate membrane is used for the polymer catalyst separation membrane. 28 refs., 4 figs., 1 tabs.

  18. Taylor dispersion in premixed combustion: Questions from turbulent combustion answered for laminar flames

    Science.gov (United States)

    Daou, Joel; Pearce, Philip; Al-Malki, Faisal

    2018-02-01

    We present a study of Taylor dispersion in premixed combustion and use it to clarify fundamental issues related to flame propagation in a flow field. In particular, simple analytical formulas are derived for variable density laminar flames with arbitrary Lewis number Le providing clear answers to important questions arising in turbulent combustion, when these questions are posed for the case of one-scale laminar parallel flows. Exploiting, in the context of a laminar Poiseuille flow model, a thick flame distinguished asymptotic limit for which the flow amplitude is large with the Reynolds number Re fixed, three main contributions are made. First, a link is established between Taylor dispersion [G. Taylor, Proc. R. Soc. London Ser. A 219, 186 (1953), 10.1098/rspa.1953.0139] and Damköhler's second hypothesis [G. Damköhler, Ber. Bunsen. Phys. Chem. 46, 601 (1940)] by describing analytically the enhancement of the effective propagation speed UT due to small flow scales. More precisely, it is shown that Damköhler's hypothesis is only partially correct for one-scale parallel laminar flows. Specifically, while the increase in UT due to the flow is shown to be directly associated with the increase in the effective diffusivity as suggested by Damköhler, our results imply that UT˜Re (for Re≫1 ) rather than UT˜√{Re} , as implied by Damköhler's hypothesis. Second, it is demonstrated analytically and confirmed numerically that, when UT is plotted versus the flow amplitude for fixed values of Re, the curve levels off to a constant value depending on Re. We may refer to this effect as the laminar bending effect as it mimics a similar bending effect known in turbulent combustion. Third, somewhat surprising implications associated with the dependence of UT and of the effective Lewis number Leeff on the flow are reported. For example, Leeff is found to vary from Le to Le-1 as Re varies from small to large values. Also, UT is found to be a monotonically increasing function

  19. A laminar flow unit for the care of critically ill newborn infants

    Directory of Open Access Journals (Sweden)

    Perez JM

    2013-10-01

    Full Text Available Jose MR Perez,1 Sergio G Golombek,2 Carlos Fajardo,3 Augusto Sola41Stella Maris Hospital, International Neurodevelopment Neonatal Center (CINN, Sao Paulo, Brazil; 2M Fareri Children’s Hospital, Westchester Medical Center, New York Medical College, Valhalla, NY, USA; 3University of Calgary, Calgary, Canada; 4St Jude Hospital, Fullerton, California, CA, USAIntroduction: Medical and nursing care of newborns is predicated on the delicate control and balance of several vital parameters. Closed incubators and open radiant warmers are the most widely used devices for the care of neonates in intensive care; however, several well-known limitations of these devises have not been resolved. The use of laminar flow is widely used in many fields of medicine, and may have applications in neonatal care.Objective: To describe the neonatal laminar flow unit, a new equipment we designed for care of ill newborns.Methods: The idea, design, and development of this device was completed in Sao Paulo, Brazil. The unit is an open mobile bed designed with the objective of maintaining the advantages of the incubator and radiant warmer, while overcoming some of their inherent shortcomings; these shortcomings include noise, magnetic fields and acrylic barriers in incubators, and lack of isolation and water loss through skin in radiant warmers. The unit has a pump that aspirates environmental air which is warmed by electrical resistance and decontaminated with High Efficiency Particulate Air Filter (HEPA filters (laminar flow. The flow is directed by an air flow directioner. The unit has an embedded humidifier to increase humidity in the infant’s microenvironment and a servo control mechanism for regulation of skin temperature.Results: The laminar flow unit is open and facilitates access of care providers and family, which is not the case in incubators. It provides warming by convection at an air velocity of 0.45 m/s, much faster than an incubator (0.1 m/s. The system

  20. Laminar shear flow increases hydrogen sulfide and activates a nitric oxide producing signaling cascade in endothelial cells.

    Science.gov (United States)

    Huang, Bin; Chen, Chang-Ting; Chen, Chi-Shia; Wang, Yun-Ming; Hsieh, Hsyue-Jen; Wang, Danny Ling

    2015-09-04

    Laminar shear flow triggers a signaling cascade that maintains the integrity of endothelial cells (ECs). Hydrogen sulfide (H2S), a new gasotransmitter is regarded as an upstream regulator of nitric oxide (NO). Whether the H2S-generating enzymes are correlated to the enzymes involved in NO production under shear flow conditions remains unclear as yet. In the present study, the cultured ECs were subjected to a constant shear flow (12 dyn/cm(2)) in a parallel flow chamber system. We investigated the expression of three key enzymes for H2S biosynthesis, cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), and 3-mercapto-sulfurtransferase (3-MST). Shear flow markedly increased the level of 3-MST. Shear flow enhanced the production of H2S was determined by NBD-SCN reagent that can bind to cysteine/homocystein. Exogenous treatment of NaHS that can release gaseous H2S, ECs showed an increase of phosphorylation in Akt(S473), ERK(T202/Y204) and eNOS(S1177). This indicated that H2S can trigger the NO-production signaling cascade. Silencing of CSE, CBS and 3-MST genes by siRNA separately attenuated the phosphorylation levels of Akt(S473) and eNOS(S1177) under shear flow conditions. The particular mode of shear flow increased H2S production. The interplay between H2S and NO-generating enzymes were discussed in the present study. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Magnetic separation of algae

    Science.gov (United States)

    Nath, Pulak; Twary, Scott N.

    2016-04-26

    Described herein are methods and systems for harvesting, collecting, separating and/or dewatering algae using iron based salts combined with a magnetic field gradient to separate algae from an aqueous solution.

  2. Separation anxiety in children

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/001542.htm Separation anxiety in children To use the sharing features on this page, please enable JavaScript. Separation anxiety in children is a developmental stage in which ...

  3. Chromatographic separations of stereoisomers

    Energy Technology Data Exchange (ETDEWEB)

    Souter, R.W.

    1985-01-01

    This text covers both diastereomers and enantiomers; describes techniques for GC, HPLC, and other chromatographic methods; and tabulates results of various applications by both techniques and compound class. It provides current knowledge about separation mechanisms and interactions of asymmetric molecules, as well as experimental and commercial materials such as columns, instruments, and derivatization reagents. The contents also include stereoisomer separations by gas chromatography. Stereoisomer separations by high-performance liquid chromatography. Stereoisomer separations by other chromatographic techniques.

  4. Temperature decline thermography for laminar-turbulent transition detection in aerodynamics

    Science.gov (United States)

    von Hoesslin, Stefan; Stadlbauer, Martin; Gruendmayer, Juergen; Kähler, Christian J.

    2017-09-01

    Detailed knowledge about laminar-turbulent transition and heat transfer distribution of flows around complex aerodynamic components are crucial to achieve highest efficiencies in modern aerodynamical systems. Several measurement techniques have been developed to determine those parameters either quantitatively or qualitatively. Most of them require extensive instrumentation or give unreliable results as the boundary conditions are often not known with the required precision. This work introduces the simple and robust temperature decline method to qualitatively detect the laminar-turbulent transition and the respective heat transfer coefficients on a surface exposed to an air flow, according to patent application Stadlbauer et al. (Patentnr. WO2014198251 A1, 2014). This method provides results which are less sensitive to control parameters such as the heat conduction into the blade material and temperature inhomogeneities in the flow or blade. This method was applied to measurements with NACA0018 airfoils exposed to the flow of a calibration-free jet at various Reynolds numbers and angles of attack. For data analysis, a post-processing method was developed and qualified to determine a quantity proportional to the heat transfer coefficient into the flow. By plotting this quantity for each pixel of the surface, a qualitative, two-dimensional heat transfer map was obtained. The results clearly depicted the areas of onset and end of transition over the full span of the model and agreed with the expected behavior based on the respective flow condition. To validate the approach, surface hotfilm measurements were conducted simultaneously on the same NACA profile. Both techniques showed excellent agreement. The temperature decline method allows to visualize laminar-turbulent transitions on static or moving parts and can be applied on a very broad range of scales—from tiny airfoils up to large airplane wings.

  5. An Experimental Measurement on Laminar Burning Velocities and Markstein Length of Iso-Butane-Air Mixtures at Ambient Conditions

    Directory of Open Access Journals (Sweden)

    Yousif Alaeldeen Altag

    2016-01-01

    Full Text Available In the present work, experimental investigation on laminar combustion of iso-butane-air mixtures was conducted in constant volume explosion vessel. The experiments were conducted at wide range of equivalence ratios ranging between Ф = 0.6 and 1.4 and atmospheric pressure of 0.1 MPa and ambient temperature of 303K. Using spherically expanding flame method, flame parameters including stretched, unstretched flame propagation speeds, laminar burning velocities and Markstein length were calculated. For laminar burning velocities the method of error bars of 95% confidence level was applied. In addition, values of Markstein lengths were measured in wide range of equivalence ratios to study the influence of stretch rate on flame instability and burning velocity. It was found that the stretched flame speed and laminar burning velocities increased with equivalence ratios and the peak value was obtained at equivalence ratio of Ф = 1.1. The Markstein length decreased with the increases in equivalence ratios, which indicates that the diffusion thermal flame instability increased at high equivalence ratios in richer mixture side. However, the total deviations in the laminar burning velocities have discrepancies of 1.2-2.9% for all investigated mixtures.

  6. Bone augmentation of the osteo-odonto alveolar lamina in MOOKP--will it delay laminar resorption?

    Science.gov (United States)

    Iyer, Geetha; Srinivasan, Bhaskar; Agarwal, Shweta; Rishi, Ekta; Rishi, Pukhraj; Rajan, Gunaseelan; Shanmugasundaram, Shanmugasundaram

    2015-07-01

    We aimed to describe a new technique and analyse the early outcomes of augmenting the canine tooth using a mandibular bone graft in an attempt to delay or retard the process of laminar resorption following the modified osteo odonto keratoprosthesis (MOOKP) procedure. This was a retrospective case series. Eyes that underwent the bone augmentation procedure between December 2012 and February 2014 were retrospectively analysed. The procedure, performed by the oromaxillofacial surgeon, involved securing a mandibular bone graft beneath the periosteum on the labial aspect of the canine tooth chosen to be harvested for the MOOKP procedure. This procedure was performed simultaneously with the Stage 1 A of the MOOKP. Three months later, the tooth was harvested and fashioned into the osteo-odonto alveolar lamina similar to the method described in the Rome-Vienna Protocol. The bone augmentation procedure was performed in 11 eyes (five SJS/ six chemical injuries). The mean follow-up after Stage 2 of MOOKP procedure in these eyes was 7.45 months (2 to 20 months). Complications noted were peripheral laminar exposure (three eyes-SJS) and bone graft exposure and necrosis in the mouth (nine-SJS). No evidence of clinical laminar resorption was noted in any of the eyes. Laminar resorption in MOOKP can lead to vision and globe threatening complications due to the consequent cylinder instability and chances of extrusion. Augmenting the bone on the labial aspect of the canine tooth might have a role to play in delaying or preventing laminar resorption.

  7. Effects of hydrogen addition and nitrogen dilution on the laminar flame characteristics of premixed methane-air flames

    Energy Technology Data Exchange (ETDEWEB)

    Tahtouh, T.; Halter, F.; Mounaim-Rousselle, C. [Institut PRISME, Universite d' Orleans, 8 rue Leonard de Vinci-45072, Orleans Cedex 2 (France); Samson, E. [PSA Peugeot Citroen (France)

    2009-10-15

    The effect of hydrogen addition and nitrogen dilution on laminar flame characteristics was investigated. The spherical expanding flame technique, in a constant volume bomb, was employed to extract laminar flame characteristics. The mole fraction of hydrogen in the methane-hydrogen mixture was varied from 0 to 1 and the mole fraction of nitrogen in the total mixture (methane-hydrogen-air-diluent) from 0 to 0.35. Measurements were performed at an initial pressure of 0.1 MPa and an initial temperature of 300 K. The mixtures investigated were under stoichiometric conditions. Based on experimental measurements, a new correlation for calculating the laminar burning velocity of methane-hydrogen-air-nitrogen mixtures is proposed. The laminar burning velocity was found to increase linearly with hydrogen mass fraction for all dilution ratios while the burned gas Markstein length decreases with the increase in hydrogen amount in the mixture except for high hydrogen mole fractions (>0.6). Nitrogen dilution has a nonlinear reducing effect on the laminar burning velocity and an increasing effect on the burned gas Markstein length. The experimental results and the proposed correlation obtained are in good agreement with literature values. (author)

  8. Unsteady separated stagnation-point flow and heat transfer of a viscous fluid over a moving flat surface

    Science.gov (United States)

    Dholey, S.

    2018-04-01

    In this paper, we have investigated numerically the laminar unsteady separated stagnation-point flow and heat transfer of a viscous fluid over a moving flat surface in the presence of a time dependent free stream velocity which causes the unsteadiness of this flow problem. The plate is assumed to move in the same or opposite direction of the free stream velocity. The flow is therefore governed by the velocity ratio parameter λ (ratio of the plate velocity to the free stream velocity) and the unsteadiness parameter β. When the plate surface moves in the same direction of the free stream velocity (i.e., when λ > 0), the solution of this flow problem continues for any given value of β. On the other hand, when they move in opposite directions (i.e., when λ heat transfer analysis is that for a given value of λ(= 0), first the heat transfer rate increases with the increase of the Prandtl number Pr and after attaining a maximum value, it decreases and finally tends to be zero for large values of Pr depending upon the values of β > 0. On the contrary, for a given value of β(≤ 0), the rate of heat transfer increases consistently with the increase of Pr.

  9. Wide angle isotope separator

    International Nuclear Information System (INIS)

    Kantrowitz, A.

    1976-01-01

    A method and apparatus is described for particle separation. The method uses a wide angle radially expanding vapor of a particle mixture. In particular, selective ionization of one isotope type in the particle mixture is produced in a multichamber separator and the ionized isotope type is accelerated out of the path of the vapor expansion for separate collection

  10. Steam-water separator

    International Nuclear Information System (INIS)

    Modrak, T.M.; Curtis, R.W.

    1978-01-01

    A two-stage steam-water separating device is introduced, where the second stage is made as a cyclone separator. The water separated here is collected in the first stage of the inner tube and is returned to the steam raising unit. (TK) [de

  11. Meniscus Membranes For Separation

    Science.gov (United States)

    Dye, Robert C.; Jorgensen, Betty; Pesiri, David R.

    2005-09-20

    Gas separation membranes, especially meniscus-shaped membranes for gas separations are disclosed together with the use of such meniscus-shaped membranes for applications such as thermal gas valves, pre-concentration of a gas stream, and selective pre-screening of a gas stream. In addition, a rapid screening system for simultaneously screening polymer materials for effectiveness in gas separation is provided.

  12. Meniscus membranes for separations

    Science.gov (United States)

    Dye, Robert C [Irvine, CA; Jorgensen, Betty [Jemez Springs, NM; Pesiri, David R [Aliso Viejo, CA

    2004-01-27

    Gas separation membranes, especially meniscus-shaped membranes for gas separations are disclosed together with the use of such meniscus-shaped membranes for applications such as thermal gas valves, pre-concentration of a gas stream, and selective pre-screening of a gas stream. In addition, a rapid screening system for simultaneously screening polymer materials for effectiveness in gas separation is provided.

  13. Method and apparatus for separating isotopes

    International Nuclear Information System (INIS)

    Harris, S.E.

    1976-01-01

    Isotope separation is achieved between species A and B having an absorption resonance separated by an isotopic shift by selectively exciting a portion of species A using a tunable photon source of narrow emission line with and subsequently causing collisions with an optically excited third species to selectively ionize the excited portion of species A. When ionized, species A is easily separated by any technique, using its ionized condition to distinguish it from species B. 18 claims, 3 drawing figures

  14. Laminar flow in porous pipes and ducts with variable suction or injection at the wall

    International Nuclear Information System (INIS)

    Souza Araujo, P.M. de; Stuckenbruck, S.

    1977-01-01

    The laminar flow of an incompressible fluid is analysed along a porous-walled straight circular tube and a flat duct formed by parallel porous plates. The non-similarity of velocity profiles is verified and the analytical solution is obtained by expanding the axial velocity component in a power series. The mass flow through the walls is taken into consideration as an application of Darcy's Law. Adverse axial pressure gradients and occasional reverse flow near the wall are pointed out in the work. (Author) [pt

  15. Analysis of thermal dispersion in an array of parallel plates with fully-developed laminar flow

    International Nuclear Information System (INIS)

    Xu Jiaying; Lu Tianjian; Hodson, Howard P.; Fleck, Norman A.

    2010-01-01

    The effect of thermal dispersion upon heat transfer across a periodic array of parallel plates is studied. Three basic heat transfer problems are addressed, each for steady, fully-developed, laminar fluid flow: (a) transient heat transfer due to an arbitrary initial temperature distribution within the fluid, (b) steady heat transfer with constant heat flux on all plate surfaces, and (c) steady heat transfer with constant wall temperatures. For problems (a) and (b), the effective thermal dispersivity scales with the Peclet number Pe according to 1 + CPe 2 , where the coefficient C is independent of Pe. For problem (c) the coefficient C is a function of Pe.

  16. Laminar burning velocities of near-flammability-limit H{sub 2}-air-steam mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Loesel Sitar, J V; Chan, C K; Torchia, F; Guerrero, A

    1996-12-31

    Laminar burning velocities of lean H{sub 2}-air-steam mixtures near the flammability limit were measured by using the pressure-time history of an expanding flame kernel. Although flames in these mixtures are inherently unstable, this difficulty was avoided by using the early pressure rise of the burn. A comparison of results from that method with burning velocities determined from schlieren photographs of the expanding flame kernel gave good agreement. Despite the difficulties, it is believed that the pressure trace method gives results that are useful in modelling reactor accident scenarios. 8 refs., 4 figs.

  17. Fully developed laminar flow of two immiscible liquids through horizontal pipes: a variational approach

    Energy Technology Data Exchange (ETDEWEB)

    Kurban, Adib Paulo Abdalla [PETROBRAS, Rio de Janeiro (Brazil). Centro de Pesquisas; Bannwart, Antonio Carlos [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica

    1990-12-31

    The fully developed laminar flow of two immiscible liquids with both different viscosities and densities through a horizontal round pipe is studied. The interface between the fluids as well as their flow fields are determined by the use of a variational principle: the so called viscous dissipation principle: The results foreseen by this paper are in agreement with the physical observation (e.g. Southern and Ballman) that the more viscous fluid is total or partially encapsulated by the less viscous one. (author) 8 refs., 4 figs.

  18. Calculation of pressure gradients from MR velocity data in a laminar flow model

    International Nuclear Information System (INIS)

    Adler, R.S.; Chenevert, T.L.; Fowlkes, J.B.; Pipe, J.G.; Rubin, J.M.

    1990-01-01

    This paper reports on the ability of current imaging modalities to provide velocity-distribution data that offers the possibility of noninvasive pressure-gradient determination from an appropriate rheologic model of flow. A simple laminar flow model is considered at low Reynolds number, RE calc = 0.59 + (1.13 x (dp/dz) meas ), R 2 = .994, in units of dyne/cm 2 /cm for the range of flows considered. The authors' results indicate the potential usefulness of noninvasive pressure-gradient determinations from quantitative analysis of imaging-derived velocity data

  19. Numerical analysis of a hypersonic turbulent and laminar flow using a commercial CFD solver

    Directory of Open Access Journals (Sweden)

    Pajčin Miroslav P.

    2017-01-01

    Full Text Available Computational fluid dynamics computations for two hypersonic flow cases using the commercial ANSYS FLUENT 16.2 CFD software were done. In this paper, an internal and external hypersonic flow cases were considered and analysis of the hypersonic flow using different turbulence viscosity models available in ANSYS FLUENT 16.2 as well as the laminar viscosity model were done. The obtained results were after compared and commented upon. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 35035

  20. Fully developed laminar flow of two immiscible liquids through horizontal pipes: a variational approach

    Energy Technology Data Exchange (ETDEWEB)

    Kurban, Adib Paulo Abdalla [PETROBRAS, Rio de Janeiro (Brazil). Centro de Pesquisas; Bannwart, Antonio Carlos [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica

    1991-12-31

    The fully developed laminar flow of two immiscible liquids with both different viscosities and densities through a horizontal round pipe is studied. The interface between the fluids as well as their flow fields are determined by the use of a variational principle: the so called viscous dissipation principle: The results foreseen by this paper are in agreement with the physical observation (e.g. Southern and Ballman) that the more viscous fluid is total or partially encapsulated by the less viscous one. (author) 8 refs., 4 figs.

  1. MRI demonstration of cortical laminar necrosis and delayed white matter injury in anoxic encephalopathy

    International Nuclear Information System (INIS)

    Sawada, H.; Udaka, F.; Seriu, N.; Shindou, K.; Kameyama, M.; Tsujimura, M.

    1990-01-01

    We performed serial radiological examinations on a patient with anoxic encephalopathy. In the early term after the anoxic insult, T1-weighted MRI revealed high signal intensity area distributed laminarly in the cerebral cortex and diffusely in the putamen, which were thought to refect the cortical necrosis and necrosis in the putamen. Single photon emission computed tomography using I-123 isopropylamphetamine showed persistent hypoperfusion in the arterial watershed zones. T2-weighted MRI performed several months after the anoxic episode revealed diffuse high-intensity lesions in the arterial watershed zones. These delayed-onset white matter lesions continued to extend over several months. (orig.)

  2. Conjugated heat transfer in laminar flow between parallel-plates channel

    International Nuclear Information System (INIS)

    Guedes, R.O.C.; Cotta, R.M.; Brum, N.C.L.

    1989-01-01

    An analysis is made of conjugated convective-conductive heat transfer in laminar flow of a newtonian fluid between parallel-plates channel, taking into account the longitudinal conduction along the duct walls only, by neglecting the transversal temperature gradients in the solid. This extended Graetz-type problem is then analytically handled through the generalized integral transform technique, providing accurate numerical results for quantities of practical interest sucyh as bulk and wall temperatures, and Nusselt numbers. The effects of a conjugation parameter and Biot number on heat transfer behavior are then investigated. (author)

  3. Laminar burning velocities of near-flammability-limit H2-air-steam mixtures

    International Nuclear Information System (INIS)

    Loesel Sitar, J.V.; Chan, C.K.; Torchia, F.; Guerrero, A.

    1995-01-01

    Laminar burning velocities of lean H 2 -air-steam mixtures near the flammability limit were measured by using the pressure-time history of an expanding flame kernel. Although flames in these mixtures are inherently unstable, this difficulty was avoided by using the early pressure rise of the burn. A comparison of results from that method with burning velocities determined from schlieren photographs of the expanding flame kernel gave good agreement. Despite the difficulties, it is believed that the pressure trace method gives results that are useful in modelling reactor accident scenarios. 8 refs., 4 figs

  4. Friction factors referring to laminar flow through pipe bundles with longitudinal webs

    Energy Technology Data Exchange (ETDEWEB)

    Schenkel, G

    1983-09-01

    Pipe bundles with continuous webs or ribs between adjacent pipes, as well as between outer pipes and channel walls, are much more vibrational proof than web-free systems. In addition, the change-over from a multiple-connected web-free cross-section to a set of singly-connected cross-sections facilitates the calculation of friction factors. The investigation is concerned with isothermal steady fully-developed laminar flow of Newtonian fluids. In particularly, pipe bundles with squares and hexagonal arrays in respective channels are treated. Friction factors for the subchannels are taken from a former paper of the author.

  5. Selective in situ functionalization of biosensors on LOC devices using laminar co-flow

    DEFF Research Database (Denmark)

    Parra-Cabrera, C.; Sporer, C.; Rodriguez-Villareal, I.

    2012-01-01

    Many applications involving lab-on-a-chip (LOC) devices are prevented from entering the market because of difficulties to achieve mass production and impart suitable properties allowing long-term storage. To integrate biosensors on these microfluidic chips, one of the main restrictions...... is the fabrication and stability of the molecular modifications that must be performed on the surfaces of the sensors for a given application. The complexity of the problem increases exponentially when the LOC integrates several of these sensors. Here we present a system based on laminar co-flow to perform an on...

  6. Bryozoan filter feeding in laminar wall layers: flume experiments and computer simulation

    DEFF Research Database (Denmark)

    Larsen, Poul Scheel; Matlok, Simon; Riisgård, Hans Ulrik

    1998-01-01

    gradient (1-4 s-1). The laminar wall layer simulated viscous sublayers found in the field for smooth surfaces. Incurrents to lines of 3-10 zooids typically distort paths of particles approaching the colony at heights 1-2 mm above the level of lophophore inlets and theycapture particles from paths 0...... line colony to be about 16 times the frontal area of a simulated lophophore. Fluid particles were captured from paths about 1.3 mm above the sink. At twice the flowrate, the area cleared of particles reduced to about 7 times the frontal area while feeding rate increased by about 19%.KEY WORDS: ambient...

  7. How the venetian blind percept emerges from the laminar cortical dynamics of 3D vision

    OpenAIRE

    Cao, Yongqiang; Grossberg, Stephen

    2014-01-01

    The 3D LAMINART model of 3D vision and figure-ground perception is used to explain and simulate a key example of the Venetian blind effect and to show how it is related to other well-known perceptual phenomena such as Panum's limiting case. The model proposes how lateral geniculate nucleus (LGN) and hierarchically organized laminar circuits in cortical areas V1, V2, and V4 interact to control processes of 3D boundary formation and surface filling-in that simulate many properties of 3D vision ...

  8. How the Venetian Blind Percept Emergesfrom the Laminar Cortical Dynamics of 3D Vision

    OpenAIRE

    Stephen eGrossberg

    2014-01-01

    The 3D LAMINART model of 3D vision and figure-ground perception is used to explain and simulate a key example of the Venetian blind effect and show how it is related to other well-known perceptual phenomena such as Panum's limiting case. The model shows how identified neurons that interact in hierarchically organized laminar circuits of the visual cortex can simulate many properties of 3D vision percepts, notably consciously seen surface percepts, which are predicted to arise when filled-in s...

  9. 9 CFR 3.109 - Separation.

    Science.gov (United States)

    2010-01-01

    ... Mammals Animal Health and Husbandry Standards § 3.109 Separation. Marine mammals, whenever known to be... in the same enclosure. Marine mammals must not be housed near other animals that cause them... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Separation. 3.109 Section 3.109...

  10. PARAFFIN SEPARATION VACUUM DISTILLATION

    Directory of Open Access Journals (Sweden)

    Zaid A. Abdulrahman

    2013-05-01

    Full Text Available Simulated column performance curves were constructed for existing paraffin separation vacuum distillation column in LAB plant (Arab Detergent Company/Baiji-Iraq. The variables considered in this study are the thermodynamic model option, top vacuum pressure, top and bottom temperatures, feed temperature, feed composition & reflux ratio. Also simulated columns profiles for the temperature, vapor & liquid flow rates composition were constructed. Four different thermodynamic model options (SRK, TSRK, PR, and ESSO were used, affecting the results within 1-25% variation for the most cases.The simulated results show that about 2% to 8 % of paraffin (C10, C11, C12, & C13 present at the bottom stream which may cause a problem in the LAB plant. The major variations were noticed for the top temperature & the  paraffin weight fractions at bottom section with top vacuum pressure. The bottom temperature above 240 oC is not recommended because the total bottom flow rate decreases sharply, where as  the weight fraction of paraffins decrease slightly. The study gives evidence about a successful simulation with CHEMCAD

  11. Safety shutdown separators

    Science.gov (United States)

    Carlson, Steven Allen; Anakor, Ifenna Kingsley; Farrell, Greg Robert

    2015-06-30

    The present invention pertains to electrochemical cells which comprise (a) an anode; (b) a cathode; (c) a solid porous separator, such as a polyolefin, xerogel, or inorganic oxide separator; and (d) a nonaqueous electrolyte, wherein the separator comprises a porous membrane having a microporous coating comprising polymer particles which have not coalesced to form a continuous film. This microporous coating on the separator acts as a safety shutdown layer that rapidly increases the internal resistivity and shuts the cell down upon heating to an elevated temperature, such as 110.degree. C. Also provided are methods for increasing the safety of an electrochemical cell by utilizing such separators with a safety shutdown layer.

  12. Rapid chemical separations

    CERN Document Server

    Trautmann, N

    1976-01-01

    A survey is given on the progress of fast chemical separation procedures during the last few years. Fast, discontinuous separation techniques are illustrated by a procedure for niobium. The use of such techniques for the chemical characterization of the heaviest known elements is described. Other rapid separation methods from aqueous solutions are summarized. The application of the high speed liquid chromatography to the separation of chemically similar elements is outlined. The use of the gas jet recoil transport method for nuclear reaction products and its combination with a continuous solvent extraction technique and with a thermochromatographic separation is presented. Different separation methods in the gas phase are briefly discussed and the attachment of a thermochromatographic technique to an on-line mass separator is shown. (45 refs).

  13. Acoustofluidic bacteria separation

    International Nuclear Information System (INIS)

    Li, Sixing; Huang, Tony Jun; Ma, Fen; Zeng, Xiangqun; Bachman, Hunter; Cameron, Craig E

    2017-01-01

    Bacterial separation from human blood samples can help with the identification of pathogenic bacteria for sepsis diagnosis. In this work, we report an acoustofluidic device for label-free bacterial separation from human blood samples. In particular, we exploit the acoustic radiation force generated from a tilted-angle standing surface acoustic wave (taSSAW) field to separate Escherichia coli from human blood cells based on their size difference. Flow cytometry analysis of the E. coli separated from red blood cells shows a purity of more than 96%. Moreover, the label-free electrochemical detection of the separated E. coli displays reduced non-specific signals due to the removal of blood cells. Our acoustofluidic bacterial separation platform has advantages such as label-free separation, high biocompatibility, flexibility, low cost, miniaturization, automation, and ease of in-line integration. The platform can be incorporated with an on-chip sensor to realize a point-of-care sepsis diagnostic device. (paper)

  14. Acoustofluidic bacteria separation

    Science.gov (United States)

    Li, Sixing; Ma, Fen; Bachman, Hunter; Cameron, Craig E.; Zeng, Xiangqun; Huang, Tony Jun

    2017-01-01

    Bacterial separation from human blood samples can help with the identification of pathogenic bacteria for sepsis diagnosis. In this work, we report an acoustofluidic device for label-free bacterial separation from human blood samples. In particular, we exploit the acoustic radiation force generated from a tilted-angle standing surface acoustic wave (taSSAW) field to separate Escherichia coli from human blood cells based on their size difference. Flow cytometry analysis of the E. coli separated from red blood cells shows a purity of more than 96%. Moreover, the label-free electrochemical detection of the separated E. coli displays reduced non-specific signals due to the removal of blood cells. Our acoustofluidic bacterial separation platform has advantages such as label-free separation, high biocompatibility, flexibility, low cost, miniaturization, automation, and ease of in-line integration. The platform can be incorporated with an on-chip sensor to realize a point-of-care sepsis diagnostic device.

  15. MR microscopy of articular cartilage at 1.5 T: orientation and site dependence of laminar structures

    Energy Technology Data Exchange (ETDEWEB)

    Yoshioka, Hiroshi; Anno, Izumi; Echigo, Junko; Itai, Yuji [Department of Radiology, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575 (Japan); Haishi, Tomoyuki; Uematsu, Takaaki; Matsuda, Yoshimasa; Kose, Katsumi [Institute of Applied Physics, University of Tsukuba, Tsukuba (Japan); Lang, Philipp [Department of Radiology, Brigham and Women' s Hospital, Boston, Massachusetts (United States)

    2002-09-01

    Abstract Objective. To evaluate MR microscopic images of normal-appearing porcine hyaline cartilage (n=15) in vitro obtained with an MR microscope using an independent console system (MRMICS) at 1.5 T.Design and results. The MRMICS is a portable imaging system consisting of a radiofrequency system, gradient power supplies and a personal computer. The images from the MRMICS showed a laminar structure of porcine cartilage similar to the structure demonstrated with other MR imaging techniques. The laminar structures of the articular cartilage, were, however heterogeneous in respect of signal intensity and thickness, which varied according to the site resected. The MR laminar appearance was most comparable to the staining with Masson's trichrome for collagen.Conclusion. MRMICS is a useful add-on system for obtaining microscopic MR images of articular cartilage in vitro. (orig.)

  16. MR microscopy of articular cartilage at 1.5 T: orientation and site dependence of laminar structures

    International Nuclear Information System (INIS)

    Yoshioka, Hiroshi; Anno, Izumi; Echigo, Junko; Itai, Yuji; Haishi, Tomoyuki; Uematsu, Takaaki; Matsuda, Yoshimasa; Kose, Katsumi; Lang, Philipp

    2002-01-01

    Abstract Objective. To evaluate MR microscopic images of normal-appearing porcine hyaline cartilage (n=15) in vitro obtained with an MR microscope using an independent console system (MRMICS) at 1.5 T.Design and results. The MRMICS is a portable imaging system consisting of a radiofrequency system, gradient power supplies and a personal computer. The images from the MRMICS showed a laminar structure of porcine cartilage similar to the structure demonstrated with other MR imaging techniques. The laminar structures of the articular cartilage, were, however heterogeneous in respect of signal intensity and thickness, which varied according to the site resected. The MR laminar appearance was most comparable to the staining with Masson's trichrome for collagen.Conclusion. MRMICS is a useful add-on system for obtaining microscopic MR images of articular cartilage in vitro. (orig.)

  17. Laminar Flame Speeds of Gasoline Surrogates Measured with the Flat Flame Method

    KAUST Repository

    Liao, Y.-H.

    2016-01-27

    © 2016 American Chemical Society. The adiabatic, laminar flame speeds of gasoline surrogates at atmospheric pressure over a range of equivalence ratios of = 0.8-1.3 and unburned gas temperatures of 298-400 K are measured with the flat flame method, which produces a one-dimensional flat flame free of stretch. Surrogates used in the current work are the primary reference fuels (PRFs, mixtures of n-heptane and isooctane), the toluene reference fuels (TRFs, mixtures of toluene and PRFs), and the ethanol reference fuels (ERFs, mixtures of ethanol and PRFs). In general, there is good agreement between the present work and the literature data for single-component fuel and PRF mixtures. Surrogates of TRF mixtures are found to exhibit comparable flame speeds to a real gasoline, while there is discrepancy observed between isooctane and gasoline. Moreover, the laminar flame speeds of TRF mixtures with similar fractions of n-heptane are found to be insensitive to the quantity of toluene in the mixture. Mixtures of ERFs exhibit comparable flame speeds to those of TRFs with similar mole fractions of n-heptane and isooctane.

  18. Osborne Reynolds pipe flow: direct numerical simulation from laminar to fully-developed turbulence

    Science.gov (United States)

    Adrian, R. J.; Wu, X.; Moin, P.; Baltzer, J. R.

    2014-11-01

    Osborne Reynolds' pipe experiment marked the onset of modern viscous flow research, yet the detailed mechanism carrying the laminar state to fully-developed turbulence has been quite elusive, despite notable progress related to dynamic edge-state theory. Here, we continue our direct numerical simulation study on this problem using a 250R long, spatially-developing pipe configuration with various Reynolds numbers, inflow disturbances, and inlet base flow states. For the inlet base flow, both fully-developed laminar profile and the uniform plug profile are considered. Inlet disturbances consist of rings of turbulence of different width and radial location. In all the six cases examined so far, energy norms show exponential growth with axial distance until transition after an initial decay near the inlet. Skin-friction overshoots the Moody's correlation in most, but not all, the cases. Another common theme is that lambda vortices amplified out of susceptible elements in the inlet disturbances trigger rapidly growing hairpin packets at random locations and times, after which infant turbulent spots appear. Mature turbulent spots in the pipe transition are actually tight concentrations of hairpin packets looking like a hairpin forest. The plug flow inlet profile requires much stronger disturbances to transition than the parabolic profile.

  19. Hydrodynamics of piston-driven laminar pulsating flow: Part 2. Fully developed flow

    International Nuclear Information System (INIS)

    Aygun, Cemalettin; Aydin, Orhan

    2014-01-01

    Highlights: • The piston-driven laminar pulsating flow in a pipe is studied. • Fully developed flow is examined analytically, numerically and experimentally. • An increase in F results an increase in the amplitude of the centerline velocity. • The characters of the radial velocity profiles critically depend on both the frequency and the phase angle. • The near/off-wall flow reversals are observed for F = 105, 226 and 402. - Abstract: Piston-driven pulsating flow is a specific type of pressure-driven pulsating flows. In this study, piston-driven laminar pulsating flow in a pipe is studied. This study mainly exists of two parts: developing flow and fully developed flow. In this part, hydrodynamically fully developed flow is examined analytically, numerically and experimentally. A constant value of the time-averaged Reynolds number is considered, Re = 1000. In the theoretical studies, both analytical and numerical, an inlet velocity profile representing the experimental case, i.e., the piston driven flow, is assumed. In the experiments, in the hydrodynamically fully developed region, radial velocity distribution and pressure drop are obtained using hot-wire anemometer and pressure transmitter, respectively. The effect pulsation frequency on the friction coefficient as well as velocity profiles are obtained. A good agreement is observed among analytical, numerical and experimental results

  20. In situ analysis of dynamic laminar flow extraction using surface-enhanced Raman spectroscopy

    Science.gov (United States)

    Wang, Fei; Wang, Hua-Lin; Qiu, Yang; Chang, Yu-Long; Long, Yi-Tao

    2015-12-01

    In this study, we performed micro-scale dynamic laminar flow extraction and site-specific in situ chloride concentration measurements. Surface-enhanced Raman spectroscopy was utilized to investigate the diffusion process of chloride ions from an oil phase to a water phase under laminar flow. In contrast to common logic, we used SERS intensity gradients of Rhodamine 6G to quantitatively calculate the concentration of chloride ions at specific positions on a microfluidic chip. By varying the fluid flow rates, we achieved different extraction times and therefore different chloride concentrations at specific positions along the microchannel. SERS spectra from the water phase were recorded at these different positions, and the spatial distribution of the SERS signals was used to map the degree of nanoparticle aggregation. The concentration of chloride ions in the channel could therefore be obtained. We conclude that this method can be used to explore the extraction behaviour and efficiency of some ions or molecules that enhance the SERS intensity in water or oil by inducing nanoparticle aggregation.

  1. Calculation of laminar incompressible fluid flow and heat transfer during spherical annulus filling

    International Nuclear Information System (INIS)

    Tuft, D.B.

    1979-04-01

    A method of computing laminar incompressible fluid-flow and heat transfer during the filling of a spherical annulus is presented. Transient fluid temperatures and heat flux rates in the spherical annulus are calculated for an insulated outer sphere and a constant temperature inner sphere with heated water filling the annulus from the bottom. To achieve a solution, laminar axially symmetric flow is assumed and the Marker-and-Cell (MAC) free surface computational method is applied to this problem in spherical coordinates. Changes in the standard MAC treatment are incorporated and special methods for handling the free surface are introduced. A variable mesh is used to improve resolution near the inner sphere where temperature and velocity gradients are steep and the governing equations are derived for variable fluid properties to allow an eddy viscosity turbulence model to be applied later. Calculations of velocity, temperature, and inner sphere heat flux in a spherical annulus of 139.7 mm inner radius, and 168.3 mm outer radius within an inlet tube diameter of 38.1 mm are presented

  2. Effects of Burner Configurations on the Natural Oscillation Characteristics of Laminar Jet Diffusion Flames

    Directory of Open Access Journals (Sweden)

    K. R. V. Manikantachari

    2015-09-01

    Full Text Available In this work, effects of burner configurations on the natural oscillations of methane laminar diffusion flames under atmospheric pressure and normal gravity conditions have been studied experimentally. Three regimes of laminar diffusion flames, namely, steady, intermittent flickering and continuous flickering have been investigated. Burner configurations such as straight pipe, contoured nozzle and that having an orifice plate at the exit have been considered. All burners have the same area of cross section at the exit and same burner lip thickness. Flame height data has been extracted from direct flame video using MATLAB. Shadowgraph videos have been captured to analyze the plume width characteristics. Results show that, the oscillation characteristics of the orifice burner is significantly different from the other two burners; orifice burner produces a shorter flame and wider thermal plume width in the steady flame regime and the onset of the oscillation/flickering regimes for the orifice burner occurs at a higher fuel flow rate. In the natural flickering regime, the dominating frequency of flame flickering remains within a small range, 12.5 Hz to 15 Hz, for all the burners and for all fuel flow rates. The time-averaged flame length-scale parameters, such as the maximum and the minimum flame heights, increase with respect to the fuel flow rate, however, the difference in the maximum and the minimum flame heights remains almost constant.

  3. Coupling of conduction with laminar free convection from a vertical flat plate - an experimental study

    International Nuclear Information System (INIS)

    Aharon, J.; Lahav, C.; Kalman, H.; Shai, I.

    1996-01-01

    The present work deals with natural convection on a vertical flat plate, where one side of the plate is maintained at a uniform temperature - T a , and the other side of the plate is exposed to an environment of constant temperature -T∞. The plate is consisted of several layers of conductive and non-conductive materials such that the series thermal resistance can be expressed as an equivalent heat transfer coefficient h eq 1/Σ(k i /d i ). It is also assumed a negligible axial conduction, which can be neglected. The present investigation treats the heat transfer problem in the laminar zone in air (P r ∼1). The wall effective heat transfer coefficient is in the range of 4.3 to 11.5 W/m 2 - deg C. An experimental apparatus was constructed to confirm the heat transfer features predicted analytically in a previous work. The local experimental Nusselt number was correlated with the modified Rayleigh number, for the laminar range (authors)

  4. A Laminar Flow-Based Microfluidic Tesla Pump via Lithography Enabled 3D Printing.

    Science.gov (United States)

    Habhab, Mohammed-Baker; Ismail, Tania; Lo, Joe Fujiou

    2016-11-23

    Tesla turbine and its applications in power generation and fluid flow were demonstrated by Nicholas Tesla in 1913. However, its real-world implementations were limited by the difficulty to maintain laminar flow between rotor disks, transient efficiencies during rotor acceleration, and the lack of other applications that fully utilize the continuous flow outputs. All of the aforementioned limits of Tesla turbines can be addressed by scaling to the microfluidic flow regime. Demonstrated here is a microscale Tesla pump designed and fabricated using a Digital Light Processing (DLP) based 3D printer with 43 µm lateral and 30 µm thickness resolutions. The miniaturized pump is characterized by low Reynolds number of 1000 and a flow rate of up to 12.6 mL/min at 1200 rpm, unloaded. It is capable of driving a mixer network to generate microfluidic gradient. The continuous, laminar flow from Tesla turbines is well-suited to the needs of flow-sensitive microfluidics, where the integrated pump will enable numerous compact lab-on-a-chip applications.

  5. Subchannel friction factors for rod bundles: laminar flow predictions and their application to turbulent flows

    International Nuclear Information System (INIS)

    Robinson, D.P.

    1979-02-01

    For the calculation of friction factors the use of correlations validated for smooth circular tubes along with the duct hydraulic diameter is known to be inappropriate for certain non-circular geometries. In order to test the validity and range of application of such correlations to the subchannels of rod bundles a computer programme has been written for the prediction of subchannel laminar velocity distributions and friction coefficients for fully developed flow. The theoretical basis and development of the programme is described along with comparisons between predictions and existing solutions for some simple geometries. Using the computer programme a wide range of calculations have been carried out for flow sections representing edge, corner and internal subchannels of rod bundles with particular emphasis on those of in-line pin bundle geometries. Where comparison can be made the predicted laminar coefficients are in excellent agreement with existing solutions. Although the approach adopted here could be used as the basis of a model for the subchannel axial friction factor, careful account should be taken of enhanced turbulent momentum transfer in situations where the flow is not unidirectional. (UK)

  6. A Laminar Flow-Based Microfluidic Tesla Pump via Lithography Enabled 3D Printing

    Directory of Open Access Journals (Sweden)

    Mohammed-Baker Habhab

    2016-11-01

    Full Text Available Tesla turbine and its applications in power generation and fluid flow were demonstrated by Nicholas Tesla in 1913. However, its real-world implementations were limited by the difficulty to maintain laminar flow between rotor disks, transient efficiencies during rotor acceleration, and the lack of other applications that fully utilize the continuous flow outputs. All of the aforementioned limits of Tesla turbines can be addressed by scaling to the microfluidic flow regime. Demonstrated here is a microscale Tesla pump designed and fabricated using a Digital Light Processing (DLP based 3D printer with 43 µm lateral and 30 µm thickness resolutions. The miniaturized pump is characterized by low Reynolds number of 1000 and a flow rate of up to 12.6 mL/min at 1200 rpm, unloaded. It is capable of driving a mixer network to generate microfluidic gradient. The continuous, laminar flow from Tesla turbines is well-suited to the needs of flow-sensitive microfluidics, where the integrated pump will enable numerous compact lab-on-a-chip applications.

  7. Buoyancy effects laminar slot jet impinging on a surface with constant heat flux

    International Nuclear Information System (INIS)

    Shokouhmand, H.; Esfahanian, V.; Masoodi, R.

    2004-01-01

    The two-dimensional laminar air jet issuing from a nozzle of half which terminates at height above a flat plate normal to the jet is numerically on the flow and thermal structure of the region near impingement. The impinging surface is maintained at a constant heat flux condition. The full Navier-Stocks and energy equations are solved by a finite difference method to evaluate the velocity profiles and temperature distribution. The governing parameters and their ranges are: Reynolds number Re, 10-50, Grashof number Gr, 0-50, Richardson number Ri=Gr/ Re 2 , Non dimensional nozzle height H,2-3. Results of the free streamline, local friction factor and heat transfer coefficient are graphically presented. It is found that enhancement of the heat transfer rate is substantial for high Richardson number conditions. Although the laminar jet impingement for isothermal condition has been already studied, however the constant heat flux has not been studied enough. the present paper will analyze a low velocity air jet, Which can be used for cooling of a simulated electronics package

  8. Dynamic bioprocessing and microfluidic transport control with smart magnetic nanoparticles in laminar-flow devices.

    Science.gov (United States)

    Lai, James J; Nelson, Kjell E; Nash, Michael A; Hoffman, Allan S; Yager, Paul; Stayton, Patrick S

    2009-07-21

    In the absence of applied forces, the transport of molecules and particulate reagents across laminar flowstreams in microfluidic devices is dominated by the diffusivities of the transported species. While the differential diffusional properties between smaller and larger diagnostic targets and reagents have been exploited for bioseparation and assay applications, there are limitations to methods that depend on these intrinsic size differences. Here a new strategy is described for exploiting the sharply reversible change in size and magnetophoretic mobility of "smart" magnetic nanoparticles (mNPs) to perform bioseparation and target isolation under continuous flow processing conditions. The isolated 5 nm mNPs do not exhibit significant magnetophoretic velocities, but do exhibit high magnetophoretic velocities when aggregated by the action of a pH-responsive polymer coating. A simple external magnet is used to magnetophorese the aggregated mNPs that have captured a diagnostic target from a lower pH laminar flowstream (pH 7.3) to a second higher pH flowstream (pH 8.4) that induces rapid mNP disaggregation. In this second dis-aggregated state and flowstream, the mNPs continue to flow past the magnet rather than being immobilized at the channel surface near the magnet. This stimuli-responsive reagent system has been shown to transfer 81% of a model protein target from an input flowstream to a second flowstream in a continuous flow H-filter device.

  9. Characteristics of autoignited laminar lifted flames in heated coflow jets of carbon monoxide/hydrogen mixtures

    KAUST Repository

    Choi, Byungchul

    2012-06-01

    The characteristics of autoignited lifted flames in laminar jets of carbon monoxide/hydrogen fuels have been investigated experimentally in heated coflow air. In result, as the jet velocity increased, the blowoff was directly occurred from the nozzle-attached flame without experiencing a stabilized lifted flame, in the non-autoignited regime. In the autoignited regime, the autoignited lifted flame of carbon monoxide diluted by nitrogen was affected by the water vapor content in the compressed air oxidizer, as evidenced by the variation of the ignition delay time estimated by numerical calculation. In particular, in the autoignition regime at low temperatures with added hydrogen, the liftoff height of the autoignited lifted flames decreased and then increased as the jet velocity increased. Based on the mechanism in which the autoignited laminar lifted flame is stabilized by ignition delay time, the liftoff height can be influenced not only by the heat loss, but also by the preferential diffusion between momentum and mass diffusion in fuel jets during the autoignition process. © 2012 The Korean Society of Mechanical Engineers.

  10. Surgical clothing systems in laminar airflow operating room: a numerical assessment.

    Science.gov (United States)

    Sadrizadeh, Sasan; Holmberg, Sture

    2014-01-01

    This study compared two different laminar airflow distribution strategies - horizontal and vertical - and investigated the effectiveness of both ventilation systems in terms of reducing the sedimentation and distribution of bacteria-carrying particles. Three different staff clothing systems, which resulted in source strengths of 1.5, 4 and 5 CFU/s per person, were considered. The exploration was conducted numerically using a computational fluid dynamics technique. Active and passive air sampling methods were simulated in addition to recovery tests, and the results were compared. Model validation was performed through comparisons with measurement data from the published literature. The recovery test yielded a value of 8.1 min for the horizontal ventilation scenario and 11.9 min for the vertical ventilation system. Fewer particles were captured by the slit sampler and in sedimentation areas with the horizontal ventilation system. The simulated results revealed that under identical conditions in the examined operating room, the horizontal laminar ventilation system performed better than the vertical option. The internal constellation of lamps, the surgical team and objects could have a serious effect on the movement of infectious particles and therefore on postoperative surgical site infections. Copyright © 2014 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

  11. Uncertainty quantification-based robust aerodynamic optimization of laminar flow nacelle

    Science.gov (United States)

    Xiong, Neng; Tao, Yang; Liu, Zhiyong; Lin, Jun

    2018-05-01

    The aerodynamic performance of laminar flow nacelle is highly sensitive to uncertain working conditions, especially the surface roughness. An efficient robust aerodynamic optimization method on the basis of non-deterministic computational fluid dynamic (CFD) simulation and Efficient Global Optimization (EGO)algorithm was employed. A non-intrusive polynomial chaos method is used in conjunction with an existing well-verified CFD module to quantify the uncertainty propagation in the flow field. This paper investigates the roughness modeling behavior with the γ-Ret shear stress transport model including modeling flow transition and surface roughness effects. The roughness effects are modeled to simulate sand grain roughness. A Class-Shape Transformation-based parametrical description of the nacelle contour as part of an automatic design evaluation process is presented. A Design-of-Experiments (DoE) was performed and surrogate model by Kriging method was built. The new design nacelle process demonstrates that significant improvements of both mean and variance of the efficiency are achieved and the proposed method can be applied to laminar flow nacelle design successfully.

  12. Numerical and Experimental Investigation of Computed Tomography of Chemiluminescence for Hydrogen-Air Premixed Laminar Flames

    Directory of Open Access Journals (Sweden)

    Liang Lv

    2016-01-01

    Full Text Available Computed tomography of chemiluminescence (CTC is a promising technique for combustion diagnostics, providing instantaneous 3D information of flame structures, especially in harsh circumstance. This work focuses on assessing the feasibility of CTC and investigating structures of hydrogen-air premixed laminar flames using CTC. A numerical phantom study was performed to assess the accuracy of the reconstruction algorithm. A well-designed burner was used to generate stable hydrogen-air premixed laminar flames. The OH⁎ chemiluminescence intensity field reconstructed from 37 views using CTC was compared to the OH⁎ chemiluminescence distributions recorded directly by a single ICCD camera from the side view. The flame structures in different flow velocities and equivalence ratios were analyzed using the reconstructions. The results show that the CTC technique can effectively indicate real distributions of the flame chemiluminescence. The height of the flame becomes larger with increasing flow velocities, whereas it decreases with increasing equivalence ratios (no larger than 1. The increasing flow velocities gradually lift the flame reaction zones. A critical cone angle of 4.76 degrees is obtained to avoid blow-off. These results set up a foundation for next studies and the methods can be further developed to reconstruct 3D structures of flames.

  13. Linear Stability Analysis of Laminar Premixed Fuel-Rich Double-Spray Flames

    Directory of Open Access Journals (Sweden)

    Noam Weinberg

    2014-03-01

    Full Text Available This paper considers the stability of a double-spray premixed flame formed when both fuel and oxidizer are initially present in the form of sprays of evaporating liquid droplets. To simplify the inherent complexity that characterizes the analytic solution of multi-phase combustion processes, the analysis is restricted to fuel-rich laminar premixed double-spray flames, and assumes a single-step global chemical reaction mechanism. Steady-state solutions are obtained and the sensitivity of the flame temperature and the flame propagating velocity to the initial liquid fuel and/or oxidizer loads are established. The stability analysis revealed an increased proneness to cellular instability induced by the presence of the two sprays, and for the fuel-rich case considered here the influence of the liquid oxidizer was found to be more pronounced than that of the liquid fuel. Similar effects were noted for the neutral pulsating stability boundaries. The impact of unequal latent heats of vaporization is also investigated and found to be in keeping with the destabilizing influence of heat loss due to droplet evaporation. It should be noted that as far as the authors are aware no experimental evidence is available for (at least validation of the predictions. However, they do concur in a general and reasonable fashion with independent experimental evidence in the literature of the behavior of single fuel spray laminar premixed flames.

  14. Effect of mobile laminar airflow units on airborne bacterial contamination during neurosurgical procedures.

    Science.gov (United States)

    von Vogelsang, A-C; Förander, P; Arvidsson, M; Löwenhielm, P

    2018-03-24

    Surgical site infections (SSIs) after neurosurgery are potentially life-threatening and entail great costs. SSIs may occur from airborne bacteria in the operating room, and ultraclean air is desired during infection-prone cleaning procedures. Door openings and the number of persons present in the operating room affect the air quality. Mobile laminar airflow (MLAF) units, with horizontal laminar airflow, have previously been shown to reduce airborne bacterial contamination. To assess the effect of MLAF units on airborne bacterial contamination during neurosurgical procedures. In a quasi-experimental design, bacteria-carrying particles (colony-forming units: cfu) during neurosurgical procedures were measured with active air-sampling in operating rooms with conventional turbulent ventilation, and with additional MLAF units. The MLAF units were shifted between operating rooms monthly. Colony-forming unit count and bacterial species detection were conducted after incubation. Data was collected for a period of 18 months. A total of 233 samples were collected during 45 neurosurgical procedures. The use of MLAF units significantly reduced the numbers of cfu in the surgical site area (P neurosurgery to ultraclean air levels. MLAF units are valuable when the main operating room ventilation system is unable to produce ultraclean air in infection-prone clean neurosurgery. Copyright © 2018 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

  15. Coupling of conduction with laminar free convection from a vertical flat plate - an experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Aharon, J; Lahav, C [Israel Atomic Energy Commission, Beersheba (Israel). Nuclear Research Center-Negev; Kalman, H; Shai, I [Ben-Gurion Univ. of the Negev, Beersheba (Israel) Dept, of Mechanical engineering, Pearlstone Center for Aeronautical Engineering Studies

    1996-12-01

    The present work deals with natural convection on a vertical flat plate, where one side of the plate is maintained at a uniform temperature - T{sub a}, and the other side of the plate is exposed to an environment of constant temperature -T{infinity}. The plate is consisted of several layers of conductive and non-conductive materials such that the series thermal resistance can be expressed as an equivalent heat transfer coefficient h{sub eq} 1/{Sigma}(k{sub i}/d{sub i}). It is also assumed a negligible axial conduction, which can be neglected. The present investigation treats the heat transfer problem in the laminar zone in air (P{sub r}{approx}1). The wall effective heat transfer coefficient is in the range of 4.3 to 11.5 W/m{sup 2} - deg C. An experimental apparatus was constructed to confirm the heat transfer features predicted analytically in a previous work. The local experimental Nusselt number was correlated with the modified Rayleigh number, for the laminar range (authors).

  16. Numerical investigation of Al2O3/water nanofluid laminar convective heat transfer through triangular ducts

    Directory of Open Access Journals (Sweden)

    Zeinali Heris Saeed

    2011-01-01

    Full Text Available Abstract In this article, laminar flow-forced convective heat transfer of Al2O3/water nanofluid in a triangular duct under constant wall temperature condition is investigated numerically. In this investigation, the effects of parameters, such as nanoparticles diameter, concentration, and Reynolds number on the enhancement of nanofluids heat transfer is studied. Besides, the comparison between nanofluid and pure fluid heat transfer is achieved in this article. Sometimes, because of pressure drop limitations, the need for non-circular ducts arises in many heat transfer applications. The low heat transfer rate of non-circular ducts is one the limitations of these systems, and utilization of nanofluid instead of pure fluid because of its potential to increase heat transfer of system can compensate this problem. In this article, for considering the presence of nanoparticl: es, the dispersion model is used. Numerical results represent an enhancement of heat transfer of fluid associated with changing to the suspension of nanometer-sized particles in the triangular duct. The results of the present model indicate that the nanofluid Nusselt number increases with increasing concentration of nanoparticles and decreasing diameter. Also, the enhancement of the fluid heat transfer becomes better at high Re in laminar flow with the addition of nanoparticles.

  17. DNS of Laminar-Turbulent Transition in Swept-Wing Boundary Layers

    Science.gov (United States)

    Duan, L.; Choudhari, M.; Li, F.

    2014-01-01

    Direct numerical simulation (DNS) is performed to examine laminar to turbulent transition due to high-frequency secondary instability of stationary crossflow vortices in a subsonic swept-wing boundary layer for a realistic natural-laminar-flow airfoil configuration. The secondary instability is introduced via inflow forcing and the mode selected for forcing corresponds to the most amplified secondary instability mode that, in this case, derives a majority of its growth from energy production mechanisms associated with the wall-normal shear of the stationary basic state. An inlet boundary condition is carefully designed to allow for accurate injection of instability wave modes and minimize acoustic reflections at numerical boundaries. Nonlinear parabolized stability equation (PSE) predictions compare well with the DNS in terms of modal amplitudes and modal shape during the strongly nonlinear phase of the secondary instability mode. During the transition process, the skin friction coefficient rises rather rapidly and the wall-shear distribution shows a sawtooth pattern that is analogous to the previously documented surface flow visualizations of transition due to stationary crossflow instability. Fully turbulent features are observed in the downstream region of the flow.

  18. Laser-Doppler measurements of laminar and turbulent flow in a pipe bend

    Energy Technology Data Exchange (ETDEWEB)

    Enayet, M.M.; Gibson, M.M.; Taylor, A.M.K.P.; Yianneskis, M.

    1982-12-01

    Laser-Doppler measurements are reported for laminar and turbulent flow through a 90/sup 0/ bend of circular cross-section with mean radius of curvature equal to 2.8 times the diameter. The measurements were made in cross-stream planes 0.58 diameters upstream of the bend inlet plane, in 30, 60, and 75/sup 0/ planes in the bend and in planes one and six diameters downstream of the exit plane. Three sets of data were obtained: for laminar flow at Reynolds numbers of 500 and 1093 and for turbulent flow at the maximum obtainable Reynolds number of 43 000. The results show the development of strong pressure-driven secondary flows in the form of a pair of counter-rotating vortices in the streamwise direction. The strength and character of the secondary flows were found to depend on the thickness and nature of the inlet boundary layerd, conditions which could not be varied independently of Reynolds number. The quantitative anemometer measurements are supported by flow visualization studies. Refractive index matching at the fluid-wall interface was not used; the measurements consist, therefore, of streamwise components of mean and fluctuating velocities only, supplemented by wall pressure measurements for the turbulent flow. This displacement of the laser measurement volume due to refraction is allowed for in simple geometrical calculations. The results are intended for use as benchmark data for calibrating flow calculation methods.

  19. Suppression of endothelial t-PA expression by prolonged high laminar shear stress

    International Nuclear Information System (INIS)

    Ulfhammer, Erik; Carlstroem, Maria; Bergh, Niklas; Larsson, Pia; Karlsson, Lena; Jern, Sverker

    2009-01-01

    Primary hypertension is associated with an impaired capacity for acute release of endothelial tissue-type plasminogen activator (t-PA), which is an important local protective response to prevent thrombus extension. As hypertensive vascular remodeling potentially results in increased vascular wall shear stress, we investigated the impact of shear on regulation of t-PA. Cultured human endothelial cells were exposed to low (≤1.5 dyn/cm 2 ) or high (25 dyn/cm 2 ) laminar shear stress for up to 48 h in two different experimental models. Using real-time RT-PCR and ELISA, shear stress was observed to time and magnitude-dependently suppress t-PA transcript and protein secretion to approximately 30% of basal levels. Mechanistic experiments revealed reduced nuclear protein binding to the t-PA specific CRE element (EMSA) and an almost completely abrogated shear response with pharmacologic JNK inhibition. We conclude that prolonged high laminar shear stress suppresses endothelial t-PA expression and may therefore contribute to the enhanced risk of arterial thrombosis in hypertensive disease.

  20. Propagation of atmospheric pressure helium plasma jet into ambient air at laminar gas flow

    International Nuclear Information System (INIS)

    Pinchuk, M; Kurakina, N; Spodobin, V; Stepanova, O

    2017-01-01

    The formation of an atmospheric pressure plasma jet (APPJ) in a gas flow passing through the discharge gap depends on both gas-dynamic properties and electrophysical parameters of the plasma jet generator. The paper presents the results of experimental and numerical study of the propagation of the APPJ in a laminar flow of helium. A dielectric-barrier discharge (DBD) generated inside a quartz tube equipped with a coaxial electrode system, which provided gas passing through it, served as a plasma source. The transition of the laminar regime of gas flow into turbulent one was controlled by the photography of a formed plasma jet. The corresponding gas outlet velocity and Reynolds numbers were revealed experimentally and were used to simulate gas dynamics with OpenFOAM software. The data of the numerical simulation suggest that the length of plasma jet at the unvarying electrophysical parameters of DBD strongly depends on the mole fraction of ambient air in a helium flow, which is established along the direction of gas flow. (paper)

  1. Propagation of atmospheric pressure helium plasma jet into ambient air at laminar gas flow

    Science.gov (United States)

    Pinchuk, M.; Stepanova, O.; Kurakina, N.; Spodobin, V.

    2017-05-01

    The formation of an atmospheric pressure plasma jet (APPJ) in a gas flow passing through the discharge gap depends on both gas-dynamic properties and electrophysical parameters of the plasma jet generator. The paper presents the results of experimental and numerical study of the propagation of the APPJ in a laminar flow of helium. A dielectric-barrier discharge (DBD) generated inside a quartz tube equipped with a coaxial electrode system, which provided gas passing through it, served as a plasma source. The transition of the laminar regime of gas flow into turbulent one was controlled by the photography of a formed plasma jet. The corresponding gas outlet velocity and Reynolds numbers were revealed experimentally and were used to simulate gas dynamics with OpenFOAM software. The data of the numerical simulation suggest that the length of plasma jet at the unvarying electrophysical parameters of DBD strongly depends on the mole fraction of ambient air in a helium flow, which is established along the direction of gas flow.

  2. Analytical solutions of heat transfer for laminar flow in rectangular channels

    Directory of Open Access Journals (Sweden)

    Rybiński Witold

    2014-12-01

    Full Text Available The paper presents two analytical solutions namely for Fanning friction factor and for Nusselt number of fully developed laminar fluid flow in straight mini channels with rectangular cross-section. This type of channels is common in mini- and microchannel heat exchangers. Analytical formulae, both for velocity and temperature profiles, were obtained in the explicit form of two terms. The first term is an asymptotic solution of laminar flow between parallel plates. The second one is a rapidly convergent series. This series becomes zero as the cross-section aspect ratio goes to infinity. This clear mathematical form is also inherited by the formulae for friction factor and Nusselt number. As the boundary conditions for velocity and temperature profiles no-slip and peripherally constant temperature with axially constant heat flux were assumed (H1 type. The velocity profile is assumed to be independent of the temperature profile. The assumption of constant temperature at the channel’s perimeter is related to the asymptotic case of channel’s wall thermal resistance: infinite in the axial direction and zero in the peripheral one. It represents typical conditions in a minichannel heat exchanger made of metal.

  3. Response of a laminar premixed flame to flow oscillations: A kinematic model and thermoacoustic instability results

    Energy Technology Data Exchange (ETDEWEB)

    Fleifil, M.; Annaswamy, A.M.; Ghoneim, A.F. [Massachusetts Inst. of Technology, Cambridge, MA (United States); Ghoneim, Z.A. [Ain Shams Univ., Abassia (Egypt)

    1996-09-01

    Combustion instability is a resonance phenomenon that arises due to the coupling between the system acoustics and the unsteady heat release. The constructive feedback between the two processes, which is known to occur as a certain phase relationship between the pressure and the unsteady heat release rate is satisfied, depends on many parameters among which is the acoustic mode, the flame holder characteristics, and the dominant burning pattern. In this paper, the authors construct an analytical model to describe the dynamic response of a laminar premixed flame stabilized on the rim of a tube to velocity oscillation. They consider uniform and nonuniform velocity perturbations superimposed on a pipe flow velocity profile. The model results show that the magnitude of heat release perturbation and its phase with respect to the dynamic perturbation dependent primarily on the flame Strohal number, representing the ratio of the dominant frequency times the tube radius to the laminar burning velocity. In terms of this number, high-frequency perturbations pass through the flame while low frequencies lead to a strong response. The phase with respect to the velocity perturbation behaves in the opposite way. Results of this model are shown to agree with experimental observations and to be useful in determining how the combustion excited model is selected among all the acoustic unstable modes. The model is then used to obtain a time-domain differential equation describing the relationship between the velocity perturbation and the heat release response over the entire frequency range.

  4. Construction of a liver sinusoid based on the laminar flow on chip and self-assembly of endothelial cells.

    Science.gov (United States)

    Mi, Shengli; Yi, Xiaoman; Du, Zhichang; Xu, Yuanyuan; Sun, Wei

    2018-02-20

    The liver is one of the main metabolic organs, and nearly all ingested drugs will be metabolized by the liver. Only a small fraction of drugs are able to come onto the market during drug development, and hepatic toxicity is a major cause for drug failure. Since drug development is costly in both time and materials, an in vitro liver model that can accelerate bioreactions in the liver and reduce drug consumption is imperative in the pharmaceutical industry. The liver on a chip is an ideal alternative for its controllable environment and tiny size, which means constructing a more biomimetic model, reducing material consumption as well as promoting drug diffusion and reaction. In this study, taking advantage of the laminar flow on chips and using natural degradable gel rat tail Collagen-I, we constructed a liver sinusoid on a chip. By synchronously injecting two kinds of cell-laden collagen, HepG2-laden collagen and HUVEC-laden collagen, we formed two collagen layers with a clear borderline. By controlling the HUVEC density and injection of growth factors, HUVECs in collagen formed a monolayer through self-assembly. Thus, a liver sinusoid on a chip was achieved in a more biomimetic environment with a more controllable and uniform distribution of discrete HUVECs. Viability, album secretion and urea synthesis of the live sinusoid on a chip were analysed on days 3, 5 and 7 after collagen injection with acetaminophen treatment at 0 (control), 10 and 20 mM. The results indicated that our liver sinusoid on a chip was able to maintain bioactivity and function for at least 7 d and was beneficial for hepatotoxic drug screening.

  5. Abnormal fetal cerebral laminar organization in cobblestone complex as seen on post-mortem MRI and DTI

    International Nuclear Information System (INIS)

    Widjaja, Elysa; Geibprasert, Sasikhan; Blaser, Susan; Rayner, Tammy; Shannon, Patrick

    2009-01-01

    We report a unique case of cobblestone complex using post-mortem MR and diffusion tensor imaging to assess the laminar organization of the fetal cerebrum. The imaging findings were correlated with autopsy findings. Abnormal cortical development in cobblestone complex resulted in disruption of normal laminar organization of the fetal brain, which was seen as interruption and nodularity of the high-signal T1 cortical band with increased anisotropy and medium diffusivity extending beyond the cortical band into the cerebral mantle on post-mortem MR and diffusion tensor imaging. (orig.)

  6. Abnormal fetal cerebral laminar organization in cobblestone complex as seen on post-mortem MRI and DTI

    Energy Technology Data Exchange (ETDEWEB)

    Widjaja, Elysa; Geibprasert, Sasikhan; Blaser, Susan; Rayner, Tammy [Hospital for Sick Children, Department of Diagnostic Imaging, Toronto (Canada); Shannon, Patrick [University of Toronto, Department of Pathology, Mount Sinai Hospital, Toronto (Canada)

    2009-08-15

    We report a unique case of cobblestone complex using post-mortem MR and diffusion tensor imaging to assess the laminar organization of the fetal cerebrum. The imaging findings were correlated with autopsy findings. Abnormal cortical development in cobblestone complex resulted in disruption of normal laminar organization of the fetal brain, which was seen as interruption and nodularity of the high-signal T1 cortical band with increased anisotropy and medium diffusivity extending beyond the cortical band into the cerebral mantle on post-mortem MR and diffusion tensor imaging. (orig.)

  7. Effect of laminar airflow ventilation on surgical site infections: a systematic review and meta-analysis.

    Science.gov (United States)

    Bischoff, Peter; Kubilay, N Zeynep; Allegranzi, Benedetta; Egger, Matthias; Gastmeier, Petra

    2017-05-01

    The role of the operating room's ventilation system in the prevention of surgical site infections (SSIs) is widely discussed, and existing guidelines do not reflect current evidence. In this context, laminar airflow ventilation was compared with conventional ventilation to assess their effectiveness in reducing the risk of SSIs. We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and WHO regional medical databases from Jan 1, 1990, to Jan 31, 2014. We updated the search for MEDLINE for the period between Feb 1, 2014, and May 25, 2016. We included studies most relevant to our predefined question: is the use of laminar airflow in the operating room associated with the reduction of overall or deep SSI as outcomes in patients of any age undergoing surgical operations? We excluded studies not relevant to the study question, studies not in the selected languages, studies published before Jan 1, 1990, or after May 25, 2016, meeting or conference abstracts, and studies of which the full text was not available. Data were extracted by two independent investigators, with disagreements resolved through further discussion. Authors were contacted if the full-text article was not available, or if important data or information on the paper's content was absent. Studies were assessed for publication bias. Grading of recommendations assessment, development, and evaluation was used to assess the quality of the identified evidence. Meta-analyses were done with RevMan (version 5.3). We identified 1947 records of which 12 observational studies were comparing laminar airflow ventilation with conventional turbulent ventilation in orthopaedic, abdominal, and vascular surgery. The meta-analysis of eight cohort studies showed no difference in risk for deep SSIs following total hip arthroplasty (330 146 procedures, odds ratio [OR] 1·29, 95% CI 0·98-1·71; p=0·07, I 2 =83%). For total knee arthroplasty, the meta-analysis of six cohort studies showed no difference

  8. Combustion and radiation modeling of laminar premixed flames using OpenFOAM: A numerical investigation of radiative heat transfer in the RADIADE project

    DEFF Research Database (Denmark)

    Haider, Sajjad; Pang, Kar Mun; Ivarsson, Anders

    2013-01-01

    This paper presents the computational fluid dynamics modelling of a laminar premixed flame. A specific solver named ’rareLTSFoam’ is developed using OpenFOAM ® code. The solver is used to simulate experimental stoichiometric and rich laminar premixed flames. The modelling is carried out for thermal...

  9. Method for separating isotopes

    International Nuclear Information System (INIS)

    Jepson, B.E.

    1976-01-01

    The invention comprises a method for separating different isotopes of elements from each other by contacting a feed solution containing the different isotopes with a macrocyclic polyether to preferentially form a macrocyclic polyether complex with the lighter of the different isotopes. The macrocyclic polyether complex is then separated from the lighter isotope depleted feed solution. A chemical separation of isotopes is carried out in which a constant refluxing system permits a continuous countercurrent liquid-liquid extraction. (LL)

  10. Exogenous vs. Endogenous Separation

    OpenAIRE

    Ramey, Garey

    2008-01-01

    This paper assesses how various approaches to modelling the separation margin a¤ect the ability of the Mortensen-Pissarides job matching model to explain key facts about the aggregate labor market. Allowing for realistic time variation in the separation rate, whether exogenous or endogenous, greatly in- creases the unemployment variability generated by the model. Speci…cations with exogenous separation rates, whether constant or time-varying, fail to pro- duce realistic volatility and prod...

  11. Method for separating isotopes

    International Nuclear Information System (INIS)

    Schlenker, R.F.

    1978-01-01

    A vortex tube for separating isotopes is described. A gas mixture containing the isotopic molecules enters the vortex tube under pressure and is separated into a hot discharge flow stream and a cold discharge flow stream. The hot discharge is enriched in lighter isotopic molecules whereas the cold discharge flow stream is enriched in the heavier isotopic molecules. The vortex tube can be used in a single stage or multistage isotope separation apparatus

  12. Centrifugal gas separator

    Energy Technology Data Exchange (ETDEWEB)

    Sakurai, M

    1970-03-27

    A centrifugal gas separator of a highly endurable construction and with improved gas sealing qualities utilizes a cylincrical elastic bellows or similar system in cooperation with a system of dynamic pressure operable gas seals as means for removing separated gases from the interior of the rotor drum, collecting the separated gases in their respective separated gas chambers defined by the corresponding bellows and their supporting stationary wall members, gas seals and rotor end caps, and means for discharging to the exterior of the surrounding cylindrical wall member the gaseous components from their respective separated gas chambers. In the vicinity of the rotary drum motor is a mixed gas chamber and means for providing the gas mixture along a co-axial passage into the rotary drum chamber. Orifices are bored into the end caps of the rotary drum to direct the separated gases into the aforementioned separated gas chambers which, through the action of the gas seals, freely slide upon the rotating drum to collect and thereafter discharge the thus separated gases. Therefore, according to the present invention, helium gas used to prevent separated gas remixture is unnecessary and, furthermore, the gas seals and elastic bellows means provide an air-tight seal superior to that of the contact sealing system of the former art.

  13. Entrainment separator performance

    International Nuclear Information System (INIS)

    First, M.W.; Leith, D.

    1976-01-01

    Clean and dust-loaded ACS entrainment separators mounted upstream of HEPA filters were exposed to a combination of fine water mist and steam at about 70 0 C from one to four hours. In every trial, the ACS entrainment separator prevented measurable deterioration of performance in the following HEPA filter. Droplet size-efficiency evaluation of the ACS entrainment separators showed that, within the accuracy of the measurements, they meet all service requirements and are fully equal to the best separator units available for service on pressurized water reactors

  14. Centrifugal gas separator

    International Nuclear Information System (INIS)

    Sakurai, Mitsuo.

    1970-01-01

    A centrifugal gas separator of a highly endurable construction and with improved gas sealing qualities utilizes a cylincrical elastic bellows or similar system in cooperation with a system of dynamic pressure operable gas seals as means for removing separated gases from the interior of the rotor drum, collecting the separated gases in their respective separated gas chambers defined by the corresponding bellows and their supporting stationary wall members, gas seals and rotor end caps, and means for discharging to the exterior of the surrounding cylindrical wall member the gaseous components from their respective separated gas chambers. In the vicinity of the rotary drum motor is a mixed gas chamber and means for providing the gas mixture along a co-axial passage into the rotary drum chamber. Orifices are bored into the end caps of the rotary drum to direct the separated gases into the aforementioned separated gas chambers which, through the action of the gas seals, freely slide upon the rotating drum to collect and thereafter discharge the thus separated gases. Therefore, according to the present invention, helium gas used to prevent separated gas remixture is unnecessary and, furthermore, the gas seals and elastic bellows means provide an air-tight seal superior to that of the contact sealing system of the former art. (K.J. Owens)

  15. Separation of ionic solutes

    International Nuclear Information System (INIS)

    1986-01-01

    The conference proceedings contain 44 papers of which 19 were incorporated in INIS. The subject of these is the use of solvent extraction or emulsion membrane extraction for separation of fission products, rare earth compounds and actinide compunds; the sorption of radionuclides; and the use of adsorbents and chelating agents in separation processes. (J.P.)

  16. Process for isotope separation

    International Nuclear Information System (INIS)

    Schuster, E.; Kersting, A.; Gebauhr, W.

    1980-01-01

    Isotope separation in UF 6 gas takes place on the principle of selective excitation by laser irradiation and separation by chemical conversion with a partner in a reaction. Atomic H, N or O or the CH 3 or CHO radicals are suitable partners in the reaction. The recombination takes place by catalytic acceleration on leaving the reaction area. (DG) [de

  17. Separation of uranium isotopes

    International Nuclear Information System (INIS)

    Porter, J.T.

    1980-01-01

    Methods and apparatus are disclosed for separation of uranium isotopes by selective isotopic excitation of photochemically reactive uranyl salt source material at cryogenic temperatures, followed by chemical separation of selectively photochemically reduced U+4 thereby produced from remaining uranyl source material

  18. Isotope separation process

    International Nuclear Information System (INIS)

    Lyon, R.K.

    1979-01-01

    A method is described for the isotopically selective excitation of gas phase molecules by multiple infrared photon absorption after which more of the excited molecules than nonexcited molecules are converted to a chemically different form which may be separated by means known in the art. This invention is useful for, but not limited to, the separation of the principal isotopes of uranium

  19. Separation anxiety disorder

    NARCIS (Netherlands)

    Nauta, M.H.; Emmelkamp, P.M.G.; Sturmey, P.; Hersen, M.

    2012-01-01

    Separation anxiety disorder (SAD) is the only anxiety disorder that is specific to childhood; however, SAD has hardly ever been addressed as a separate disorder in clinical trials investigating treatment outcome. So far, only parent training has been developed specifically for SAD. This particular

  20. Method for separating isotopes

    International Nuclear Information System (INIS)

    Jepson, B.E.

    1975-01-01

    Isotopes are separated by contacting a feed solution containing the isotopes with a cyclic polyether wherein a complex of one isotope is formed with the cyclic polyether, the cyclic polyether complex is extracted from the feed solution, and the isotope is thereafter separated from the cyclic polyether

  1. Influence of thermal radiation on soot production in Laminar axisymmetric diffusion flames

    International Nuclear Information System (INIS)

    Demarco, R.; Nmira, F.; Consalvi, J.L.

    2013-01-01

    The aim of this paper is to study the effect of radiative heat transfer on soot production in laminar axisymmetric diffusion flames. Twenty-four C 1 –C 3 hydrocarbon–air flames, consisting of normal (NDF) and inverse (IDF) diffusion flames at both normal gravity (1 g) and microgravity (0 g), and covering a wide range of conditions affecting radiative heat transfer, were simulated. The numerical model is based on the Steady Laminar Flamelet (SLF) model, a semi-empirical two-equation acetylene/benzene based soot model and the Statistical Narrow Band Correlated K (SNBCK) model coupled to the Finite Volume Method (FVM) to compute thermal radiation. Predictions relative to velocity, temperature, soot volume fraction and radiative losses are on the whole in good agreement with the available experimental data. Model results show that, for all the flames considered, thermal radiation is a crucial process with a view to providing accurate predictions for temperatures and soot concentrations. It becomes increasingly significant from IDFs to NDFs and its influence is much greater as gravity is reduced. The radiative contribution of gas prevails in the weakly-sooting IDFs and in the methane and ethane NDFs, whereas soot radiation dominates in the other flames. However, both contributions are significant in all cases, with the exception of the 1 g IDFs investigated where soot radiation can be ignored. The optically-thin approximation (OTA) was also tested and found to be applicable as long as the optical thickness, based on flame radius and Planck mean absorption coefficient, is less than 0.05. The OTA is reasonable for the IDFs and for most of the 1 g NDFs, but it fails to predict the radiative heat transfer for the 0 g NDFs. The accuracy of radiative-property models was then assessed in the latter cases. Simulations show that the gray approximation can be applied to soot but not to combustion gases. Both the non-gray and gray soot versions of the Full Spectrum Correlated

  2. Endoscopic component separation for ventral hernia causes fewer wound complications compared to open components separation

    DEFF Research Database (Denmark)

    Jensen, Kristian K; Henriksen, Nadia A; Jorgensen, Lars N

    2014-01-01

    -analysis reporting on a total of 163 patients. Patient demography and the rates of mesh repair were comparable between the ECS and OCS patient groups. The incidence of wound complications comprising surgical site infection, skin necrosis, subcutaneous abscess, seroma, skin dehiscence, cellulitis, and fistula...

  3. AEROSOL NUCLEATION AND GROWTH DURING LAMINAR TUBE FLOW: MAXIMUM SATURATIONS AND NUCLEATION RATES. (R827354C008)

    Science.gov (United States)

    An approximate method of estimating the maximum saturation, the nucleation rate, and the total number nucleated per second during the laminar flow of a hot vapour–gas mixture along a tube with cold walls is described. The basis of the approach is that the temperature an...

  4. Separation of tritiated water using graphene oxide membrane

    Energy Technology Data Exchange (ETDEWEB)

    Sevigny, Gary J. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Motkuri, Radha K. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Gotthold, David W. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Fifield, Leonard S. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Frost, Anthony P. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Bratton, Wesley [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

    2015-06-28

    In future nuclear fuel reprocessing plants and possibly for nuclear power plants, the cleanup of tritiated water will be needed for hundreds of thousands of gallons of water with low activities of tritium. This cleanup concept utilizes graphene oxide laminar membranes (GOx) for the separation of low-concentration (10-3-10 µCi/g) tritiated water to create water that can be released to the environment and a much smaller waste stream with higher tritium concentrations. Graphene oxide membranes consist of hierarchically stacked, overlapping molecular layers and represent a new class of materials. A permeation rate test was performed with a 2-µm-thick cast Asbury membrane using mixed gas permeability testing with zero air (highly purified atmosphere) and with air humidified with either H2O or D2O to a nominal 50% relative humidity. The membrane permeability for both H2O and D2O was high with N2 and O2 at the system measurement limit. The membrane water permeation rate was compared to a Nafion® membrane and the GOx permeation was approximately twice as high at room temperature. The H2O vapor permeation rate was 5.9 × 102 cc/m2/min (1.2 × 10-6 g/min-cm2), which is typical for graphene oxide membranes. To demonstrate the feasibility of such isotopic water separation through GOX laminar membranes, an experimental setup was constructed to use pressure-driven separation by heating the isotopic water mixture at one side of the membrane to create steam while cooling the other side. Several membranes were tested and were prepared using different starting materials and by different pretreatment methods. The average separation result was 0.8 for deuterium and 0.6 for tritium. Higher or lower temperatures may also improve separation efficiency but neither has been tested yet. A rough estimate of cost compared to current technology was also included as an indication of potential viability of the process. The relative process costs were based on the rough size of facility to

  5. Isotope separation process

    International Nuclear Information System (INIS)

    Cox, D.M.; Maas, E.T.

    1982-01-01

    Processes are disclosed for the separation of isotopes of an element comprising vaporizing uranyl compounds having the formula (UO2a2)n, where a is a monovalent anion and n in an integer from 2 to 4, the compounds having an isotopically shifted infrared absorption spectrum associated with uranyl ions containing said element which is to be separated, and then irradiating the uranyl compound with infrared radiation which is preferentially absorbed by a molecular vibration of uranyl ions of the compound containing a predetermined isotope of that element so that excited molecules of the compound are provided which are enriched in the molecules of the compound containing that predetermined isotope, thus enabling separation of these excited molecules. The processes disclosed include separation of the excited molecules by irradiating under conditions such that the excited molecules dissociate, and also separating the excited molecules by a discrete separation step. The latter includes irradiating the excited molecules by a second infrared laser in order to convert the excited molecules into a separable product, or also by chemically converting the excited molecules, preferably by reaction with a gaseous reactant

  6. Laminar forced convective heat transfer to near-critical water in a tube

    International Nuclear Information System (INIS)

    Lee, Sang Ho

    2003-01-01

    Numerical modeling is carried out to investigate forced convective heat transfer to near-critical water in developing laminar flow through a circular tube. Due to large variations of thermo-physical properties such as density, specific heat, viscosity, and thermal conductivity near thermodynamic critical point, heat transfer characteristics show quite different behavior compared with pure forced convection. With flow acceleration along the tube unusual behavior of heat transfer coefficient and friction factor occurs when the fluid enthalpy passes through pseudocritical point of pressure in the tube. There is also a transition behavior from liquid-like phase to gas-like phase in the developing region. Numerical results with constant heat flux boundary conditions are obtained for reduced pressures from 1.09 to 1.99. Graphical results for velocity, temperature, and heat transfer coefficient with Stanton number are presented and analyzed

  7. Dual reciprocity boundary element analysis for the laminar forced heat convection problem in concentric annulus

    International Nuclear Information System (INIS)

    Choi, Chang Yong

    1999-01-01

    This paper presents a study of the Dual Reciprocity Boundary Element Method (DRBEM) for the laminar heat convection problem in a concentric annulus with constant heat flux boundary condition. DRBEM is one of the most successful technique used to transform the domain integrals arising from the nonhomogeneous term of the poisson equation into equivalent boundary only integrals. This recently developed and highly efficient numerical method is tested for the solution accuracy of the fluid flow and heat transfer study in a concentric annulus. Since their exact solutions are available, DRBEM solutions are verified with different number of boundary element discretization and internal points. The results obtained in this study are discussed with the relative error percentage of velocity and temperature solutions, and potential applicability of the method for the more complicated heat convection problems with arbitrary duct geometries

  8. Conjugate heat transfer of laminar film condensation along a horizontal plate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Euk Soo [Pusan National Univesity, Busan (Korea, Republic of)

    2006-03-15

    This paper proposes appropriate conjugate parameters and dimensionless temperatures to analysis the conjugate problem of heat conduction in solid wall coupled with laminar film condensation flow adjacent to horizontal flat plate. An efficient methods for some fluids are proposed for its solution. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Modified Jacob number, Ja{sup *}/Pr, defined by an overall temperature difference, a property ratio {radical}{rho}{sub {iota}}{mu}{sub {iota}} {radical}{rho}{sub {upsilon}}{mu}{sub {upsilon}} and the conjugate parameter {zeta}. The obtained similarity solution reveals the effect of the conjugate parameter, and the results are compared with the simplified solution. The variations of the heat transfer rates as well as the interface temperature and frictions along the plate are shown explicitly.

  9. F-16XL Ship #2 in hangar for Laminar Flow Glove mounting

    Science.gov (United States)

    1995-01-01

    NASA's two-seat F-16XL research aircraft is shown in the modification hangar at the Dryden Flight Research Center, Edwards, California, during installation of a titanium 'glove' on the upper surface of its modified left wing. The aircraft subsequently concluded a 13 month-long, 45-flight research program which investigated drawing off a small portion of the boundary-layer air in order to provide laminar -- or smooth -- flow over a major portion of a wing flying at supersonic speeds. A turbo-compressor in the aircraft's fuselage provided suction to draw air through more than 10 million tiny laser-drilled holes in the glove via a manifold system employing 20 valves. Data obtained during the program could assist designers of future high-speed aircraft in developing a more efficient civil transport.

  10. Numerical and experimental study on laminar round free jet of Ar discharging into stagnant air

    International Nuclear Information System (INIS)

    Fumizawa, Motoo; Hishida, Makoto; Kunugi, Tomoaki

    1990-01-01

    The objective of the present study is to investigate numerically and experimentally the behavior of the fluid flow and the mass transfer of argon gas (Ar) laminar round jet discharging into stagnant air along the gravity force. The SIMPLE method and two differential numerical schemes of PLDS and QUICK are used in the TEAM code modified by adding the binary diffusion equation. The solution domain is comprised of 80X40 grids of uniform size. As the result, the following were obtained: The half radius of Ar mass fraction obtained by QUICK was in good agreement with experimental result. The half radii of axial velocity and Ar mass fraction obtained by PLDS were larger than those by QUICK due to numerical viscosity. Numerical analyses by PLDS and QUICK schemes agreed well with experimental results on centerline Ar mass fraction. Computational times of PLDS and QUICK are about 40 min. and 120 min. respectively by FACOM VP100 computer in JAERI. (author)

  11. Flash pyrolysis of agricultural residues using a plasma heated laminar entrained flow reactor

    International Nuclear Information System (INIS)

    Xiu Shuangning; Yi Weiming; Li Baoming

    2005-01-01

    In order to study the volatilization characteristics of biomass particles at flash heating rates, a plasma heated laminar entrained flow reactor (PHLEFR) was designed and built in our lab. Two agricultural residues, wheat straw and corn stalk, were chosen as feedstock for pyrolysis which were conducted on the PHLEFR with the aim of determining the extent of thermal decomposition at high heating rate (more than 10 4o Cs -1 ). Based on the experimental data, a first order kinetic model was introduced and the relevant kinetic parameters (apparent active energy and apparent frequency factor) were determined for the two straws: E=31.51kJmol -1 , A=1028s -1 (wheat straw) and E=33.74kJmol -1 , A=1013s -1 (corn stalk). The predicted conversion of the fitted model to the experimental data provided general agreements when one considered the experimental errors

  12. Solution for laminar natural convection flows in a square cavity with temperature dependent viscosity

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, J.G. [Parsons Brinckerhoff, New York, NY (United States)

    1995-12-31

    This paper presents an examination of numerical results for the buoyancy-driven convection heat transfer problem, in a two-dimensional enclosure under steady-state, laminar, incompressible, and temperature dependent viscosity fluid flow conditions. The vertical walls are exposed to different temperatures and the top and bottom are insulated. Rayleigh numbers of 10{sup 4}, 10{sup 5}, and 10{sup 6} are considered. Specific heat, thermal conductivity, and the thermal expansion coefficient are assumed constant. Density variation is included using the Oberbeck-Boussinesq approximation. The results are obtained using the SIMPLEC solution technique based on a power-law, finite-volume discretization scheme. The hydrodynamic and thermal fields are presented at various locations in the enclosures.

  13. Intriguingly high convective heat transfer enhancement of nanofluid coolants in laminar flows

    Science.gov (United States)

    Xie, Huaqing; Li, Yang; Yu, Wei

    2010-05-01

    We reported on investigation of the convective heat transfer enhancement of nanofluids as coolants in laminar flows inside a circular copper tube with constant wall temperature. Nanofluids containing Al 2O 3, ZnO, TiO 2, and MgO nanoparticles were prepared with a mixture of 55 vol.% distilled water and 45 vol.% ethylene glycol as base fluid. It was found that the heat transfer behaviors of the nanofluids were highly depended on the volume fraction, average size, species of the suspended nanoparticles and the flow conditions. MgO, Al 2O 3, and ZnO nanofluids exhibited superior enhancements of heat transfer coefficient, with the highest enhancement up to 252% at a Reynolds number of 1000 for MgO nanofluid. Our results demonstrated that these oxide nanofluids might be promising alternatives for conventional coolants.

  14. Intriguingly high convective heat transfer enhancement of nanofluid coolants in laminar flows

    International Nuclear Information System (INIS)

    Xie Huaqing; Li Yang; Yu Wei

    2010-01-01

    We reported on investigation of the convective heat transfer enhancement of nanofluids as coolants in laminar flows inside a circular copper tube with constant wall temperature. Nanofluids containing Al 2 O 3 , ZnO, TiO 2 , and MgO nanoparticles were prepared with a mixture of 55 vol.% distilled water and 45 vol.% ethylene glycol as base fluid. It was found that the heat transfer behaviors of the nanofluids were highly depended on the volume fraction, average size, species of the suspended nanoparticles and the flow conditions. MgO, Al 2 O 3 , and ZnO nanofluids exhibited superior enhancements of heat transfer coefficient, with the highest enhancement up to 252% at a Reynolds number of 1000 for MgO nanofluid. Our results demonstrated that these oxide nanofluids might be promising alternatives for conventional coolants.

  15. Intriguingly high convective heat transfer enhancement of nanofluid coolants in laminar flows

    Energy Technology Data Exchange (ETDEWEB)

    Xie Huaqing, E-mail: hqxie@eed.sspu.c [School of Urban Development and Environmental Engineering, Shanghai Second Polytechnic University, Shanghai 201209 (China); Li Yang; Yu Wei [School of Urban Development and Environmental Engineering, Shanghai Second Polytechnic University, Shanghai 201209 (China)

    2010-05-31

    We reported on investigation of the convective heat transfer enhancement of nanofluids as coolants in laminar flows inside a circular copper tube with constant wall temperature. Nanofluids containing Al{sub 2}O{sub 3}, ZnO, TiO{sub 2}, and MgO nanoparticles were prepared with a mixture of 55 vol.% distilled water and 45 vol.% ethylene glycol as base fluid. It was found that the heat transfer behaviors of the nanofluids were highly depended on the volume fraction, average size, species of the suspended nanoparticles and the flow conditions. MgO, Al{sub 2}O{sub 3}, and ZnO nanofluids exhibited superior enhancements of heat transfer coefficient, with the highest enhancement up to 252% at a Reynolds number of 1000 for MgO nanofluid. Our results demonstrated that these oxide nanofluids might be promising alternatives for conventional coolants.

  16. Eulerian-Eulerian two-phase numerical simulation of nanofluid laminar forced convection in a microchannel

    International Nuclear Information System (INIS)

    Kalteh, Mohammad; Abbassi, Abbas; Saffar-Avval, Majid; Harting, Jens

    2011-01-01

    In this paper, laminar forced convection heat transfer of a copper-water nanofluid inside an isothermally heated microchannel is studied numerically. An Eulerian two-fluid model is considered to simulate the nanofluid flow inside the microchannel and the governing mass, momentum and energy equations for both phases are solved using the finite volume method. For the first time, the detailed study of the relative velocity and temperature of the phases are presented and it has been observed that the relative velocity and temperature between the phases is very small and negligible and the nanoparticle concentration distribution is uniform. However, the two-phase modeling results show higher heat transfer enhancement in comparison to the homogeneous single-phase model. Also, the heat transfer enhancement increases with increase in Reynolds number and nanoparticle volume concentration as well as with decrease in the nanoparticle diameter, while the pressure drop increases only slightly.

  17. Modified rational Legendre approach to laminar viscous flow over a semi-infinite flat plate

    International Nuclear Information System (INIS)

    Tajvidi, T.; Razzaghi, M.; Dehghan, M.

    2008-01-01

    A numerical method for solving the classical Blasius' equation is proposed. The Blasius' equation is a third order nonlinear ordinary differential equation , which arises in the problem of the two-dimensional laminar viscous flow over a semi-infinite flat plane. The approach is based on a modified rational Legendre tau method. The operational matrices for the derivative and product of the modified rational Legendre functions are presented. These matrices together with the tau method are utilized to reduce the solution of Blasius' equation to the solution of a system of algebraic equations. A numerical evaluation is included to demonstrate the validity and applicability of the method and a comparison is made with existing results

  18. Proper orthogonal decomposition applied to laminar thermal convection in a vertical two plate channel

    International Nuclear Information System (INIS)

    Alvarez-Herrera, C; Murillo-Ramírez, J G; Pérez-Reyes, I; Moreno-Hernández, D

    2015-01-01

    This work reports the thermal convection with imposed shear flow in a thin two-plate channel. Flow structures are investigated under heating asymmetric conditions and different laminar flow conditions. The dynamics of heat flow and the energy distribution were determined by visualization with the Schlieren technique and application of the proper orthogonal decomposition (POD) method. The obtained results from the POD mode analysis revealed that for some flow conditions the heat transfer is related to the energy of the POD modes and their characteristic numbers. It was possible to detect periodic motion in the two-plate channel flow from the POD mode analysis. It was also found that when the energy is distributed among many POD modes, the fluid flow is disorganized and unsteady. (paper)

  19. The effect of laminar air flow and door openings on operating room contamination.

    Science.gov (United States)

    Smith, Eric B; Raphael, Ibrahim J; Maltenfort, Mitchell G; Honsawek, Sittisak; Dolan, Kyle; Younkins, Elizabeth A

    2013-10-01

    We evaluate the association of laminar airflow (LAF) and OR traffic with intraoperative contamination rates. Two sterile basins were placed in each room during 81 cases, one inside and one outside the LAF. One Replicate Organism Detection and Counting (RODAC) plate from each basin was sent for culture at successive 30-minute intervals from incision time until wound closure. At successive 30-minute intervals more plates were contaminated outside than inside the LAF. A negative binomial model showed that the bacteria colony forming units (CFU) depended on whether there were any door openings (P=0.02) and the presence of LAF (P=0.003). LAF decreases CFU by 36.6%. LAF independently reduces the risk of contamination and microbial counts for surgeries lasting 90 minutes or less. © 2013.

  20. Study of Cooling Characteristic of The Containment APWR Model Using Laminar Subcooled Water Film

    International Nuclear Information System (INIS)

    Diah Hidayanti; Aryadi Suwono; Nathanael P Tandian; Ari Darmawan Pasek; Efrizon Umar

    2009-01-01

    One of mechanism utilized by the next-generation pressurized water reactor for cooling its containment passively is gravitationally falling water spray cooling. This paper focuses on the characteristic study using Fluent 5/6 program for the case of the containment outer wall cooling by laminar sub-cooled water film. The cooling system characteristics which will be discussed consist of water film thickness and temperature on all parts of the containment wall as well as the effect of water spray volume flow rate on the water film thickness and convection heat transfer capability from the containment wall to the film bulk. In addition, some kinds of non dimensional numbers involved in the film heat transfer correlation will be presented in this paper. (author)

  1. PACAP decides neuronal laminar fate via PKA signaling in the developing cerebral cortex

    International Nuclear Information System (INIS)

    Ohtsuka, Masanari; Fukumitsu, Hidefumi; Furukawa, Shoei

    2008-01-01

    Laminar formation in the developing cerebral cortex requires the precisely regulated generation of phenotype-specified neurons. To test the possible involvement of pituitary adenylate cyclase-activating polypeptide (PACAP) in this formation, we investigated the effects of PACAP administered into the telencephalic ventricular space of 13.5-day-old mouse embryos. PACAP partially inhibited the proliferation of cortical progenitors and altered the position and gene-expression profiles of newly generated neurons otherwise expected for layer IV to those of neurons for the deeper layers, V and VI, of the cerebral cortex. The former and latter effects were seen only when the parent progenitor cells were exposed to PACAP in the later and in earlier G1 phase, respectively; and these effects were suppressed by co-treatment with a protein kinase A (PKA) inhibitor. These observations suggest that PACAP participates in the processes forming the neuronal laminas in the developing cortex via the intracellular PKA pathway

  2. Accuracy and Precision of Plane Wave Vector Flow Imaging for Laminar and Complex Flow In Vivo

    DEFF Research Database (Denmark)

    Jensen, Jonas; Traberg, Marie Sand; Villagómez Hoyos, Carlos Armando

    2017-01-01

    In this study, a comparison between velocity fields for a plane wave 2-D vector flow imaging (VFI) method and a computational fluid dynamics (CFD) simulation is made. VFI estimates are obtained from the scan of a flow phantom, which mimics the complex flow conditions in the carotid artery....... Furthermore, the precision of the VFI method is investigated under laminar and complex flow conditions in vivo. The carotid bifurcation of a healthy volunteer was scanned using both fast plane wave ultrasound and magnetic resonance imaging (MRI). The acquired MRI geometry of the bifurcation was used...... difference within 15 %, however, it was 23 % in the external branch. For the in vivo scan, the precision in terms of mean standard deviation (SD) of estimates aligned to the cardiac cycle was highest in the center of the common carotid artery (SD 4.7◦ for angles) and lowest in the external branch and close...

  3. Fine structure symmetry-breaking in decaying passive scalars advected by laminar shear flow

    Science.gov (United States)

    Bernardi, Francesca; Aminian, Manuchehr; Camassa, Roberto; Harris, Daniel; McLaughlin, Richard; UNC Joint Applied Mathematics; Marine Sciences Fluids Lab Team

    2017-11-01

    We investigate the dispersion of a passive scalar in laminar shear flow through rectangular and elliptical channels. We show through simulation, analysis and experiments that the cross-sectional aspect ratio sets the sign of the average skewness at long times, which describes the longitudinal asymmetry of the tracer distribution. We then extend the results to study the entire tracer distribution rather than only its longitudinal moments. With an analytical approach, we show that it is possible to describe the behavior of the tracer distribution at long time at any location in the cross-section, in turn highlighting the mechanism by which symmetry is broken. Future directions will be discussed. ONR Grant DURIP N00014-12-1-0749. NSF Grants RTG DMS-0943851, CMG ARC-1025523, DMS-1009750, and DMS-1517879.

  4. Material utilizado en la construcción de estructuras laminares

    Directory of Open Access Journals (Sweden)

    Parsons, John K.

    1979-09-01

    Full Text Available This article deals with the materials used in the various types of laminated structures: spherical, cylindrical and hyperbolic. The work shows particularly the geometric and structural features of the «ENSPHERE» reticular spheric dome built with laminated timber and discusses its behaviour under various loads, the method followed in its structural analysis and the different tests performed.

    Este articulo trata de los materiales empleados en las distintas formas de estructuras laminares: esféricas, cilíndricas e hiperbólicas. De una manera especial se ven las características, tanto geométricas como estructurales, de la bóveda reticulada esférica «ENSPHERE» construida con madera laminada, su comportamiento frente a las diversas cargas, el método seguido para su análisis estructural, así como los diversos ensayos realizados.

  5. Tratamento conservador dos hematomas extradurais laminares na infância

    Directory of Open Access Journals (Sweden)

    Orildo Ciquini Júnior

    1992-12-01

    Full Text Available Os autores relatam sua experiência com o tratamento conservador de 15 crianças com hematoma extradural (HED laminar traumático. Todas, por ocasião do diagnóstico, apresentavam-se neurologicamente estáveis e sem sinais de herniação intracraniana. Estes HED foram descobertos em períodos de 30 minutos e 5 dias depois do trauma, a maioria estando localizados na região parietal. OHED foi reabsorvido espontaneamente em todos os casos, num período que variou de 2 a 12 dias. Os critérios para seleção destes pacientes e os cuidados com essa modalidade de tratamento do HED são discutidos.

  6. Effect of radiation on the laminar convective heat transfer through a layer of highly porous medium

    International Nuclear Information System (INIS)

    Lee, K.; Howell, J.R.

    1986-01-01

    A numerical investigation is reported of the coupled forced convective and radiative transfer through a highly porous medium. The porosity range investigated is high enough that the fluid inertia terms in the momentum equation cannot be neglected; i.e., the simple form of Darcy's law is invalid. The geometry studied is a plane layer of highly porous medium resting on one impermeable boundary and exposed to a two-dimensional laminar external flow field. The objective is to determine the effective overall heat transfer coefficients for such a geometry. The results are applicable to diverse situations, including insulation batts exposed to external flow, the heat loss and drying rates of grain fields and forest areas, and the drying of beds of porous material exposed to convective and radiative heating

  7. Heat-and-mass transfer during a laminar dissociating gas flow in eccentric annular channels

    International Nuclear Information System (INIS)

    Besedina, T.V.; Udot, A.V.; Yakushev, A.P.

    1987-01-01

    An algorithm to calculate heat-and-mass transfer processes during dissociating gas laminar flow in an eccentric annular channels is considered. Analytical solutions of the heat transfer equations for a rod clodding and gap with boundary conditions of conjugation of temperatures and heat fluxes have been used to determine temperature field. This has made it possible to proceed from slution of the conjugate problem to solution of the equation of energy only for the coolant. The results of calculation of temperature distribution along the cladding for different values of its eccentricity and thermal conductivity coefficient both for the case of frozen flow and in the presence of chemical reactions in the flow are given. When calculating temperatures with conjugation boundary conditions temperature gradients in azimuthal direction are far less and heat transfer in concentration diffusion is carried out mainly in radial direction

  8. Laminar-turbulent transition tripped by step on transonic compressor profile

    Science.gov (United States)

    Flaszynski, Pawel; Doerffer, Piotr; Szwaba, Ryszard; Piotrowicz, Michal; Kaczynski, Piotr

    2018-02-01

    The shock wave boundary layer interaction on the suction side of transonic compressor blade is one of the main objectives of TFAST project (Transition Location Effect on Shock Wave Boundary Layer Interaction). The experimental and numerical results for the flow structure investigations are shown for the flow conditions as the existing ones on the suction side of the compressor profile. The two cases are investigated: without and with boundary layer tripping device. In the first case, boundary layer is laminar up to the shock wave, while in the second case the boundary layer is tripped by the step. Numerical results carried out by means of Fine/Turbo Numeca with Explicit Algebraic Reynolds Stress Model including transition modeling are compared with schlieren, Temperature Sensitive Paint and wake measurements. Boundary layer transition location is detected by Temperature Sensitive Paint.

  9. Deuterium isotope separation

    International Nuclear Information System (INIS)

    Benson, S.W.

    1979-01-01

    Deuterium-containing molecules are separated and enriched by exposing commercially available ethylene, vinyl chloride, 1,2-dichloroethane or propylene to the radiation of tuned infrared lasers to selectively decompose these compounds into enriched molecular products containing deuterium atoms. The deuterium containing molecules can be easily separated from the starting material by absorption, distillation or other simple chemical separation techniques and methods. After evaporation such deuterium containing molecules can be burned to form water with an enriched deuterium content or pyrolyzed to form hydrogen gas with an enriched deuterium content. (author)

  10. Chromatographic hydrogen isotope separation

    International Nuclear Information System (INIS)

    Aldridge, F.T.

    1983-01-01

    Intermetallic compounds with the CaCu5 type of crystal structure, particularly LaNiCo and CaNi5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation column. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale multi-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors

  11. Chromatographic hydrogen isotope separation

    International Nuclear Information System (INIS)

    Aldridge, F.T.

    1981-01-01

    Intermetallic compounds with the CaCu5 type of crystal structure , particularly LaNiCo and CaNi5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors

  12. Magnetic separations in biotechnology.

    Science.gov (United States)

    Borlido, L; Azevedo, A M; Roque, A C A; Aires-Barros, M R

    2013-12-01

    Magnetic separations are probably one of the most versatile separation processes in biotechnology as they are able to purify cells, viruses, proteins and nucleic acids directly from crude samples. The fast and gentle process in combination with its easy scale-up and automation provide unique advantages over other separation techniques. In the midst of this process are the magnetic adsorbents tailored for the envisioned target and whose complex synthesis spans over multiple fields of science. In this context, this article reviews both the synthesis and tailoring of magnetic adsorbents for bioseparations as well as their ultimate application. Copyright © 2013 Elsevier Inc. All rights reserved.

  13. MRI of Retinal Free Radical Production With Laminar Resolution In Vivo

    Science.gov (United States)

    Berkowitz, Bruce A.; Lewin, Alfred S.; Biswal, Manas R.; Bredell, Bryce X.; Davis, Christopher; Roberts, Robin

    2016-01-01

    Purpose Recent studies have suggested the hypothesis that quench-assisted 1/T1 magnetic resonance imaging (MRI) measures free radical production with laminar resolution in vivo without the need of a contrast agent. Here, we test this hypothesis further by examining the spatial and detection sensitivity of quench-assisted 1/T1 MRI to strain, age, or retinal cell layer-specific genetic manipulations. Methods We studied: adult wild-type mice; mice at postnatal day 7 (P7); cre dependent retinal pigment epithelium (RPE)-specific MnSOD knockout mice; doxycycline-treated Sod2flox/flox mice lacking the cre transgene; and α-transducin knockout (Gnat1−/−) mice on a C57Bl/6 background. Transretinal 1/T1 profiles were mapped in vivo in the dark without or with antioxidant treatment, or followed by light exposure. We calibrated profiles spatially using optical coherence tomography. Results Dark-adapted RPE-specific MnSOD knockout mice had greater than normal 1/T1 in the RPE and outer nuclear layers that was corrected to wild-type levels by antioxidant treatment. Dark and light Gnat1−/− mice also had greater than normal outer retinal 1/T1 values. In adult wild-type mice, dark values of 1/T1 in the ellipsoid region and in the outer segment were suppressed by 13 minutes of light. By 29 minutes of light, 1/T1 reduction extended to the outer nuclear layer. Gnat1−/− mice demonstrated a faster light-evoked suppression of 1/T1 values in the outer retina. In P7 mice, transretinal 1/T1 profiles were the same in dark and light. Conclusions Quench-assisted MRI has the laminar resolution and detection sensitivity to evaluate normal and pathologic production of free radicals in vivo. PMID:26886890

  14. Stability enhancement of ozone-assisted laminar premixed Bunsen flames in nitrogen co-flow

    KAUST Repository

    Vu, Tran Manh

    2014-04-01

    Ozone (O3) is known as one of the strongest oxidizers and therefore is widely used in many applications. Typically in the combustion field, a combination of non-thermal plasma and combustion systems have been studied focusing on the effects of ozone on flame propagation speeds and ignition characteristics. Here, we experimentally investigated the effects of ozone on blowoff of premixed methane/air and propane/air flames over a full range of equivalence ratios at room temperature and atmospheric pressure by using a co-flow burner and a dielectric barrier discharge. The results with ozone showed that a nozzle exit jet velocity at the moment of flame blowoff (blowoff velocity) significantly increased, and flammability limits for both fuel-lean and rich mixtures were also extended. Ozone had stronger effects of percent enhancement in the blowoff velocity for off-stoichiometric mixtures, while minimum enhancements could be observed around stoichiometric conditions for both fuels showing linear positive dependence on a tested range of ozone concentration up to 3810ppm. Through chemical kinetic simulations, the experimentally observed trends of the enhancement in blowoff velocity were identified as a result of the modification of the laminar burning velocity. Two ozone decomposition pathways of O3+N2→O+O2+N2 and O3+H→O2+OH were identified as the most controlling steps. These reactions, coupled with fuel consumption characteristics of each fuel determined the degree of promotion in laminar burning velocities, supporting experimental observations on blowoff velocities with ozone addition. © 2013 The Combustion Institute.

  15. Effect of diluents on soot precursor formation and temperature in ethylene laminar diffusion flames

    KAUST Repository

    Abhinavam Kailasanathan, Ranjith Kumar

    2013-03-01

    Soot precursor species concentrations and flame temperature were measured in a diluted laminar co-flow jet diffusion flame at pressures up to eight atmospheres while varying diluent type. The objective of this study was to gain a better understanding of soot production and oxidation mechanisms, which could potentially lead to a reduction in soot emissions from practical combustion devices. Gaseous samples were extracted from the centerline of an ethylene-air laminar diffusion flame, which was diluted individually with four diluents (argon, helium, nitrogen, and carbon dioxide) to manipulate flame temperature and transport properties. The diluted fuel and co-flow exit velocities (top-hat profiles) were matched at all pressures to minimize shear-layer effects, and the mass fluxes were fixed over the pressure range to maintain constant Reynolds number. The flame temperature was measured using a fine gauge R-type thermocouple at pressures up to four atmospheres. Centerline concentration profiles of major non-fuel hydrocarbons collected via extractive sampling with a quartz microprobe and quantification using GC/MS+FID are reported within. The measured hydrocarbon species concentrations are vary dramatically with pressure and diluent, with the helium and carbon dioxide diluted flames yielding the largest and smallest concentrations of soot precursors, respectively. In the case of C2H2 and C6H6, two key soot precursors, helium diluted flames had concentrations more than three times higher compared with the carbon dioxide diluted flame. The peak flame temperature vary with diluents tested, as expected, with carbon dioxide diluted flame being the coolest, with a peak temperature of 1760K at 1atm, and the helium diluted flame being the hottest, with a peak temperature of 2140K. At four atmospheres, the helium diluted flame increased to 2240K, but the CO2 flame temperature increased more, decreasing the difference to approximately 250K. © 2012 The Combustion Institute.

  16. Drag reduction using wrinkled surfaces in high Reynolds number laminar boundary layer flows

    Science.gov (United States)

    Raayai-Ardakani, Shabnam; McKinley, Gareth H.

    2017-09-01

    Inspired by the design of the ribbed structure of shark skin, passive drag reduction methods using stream-wise riblet surfaces have previously been developed and tested over a wide range of flow conditions. Such textures aligned in the flow direction have been shown to be able to reduce skin friction drag by 4%-8%. Here, we explore the effects of periodic sinusoidal riblet surfaces aligned in the flow direction (also known as a "wrinkled" texture) on the evolution of a laminar boundary layer flow. Using numerical analysis with the open source Computational Fluid Dynamics solver OpenFOAM, boundary layer flow over sinusoidal wrinkled plates with a range of wavelength to plate length ratios ( λ / L ), aspect ratios ( 2 A / λ ), and inlet velocities are examined. It is shown that in the laminar boundary layer regime, the riblets are able to retard the viscous flow inside the grooves creating a cushion of stagnant fluid that the high-speed fluid above can partially slide over, thus reducing the shear stress inside the grooves and the total integrated viscous drag force on the plate. Additionally, we explore how the boundary layer thickness, local average shear stress distribution, and total drag force on the wrinkled plate vary with the aspect ratio of the riblets as well as the length of the plate. We show that riblets with an aspect ratio of close to unity lead to the highest reduction in the total drag, and that because of the interplay between the local stress distribution on the plate and stream-wise evolution of the boundary layer the plate has to exceed a critical length to give a net decrease in the total drag force.

  17. Separations by centrifugal phenomena

    International Nuclear Information System (INIS)

    Hsu, H.W.

    1981-01-01

    The technical information presented herein emphasizes the uniqueness of the centrifugal separations methodology and pertinent theory for various kinds of centrifugation. The topics are arranged according to gas, liquid, and solid phases, in the order of increasing densities. Much space is devoted to liquid centrifugation because of the importance of this technique in chemical and biological laboratories. Many separational and characterizational examples are illustrated in detail. The material has been divided into 7 chapters entitled: 1) Introduction, 2) Basic Theory of Centrifugation, 3) Gas Centrifuges, 4) Preparative Liquid Centrifuges, 5) Analytical Liquid Centrifuges, 6) Liquid Centrifuges in Practice, and 7) Mechanical Separations by Centrifuges. Separate abstracts have been prepared for each chapter except the introduction

  18. Partially separable t matrix

    International Nuclear Information System (INIS)

    Sasakawa, T.; Okuno, H.; Ishikawa, S.; Sawada, T.

    1982-01-01

    The off-shell t matrix is expressed as a sum of one nonseparable and one separable terms so that it is useful for applications to more-than-two body problems. All poles are involved in this one separable term. Both the nonseparable and the separable terms of the kernel G 0 t are regular at the origin. The nonseparable term of this kernel vanishes at large distances, while the separable term behaves asymptotically as the spherical Hankel function. These properties make our expression free from defects inherent in the Jost or the K-matrix expressions, and many applications are anticipated. As the application, a compact expression of the many-level formula is presented. Also the application is suggested to the breakup threebody problem based on the Faddeev equation. It is demonstrated that the breakup amplitude is expressed in a simple and physically interesting form and we can calculate it in coordinate space

  19. Separation by solvent extraction

    International Nuclear Information System (INIS)

    Holt, C.H. Jr.

    1976-01-01

    In a process for separating fission product values from U and Pu values contained in an aqueous solution, an oxidizing agent is added to the solution to secure U and Pu in their hexavalent state. The aqueous solution is contacted with a substantially water-immiscible organic solvent with agitation while the temperature is maintained at from -1 to -2 0 C until the major part of the water present is frozen. The solid ice phase is continuously separated as it is formed and a remaining aqueous liquid phase containing fission product values and a solvent phase containing Pu and U values are separated from each other. The last obtained part of the ice phase is melted and added to the separated liquid phase. The resulting liquid is treated with a new supply of solvent whereby it is practically depleted of U and Pu

  20. CHROMATOGRAPHIC SEPARATION AND SPECTRO ...

    African Journals Online (AJOL)

    Four different fractions having colours yellow, grey, orange and ... Two different dyes vis a vis: methylene blue and malachite green dyes have been separated .... hydrogen carbonate of alkaline and alkaline earth metals in the samples.

  1. UWIS isotope separator

    Energy Technology Data Exchange (ETDEWEB)

    Wojtasiewicz, A. [Warsaw Univ., Inst. of Experimental Physics, Nuclear Physics Div., Warsaw (Poland)

    1997-12-31

    Since 1995 the University of Warsaw Isotope Separator group has participated in the ISOL/IGISOL project at the Heavy Ion Cyclotron. This project consists in installation of an isotope separator (on line with cyclotron heavy ion beam) with a hot plasma ion source (ISOL system) and/or with an ion guide source (IGISOL system). In the report the short description of the present status of the project is presented. 2 figs, 10 refs.

  2. Separating oil from water

    Energy Technology Data Exchange (ETDEWEB)

    Webb, C

    1991-04-11

    The technology available to deal with oil spills has assumed many new faces in recent years. Methods of dealing with small-scale pollution in the process industries and vast oil slicks such as that in the Gulf have developed in parallel. The progress being made in finding new means of separating oil from water is reported and the relative merits of bioremediation, hydrocylones, horizontal separators and gas flotation are discussed. (author).

  3. On separable Pauli equations

    International Nuclear Information System (INIS)

    Zhalij, Alexander

    2002-01-01

    We classify (1+3)-dimensional Pauli equations for a spin-(1/2) particle interacting with the electro-magnetic field, that are solvable by the method of separation of variables. As a result, we obtain the 11 classes of vector-potentials of the electro-magnetic field A(t,x(vector sign))=(A 0 (t,x(vector sign)), A(vector sign)(t,x(vector sign))) providing separability of the corresponding Pauli equations. It is established, in particular, that the necessary condition for the Pauli equation to be separable into second-order matrix ordinary differential equations is its equivalence to the system of two uncoupled Schroedinger equations. In addition, the magnetic field has to be independent of spatial variables. We prove that coordinate systems and the vector-potentials of the electro-magnetic field providing the separability of the corresponding Pauli equations coincide with those for the Schroedinger equations. Furthermore, an efficient algorithm for constructing all coordinate systems providing the separability of Pauli equation with a fixed vector-potential of the electro-magnetic field is developed. Finally, we describe all vector-potentials A(t,x(vector sign)) that (a) provide the separability of Pauli equation, (b) satisfy vacuum Maxwell equations without currents, and (c) describe non-zero magnetic field

  4. Diseño de un sistema de generación de chorro de agua de flujo laminar iluminado//Designing a system to generate water jet illuminated laminar flow

    Directory of Open Access Journals (Sweden)

    Néstor A. Ulloa-Auqui

    2015-09-01

    Full Text Available Se diseñó y fabricó exitosamente un Sistema de Generación de Chorro de Agua de Flujo Laminar Iluminado, el mismo tiene como finalidad desarrollar destrezas y capacidades en el laboratorio de fluidos cuando se realicen prácticas de variación de caudal para obtener diferentes alturas, alcances y observar como viajan las partículas de agua en un flujo laminar, fenómeno que se produce gracias a la iluminación de todo el chorro con la tecnología de la fibra óptica y un potenciador led RGB.  Los resultados obtenidos permiten realizar proyectos en el área de ornamentación que pueden ser utilizados de manera creativa en parques, hoteles, piscinas y piletas.  El estudio inicia con la determinación de las ecuaciones de cantidad de movimiento, balance de energía y movimiento parabólico que sirvieron para el cálculo hidráulico y selección de la bomba de caudal y boquilla del dispositivo. Palabras clave: flujo laminar, chorro de agua, fibra óptica, boquilla._____________________________________________________________________________AbstractA system to generate water jet illuminated laminar flow was successfully designed and fabricated, the same aims to develop skills and capabilities in the laboratory practices fluids when flow variation for different heights and ranges are made and watch the water particles traveling in laminar flow, phenomenon which occurs by lighting the whole jet technology with fiber optics and a RGB led enhancer.  The results obtained allow perform projects in the area of ornamentation, the same that can be used creatively in parks, hotels, swimming pools and fountains.  The study begins with the determination of the equations of momentum, energy balance and parabolic movement that served to the hydraulic calculation and selection of the pump flow and nozzle device. Key words: flow, laminar, waterjet, optical fiber, nozzle.

  5. Isotope separation apparatus and method

    International Nuclear Information System (INIS)

    Cotter, T.P.

    1982-01-01

    The invention relates to a method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferable substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. The laser beam comprises pi-pulses of a selected wavelength which excite unexcited molecules, or cause stimulated emission of excited molecules of one of the isotopes. Excitation caused by first direction pi-pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning pi-pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement is accomplished by a large number of pi-pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam

  6. Isotope separation apparatus and method

    International Nuclear Information System (INIS)

    Feldman, B. J.

    1985-01-01

    The invention relates to an improved method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferably substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. Because the molecules in the beam occupy various degenerate energy levels, if the laser beam comprises chirped pulses comprising selected wavelengths, the laser beam will very efficiently excite substantially all unexcited molecules and will cause stimulated emission of substantially all excited molecules of a selected one of the isotopes in the beam which such pulses encounter. Excitation caused by first direction chirped pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning chirped pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement of essentially all the molecules containing the one isotope is accomplished by a large number of chirped pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam

  7. Gas separation with membranes

    International Nuclear Information System (INIS)

    Schulz, G.; Michele, H.; Werner, U.

    1982-01-01

    Gas separation with membranes has already been tested in numerous fields of application, e.g. uranium enrichment of H 2 separation. In many of these processes the mass transfer units, so-called permeators, have to be connected in tandem in order to achieve high concentrations. A most economical operating method provides for each case an optimization of the cascades with regard to the membrane materials, construction and design of module. By utilization of the concentration gradient along the membrane a new process development has been accomplished - the continuously operating membrane rectification unit. Investment and operating costs can be reduced considerably for a number of separating processes by combining a membrane rectification unit with a conventional recycling cascade. However, the new procedure requires that the specifications for the module construction, flow design, and membrane properties be reconsidered. (orig.) [de

  8. Isotope separation process

    International Nuclear Information System (INIS)

    Lyon, R.K.

    1977-01-01

    The instant invention relates to a process for separating a material into two or more parts in each of which the abundances of the isotopes of a given element differ from the abundances of the isotopes of the same material in said material. More particularly, the invention relates to a method for the isotopically selective excitation of gas phase molecules by multiple infrared photon absorption followed by a step wherein more of the excited molecules than nonexcited molecules are converted to a chemically different form which may be separated by means known in the art. This invention is useful for, but not limited to, the separation of the principal isotopes of uranium. 15 claims, 1 figure

  9. Isotope separation process

    International Nuclear Information System (INIS)

    Thomas, W.R.L.

    1979-01-01

    The instant invention relates to an improved process for separating a material into two or more parts in each of which the abundances of the isotopes of a given element differ from the abundances of the isotopes of the same element in said material. More particularly, the invention relates to a method for the isotopically selective excitation of gas phase molecules by multiple infrared photon absorption followed by a step wherein more of the excited molecules than non-excited molecules are converted to a chemically different form which may be separated by means known in the art. This invention is useful for, but not limited to, the separation of the principal isotopes of uranium

  10. Separable quadratic stochastic operators

    International Nuclear Information System (INIS)

    Rozikov, U.A.; Nazir, S.

    2009-04-01

    We consider quadratic stochastic operators, which are separable as a product of two linear operators. Depending on properties of these linear operators we classify the set of the separable quadratic stochastic operators: first class of constant operators, second class of linear and third class of nonlinear (separable) quadratic stochastic operators. Since the properties of operators from the first and second classes are well known, we mainly study the properties of the operators of the third class. We describe some Lyapunov functions of the operators and apply them to study ω-limit sets of the trajectories generated by the operators. We also compare our results with known results of the theory of quadratic operators and give some open problems. (author)

  11. Immunoassay separation technique

    International Nuclear Information System (INIS)

    1977-01-01

    A method for effecting the immunoassay of a multiplicity of samples, each possibly containing an antigen or an antibody to be assayed, is discussed. Each sample is incubated with a solution containing a detectable antigen or antibody to form a multiplicity of mixtures, each mixture containing as components antigen-antibody, non-complexed antigen and non-complexed antibody. At least one of the components of the said mixture is separated by adsorption. There after, quantity of detectable antigen or antibody is detected in one of the non-adsorbed portions of the mixture. An improvement, compared to other techniques, is the continuous and sequential separation of at least one component, which is intended to be separated from each said multiplicity of mixtures

  12. Electromagnetic separator of plasma

    International Nuclear Information System (INIS)

    Gasilin, V.V.; Nezovibatko, Yu.N.; Poklepach, G.S.; Shvets, O.M.; Taran, V.S.; Tereshin, V.I.

    2005-01-01

    The progress in the widespread utilization of the PVD methods is determined in many respects by the plasma quality and, therefore, the necessity of an application of plasma separators, in particular magnetic separators. One needs to note that traditional magnetic separators have a number of problems their using, namely their unwieldiness, the presence of the isolated cameras and so on. We have proposed, manufactured and investigated the simple separator of plasma that doesn't require using additional cameras. As a source of metallic plasma the standard cathode vaporizer in the installation 'BULAT 6' was in use. Plasma stream from the cathode flowed through the not protected by isolation spiral solenoid. The solenoid input (from the cathode side) was under floating potential. The solenoid output was connected to the autonomous power supply system. The solenoid was prepared with stride winding and 90 degree turn. The solenoid current was 20-90 A and the solenoid voltage with respect to the vessel (earth) was +15 V. In this case drifting charged particles could freely fly out from the interior solenoid region to its boundary. The glow of the turned flow of plasma was observed during the supplying of the cathode and the solenoid. Plasma flow was separated from the coils and extended along the axis of solenoid. One can assume that this device ensures radial electric with respect to the bulk of plasma (the diameter of the bulk of plasma is comparable with the cathode diameter), the toroidal magnetic field, produced by solenoid, was of an order of 20 Oe. Magnetic field strength was sufficient for the magnetization of electrons, but it was rather small for magnetizing the ions and charged micro-droplets. The experiments carried out with aluminum cathode on the deposition of coatings at the stainless steel substrate have shown the high effectiveness of this separator operation. Coatings without droplets were obtained also on the glass substrate with HF- displacement

  13. Role of Myoendothelial Gap Junctions in the Regulation of Human Coronary Artery Smooth Muscle Cell Differentiation by Laminar Shear Stress

    Directory of Open Access Journals (Sweden)

    Zongqi Zhang

    2016-07-01

    Full Text Available Background/Aims: Smooth muscle cells may dedifferentiate into the synthetic phenotype and promote atherosclerosis. Here, we explored the role of myoendothelial gap junctions in phenotypic switching of human coronary artery smooth muscle cells (HCASMCs co-cultured with human coronary artery endothelial cells (HCAECs exposed to shear stress. Methods: HCASMCs and HCAECs were seeded on opposite sides of Transwell inserts, and HCAECs were exposed to laminar shear stress of 12 dyn/cm2 or 5 dyn/cm2. The myoendothelial gap junctions were evaluated by using a multi-photon microscope. Results: In co-culture with HCAECs, HCASMCs exhibited a contractile phenotype, and maintained the expression of differentiation markers MHC and H1-calponin. HCASMCs and HCAECs formed functional intercellular junctions, as evidenced by colocalization of connexin(Cx40 and Cx43 on cellular projections inside the Transwell membrane and biocytin transfer from HCAECs to HCASMCs. Cx40 siRNA and 18-α-GA attenuated protein expression of MHC and H1-calponin in HCASMCs. Shear stress of 5 dyn/cm2 increased Cx43 and decreased Cx40 expression in HCAECs, and partly inhibited biocytin transfer from HCAECs to HCASMCs, which could be completely blocked by Cx43 siRNA or restored by Cx40 DNA transfected into HCAECs. The exposure of HCAECs to shear stress of 5 dyn/cm2 promoted HCASMC phenotypic switching, manifested by morphological changes, decrease in MHC and H1-calponin expression, and increase in platelet-derived growth factor (PDGF-BB release, which was partly rescued by Cx43 siRNA or Cx40 DNA or PDGF receptor signaling inhibitor. Conclusions: The exposure of HCAECs to shear stress of 5 dyn/cm2 caused the dysfunction of Cx40/Cx43 heterotypic myoendothelial gap junctions, which may be replaced by homotypic Cx43/Cx43 channels, and induced HCASMC transition to the synthetic phenotype associated with the activation of PDGF receptor signaling, which may contribute to shear stress

  14. Unity Through Separation

    DEFF Research Database (Denmark)

    Dabelsteen, Hans B.

    This PhD thesis asks how we can conceptualize the current separation doctrine of religion and politics in a country like Denmark, where the structure of the established church and peoplehood overlap. In order to answer this question, Hans Bruun Dabelsteen maps the current discussion of secularism...... into the principle of treating everybody equally (with religious freedom, equality and Danish peoplehood as the most important principles adjacent to secularism). In a study of the historical roots of the separation doctrine and two current policy cases (same-sex marriage and reforms of church governance...

  15. Separation membrane development

    Energy Technology Data Exchange (ETDEWEB)

    Lee, M.W. [Savannah River Technology Center, Aiken, SC (United States)

    1998-08-01

    A ceramic membrane has been developed to separate hydrogen from other gases. The method used is a sol-gel process. A thin layer of dense ceramic material is coated on a coarse ceramic filter substrate. The pore size distribution in the thin layer is controlled by a densification of the coating materials by heat treatment. The membrane has been tested by permeation measurement of the hydrogen and other gases. Selectivity of the membrane has been achieved to separate hydrogen from carbon monoxide. The permeation rate of hydrogen through the ceramic membrane was about 20 times larger than Pd-Ag membrane.

  16. Gas separation membranes

    Science.gov (United States)

    Schell, William J.

    1979-01-01

    A dry, fabric supported, polymeric gas separation membrane, such as cellulose acetate, is prepared by casting a solution of the polymer onto a shrinkable fabric preferably formed of synthetic polymers such as polyester or polyamide filaments before washing, stretching or calendering (so called griege goods). The supported membrane is then subjected to gelling, annealing, and drying by solvent exchange. During the processing steps, both the fabric support and the membrane shrink a preselected, controlled amount which prevents curling, wrinkling or cracking of the membrane in flat form or when spirally wound into a gas separation element.

  17. Separation techniques: Chromatography

    Science.gov (United States)

    Coskun, Ozlem

    2016-01-01

    Chromatography is an important biophysical technique that enables the separation, identification, and purification of the components of a mixture for qualitative and quantitative analysis. Proteins can be purified based on characteristics such as size and shape, total charge, hydrophobic groups present on the surface, and binding capacity with the stationary phase. Four separation techniques based on molecular characteristics and interaction type use mechanisms of ion exchange, surface adsorption, partition, and size exclusion. Other chromatography techniques are based on the stationary bed, including column, thin layer, and paper chromatography. Column chromatography is one of the most common methods of protein purification. PMID:28058406

  18. Isotope separation process

    International Nuclear Information System (INIS)

    1976-01-01

    The invention relates to a process for separating a given material into two or more parts, in each of which the abundances of the isotopes of a given element differ from the abundances of the isotopes of the same material in the said material. More particularly, the invention relates to a method for the isotopically selective excitation of gas phase UF 6 by infrared photon absorption followed by selective reaction of said excited UF 6 with atomic chlorine, bromine, or iodine to form a product which may be separated by means known in the art

  19. SEPARATION PHENOMENA LOGISTIC REGRESSION

    Directory of Open Access Journals (Sweden)

    Ikaro Daniel de Carvalho Barreto

    2014-03-01

    Full Text Available This paper proposes an application of concepts about the maximum likelihood estimation of the binomial logistic regression model to the separation phenomena. It generates bias in the estimation and provides different interpretations of the estimates on the different statistical tests (Wald, Likelihood Ratio and Score and provides different estimates on the different iterative methods (Newton-Raphson and Fisher Score. It also presents an example that demonstrates the direct implications for the validation of the model and validation of variables, the implications for estimates of odds ratios and confidence intervals, generated from the Wald statistics. Furthermore, we present, briefly, the Firth correction to circumvent the phenomena of separation.

  20. Radiation gradient isotope separator

    International Nuclear Information System (INIS)

    Hughes, J.L.

    1980-01-01

    A system is described for transporting, separating and storing charged particles, charged antiparticles and fully or partially ionized isotopes of any element comprising a laser beam generator, laser beam intensity profiler, a laser beam variable intensity attenuator, and means for injecting charged particles, charged antiparticles and ionized isotopes into the beam and extracting them from the system as required. The invention is particularly useful for channelling electrons and ions used for fuel pellet compression in inertial fusion systems, for separating the isotopes of elements and for the confinement of charged antiparticles and particle/antiparticle plasmas

  1. Organic separations with membranes

    International Nuclear Information System (INIS)

    Funk, E.W.

    1993-01-01

    This paper presents an overview of present and emerging applications of membrane technology for the separation and purification of organic materials. This technology is highly relevant for programs aimed at minimizing waste in processing and in the treatment of gaseous and liquid effluents. Application of membranes for organic separation is growing rapidly in the petrochemical industry to simplify processing and in the treatment of effluents, and it is expected that this technology will be useful in numerous other industries including the processing of nuclear waste materials

  2. Isotope separation process

    International Nuclear Information System (INIS)

    Lyon, R.K.

    1976-01-01

    The instant invention relates to a process for separating a material into two or more parts in each of which the abundances of the isotopes of a given element differ from the abundances of the isotopes of the same material in said material. In one embodiment, the invention relates to a method for the isotopically selective excitation of gas phase molecules by multiple infrared photon absorption followed by selective dissociation of said excited molecules by the absorption of a single photon of visible or ultraviolet light. This invention is useful for, but not limited to, the separation of the principal isotopes of uranium. 11 Claims, 2 Drawing Figures

  3. Acromioclavicular joint separation

    Directory of Open Access Journals (Sweden)

    Devan Pandya, BS

    2018-04-01

    Full Text Available History of present illness: A 30-year-old male was brought in by ambulance to the emergency department as a trauma activation after a motorcycle accident. The patient was the helmeted rider of a motorcycle traveling at an unknown speed when he lost control and was thrown off his vehicle. He denied loss of consciousness, nausea, or vomiting. The patient’s vital signs were stable and his only complaint was pain around his left shoulder. On exam, the patient had a prominent left clavicle without skin compromise. He had adequate range of motion in the left shoulder with moderate pain, and his left upper extremity was neurovascularly intact. Significant findings: Plain films of the left shoulder showed elevation of the left clavicle above the acromion. There was an increase in the acromioclavicular (AC and coracoclavicular (CC distances (increased joint distances marked with red and blue arrows, respectively. A normal AC joint measures 1-3 mm whereas a normal CC distance measures 11-13 mm.1 The injury was classified as a Rockwood type III AC joint separation. Discussion: The AC joint is a synovial joint between an oval facet on the acromion and a similar facet on the distal end of the clavicle. Horizontal stability is provided by the AC joint while axial stability is provided by the CC joint.2,3 AC joint injuries account for about 9%-12% of shoulder girdle injuries, and the most common mechanism is direct trauma.4,5 Initial evaluation with imaging includes plain films with three views: the anterior-posterior (AP view with the shoulder in internal and external rotation as well as an axillary, or scapula-Y view (sensitivity 40%, specificity 90% for all films.6,7 AC joint injuries are classified by the Rockwood system.8 Type I involves a sprain or incomplete tear of the AC ligaments with an intact CC ligament. The AC joint appears normal on X-ray, but can become widened with stress, achieved by having the patient hold a 10-15 pound weight from each

  4. Non-equilibrium thermodynamics, heat transport and thermal waves in laminar and turbulent superfluid helium

    Science.gov (United States)

    Mongiovì, Maria Stella; Jou, David; Sciacca, Michele

    2018-01-01

    This review paper puts together some results concerning non equilibrium thermodynamics and heat transport properties of superfluid He II. A one-fluid extended model of superfluid helium, which considers heat flux as an additional independent variable, is presented, its microscopic bases are analyzed, and compared with the well known two-fluid model. In laminar situations, the fundamental fields are density, velocity, absolute temperature, and heat flux. Such a theory is able to describe the thermomechanical phenomena, the propagation of two sounds in liquid helium, and of fourth sound in superleak. It also leads in a natural way to a two-fluid model on purely macroscopical grounds and allows a small amount of entropy associated with the superfluid component. Other important features of liquid He II arise in rotating situations and in superfluid turbulence, both characterized by the presence of quantized vortices (thin vortex lines whose circulation is restricted by a quantum condition). Such vortices have a deep influence on the transport properties of superfluid helium, as they increase very much its thermal resistance. Thus, heat flux influences the vortices which, in turn, modify the heat flux. The dynamics of vortex lines is the central topic in turbulent superfluid helium. The model is generalized to take into account the vortices in different cases of physical interest: rotating superfluids, counterflow superfluid turbulence, combined counterflow and rotation, and mass flow in addition to heat flow. To do this, the averaged vortex line density per unit volume L, is introduced and its dynamical equations are considered. Linear and non-linear evolution equations for L are written for homogeneous and inhomogeneous, isotropic and anisotropic situations. Several physical experiments are analyzed and the influence of vortices on the effective thermal conductivity of turbulent superfluid helium is found. Transitions from laminar to turbulent flows, from diffusive to

  5. Laminar simulation of intersubchannel mixing in a triangular nuclear fuel bundle geometry

    International Nuclear Information System (INIS)

    Zaretsky, A.; Lightstone, M.F.; Tullis, S.

    2015-01-01

    Highlights: • Quasi-periodic flow was observed through rod-to-wall gaps. • Triangular subchannel flows were fundamentally irregular. • Cross-gap flow was influenced both by local and adjacent cross-gap intensity. • Phase-linking between gaps induced cross-plane peripheral circulation through rod–wall gaps. • Cross-gap flow structure was dependent on subchannel geometry. - Abstract: Predicting temperature distributions in fuel rod bundles is an important component of nuclear reactor safety analysis. Intersubchannel mixing acts to homogenize coolant temperatures thus reducing the likelihood of localized regions of high fuel temperature. Previous research has shown that intersubchannel mixing in nuclear fuel rod bundles is enhanced by a large-scale quasi-periodic energetic fluid motion, which transports fluid on the cross-plane between the narrow gaps connecting subchannels. This phenomenon has also been observed in laminar flows. Unsteady laminar flow simulations were performed in a simplified bundle of three rods with a pipe. Three similar geometries of varying gap width were examined, and a thermal trace was implemented on the first geometry. Thermal mixing was driven by the advection of energy between subchannels by the cross-plane flow. Flow through the rod-to-wall gaps in the wall subchannels alternated with a dominant frequency, particularly when rod-to-wall gaps were smaller than rod-to-rod gaps. Significant phase-linking between rod-to-wall gaps was also observed such that a peripheral circulation occurred through each gap simultaneously. Cross-plane flow through the rod-to-rod gaps in the triangular subchannel was irregular in each case. This was due to the fundamental irregularity of the triangular subchannel geometry. Vortices were continually broken up by cross-plane flow from other gaps due to the odd number of fluid pathways within the central subchannel. Cross-plane flow in subchannel geometries is highly interconnected between gaps. The

  6. Influence of thermal radiation on soot production in Laminar axisymmetric diffusion flames

    Science.gov (United States)

    Demarco, R.; Nmira, F.; Consalvi, J. L.

    2013-05-01

    The aim of this paper is to study the effect of radiative heat transfer on soot production in laminar axisymmetric diffusion flames. Twenty-four C1-C3 hydrocarbon-air flames, consisting of normal (NDF) and inverse (IDF) diffusion flames at both normal gravity (1 g) and microgravity (0 g), and covering a wide range of conditions affecting radiative heat transfer, were simulated. The numerical model is based on the Steady Laminar Flamelet (SLF) model, a semi-empirical two-equation acetylene/benzene based soot model and the Statistical Narrow Band Correlated K (SNBCK) model coupled to the Finite Volume Method (FVM) to compute thermal radiation. Predictions relative to velocity, temperature, soot volume fraction and radiative losses are on the whole in good agreement with the available experimental data. Model results show that, for all the flames considered, thermal radiation is a crucial process with a view to providing accurate predictions for temperatures and soot concentrations. It becomes increasingly significant from IDFs to NDFs and its influence is much greater as gravity is reduced. The radiative contribution of gas prevails in the weakly-sooting IDFs and in the methane and ethane NDFs, whereas soot radiation dominates in the other flames. However, both contributions are significant in all cases, with the exception of the 1 g IDFs investigated where soot radiation can be ignored. The optically-thin approximation (OTA) was also tested and found to be applicable as long as the optical thickness, based on flame radius and Planck mean absorption coefficient, is less than 0.05. The OTA is reasonable for the IDFs and for most of the 1 g NDFs, but it fails to predict the radiative heat transfer for the 0 g NDFs. The accuracy of radiative-property models was then assessed in the latter cases. Simulations show that the gray approximation can be applied to soot but not to combustion gases. Both the non-gray and gray soot versions of the Full Spectrum Correlated k (FSCK

  7. Damage detection in laminar thermoplastic composite materials by means of embedded optical fibers

    Directory of Open Access Journals (Sweden)

    Kojović Aleksandar M.

    2006-01-01

    Full Text Available This paper investigates the possibility of applying optical fibers as sensors for investigating low energy impact damage in laminar thermoplastic composite materials, in real time. Impact toughness testing by a Charpy impact pendulum with different loads was conducted in order to determine the method for comparative measurement of the resulting damage in the material. For that purpose intensity-based optical fibers were built in to specimens of composite materials with Kevlar 129 (the DuPont registered trade-mark for poly(p-phenylene terephthalamide woven fabric as reinforcement and thermoplastic PVB (poly(vinyl butyral as the matrix. In some specimens part of the layers of Kevlar was replaced with metal mesh (50% or 33% of the layers. Experimental testing was conducted in order to observe and analyze the response of the material under multiple low-energy impacts. Light from the light-emitting diode (LED was launched to the embedded optical fiber and was propagated to the phototransistor-based photo detector. During each impact, the signal level, which is proportional to the light intensity in the optical fiber, drops and then slowly recovers. The obtained signals were analyzed to determine the appropriate method for real time damage monitoring. The major part of the damage occurs during impact. The damage reflects as a local, temporary release of strain in the optical fiber and an increase of the signal level. The obtained results show that intensity-based optical fibers could be used for measuring the damage in laminar thermoplastic composite materials. The acquired optical fiber signals depend on the type of material, but the same set of rules (relatively different, depending on the type of material could be specified. Using real time measurement of the signal during impact and appropriate analysis enables quantitative evaluation of the impact damage in the material. Existing methods in most cases use just the intensity of the signal before

  8. Numerical study of laminar nonpremixed methane flames in coflow jets: Autoignited lifted flames with tribrachial edges and MILD combustion at elevated temperatures

    KAUST Repository

    M. Al-Noman, Saeed; Choi, Sang Kyu; Chung, Suk-Ho

    2016-01-01

    Autoignition characteristics of laminar nonpremixed methane jet flames in high-temperature coflow air are studied numerically. Several flame configurations are investigated by varying the initial temperature and fuel mole fraction. At a relatively

  9. Fathering After Marital Separation

    Science.gov (United States)

    Keshet, Harry Finkelstein; Rosenthal, Kristine M.

    1978-01-01

    Deals with experiences of a group of separated or divorced fathers who chose to remain fully involved in the upbringing of their children. As they underwent transition from married parenthood to single fatherhood, these men learned that meeting demands of child care contributed to personal stability and growth. (Author)

  10. Isotope separator laoratory development

    International Nuclear Information System (INIS)

    Anderl, R.A.

    1977-01-01

    Significant improvements in the capability for collection of mass-separated ions are described. These improvements centered on the fabrication and installation of a more versatile collection-beam viewing system and the design, fabrication, installation and testing of a retardation lens. A summary description of this capability development is presented

  11. Separation of Powers.

    Science.gov (United States)

    Bill of Rights in Action, 1987

    1987-01-01

    The dimensions of the separation of powers principle are explored through three lessons in the subject areas of U.S. history, U.S. government, and world history. In 1748, a French nobleman, Baron de Montesquieu, wrote a book called "The Spirit of the Laws," in which he argued that there could be no liberty when all government power was…

  12. Polymide gas separation membranes

    Science.gov (United States)

    Ding, Yong; Bikson, Benjamin; Nelson, Joyce Katz

    2004-09-14

    Soluble polyamic acid salt (PAAS) precursors comprised of tertiary and quaternary amines, ammonium cations, sulfonium cations, or phosphonium cations, are prepared and fabricated into membranes that are subsequently imidized and converted into rigid-rod polyimide articles, such as membranes with desirable gas separation properties. A method of enhancing solubility of PAAS polymers in alcohols is also disclosed.

  13. Industrial separation processes : fundamentals

    NARCIS (Netherlands)

    Haan, de A.B.; Bosch, Hans

    2013-01-01

    Separation processes on an industrial scale comprise well over half of the capital and operating costs. They are basic knowledge in every chemical engineering and process engineering study. This book provides comprehensive and fundamental knowledge of university teaching in this discipline,

  14. diffusive phase separation

    Directory of Open Access Journals (Sweden)

    Nobuyuki Kenmochi

    1996-01-01

    w is constrained to have double obstacles σ*≤w≤σ* (i.e., σ* and σ* are the threshold values of w. The objective of this paper is to discuss the semigroup {S(t} associated with the phase separation model, and construct its global attractor.

  15. Separation of uranium isotopes

    International Nuclear Information System (INIS)

    Ehrfeld, W.; Ehrfeld, U.

    1977-01-01

    In the nuclear fuel cycle, uranium enrichment is not a principal problem of technological feasibility. Several processes exist for producing LWR fuel and the enrichment method can be selected in consideration of economical, environmental, and political aspects. To date, the gaseous diffusion process constitutes the major part of enrichment capacity. This process has been well demonstrated for over 30 years and, as a matter of fact, no major technological and economical progress is to be expected in the future. Because of their comparatively high development potential, the centrifuge and the separation nozzle method may become increasingly favorable in economics. The development of the centrifuge process which is superior by its low specific energy consumption aims at technological improvements. In the separation nozzle process which offers the advantage of a comparatively simple technology a further reduction of the specific energy consumption is to be expected because of the thermodynamically favorable separation mechanism of this process. Laser isotope separation methods are still on the laboratory scale, although large financial funds have been spent. (orig.) [de

  16. Oily Bilgewater Separators

    Science.gov (United States)

    2011-11-01

    11 3.3.4 Flotation ...Flocculation, • Flotation , and • Ultrafiltration . EPA evaluated the effectiveness of bilge separators by their ability to achieve low effluent oil...parameters, suspended solids), metals (arsenic, copper , cadmium, chromium, lead, mercury, selenium and zinc) and organics (benzene, chloroform

  17. Separation problems and forcing

    Czech Academy of Sciences Publication Activity Database

    Zapletal, Jindřich

    2013-01-01

    Roč. 13, č. 1 (2013), s. 1350002 ISSN 0219-0613 R&D Projects: GA AV ČR IAA100190902 Institutional research plan: CEZ:AV0Z10190503 Keywords : separation * set of uniqueness * forcing Subject RIV: BA - General Mathematics Impact factor: 0.364, year: 2012 http://www.worldscientific.com/doi/abs/10.1142/S0219061313500025

  18. Radioactive krypton gas separation

    International Nuclear Information System (INIS)

    Martin, J.R.

    1976-01-01

    Radioactive krypton is separated from a gas mixture comprising nitrogen and traces of carbon dioxide and radioactive krypton by selective adsorption and then cryogenic distillation of the prepurified gas against nitrogen liquid to produce krypton bottoms concentrate liquid, using the nitrogen gas from the distillation for two step purging of the adsorbent. 16 Claims, 8 Drawing Figures

  19. Ruthenium cluster-like chalcogenide as a methanol tolerant cathode catalyst in air-breathing laminar flow fuel cells

    International Nuclear Information System (INIS)

    Whipple, Devin T.; Jayashree, Ranga S.; Egas, Daniela; Alonso-Vante, Nicolas; Kenis, Paul J.A.

    2009-01-01

    This paper reports the incorporation of a cluster-like Ru x Se y as a methanol tolerant cathode catalyst in a laminar flow fuel cell. The effect on cell performance of several concentrations of methanol in the cathode stream was investigated for the Ru x Se y catalyst and compared to a conventional platinum catalyst. While the Pt catalyst exhibited up to ∼80% drop in power density, the Ru x Se y catalyst showed no decrease in performance when the cathode was exposed to methanol. At several methanol concentrations the Ru x Se y catalyst performed better than the Pt catalyst. This demonstration of a methanol tolerant catalyst in a laminar flow fuel cell opens up the way for further miniaturization of the cell design and simplification of its operation as the need for an electrolyte stream to prevent fuel crossover has been eliminated.

  20. Fully developed laminar flow of non-Newtonian liquids through annuli: comparison of numerical calculations with experiments

    Energy Technology Data Exchange (ETDEWEB)

    Escudier, M.P.; Smith, S. [Department of Engineering, Mechanical Engineering, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom); Oliveira, P.J. [Departamento de Engenharia Electromecanica, Universidade da Beira Interior, Rua Marques D' Avila e Boloma, 6200 Covilha (Portugal); Pinho, F.T. [Centro de Estudos de Fenomenos de Transporte, DEMEGI, Faculdade de Engenharia, Universidade do Porto, Rua Roberto Frias, 4200-465 Porto (Portugal)

    2002-07-01

    Experimental data are reported for fully developed laminar flow of a shear-thinning liquid through both a concentric and an 80% eccentric annulus with and without centrebody rotation. The working fluid was an aqueous solution of 0.1% xanthan gum and 0.1% carboxymethylcellulose for which the flow curve is well represented by the Cross model. Comparisons are reported between numerical calculations and the flow data, as well as with other laminar annular-flow data for a variety of shear-thinning liquids previously reported in the literature. In general, the calculations are in good quantitative agreement with the experimental data, even in situations where viscoelastic effects, neglected in the calculations, would be expected to play a role. (orig.)