Modeling effective viscosity reduction behaviour of solid suspensions
Wei En-Bo; Ji Yan-Ju; Zhang Jun
2012-01-01
Under a simple shearing flow,the effective viscosity of solid suspensions can be reduced by controlling the inclusion particle size or the number of inclusion particles in a unit volume.Based on the Stokes equation,the transformation field method is used to model the reduction behaviour of effective viscosity of solid suspensions theoretically by enlarging the particle size at a given high concentration of particles.With a lot of samples of random cubic particles in a unit cell,our statistical results show that at the same higher concentration,the effective viscosity of solid suspensions can be reduced by increasing the particle size or reducing the number of inclusion particles in a unit volume.This work discloses the viscosity reduction mechanism of increasing particle size,which is observed experimentally.
Viscosity model of high-viscosity dispersing system
魏先福; 王娜; 黄蓓青; 孙承博
2008-01-01
High-viscosity dispersing system is formed by dispersing the solid particles in the high-viscosity continuous medium.It is very easy to form the three-dimensional network structure for solid particles in the system and the rheology behavior becomes complicated.The apparent viscosity of this dispersing system always has the connection with the volume ratio and the shear rate.In order to discuss the rheology behavior and put up the viscosity model,the suspension of silicon dioxide and silicon oil were prepared.Through testing the viscosity,the solid concentration and the shear rate,the effects of the ratio and the shear rate on viscosity was analyzed,the model of the high-viscosity dispersing system was designed and the model with the printing ink were validated.The experiment results show that the model is applicable to the high-viscosity dispersing systems.
Nakashima, Takako; Sako, Nobutomo; Matsuda, Takakuni; Uematsu, Naoya; Sakurai, Kazushi; Ishida, Tatsuhiro
2014-01-01
This study aimed at developing a novel rebamipide liquid for an effective treatment of oral mucositis. The healing effects of a variety of liquids comprising submicronized rebamipide crystals were investigated using a rat cauterization-induced oral ulcer model. Whereas 2% rebamipide liquid comprising micro-crystals did not exhibit significant curative effect, 2% rebamipide liquids comprising submicronized crystals with moderate viscosities exhibited healing effects following intra-oral administration. The 2% and 4% optimized rebamipide liquids showed significant healing effects in the rat oral ulcer model (prebamipide liquid significantly reduced the percent area of ulcerated injury (prebamipide liquid with moderate viscosity following intra-oral administration showed better both healing effect in the rat oral ulcer model and preventive effect in the rat irradiation-induced glossitis model.
The role of fat in flavor perception: effect of partition and viscosity in model emulsions.
Bayarri, Sara; Taylor, Andrew J; Hort, Joanne
2006-11-15
Decreasing the fat content of a food, while maintaining the same aroma content, changes both aroma release (due to partition effects) and the viscosity of the food. To understand the relative contribution of these two factors on flavor perception, a series of flavored emulsions were prepared to control aroma release and viscosity using different aroma, oil, and hydroxypropyl methyl cellulose (HPMC) contents. Samples were formulated to deliver the same aroma-release in vitro and in vivo, and their viscosity was measured using the Kokini oral shear stress parameter. Despite the in vivo aroma release being constant, there were perceptual differences between the samples, and the flavor intensity decreased as in-mouth viscosity increased. For these iso release samples, the Kokini oral shear stress parameter correlated well with the decrease in perception, suggesting that there may be a viscosity stimulus or that the viscosity affects release of tastant and hinders aroma-taste interactions.
Ahmada Omar Ali
2015-01-01
Full Text Available This paper investigates numerically the effects of variable viscosity on unsteady generalized Couette flow of a water base nanofluid with convective cooling at the moving surface. The Buongiorno model utilized for the nanofluid incorporates the effects of Brownian motion and thermophoresis. The nonlinear governing equations of continuity, momentum, energy and nanoparticles concentration are tackled numerically using a semi discretization finite difference method together with Runge-Kutta Fehlberg integration scheme. Numerical results for velocity, temperature, and nanoparticles concentration profiles together with skin friction and Nusselt number are obtained graphically and discussed quantitatively.
Viscosity model for aluminosilicate melt
Zhang G.H.
2012-01-01
Full Text Available The structurally based viscosity model proposed in our previous study is extended to include more components, e.g. SiO2, Al2O3, FeO, MnO, MgO, CaO, Na2O and K2O. A simple method is proposed to calculate the numbers of different types of oxygen ions classified by the different cations they bonded with, which is used to characterize the influence of composition on viscosity. When dealing with the aluminosilicate melts containing several basic oxides, the priority order is established for different cations for charge compensating Al3+ ions, according to the coulombic force between cation and oxygen anion. It is indicated that basic oxides have two paradox influences on viscosity: basic oxide with a higher basicity decreases viscosity more greatly by forming weaker non-bridging oxygen bond; while it increases viscosity more greatly by forming stronger bridging oxygen bond in tetrahedron after charge compensating Al3+ ion. The present model can extrapolate its application range to the system without SiO2. Furthermore, it could also give a satisfy interpretation to the abnormal phenomenon that viscosity increases when adding K2O to CaO-Al2O3-SiO2 melt within a certain composition range.
Effective Viscosity Coefficient of Nanosuspensions
Rudyak, V. Ya.; Belkin, A. A.; Egorov, V. V.
2008-12-01
Systematic calculations of the effective viscosity coefficient of nanosuspensions have been performed using the molecular dynamics method. It is established that the viscosity of a nanosuspension depends not only on the volume concentration of the nanoparticles but also on their mass and diameter. Differences from Einstein's relation are found even for nanosuspensions with a low particle concentration.
The effects of viscosity on circumplanetary disks
De-Fu Bu; Hsien Shang; Feng Yuan
2013-01-01
The effects of viscosity on the circumplanetary disks residing in the vicinity of protoplanets are investigated through two-dimensional hydrodynamical simulations with the shearing sheet model.We find that viscosity can considerably affect properties of the circumplanetary disk when the mass of the protoplanet Mp (＜) 33 M(⊙),where M(⊙) is the Earth's mass.However,effects of viscosity on the circumplanetary disk are negligibly small when the mass of the protoplanet Mp(＞) 33 M(⊙).We find that when Mp(＜) 33 M(⊙),viscosity can markedly disrupt the spiral structure of the gas around the planet and smoothly distribute the gas,which weakens the torques exerted on the protoplanet.Thus,viscosity can slow the migration speed of a protoplanet.After including viscosity,the size of the circumplanetary disk can be decreased by a factor of (＞) 20％.Viscosity helps to transport gas into the circumplanetary disk from the differentially rotating circumstellar disk.The mass of the circumplanetary disk can be increased by a factor of 50％ after viscosity is taken into account when Mp(＜) 33 M(⊙).Effects of viscosity on the formation of planets and satellites are briefly discussed.
Comparative analysis of CFD models for jetting fluidized beds: Effect of particle-phase viscosity
Pei Pei; Kai Zhang; Gang Xu; Yongping Yang; Dongsheng Wen
2012-01-01
Under the Eulerian-Eulerian framework of simulating gas-solid two-phase flow,the accuracy of the hydrodynamic prediction is strongly affected by the selection of rheology of the particulate phase,for which a detailed assessment is still absent.Using a jetting fluidized bed as an example,this work investigates the influence of solid theology on the hydrodynamic behavior by employing different particle-phase viscosity models.Both constant particle-phase viscosity model (CVM) with different viscosity values and a simple two-fluid model without particle-phase viscosity (NVM) are incorporated into the classical twofluid model and compared with the experimental measurements.Qualitative and quantitative results show that the jet penetration depth,jet frequency and averaged bed pressure drop are not a strong function of the particle-phase viscosity.Compared to CVM,the NVM exhibits better predictions on the jet behaviors,which is more suitable for investigating the hydrodynamics of gas-solid fluidized bed with a central jet.
ON THE EDDY VISCOSITY MODEL OF PERIODIC TURBULENT SHEAR FLOWS
王新军; 罗纪生; 周恒
2003-01-01
Physical argument shows that eddy viscosity is essentially different from molecular viscosity. By direct numerical simulation, it was shown that for periodic turbulent flows, there is phase difference between Reynolds stress and rate of strain. This finding posed great challenge to turbulence modeling, because most turbulence modeling, which use the idea of eddy viscosity, do not take this effect into account.
Pressure Effect on Extensional Viscosity
Christensen, Jens Horslund; Kjær, Erik Michael
1999-01-01
The primary object of these experiments was to investigate the influence of hydrostatic pressure on entrance flow. The effect of pressure on shear and extensional viscosity was evaluated using an axis symmetric capillary and a slit die where the hydrostatic pressure was raised with valves...
Effective viscosity of confined hydrocarbons
Sivebæk, Ion Marius; Samoilov, V.N.; Persson, B.N.J.
2012-01-01
We present molecular dynamics friction calculations for confined hydrocarbon films with molecular lengths from 20 to 1400 carbon atoms. We find that the logarithm of the effective viscosity ηeff for nanometer-thin films depends linearly on the logarithm of the shear rate: log ηeff=C-nlog γ̇, where...
Viscosity model for fully liquid silicate melt
Zhang Guo-Hua
2012-01-01
Full Text Available A model for estimating the viscosity of silicate melt as derived in our previous paper is extended to the system containing MgO, CaO, SrO, BaO, Li2O, Na2O, K2O, which can express the nonlinear variation of activation energy of viscosity with the composition. It is found that the optimized parameters of model which characterize the deforming ability of bonds around non-bridging oxygen decrease with increasing the bond strength of M-O bond expressed by I=2Q/RMz+ + rO2-2 (where Q is the valence of cation M; r is the radius. It is pointed out that viscosity is not only determined by the bond strength, but also by the radius of cation which is defined as the size effect. The radius of cation plays paradox roles in the two factors: smaller radius leads to a stronger bond, thus a higher viscosity; while cations with smaller radius are easier to diffuse when neglecting the interaction force, thus a lower viscosity will be.
Intrinsic viscosities of polyelectrolytes: determination and modeling of the effects of extra salt.
Eich, Andreas; Wolf, Bernhard A
2011-10-24
Based on early measurements of J. J. Hermans and co-workers (D. T. F. Pals, J. J. Hermans, Recl. Trav. Chim. Pays-Bas 1952, 71, 513-520; D. T. F. Pals, J. J. Hermans, J. Polym. Sci. 1950, 5, 733-734; D. T. F. Pals, J. J. Hermans, J. Polym. Sci. 1948, 3, 897-898), the present contribution demonstrates how primary data should be evaluated in order to obtain reliable intrinsic viscosities. This procedure yields detailed information on the changes of the intrinsic viscosities and of the corresponding viscometric interaction parameters caused by an increasing salinity of water. Both quantities decline from a maximum value in the pure solvent to a minimum value, which is approached in the limit of sufficiently high salt concentrations, and can be modeled quantitatively by means of a Boltzmann sigmoid. Particular attention is paid to the significance of results obtained by means of the method of isoionic dilution, proposed by J. J. Hermans and co-workers. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Bulk viscosity effects on ultrasonic thermoacoustic instability
Lin, Jeffrey; Scalo, Carlo; Hesselink, Lambertus
2016-11-01
We have carried out unstructured fully-compressible Navier-Stokes simulations of a minimal-unit traveling-wave ultrasonic thermoacoustic device in looped configuration. The model comprises a thermoacoustic stack with 85% porosity and a tapered area change to suppress the fundamental standing-wave mode. A bulk viscosity model, which accounts for vibrational and rotational molecular relaxation effects, is derived and implemented via direct modification of the viscous stress tensor, τij ≡ 2 μSij +λ/2 μ ∂uk/∂xk δij , where the bulk viscosity is defined by μb ≡ λ +2/3 μ . The effective bulk viscosity coefficient accurately captures acoustic absorption from low to high ultrasonic frequencies and matches experimental wave attenuation rates across five decades. Using pressure-based similitude, the model was downscaled from total length L = 2 . 58 m to 0 . 0258 m, corresponding to the frequency range f = 242 - 24200 Hz, revealing the effects of bulk viscosity and direct modification of the thermodynamic pressure. Simulations are carried out to limit cycle and exhibit growth rates consistent with linear stability analyses, based on Rott's theory.
The Friction Theory for Viscosity Modeling
Cisneros, Sergio; Zeberg-Mikkelsen, Claus Kjær; Stenby, Erling Halfdan
2001-01-01
In this work the one-parameter friction theory (f-theory) general models have been extended to the viscosity prediction and modeling of characterized oils. It is demonstrated that these simple models, which take advantage of the repulsive and attractive pressure terms of cubic equations of state...... such as the SRK, PR and PRSV, can provide accurate viscosity prediction and modeling of characterized oils. In the case of light reservoir oils, whose properties are close to those of normal alkanes, the one-parameter f-theory general models can predict the viscosity of these fluids with good accuracy. Yet......, in the case when experimental information is available a more accurate modeling can be obtained by means of a simple tuning procedure. A tuned f-theory general model can deliver highly accurate viscosity modeling above the saturation pressure and good prediction of the liquid-phase viscosity at pressures...
Effects of bulk viscosity on cosmological evolution
Pimentel, L O; Pimentel, L O; Diaz-Rivera, L M
1994-01-01
Abstract:The effect of bulk viscisity on the evolution of the homogeneous and isotropic cosmological models is considered. Solutions are found, with a barotropic equation of state, and a viscosity coefficient that is proportional to a power of the energy density of the universe. For flat space, power law expansions, related to extended inflation are found as well as exponential solutions, related to old inflation; also a solution with expansion that is an exponential of an exponential of the time is found.
A Study of Oil Viscosity Mental Model
Albaiti; Liliasari; Sumarna, Omay; Abdulkadir Martoprawiro, Muhamad
2017-02-01
There is no study regarding on how to learn viscosity of the liquid (e.g. oil) by interconnecting macroscopic, sub-microscopic and symbolic levels. Therefore, the purpose of this research was to study the mental model of the oil viscosity. Intermolecular attractive force of oil constituent on the sub-microscopic level is depicted in the form of mental models. In this research, the viscosity data for some types of oil was measured by using Hoppler method. Viscosity of mineral oil SAE 20W-50, mineral oil SAE 15W-40 and synthetic oil SAE 10W-40 were 1.75, 1.31, and 1.03 Pa s, and the densities of these oils were 908.64, 885.04, and 877.02 kg/m3, respectively. The results showed that the greater density of the mineral oil that is assumed to be composed of linear chains of hydrocarbons, the longer the chain of hydrocarbon linear. Consequently, there are stronger the London force and greater the oil viscosity. The density and viscosity of synthetic oil are lower than that of both mineral oils. Synthetic oil structurally forms polymers with large branching. This structure affects a lower synthetic oil viscosity. This study contributes to construct a mental model of pre-service chemistry teachers.
Singularities and Entropy in Bulk Viscosity Dark Energy Model
孟新河; 窦旭
2011-01-01
In this paper bulk viscosity is introduced to describe the effects of cosmic non-perfect fluid on the cosmos evolution and to build the unified dark energy （DE） with （dark） matter models. Also we derive a general relation between the bulk viscosity form and Hubble parameter that can provide a procedure for the viscosity DE model building. Especially, a redshift dependent viscosity parameter ζ ∝ λ0 ＋λ1（1 ＋z）n proposed in the previous work [X.H. Meng and X. Dou, Commun. Theor. Phys. B2 （2009） 377] is investigated extensively in this present work. Further more we use the recently released supernova dataset （the Constitution dataset） to constrain the model parameters. In order to differentiate the proposed concrete dark energy models from the well known ACDM model, statefinder diagnostic method is applied to this bulk viscosity model, as a complementary to the Om parameter diagnostic and the deceleration parameter analysis performed by us before. The DE model evolution behavior and tendency are shown in the plane of the statefinder diagnostic parameter pair {τ, s} as axes where the fixed point represents the A CDM model The possible singularity property in this bulk viscosity cosmology is also discussed to which we can conclude that in the different parameter regions chosen properly, this concrete viscosity DE model can have various late evolution behaviors and the late time singularity could be avoided. We also calculate the cosmic entropy in the bulk viscosity dark energy frame, and find that the total entropy in the viscosity DE model increases monotonously with respect to the scale factor evolution, thus this monotonous increasing property can indicate an arrow of time in the universe evolution, though the quantum version of the arrow of time is still very puzzling.
Effect of nuclear viscosity on fission process
Li Shidong; Kuang Huishun; Zhang Shufa; Xing Jingru; Zhuo Yizhong; Wu Xizhen; Feng Renfa
1989-02-01
According to the fission diffusion model, the deformation motion of fission nucleuses is regarded as a diffusion process of quasi-Brownian particles under fission potential. Through simulating such Brownian motion in two dimensional phase space by Monte-Carlo mehtod, the effect of nuclear visocity on Brownian particle diffusion is studied. Dynamical quanties, such as fission rate, kinetic energy distribution on scission, and soon are numerically calculated for various viscosity coefficients. The results are resonable in physics. This method can be easily extended to deal with multi-dimensional diffusion problems.
Bulk viscosity-driven suppression of shear viscosity effects on the flow harmonics at RHIC
Noronha-Hostler, J; Grassi, F
2014-01-01
The interplay between shear and bulk viscosities on the flow harmonics, $v_n$'s, at RHIC is investigated using the newly developed relativistic 2+1 hydrodynamical code v-USPhydro that includes bulk and shear viscosity effects both in the hydrodynamic evolution and also at freeze-out. While shear viscosity is known to attenuate the flow harmonics, we find that the inclusion of bulk viscosity decreases the shear viscosity-induced suppression of the flow harmonics bringing them closer to their values in ideal hydrodynamical calculations. Depending on the value of the bulk viscosity to entropy density ratio, $\\zeta/s$, in the quark-gluon plasma, the bulk viscosity-driven suppression of shear viscosity effects on the flow harmonics may require a re-evaluation of the previous estimates of the shear viscosity to entropy density ratio, $\\eta/s$, of the quark-gluon plasma previously extracted by comparing hydrodynamic calculations to heavy ion data.
Variable viscosity effects on mixed convection heat and mass ...
Variable viscosity effects on mixed convection heat and mass transfer along a ... PROMOTING ACCESS TO AFRICAN RESEARCH ... Keywords: Variable viscosity, Chemical Reaction, Viscous Dissipation, Finite difference method, Suction.
Shear Viscosity Coefficient from Microscopic Models
Muronga, A
2004-01-01
The transport coefficient of shear viscosity is studied for a hadron matter through microscopic transport model, the Ultra--relativistic Quantum Molecular Dynamics (UrQMD), using the Green--Kubo formulas. Molecular--dynamical simulations are performed for a system of light mesons in a box with periodic boundary conditions. Starting from an initial state composed of $\\pi, \\eta ,\\omega ,\\rho ,\\phi$ with a uniform phase--space distribution, the evolution takes place through elastic collisions, production and annihilation. The system approaches a stationary state of mesons and their resonances, which is characterized by common temperature. After equilibration, thermodynamic quantities such as the energy density, particle density, and pressure are calculated. From such an equilibrated state the shear viscosity coefficient is calculated from the fluctuations of stress tensor around equilibrium using Green--Kubo relations. We do our simulations here at zero net baryon density so that the equilibration times depend o...
Effect of Viscosity on Liquid Curtain Stability
Mohammad Karim, Alireza; Suszynski, Wieslaw; Francis, Lorraine; Carvalho, Marcio; Dow Chemical Company Collaboration; PUC Rio Collaboration; University of Minnesota, Twin Cities Collaboration
2016-11-01
The effect of viscosity on the stability of Newtonian liquid curtains was explored by high-speed visualization. Glycerol/water solutions with viscosity ranging from 19.1 to 210 mPa.s were used as coating liquids. The experimental set-up used a slide die delivery and steel tube edge guides. The velocity along curtain at different positions was measured by tracking small particles at different flow conditions. The measurements revealed that away from edge guides, velocity is well described by free fall effect. However, close to edge guides, liquid moves slower, revealing formation of a viscous boundary layer. The size of boundary layer and velocity near edge guides are strong function of viscosity. The critical condition was determined by examining flow rate below which curtain broke. Curtain failure was initiated by growth of a hole within liquid curtain, close to edge guides. Visualization results showed that the hole forms in a circular shape then becomes elliptical as it grows faster in vertical direction compared to horizontal direction. As viscosity rises, minimum flow rate for destabilization of curtain increased, indicating connection between interaction with edge guides and curtain stability. We would like to acknowledge the financial support from the Dow Chemical Company.
Glass viscosity calculation based on a global statistical modelling approach
Fluegel, Alex
2007-02-01
A global statistical glass viscosity model was developed for predicting the complete viscosity curve, based on more than 2200 composition-property data of silicate glasses from the scientific literature, including soda-lime-silica container and float glasses, TV panel glasses, borosilicate fiber wool and E type glasses, low expansion borosilicate glasses, glasses for nuclear waste vitrification, lead crystal glasses, binary alkali silicates, and various further compositions from over half a century. It is shown that within a measurement series from a specific laboratory the reported viscosity values are often over-estimated at higher temperatures due to alkali and boron oxide evaporation during the measurement and glass preparation, including data by Lakatos et al. (1972) and the recently published High temperature glass melt property database for process modeling by Seward et al. (2005). Similarly, in the glass transition range many experimental data of borosilicate glasses are reported too high due to phase separation effects. The developed global model corrects those errors. The model standard error was 9-17°C, with R^2 = 0.985-0.989. The prediction 95% confidence interval for glass in mass production largely depends on the glass composition of interest, the composition uncertainty, and the viscosity level. New insights in the mixed-alkali effect are provided.
Effective viscosity of magnetic nanofluids through capillaries.
Patel, Rajesh
2012-02-01
The simultaneous effect of magnetic field and temperature on the capillary viscosity of magnetic nanofluid is an important parameter for a new class of applications such as nanoduct flow, nanomotors, micro- and nanofluidic devices, for transformer cooling, magnetic targeted drug delivery, etc. The effective viscosity of a nanofluid is explained based on the rotation of the particles and the effect of torque on it due to an externally applied magnetic field. Two types of fluids are used here, temperature-sensitive and non-temperature-sensitive magnetic nanofluids. In both types of fluids, decrease in effective viscosity with temperature is observed, but in both cases the mechanism for the decrement is quite different. One is due to temperature dependence of the magnetic moment and the other is due to removal of the secondary surfactant. For temperature-sensitive magnetic nanofluids, a Curie temperature of ~80 °C is extracted from this study. For non-temperature-sensitive magnetic nanofluids ~65% of the secondary surfactant is removed for a change in temperature, ΔT = 40 °C. This is analogous with removal of a drug from magnetic particles for targeted drug delivery. Further, a linear dependence of effective viscosity with different capillary size and ξ (angle between magnetic field and flow direction, ξε[0,π/2]) is also observed. This linear dependence can also be a good approximation for the study of magnetic drug targeting, as in the human body the capillaries are of different sizes, and the externally applied magnetic field is not always parallel or perpendicular to the drug flow direction.
The Effects of Fluid Viscosity on the Orifice Rotameter
Jiang Wei
2016-04-01
Full Text Available Due to the viscous shear stress, there is an obvious error between the real flow rate and the rotameter indication for measuring viscous fluid medium. At 50 cSt the maximum error of DN40 orifice rotameter is up to 35 %. The fluid viscosity effects on the orifice rotameter are investigated using experimental and theoretical models. Wall jet and concentric annulus laminar theories were adapted to study the influence of viscosity. And a new formula is obtained for calculating the flow rate of viscous fluid. The experimental data were analyzed and compared with the calculated results. At high viscosity the maximum theoretical results error is 6.3 %, indicating that the proposed measurement model has very good applicability.
Dean vortex membrane microfiltration non-Newtonian viscosity effects
Schutyser, M.A.I.; Belfort, G.
2002-01-01
Many industrial feeds behave as non-Newtonian fluids, and little understanding exists as to their influence on cross-flow microfiltration (CMF) performance. The viscosity effects of a model non-Newtonian shear-thickening fluid were investigated in CMF with and without suspended silica particles in t
Dean vortex membrane microfiltration non-Newtonian viscosity effects
Schutyser, M.A.I.; Belfort, G.
2002-01-01
Many industrial feeds behave as non-Newtonian fluids, and little understanding exists as to their influence on cross-flow microfiltration (CMF) performance. The viscosity effects of a model non-Newtonian shear-thickening fluid were investigated in CMF with and without suspended silica particles in
The Effect of Exercise on Salivary Viscosity
Antoon J. M. Ligtenberg
2016-11-01
Full Text Available A common experience after exercise is the presence of a thick and sticky saliva layer on the oral surfaces, which causes a feeling of a dry mouth. Since the salivary mucin MUC5B is responsible for the visco-elastic behavior of saliva, in the present study we explored the effect of exercise on both the salivary viscosity and the secretion of MUC5B in saliva. Twenty healthy dental students performed an aerobic exercise by cycling for 15 min on cycle-ergometers at a heart rate of 130–140 beats per minute. Saliva was collected at three time points: before exercise, immediately after exercise and after 30 min recovery. Salivary flow rate, viscosity, amylase activity, total protein, carbohydrate and MUC5B concentration were determined. Salivary flow rate, protein and amylase did not change significantly. Immediately after exercise, the salivary viscosity and carbohydrate concentration were significantly higher than at baseline and after 30 min recovery. Immediately after exercise, the MUC5B concentration was significantly higher than after 30 min recovery. It is concluded that the presence of thick saliva after exercise is at least partially due to an increased secretion of MUC5B.
Modeling the viscosity of silicate melts containing manganese oxide
Kim Wan-Yi
2013-01-01
Full Text Available Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing manganese oxide. The model requires three pairs of adjustable parameters that describe the viscosities in three systems: pure MnO, MnO-SiO2 and MnO-Al2O3-SiO2. The viscosity of other ternary and multicomponent silicate melts containing MnO is then predicted by the model without any additional adjustable model parameters. Experimental viscosity data are reviewed for melts formed by MnO with SiO2, Al2O3, CaO, MgO, PbO, Na2O and K2O. The deviation of the available experimental data from the viscosities predicted by the model is shown to be within experimental error limits.
Mechanism of viscosity effect on magnetic island rotation
Mikhailovskii, A.B.; Konovalov, S.V. [Institute of Nuclear Fusion, Russian Research Centre ' Kurchatov Institute' , Kurchatov Sq., 1, Moscow (Russian Federation); Pustovitov, V.D. [National Inst. for Fusion Science, Toki, Gifu (Japan); Tsypin, V.S. [Institute of Physics, University of Sao Paulo, Rua do Matao, Travessa R, SP (Brazil)
2000-04-01
It is shown that plasma viscosity does not influence the magnetic island rotation directly. Nevertheless, it leads to nonstationarity of the plasma velocity. This nonstationarity is the reason of the viscosity effect on island rotation. (author)
Viscosity Formulations and the Effect of Uncertain Parameters
Wasiliev, J. M.
2015-12-01
The development of detailed models of the interior of the Earth and other terrestrial planets is frequently hampered by poorly constrained compositional parameters, namely Activation Energy and Volume, which are necessary to define Arrhenius viscosity. This results in the values of said parameters varying considerably to suit the needs of individual investigations. A computational exploration of the effects of Activation Energy and Volume on the Earth's mantle was thus conducted, with a view to developing a robust and versatile method for obtaining a first-degree approximation for the parameter values, and providing some context for future studies. A wide range of plausible mantle configurations was examined in both one and two dimensions, with the latter case utilising the modelling program ASPECT to generate a series of simple Earth-like planets which were allowed to evolve until a steady state was achieved. A comprehensive statistical analysis was then performed, allowing for suitable parameter values to be more effectively constrained for numerous given viscosity formulations. Activation Energy was seen to exhibit considerable influence over the bulk magnitude of viscosity values, while Activation Volume heavily impacted the viscosity contrast between the upper and lower mantle. This behaviour stems from the parameters controlling the temperature and pressure dependency of viscosity within the calculation. Results were found to be highly dependent on the minimum and maximum values imposed on the viscosity, reinforcing the need for a fuller understanding of the formulation. A notable impact on stress profiles, and hence tectonic regime, was also observed. As such similar calculations were performed on directly scaled Super-Earths, with the intention of providing some insight into scenarios conducive to particular tectonic regimes in planets outside our solar system.
Nonlinear Eddy Viscosity Models applied to Wind Turbine Wakes
Laan, van der, Paul Maarten; Sørensen, Niels N.; Réthoré, Pierre-Elouan;
2013-01-01
The linear k−ε eddy viscosity model and modified versions of two existing nonlinear eddy viscosity models are applied to single wind turbine wake simulations using a Reynolds Averaged Navier-Stokes code. Results are compared with field wake measurements. The nonlinear models give better results...
Modelling droplet collision outcomes for different substances and viscosities
Sommerfeld, Martin; Kuschel, Matthias
2016-12-01
The main objective of the present study is the derivation of models describing the outcome of binary droplet collisions for a wide range of dynamic viscosities in the well-known collision maps (i.e. normalised lateral droplet displacement at collision, called impact parameter, versus collision Weber number). Previous studies by Kuschel and Sommerfeld (Exp Fluids 54:1440, 2013) for different solution droplets having a range of solids contents and hence dynamic viscosities (here between 1 and 60 mPa s) revealed that the locations of the triple point (i.e. coincidence of bouncing, stretching separation and coalescence) and the critical Weber number (i.e. condition for the transition from coalescence to separation for head-on collisions) show a clear dependence on dynamic viscosity. In order to extend these findings also to pure liquids and to provide a broader data basis for modelling the viscosity effect, additional binary collision experiments were conducted for different alcohols (viscosity range 1.2-15.9 mPa s) and the FVA1 reference oil at different temperatures (viscosity range 3.0-28.2 mPa s). The droplet size for the series of alcohols was around 365 and 385 µm for the FVA1 reference oil, in each case with fixed diameter ratio at Δ= 1. The relative velocity between the droplets was varied in the range 0.5-3.5 m/s, yielding maximum Weber numbers of around 180. Individual binary droplet collisions with defined conditions were generated by two droplet chains each produced by vibrating orifice droplet generators. For recording droplet motion and the binary collision process with good spatial and temporal resolution high-speed shadow imaging was employed. The results for varied relative velocity and impact angle were assembled in impact parameter-Weber number maps. With increasing dynamic viscosity a characteristic displacement of the regimes for the different collision scenarios was also observed for pure liquids similar to that observed for solutions. This
Mathematical Models For Calculating The Value Of Dynamic Viscosity Of A Liquid
Ślęzak M.
2015-06-01
Full Text Available The objective of this article is to review models for calculating the value of liquid dynamic viscosity. Issues of viscosity and rheological properties of liquid ferrous solutions are important from the perspective of modelling, along with the control of actual production processes related to the manufacturing of metals, including iron and steel. Conducted analysis within literature indicates that there are many theoretical considerations concerning the effect of viscosity of liquid metals solutions. The vast majority of models constitute a group of theoretical or semi-empirical equations, where thermodynamic parameters of solutions, or some parameters determined by experimental methods, are used for calculations of the dynamic viscosity coefficient.
Investigating the effect of lateral viscosity variations in the Earth's mantle
O'Farrell, K. A.; Lithgow-Bertelloni, C. R.
2015-12-01
Seismic tomography can be used to investigate radial viscosity variations on instantaneous flow models by predicting the global geoid and comparing with the observed geoid. This method is one of many that has been used to constrain viscosity structure in the Earth's mantle in the last few decades. Using the 3D mantle convection model, Stag-YY (e.g., Hernlund and Tackley, 2008), we are further able to explore the effect of lateral variations in viscosity in addition to the radial variations. Examining over 50 tomographic models we found notable differences by comparing a synthetically produced geoid with the observed geoid. Comparing S- and P-wave tomographic models, the S-wave models provided a better fit to the observed geoid. Using this large suite of 50 tomographic models, we have been able to constrain the radial viscosity structure of the Earth. We found that two types of viscosity profiles yielded equally good fits. A viscosity profile with a low transition zone viscosity and a lower mantle viscosity equal to the upper mantle, or a profile with a large lower mantle viscosity and a transition zone viscosity similar to the upper mantle. Using the set of radial viscosity profiles that gave the best fit to the observed geoid, we can explore a range of lateral viscosity variations and see how they affect the different types of tomographic models. Improving on previous studies of lateral viscosity variations (e.g. Ghosh, Becker and Zhong, 2010), we systematically explore a large range of tomographic models and density-velocity conversion factors. We explore which type of tomographic model (S- or P- wave) is more strongly affected by lateral viscosity variations, as well as the effect on isotropic and anisotropic models. We constrain the strength of lateral viscosity variations necessary to produce a high correlation between observed and predicted geoid anomalies. We will discuss the wavelength of flow that is most affected by the lateral viscosity variations
Unification of viscose models for powder suspension system
梁叔全; 李伟洲; 黄伯云
2002-01-01
The viscose models for powder suspension system was reviewed and analysed. It is found that by introducing modification function f(φ) in the differential form of classical Einsteins viscosity law, all of viscose models can be unified if f(φ) takes suitable form . Some rational forms of the function f(φ) were discussed according to functional approximation method, and a new rheological model contained two undetermined parameters was consequently developed, more suitable for high particle concentration dispersing system. The experimental results show that this new model is of better consistence.
Modeling of the eddy viscosity by breaking waves
无
2007-01-01
Breaking wave induced nearsurface turbulence has important consequences for many physical and biochemical processes including water column and nutrients mixing, heat and gases exchange across air-sea interface. The energy loss from wave breaking and the bubble plume penetration depth are estimated. As a consequence, the vertical distribution of the turbulent kinetic energy (TKE), the TKE dissipation rate and the eddy viscosity induced by wave breaking are also provided. It is indicated that model results are found to be consistent with the observational evidence that most TKE generated by wave breaking is lost within a depth of a few meters near the sea surface. High turbulence level with intensities of eddy viscosity induced by breaking is nearly four orders larger than υwl(=κu *wz), the value predicted for the wall layer scaling close to the surface, where u *w is the friction velocity in water, κ with 0.4 is the von Kármán constant, and z is the water depth, and the strength of the eddy viscosity depends both on wind speed and sea state, and decays rapidly through the depth. This leads to the conclusion that the breaking wave induced vertical mixing is mainly limited to the near surface layer, well above the classical values expected from the similarity theory. Deeper down, however, the effects of wave breaking on the vertical mixing become less important.
Modeling the viscosity of polydisperse suspensions: Improvements in prediction of limiting behavior
Mwasame, Paul M.; Wagner, Norman J.; Beris, Antony N.
2016-06-01
The present study develops a fully consistent extension of the approach pioneered by Farris ["Prediction of the viscosity of multimodal suspensions from unimodal viscosity data," Trans. Soc. Rheol. 12, 281-301 (1968)] to describe the viscosity of polydisperse suspensions significantly improving upon our previous model [P. M. Mwasame, N. J. Wagner, and A. N. Beris, "Modeling the effects of polydispersity on the viscosity of noncolloidal hard sphere suspensions," J. Rheol. 60, 225-240 (2016)]. The new model captures the Farris limit of large size differences between consecutive particle size classes in a suspension. Moreover, the new model includes a further generalization that enables its application to real, complex suspensions that deviate from ideal non-colloidal suspension behavior. The capability of the new model to predict the viscosity of complex suspensions is illustrated by comparison against experimental data.
The viscosity of planetary tholeiitic melts: A configurational entropy model
Sehlke, Alexander; Whittington, Alan G.
2016-10-01
The viscosity (η) of silicate melts is a fundamental physical property controlling mass transfer in magmatic systems. Viscosity can span many orders of magnitude, strongly depending on temperature and composition. Several models are available that describe this dependency for terrestrial melts quite well. Planetary basaltic lavas however are distinctly different in composition, being dominantly alkali-poor, iron-rich and/or highly magnesian. We measured the viscosity of 20 anhydrous tholeiitic melts, of which 15 represent known or estimated surface compositions of Mars, Mercury, the Moon, Io and Vesta, by concentric cylinder and parallel plate viscometry. The planetary basalts span a viscosity range of 2 orders of magnitude at liquidus temperatures and 4 orders of magnitude near the glass transition, and can be more or less viscous than terrestrial lavas. We find that current models under- and overestimate superliquidus viscosities by up to 2 orders of magnitude for these compositions, and deviate even more strongly from measured viscosities toward the glass transition. We used the Adam-Gibbs theory (A-G) to relate viscosity (η) to absolute temperature (T) and the configurational entropy of the system at that temperature (Sconf), which is in the form of log η =Ae +Be /TSconf . Heat capacities (CP) for glasses and liquids of our investigated compositions were calculated via available literature models. We show that the A-G theory is applicable to model the viscosity of individual complex tholeiitic melts containing 10 or more major oxides as well or better than the commonly used empirical equations. We successfully modeled the global viscosity data set using a constant Ae of -3.34 ± 0.22 log units and 12 adjustable sub-parameters, which capture the compositional and temperature dependence on melt viscosity. Seven sub-parameters account for the compositional dependence of Be and 5 for Sconf. Our model reproduces the 496 measured viscosity data points with a 1
Gas distribution effects on waste properties: Viscosities of bubbly slurries
Gauglitz, P.A.; Shah, R.R.; Davis, R.L.
1994-09-01
The retention and episodic release of flammable gases are critical safety concerns for double-shell tanks that contain waste slurries. The rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles. The presence of gas bubbles is expected to affect the rheology of the sludge, but essentially no literature data are available to assess the effect of bubbles. Accordingly, the objectives of this study are to develop models for the effect of gas bubbles on the viscosity of a particulate slurry, develop an experimental method (capillary rheometer), collect data on the viscosity of a bubbly slurry, and develop a theoretical basis for interpreting the experimental data from the capillary rheometer.
EFFECT OF ADSORPTION ON THE VISCOSITY OF DILUTE POLYMER SOLUTION
Rong-shi Cheng; Yu-fang Shao; Ming-zhu Liu; Rong-qing Lu
1999-01-01
Careful measurements of the dilute solution viscosities of polyethylene glycol and polyvinyl alcohol in water were carried out. The reduced viscosities of both polymer solutions plot upward curves at extremely dilute concentration levels similar to the phenomena observed for many polymer solutions in the early 1950's. Upon observation of the changes of the flow times of pure water in and the wall surface wettability of the viscometer after measuring solution viscosity, a view was formed that the observed viscosity abnormality at extremely dilute concentration regions is solely due to the effect of adsorption of polymer chains onto the wall surface of viscometer. A theory of adsorption effect based on the Langmuir isotherms was proposed and a mathematical analysis for data treatment was performed. The theory could adequately describe the existing viscosity data. It seems necessary to correct the viscosity result of dilute polymer solutions measured by glass capillary viscometer by taking into account the effect of adsorption in all cases.
Effects of Liquid Second Viscosity in High-Amplitude Sonoluminescence
Ahmad Moshaii; Rasool Sadighi-Bonabi; Mohammad Taeibi-Rahni; Mehdi Daemi
2004-01-01
@@ The well-known Rayleigh-Plesset (RP) equation is the base of nearly all hydrodynamical descriptions of the sonoluminescence phenomenon. A major deficiency of this equation is that it accounts for viscosity of an incompressible liquid and compressibility, separately. By removing this approximation, we have modified the RP equation, considering effects of liquid second viscosity. This modification exhibits its importance at the end of an intense collapse, so that the new model predicts the appearance of a new picosecond bouncing during highamplitude sonoluminescence radiation. This new bouncing produces very sharp (sub-picosecond) peaks on the top of the sonoluminescence pulse. These new behaviours are more remarkable for higher driving pressures and lower ambient temperatures.
Randall-Sundrum model with {lambda}<0 and bulk brane viscosity
Lepe, Samuel [Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Casilla 4950, Valparaiso (Chile); Pena, Francisco [Departamento de Ciencias Fisicas, Facultad de Ingenieria, Ciencias y Administracion, Universidad de la Frontera, Avda. Francisco Salazar 01145, Casilla 54-D, Temuco (Chile); Saavedra, Joel [Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Casilla 4950, Valparaiso (Chile)], E-mail: joel.saavedra@ucv.cl
2008-04-17
We study the effect of the inclusion of bulk brane viscosity on brane world (BW) cosmology in the framework of the Eckart's theory, we focus in the Randall-Sundrum model with negative tension on the brane.
On the micropolar flow in a circular pipe: the effects of the viscosity coefficients
无
2011-01-01
This paper considers the stationary flow of incompressible micropolar fluid through a thin cylindrical pipe governed by the pressure drop between pipe's ends. Its goal is to investigate the influence of the viscosity coefficients on the effective flow. Depending on the magnitude of viscosity coefficients with respect to the pipe's thickness, it derives different asymptotic models and discusses their properties.
Chebyshev super spectral viscosity method for a fluidized bed model
Sarra, S A
2003-01-01
A Chebyshev super spectral viscosity method and operator splitting are used to solve a hyperbolic system of conservation laws with a source term modeling a fluidized bed. The fluidized bed displays a slugging behavior which corresponds to shocks in the solution. A modified Gegenbauer postprocessing procedure is used to obtain a solution which is free of oscillations caused by the Gibbs-Wilbraham phenomenon in the spectral viscosity solution. Conservation is maintained by working with unphysical negative particle concentrations.
A memory-based model for blood viscosity
Ionescu, Clara M.
2017-04-01
This paper presents a comparison between existing models for non-Newtonian fluid viscosity as a function of shear rate variations. A novel model is introduced whose parameters are linked to physiological phenomena in the blood. The end use of such models is to predict changes in viscosity to adapt the speed of a nanorobot device for targeted drug delivery purposes. Simulation results show the agreement between the proposed model and available models from literature. A laboratory scale validation of the proposed model for a fluid mimicking non-Newtonian properties has been performed. Conceptual perspectives are also given in this work.
RECENT PROGRESS IN NONLINEAR EDDY-VISCOSITY TURBULENCE MODELING
符松; 郭阳; 钱炜祺; 王辰
2003-01-01
This article presents recent progresses in turbulence modeling in the Unit for Turbulence Simulation in the Department of Engineering Mechanics at Tsinghua University. The main contents include: compact Non-Linear Eddy-Viscosity Model (NLEVM) based on the second-moment closure, near-wall low-Re non-linear eddy-viscosity model and curvature sensitive turbulence model.The models have been validated in a wide range of complex flow test cases and the calculated results show that the present models exhibited overall good performance.
Effect of viscosity on appetite and gastro-intestinal hormones
Zijlstra, N.; Mars, M.; Wijk, de R.A.; Westerterp-Plantenga, M.S.; Holst, J.J.; Graaf, de C.
2009-01-01
In previous studies we showed that higher viscosity resulted in lower ad libitum intake and that eating rate is an important factor. In this study we aimed to explore the effect of viscosity on the gastro-intestinal hormones ghrelin, CCK-8 and GLP-1. Thirty-two subjects (22 ± 2 y, BMI 21.9 ± 2.2 kg/
Effect of viscosity on appetite and gastro-intestinal hormones
Zijlstra, N.; Mars, M.; Wijk, de R.A.; Westerterp-Plantenga, M.S.; Holst, J.J.; Graaf, de C.
2009-01-01
In previous studies we showed that higher viscosity resulted in lower ad libitum intake and that eating rate is an important factor. In this study we aimed to explore the effect of viscosity on the gastro-intestinal hormones ghrelin, CCK-8 and GLP-1. Thirty-two subjects (22 ± 2 y, BMI 21.9 ± 2.2 kg/
Universe Models with Negative Bulk Viscosity
Brevik, Iver
2013-01-01
The concept of negative temperatures has occasionally been used in connection with quantum systems. A recent example of this sort is reported in the paper of S. Braun et al. [Science 339,52 (2013)], where an attractively interacting ensemble of ultracold atoms is investigated experimentally and found to correspond to a negative-temperature system since the entropy decreases with increasing energy at the high end of the energy spectrum. As the authors suggest, it would be of interest to investigate whether a suitable generalization of standard cosmological theory could be helpful, in order to elucidate the observed accelerated expansion of the universe usually explained in terms of a positive tensile stress (negative pressure). In the present note we take up this basic idea and investigate a generalization of the standard viscous cosmological theory, not by admitting negative temperatures but instead by letting the bulk viscosity take negative values. Evidently, such an approach breaks standard thermodynamics,...
Commensurability Effects in Viscosity of Nanoconfined Water.
Neek-Amal, Mehdi; Peeters, Francois M; Grigorieva, Irina V; Geim, Andre K
2016-03-22
The rate of water flow through hydrophobic nanocapillaries is greatly enhanced as compared to that expected from macroscopic hydrodynamics. This phenomenon is usually described in terms of a relatively large slip length, which is in turn defined by such microscopic properties as the friction between water and capillary surfaces and the viscosity of water. We show that the viscosity of water and, therefore, its flow rate are profoundly affected by the layered structure of confined water if the capillary size becomes less than 2 nm. To this end, we study the structure and dynamics of water confined between two parallel graphene layers using equilibrium molecular dynamics simulations. We find that the shear viscosity is not only greatly enhanced for subnanometer capillaries, but also exhibits large oscillations that originate from commensurability between the capillary size and the size of water molecules. Such oscillating behavior of viscosity and, consequently, the slip length should be taken into account in designing and studying graphene-based and similar membranes for desalination and filtration.
Unraveling viscosity effects on the hysteresis losses of magnetic nanocubes.
Cabrera, D; Lak, A; Yoshida, T; Materia, M E; Ortega, D; Ludwig, F; Guardia, P; Sathya, A; Pellegrino, T; Teran, F J
2017-04-20
Hysteresis losses in magnetic nanoparticles constitute the basis of magnetic hyperthermia for delivering a local thermal stress. Nevertheless, this therapeutic modality is only to be realised through a careful appraisal of the best possible intrinsic and extrinsic conditions to the nanoparticles for which they maximise and preserve their heating capabilities. Low frequency (100 kHz) hysteresis loops accurately probe the dynamical magnetic response of magnetic nanoparticles in a more reliable manner than calorimetry measurements, providing conclusive quantitative data under different experimental conditions. We consider here a set of iron oxide or cobalt ferrite nanocubes of different sizes, through which we experimentally and theoretically study the influence of the viscosity of the medium on the low frequency hysteresis loops of magnetic colloids, and hence their ability to produce and dissipate heat to the surroundings. We analyse the role of nanoparticle size, size distribution, chemical composition, and field intensity in making the magnetisation dynamics sensitive to viscosity. Numerical simulations using the stochastic Landau-Lifshitz-Gilbert equation model the experimental observations in excellent agreement. These results represent an important contribution towards predicting viscosity effects and hence to maximise heat dissipation from magnetic nanoparticles regardless of the environment.
Mathematical Viscosity Models for Ternary Metallic and Silicate Melts
FU Yuan-kun; MENG Xian-min; GUO Han-jie
2004-01-01
The mathematical viscosity models for metallic melts were discussed. The experimental data of Ag-Au-Cu systems were used to verify the models based on Chou's general geometric thermodynamic model and the calculated results are consistent with the reported experimental data. A new model predicting the viscosity of multi-component silicate melts was established. The CaO-MnO-SiO2, CaO-FeO-SiO2 and FeO-MnO-SiO2 silicate slag systems were used to verify the model.
A synthesis of similarity and eddy-viscosity models
Verstappen, R.; Friedrich, R; Geurts, BJ; Metais, O
2004-01-01
In large-eddy simulation, a low-pass spatial filter is usually applied to the Navier-Stokes equations. The resulting commutator of the filter and the nonlinear term is usually modelled by an eddy-viscosity model, by a similarity model or by a mix thereof. Similarity models possess the proper mathema
MODELING A SOLID BOUNDARY AS A FLUID OF INFINITE VISCOSITY
无
2000-01-01
A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundary but still yields a finite value for the shear stress at the solid wall. Basic objective of this research is to show that certain combinations of higher order normal velocity gradients become zero at the solid boundary.Modified solutions for the Couette flow and Poiseuille flow between two parallel plates are obtained by modeling the coefficient of viscosity in a novel way. Also,viscous drag computed by our model is expected to yield higher values than the values predicted by the existing models, which matches closely to the experimental data.
Bianchi Type Ⅲ String Cosmological Model with Bulk Viscosity
WANGXing-Xiang
2004-01-01
The Bianchi type Ⅲ cosmological model for a cloud string with bulk viscosity are presented. To obtain a determinate model, an equation of state ρ=kλ and a relation between metric potentials B = Cn are assumed. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start, and the relation between the coefficient of bulk viscosity and the energy density is ζ∝ρ1/2.
Bianchi Type Ⅲ String Cosmological Model with Bulk Viscosity
WANG Xing-Xiang
2004-01-01
The Bianchi type Ⅲ cosmological model for a cloud string with bulk viscosity are presented. To obtaina determinate model, an equation of state p = κλ and a relation between metric potentials B = Cn are assumed. Thephysical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuouslyexpanding universe with a big-bang start, and the relation between the coefficient of bulk viscosity and the energy densityis ζ∝1 p1/2.
Viscosity effects in wind wave generation
Paquier, Anna; Rabaud, Marc
2016-01-01
We investigate experimentally the influence of the liquid viscosity on the problem of the generation of waves by a turbulent wind at the surface of a liquid, extending the results of Paquier, Moisy and Rabaud [Phys. Fluids {\\bf 27}, 122103 (2015)] over nearly three decades of viscosity. The surface deformations are measured with micrometer accuracy using the Free-Surface Synthetic Schlieren method. We recover the two regimes of surface deformations previously identified: the wrinkles regime at small wind velocity, resulting from the viscous imprint on the liquid surface of the turbulent fluctuations in the boundary layer, and the regular wave regime at large wind velocity. Below the wave threshold, we find that the characteristic amplitude of the wrinkles scales as $\
Measuring Solution Viscosity and its Effect on Enzyme Activity
Uribe Salvador
2003-01-01
Full Text Available In proteins, some processes require conformational changes involving structural domain diffusion. Among these processes are protein folding, unfolding and enzyme catalysis. During catalysis some enzymes undergo large conformational changes as they progress through the catalytic cycle. According to Kramers theory, solvent viscosity results in friction against proteins in solution, and this should result in decreased motion, inhibiting catalysis in motile enzymes. Solution viscosity was increased by adding increasing concentrations of glycerol, sucrose and trehalose, resulting in a decrease in the reaction rate of the H+-ATPase from the plasma membrane of Kluyveromyces lactis. A direct correlation was found between viscosity (&eegr; and the inhibition of the maximum rate of catalysis (V max. The protocol used to measure viscosity by means of a falling ball type viscometer is described, together with the determination of enzyme kinetics and the application of Kramers’ equation to evaluate the effect of viscosity on the rate of ATP hydrolysis by the H+-ATPase.
Development of Viscosity Model for Petroleum Industry Applications
Motahhari, Hamed reza
Heavy oil and bitumen are challenging to produce and process due to their very high viscosity, but their viscosity can be reduced either by heating or dilution with a solvent. Given the key role of viscosity, an accurate viscosity model suitable for use with reservoir and process simulators is essential. While there are several viscosity models for natural gases and conventional oils, a compositional model applicable to heavy petroleum and diluents is lacking. The objective of this thesis is to develop a general compositional viscosity model that is applicable to natural gas mixtures, conventional crudes oils, heavy petroleum fluids, and their mixtures with solvents and other crudes. The recently developed Expanded Fluid (EF) viscosity correlation was selected as a suitable compositional viscosity model for petroleum applications. The correlation relates the viscosity of the fluid to its density over a broad range of pressures and temperatures. The other inputs are pressure and the dilute gas viscosity. Each fluid is characterized for the correlation by a set of fluid-specific parameters which are tuned to fit data. First, the applicability of the EF correlation was extended to asymmetric mixtures and liquid mixtures containing dissolved gas components. A new set of mass-fraction based mixing rules was developed to calculate the fluid-specific parameters for mixtures. The EF correlation with the new set of mixing rules predicted the viscosity of over 100 mixtures of hydrocarbon compounds and carbon dioxide with overall average absolute relative deviations (AARD) of less than 10% either with measured densities or densities estimated by Advanced Peng-Robinson equation of state (APR EoS). To improve the viscosity predictions with APR EoS-estimated densities, general correlations were developed for non-zero viscosity binary interaction parameters. The EF correlation was extended to non-hydrocarbon compounds typically encountered in natural gas industry. It was
Pan-Sang Kang
2016-06-01
Full Text Available Polymer flooding is now considered a technically- and commercially-proven method for enhanced oil recovery (EOR. The viscosity of the injected polymer solution is the key property for successful polymer flooding. Given that the viscosity of a polymer solution has a non-linear relationship with various influential parameters (molecular weight, degree of hydrolysis, polymer concentration, cation concentration of polymer solution, shear rate, temperature and that measurement of viscosity based on these parameters is a time-consuming process, the range of solution samples and the measurement conditions need to be limited and precise. Viscosity estimation of the polymer solution is effective for these purposes. An artificial neural network (ANN was applied to the viscosity estimation of FlopaamTM 3330S, FlopaamTM 3630S and AN-125 solutions, three commonly-used EOR polymers. The viscosities measured and estimated by ANN and the Carreau model using Lee’s correlation, the only method for estimating the viscosity of an EOR polymer solution in unmeasured conditions, were compared. Estimation accuracy was evaluated by the average absolute relative deviation, which has been widely used for accuracy evaluation of the results of ANN models. In all conditions, the accuracy of the ANN model is higher than that of the Carreau model using Lee’s correlation.
The effect of viscosity on ad libitum food intake
Zijlstra, N; Mars, M; Wijk, de, R.A; Westerterp-Plantenga, M; Graaf, de, C
2008-01-01
.... Objective: To investigate the effect of viscosity on ad libitum food intake in real-life setting and to investigate whether a difference in ad libitum intake is related to eating rate and/or eating effort. Design...
Effect of internal viscosity on Brownian dynamics of DNA molecules in shear flow.
Yang, Xiao-Dong; Melnik, Roderick V N
2007-04-01
The results of Brownian dynamics simulations of a single DNA molecule in shear flow are presented taking into account the effect of internal viscosity. The dissipative mechanism of internal viscosity is proved necessary in the research of DNA dynamics. A stochastic model is derived on the basis of the balance equation for forces acting on the chain. The Euler method is applied to the solution of the model. The extensions of DNA molecules for different Weissenberg numbers are analyzed. Comparison with the experimental results available in the literature is carried out to estimate the contribution of the effect of internal viscosity.
PVT characterization and viscosity modeling and prediction of crude oils
Cisneros, Eduardo Salvador P.; Dalberg, Anders; Stenby, Erling Halfdan
2004-01-01
In previous works, the general, one-parameter friction theory (f-theory), models have been applied to the accurate viscosity modeling of reservoir fluids. As a base, the f-theory approach requires a compositional characterization procedure for the application of an equation of state (EOS), in mos...
Christensen, René
2011-01-01
cylindrical tube the characteristic length is the radius. A triangular cross-section does not have a characteristic length, but as will be shown in this paper the model can in fact be used as long as 1) the cross-sectional pressure is constant and 2) a characteristic impedance and propagation wavenumber can...
Density and viscosity modeling and characterization of heavy oils
Cisneros, Sergio; Andersen, Simon Ivar; Creek, J
2005-01-01
are widely used within the oil industry. Further work also established the basis for extending the approach to heavy oils. Thus, in this work, the extended f-theory approach is further discussed with the study and modeling of a wider set of representative heavy reservoir fluids with viscosities up...... to thousands of mPa center dot s. Essential to the presented extended approach for heavy oils is, first, achievement of accurate P nu T results for the EOS-characterized fluid. In particular, it has been determined that, for accurate viscosity modeling of heavy oils, a compressibility correction in the way...
Effect of Electrohydraulic Discharge on Viscosity of Human Blood
G. M. El-Aragi
2013-01-01
Full Text Available Electrohydraulic plasma discharge is a novel technology with high efficiency and high speed and can generate chemically active species like free radicals, ions, atoms, and metastables, accompanied by ultraviolet light emission and shock pressure waves. The aim of this work is to examine the effect of electrohydraulic discharge (EHD system on viscosity of the human blood after different exposure time. The voltage pulsation introduces electric field and temperature jump and at the same time leads to haemolysis of the blood cells. The ratio of blood viscosity under the influence of magnetic field to the viscosity in the absence of magnetic field is directly proportional to the applied magnetic field .
Asymptotic Modeling of the Thin Film Flow with a Pressure-Dependent Viscosity
Eduard Marušić-Paloka
2014-01-01
Full Text Available We study the lubrication process with incompressible fluid taking into account the dependence of the viscosity on the pressure. Assuming that the viscosity-pressure relation is given by the well-known Barus law, we derive an effective model using asymptotic analysis with respect to the film thickness. The key idea is to conveniently transform the governing system and then apply two-scale expansion technique.
A new reference viscosity model for hydrogen sulfide
Schmidt, K.A.G. [Alberta Univ., Edmonton, AB (Canada). Dept. of Chemical and Materials Engineering, Electrical and Computer Engineering Research Facility; Quinones-Cisneros, S.E. [Univ. Nacional Autonoma de Mexico, Mexico City (Mexico). Dept. of Rheology, Materials Research Inst.; Giri, B.R.; Blais, P.; Marriott, R.A. [Alberta Sulphur Research Ltd., Calgary, AB (Canada); Calgary Univ., AB (Canada). Dept. of Chemistry
2010-07-01
New and economical ways of reducing emissions of acid gases to the atmosphere are becoming increasingly important in the petroleum industry. This presentation discussed the promising sequestration option of injecting these acid gases into formations for disposal and or storage. Acid gas injection (AGI) is a commonly used process for the disposal of mixtures of hydrogen sulphide and carbon dioxide, particularly in small scale schemes. The acid gas is sometimes used as a miscible flood fluid for pressure maintenance. The use of AGI is being considered for the production of elemental sulphur. Accurate viscosities are needed in the design of these injection schemes to determine pressure drops due to fluid flow in both the acid gas pipeline and the injection well. This presentation included experimental data and discussed the applicability of the friction theory for viscosity modelling to reproduce the existing experimental visco cities of hydrogen sulphide and its mixtures. The friction theory model was shown to be a highly flexible and powerful tool for the modelling the viscosity of reservoir fluids, from light to heavy fluids under broad conditions of temperature, pressure and composition. During the development of this reference viscosity model, a literature review identified areas where additional data is needed to fill voids and resolve discrepancies of existing data sets. It was concluded that although the developed model was based on limited data, the sound physical reasoning provided good results. An experimental program has been launched to determine the viscosities of hydrogen sulphide (H{sub 2}S) in the critical areas identified in the initial reference model. The current update to the data set consists of experimental H{sub 2}S viscosities up to 1000 bar and at temperatures between 0 and 150 degrees C. The data will be applied to update the H{sub 2}S reference viscosity model based on the friction-theory. The updated reference equation will help improve
Duchesne, Marc A. [Chemical and Biological Engineering Department, University of Ottawa, 161 Louis Pasteur, Ottawa, Ont. (Canada); CanmetENERGY, 1 Haanel Drive, Ottawa, Ontario (Canada); Macchi, Arturo [Chemical and Biological Engineering Department, University of Ottawa, 161 Louis Pasteur, Ottawa, Ont. (Canada); Lu, Dennis Y.; Hughes, Robin W.; McCalden, David; Anthony, Edward J. [CanmetENERGY, 1 Haanel Drive, Ottawa, Ontario (Canada)
2010-08-15
Threshold slag viscosity heuristics are often used for the initial assessment of coal gasification projects. Slag viscosity predictions are also required for advanced combustion and gasification models. Due to unsatisfactory performance of theoretical equations, an artificial neural network model was developed to predict slag viscosity over a broad range of temperatures and slag compositions. This model outperforms other slag viscosity models, resulting in an average error factor of 5.05 which is lower than the best obtained with other available models. Genesee coal ash viscosity predictions were made to investigate the effect of adding Canadian limestone and dolomite. The results indicate that magnesium in the fluxing agent provides a greater viscosity reduction than calcium for the threshold slag tapping temperature range. (author)
Shear viscosity in holography and effective theory of transport without translational symmetry
Burikham, Piyabut
2016-01-01
We study the shear viscosity in an effective hydrodynamic theory and holographic model where the translational symmetry is broken by massless scalar fields. We identify the shear viscosity, $\\eta$, from the coefficient of the shear tensor in the modified constitutive relation, constructed from thermodynamic quantities, fluid velocity and the scalar fields, which break the translational symmetry explicitly. Our construction of constitutive relation is inspired by those derived from the fluid/gravity correspondence in the weakly disordered limit $m/T \\ll 1$. We found that the shear viscosity - entropy density ratio violate the KSS bound even when the translational symmetry is weakly broken. At the leading order in disorder strength, as the energy density is fixed and the disorder strength increases, we observe that the shear viscosity remains unchanged while the entropy grows larger, resulting in the violation of the bound. At higher order correction in $m/T$, we show that the shear viscosity from the constitut...
Effective shear viscosity and dynamics of suspensions of micro-swimmers at moderate concentrations
Constantin, Lipnikov [Los Alamos National Laboratory; Gyrya, V [PENNSYLVANIA STATE UNIV.; Aronson, I [ANL; Berlyand, L [PENNSYLVANIA STATE UNIV.
2009-01-01
Recently, there have been a number of experimental studies suggesting that a suspension of self-propelled bacteria (microswimmers in general) may have an effective viscosity significantly smaller than the viscosity of the ambient fluid. This is in sharp contrast with suspensions of hard passive inclusions, whose presence always increases the viscosity. Here we present a 2D model for a suspension of microswimmers in a fluid and analyze it analytically in the dilute regime (no swimmer-swimmer interactions) and numerically using a Mimetic Finite Difference discretization. Our analysis shows that in the dilute regime the effective shear viscosity is not affected by self-propulsion. But at the moderate concentrations (due to swimmer-swimmer interactions) the effective viscosity decreases linearly as a function of the propulsion strength of the swimmers. These findings prove that (i) a physically observable decrease of viscosity for a suspension of self-propelled bacteria can be explained purely by hydrodynamic interactions and (ii) self-propulsion and interaction of swimmers are both essential to the reduction of the effective shear viscosity. We performed a number of numerical experiments analyzing the dynamics of swimmers resulting from pairwise interactions. The numerical results agree with the physically observed phenomena (e.g., attraction of swimmer to swimmer and swimmer to the wall). This is viewed as an additional validation of the model and the numerical scheme.
Mechanism of sulfide effect on viscosity of HPAM polymer solution
康万利; 周阳; 王志伟; 孟令伟; 刘述忍; 白宝君
2008-01-01
The effect of sulfide on HPAM solution viscosity was studied using BROOKFIELD DV-II viscometer,and the interaction mechanism was discussed.The HPAM solution viscosity was investigated through fully reducing sulfide by the addition of hydrogen peroxide oxidation,and the mechanism of increasing polymer viscosity was investigated.The experimental results also show that there is a critical concentration of 15 mg/L.Below it,the loss rate of HPAM solution viscosity increases more rapidly,but becomes slowly above the critical concentration.A theoretical guidance for oilfields to prepare polymer solution using sewage-water by eliminating sulfide,and it is also importance to prepare polymer solution using sewage-water and save fresh water.
Fluid friction and wall viscosity of the 1D blood flow model
Wang, Xiao-Fei; Matsukawa, Mami; Ghigo, Arthur; Lagrée, Pierre-Yves; Fullana, Jose-Maria
2015-01-01
We study the behavior of the pulse waves of water into a flexible tube for application to blood flow simulations. In pulse waves both fluid friction and wall viscosity are damping factors, and difficult to evaluate separately. In this paper, the coefficients of fluid friction and wall viscosity are estimated by fitting a nonlinear 1D flow model to experimental data. In the experimental setup, a distensible tube is connected to a piston pump at one end and closed at another end. The pressure and wall displacements are measured simultaneously. A good agreement between model predictions and experiments was achieved. For amplitude decrease, the effect of wall viscosity on the pulse wave has been shown as important as that of fluid viscosity.
Effect of Solvation Film on the Viscosity of Colloidal Dispersions
PENG Chang-Sheng; GU Qing-Bao; SONG Shao-Xian
2005-01-01
Viscosity is one of the most important properties of colloids in mixing, transportation, stabilization, energy consumption, and so on. According to Einstein's viscosity equation, the viscosity of a colloidal dispersion increases with the increase of particle concentration. And the equation can be applicable to all micro-particle dispersions, because the effect of solvation films coated on particles can be neglectable in that case. But with the decrease of particle size to nano-scale, the formation of solvation films on nano-particles can greatly affect the viscosity of a dispersion, and Einstein's equation may not be applicable to this case. In this work, one kind of micro-size silica particle and two kinds of nano-size silica particles were used to investigate the effect of solvation films on dispersion viscosity, dispersed in water and ethyl alcohol solvents, respectively. The results of theoretical calculation and experimental investigation show that the increase of viscosity is contributed from solvation films by more than 95 percent for nano-particle dispersions, while less than 10 percent for micro-particle dispersions.
Effect of viscosity on harmonic signals from magnetic fluid
Yoshida, Takashi, E-mail: t_yoshi@ees.kyushu-u.ac.jp; Bai, Shi; Hirokawa, Aiki; Tanabe, Kazuhiro; Enpuku, Keiji
2015-04-15
We explored the effect of viscosity on harmonic signals from a magnetic fluid. Using a numerical simulation that accounts for both the Brownian and Néel processes, we clarified how the magnetization mechanism is affected by viscosity. When the excitation field varies much slower than the Brownian relaxation time, magnetization can be described by the Langevin function. On the other hand, for the case when the excitation field varies much faster than the Brownian relaxation time, but much slower than the Néel relaxation time, the easy axes of the magnetic nanoparticles (MNPs) turn to some extent toward the direction of the excitation field in an equilibrium state. This alignment of the easy axes of MNPs caused by the AC field becomes more significant with the increase of the AC field strength. Consequently, the magnetization is different from the Langevin function even though Néel relaxation time is faster than time period of the external frequency. It is necessary to consider these results when we use harmonic signals from a magnetic fluid in a high-viscosity medium. - Highlights: • We explore the effect of viscosity on harmonic signals from a magnetic fluid. • We clarify how the magnetization mechanism is affected by the viscosity of the fluid. • The magnetization in a high-viscosity medium is different from a Langevin function. • We empirically express the alignment of easy axes of the MNPs caused by an AC field.
Effects of boundary layer and liquid viscosity and compressible air on sloshing characteristics
Zou, Chang-Fang; Wang, De-Yu; Cai, Zhong-Hua
2015-07-01
In this paper, numerical investigations for tank sloshing, based on commercial CFD package FLUENT, are performed to study effects of boundary layer grid, liquid viscosity and compressible air on sloshing pressure, wave height and rising time of impact pressure. Also, sloshing experiments for liquids of different viscosity are carried out to validate the numerical results. Through comparison of numerical and experimental results, a computational model including boundary layer grid can predict the sloshing pressure more accurately. Energy dissipation due to viscous friction leads to reduction of sloshing pressure and wave elevation. Sloshing pressure is also reduced because of cushion effect of compressible air. Due to high viscosity damping effect and compressible air effect, the rising time of impact pressure becomes longer. It is also found that liquid viscosity and compressible air influence distribution of dynamic pressure along the vertical tank wall.
3D viscosity maps for Greenland and effect on GRACE mass balance estimates
van der Wal, Wouter; Xu, Zheng
2016-04-01
The GRACE satellite mission measures mass loss of the Greenland ice sheet. To correct for glacial isostatic adjustment numerical models are used. Although generally found to be a small signal, the full range of possible GIA models has not been explored yet. In particular, low viscosities due to a wet mantle and high temperatures due to the nearby Iceland hotspot could have a significant effect on GIA gravity rates. The goal of this study is to present a range of possible viscosity maps, and investigate the effect on GRACE mass balance estimates. Viscosity is derived using flow laws for olivine. Mantle temperature is computed from global seismology models, based on temperature derivatives for different mantle compositions. An indication for grain sizes is obtained by xenolith findings at a few locations. We also investigate the weakening effect of the presence of melt. To calculate gravity rates, we use a finite-element GIA model with the 3D viscosity maps and the ICE-5G loading history. GRACE mass balances for mascons in Greenland are derived with a least-squares inversion, using separate constraints for the inland and coastal areas in Greenland. Biases in the least-squares inversion are corrected using scale factors estimated from a simulation based on a surface mass balance model (Xu et al., submitted to The Cryosphere). Model results show enhanced gravity rates in the west and south of Greenland with 3D viscosity maps, compared to GIA models with 1D viscosity. The effect on regional mass balance is up to 5 Gt/year. Regional low viscosity can make present-day gravity rates sensitivity to ice thickness changes in the last decades. Therefore, an improved ice loading history for these time scales is needed.
Effect of the shear viscosity on plasma sheath in an oblique magnetic field
Wang, Ting-Ting; Li, Jing-Ju; Ma, J. X.
2016-12-01
In a magnetized plasma sheath, strong velocity shear exists owing to the three-dimensional nature of ion velocity. Thus, the ion viscosity should have an important effect on the sheath structure, which has not been studied. This article presents the study of the effect of ion shear viscosity on the sheath in an oblique magnetic field within the framework of classical cross-field transport. It is shown that the inclusion of the shear viscosity in the ion momentum equation results in a significant reduction in the sheath thickness. It is also shown that the "generalized Bohm criterion" is not affected by the shear viscosity within the present model. However, additional boundary conditions such as the velocity shear arise in the viscous case. The appropriate boundary conditions are formulated, accounting for E × B and diamagnetic drifts at the sheath edge, which affects the criterion and sheath profiles.
Mendoza, Carlos I; Santamaría-Holek, I
2009-01-28
We propose a simple and general model accounting for the dependence of the viscosity of a hard sphere suspension at arbitrary volume fractions. The model constitutes a continuum-medium description based on a recursive-differential method where correlations between the spheres are introduced through an effective volume fraction. In contrast to other differential methods, the introduction of the effective volume fraction as the integration variable implicitly considers interactions between the spheres of the same recursive stage. The final expression for the viscosity scales with this effective volume fraction, which allows constructing a master curve that contains all the experimental situations considered. The agreement of our expression for the viscosity with experiments at low- and high-shear rates and in the high-frequency limit is remarkable for all volume fractions.
Bulk Viscosity Effects in Event-by-Event Relativistic Hydrodynamics
Noronha-Hostler, Jacquelyn; Noronha, Jorge; Andrade, Rone P G; Grassi, Frederique
2013-01-01
Bulk viscosity effects on the collective flow harmonics in heavy ion collisions are investigated, on an event by event basis, using a newly developed 2+1 Lagrangian hydrodynamic code named v-USPhydro which implements the Smoothed Particle Hydrodynamics (SPH) algorithm for viscous hydrodynamics. A new formula for the bulk viscous corrections present in the distribution function at freeze-out is derived starting from the Boltzmann equation for multi-hadron species. Bulk viscosity is shown to enhance the collective flow Fourier coefficients from $v_2(p_T)$ to $v_5(p_T)$ when $% p_{T}\\sim 1-3$ GeV even when the bulk viscosity to entropy density ratio, $% \\zeta/s$, is significantly smaller than $1/(4\\pi)$.
Effect of Fluid Dynamic Viscosity on the Strength of Chalk
Hedegaard, K.; Fabricius, Ida Lykke
The mechanical strength of high porosity and weakly cemented chalk is affected by the fluid in the pores. In this study, the effect of the dynamic viscosity of non-polar fluids has been measured on outcrop chalk from Sigerslev Quarry, Stevns, Denmark. The outcome is that the measured strength...
An alternative eddy-viscosity representation and its implication to turbulence modeling
Jakirlic, Suad; Jovanovic, Jovan; Basara, Branislav
2013-11-01
Large majority of turbulence models in the RANS framework (it holds also in the case of the LES method) is based on the eddy-viscosity rationale. The principle task of modeling the Reynolds stress tensor reduces to modeling the eddy-viscosity, representing, according to Boussinesq (1877), the ``coefficient of proportionality'' between the Reynolds stress and mean rate of strain tensors. In the present contribution an extended formulation based on the least square approach applied to the Boussinesq's correlation is presented. Furthermore, a Taylor-microscale-based formulation is derived originating from the equilibrium assumption related to the equality between the production and dissipation rates of kinetic energy of turbulence. Finally, an expression is proposed reflecting the Reynolds stress anisotropy influence on the eddy-viscosity damping by approaching the solid wall as well as including an appropriate length-scale switch accounting for the viscosity effects through inclusion of the Kolmogorov scales blended with those of the energy-containing eddies. The latter formulation is successfully applied in the framework of an instability-sensitive Reynolds stress model of turbulence. The afore-mentioned eddy-viscosity definitions are comparatively assessed in a series of wall-bounded flow configurations (including separation) in a Reynolds number range.
The effect of exercise on salivary viscosity
Ligtenberg, A.J.M.; Liem, E.H.S.; Brand, H.S.; Veerman, E.C.I.
2016-01-01
A common experience after exercise is the presence of a thick and sticky saliva layer on the oral surfaces, which causes a feeling of a dry mouth. Since the salivary mucin MUC5B is responsible for the visco-elastic behavior of saliva, in the present study we explored the effect of exercise on both
Mizue MUNEKATA; Hidefumi TAKAKI; Hideki OHBA; Kazuyoshi MATSUZAKI
2005-01-01
Effects of non-Newtonian viscosity for surfactant solution on the vortex characteristics and drag-reducing rate in a swirling pipe flow are investigated by pressure drop measurements, velocity profile measurements and viscosity measurements. Non-Newtonian viscosity is represented by power-law model (τ = kD n). Surfactant solution used has shear-thinning viscosity with n ＜ 1.0. The swirling flow in this study has decay of swirl and vortex-type change from Rankin's combined vortex to forced vortex. It is shown that the effect of shear-thinning viscosity on the decay of swirl intensity is different by vortex category and the critical swirl number with the vortex-type change depends on shear-thinning viscosity.
Empirical slip and viscosity model performance for microscale gas flows.
Gallis, Michail A.; Boyd, Iain D. (University of Michigan, Ann Arbor, MI); McNenly, Matthew J. (University of Michigan, Ann Arbor, MI)
2004-07-01
For the simple geometries of Couette and Poiseuille flows, the velocity profile maintains a similar shape from continuum to free molecular flow. Therefore, modifications to the fluid viscosity and slip boundary conditions can improve the continuum based Navier-Stokes solution in the non-continuum non-equilibrium regime. In this investigation, the optimal modifications are found by a linear least-squares fit of the Navier-Stokes solution to the non-equilibrium solution obtained using the direct simulation Monte Carlo (DSMC) method. Models are then constructed for the Knudsen number dependence of the viscosity correction and the slip model from a database of DSMC solutions for Couette and Poiseuille flows of argon and nitrogen gas, with Knudsen numbers ranging from 0.01 to 10. Finally, the accuracy of the models is measured for non-equilibrium cases both in and outside the DSMC database. Flows outside the database include: combined Couette and Poiseuille flow, partial wall accommodation, helium gas, and non-zero convective acceleration. The models reproduce the velocity profiles in the DSMC database within an L{sub 2} error norm of 3% for Couette flows and 7% for Poiseuille flows. However, the errors in the model predictions outside the database are up to five times larger.
Renormalization-group theory for the eddy viscosity in subgrid modeling
Zhou, YE; Vahala, George; Hossain, Murshed
1988-01-01
Renormalization-group theory is applied to incompressible three-dimensional Navier-Stokes turbulence so as to eliminate unresolvable small scales. The renormalized Navier-Stokes equation now includes a triple nonlinearity with the eddy viscosity exhibiting a mild cusp behavior, in qualitative agreement with the test-field model results of Kraichnan. For the cusp behavior to arise, not only is the triple nonlinearity necessary but the effects of pressure must be incorporated in the triple term. The renormalized eddy viscosity will not exhibit a cusp behavior if it is assumed that a spectral gap exists between the large and small scales.
Phantom dark energy as an effect of bulk viscosity
Velten, Hermano; Meng, Xinhe
2013-01-01
In a homogeneous and isotropic universe bulk viscosity is the unique viscous effect capable to modify the background dynamics. Effects like shear viscosity or heat conduction can only change the evolution of the perturbations. The existence of a bulk viscous pressure in a fluid, which in order to obey to the second law of thermodynamics is negative, reduces its effective pressure. We discuss in this study the degeneracy in bulk viscous cosmologies and address the possibility that phantom dark energy cosmology could be caused by the existence of non-equilibrium pressure in any cosmic component. We establish the conditions under which either matter or radiation viscous cosmologies can be mapped into the phantom dark energy scenario with constraints from multiple observational data-sets
Zhang, Shuxia; Yuen, David A.
1994-01-01
We have investigated the influences of lateral variations of viscosity on the moment of inertia tensor from viscous flows due to the density anomalies in the mantle inferred from seismic tomographic models. The scaling relations between the density and the seismic anomalies is taken as either a constant or a function increasing with depth in accord with the recent high-pressure experimental studies. The viscosity is taken as an exponential function of the 3D density anomaly. In models with an isoviscous background, the effects on the perturbed moment of inertia tensor from the lateral viscosity variations are smaller than those due to variations in the radial viscosity profiles. In mantle models with a background viscosity increasing with depth, the influences of the lateral viscosity variations are significant. The most striking feature in the latter case is that the two off-diagonal elements delta I(sub xz) and delta I(sub yz) in the inertia tensor exhibit greatest sensitivity to lateral variations of the viscosity. While the other elements of the inertia change by only about a few tens of percent in the range of lateral viscosity contrast considered (less than 300), delta I(sub xz) and delta I(sub yz) can vary up to 40 times even with a change in sign, depending on the radial viscosity stratification and the location of the strongest lateral variations. The increase in the velocity-density scaling relation with depth can reduce the influences of the lateral viscosity variations, but it does not change the overall sensitive nature of delta I(sub xz) and delta I(sub yz). This study demonstrates clearly that the lateral viscosity variations, especially in the upper mantle, must be considered in the determination of long-term polar wander, since the variations in the delta I(sub xz) and delta I(sub yz) terms are directly responsible for exciting rotational movements.
Surface reproduction of elastomeric materials: viscosity and groove shape effects
Mahmood, N.; Abu Kasim, N.H.; Azuddin, M.; Kasim, N.L. Abu
2010-01-01
Objective: To evaluate the effect of viscosity and type of grooves on surface detail reproduction of elastomeric impression materials. Methods: Express putty/light-, Impregum medium- and heavy/light-bodied and Aquasil medium- and putty/light-bodied elastomeric impression materials were chosen for this study. Five impressions were made using a cylindrical aluminum reference block with U- and V- shaped grooves and to produce 35 master dies. Each master die was immersed in distilled water at 370...
Models to estimate viscosities of ternary metallic melts and their comparisons
王习东; 李文超
2003-01-01
Three models, based on Chou's general geometric thermodynamic model, to predict the viscosity of ternary metallic melts have been established. The calculation equations of the model have been deduced. The experimental viscosity data of Ag-Au-Cu systems were used to verify the models and the calculation results with the models are consistent with the reported experimental data. The advantages, requirement and applicability of the models have been analyzed and compared. The models have also been utilized to predict the viscosity of Ag-Sn-Cu system. The viscosity of the system was experimentally measured and the results are consistent with the calculated value of the models.
2014-09-26
34 FOREIGN TECHNOLOGY DIVISION i00 Lfl .. THE EFFECT OF FLUOROCARBON SURFACTANT ADDITIVES ON THE EFFECTIVE VISCOSITY OF ACETONE SOLUTIONS OF CELLULOSE ...ADDITIVES ON TH~ .. t- ’_ ition EFFECTIVE VISCOSITY OF ACETONE SOLUTIONS OF CELLULOSE DIACETATE D~rbt~l By: L.A. Shits, N. Yu. Kal’nova Codesuton English...VISCOSITY OF ACETONE SOLUTIONS OF CELLULOSE DIACETATE L. A. Shits, N. Yu. Kal’nova (Institute of Physical Chemistry of the AS USSR, Moscow) ! - The
Effect of temperature on rotational viscosity in magnetic nano fluids.
Patel, R
2012-10-01
Flow behavior of magnetic nano fluids with simultaneous effect of magnetic field and temperature is important for its application for cooling devices such as transformer, loud speakers, electronic cooling and for its efficiency in targeted drug delivery and hyperthermia treatment. Using a specially designed horizontal capillary viscometer, temperature-sensitive and non-temperature-sensitive magnetic nano fluids are studied. In both these case the temperature-dependent rotational viscosity decreases, but follows a quite different mechanism. For temperature-sensitive magnetic nano fluids, the reduction in rotational viscosity is due to the temperature dependence of magnetization. Curie temperature ((T)(c)) and pyromagnetic coefficient are extracted from the study. A fluid with low T(c) and high pyromagnetic coefficient is useful for thermo-sensitive cooling devices and magnetic hyperthermia. For non-temperature-sensitive magnetic nano fluids, reduction in rotational viscosity is due to removal of physisorbed secondary surfactant on the particle because of thermal and frictional effects. This can be a good analogy for removal of drug from the magnetic particles in the case of targeted drug delivery.
Gamma radiation effects on the viscosity of green banana flour
Uehara, Vanessa B.; Inamura, Patricia Y.; Mastro, Nelida L. Del [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)], e-mail: vanessa.uehara@usp.br, e-mail: patyoko@yahoo.com, e-mail: nlmastro@ipen.br
2009-07-01
Banana (Musa sp) is a tropical fruits with great acceptability among consumers and produced in Brazil in a large scale. Bananas are not being as exploited as they could be in prepared food, and research could stimulate greater interest from industry. The viscosity characteristics and a product consistency can determine its acceptance by the consumer. Particularly the starch obtained from green banana had been studied from the nutritional point of view since the concept of Resistant Starch was introduced. Powder RS with high content of amylose was included in an approved food list with alleged functional properties in Brazilian legislation. Ionizing radiation can be used as a public health intervention measure for the control of food-borne diseases. Radiation is also a very convenient tool for polymer materials modification through degradation, grafting and crosslinking. In this work the influence of ionizing radiation on the rheological behavior of green banana pulp was investigated. Samples of green banana pulp flour were irradiated in a {sup 60}Co Gammacell 220 (AECL) with doses of 0 kGy,1 kGy, 3 kGy, 5 kGy and 10 kGy in glass recipients. After irradiation 3% and 5% aqueous dilution were prepared and viscosity measurements performed in a Brooksfield, model DVIII viscometer using spindle SC4-18 and SC4-31. There was a reduction of the initial viscosity of the samples as a consequence of radiation processing, being the reduction inversely proportional to the flour concentration. The polysaccharide content of the banana starch seems to be degraded by radiation in solid state as shown by the reduction of viscosity as a function of radiation dose. (author)
Modelling viscosity and mass fraction of bitumen - diluent mixtures
Miadonye, A.; Latour, N.; Puttagunta, V.R. [Lakehead Univ., Thunder Bay, ON (Canada)
1999-07-01
In recovery of bitumen in oil sands extraction, the reduction of the viscosity is important above and below ground. The addition of liquid diluent breaks down or weakens the intermolecular forces that create a high viscosity in bitumen. The addition of even 5% of diluent can cause a viscosity reduction in excess of 8%, thus facilitating the in situ recovery and pipeline transportation of bitumen. Knowledge of bitumen - diluent viscosity is highly important because without it, determination of upgrading processes, in situ recovery, well simulation, heat transfer, fluid flow and a variety of other engineering problems would be difficult or impossible to solve. The development of a simple correlation to predict the viscosity of binary mixtures of bitumen - diluent in any proportion is described. The developed correlation used to estimate the viscosities and mass fractions of bitumen - diluent mixtures was within acceptable limits of error. For the prediction of mixture viscosities, the developed correlation gave the best results with an overall average absolute deviation of 12% compared to those of Chironis (17%) and Cragoe (23%). Predictions of diluent mass fractions yielded a much better result with an overall average absolute deviation of 5%. The unique features of the correlation include its computational simplicity, its applicability to mixtures at temperatures other than 30 degrees C, and the fact that only the bitumen and diluent viscosities are needed to make predictions. It is the only correlation capable of predicting viscosities of mixtures, as well as diluent mass fractions required to reduce bitumen viscosity to pumping viscosities. The prediction of viscosities at 25, 60.3, and 82.6 degrees C produced excellent results, particularly at high temperatures with an average absolute deviation of below 10%. 11 refs., 3 figs., 8 tabs.
Effect of gamma irradiation on starch viscosity and physicochemical properties of different rice
Wu Dianxing E-mail: dianxingwu@hotmail.com; Shu Qingyao; Wang Zhonghua; Xia Yingwu
2002-08-01
Three types of rice cultivars (indica, japonica and hybrid rice) with similar intermediate apparent amylose content (AAC) as well as early indica rice cultivars with different amounts of AAC were selected for studying the effects of gamma irradiation on starch viscosity, physicochemical properties and starch granule structure. Four major parameters of RVA profile, that was determined by a rapid visco analyser (RVA, Model-3D), peak viscosity, hot pasting viscosity, cool pasting viscosity, and setback viscosity, were considerably decreased with increasing dose levels. Gamma irradiation reduced the amylose contents in the cultivars with low AAC, intermediate AAC, and glutinous rice, but had no effects on the high AAC cultivar. No visible changes in gelatinization temperature were detected after irradiation, but the peak time was reduced with the dose levels. Gel consistency was significantly increased in the tested cultivars, especially in the high AAC indica rice. The starch granules were somewhat deformed by gamma irradiation. These results suggested that it is promising to use gamma irradiation to improve rice eating or cooking quality.
Notes on shear viscosity bound violation in anisotropic models
Ge, Xian-Hui
2015-01-01
The shear viscosity bound violation in Einstein gravity for anisotropic black branes is discussed, with the aim of constraining the deviation of the shear viscosity-entropy density ratio from the shear viscosity bound using causality and thermodynamics analysis. The results show that no stringent constraints can be imposed. The diffusion bound in anisotropic phases is also studied. Ultimately, it is concluded that shear viscosity violation always occurs in cases where the equation of motion of the metric fluctuations cannot be written in a form identical to that of the minimally coupled massless scalar fields.
Employing Taylor and Heisenberg subfilter viscosities to simulate turbulent statistics in LES models
Degrazia, G. A.; Rizza, U.; Puhales, F. S.; Welter, G. S.; Acevedo, O. C.; Maldaner, S.
2012-02-01
A turbulent subfilter viscosity for Large Eddy Simulation (LES) based on the Taylor statistical diffusion theory is proposed. This viscosity is described in terms of a velocity variance and a time scale, both associated to the inertial subrange. This new subfilter viscosity contains a cutoff wavenumber kc, presenting an identical form (differing by a constant) to the Heisenberg subfilter viscosity. Therefore, both subfilter viscosities are described in terms of a sharp division between large and small wavenumbers of a turbulent flow and, henceforth, Taylor and Heisenberg subfilter viscosities are in agreement with the sharp Fourier filtering operation, frequently employed in LES models. Turbulent statistics of different orders, generated from atmospheric boundary layer simulations employing both Taylor and Heisenberg subfilter viscosities have been compared with observations and results provided by other simulations. The comparison shows that the LES model utilizing the approaches of Taylor and Heisenberg reproduces these turbulent statistics correctly in different vertical regions of a planetary convective boundary layer (CBL).
Viscosity and dissipative hydrodynamics from effective field theory
Grozdanov, Sašo; Polonyi, Janos
2015-05-01
With the goal of deriving dissipative hydrodynamics from an action, we study classical actions for open systems, which follow from the generic structure of effective actions in the Schwinger-Keldysh closed-time-path (CTP) formalism with two time axes and a doubling of degrees of freedom. The central structural feature of such effective actions is the coupling between degrees of freedom on the two time axes. This reflects the fact that from an effective field theory point of view, dissipation is the loss of energy of the low-energy hydrodynamical degrees of freedom to the integrated-out, UV degrees of freedom of the environment. The dynamics of only the hydrodynamical modes may therefore not possess a conserved stress-energy tensor. After a general discussion of the CTP effective actions, we use the variational principle to derive the energy-momentum balance equation for a dissipative fluid from an effective Goldstone action of the long-range hydrodynamical modes. Despite the absence of conserved energy and momentum, we show that we can construct the first-order dissipative stress-energy tensor and derive the Navier-Stokes equations near hydrodynamical equilibrium. The shear viscosity is shown to vanish in the classical theory under consideration, while the bulk viscosity is determined by the form of the effective action. We also discuss the thermodynamics of the system and analyze the entropy production.
王瑞; 李昌烽; 吴桂芬; 胡自成; 王迎慧
2011-01-01
In recent studies of drag reduction in wall turbulence it was proposed that the streching polymer produces a self-consistent effective viscosity that increases with the distance from the wall. This linear effective viscosity theory for drag reduction in the wall-bounded turbulent flow was examined by introducing such linear viscosity profile to Navier-Stokes equation, and computing with Reynolds stress model. It shows that the linear effective viscosity model demonstrates drag reducing properties, and the percentage of the drag reduction increases up to the drag reduction saturation with the slope of viscosity profile increasing. The level of drag reduction up to about 75% , approaching the maximum drag reduction extent was obtained. The turbulence important characteristics including mean velocity profile, root-mean-square velocity fluctuations, Reynolds stress and viscous stress profiles are in agreement with the direct numerical simulation results and experimental data. It is universal and reasonable in some content for the linear viscosity profile model to explain drag reduction mechanism.%近来在壁面湍流高分子减阻研究中，一种拉伸的高分子产生自相一致的等效粘度的理论提了出来，这个等效粘度随离开壁面的距离而增长。本文将此线性分布等效粘度置入Navier-Stokes方程，运用雷诺应力模型计算在壁面湍流中的减阻情况，检验这种等效粘度的可行性。可以发现，此模型可以得到湍流减阻的效果，所得到的减阻率随着等效粘度线性分布斜率的增加增大到一个饱和值。本文得到了接近最大减阻极限的减阻率(75％)。且由此模型计算得到的减阻湍流特征值包括平均速度分布、速度脉动均方根、雷诺应力及粘性应力分布都与实验数据和直接数值模拟结果相符。该线性分布等效粘度减阻模型大致上把握了高分子湍流减阻特性，给出了在一定程度上对湍流减阻机理普适和合理的解释。
The effects of depth-dependent viscosity in the lithosphere on post-seismic viscous relaxation
Yamasaki, T.; Houseman, G. A.
2010-12-01
Following an earthquake elastic strain is relaxed by several mechanisms, including aseismic slip, poroelastic relaxation and viscous relaxation. The observed surface deformation reflects the integrated effect of these mechanisms, and it is therefore essential to evaluate the behaviour of each deformation process in order to advance our understanding of the co-and post-seismic deformations in the earthquake cycle. This evaluation requires mathematical models of the deformation, ground-truthed where possible using geodetic data (GPS and/or InSAR) to measure the surface deformation that accompanies and follows the earthquake. In this study, the effects of depth-dependent viscosity (DDV) variation in the lithosphere on the signature of post-seismic viscous relaxation are compared with the predictions of a uniform viscosity (UNV) model. For this purpose, we use a new parallelized 3-D finite element code, oregano_ve, to solve the linear Maxwell visco-elastic response following an applied internal fault displacement in a rectangular block. The model consists of a visco-elastic layer overlain by an elastic layer; the visco-elastic layer has a depth-dependent viscosity: η = η0exp[c(z0-z)], where η0 is the viscosity at the bottom of the layer, c is a constant (c = 0 for UNV model), z is the depth and z0 is the depth at the bottom of the layer. The fault displacement is implemented using the split node method developed by Melosh and Raefsky (BSSA, 71,1391,1981). We compare the relaxation of displacement that occurs on the surface after an instantaneous strike-slip faulting event for UNV and DDV models. For any given DDV model, we can choose a UNV model which approximately mimics the behaviour of the DDV model, but the required UNV viscosity depends on the distance from the fault; a smaller UNV viscosity is implied for a surface point that is further from the fault. The quality with which a UNV model can match a DDV simulation also depends on distance from the fault. In the
Shahzadi, Iqra; Nadeem, S.; Rabiei, Faranak
The current article deals with the combine effects of single wall carbon nanotubes and effective viscosity for the peristaltic flow of nanofluid through annulus. The nature of the walls is assumed to be permeable. The present theoretical model can be considered as mathematical representation to the motion of conductive physiological fluids in the existence of the endoscope tube which has many biomedical applications such as drug delivery system. The outer tube has a wave of sinusoidal nature that is travelling along its walls while the inner tube is rigid and uniform. Lubrication approach is used for the considered analysis. An empirical relation for the effective variable viscosity of nanofluid is proposed here interestingly. The viscosity of nanofluid is the function of radial distance and the concentration of nanoparticles. Exact solution for the resulting system of equations is displayed for various quantities of interest. The outcomes show that the maximum velocity of SWCNT-blood nanofluid enhances for larger values of viscosity parameter. The pressure gradient in the more extensive part of the annulus is likewise found to increase as a function of variable viscosity parameter. The size of the trapped bolus is also influenced by variable viscosity parameter. The present examination also revealed that the carbon nanotubes have many applications related to biomedicine.
Sulaiman Al-Zuhair, Mirghani I. Ahmed and Yousif A. Abakr
2012-10-01
Full Text Available This paper discusses the apparent viscosity of crude palm oil, using rotary viscometer, under different boundary conditions. It was experimentally shown that the apparent viscosity of palm oil drops with increasing of the shear rate and the temperature. However, the effect of temperature on the viscosity tends to fade at temperatures beyond 80 oC. A correlation between the apparent viscosity of crude palm oil and the operating conditions was developed. This correlation can be used in design of crude palm oil settlers and in determining the optimum operating conditions.Key Words: Crude palm oil, apparent viscosity, shear rate, modelling, separation
Viscosity modeling for ionic liquid solutions by Eyring-Wilson equation
He Yang-Chun
2012-01-01
Full Text Available A semi-theoretical model based on the classical Eyring’s mixture viscosity equation and the Wilson activity coefficient equation is presented for correlating the viscosity of ionic liquids with solvent systems. The accuracy of the proposed model was verified by comparing calculated and experimental viscosity values from literatures for 49mixtures with total 1560 data points. The results show that the equation similar to the Wilson activity coefficient equation can be well applied to describe the non-ideal term in the Eyring’s mixture viscosity equation. The model has a relatively simple mathematical form and can be easily incorporated into process simulation software.
Effect of Short Chain Alcohols upon Viscosity of TTAB Solution
Yun-fei Yan; Hua-zhen Li; Hai-yang Yang; Jia-sheng Qian; Ping-ping Zhu; Ping-sheng He
2008-01-01
The effect of ethanol (C2H5OH),propanol (C3H7OH),and butanol (C4H9OH) upon the viscosity of tetrade- cyltrimethylammonium bromide (TTAB) solution in the presence or absence of KBr at 30℃ was investi- gated,where the surfactant concentration Cs is kept constant.In the absence of KBr,the relative viscosity ηr of TTAB solution increases linearly with the alcohol concentration CA,indicating that the alcohols do not promote micelle formation of TTAB.In the presence of KBr,ηr linearly decreases with CA for C2H5OH, but it exhibits a maximum with increasing CA for C3H7OH or C4H9OH.The facts reveal that C2H5OH or C4H9OH promotes the micelle formation of TTAB.A possible explanation is that the hydrophobicity of the micellar interior is enhanced by KBr,so that C2H5OH or C4H9OH can dissolve in micelle and promotes micelle formation.In the presence of KCl,which is less efficient in promoting the micelle formation of cationic surfactant,both C3H7OH and C4H9OH have only a slight effect on the micelle formation.In contrast,due to the hydrophilicity,C2H5OH cannot dissolve in micelles in the presence of KBr or KCl.
Dörr, Aaron; Mehdizadeh, Amirfarhang
2012-01-01
Based on the notion of a construction process consisting of the stepwise addition of particles to the pure fluid, a discrete model for the apparent viscosity as well as for the maximum packing fraction of polydisperse suspensions of spherical, non-colloidal particles is derived. The model connects the approaches by Bruggeman and Farris and is valid for large size ratios of consecutive particle classes during the construction process. Furthermore, a new general form of the well-known Krieger equation allowing for the choice of a second-order Taylor coefficient for the volume fraction is proposed and then applied as a monodisperse reference equation in the course of polydisperse modeling. By applying the polydisperse viscosity model to two different particle size distributions (Rosin-Rammler and uniform distribution), the influence of polydispersity on the apparent viscosity is examined. The extension of the model to the case of small size ratios as well as to the inclusion of shear rate effects is left for fut...
Effect of combined treatments on viscosity of whey dispersions
Camillo, A.; Sabato, S.F. E-mail: sfsabato@ipen.br
2004-10-01
Whey proteins, enriched protein fractions from milk, are of great interest as ingredients due to nutritional value associated with its functional properties. These proteins could have their structural properties improved when some treatments are applied, such as thermal and gamma irradiation or when some compounds are added. The current work aimed to study the viscometer behavior of whey dispersions submitted to two different combined treatments: (1) thermal plus irradiation and (2) thermal plus vacuum and N{sub 2} plus irradiation. Dispersions of whey protein in water (5% and 8% protein (w/v) base) and containing proteins and glycerol at ratios 1:1 and 2:1 (protein:glycerol) were submitted to both combined treatments. The irradiation doses were 0, 5, 15 and 25 kGy. The viscosity of the two combined treatments and for four levels of absorbed doses is presented and the combined effects are discussed. The thermal treatment combined with gamma irradiation contributed to increase the viscosity as irradiation doses increases for both (5% and 8%) concentrations of proteins (p<0.05). For protein and glycerol solutions, the irradiation dose seemed to result in a slightly increase. The vacuum applied before the irradiation showed a small contribution.
Effect of combined treatments on viscosity of whey dispersions
Camillo, A.; Sabato, S. F.
2004-09-01
Whey proteins, enriched protein fractions from milk, are of great interest as ingredients due to nutritional value associated with its functional properties. These proteins could have their structural properties improved when some treatments are applied, such as thermal and gamma irradiation or when some compounds are added. The current work aimed to study the viscometer behavior of whey dispersions submitted to two different combined treatments: (1) thermal plus irradiation and (2) thermal plus vacuum and N 2 plus irradiation. Dispersions of whey protein in water (5% and 8% protein (w/v) base) and containing proteins and glycerol at ratios 1:1 and 2:1 (protein:glycerol) were submitted to both combined treatments. The irradiation doses were 0, 5, 15 and 25 kGy. The viscosity of the two combined treatments and for four levels of absorbed doses is presented and the combined effects are discussed. The thermal treatment combined with gamma irradiation contributed to increase the viscosity as irradiation doses increases for both (5% and 8%) concentrations of proteins ( p<0.05). For protein and glycerol solutions, the irradiation dose seemed to result in a slightly increase. The vacuum applied before the irradiation showed a small contribution.
Drag reduction by linear viscosity model in turbulent channel flow of polymer solution
吴桂芬; 李昌烽; 黄东升; 赵作广; 冯晓东; 王瑞
2008-01-01
A further numerical study of the theory that the drag reduction in the turbulence is related to the viscosity profile growing linearly with the distance from the wall was performed.The constant viscosity in the Navier-Stokes equations was replaced using this viscosity model.Some drag reduction characteristics were shown comparing with Virk’s phenomenology.The mean velocity and Reynolds stress profiles are consistent with the experimental and direct numerical simulation results.A drag reduction level of 45% was obtained.It is reasonable for this linear viscosity model to explain the mechanism of turbulence drag reduction in some aspects.
Sznitman, Josue; Purohit, Prashant K; Arratia, Paulo E
2009-01-01
The effects of fluid viscosity on the kinematics of a small swimmer at low Reynolds number are investigated in both experiments and in a simple model. The swimmer is the nematode Caenorhabditis elegans, which is an undulating roundworm approximately 1 mm long. Experiments show that the nematode maintains a highly periodic swimming behavior as the fluid viscosity is varied from 1.0 mPa-s to 12 mPa-s. Surprisingly, the nematode's swimming speed (~0.35 mm/s) is nearly insensitive to the range of fluid viscosities investigated here. However, the nematode's beating frequency decreases to an asymptotic value (~1.7 Hz) with increasing fluid viscosity. A simple model is used to estimate the nematode's Young's modulus and tissue viscosity. Both material properties increase with increasing fluid viscosity. It is proposed that the increase in Young's modulus may be associated with muscle contraction in response to larger mechanical loading while the increase in effective tissue viscosity may be associated with the energ...
Verification of mathematical models for calculation of viscosity of molten oxide systems
S. Rosypalová
2014-06-01
Full Text Available The subject of this work is the comparison of numerically obtained values of dynamic viscosity using different types of mathematical models and experimentally measured data of viscosity of oxide systems. The ternary system of SiO2-CaO-Al2O3, which presents simplified base of the casting powders used in technological process, was submitted to the experiment. Experimental research of dynamic viscosity is highly limited by its complexity. That’s why model studies play such an important role in this field. For mathematic calculation of viscosity the NPL model, Iida model and Urbain model were chosen. The results of simulation were compared with the experimentally obtained values of viscosity.
Snehasis Daschakraborty; Ranjit Biswas
2012-07-01
Molecular dynamics simulations of model liquids interacting via Lennard-Jones (L-J) and Stockmayer (SM) interactions have been carried out to explore the effects of the longer-ranged dipole-dipole interaction on solvent viscosity and diffusion. Switching on of the dipolar interaction at a fixed density and temperature has been found to increase the viscosity over that of the LJ liquid, the extent of increase being a few percent to as large as ∼60% depending on the magnitude of the solvent dipole moment used in the SM potential. The simulated translational and rotational diffusion coefficients show strong dipole moment and temperature dependences, eventhough effects of these parameters on solvent-solvent radial distribution function are moderate. Interestingly, a partial solute-solvent decoupling is observed when the simulated translational and rotational diffusion coefficients are connected to the simulated viscosity coefficients via the Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) relations. In the limit of large dipole moment, simulated self-part of the van Hove correlation function at intermediate times reveals a departure from the Gaussian distribution with particle displacement. This suggests that dynamic heterogeneity is one of the reasons for the departure of centre-of-mass diffusion from the SE relation in these model systems.
The Effect of Lubricant Viscosity in High Pressure Forming
Syahrullail, S.; Ridzuan, M. J. M.; Seah, W. B.
2010-06-01
In this research, the effects of viscosity of lubricant in cold work extrusion process were investigated. The experimental evaluation was carried out by using cold work plane strain extrusion apparatus with a pair of 45-degree die half angle and a symmetrical workpiece (billet). The billet material was annealed pure aluminum, A1100. The analytical evaluation was carried out using a visioplasticity method. The testing lubricant is RBD palm olein, RBD palm stearin and palm fatty acid distillate. The results were compared with the additive free paraffinic mineral oil. The result shows that palm oil has advantage in reducing the extrusion load. We confirmed that palm oil showed satisfactory lubrication performance, as compared to additive free paraffinic mineral oil.
Jeon, Sang Hyeon; Kim, Bum Suk; Huh, Jong Chul [Jeju National Univ., Jeju (Korea, Republic of); Go, Young Jun [Hanjin Ind, Co., Ltd., Yangsan (Korea, Republic of)
2016-01-15
The wake effects behind wind turbines were investigated by using data from a Met Mast tower and the SCADA (Supervisory Control and Data Acquisition) system for a wind turbine. The results of the wake investigations and predicted values for the velocity deficit based on the eddy viscosity model were compared with the turbulence intensity from the Lange model. As a result, the velocity deficit and turbulence intensity of the wake increased as the free stream wind speed decreased. In addition, the magnitude of the velocity deficit for the center of the wake using the eddy viscosity model was overestimated while the turbulence intensity from the Lange model showed similarities with measured values.
Variable viscosity condition in the modeling of a slider bearing
Uprety, Kedar Nath
2014-01-01
To reduce tear and wear of machinery lubrication is essential. Lubricants form a layer between two surfaces preventing direct contact and reduce friction between moving parts and hence reduce wear. In this short letter the lubrication of two slider bearings with parallel and nonparallel is studied. First, we show that bearings with parallel plates cannot support any load. For bearings with nonparallel plates we are interested on how constant and temperature dependent viscosity affects the properties of the bearings. Also, a critical temperature for which the bearings would fail due to excess in temperature is found for both latter cases. If the viscosity is constant, the critical temperature is given by an explicit formula, while for the non-constant viscosity the critical temperature can be always found from a closed form formula involving Weber functions
Effect of Fluid Viscosity on Centrifugal Pump Performance
Kim, Nohhyeong [GS Caltex Corporation, Daejeon (Korea, Republic of)
2013-06-15
The characteristics of centrifugal pump performance according to fluid viscosity change were studied experimentally. A small volute pump with low specific speed was tested by changing the viscosity of an aqueous solution of sugar and glycerin, which is considered a Newtonian fluid. After finishing the test, the total head, shaft horsepower, and pump efficiency were compared with those of a water pump. The results are summarized as follows: when the fluid viscosity is increased, the shut-off head shows very little change but the total head decreases gradually as the flow increases, and this makes the H-Q curve leaning rapidly, and when the fluid viscosity is increased, the shaft horsepower shows very little change at the shutoff condition; however, the shaft horsepower increases more rapidly with an increase in the flow and viscosity.
Ion-viscosity effects on plasma-liner formation and implosion via merging supersonic plasma jets
Schillo, Kevin; Cassibry, Jason; Samulyak, Roman; Shih, Wen; Hsu, Scott; PLX-Alpha Team
2016-10-01
The PLX- α project endeavors to study plasma-liner formation and implosion by merging a spherical array of plasma jets as a candidate standoff driver for MIF. Smoothed particle hydrodynamics is used to model the liner formation and implosion processes. SPH is a meshless Lagrangian method to simulate fluid flows by dividing a fluid into a set of particles and using a summation interpolant function to calculate the properties and gradients for each of these particles. Ion viscosity is anticipated to be an important mechanism for momentum transport during liner formation, implosion, and stagnation. To study this, ion viscosity was incorporated into the code. To provide confidence in the numerical output and to help identify the difference between numerical and physical diffusion, a series of test cases were performed, consisting of Couette flow, Gresho vortex, and a Taylor-Green vortex. An L2-norm analysis was performed to measure the error and convergence. Simulations of conical (6 jets) and 4 π (60 jets) liners with and without ion viscosity reveal potential effects of viscosity on ram pressure, Mach-number degradation, and evolution of liner perturbations during jet merging and liner implosion.
Nirmala sundaram
2017-01-01
Full Text Available A comprehensive hydrodynamic study of a Liquid - Solid Circulating Fluidized Bed (LSCFB is conducted with changes in viscosity of the fluidizing medium and the inventory height of solids initially fed into the system. An LSCFB of height 2.95m and riser outer diameter 0.1m was chosen for experimentation. The three liquid media systems with varying viscosities that were chosen were water, glycerol 10% (v/v and glycerol 20% (v/v. Effect of inventory on the hydrodynamics was also studied, by taking initial heights of inventory to be 15cm, 25cm and 35cm. The hydrodynamic studies concentrated on pressure gradients along the axial pressure tapings, axial solid holdup, average solid holdup, solid circulation rate and slip velocity. Uniformity in axial solid holdup and average solid holdup was validated for changes in viscosity and inventory. Solid flux was seen to follow an inverse relationship to holdup. The changes in slip velocity with varying viscosity and inventory were studied, and found to decrease with both variables. The distribution parameter, Co of the drift flux model was found to be in the range of 0.983-0.994, suggesting non-uniformity in radial solid distribution, with higher solid concentration by the walls compared to the core of the column.
Nuño, P; Hernández, A; Mendoza-Figueroa, T; Panduro, A
1997-02-18
This study analyzes the relationship of plasmatic colloid osmotic pressure (PCO) and viscosity with the different hyperlipidemic stages observed in rats with acute liver damage induced by carbon tetrachloride (CCl4) and in rats with nephrotic syndrome induced by puromycin amino nucleoside (PAN). In both animal models viscosity increases were associated with the induction of the hyperlipidemic stage characterized by an increase of high density lipoproteins (HDL) and steady-state levels (SSL) of apo A-1 mRNA. In both animal models PCO decreased at early stages of the disease when hyperlipidemia was characterized principally by an increase of total cholesterol and triacylglycerols, but was not associated with the induction of HDL and apo A-1 mRNA. To confirm the in vivo findings, we studied the effect of viscosity on apo A-1 gene expression in an in vitro model using cultured hepatocytes. When medium viscosity was maintained below physiological values, an induction of the SSL of apo A-1 mRNA was observed. By contrast, when medium viscosity was raised to values similar or higher than the physiological range, the SSL of apo A-1 mRNA decreased steadily and after 24 h incubation an almost total inhibition was observed. These results suggest that in both experimental animal models of secondary hyperlipidemia, small viscosity changes below the physiological range, most probably in the interstitial fluid, can induce apo A-1 gene expression at the mRNA level, and that when viscosity reaches physiological values, apo A-1 gene expression is inhibited. Both effects were shown in cultured hepatocytes.
Cuihua Wang
2014-09-01
Full Text Available An incompressible fully developed laminar flow in a helical rectangular duct having finite pitch and curvature with temperature-dependent viscosity under heating condition is studied in this work. Both the cases of one wall heated and four walls heated are studied. The cross-sectional dimensions of the rectangular duct are 2a and 2b. The aspect ratio n=2b/2a is 0.5. Water is used as the fluid and Reynolds number (Re is varied in the range of 100 to 400. The secondary flow with temperature-dependent viscosity is enhanced markedly as compared to constant viscosity. An additional pair of vortices is obtained near the center of the outer wall at Re=400 for the model of four walls heated with temperature-dependent viscosity, y, while for constant viscosity, the appearance of two additional vortices near the outer wall cannot be found. Besides, the axial velocity decreases and the temperature increases at the central region of the rectangular duct when the temperature-dependent viscosity is considered. Due to the decrease of the viscosity near the walls, the friction factor obtained with temperature-dependent viscosity is lower than that of constant viscosity, while the convective heat transfer for temperature-dependent viscosity is significantly enhanced owing to the strengthened secondary flow. Especially for four heated walls, the effects of viscosity variation on the flow resistance and heat transfer are more significant.
Janssen, P. J. A.; Anderson, P. D.
2008-10-01
A boundary-integral method is presented for drop deformation between two parallel walls for non-unit viscosity ratio systems. To account for the effect of the walls the Green's functions are modified and all terms for the double-layer potential are derived. The full three-dimensional implementation is validated, and the model is shown to be accurate and consistent. The method is applied to study drop deformation in shear flow. An excellent match with small-deformation theory is found at low capillary numbers, and our results match with other BIM simulations for pressure-driven flows. For shear flow with moderate capillary numbers, we see that the behavior of a low-viscosity drop is similar to that of drop with a viscosity ratio of unity. High-viscosity drops, on the other hand, are prevented from rotating in shear flow, which results in a larger deformation, but less overshoot in the drop axes is observed. In contrast with unconfined flow, high-viscosity drops can be broken in shear flow between parallel plates; for low-viscosity drops the critical capillary number is higher in confined situations.
Elastic models for the non-Arrhenius viscosity of glass-forming liquids
Dyre, Jeppe; Christensen, Tage Emil; Olsen, Niels Boye
2006-01-01
on to review several related explanations for the non-Arrhenius viscosity. Most of these are also ‘elastic models’, i.e., they express the viscosity activation energy in terms of short-time elastic properties of the liquid. Finally, two alternative arguments for elastic models are given, a general solid......This paper first reviews the shoving model for the non-Arrhenius viscosity of viscous liquids. According to this model the main contribution to the activation energy of a flow event is the energy needed for molecules to shove aside the surrounding, an energy which is proportional...
Bahaya, Bernard
The aim of this thesis is to study the improvement of heat transfer in graphene-water nanofluids. Experiments were conducted with graphene nanoplatelets (GNP) to study the relative benefit of the thermal conductivity improvement in relationship to the potential detriment when considering the effect that more GNP dispersed in the water increases the viscosity of the resulting suspension relative to that of the water. A maximum enhancement ratio for GNP nanofluid thermal conductivity over water was 1.43 at a volume fraction of 0.014. Based upon GNP aspect ratios confirmed in sizing measurements, the DEM model presented by Chu et al., (2012) appears to describe the experimental results of this study when using a fitted interfacial resistance value of 6.25 E -8 m2 K W-1. The well-known Einstein viscosity model for spheres dispersed in fluids was shown to under predict the experimental data. Adjusting the intrinsic model term for spheres from a value of 2.5 to a fitted value of 1938 representative for the GNP of this study provided much closer agreement between measured and predicted values. Heat transfer is a nonlinear function of viscosity and thermal conductivity and heat transfer is predicted to decrease for GNP nanofluids when compared to water alone. Hence the use of nanofluids to enhance heat transfer processes appears not to be viable.
Temperature-Dependent Conformations of Model Viscosity Index Improvers
Ramasamy, Uma Shantini; Cosimbescu, Lelia; Martini, Ashlie
2015-05-01
Lubricants are comprised of base oils and additives where additives are chemicals that are deliberately added to the oil to enhance properties and inhibit degradation of the base oils. Viscosity index (VI) improvers are an important class of additives that reduce the decline of fluid viscosity with temperature [1], enabling optimum lubricant performance over a wider range of operating temperatures. These additives are typically high molecular weight polymers, such as, but not limited to, polyisobutylenes, olefin copolymer, and polyalkylmethacrylates, that are added in concentrations of 2-5% (w/w). Appropriate polymers, when dissolved in base oil, expand from a coiled to an uncoiled state with increasing temperature [2]. The ability of VI additives to increase their molar volume and improve the temperature-viscosity dependence of lubricants suggests there is a strong relationship between molecular structure and additive functionality [3]. In this work, we aim to quantify the changes in polymer size with temperature for four polyisobutylene (PIB) based molecular structures at the nano-scale using molecular simulation tools. As expected, the results show that the polymers adopt more conformations at higher temperatures, and there is a clear indication that the expandability of a polymer is strongly influenced by molecular structure.
Bulk viscosity for pion and nucleon thermal fluctuation in the hadron resonance gas model
Ghosh, Sabyasachi; Mohanty, Bedangdas
2016-01-01
We have calculated microscopically bulk viscosity of hadronic matter, where equilibrium thermodynamics for all hadrons in medium are described by Hadron Resonance Gas (HRG) model. Considering pions and nucleons as abundant medium constituents, we have calculated their thermal widths, which inversely control the strength of bulk viscosities for respective components and represent their in-medium scattering probabilities with other mesonic and baryonic resonances, present in the medium. Our calculations show that bulk viscosity increases with both temperature and baryon chemical potential, whereas viscosity to entropy density ratio decreases with temperature and with baryon chemical potential, the ratio increases first and then decreases. The decreasing nature of the ratio with temperature is observed in most of the earlier investigations with few exceptions. We find that the temperature dependence of bulk viscosity crucially depends on the structure of the relaxation time. Along the chemical freeze-out line in...
Improvement of the Blast Furnace Viscosity Prediction Model Based on Discrete Points Data
Guo, Hongwei; Zhu, Mengyi; Li, Xinyu; Guo, Jian; Du, Shen; Zhang, Jianliang
2015-02-01
Viscosity is considered to be a significant indicator of the metallurgical property of blast furnace slag. An improved model for viscosity prediction based on the Chou model was presented in this article. The updated model has optimized the selection strategy of distance algorithm and negative weights at the reference points. Therefore, the extensionality prediction disadvantage in the original model was ameliorated by this approach. The model prediction was compared with viscosity data of slags of compositions typical to BF operations obtained from a domestic steel plant. The results show that the approach can predict the viscosity with average error of 9.23 pct and mean standard deviation of 0.046 Pa s.
Ram Paras
2016-01-01
Full Text Available An attempt has been made to describe the effects of geothermal viscosity with viscous dissipation on the three dimensional time dependent boundary layer flow of magnetic nanofluids due to a stretchable rotating plate in the presence of a porous medium. The modelled governing time dependent equations are transformed a from boundary value problem to an initial value problem, and thereafter solved by a fourth order Runge-Kutta method in MATLAB with a shooting technique for the initial guess. The influences of mixed temperature, depth dependent viscosity, and the rotation strength parameter on the flow field and temperature field generated on the plate surface are investigated. The derived results show direct impact in the problems of heat transfer in high speed computer disks (Herrero et al. [1] and turbine rotor systems (Owen and Rogers [2].
Viscosity and Liquid Density of Asymmetric n-Alkane Mixtures: Measurement and Modelling
Queimada, António J.; Marrucho, Isabel M.; Coutinho, João A.P.
2005-01-01
Viscosity and liquid density Measurements were performed, at atmospheric pressure. in pure and mixed n-decane. n-eicosane, n-docosane, and n-tetracosane from 293.15 K (or above the melting point) up to 343.15 K. The viscosity was determined with a rolling ball viscometer and liquid densities with...... of state and a corresponding states model recently proposed for surface tension, viscosity, vapor pressure, and liquid densities of the series of n-alkanes. Advantages and shortcoming of these models are discussed....
Role of loading on head stability and effective neck stiffness and viscosity.
Simoneau, Martin; Denninger, Marc; Hain, Timothy C
2008-07-19
This experiment tests the hypothesis that loading the head would increase head stability. In particular, we hypothesized that an arrangement of the head so that muscle activation is required to counteract a load would significantly increase effective neck stiffness and viscosity, which would be associated with lower peak head angular velocity following abrupt force perturbations applied to the head. Seven young healthy subjects had their head loaded (preload) using a weight/pulley apparatus. Then, the head was pulled either forward or backward by dropping an additional weight onto the preload, causing an impulse of force followed by an increase in load. We recorded the applied force and head angular velocity. Neck viscoelastic properties as a function of loading were estimated by fitting experimental data to a second-order mathematical model of the head biomechanics. Across preloads varying from 2.22 to 8.89 N, peak head angular velocity decreased by 18.2% for the backward and by 19.9% for forward perturbations. As preload increased, simulated effective neck stiffness and viscosity significantly increased leading to lower peak angular velocity. These results demonstrated that loading reduces peak head angular velocity and that change in muscle stiffness and viscosity is a feasible explanation for this effect. We propose that reduction in peak head velocity could be caused by modulation of the strength of the vestibulo-collic reflex.
Size and temperature effects on the viscosity of water inside carbon nanotubes
Ye Hongfei
2011-01-01
Full Text Available Abstract The influences of the diameter (size of single-walled carbon nanotubes (SWCNTs and the temperature on the viscosity of water confined in SWCNTs are investigated by an "Eyring-MD" (molecular dynamics method. The results suggest that the relative viscosity of the confined water increases with increasing diameter and temperature, whereas the size-dependent trend of the relative viscosity is almost independent of the temperature. Based on the computational results, a fitting formula is proposed to calculate the size- and temperature- dependent water viscosity, which is useful for the computation on the nanoflow. To demonstrate the rationality of the calculated relative viscosity, the relative amount of the hydrogen bonds of water confined in SWCNTs is also computed. The results of the relative amount of the hydrogen bonds exhibit similar profiles with the curves of the relative viscosity. The present results should be instructive for understanding the coupling effect of the size and the temperature at the nanoscale.
Effective viscosity of puller-like microswimmers: a renormalization approach
Gluzman, Simon; Karpeev, Dmitry A.; Berlyand, Leonid V.
2013-01-01
Effective viscosity (EV) of suspensions of puller-like microswimmers (pullers), for example Chlamydamonas algae, is difficult to measure or simulate for all swimmer concentrations. Although there are good reasons to expect that the EV of pullers is similar to that of passive suspensions, analytical determination of the passive EV for all concentrations remains unsatisfactory. At the same time, the EV of bacterial suspensions is closely linked to collective motion in these systems and is biologically significant. We develop an approach for determining analytical EV estimates at all concentrations for suspensions of pullers as well as for passive suspensions. The proposed methods are based on the ideas of renormalization group (RG) theory and construct the EV formula based on the known asymptotics for small concentrations and near the critical point (i.e. approaching dense packing). For passive suspensions, the method is verified by comparison against known theoretical results. We find that the method performs much better than an earlier RG-based technique. For pullers, the validation is done by comparing them to experiments conducted on Chlamydamonas suspensions. PMID:24068178
Radwan, Asma; Zaid, Abdel Naser; Jaradat, Nidal; Odeh, Yousef
2017-04-01
The clinical implications of food-drug interactions may have to be taken seriously into account with oral drugs administration in order to minimize variations in drug bioavailability. Food intake may alter physiological changes in the pH and viscosity of the gastrointestinal lumen, which could affect the oral absorption of drugs. The aim of the present study was to have an insight on the effect of media parameters: viscosity and pHon the oral absorption of ciprofloxacin HCl from solid formulations using a model food: Corchorus olitorius (Jute) Soup. In vitro disintegration and dissolution rates of ciprofloxacin tablet were evaluated using compendia buffer media in the presence/absence of C. olitorius leaves. These in vitro data were then input to GastroPlus™ to predict ciprofloxacin absorption profiles under fasted and fed states. The present study demonstrated the significance of luminal pH and viscosity on the dissolution and disintegration of solid formulations following postprandial ingestion of the viscous soup. The tablets showed prolonged disintegration times and reduced dissolution rates in this soup, which could be attributed to the postprandial elevation in media viscosity and reduced solubility at elevated gastricpH. The predicted model under fed state showed no impact on AUC but prolonged Tmax and a decrease in Cmax. Concomitant intake of C. olitorius soup with ciprofloxacin might have negative effect on the rate of drug release from conventional immediate release tablets. Copyright © 2017 Elsevier B.V. All rights reserved.
Jain, Shweta, E-mail: jshweta09@gmail.com; Sharma, Prerana [Department of Physics, Ujjain Engineering College, Ujjain, M.P.456010 (India); Chhajlani, R. K. [School of Studies in Physics, Vikram University Ujjain, M. P. - 456010 (India)
2015-07-31
The Jeans instability of self-gravitating quantum plasma is examined considering the effects of viscosity, finite Larmor radius (FLR) corrections and rotation. The analysis is done by normal mode analysis theory with the help of relevant linearized perturbation equations of the problem. The general dispersion relation is obtained using the quantum magneto hydrodynamic model. The modified condition of Jeans instability is obtained and the numerical calculations have been performed to show the effects of various parameters on the growth rate of Jeans instability.
Kim, Sung-Gun; Yoo, Byoungseung
2015-01-01
Background: Although extensive literature is available on the viscosity of thickened beverages with food thickeners, no attempt has been made to study the effect of setting time on the viscosity of pudding-like cold-thickened beverages with xanthan gum (XG)-based thickeners by using a rheometer. In particular, it is of considerable practical…
Effect of Shear and Bulk Viscosities on Interacting Modified Chaplygin Gas Cosmology
Naji, J.; Pourhassan, B.; Amani, Ali R.
2014-12-01
In this paper, we study interacting modified Chaplygin gas (MCG) which has shear and bulk viscosities. We consider sign-changeable interaction between MCG and matter, then investigate the effects of shear and bulk viscosities on the cosmological parameters such as energy, density, Hubble expansion parameter, scale factor and deceleration parameter.
Effect of strong electrolytes on Edible oil Part II, Viscosity of maize oil ...
paras
Effect of Strong Electrolytes on Edible Oils Part III: Viscosity of canola oil in 1,4- dioxane in the presence of HCl, ... (BDH) are used without further purification. Canola oil was ... the procedure given elsewhere (Khan et al, 2005). The viscosity of ...
Kim, Sung-Gun; Yoo, Byoungseung
2015-01-01
Background: Although extensive literature is available on the viscosity of thickened beverages with food thickeners, no attempt has been made to study the effect of setting time on the viscosity of pudding-like cold-thickened beverages with xanthan gum (XG)-based thickeners by using a rheometer. In particular, it is of considerable practical…
The effect of viscosity on ad libitum food intake
Zijlstra, N.; Mars, M.; Wijk, de R.A.; Westerterp-Plantenga, M.; Graaf, de C.
2008-01-01
Background: Energy-yielding liquids elicit weak suppressive appetite responses and weak compensatory responses, suggesting that liquid calories might lead to a positive energy balance. However, data is often derived from foods differing in many characteristics other than viscosity. Objective: To
Effective viscosity of non-gravitactic Chlamydomonas Reinhardtii microswimmer suspensions
Mussler, Matthias; Peyla, Philippe; Wagner, Christian
2013-01-01
Active microswimmers are known to affect the macroscopic viscosity of suspensions in a more complex manner than passive particles. For puller-like microswimmers an increase in the viscosity has been observed. It has been suggested that the persistence of the orientation of the microswimmers hinders the rotation that is normally caused by the vorticity. It was previously shown that some sorts of algaes are bottom-heavy swimmers, i.e. their centre of mass is not located in the centre of the body. In this way, the algae affects the vorticity of the flow when it is perpendicular oriented to the axis of gravity. This orientation of gravity to vorticity is given in a rheometer that is equipped with a cone-plate geometry. Here we present measurements of the viscosity both in a cone-plate and a Taylor-Couette cell. The two set-ups yielded the same increase in viscosity although the axis of gravitation in the Taylor-Couette cell is parallel to the direction of vorticity. In a complementary experiment we tested the ori...
The effects of gold nanoparticles size and concentration on viscosity ...
The spindle was immersed and rotated in these gold nanofluids in the speed range from ... Viscosity of GNPs was measured at temperature of 37°C and at a gradually ... The incident light at 308 nm will lead to excitation of the surface plasmon ...
2011-01-01
Modeling the Thermodynamic and Transport Properties of Decahydronaphthalene/Propane Mixtures: Phase Equilibria , Density, and Viscosity Nathaniel...Decahydronaphthalene/Propane Mixtures: Phase Equilibria , Density, And Viscosity 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Keywords: phase equilibria ; modified Sanchez-Lacombe equation of state
Bianchi Type-Ⅲ String Cosmological Model with Bulk Viscosity in General Relativity
WANG Xing-Xiang
2005-01-01
The Bianchi type-Ⅲcosmological model for a cloud string with bulk viscosity are studied. To obtain a determinate solution, it is assumed that the coefficient of bulk viscosity is a power function of the scalar of expansion ζ = kθm and the shear scalar is proportional to scalar of expansion σ∝θ, which leads to the relation between metric potentials B = Cn. The physical features of the model are also discussed. It is found that the power index mhas significant influence on the string model. There is a "big bang" start in the model when m ≤ 1 but there is no the big-bang start when m ＞ 1. In the special case m = 0, the model reduces to the string model of constant coefficient of bulk viscosity that was the result previously given in the literature.
The Effect of Anisotropic Viscosity on Cold Fronts in Galaxy Clusters
ZuHone, J A; Markevitch, M; Stone, J M; Biffi, V
2014-01-01
Cold fronts--contact discontinuities in the intracluster medium (ICM) of galaxy clusters--should be disrupted by Kelvin-Helmholtz (K-H) instabilities due to the associated shear velocity. However, many observed cold fronts appear stable. This opens the possibility to place constraints on microphysical mechanisms that stabilize them, such as the ICM viscosity and/or magnetic fields. We performed exploratory high-resolution simulations of cold fronts arising from subsonic gas sloshing in cluster cores using the grid-based Athena MHD code, comparing the effects of isotropic Spitzer and anisotropic Braginskii viscosity (expected in a magnetized plasma). Magnetized simulations with full Braginskii viscosity or isotropic Spitzer viscosity reduced by a factor f ~ 0.1 are both in qualitative agreement with observations in terms of suppressing K-H instabilities. The RMS velocity and turbulence within the sloshing region is only modestly reduced by Braginskii viscosity. We also performed unmagnetized simulations with a...
THE EFFECT OF ADDITIVE ON THE VISCOSITY INDEX OF LUBRICATING OIL (ENGINE OIL
ONYEJI,
2011-03-01
Full Text Available The effects of four different additive formulations namely 5748, 801, 264 and 261 on the viscosity index of two lubricating oils (base oils namely 150N and 500N at two temperatures 400C and 1000C wereinvestigated. The base oils were blended with the additives in three different proportions of 100/4. 100/8 and 100/12. The results gave a viscosity index of 96 and 98 respectively for 150N and 500N withoutadditives. On the other hand, the addition of 12g of 261 additive formulations to 100cm3 of both base oils gave about 180% increase in kinematic viscosity at 400C, about 161% increase and 146% increase at1000C for 150N and 500N respectively. About 60% in viscosity index was achieved by 100/12 blend of 261 additives in 150N. The results revealed that 261 additive formulations gave the highest increase inviscosity in all proportions increasing as the weight of the additive increases. Generally, all the four additive formulations used mproved the viscosities of all the blends in all the proportions and at both temperatures. The blends can be classified as very high viscosity index being above 110. This means that they will undergo very little change in viscosity with temperature extremes and so can be considered to have stable viscosity.
Effects of powdered versus liquid barium on the viscosity of fluids used in modified swallow studies
Baron, J.; Alexander, T. [Univ. of Alberta, Dept. of Radiology, Edmonton, Alberta (Canada)
2003-06-01
To determine if the viscosity of thickened juice mixtures used in modified barium swallow studies significantly changes with the addition of powdered barium. We also describe a test formulation created using liquid barium, which has a negligible effect on juice viscosity. The viscosities of water and standardized honey- and nectar-consistency juices mixed with different amounts of powdered barium were measured by timing the laminar flow of a given initial hydrostatic head of fluid under gravity though an orifice of fixed diameter. Standardized juices were then mixed with a liquid formulation of barium and with measured quantities of water to produce viscosities that more closely equated with those of the standardized juices. With the addition of powdered barium, viscosity increased in all fluids, most markedly with the nectar-consistency juice. Liquid barium formulations maintained the viscosities of the original thickened juices. Rendering juices radio-opaque with barium powder results in dramatic increases in the viscosity of the resulting mixture and compromises diagnostic accuracy. Liquid barium preparations have the advantage that they can be rapidly and accurately dispensed by syringe, and their use does not significantly increase the viscosity of the preparation. (author)
Usmanov, Arcadi V.; Matthaeus, William H. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Goldstein, Melvyn L., E-mail: arcadi.usmanov@nasa.gov [Code 672, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2014-06-10
We have developed a three-fluid, three-dimensional magnetohydrodynamic solar wind model that incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating. The solar wind plasma is described as a system of co-moving solar wind protons, electrons, and interstellar pickup protons, with separate energy equations for each species. Numerical steady-state solutions of Reynolds-averaged solar wind equations coupled with turbulence transport equations for turbulence energy, cross helicity, and correlation length are obtained by the time relaxation method in the corotating with the Sun frame of reference in the region from 0.3 to 100 AU (but still inside the termination shock). The model equations include the effects of electron heat conduction, Coulomb collisions, photoionization of interstellar hydrogen atoms and their charge exchange with the solar wind protons, turbulence energy generation by pickup protons, and turbulent heating of solar wind protons and electrons. The turbulence transport model is based on the Reynolds decomposition and turbulence phenomenologies that describe the conversion of fluctuation energy into heat due to a turbulent cascade. In addition to using separate energy equations for the solar wind protons and electrons, a significant improvement over our previous work is that the turbulence model now uses an eddy viscosity approximation for the Reynolds stress tensor and the mean turbulent electric field. The approximation allows the turbulence model to account for driving of turbulence by large-scale velocity gradients. Using either a dipole approximation for the solar magnetic field or synoptic solar magnetograms from the Wilcox Solar Observatory for assigning boundary conditions at the coronal base, we apply the model to study the global structure of the solar wind and its three-dimensional properties, including embedded turbulence, heating, and acceleration throughout the heliosphere. The model results are
Set, Seng; Ford, David; Kita, Masakazu
2015-01-01
This research revealed that metal ions with different charges could significantly affect the viscosity of aqueous sodium carboxylmethylcellulose (CMC) solution. On the basis of an Ostwald viscometer, an improvised apparatus using a dropping ball for examining the viscosity of liquids/solutions has been developed. The results indicate that the…
Kustova, Elena V.; Kremer, Gilberto M.
2015-09-01
Shear viscosity coefficient is calculated for both equilibrium and strongly non-equilibrium state-to-state vibrational distributions taking into account increasing diameters of vibrationally excited molecules. Under conditions of local thermal equilibrium, the effect of vibrational excitation on the shear viscosity coefficient is found to be negligible for temperatures below 5000 K. For T > 10 000 K, the contribution of excited states becomes important. Under non-equilibrium conditions characteristic for shock heated and supersonic expanding flows vibrational level populations deviate strongly from the Boltzmann distribution. Nevertheless, estimated coupled effect of molecular size and non-Boltzmann distributions on the shear viscosity coefficient is negligible.
The effect of the salt viscosity on future evolution of the Gorleben salt diapir, Germany
Chemia, Zurab; Schmeling, H.; Koyi, H.
2009-01-01
for various salt rheologies. It is shown that the rheology of the salt plays a significant role in how and at which rate the anhydrite blocks sink within the diapir. The mobility of anhydrite blocks depends on the effective viscosity of salt which has to be lower than threshold value of around 1018–1019 Pa s....... Decreasing salt viscosity allows the previously “stationary” anhydrite blocks to sink. If the effective viscosity of salt in post-depositional stage of the Gorleben diapir falls below this threshold value, induced internal flow due to the present anhydrite layer might disturb any repository within the diapir....
The effect of the salt viscosity on future evolution of the Gorleben salt diapir, Germany
Chemia, Zurab; Schmeling, H.; Koyi, H.
2009-01-01
for various salt rheologies. It is shown that the rheology of the salt plays a significant role in how and at which rate the anhydrite blocks sink within the diapir. The mobility of anhydrite blocks depends on the effective viscosity of salt which has to be lower than threshold value of around 1018–1019 Pa s....... Decreasing salt viscosity allows the previously “stationary” anhydrite blocks to sink. If the effective viscosity of salt in post-depositional stage of the Gorleben diapir falls below this threshold value, induced internal flow due to the present anhydrite layer might disturb any repository within the diapir....
Effects of real viscosity on plasma liner formation and implosion from supersonic plasma jets
Schillo, Kevin; Cassibry, Jason; Hsu, Scott; PLX-Alpha Team
2015-11-01
The PLX- α project endeavors to study plasma liner formation and implosion by merging of a spherical array of plasma jets as a candidate standoff driver for magneto-inertial fusion (MIF). Smoothed particle hydrodynamics (SPH) is being used to model the liner formation and implosion processes. SPH is a meshless Lagrangian method to simulate fluid flows by dividing a fluid into a set of particles and using a summation interpolant function to calculate the properties and gradients for each of these particles. The SPH code was used to simulate test cases in which the number of plasma guns and initial conditions for the plasma were varied. Linear stabilizations were observed, but the possibility exists that this stabilization was due to the implementation of artificial viscosity in the code. A real viscosity model was added to our SPHC model using the Braginskii ion viscosity. Preliminary results for test cases that incorporate real viscosity are presented.
G P Singh; R V Deshpande; T Singh
2004-11-01
We have studied five-dimensional homogeneous cosmological models with variable and bulk viscosity in Lyra geometry. Exact solutions for the field equations have been obtained and physical properties of the models are discussed. It has been observed that the results of new models are well within the observational limit.
Naduvinamani, Neminath Bujappa; Apparao, Siddangouda; Gundayya, Hiremath Ayyappa; Biradar, Shivraj Nagshetty
2015-01-01
In this paper, a theoretical study of the effect of pressure dependent viscosity on couple stress squeeze film lubrication between rough parallel plates is analyzed on the basis of Barus experimental results...
Bulk viscosity of strange quark matter in density dependent quark mass model
J D Anand; N Chandrika Devi; V K Gupta; S Singh
2000-05-01
We have studied the bulk viscosity of strange quark matter in the density dependent quark mass model (DDQM) and compared results with calculations done earlier in the MIT bag model where , masses were neglected and ﬁrst order interactions were taken into account. We ﬁnd that at low temperatures and high relative perturbations, the bulk viscosity is higher by 2 to 3 orders of magnitude while at low perturbations the enhancement is by 1–2 order of magnitude as compared to earlier results. Also the damping time is 2–3 orders of magnitude lower implying that the star reaches stability much earlier than in MIT bag model calculations.
Vuksan, Vladimir; Jenkins, Alexandra L; Rogovik, Alexander L; Fairgrieve, Christopher D; Jovanovski, Elena; Leiter, Lawrence A
2011-11-01
The well-documented lipid-lowering effects of fibre may be related to its viscosity, a phenomenon that has been understudied, especially when fibre is given against the background of a typical North American (NA) diet. In this three-arm experiment, we compared the lipid-lowering effect of low-viscosity wheat bran (WB), medium-viscosity psyllium (PSY) and a high-viscosity viscous fibre blend (VFB), as part of a fibre intervention aimed at increasing fibre intake to recommended levels within the context of a NA diet in apparently healthy individuals. Using a randomised cross-over design, twenty-three participants (twelve males and eleven females; age 35 (SD 12) years; LDL-cholesterol (C) 2.9 (SEM 0.6) mmol/l) consuming a typical NA diet received a standard, fibre-enriched cereal, where approximately one-third of the fibre was either a low-viscosity (570 centipoise (cP)) WB, medium-viscosity (14,300 cP) PSY or a high-viscosity (136,300 cP) novel VFB, for 3 weeks separated by washout periods of ≥ 2 weeks. There were no differences among the treatments in the amount of food consumed, total dietary fibre intake, reported physical activity and body weight. Final intake of the WB, PSY and VFB was 10.8, 9.0 and 5.1 g, respectively. Reduction in LDL-C was greater with the VFB compared with the medium-viscosity PSY (-12.6 (SEM 3.5) %, P = 0.002) and low-viscosity WB (-14.6 (SEM 4.2) %, P = 0.003). The magnitude of LDL-C reduction showed a positive association with fibre apparent viscosity (r - 0.41, P = 0.001). Despite the smaller quantity consumed, the high-viscosity fibre lowered LDL-C to a greater extent than lower-viscosity fibres. These data support the inclusion of high-viscosity fibre in the diet to reduce plasma lipids among apparently healthy individuals consuming a typical NA diet.
A new and reliable model for predicting methane viscosity at high pressures and high temperatures
Ehsan Heidaryan; Jamshid Moghadasi; Amir Salarabadi
2010-01-01
In recent years,there has been an increase of interest in the flow of gases at relatively high pressures and high temperatures.Hydrodynamic calculation of the energy losses in the flow of gases in conduits,as well as through the porous media constituting natural petroleum reservoirs,requires knowledge of the viscosity of the fluid at the pressure and temperature involved.Although there are numerous publications concerning the viscosity of methane at atmospheric pressure,there appears to be little information available relating to the effect of pressure and temperature upon the viscosity.A survey of the literature reveals that the disagreements between published data on the viscosity of methane are common and that most investigations have been conducted over restricted temperature and pressure ranges.Experimental viscosity data for methane are presented for temperatures from 320 to 400 K and pressures from 3000 to 140000 kPa by using falling body viscometer.A summary is given to evaluate the available data for methane,and a comparison is presented for that data common to the experimental range reported in this paper.A new and reliable correlation for methane gas viscosity is presented.Predicted values are given for temperatures up to 400 K and pressures up to 140000 kPa with Average Absolute Percent Relative Error(EABS)of 0.794.
The effect of N-acetyl-L-cysteine on the viscosity of ileal neobladder mucus.
Schrier, B P; Lichtendonk, W J; Witjes, J A
2002-05-01
N-acetyl-L-cysteine (NAC) proved to be an effective mucolytic in pulmonary secretions. Our goal was to investigate the in vitro effect of NAC on viscosity of ileal neobladder mucus. The urine of a patient with an ileal neobladder was collected during the first 7 days postoperatively and stored in a refrigerator. After precipitation, the urine was decanted. The residue was stirred to a homogeneous suspension. To samples of 4.5 ml mucus, 0.5 ml NAC 10% was added. To the control sample, 0.5 ml water was added. The samples were incubated in a water bath at 37 degrees C for 5, 30 and 60 min. Viscosity was measured in the Bohlin VOR Rheometer. The viscosity of the ileal neobladder mucus decreased quickly after incubating with NAC 10%. Viscosity increased slightly after I h of incubation. The viscosity in the control sample was higher than in the other incubated samples. NAC was found to decrease the viscosity of ileal neobladder mucus, supporting the in vivo experience that NAC can be useful in patients with an ileal neobladder to facilitate the evacuation of mucus by decreasing viscosity.
Doorwar, Shashvat; Mohanty, Kishore K
2014-07-01
Immiscible displacement of viscous oil by water in a petroleum reservoir is often hydrodynamically unstable. Due to similarities between the physics of dielectric breakdown and immiscible flow in porous media, we extend the existing dielectric breakdown model to simulate viscous fingering patterns for a wide range of viscosity ratios (μ(r)). At low values of power-law index η, the system behaves like a stable Eden growth model and as the value of η is increased to unity, diffusion limited aggregation-like fractals appear. This model is compared with our two-dimensional (2D) experiments to develop a correlation between the viscosity ratio and the power index, i.e., η = 10(-5)μ(r)(0.8775). The 2D and three-dimensional (3D) simulation data appear scalable. The fingering pattern in 3D simulations at finite viscosity ratios appear qualitatively similar to the few experimental results published in the literature.
Shaing, K. C.; Sabbagh, S. A.
2016-07-01
Theory for neoclassical toroidal plasma viscosity has been developed to model transport phenomena, especially, toroidal plasma rotation for tokamaks with broken symmetry. Theoretical predictions are in agreement with the results of the numerical codes in the large aspect ratio limit. The theory has since been extended to include effects of finite aspect ratio and finite plasma β. Here, β is the ratio of the plasma thermal pressure to the magnetic field pressure. However, there are cases where the radial wavelength of the self-consistent perturbed magnetic field strength B on the perturbed magnetic surface is comparable to the width of the trapped particles, i.e., bananas. To accommodate those cases, the theory for neoclassical toroidal plasma viscosity is further extended here to include the effects of the finite banana width. The extended theory is developed using the orbit averaged drift kinetic equation in the low collisionality regimes. The results of the theory can now be used to model plasma transport, including toroidal plasma rotation, in real finite aspect ratio, and finite plasma β tokamaks with the radial wavelength of the perturbed symmetry breaking magnetic field strength comparable to or longer than the banana width.
Power-law electrokinetic behavior as a direct probe of effective surface viscosity
Uematsu, Yuki; Netz, Roland R.; Bonthuis, Douwe Jan
2017-02-01
An exact solution to the Poisson-Boltzmann and Stokes equations is derived to describe the electric double layer with inhomogeneous dielectric and viscosity profiles in a lateral electric field. In the limit of strongly charged surfaces and low salinity, the electrokinetic flow magnitude follows a power law as a function of the surface charge density. Remarkably, the power-law exponent is determined by the interfacial dielectric constant and viscosity, the latter of which has eluded experimental determination. Our approach provides a novel method to extract the effective interfacial viscosity from standard electrokinetic experiments. We find good agreement between our theory and experimental data.
Andhariya, Nidhi; Chudasama, Bhupendra; Patel, Rajesh; Upadhyay, R V; Mehta, R V
2008-07-01
In the present investigation we report the effect of capillary diameter and the direction of applied magnetic field on the rotational viscosity of water and kerosene based ferrofluids. We found that changes in the field induced rotational viscosity are larger in the case of water based magnetic fluid than that of kerosene based fluid. The field induced rotational viscosity is found to be inversely proportional to the capillary diameter and it falls exponentially as a function of the angle between the direction of field and vorticity of flow. Magnetophoretic mobility and hydrodynamic volume fraction of nanomagnetic particles are determined for above cases.
Modified expression for the effective viscosity in the semi-dilute shear flows of fiber suspension
ZHANG Lingxin; LIN Jianzhong; SHI Xing
2004-01-01
The available expressions for the effective viscosity can not provide good predictions compared with the experiment data measured in the semi-dilute shear flows of fiber suspension with small aspect ratio. The departure of the theoretical prediction from the measured data increases with the decrease of the fiber aspect ratio. Therefore, by experiment for the fiber with 20 μm diameter, a new expression for the effective viscosity in the semi-dilute shear flows of fiber suspension with small aspect ratio is proposed, the relationship between the shear viscosity of fiber suspensions and the fiber concentration is given. The results show that the effective viscosity is not a linear function of the fiber concentration.
Practical modeling of acoustic losses in air due to heat conduction and viscosity
Christensen, René; Juhl, Peter Møller; Cutanda Henríquez, Vicente
2008-01-01
Accurate acoustics models of small devices with cavities and narrow slits and ducts should include the socalled boundary layer attenuation caused by thermal conduction and viscosity. The purpose of this paper is to present and compare different methods for including these loss mechanisms in analy......Accurate acoustics models of small devices with cavities and narrow slits and ducts should include the socalled boundary layer attenuation caused by thermal conduction and viscosity. The purpose of this paper is to present and compare different methods for including these loss mechanisms...
Effect of Lubricant Viscosity and Surface Roughness on Coefficient of Friction in Rolling Contact
S.G. Ghalme
2013-12-01
Full Text Available The main objective of this paper is to investigate the effect of surface roughness and lubricant viscosity on coefficient of friction in silicon nitride- steel rolling contact. Two samples of silicon nitride with two different values of surface roughness were tested against steel counter face. The test was performed on four ball tester in presence of lubricant with two different values of viscosity. Taguchi technique a methodology in design of experiment implemented to plan the experimentation and same is utilized to evaluate the interacting effect of surface roughness and lubricant viscosity. Analysis of experimental results presents a strong interaction between surface roughness and lubricant viscosity on coefficient of friction in rolling contact.
Numerical modelling of melting and settling of an encapsulated PCM using variable viscosity
Kasibhatla, Raghavendra Rohith; König-Haagen, Andreas; Rösler, Fabian; Brüggemann, Dieter
2016-10-01
Thermal energy storage units using macro-encapsulated PCM in industrial and residential applications are contemporary due to better efficiency during charging and discharging. This article focuses on numerical modelling of the melting process in a macro-encapsulated PCM. Accounting the non-linear enthalpy-temperature relation and ramping down the velocity in solid phase is therefore fundamental. In the present article the variable viscosity method is implemented to ramp down the solid velocity and allow settling of the solid phase. This complete numerical model of melting and settling of PCM in a capsule is implemented in OpenFOAM. The numerical results for different solid viscosities are validated with experiments and show good agreement. The influence of the solid viscosity value and the pressure-velocity convergence is studied. It is observed that the pressure-velocity convergence only plays a greater role in the case where the computation of the exact solid velocity is required.
Afrand, Masoud; Abedini, Ehsan; Teimouri, Hamid
2017-03-01
In this paper, the effect of dispersion of magnesium oxide nanoparticles on viscosity of a mixture of water and ethylene glycol (50-50% vol.) was examined experimentally. Experiments were performed for various nanofluid samples at different temperatures and shear rates. Measurements revealed that the nanofluid samples with volume fractions of less than 1.5% had Newtonian behavior, while the sample with volume fraction of 3% showed non-Newtonian behavior. Results showed that the viscosity of nanofluids enhanced with increasing nanoparticles volume fraction and decreasing temperature. Results of sensitivity analysis revealed that the viscosity sensitivity of nanofluid samples to temperature at higher volume fractions is more than that of at lower volume fractions. Finally, because of the inability of the existing model to predict the viscosity of MgO/EG-water nanofluid, an experimental correlation has been proposed for predicting the viscosity of the nanofluid.
CHANG Cui-qing; CHEN Yan-bo; CHEN Zhi-min; ZHANG Lan-tao
2010-01-01
Background The consumption of carbohydrate-electrolyte beverages (CEs) has been known to be more effective than plain water for recovery from dehydration. This phenomenon suggests that the ingestion of CEs after dehydration is better than water for maintaining body fluid and plasma volume, and for the recovery from hemoconcentration and high blood viscosity as well. High blood viscosity causes infarction and other cardiovascular events. In this study, CE was compared with water and tea for the ability to reduce increased blood viscosity after dehydration.Methods A crossover random control study was conducted to assess the effectiveness of three beverages for rehydration and decreasing of blood viscosity. Following exercise-induced dehydration of 2.2% of body weight in a permanent warm environment, 10 male subjects rested in a thermoneutral environment for 3 hours (rehydration period,REP). The subjects ingested test beverages equal to their body weight loss during the first 20 minutes in REP. Blood and urine samples were obtained throughout the experiments to assess the rehydration effect.rate was significantly greater for CE ((77.0+3.9)%) than water ((61.2±3.4)%) and tea ((60.5±3.7)%) for 3 hours of rest in REP.Conclusions The recovery from high blood viscosity induced by dehydration was higher with CE consumption than with water or tea. These results suggest that CE is useful for normalizing increased blood viscosity due to exercise-induced dehydration.
A mathematical model for the movement of food bolus of varying viscosities through the esophagus
Tripathi, Dharmendra
2011-09-01
This mathematical model is designed to study the influence of viscosity on swallowing of food bolus through the esophagus. Food bolus is considered as viscous fluid with variable viscosity. Geometry of esophagus is assumed as finite length channel and flow is induced by peristaltic wave along the length of channel walls. The expressions for axial velocity, transverse velocity, pressure gradient, volume flow rate and stream function are obtained under the assumptions of long wavelength and low Reynolds number. The impacts of viscosity parameter on pressure distribution, local wall shear stress, mechanical efficiency and trapping are numerically discussed with the help of computational results. On the basis of presented study, it is revealed that swallowing of low viscous fluids through esophagus requires less effort in comparison to fluids of higher viscosity. This result is similar to the experimental result obtained by Raut et al. [1], Dodds [2] and Ren et al. [3]. It is further concluded that the pumping efficiency increases while size of trapped bolus reduces when viscosity of fluid is high.
The Effect of Variable Viscosities on Micropolar Flow of Two Nanofluids
Nadeem, S.; Ahmed, Z.; Saleem, S.
2016-12-01
A study of nanofluids is carried out that reveals the effect of rotational inertia and other physical parameters on the heat transfer and fluid flow. Temperature-dependent dynamic viscosity makes the microrotation viscosity parameter and the micro inertia density variant as well. The governing nonlinear partial differential equations are converted into a set of nonlinear ordinary differential equations by introducing suitable similarity transformations. These reduced nonlinear differential equations are then solved numerically by Keller-box method. The obtained numerical and graphical result discloses many interesting behaviour of nanofluids. It is seen that the temperature gradient decreases with the increase in viscosity parameter. Also, it is observed that with the fixed values of micropolar parameter and viscosity parameter, the velocity gradient near the wall increases with increasing values of solid particle volume fraction parameter. A suitable comparison of results is also presented in this study.
Viscosity methods for multiscale financial models with stochastic volatility
Bardi, Martino; Cesaroni, Annalisa; Ghilli, Daria; Scotti, Andrea
2014-01-01
Parallel session; International audience; Introduction on models Financial models and stochastic volatility, Gaussian or with jumps Fast stochastic volatility Part 1 Control systems with random parameters and multiple scales The Hamilton-Jacobi-Bellman approach to Singular Perturbations I Tools I Assumptions I A convergence result Applications to finance Part 2 Large deviations for small time to maturity: see also Daria Ghilli's poster tomorrow
Chandel S; Ram Shri
2016-03-01
The paper deals with the study of particle creation and bulk viscosity in the evolution of spatially homogeneous and anisotropic Bianchi type-V cosmological models in the framework of Saez–Ballester theory of gravitation. Particle creation and bulk viscosity are considered as separate irreversible processes. The energy–momentum tensor is modified to accommodate the viscous pressure and creation pressure which is associated with the creation of matter out of gravitational field. A special law of variation of Hubble parameter is applied to obtain exact solutions of field equations in two types of cosmologies, one with power-law expansion and the other with exponential expansion. Cosmological model with power-law expansion has a Big-Bang singularity at time $t = 0$, whereas the model with exponential expansion has no finite singularity. We study bulk viscosity and particle creation in each model in four different cases. The bulk viscosity coefficient is obtained for full causal, Eckart’s and truncated theories. All physical parameters are calculated and thoroughly discussed in both models.
Modifying the pom-pom model for extensional viscosity overshoots
Hawke, L. D. G.; Huang, Qian; Hassager, Ole
2015-01-01
) strongly accelerated stress relaxation upon cessation of the flow beyond the overshoot. Within the context of our model, these overshoots originate from entanglement stripping (ES) during the processes of normal chain retraction and branch point withdrawal. We demonstrate that, for a single mode......, the predictions of our overshoot model are qualitatively consistent with experimental data. To provide a quantitative fit, we represent an industrial melt by a superposition of several individual modes. We showt hat a minimal version of our model, in which ES due to normal chain retraction is omitted, can provide...
Flow of an Eyring-Powell Model Fluid between Coaxial Cylinders with Variable Viscosity
Azad Hussain
2013-01-01
Full Text Available We consider the flow of Eyring-Powell model fluid in the annulus between two cylinders whose viscosity depends upon the temperature. We consider the steady flow in the annulus due to the motion of inner cylinder and constant pressure gradient. In the problem considered the flow is found to be remarkedly different from that for the incompressible Navier-Stokes fluid with constant viscosity. An analytical solution of the nonlinear problem is obtained using homotopy analysis method. The behavior of pertinent parameters is analyzed and depicted through graphs.
Zhang Peng
2015-11-01
Full Text Available Hydrophobically associating polyacrylamide (HAPAM is considered to be a promising candidate for polymer flooding because of its excellent apparent viscosifying capability. Compared with partially hydrolyzed polyacrylamide (HPAM, the resistance factor and residual resistance factor caused by HAPAM tend to be higher. However, the effective viscosity of HAPAM is lower than that of conventional polymer at a concentration of 2 000 mg/L. The dynamic retention capacity of HAPAM is about 2.3 times that of HPAM. The oil displacement efficiency of HAPAM is lower than that of conventional polymer at a concentration of 2 000 mg/L in the homogeneous sandpack model. The oil displacement efficiency of HAPAM is higher than that of HPAM only in the heterogeneous model (permeability ratio 2.8. Neither high nor low permeability ratios are good for the oil displacement efficiency of HAPAM.
Lagogianni, A. E.; Krausser, J.; Evenson, Z.; Samwer, K.; Zaccone, A.
2016-08-01
An analytical framework is proposed to describe the elasticity, viscosity and fragility of metallic glasses in relation to their atomic-level structure and the effective interatomic interaction. The bottom-up approach starts with forming an effective Ashcroft-Born-Mayer interatomic potential based on Boltzmann inversion of the radial distribution function g (r) and on fitting the short-range part of g (r) by means of a simple power-law approximation. The power exponent λ represents a global repulsion steepness parameter. A scaling relation between atomic connectivity and packing fraction Z˜ {φ1+λ} is derived. This relation is then implemented in a lattice-dynamical model for the high-frequency shear modulus where the attractive anharmonic part of the effective interaction is taken into account through the thermal expansion coefficient which maps the ϕ-dependence into a T-dependence. The shear modulus as a function of temperature calculated in this way is then used within the cooperative shear model of the glass transition to yield the viscosity of the supercooled melt as a double-exponential function of T across the entire Angell plot. The model, which has only one adjustable parameter (the characteristic atomic volume for high-frequency cage deformation) is tested against new experimental data of ZrCu alloys and provides an excellent one-parameter description of the viscosity down to the glass transition temperature.
Modifying the pom-pom model for extensional viscosity overshoots
Hawke, L. D. G.; Huang, Qian; Hassager, Ole;
2015-01-01
We have developed a variant of the pom-pom model that qualitatively describes two surprising features recently observed in filament stretching rheometer experiments of uniaxial extensional flow of industrial branched polymer resins: (i) Overshoots of the transient stress during steady flow and (ii......) strongly accelerated stress relaxation upon cessation of the flow beyond the overshoot. Within the context of our model, these overshoots originate from entanglement stripping (ES) during the processes of normal chain retraction and branch point withdrawal. We demonstrate that, for a single mode...... a reasonable, but not perfect, fit to the data. With regard the stress relaxation after (kinematically) steady flow, we demonstrate that the differential version of tube orientation dynamics in the original pom-pom model performs anomalously. We discuss the reasons for this and suggest a suitable alternative....
Viscosity solutions for a polymer crystal growth model
Cardaliaguet, Pierre; Monteillet, Aurélien
2010-01-01
We prove existence of a solution for a polymer crystal growth model describing the movement of a front $(\\Gamma(t))$ evolving with a nonlocal velocity. In this model the nonlocal velocity is linked to the solution of a heat equation with source $\\delta_\\Gamma$. The proof relies on new regularity results for the eikonal equation, in which the velocity is positive but merely measurable in time and with H\\"{o}lder bounds in space. From this result, we deduce \\textit{a priori} regularity for the front. On the other hand, under this regularity assumption, we prove bounds and regularity estimates for the solution of the heat equation.
Viscosity solutions for a polymer crystal growth model
Cardaliaguet, Pierre; Ley, Olivier; Monteillet, Aurélien
2011-01-01
International audience; We prove existence of a solution for a polymer crystal growth model describing the movement of a front $(\\Gamma(t))$ evolving with a nonlocal velocity. In this model the nonlocal velocity is linked to the solution of a heat equation with source $\\delta_\\Gamma$. The proof relies on new regularity results for the eikonal equation, in which the velocity is positive but merely measurable in time and with H\\"{o}lder bounds in space. From this result, we deduce \\textit{a pri...
Ling Miao
2015-10-01
Full Text Available In this paper we study the effects of variable viscosity and thermal conductivity on the heat transfer in the pressure-driven fully developed flow of a slurry (suspension between two horizontal flat plates. The fluid is assumed to be described by a constitutive relation for a generalized second grade fluid where the shear viscosity is a function of the shear rate, temperature and concentration. The heat flux vector for the slurry is assumed to follow a generalized form of the Fourier’s equation where the thermal conductivity k depends on the temperature as well as the shear rate. We numerically solve the governing equations of motion in the non-dimensional form and perform a parametric study to see the effects of various dimensionless numbers on the velocity, volume fraction and temperature profiles. The different cases of shear thinning and thickening, and the effect of the exponent in the Reynolds viscosity model, for the temperature variation in viscosity, are also considered. The results indicate that the variable thermal conductivity can play an important role in controlling the temperature variation in the flow.
Effect of viscosity and wall heat conduction on shock attenuation in narrow channels
Deshpande, A.; Puranik, B.
2016-07-01
In the present work, the effects due to viscosity and wall heat conduction on shock propagation and attenuation in narrow channels are numerically investigated. A two-dimensional viscous shock tube configuration is simulated, and heat conduction in the channel walls is explicitly included. The simulation results indicate that the shock attenuation is significantly less in the case of an adiabatic wall, and the use of an isothermal wall model is adequate to take into account the wall heat conduction. A parametric study is performed to characterize the effects of viscous forces and wall heat conduction on shock attenuation, and the behaviour is explained on the basis of boundary layer formation in the post-shock region. A dimensionless parameter that describes the shock attenuation is correlated with the diaphragm pressure ratio and a dimensionless parameter which is expressed using the characteristic Reynolds number and the dimensionless shock travel.
Study of the Viscosity of Mold Flux Based on the Vogel-Fulcher-Tammann (VFT) Model
Zhou, Lejun; Wang, Wanlin
2017-02-01
Viscosity is one of the most important properties of mold flux and affects the process of continuous casting significantly. In order to describe the variation of viscosity of mold flux accurately in a wide range of temperature occurring in the casting mold, a non-Arrhenius Vogel-Fulcher-Tammann (VFT) model was adopted in this study. The results showed that the adjusted coefficient of determination (Adj. R 2) of non-Arrhenius VFT Model ranges from 0.92 to 0.96, which suggests this model could be well adapted to predict the relationship between viscosity and temperature of mold flux. The temperature at which viscosity becomes infinite, T VFT, increased with the addition of Cr2O3 and improvement of basicity, while it decreased with the addition of B2O3, as it was determined by both the degree of polymerization of the melt structure and crystallization behavior of the melt. Also, the pseudo-activation energy, E VFT, of Samples 1 to 5 was 60.1 ± 3.6, 94.7 ± 14.9, 101.7 ± 19.0, 38.0 ± 4.8, and 32.4 ± 4.0 kJ/mol, respectively; it increased with the addition of Cr2O3 and B2O3, but deceased with the increase of basicity.
Joamin Gonzalez-Gutierrez
2016-05-01
Full Text Available The viscosity of feedstock materials is directly related to its processability during injection molding; therefore, being able to predict the viscosity of feedstock materials based on the individual properties of their components can greatly facilitate the formulation of these materials to tailor properties to improve their processability. Many empirical and semi-empirical models are available in the literature that can be used to predict the viscosity of polymeric blends and concentrated suspensions as a function of their formulation; these models can partly be used also for metal injection molding binders and feedstock materials. Among all available models, we made a narrow selection and used only simple models that do not require knowledge of molecular weight or density and have parameters with physical background. In this paper, we investigated the applicability of several of these models for two types of feedstock materials each one with different binder composition and powder loading. For each material, an optimal model was found, but each model was different; therefore, there is not a universal model that fits both materials investigated, which puts under question the underlying physical meaning of these models.
Bianchi Type-Ⅲ String Cosmological Model With Bulk Viscosity and Magnetic Field
WANG Xing-Xiang
2006-01-01
@@ The Bianchi type-Ⅲ cosmological model for a cloud string in the presence of bulk viscosity and magnetic field are presented. To obtain the determinate model it is assumed that there is an equation of state ρ = kλ and the scalar of expansion is proportional to the shear scalar θ∝σ, which leads to a relation between metric potentials B = mCn. The physical and geometric aspects of the model are also discussed. The model describes a shearing non-rotating continuously expanding universe with a big-bang start. In the absence of magnetic field, it reduces to the string model with bulk viscosity that was previously given in the literature.
Flow-induced agitations create a granular fluid: Effective viscosity and fluctuations
Nichol, Kiri; van Hecke, Martin
2012-06-01
We fluidize a granular medium with localized stirring in a split-bottom shear cell. We probe the mechanical response of quiescent regions far from the main flow by observing the vertical motion of cylindrical probes rising, sinking, and floating in the grains. First, we find that the probe motion suggests that the granular material behaves in a liquid-like manner: high-density probes sink and low-density probes float at the depth given by Archimedes’ law. Second, we observe that the drag force on moving probes scales linearly with their velocity, which allows us to define an effective viscosity for the system. This effective viscosity is inversely proportional to the rotation rate of the disk which drives the split bottom flow. Moreover, the apparent viscosity depends on radius and mass of the probe: despite the linear dependence of the drag forces on sinking speed of the probe, the granular medium is not simply Newtonian, but exhibits a more complex rheology. The decrease of viscosity with filling height of the cell, combined with the poor correlation between local strain rate and viscosity, suggests that the fluid-like character of the material is set by agitations generated in the stirred region: the relation between applied stress and observed strain rate in one location depends on the strain rate in another location. We probe the nature of the granular fluctuations that we believe mediates these nonlocal interactions by characterizing the small and random up and down motion that the probe experiences. These Gaussian fluctuations exhibit a mix of diffusive and subdiffusive behavior at short times and saturate at a value of roughly 1/10th of a grain diameter longer times, consistent with the picture of a random walker in a potential well. The product of crossover time and effective viscosity is constant, evidencing a direct link between fluctuations and viscosity.
Han, Chen; Chen, Mao; Zhang, Weidong; Zhao, Zhixing; Evans, Tim; Zhao, Baojun
2016-10-01
Metallurgical properties of slag are determined to a great extent by its viscosity. High-temperature viscosity measurements are time-consuming and expensive. It is necessary to develop an accurate viscosity model for blast furnace slag in the SiO2-Al2O3-CaO-MgO system using reliable viscosity data. This paper describes a systemic evaluation procedure to determine the viscosity data to be used for model development. 1780 viscosity data from 10 to 65 wt pct SiO2, 3.5 to 40 wt pct Al2O3, 2 to 60 wt pct CaO, and 2 to 38 wt pct MgO in the SiO2-Al2O3-CaO-MgO system have been accepted for model evaluation after critical reviews. The existing 14 viscosity models in SiO2-Al2O3-CaO-MgO system is also reviewed and evaluated. Based on the structure of alumina-silicate slag and evaluated viscosity data, a new viscosity model has been proposed for the system SiO2-Al2O3-CaO-MgO. A new term "probability," based on the basic oxide and electronegativity, is introduced to calculate the integral activation energy of slag. The model has been evaluated and compared with existing viscosity models in three different composition ranges in SiO2-Al2O3-CaO-MgO system for different applications. The new model reports an outstanding agreement between predictions and experimental data. The industrial implications of the new model have also been discussed in ironmaking and steelmaking processes.
Effect of viscosity ratio on the motion of drops flowing on an inclined surface
Aberuee, M.; Mortazavi, S.
2017-06-01
The flow of two-dimensional drops on an inclined channel is studied by numerical simulations at finite Reynolds numbers. The effect of viscosity ratio on the behaviour of the two-phase medium is examined. The flow is driven by the acceleration due to gravity, and there is no pressure gradient along the flow direction. An implicit version of the finite difference/front-tracking method was developed and used in the present study. The lateral migration of a drop is studied first. It is found that the equilibrium position of a drop moves away from the channel floor as the viscosity ratio increases. However, the trend reverses beyond a certain viscosity ratio. Simulations with 40 drops in a relatively large channel show that there exists a limiting viscosity ratio where the drops behave like solid particles, and the effect of internal circulation of drops becomes negligible. This limiting condition resembles the granular flow regime except that the effect of interstitial fluid is present. The limiting viscosity ratio depends on the flow conditions (80 for Re=10 , and 200 for Re=20 ). There are two peaks in the areal fraction distribution of drops across the channel which is different from granular flow regime. It is also found that the peak in areal fraction distribution of drops moves away from the channel floor as the inclination angle of the channel increases.
Antibacterial and Antibiofilm Effect of Low Viscosity Chitosan against Staphylococcus epidermidis
Inger Sofie Dragland
2016-01-01
Full Text Available Aim. The aim of this study was to investigate the antibacterial and antibiofilm properties of low viscosity chitosan on S. epidermidis growth and biofilm formation. Methods and Results. The antibacterial and antibiofilm properties were investigated, during both planktonic growth and biofilm formation. This was performed using different concentrations in media and by coating on polystyrene surfaces. In addition, the bactericidal effect was investigated using a modified direct contact test. The results showed that low viscosity chitosan in media had both a bacteriostatic and bactericidal effect on planktonic growth and biofilm formation of S. epidermidis in a concentration dependent manner. Polystyrene discs coated with chitosan reduced both early biofilm formation (6 h and late biofilm formation (18 h, as confirmed by scanning electron microscopy. The modified direct contact test showed a bactericidal effect. Conclusion. This study demonstrated that low viscosity chitosan has a bacteriostatic and bactericidal activity against S. epidermidis and that the activity is dependent on the amount of chitosan added. In addition, low viscosity chitosan reduced biofilm formation both when added to media and when coated on polystyrene surfaces. Significance and Impact of Study. Low viscosity chitosan could be a contribution to new treatment approaches of biofilm-related infections of S. epidermidis.
Effects of viscosity on shock-induced damping of an initial sinusoidal disturbance
无
2010-01-01
A lack of reliable data treatment method has been for several decades the bottleneck of viscosity measurement by disturbance amplitude damping method of shock waves.In this work the finite difference method is firstly applied to obtain the numerical solutions for disturbance amplitude damping behavior of sinusoidal shock front in inviscid and viscous flow.When water shocked to 15 GPa is taken as an example,the main results are as follows:(1) For inviscid and lower viscous flows the numerical method gives results in good agreement with the analytic solutions under the condition of small disturbance(a0/λ=0.02);(2) For the flow of viscosity beyond 200 Pa s(η=κ) the analytic solution is found to overestimate obviously the effects of viscosity.It is attributed to the unreal pre-conditions of analytic solution by Miller and Ahrens;(3) The present numerical method provides an effective tool with more confidence to overcome the bottleneck of data treatment when the effects of higher viscosity in experiments of Sakharov and flyer impact are expected to be analyzed,because it can in principle simulate the development of shock waves in flows with larger disturbance amplitude,higher viscosity,and complicated initial flow.
Avelino, Arturo
2008-01-01
We present and constrain a cosmological model where the only component is a pressureless fluid with bulk viscosity as an explanation for the present accelerated expansion of the universe. We study the particular model of a bulk viscosity coefficient proportional to the Hubble parameter. The model is constrained using the SNe Ia Gold 2006 sample, the Cosmic Microwave Background (CMB) shift parameter R, the Baryon Acoustic Oscillation (BAO) peak A and the Second Law of Thermodynamics (SLT). It was found that this model is in agreement with the SLT using only the SNe Ia test. However when the model is constrained using the three cosmological tests together (SNe+CMB+BAO) we found: 1.- The model violates the SLT, 2.- It predicts a value of H_0 \\approx 53 km sec^{-1} Mpc^{-1} for the Hubble constant, and 3.- We obtain a bad fit to data with a \\chi^2_{min} \\approx 532. These results indicate that this model is viable just if the bulk viscosity is triggered in recent times.
Noreen Sher Akbar; S. Nadeem
2012-01-01
Non-Newtonian fluid model for blood flow through a tapered artery with a stenosis and variable viscosity by modeling blood as Jeffrey fluid has been studied in this paper. The Jeffrey fluid has two parameters, the relaxation time A1 and retardation time A2. The governing equations are simplified using the case of mild stenosis. Perturbation method is used to solve the resulting equations. The effects of non-Newtonian nature of blood on velocity profile, temperature profile, wall shear stress, shearing stress at the stenotsis throat and impedance of the artery are discussed. The results for Newtonian fluid are obtained as special case from this model.
Effect of non-Newtonian viscosity on the fluid-dynamic characteristics in stenotic vessels
Huh, Hyung Kyu; Ha, Hojin; Lee, Sang Joon
2015-08-01
Although blood is known to have shear-thinning and viscoelastic properties, the effects of such properties on the hemodynamic characteristics in various vascular environments are not fully understood yet. For a quantitative hemodynamic analysis, the refractive index of a transparent blood analogue needs to be matched with that of the flowing conduit in order to minimize the errors according to the distortion of the light. In this study, three refractive index-matched blood analogue fluids with different viscosities are prepared—one Newtonian and two non-Newtonian analogues—which correspond to healthy blood with 45 % hematocrit (i.e., normal non-Newtonian) and obese blood with higher viscosity (i.e., abnormal non-Newtonian). The effects of the non-Newtonian rheological properties of the blood analogues on the hemodynamic characteristics in the post-stenosis region of an axisymmetric stenosis model are experimentally investigated using particle image velocimetry velocity field measurement technique and pathline flow visualization. As a result, the centerline jet flow from the stenosis apex is suppressed by the shear-thinning feature of the blood analogues when the Reynolds number is smaller than 500. The lengths of the recirculation zone for abnormal and normal non-Newtonian blood analogues are 3.67 and 1.72 times shorter than that for the Newtonian analogue at Reynolds numbers smaller than 200. The Reynolds number of the transition from laminar to turbulent flow for all blood analogues increases as the shear-thinning feature increases, and the maximum wall shear stresses in non-Newtonian fluids are five times greater than those in Newtonian fluids. However, the shear-thinning effect on the hemodynamic characteristics is not significant at Reynolds numbers higher than 1000. The findings of this study on refractive index-matched non-Newtonian blood analogues can be utilized in other in vitro experiments, where non-Newtonian features dominantly affect the flow
The effect of N-acetyl-L-cysteine on the viscosity of ileal neobladder mucus.
Schrier, B.P.; Lichtendonk, W.J.; Witjes, J.A.
2002-01-01
N-acetyl-L-cysteine (NAC) proved to be an effective mucolytic in pulmonary secretions. Our goal was to investigate the in vitro effect of NAC on viscosity of ileal neobladder mucus. The urine of a patient with an ileal neobladder was collected during the first 7 days postoperatively and stored in a
The effect of N-acetyl-L-cysteine on the viscosity of ileal neobladder mucus.
Schrier, B.P.; Lichtendonk, W.J.; Witjes, J.A.
2002-01-01
N-acetyl-L-cysteine (NAC) proved to be an effective mucolytic in pulmonary secretions. Our goal was to investigate the in vitro effect of NAC on viscosity of ileal neobladder mucus. The urine of a patient with an ileal neobladder was collected during the first 7 days postoperatively and stored in a
Effect of viscosity on material behavior in friction stir welding process
ZHANG Hong-wu; ZHANG Zhao; BIE Jun; ZHOU Lei; CHEN Jin-tao
2006-01-01
Temperature-dependent elastic viscoplastic material model was used for the numerical simulation of the friction stir welding process. The non-elastic response of the rate-dependent material in the large deformation problems was calculated by using the closest point algorithm. The numerical results show that the shape of the equivalent plastic strain looks like onion rings and the spacing of the rings is approximately equal to the forward movement of the tool in one rotation. The equivalent plastic strain is increased with the increase of viscosity coefficient due to the increase of friction stress in the pin-plate interface. The region which is influenced by the rotating tool is decreased with the decrease of viscosity coefficient. The radial and circumferential stresses in front of the pin are greater than the ones behind the pin. This difference can be reduced with the decrease of viscosity.
Markesteijn, A.P.; Hartkamp, R.; Luding, S.; Westerweel, J.
2012-01-01
The viscosity-temperature relation is determined for the water models SPC/E, TIP4P, TIP4P/Ew, and TIP4P/2005 by considering Poiseuille flow inside a nano-channel using molecular dynamics. The viscosity is determined by fitting the resulting velocity profile (away from the walls) to the continuum sol
Guo, Hongwei; Zhu, Mengyi; Yan, Bingji; Deng, Shichan; Li, Xinyu; Liu, Feng
2016-11-01
Viscosity is considered to be a significant indicator of the metallurgical property of blast furnace (BF) slag. A model for viscosity prediction based on the partial least-squares regression of varietal quantity reference points is presented in this article. The present model proposes a dynamic regional algorithm for reference point selection. The study applied the partial least-squares regression to establish the dynamic regional viscosity prediction model on the basis of limited discrete points data. Then an actual prediction was carried out with a large amount of viscosity data of real and synthesized BF slags that was obtained from a certain steel plant in China. The results show that this advanced method turns out to be satisfactory in the viscosity prediction of BF slags with a low averaging error and mean value deviation.
Guo, Hongwei; Zhu, Mengyi; Yan, Bingji; Deng, Shichan; Li, Xinyu; Liu, Feng
2017-02-01
Viscosity is considered to be a significant indicator of the metallurgical property of blast furnace (BF) slag. A model for viscosity prediction based on the partial least-squares regression of varietal quantity reference points is presented in this article. The present model proposes a dynamic regional algorithm for reference point selection. The study applied the partial least-squares regression to establish the dynamic regional viscosity prediction model on the basis of limited discrete points data. Then an actual prediction was carried out with a large amount of viscosity data of real and synthesized BF slags that was obtained from a certain steel plant in China. The results show that this advanced method turns out to be satisfactory in the viscosity prediction of BF slags with a low averaging error and mean value deviation.
Effect of viscosity on photodegradation rates in complex secondary organic aerosol materials
Hinks, Mallory L.; Brady, Monica V.; Lignell, Hanna; Song, Mijung; Grayson, James W.; Bertram, Allan K.; Lin, Peng; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.
2016-01-01
This work explores the effect of environmental conditions on the photodegradation rates of atmospherically relevant, photolabilie, organic molecules embedded in a film of secondary organic material (SOM). Three types of SOM were studied: a-pinene/O3 SOM (PSOM), limonene/O3 SOM (LSOM), and aged limonene/O3 obtained by exposure of LSOM to ammonia (brown LSOM). PSOM and LSOM were impregnated with 2,4-dinitrophenol (2,4-DNP), an atmospherically relevant molecule that photodegrades faster than either PSOM or LSOM alone, to serve as a probe of SOM matrix effects on photochemistry. Brown LSOM contains an unidentified chromophore that absorbs strongly at 510 nm and photobleaches upon irradiation. This chromophore served as a probe molecule for the brown LSOM experiments. In all experiments, the temperature and relative humidity (RH) surrounding the SOM films were varied. The extent of photochemical reaction in the samples was monitored using UV-Vis absorption spectroscopy. For all three model systems examined, the observed photodegradation rates were slower at lower temperatures and lower RH, under conditions that make SOM more viscous. Additionally, the activation energies for photodegradation of each system were positively correlated with the viscosity of the SOM matrix as measured in poke-flow experiments. These activation energies were calculated to be 50, 24, and 17 kJ/mol for 2,4-DNP in PSOM, 2,4-DNP in LSOM, and brown LSOM, respectively and PSOM was found to be the most viscous of the three. These results suggest that the increased viscosity is hindering the motion of the molecules in SOM and is slowing down photochemical reactions in which they participate.
Jana, Amit Kumar; Roy, Partha; Nath, Deb Narayan
2014-02-01
Effect of viscosity variation on the magnetic field effect in pyrene-N,N-dimethylaniline exciplex luminescence has been studied at different permittivity values. The data is compatible to the model of Krissinel et al. (1999) [10] reported earlier to explain the effect probing the escape yield of radical pairs. It is shown that the data can also be explained on the basis of a simple model. It is interesting to note that the present letter also demonstrates the positive slope of MFE with diffusivity at extremely high viscous condition as predicted by Krissinel et al. (1999) [10] which has not been observed in earlier experiments.
Tripathi, Bhavya
2016-01-01
In this paper, effects of heat transfer on the blood flow through a stenosed, inclined non-tapered porous artery subject to the action of external magnetic field is investigated. Viscosity is assumed as variable viscosity with variable Hematocrit throughout the region of the artery. Governing equations have been modeled by taking blood as incompressible magnetohydrodynamic (MHD) Newtonian fluid. The energy equation is formulated by taking an extra factor of the heat source in its equation. The nonlinear momentum equations are simplified under the assumption of mild stenosis. Homotopy perturbation method (HPM) is used to solve nonlinear equations of velocity and temperature profiles. Effects of porosity parameter (Z), applied magnetic field parameter (M), variable hematocrit parameter(Hr), Brinkman number (Br), heat source parameter (Q) and the Grashof number (Gr) on velocity and temperature profiles are discussed graphically.
El-Amin, Mohamed
2013-01-01
In this paper, the effects of thermal dispersion and variable viscosity on the non-Darcy free, mixed, and forced convection heat transfer along a vertical flat plate embedded in a fluid-saturated porous medium are investigated. Forchheimer extension is employed in the flow equation to express the non-Darcy model. The fluid viscosity varies as an inverse linear function of temperature. The coefficient of thermal diffusivity has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. Similarity solutions of the governing equations, for an isothermally heated plate, are obtained. Effects of the physical parameters, which govern the problem, on the rate of heat transfer in terms of Nusselt number, the slip velocity, and the boundary layer thickness, for the two cases Darcy and non-Darcy, are shown on graphs or entered in tables. © 2013 by Begell House, Inc.
A new LES model derived from generalized Navier-Stokes equations with nonlinear viscosity
Rodríguez, José M
2015-01-01
Large Eddy Simulation (LES) is a very useful tool when simulating turbulent flows if we are only interested in its "larger" scales. One of the possible ways to derive the LES equations is to apply a filter operator to the Navier-Stokes equations, obtaining a new equation governing the behavior of the filtered velocity. This approach introduces in the equations the so called subgrid-scale tensor, that must be expressed in terms of the filtered velocity to close the problem. One of the most popular models is that proposed by Smagorinsky, where the subgrid-scale tensor is modeled by introducing an eddy viscosity. In this work, we shall propose a new approximation to this problem by applying the filter, not to the Navier-Stokes equations, but to a generalized version of them with nonlinear viscosity. That is, we shall introduce a nonlinear viscosity, not as a procedure to close the subgrid-scale tensor, but as part of the model itself (see below). Consequently, we shall need a different method to close the subgri...
NONE
1997-12-31
This workshop on turbulent viscosity models and on their experimental validation was organized by the `convection` section of the French society of thermal engineers. From the 9 papers presented during this workshop, 8 deal with the modeling of turbulent flows inside combustion chambers, turbo-machineries or in other energy-related applications, and have been selected for ETDE. (J.S.)
Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification
Dijke, van K.C.; Kobayashi, I.; Schroën, C.G.P.H.; Uemura, K.; Nakajima, M.; Boom, R.M.
2010-01-01
Although many aspects of microchannel emulsification have been covered in literature, one major uncharted area is the effect of viscosity of both phases on droplet size in the stable droplet generation regime. It is expected that for droplet formation to take place, the inflow of the continuous phas
Effect of n-tyrosol on blood viscosity and platelet aggregation.
Plotnikov, M B; Chernysheva, G A; Smol'yakova, V I; Maslov, M Yu; Cherkashina, I V; Krysin, A P; Sorokina, I V; Tolstikova, T G
2007-01-01
Experiments on rats showed that n-tyrosol limited the increase in blood viscosity during thermal exposure at a shear rate of 5-300 sec(-1) and inhibited ADP-induced platelet aggregation. The effects of n-tyrosol are comparable to that of pentoxyphylline.
Evaluation of the synergistic effects of milk proteins in a rapid viscosity analyzer.
Stephani, Rodrigo; Borges de Souza, Alisson; Leal de Oliveira, Marcone Augusto; Perrone, Ítalo Tuler; Fernandes de Carvalho, Antônio; Cappa de Oliveira, Luiz Fernando
2015-12-01
Protein systems (PS) are routinely used by companies from Brazil and around the globe to improve the texture, yield, and palatability of processed foods. Understanding the synergistic behavior among the different protein structures of these systems during thermal treatment under the influence of pH can help to better define optimum conditions for products and processes. The interpretation of the reactions and interactions that occur simultaneously among the protein constituents of these systems as dispersions during thermal processing is still a major challenge. Here, using a rapid viscosity analyzer, we observed the rheological changes in the startup viscosities of 5 PS obtained by combining varying proportions of milk protein concentrate and whey protein concentrate under different conditions of pH (5.0, 6.5, and 7.0) and heat processing (85°C/15min and 95°C/5min). The solutions were standardized to 25% of total solids and 17% of protein. Ten analytical parameters were used to characterize each of the startup-viscosity ramps for 35 experiments conducted in a 2×3 × 5 mixed planning matrix, using principal component analysis to interpret behavioral similarities. The study showed the clear influence of pH 5.5 in the elevation of the initial temperature of the PS startup viscosity by at least 5°C, as well as the effect of different milk protein concentrate:whey protein concentrate ratios above 15:85 at pH 7.0 on the viscographic profile curves. These results suggested that the primary agent driving the changes was the synergism among the reactions and interactions of casein with whey proteins during processing. This study reinforces the importance of the rapid viscosity analyzer as an analytical tool for the simulation of industrial processes involving PS, and the use of the startup viscosity ramp as a means of interpreting the interactions of system components with respect to changes related to the treatment temperature.
Araruna, F. D.; Braz e Silva, P.; Carvalho, R. R.; Rojas-Medar, M. A.
2015-06-01
We consider the motion of a viscous incompressible fluid consisting of two components with a diffusion effect obeying Fick's law in ℝ3. We prove that there exists a small time interval where the fluid variables converge uniformly as the viscosity and the diffusion coefficient tend to zero. In the limit, we find a non-homogeneous, non-viscous, incompressible fluid governed by an Euler-like system.
Surface Effect on Vibration of Y-SWCNTs Embedded on Pasternak Foundation Conveying Viscose Fluid
A. Ghorbanpour-Arani
2015-01-01
Full Text Available Surface and small scale effects on free transverse vibration of a single-walled carbon nanotube (SWCNT fitted with Y-junction at downstream end conveying viscose fluid is investigated in this article based on Euler-Bernoulli beam (EBB model. Nonlocal elasticity theory is employed to consider small scale effects due to its simplicity and efficiency. The energy method and Hamilton’s principle are used to establish the corresponding motion equation. To discretize and solve the governing equation of motion the Galerkin method is applied. Moreover, the small-size effect, angle of Y-junction, surface layer and Pasternak elastic foundation are studied in detail. Regarding fluid flow effects, it has been concluded that the fluid flow is an effective factor on increasing the instability of Y-SWCNT. Results show that increasing the angle of Y-junction enhances the flutter fluid velocity where the first and second modes are merged. This work could be used in medical application and design of nano-electromechanical devices such as measuring the density of blood flowing through such nanotubes.
Saikia, Bijaylakshmi; Ramachandran, Ashwin; Sinha, Krishnendu; Govindarajan, Rama
2017-02-01
Accurate prediction of laminar to turbulent transition in compressible flows is a challenging task, as it can be affected by a combination of factors. Compressibility causes large variations in thermodynamic as well as transport properties of a gas, which in turn are known to affect flow stability. We study the stratification of individual transport properties and their combined behavior. We also examine the effect of a change in the magnitude of viscosity and conductivity on flow stability. The Couette flow of a perfect gas is our model problem and both modal and non-modal analyses are carried out. We notice a large destabilizing role of the increase in the conductivity value and a dramatic stabilizing effect of mean viscosity stratification, over a range of free-stream Mach number, Reynolds number, Prandtl number, and disturbance wavenumber. In the combined case, viscosity stratification plays a dominant role. We find this to be the case for finite-time transient growth in the parameter regime below linear instability as well as asymptotically at large time. A budget of the transient growth energy amplification is also shown to identify the effects of transport properties on the constituents of perturbation energy. The extensive results presented in this paper, we believe should motivate those studying more realistic flows to examine how these contrasting effects of stratification come together.
Thanh, Mai Duc
We consider an elliptic-hyperbolic model of phase transitions and we show that any Lax shock can be approximated by a traveling wave with a suitable choice of viscosity and capillarity. By varying viscosity and capillarity coefficients, we can cover any Lax shock which either remains in the same phase, or admits a phase transition. The argument used in this paper extends the one in our earlier works. The method relies on LaSalle's invariance principle and on estimating attraction region of the asymptotically stable of the associated autonomous system of differential equations. We will show that the saddle point of this system of differential equations lies on the boundary of the attraction region and that there is a trajectory leaving the saddle point and entering the attraction region. This gives us a traveling wave connecting the two states of the Lax shock. We also present numerical illustrations of traveling waves.
Dynamic analysis of polymeric fluid in shear flow for dumbbell model with internal viscosity
杨晓东; R.V.N.MELNIK
2008-01-01
The dynamic analysis of semi-flexible polymers,such as DNA molecules,is an important multiscale problem with a wide range of applications in science and bioengineering.In this contribution,a dumbbell model with internal viscosity was studied in steady shear flows of polymeric fluid.The tensors with moments other than second moment were approximated in the terms of second moment tensor.Then,the nonlinear algebraic equation of the second moment conformation tensor was calculated in closed form.Finally,substituting the resulting conformation tensor into the Kramers equation of Hookean spring force,the constitutive equations were obtained.The shear material properties were discussed for different internal viscosities and compared with the results of Brownian dynamics simulation.
Viscosity of fused silica and thermal noise from the standard linear solid model
Kondratiev, N. M.; Gorodetsky, M. L.
2016-10-01
The fluctuation-dissipation theorem states that each source of dissipation yields corresponding fluctuations. The most obvious source of dissipation in liquids is viscosity—internal friction between layers of matter. However, this property also exists in solid materials in a glass state, i.e., an amorphous substance that cannot become a crystal due to high viscosity. Fused silica is a low-loss glass material used in many interferometric applications demanding high stability, such as Fabry-Perot etalons and gravitational-wave detector mirrors and suspensions. Very high viscosity (from 1 017 to 1 040 Pa s in the literature) can be the source of additional noise and can influence the performance of such devices. We show that fused silica may be described with the standard linear solid model of viscoelastisity and present a method to estimate this type of noise.
Radwan, Asma; Amidon, Gordon L; Langguth, Peter
2012-10-01
A negative food effect, i.e. a decrease in bioavailability upon the co-administration of compounds together with food, has been attributed particularly with high solubility/low permeability compounds (BCS class III). Different mechanisms have been proposed including intestinal dilution leading to a lower concentration gradient across the intestinal wall as well as binding of the active pharmaceutical ingredient to food components in the intestine and thereby decreasing the fraction of the dose available for absorption. These mechanisms refer primarily to the compound and not to the dosage form. An increase in viscosity of the dissolution fluid will in particular affect the absorption of BCS type III compounds with preferential absorption in the upper small intestine if the API release is delayed from the dosage form. The present study demonstrated that the increase in viscosity of the dissolution medium, following ingestion of a solid meal, may drastically reduce disintegration and dissolution. For that purpose the viscosity of the standard FDA meal was determined and simulated by solutions of HPMC in buffer. As model formulations, three commercially available tablets containing trospium chloride, a BCS class III m-cholinoreceptor antagonist was used. Trospium chloride drug products have been described to undergo a negative food effect of more than 80% following ingestion with food. The tablets showed prolonged disintegration times and reduced dissolution rates in viscous media, which could be attributed to changes in the liquid penetration rates. The effect was particularly significant for film-coated tablets relative to uncoated dosage forms. The results show the necessity of considering media viscosity when designing in vitro models of drug release for BCS type III drug formulations.
Viscosity of particle laden films
Timounay, Yousra; Rouyer, Florence
2017-06-01
We perform retraction experiments on soap films where large particles bridge the two interfaces. Local velocities are measured by PIV during the unstationnary regime. The velocity variation in time and space can be described by a continuous fluid model from which effective viscosity (shear and dilatational) of particulate films is measured. The 2D effective viscosity of particulate films η2D increases with particle surface fraction ϕ: at low ϕ, it tends to the interfacial dilatational viscosity of the liquid/air interfaces and it diverges at the critical particle surface fraction ϕc ≃ 0.84. Experimental data agree with classical viscosity laws of hard spheres suspensions adapted to the 2D geometry, assuming viscous dissipation resulting from the squeeze of the liquid/air interfaces between the particles. Finally, we show that the observed viscous dissipation in particulate films has to be considered to describe the edge velocity during a retraction experiment at large particle coverage.
Jacobitz, Frank; Porterfield, Colin; Engebrecht, Cheryn; Metzger, Ian
2007-11-01
A more comprehensive model for the apparent viscosity of blood is proposed and applied to simulations of the microcirculation in rat spinotrapezius muscle fascia. At the microcirculatory level, the apparent viscosity of blood depends on the local vessel diameter, hematocrit, and shear rate. Starting with the apparent viscosity model proposed by Pries, Secomb, Gaehtgens, and Gross (Circulation Research, 67, 826-834, 1990), describing the effect of vessel diameter and hematocrit on the apparent viscosity, and using experimental data presented by Lipowsky, Usami, and Chien (Microvascular Research, 19, 297-319, 1980), describing the shear rate dependence of apparent viscosity, a more comprehensive model is developed. This model is applied to simulations of the microcirculation in rat spinotrapezius muscle fascia. The simulations use realistic vessel topology for the microvasculature, reconstructed from microscope images of tissue samples, and consider passive and active vessel properties. The numerical method is based on a Hagen-Poiseuille balance in the microvessels and a sparse matrix solver is used to obtain the solution. It was found, for example, that the distribution of vessel length follows a log-normal law. The distribution of hematocrit, however, was found to be approximately normal.
Effect of viscosity on appetite and gastro-intestinal hormones
Zijlstra, Nicolien; Mars, Monica; de Wijk, René A
2009-01-01
/m(2)) participated in this cross-over study. Subjects received a fixed amount of a chocolate flavored milk-based liquid or semi-solid product similar in energy density and macronutrient composition. Before intake and 15, 30, 60 and 90 min thereafter, appetite was rated and blood was drawn to determine...... glucose, CCK-8, active ghrelin, desacyl ghrelin and GLP-1 concentrations. After the last blood withdrawal, subjects were offered a chocolate cake meal to consume ad libitum. In the appetite ratings we observed a small effect showing that the semi-solid product is apparently considered as more satisfying...... product effect (p 0.004). Concentrations were consistently higher after intake of the semi-solid product. Ad libitum intake of the chocolate cake was 102+/-55 g after the liquid and 96+/-46 g after the semi-solid product (ns). The results of our study show a similar response of the gastro...
Near-surface viscosity effects on capillary rise of water in nanotubes
Vo, Truong Quoc; Barisik, Murat; Kim, BoHung
2015-11-01
In this paper, we present an approach for predicting nanoscale capillary imbibitions using the Lucas-Washburn (LW) theory. Molecular dynamics (MD) simulations were employed to investigate the effects of surface forces on the viscosity of liquid water. This provides an update to the modified LW equation that considered only a nanoscale slip length. An initial water nanodroplet study was performed to properly elucidate the wetting behavior of copper and gold surfaces. Intermolecular interaction strengths between water and corresponding solid surfaces were determined by matching the contact angle values obtained by experimental measurements. The migration of liquid water into copper and gold capillaries was measured by MD simulations and was found to differ from the modified LW equation. We found that the liquid layering in the vicinity of the solid surface induces a higher density and viscosity, leading to a slower MD uptake of fluid into the capillaries than was theoretically predicted. The near-surface viscosity for the nanoscale-confined water was defined and calculated for the thin film of water that was sheared between the two solid surfaces, as the ratio of water shear stress to the applied shear rate. Considering the effects of both the interface viscosity and slip length of the fluid, we successfully predicted the MD-measured fluid rise in the nanotubes.
Effect of pre-heating on the viscosity and microhardness of a resin composite.
Lucey, S
2010-04-01
The effect of pre-heating resin composite on pre-cured viscosity and post-cured surface hardness was evaluated. Groups of uncured specimens were heated to 60 degrees C and compared with control groups (24 degrees C) with respect to viscosity and surface hardness. Mean (SD) viscosities of the pre-heated specimens (n = 15) were in the range of 285 (13)-377 (11) (Pa) compared with 642 (35)-800 (23) (Pa) at ambient temperature. There was a statistically significant difference between the two groups (P < 0.001). Mean (SD) Vickers microhardness (VHN) of the pre-heated group (n = 15) was 68.6 (2.3) for the top surface and 68.7 (1.8) for the bottom surface measured at 24 h post curing (specimen thickness = 1.5 mm). The corresponding values for the room temperature group were 60.6 (1.4) and 59.0 (3.5). There was a statistically significant difference between corresponding measurements taken at the top and bottom for the pre-heated and room temperature groups (P < 0.001). There was no significant difference between top and bottom measurements within each group. Pre-heating resin composite reduces its pre-cured viscosity and enhances its subsequent surface hardness. These effects may translate as easier placement together with an increased degree of polymerization and depth-of-cure.
Coalescence-induced jumping of droplet: Inertia and viscosity effects
Farokhirad, Samaneh; Morris, Jeffrey F.; Lee, Taehun
2015-10-01
The problem of coalescence-induced self-propelled jumping of droplet is studied using three-dimensional numerical simulation. The focus is on the effect of inertia and in particular the effect of air density on the behavior of the merged droplet during jumping. A lattice Boltzmann method is used for two identical, static micro-droplets coalescing on a homogeneous substrate with contact angle ranging from 0∘ to 180∘. The results reveal that the effect of air density is significant on detachment of the merged droplet from the substrate at the later stage of the jumping process; the larger the air density, the larger the jumping height of the droplet. Analysis of streamlines and vorticity contours is performed for density ratios ranging from 60 to 800. These show a generation of vortical structures inside and around the droplet. The intensity of these structures gets weaker after droplet departure as the air inertia is decreased. The results are also presented in terms of phase diagrams of the merged droplet jumping for different Ohnesorge numbers (Oh) and surface wettabilities for both small and large density ratios. The critical value of contact angle where the merged droplet jumps away from the substrate is independent of density ratio and has a value around 150∘. However, the critical value of Oh depends on both density ratio and wettability of the surface for contact angles greater than 150∘. In this range of contact angle, the diagrams show two distinct dynamical regimes for different density ratios, namely, inertial and viscous regimes.
S. Elipot
2009-02-01
Full Text Available Spectral characteristics of the oceanic boundary-layer response to wind stress forcing are assessed by comparing surface drifter observations from the Southern Ocean to a suite of idealized models that parameterize the vertical flux of horizontal momentum using a first-order turbulence closure scheme. The models vary in their representation of vertical viscosity and boundary conditions. Each is used to derive a theoretical transfer function for the spectral linear response of the ocean to wind stress.
The transfer functions are evaluated using observational data. The ageostrophic component of near-surface velocity is computed by subtracting altimeter-derived geostrophic velocities from observed drifter velocities (nominally drogued to represent motions at 15-m depth. Then the transfer function is computed to link these ageostrophic velocities to observed wind stresses. The traditional Ekman model, with infinite depth and constant vertical viscosity is among the worst of the models considered in this study. The model that most successfully describes the variability in the drifter data has a shallow layer of depth O(30–50 m, in which the viscosity is constant and O(100–1000 m^{2} s^{−1}, with a no-slip bottom boundary condition. The second best model has a vertical viscosity with a surface value O(200 m^{2} s^{−1}, which increases linearly with depth at a rate O(0.1–1 cm s^{−1} and a no-slip boundary condition at the base of the boundary layer of depth O(10^{3}m. The best model shows little latitudinal or seasonal variability, and there is no obvious link to wind stress or climatological mixed-layer depth. In contrast, in the second best model, the linear coefficient and the boundary layer depth seem to covary with wind stress. The depth of the boundary layer for this model is found to be unphysically large at some latitudes and seasons, possibly a consequence of the inability of
Measurements and modelling of phase behaviour and viscosity of a heavy oil-butane system
Yazdani, A.; Maini, B.B. [Calgary Univ., AB (Canada)
2007-07-01
Solvent based recovery processes are environmentally friendly alternatives for thermal techniques. Information on the phase behavior of the heavy oil/solvent system is needed for numerical simulation and feasibility studies of these processes. However, the lack of experimental data for such systems in the literature has been problematic. Solvent/oil mixtures that are evaluated within the context of the vapour extraction (VAPEX) process, require accurate description of the system's pressure, volume, and temperature (PVT) properties. This paper presented the results of a study that designed an experimental set-up and conducted several experiments in order to obtain the required PVT information. The paper presented the results of the PVT experiments conducted with the Frog-Lake heavy oil/butane system that was used in VAPEX experiments reported previously by the authors. The experimental measurements included the solvent fractions in the oil, mixture density and mixture viscosity at different saturation pressures. Using the phase behavior package WINPROP, the PVT results were modeled and an equation of state (EOS) was tuned for simulating the experimental behavior of the system. The viscosity measurements were compared with the predictions of several available correlations. It was concluded that the predicted values of EOS for density and saturation pressure were in agreement with the obtained experimental data and that a mixing type relationship was found to be adequate for describing the viscosity of heavy oil - solvent mixtures. 12 refs., 4 tabs., 10 figs.
Space-geodetic Constraints on GIA Models with 3D Viscosity
Van Der Wal, W.; Xu, Z.
2012-12-01
Models for Glacial Isostatic Adjustment (GIA) are an important correction to observations of mass change in the polar regions. Inputs for GIA models include past ice thickness and deformation parameters of the Earth's mantle, both of which are imperfectly known. Here we focus on the latter by investigating GIA models with 3D viscosity and composite (linear and non-linear) flow laws. It was found recently that GIA models with a composite flow law result in a better fit to historic sea level data, but they predict too low present-day uplift rates and gravity rates. Here GIA models are fit to space-geodetic constraints in Fennoscandia and North America. The preferred models are used to calculate the magnitude of the GIA correction on mass change estimates in Greenland and Antarctica. The observations used are GRACE Release 4 solutions from CSR and GFZ and published GPS solutions for North America and Fennoscandia, as well as historic sea level data. The GIA simulations are performed with a finite element model of a spherical, self-gravitating, incompressible Earth with 2x2 degree elements. Parameters in the flow laws are taken from seismology, heatflow measurements and experimental constraints and the ice loading history is prescribed by ICE-5G. It was found that GRACE and GPS derived uplift rates agree at the level of 1 mm/year in North America and at a level of 0.5 mm/year in Fennoscandia, the difference between the two regions being due to larger GPS errors and under sampling in North America. It can be concluded that both GPS and GRACE see the same process and the effects of filtering, noise and non-GIA processes such as land hydrology are likely to be small. Two GIA models are found that bring present-day uplift rate close to observed values in North America and Fennoscandia. These models result in a GIA correction of -17 Gt/year and -26 Gt/year on Greenland mass balance estimates from GRACE.
Bianchi type-VIh string cloud cosmological models with bulk viscosity
Tripathy, Sunil K.; Behera, Dipanjali
2010-11-01
String cloud cosmological models are studied using spatially homogeneous and anisotropic Bianchi type VIh metric in the frame work of general relativity. The field equations are solved for massive string cloud in presence of bulk viscosity. A general linear equation of state of the cosmic string tension density with the proper energy density of the universe is considered. The physical and kinematical properties of the models have been discussed in detail and the limits of the anisotropic parameter responsible for different phases of the universe are explored.
[Effect of surface modified nano-diamond on viscosity of dental adhesives].
Luo, Juan; Liang, Jie; Hu, Ai-yun; Liu, Xue-heng
2012-06-01
Different surface modified ultrafine-diamond (UFD) was added into dental adhesives as filler ,then the influence of dental adhesive properties was observed. The main matrix of dental adhesive was high polymer resin. Different content of non-modified UFD(n-UFD) or modified UFD(m-UFD) were added into dental adhesives, then the viscosity of materials were measured. The data was processed with SPSS17.0 software package. The viscosity of dental adhesives was decreased when the proportion of UFD was less than 0.1wt%, especially when it was 0.1wt%; but was significantly improved when the proportion was more than 0.1wt%. The effect of UFD and surface-modified UFD on the viscosity was significantly different. The results show that silane coupling was chemically-grafted on the surface of UFD, the dispersion and stability of UFD in ethanol was improved; And a quantity of UFD with special content could reduce the viscosity of dental adhesives and improve the flowability obviously. The m-UFD was superior to n-UFD.
A Brief Review of Viscosity Models for Slag in Coal Gasification
Massoudi, Mehrdad; Wang, Ping
2011-11-01
Many researchers have defined the phenomenon of 'slagging' as the deposition of ash in the radiative section of a boiler, while 'fouling' refers to the deposition of ash in the convective-pass region. Among the important parameters affecting ash deposition that need to be studied are ash chemistry, its transport, deposit growth, and strength development; removability of the ash deposit; heat transfer mechanisms; and the mode of operation for boilers. The heat transfer at the walls of a combustor depends on many parameters including ash deposition. This depends on the processes or parameters controlling the impact efficiency and the sticking efficiency. For a slagging combustor or furnace, however, the temperatures are so high that much of the coal particles are melted and the molten layer, in turn, captures more particles as it flows. The main problems with ash deposition are reduced heat transfer in the boiler and corrosion of the tubes. Common ways of dealing with these issues are soot blowing and wall blowing on a routine basis; however, unexpected or uncontrolled depositions can also complicate the situation, and there are always locations inaccessible to the use of such techniques. Studies have indicated that slag viscosity must be within a certain range of temperatures for tapping and the membrane wall to be accessible, for example, between 1300 C and 1500 C, the viscosity is approximately 25 Pa {center_dot} s. As the operating temperature decreases, the slag cools and solid crystals begin to form. In such cases the slag should be regarded as a non-Newtonian suspension, consisting of liquid silicate and crystals. A better understanding of the rheological properties of the slag, such as yield stress and shear-thinning, are critical in determining the optimum operating conditions. To develop an accurate heat transfer model in any type of coal combustion or gasification process, the heat transfer and to some extent the rheological properties
Gupta, S.A.; Cochran, H.D.; Cummings, P.T. [Department of Chemical Engineering, University of Tennessee, Knoxville, Tennessee 37996-2200 (United States)]|[Chemical Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6268 (United States)
1997-12-01
This study uses nonequilibrium molecular dynamics simulation to explore the rheology of confined liquid alkanes. Two alkanes that differ in molecular structural complexity are examined: tetracosane (C{sub 24}H{sub 50}), which is a linear alkane, and squalane (C{sub 30}H{sub 62}), which has six symmetrically placed methyl branches along a 24 carbon backbone. These model lubricants are confined between model walls that have short chains tethered to them, thus screening the wall details. This paper, the third of a three part series, compares the viscosities of the confined fluids to those of the bulk fluids. The alkanes are described by a well-documented potential model that has been shown to reproduce bulk experimental viscosity and phase equilibria measurements. Details of the simulation method, and structural information can be found in the preceding two papers of this series. The measured strain rates in these simulations range between 10{sup 8} and 10{sup 11} s{sup {minus}1}, which is typical of a number of practical applications. The confined fluids undergo extensive shear thinning, showing a power-law behavior. Comparison of results for the confined fluid to those for the bulk fluid reveal that, for the conditions examined, there is no difference between the bulk and confined viscosities for these alkanes. This observation is in contrast to experimental results at much lower strain rates (10{endash}10{sup 5} s{sup {minus}1}), which indicate the viscosities of the confined fluid to be much larger than the bulk viscosities. In making the comparison, we have carefully accounted for slip at the wall and have performed simulations of the bulk fluid at the same conditions of strain rate, temperature, and pressure as for the corresponding confined fluid. The viscosity is found to be independent of the wall spacing. The calculated power-law exponents are similar to experimentally observed values. We also note that the exponent increases with increasing density of the
Boufadel, Michel C.; Suidan, Makram T.; Venosa, Albert D.
1999-04-01
We present a formulation for water flow and solute transport in two-dimensional variably saturated media that accounts for the effects of the solute on water density and viscosity. The governing equations are cast in a dimensionless form that depends on six dimensionless groups of parameters. These equations are discretized in space using the Galerkin finite element formulation and integrated in time using the backward Euler scheme with mass lumping. The modified Picard method is used to linearize the water flow equation. The resulting numerical model, the MARUN model, is verified by comparison to published numerical results. It is then used to investigate beach hydraulics at seawater concentration (about 30 g l -1) in the context of nutrients delivery for bioremediation of oil spills on beaches. Numerical simulations that we conducted in a rectangular section of a hypothetical beach revealed that buoyancy in the unsaturated zone is significant in soils that are fine textured, with low anisotropy ratio, and/or exhibiting low physical dispersion. In such situations, application of dissolved nutrients to a contaminated beach in a freshwater solution is superior to their application in a seawater solution. Concentration-engendered viscosity effects were negligible with respect to concentration-engendered density effects for the cases that we considered.
Accretion disk dynamics. α-viscosity in self-similar self-gravitating models
Kubsch, Marcus; Illenseer, Tobias F.; Duschl, Wolfgang J.
2016-04-01
Aims: We investigate the suitability of α-viscosity in self-similar models for self-gravitating disks with a focus on active galactic nuclei (AGN) disks. Methods: We use a self-similar approach to simplify the partial differential equations arising from the evolution equation, which are then solved using numerical standard procedures. Results: We find a self-similar solution for the dynamical evolution of self-gravitating α-disks and derive the significant quantities. In the Keplerian part of the disk our model is consistent with standard stationary α-disk theory, and self-consistent throughout the self-gravitating regime. Positive accretion rates throughout the disk demand a high degree of self-gravitation. Combined with the temporal decline of the accretion rate and its low amount, the model prohibits the growth of large central masses. Conclusions: α-viscosity cannot account for the evolution of the whole mass spectrum of super-massive black holes (SMBH) in AGN. However, considering the involved scales it seems suitable for modelling protoplanetary disks.
Plasma Viscosity with Mass Transport in Spherical ICF Implosion Simulations
Vold, Erik L; Ortega, Mario I; Moll, Ryan; Fenn, Daniel; Molvig, Kim
2015-01-01
The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion (ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. We have implemented a Lagrange hydrodynamic code in one-dimensional spherical geometry with plasma viscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasma viscosity and to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasma viscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Plasma viscosity reduc...
The effect of viscosity on the contraction of the stalk of Vorticella Convallaria
Kantha, Deependra; van Winkle, David
2006-03-01
The contraction of the stalk of Vorticella Convallaria behaves as one of the most powerful single cell biological engines.Contractions in three different viscous mediums were recorded by a PhantomV5 camera (Vision Research) on a bright field microscope with 20X objective. The contractions were recorded as cines (image sequences) with the image resolution of 256 pixels X 128 pixels at 7000 pictures per second. The maximum variation in maximum velocity of one organism was 5.2 cm/s and the minimum variation for a different organism was 0.4 cm/s for the same viscous medium. It occurred at 2-3ms after the start of contraction. The force of contraction and the force constant were calculated as a function of the time to see the effect of viscosity on the contraction of the stalk. This experiment needs further investigation to see the net effect of viscosity on the contraction of the stalk.
The effect of viscosity on steady transonic flow with a nodal solution topology
Owocki, Stanley P.; Zank, Gary P.
1991-01-01
The effect of viscosity on a steady, transonic flow for which the inviscid limit has a nodal solution topology near the critical point is investigated. For the accelerating case, viscous solutions tend to repel each other, so that a very delicate choice of initial conditions is required to prevent them from diverging. Only the two critical solutions extend to arbitrarily large distances into both the subsonic and supersonic flows. For the decelerating case, the solutions tend to attract, and so an entire two-parameter family of solutions now extends over large distances. The general effect of viscosity on the solution degeneracy of a nodal topology is thus to reduce or limit it for the accelerating case and to enhance it for the decelerating case. The astrophysical implications of these findings are addressed.
Effect of fluid viscosity on wave propagation in a cylindrical bore in micropolar elastic medium
Sunita Deswal; Sushil K Tomar; Rajneesh Kumar
2000-10-01
Wave propagation in a cylindrical bore filled with viscous liquid and situated in a micropolar elastic medium of infinite extent is studied. Frequency equation for surface wave propagation near the surface of the cylindrical bore is obtained and the effect of viscosity and micropolarity on dispersion curves is observed. The earlier problems of Biot and of Banerji and Sengupta have been reduced as a special case of our problem.
Zeberg-Mikkelsen, Claus Kjær; Watson, G.; Baylaucq, A.;
2006-01-01
viscosity models with a physical and theoretical background. The evaluated models are based on the hard-sphere scheme, the concepts of the free-volume and the friction theory, and a model derived from molecular dynamics. In addition to these models, the simple compositional models by Grunberg...
Cantu, David C.; Malhotra, Deepika; Koech, Phillip K.; Heldebrant, David J.; Zheng, Feng (Richard); Freeman, Charles J.; Rousseau, Roger; Glezakou, Vassiliki-Alexandra
2016-01-01
CO2 capture from power generation with aqueous solvents remains energy intensive due to the high water content of the current technology, or the high viscosity of non-aqueous alternatives. Quantitative reduced models, connecting molecular structure to bulk properties, are key for developing structure-property relationships that enable molecular design. In this work, we describe such a model that quantitatively predicts viscosities of CO2 binding organic liquids (CO2BOLs) based solely on molecular structure and the amount of bound CO2. The functional form of the model correlates the viscosity with the CO2 loading and an electrostatic term describing the charge distribution between the CO2-bearing functional group and the proton-receiving amine. Molecular simulations identify the proton shuttle between these groups within the same molecule to be the critical indicator of low viscosity. The model, developed to allow for quick screening of solvent libraries, paves the way towards the rational design of low viscosity non-aqueous solvent systems for post-combustion CO2 capture. Following these theoretical recommendations, synthetic efforts of promising candidates and viscosity measurement provide experimental validation and verification.
Ivković-Jensen, M M; Kostić, N M
1997-07-01
This is a study of the effects of viscosity (in the range of 0.8-790 cP), of temperature (in the range of 260.7-307.7 K), and of ionic strength (in the range of 2.5-20.0 mM) on the kinetics of photoinduced electron-transfer reaction 3Zncyt/pc(II) --> Zncyt+/pc(I) within the electrostatic complex of zinc cytochrome c and cupriplastocyanin at pH 7.0. The unimolecular rate constant is kF. The apparent activation parameters DeltaH*, DeltaS*, and DeltaG* for this reaction were obtained in experiments with aqueous glycerol solutions having a constant composition. The interpolation of kF values obtained at the constant composition into the dependence of kF on temperature at constant viscosity gave the proper activation parameters, which agree with those obtained in experiments with solutions having a constant viscosity. This agreement validates the latter method, which is more efficient than the former, for determining activation parameters of processes that are modulated by viscosity. The smooth change in kF is governed by the change in viscosity, not in other properties of the solvent, and it does not depend on the choice of the viscosigen. Donor/acceptor electronic coupling (HAB) and reorganizational energy (lambda), obtained by fitting of the temperature dependence of kF to the Marcus equation, are consistent with true electron transfer and with electron transfer that is coupled to, or gated by, a preceding structural rearrangement of the diprotein complex 3Zncyt/pc(II). The fact that at very high viscosity kF approaches zero shows that the reaction is probably gated throughout the investigated range of viscosity. Kinetic effects and noneffects of ionic strength, viscosity, and thermodynamic driving force indicate, but do not prove, that the reaction under consideration is gated. The kinetic effect of viscosity is analyzed in terms of two models. Because ln kF is a nonlinear function of ln eta, protein friction has to be considered in the analysis of viscosity effects
Viscosity, relaxation time, and dynamics within a model asphalt of larger molecules
Li, Derek D.; Greenfield, Michael L.
2014-01-01
The dynamics properties of a new "next generation" model asphalt system that represents SHRP AAA-1 asphalt using larger molecules than past models is studied using molecular simulation. The system contains 72 molecules distributed over 12 molecule types that range from nonpolar branched alkanes to polar resins and asphaltenes. Molecular weights range from 290 to 890 g/mol. All-atom molecular dynamics simulations conducted at six temperatures from 298.15 to 533.15 K provide a wealth of correlation data. The modified Kohlrausch-Williams-Watts equation was regressed to reorientation time correlation functions and extrapolated to calculate average rotational relaxation times for individual molecules. The rotational relaxation rate of molecules decreased significantly with increasing size and decreasing temperature. Translational self-diffusion coefficients followed an Arrhenius dependence. Similar activation energies of ˜42 kJ/mol were found for all 12 molecules in the model system, while diffusion prefactors spanned an order of magnitude. Viscosities calculated directly at 533.15 K and estimated at lower temperatures using the Debye-Stokes-Einstein relationship were consistent with experimental data for asphalts. The product of diffusion coefficient and rotational relaxation time showed only small changes with temperature above 358.15 K, indicating rotation and translation that couple self-consistently with viscosity. At lower temperatures, rotation slowed more than diffusion.
Viscosity, relaxation time, and dynamics within a model asphalt of larger molecules
Li, Derek D.; Greenfield, Michael L., E-mail: greenfield@egr.uri.edu [Department of Chemical Engineering, University of Rhode Island, Kingston, Rhode Island 02881 (United States)
2014-01-21
The dynamics properties of a new “next generation” model asphalt system that represents SHRP AAA-1 asphalt using larger molecules than past models is studied using molecular simulation. The system contains 72 molecules distributed over 12 molecule types that range from nonpolar branched alkanes to polar resins and asphaltenes. Molecular weights range from 290 to 890 g/mol. All-atom molecular dynamics simulations conducted at six temperatures from 298.15 to 533.15 K provide a wealth of correlation data. The modified Kohlrausch-Williams-Watts equation was regressed to reorientation time correlation functions and extrapolated to calculate average rotational relaxation times for individual molecules. The rotational relaxation rate of molecules decreased significantly with increasing size and decreasing temperature. Translational self-diffusion coefficients followed an Arrhenius dependence. Similar activation energies of ∼42 kJ/mol were found for all 12 molecules in the model system, while diffusion prefactors spanned an order of magnitude. Viscosities calculated directly at 533.15 K and estimated at lower temperatures using the Debye-Stokes-Einstein relationship were consistent with experimental data for asphalts. The product of diffusion coefficient and rotational relaxation time showed only small changes with temperature above 358.15 K, indicating rotation and translation that couple self-consistently with viscosity. At lower temperatures, rotation slowed more than diffusion.
Accretion disk dynamics: {\\alpha}-viscosity in self-similar self-gravitating models
Kubsch, Marcus; Duschl, W J
2016-01-01
Aims: We investigate the suitability of {\\alpha}-viscosity in self-similar models for self-gravitating disks with a focus on active galactic nuclei (AGN) disks. Methods: We use a self-similar approach to simplify the partial differential equations arising from the evolution equation, which are then solved using numerical standard procedures. Results: We find a self-similar solution for the dynamical evolution of self-gravitating {\\alpha}-disks and derive the significant quantities. In the Keplerian part of the disk our model is consistent with standard stationary {\\alpha}-disk theory, and self-consistent throughout the self-gravitating regime. Positive accretion rates throughout the disk demand a high degree of self-gravitation. Combined with the temporal decline of the accretion rate and its low amount, the model prohibits the growth of large central masses. Conclusions: {\\alpha}-viscosity cannot account for the evolution of the whole mass spectrum of super-massive black holes (SMBH) in AGN. However, conside...
Gao, J.; Guo, W.; Vinen, W. F.
2016-09-01
The energy dissipation of quasiclassical homogeneous turbulence in superfluid 4He (He II) is controlled by an effective kinematic viscosity ν', which relates the energy decay rate d E /d t to the density of quantized vortex lines L as d E /d t =-ν'(κL ) 2 . The precise value of ν' is of fundamental importance in developing our understanding of the dissipation mechanism in He II, and it is also needed in many high-Reynolds-number turbulence experiments and model testing that use He II as the working fluid. However, a reliable determination of ν' requires the measurements of both E (t ) and L (t ) , which was never achieved. Here we discuss our study of the quasiclassical turbulence that emerges in the decay of thermal counterflow in He II above 1 K. We were able to measure E (t ) by using a recently developed flow-visualization technique and L (t ) via second-sound attenuation. We report the ν' values in a wide temperature range determined from a comparison of the time evolution of E (t ) and L (t ) .
The effect of non-Newtonian viscosity on the stability of the Blasius boundary layer
Griffiths, P. T.; Gallagher, M. T.; Stephen, S. O.
2016-07-01
We consider, for the first time, the stability of the non-Newtonian boundary layer flow over a flat plate. Shear-thinning and shear-thickening flows are modelled using a Carreau constitutive viscosity relationship. The boundary layer equations are solved in a self-similar fashion. A linear asymptotic stability analysis, that concerns the lower-branch structure of the neutral curve, is presented in the limit of large Reynolds number. It is shown that the lower-branch mode is destabilised and stabilised for shear-thinning and shear-thickening fluids, respectively. Favourable agreement is obtained between these asymptotic predictions and numerical results obtained from an equivalent Orr-Sommerfeld type analysis. Our results indicate that an increase in shear-thinning has the effect of significantly reducing the value of the critical Reynolds number, this suggests that the onset of instability will be significantly advanced in this case. This postulation, that shear-thinning destabilises the boundary layer flow, is further supported by our calculations regarding the development of the streamwise eigenfunctions and the relative magnitude of the temporal growth rates.
The effects of non-Newtonian viscosity on the deformation of red blood cells in a shear flow
Sesay, Juldeh
2005-11-01
The analyses of the effects of non-Newtonian viscosity on the membrane of red blood cells (RBCs) suspended in a shear flow are presented. The specific objective is to investigate the mechanical deformation on the surfaces of an ellipsoidal particle model. The hydrodynamic stresses and other forces on the surface of the particle are used to determine the cell deformation. We extended previous works, which were based on the Newtonian fluid models, to the non-Newtonian case, and focus on imposed shear rate values between 1 and 100 per second. Two viscosity models are investigated, which respectively correspond to a normal person and a patient with cerebrovascular accident (CVA). The results are compared with those obtained assuming a Newtonian model. We observed that the orientation of the cell influences the deformation and the imposed shear rate drives the local shear rate distribution along the particle surface. The integral particle deformation for the non-Newtonian models in the given shear rate regime is higher than that for the Newtonian reference model. Finally, the deformation of the cell surface decreases as the dissipation ratio increases.
Convection Heat Transfer Modeling of Ag Nanofluid Using Different Viscosity Theories
Ali Bakhsh Kasaeian
2012-04-01
Full Text Available ABSTRACT: In this paper, the effects of adding nanoparticles (including Ag to a fluid media for improving free convection heat transfer were analysed. The free convective heat transfer was assumed to be in laminar flow regime, and the corresponding calculations and solutions were all done by the integral method. Water, as a Newtonian fluid, was considered as the base and all relevant thermo physical properties of the nanofluids were considered to be unvarying. The calculations performed and the graphs generated showed that, in general, the addition of nanoparticles to the fluid media resulted in an increment or improvement of its heat transfer coefficient. With increase in the concentration of the nanoparticles, the heat transfer rate of the fluid also increased. The increment in heat transfer is also dependent on the nanoparticles’ thermal conductivity and the viscosity theory which was utilized in the calculations. In this study, four different theories were used to calculate the viscosities of the nanofluids. The effects of viscosity on the nanofluids’ thermal conductivity were apparent from the calculations which were performed for nanoparticle concentrations of 4% or less. ABSTRAK: Kajian ini menganalisis kesan penambahan nanopartikel Ag ke dalam media bendalir bagi tujuan pembaikkan pemindahan haba perolakan bebas. Perolakan bebas diandaikan berada di zon aliran laminar, di mana penyelesaian dan pengiraan telah dilakukan mengunakan kaedah kamilan. Air yang merupakan cecair Newtonian, dianggap sebagai asas dan sifat terma fizikal nanocecair dianggapkan tidak berubah. Mengikut pengiraan yang dilakukan dan graf yang diplotkan, umumnya penambahan nanopartikel kepada media bendalir menyebabkan peningkatan dan pengembangan pekali pemindahan haba. Kadar pemindahan haba meningkat dengan nanopartikel. Peningkatan pemindahan haba juga bergantung kepada pengalir haba nanopartikel dan teori kelikatan yang digunakan. Di dalam kajian ini, empat
Chan Yau Kei
2011-05-01
Full Text Available Silicone oil tamponade is used as vitreous substitute to treat complicated retinal diseases. It provides support to the retina and acts against contraction of the retina and as such plays a vital role in preventing eyes from certain blindness. Silicone oil however has a tendency to emulsify and is accountable to inflammation and glaucoma. In in-vitro study, it was found that using silicone-oil with higher viscosity reduce the occurrences of emulsifications. In this study, an eye model chamber was used to capture the movement of silicone oil bubbles inside the model eye chamber by rapid serial photography. A few tamponades derived from the same material but with different shear viscosities were used. Our objective of this experiment is to investigate the effect of viscosity of tamponade to the movement of tamponade relative to retinal phase in model eye chambers mimicking saccadic eye movements. Our experiment confirms that shear viscosity determines the relative movement between the silicone bubble and the chamber wall. The higher the viscosity, the smaller the movement of tamponade relative to the chamber wall. We suggested that using much viscous tamponade may reduce the onset of emulsification due to the reduction of relative movement.
Nagatani, Takashi; Stanley, H. Eugene
1990-03-01
A combined effect of sticking probability and finite viscosity ratio is studied on the pattern formation in Laplacian growth. A renormalization-group theory is developed to study the crossover phenomena between the diffusion-limited aggregation (DLA) and nonfractal structure. A two-stage crossover phenomenon is analyzed by using a three-parameter position-space renormalization-group method. A global flow diagram in three-parameter space is obtained. It is found that there are three nontrivial fixed points, the first Eden point, the DLA point and the second Eden point. The second Eden point corresponding to the dense structure is stable in all directions, while the first Eden point and the DLA point are saddle points. When the sticking probability P is small and the viscosity ratio is finite, the aggregate must cross over from the dense structure, through the DLA fractal, finally to the dense aggregate.
Effect of gamma irradiation on viscosity reduction of cereal porridges for improving energy density
Lee, Ju-Woon; Kim, Jae-Hun; Oh, Sang-Hee; Byun, Eui-Hong; Yook, Hong-Sun; Kim, Mee-Ree; Kim, Kwan-Soo; Byun, Myung-Woo
2008-03-01
Cereal porridges have low energy and nutrient density because of its viscosity. The objective of the present study was to evaluate the effect of irradiation on the reduction of viscosity and on the increasing solid content of cereal porridge. Four cereals, wheat, rice, maize (the normal starchy type) and waxy rice, were used in this study. The porridge with 3000 cP was individually prepared from cereal flour, gamma-irradiated at 20 kGy and tested. Gamma irradiation of 20 kGy was allowed that the high viscous and rigid cereal porridges turned into semi-liquid consistencies. The solid contents of all porridges could increase by irradiation, compared with non-irradiated ones. No significant differences of starch digestibility were observed in all cereal porridge samples. The results indicated that gamma irradiation might be helpful for improving energy density of cereal porridge with acceptable consistency.
Effect of gamma irradiation on viscosity reduction of cereal porridges for improving energy density
Lee, Ju-Woon [Radiation Application Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of)], E-mail: sjwlee@kaeri.re.kr; Kim, Jae-Hun; Oh, Sang-Hee; Byun, Eui-Hong [Radiation Application Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of); Yook, Hong-Sun; Kim, Mee-Ree [Department of Food and Nutrition, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Kim, Kwan-Soo [Research and Development Department, Greenpia Technology, Yeoju 469-811 (Korea, Republic of); Byun, Myung-Woo [Radiation Application Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185 (Korea, Republic of)], E-mail: mwbyun@kaeri.re.kr
2008-03-15
Cereal porridges have low energy and nutrient density because of its viscosity. The objective of the present study was to evaluate the effect of irradiation on the reduction of viscosity and on the increasing solid content of cereal porridge. Four cereals, wheat, rice, maize (the normal starchy type) and waxy rice, were used in this study. The porridge with 3000 cP was individually prepared from cereal flour, gamma-irradiated at 20 kGy and tested. Gamma irradiation of 20 kGy was allowed that the high viscous and rigid cereal porridges turned into semi-liquid consistencies. The solid contents of all porridges could increase by irradiation, compared with non-irradiated ones. No significant differences of starch digestibility were observed in all cereal porridge samples. The results indicated that gamma irradiation might be helpful for improving energy density of cereal porridge with acceptable consistency.
Kotsilkova R.
2014-06-01
Full Text Available Nanocomposites of multiwalled carbon nanotubes (MWCNTs in epoxy resin and polypropylene (PP are studied. The effect of matrix viscosity on the degree of dispersion of nanotubes is determined by rheological methods. Rheology and microwave properties are correlated to estimate the optimal limits of nanofiller content required for improving the performance of nanocomposites. Rheological percolation threshold is determined for both types nanocomposites, ϕp=0.27% for the epoxy/MWCNT and; ϕp=1.5% for the PP/MWCNT, as found critical for achieving a network structure of interacting nanotubes in the matrix polymer. Good electromagnetic shielding efficiency was obtained for nanocomposites at nanotube contents above the rheological percolation. Low viscosity matrix facilitates contacts between MWCNTs, resulting in appearance of electromagnetic shielding at very low percolation threshold.
Breyfogle, M.; Marine, T.; Ware, A. S.; Spong, D. A.
2008-11-01
The impact of magnetic geometry on neoclassical flows and viscosities for the Helically Symmetric Experiment (HSX) is investigated using the PENTA code [1,2]. Specifically, two topics are investigated: (1) finite-beta effects and (2) configurational variations. The PENTA code is used to calculate flows in HSX with the vacuum magnetic geometry and with finite-beta magnetic surfaces from the VMEC equilibrium code. This is done for the standard quasi-helically symmetric configuration of HSX, a symmetry-breaking mirror configuration and a hill configuration. The impact of these changes in the magnetic geometry on neoclassical viscosities and flows in HSX will be discussed.[0pt] [1] D. A. Spong, Phys. Plasmas 12, 056114 (2005). [0pt] [2] D. A. Spong, Fusion Sci. Technology 50, 343 (2006).
Giffin, Guinevere A.; Moretti, Arianna; Jeong, Sangsik; Passerini, Stefano
2017-02-01
Ionic liquids are attractive materials for alternative electrolytes to combat the safety issues associated with conventional organic carbonate-based electrolytes. However, the performance of ionic liquid-based cells is generally not competitive as the high viscosity and low conductivity limits the rate performance. The work presented here demonstrates that the drawbacks in terms of rate capability can be overcome through the use of the high lithium concentration Pyr12O1FTFSI0.6LiFTFSI0.4 electrolyte. Despite an order of magnitude difference in the conductivity and viscosity, this high concentration electrolyte outperforms the lithium-dilute electrolyte with the same components in terms of rate capability in Li metal/LFP cells and LTO/LFP cells. The results suggest that the effective Li ion transport in the concentrated electrolyte is higher than in the dilute solution.
Effect of pH on the viscosity of grewia mucilage
Ikoni Ogaji
2012-01-01
Full Text Available Background: The stability and efficacy of liquid pharmaceutical preparations depend on the pH of the medium. Such liquid preparations may contain varied additives performing different functions. One of the qualities of oral liquid pharmaceutical preparations is appropriate viscosity for pumping and transfer during manufacture and dispensing to patients. Gums find use in such liquid preparations as thickening or suspending agents together with different additives that may influence the pH of the environment and hence the stability and quality of the preparation. Aim of the study: The purpose of this study was to determine the effect of pH on the viscosity of grewia gum obtained from Grewia mollis that is potential pharmaceutical excipient. Setting and Design: The study was based on experiments carried out in the laboratory setting and the conclusions were based on the observations made. Materials and Methods: Aqueous mucilage of grewia (2% w/v was prepared and the pH was determined at different shear rates on Brookfield cone and plate rheometer at 25°C. Adjustment of pH was facilitated by the addition of 0.25 N solution of either hydrochloric acid or sodium hydroxide before the readings were taken. Results: The viscosity of the mucilage was characteristically pseudoplastic and it depended on pH of the medium and storage time. The viscosity ratio generally decreased from 2.046 to 1.470 as the pH of the medium increased from acidic to basic (2.18 to 13.10. The dynamic yield value of the dispersion at pH 2.55 and 5.08 were, respectively, 10.5 and 45. The viscosity of grewia gum dispersion changed with change in pH of the medium anomalously. Conclusion: Changes in the viscosity of grewia gum dispersion were observed with change in the pH in an unrelated fashion. This suggests that the use of grewia gum together with other additives in oral liquid preparations should be done with discretion.
Effects of water transportation on subduction dynamics: Roles of viscosity and density reduction
Nakao, Atsushi; Iwamori, Hikaru; Nakakuki, Tomoeki
2016-11-01
The effects of water on subduction dynamics, e.g., plate migration rate, slab geometry, stress field, and back-arc spreading, are investigated by using a 2-D self-consistent model for lithosphere subduction and whole mantle convection. We solve water transportation coupled with hydrous mineral phase changes. Mantle flows and water transportation are interactive through constitutive and state equations for hydrous rocks. Our model has successfully reproduced the water distribution in a mantle wedge and along the slab with sufficient resolution comparable to that of previous models that focus on the mantle wedge structure. As a result, low density owing to hydration reduces subduction rates, back-arc spreading, and slab stagnation on the phase boundary at 660-km depth, whereas low viscosity owing to hydration enhances rapid subduction, trench migration, and slab stagnation. We attribute these results to mechanisms that cause the hydrous buoyancy of subducting plates to reduce the slab pull force and the accompanying tensile stress on overlying lithosphere. In addition, hydrous weakening diminishes the mechanical coupling of the subducted slab with the wedge mantle and overriding lithosphere. Thus, water is capable of generating two opposite situations in the stress field of the overlying lithosphere and the subduction rate. Water is therefore expected to be an important mechanism for generating broad styles of the subduction structure and kinematics, as observed in actual subduction zones such as Tonga and Mariana. Such observed variation in the subduction mode can be caused by variation in buoyancy corresponding to the water content from relatively dry to several thousands of parts per million for the wedge mantle and slab surface, whereas the extremely buoyant case does not appear to occur in nature. Water in the mantle is thus key to better understand the whole-mantle-scale slab dynamics as well as island arc volcanic processes.
Kretz, V.; Berest, P.; Hulin, J. P.; Salin, D.
2003-02-01
We study the vertical miscible displacements of two fluids of different densities and/or viscosities in two model porous media, constructed using different arrangements of blocks of packed glass beads with different sizes. The two configurations have the same permeability distributions but different spatial arrangements and structural features. Time variations of the mean fluid concentration in different sections along the samples are monitored by an acoustic technique. For stable viscosity or density contrasts, the spreading of the displacement front is predominantly macrodispersive. For fluids of the same viscosity but different densities, the macrodispersivities approach at large velocities, where the displacement is stable, the passive tracer limit, ld∞, which is controlled only by the heterogeneity of the medium. This is true, regardless of the density contrast. At lower velocities, where gravity instabilities can exist, the normalized dispersivities ld/ld∞ vary exponentially with the normalized flow rate, with opposite exponents in the stable and unstable configurations. These results are compared to existing theoretical works based on stochastic approaches and linear stability analyses.
Zeberg-Mikkelsen, Claus Kjær; Watson, G.; Baylaucq, A.
2006-01-01
measured with a classical capillary viscometer (Ubbelohde) with an uncertainty of +/- 1%. A total of 208 experimental datapoints are reported. The viscosity behavior of this binary system is interpreted as the results of changes in the free volume, and the breaking or weakening of hydrogen bonds...... viscosity models with a physical and theoretical background. The evaluated models are based on the hard-sphere scheme, the concepts of the free-volume and the friction theory, and a model derived from molecular dynamics. In addition to these models, the simple compositional models by Grunberg......-Nissan and Katti-Chaudhri have also been applied. Overall a satisfactory representation of the viscosity of these two binary ethanol + C-7 hydrocarbon systems is found for the different models within the considered T, P range taking into account their simplicity....
The Effect of Viscosity on Performance of a Low Specific Speed Centrifugal Pump
Rouhollah Torabi
2016-01-01
Full Text Available Centrifugal pump delivery head and flow rate drop effectively during the pumping of viscous fluids. Several methods and correlations have been developed to predict reduction rate in centrifugal pump performance when handling viscous fluids, but their results are not in very good agreement with each other. In this study, a common industrial low specific speed pump, which is extensively used in different applications, is studied. The entire pump, including impeller, volute, pipes, front and rear sidewall gaps, and balance holes, is simulated in Computational Fluid Dynamics and 3D full Navier Stokes equations are solved. CFD results are compared with experimental data such as pump performance curves, static pressure in casing, and disk friction loss. Dimensionless angular velocity and leakage rate are investigated in sidewall gap and efficiency variation due to viscosity is studied. The results demonstrate that the behavior of the fluid in sidewall gap is strictly sensitive to viscosity. Increasing viscosity improves the volumetric efficiency by reducing internal leakage through wear rings and balance holes, causing, however, a significant fall in the disk and overall efficiency. Results lead to some recommendations for designing centrifugal pumps which may be used in transferring viscous fluids.
A. Abedini
2014-04-01
Full Text Available In this paper, the effect of compressive viscosity on the slow mode oscillation of solar corona loops is studied. The coronal loops medium are considered in low beta condition, uniform magnetic field in the presence of gravitational stratification and temperature gradient. Two-dimensional Magneto-Hydro-Dynamics (MHD equations are perturbed about the equilibrium and thenthese equations are linearized and ultimately a second order differential equation is obtained for velocity perturbation by stretching method. In considering the appropriate boundary conditions for the differential equationis solved analytically and numerically. Oscillation Modes obtained from numerical solutions with real data from satellites such as SOHO, TRACE and SDO are compared. Results show that the gravitational layering, fluctuations in the corona loop for frequency values greater than the cutoff frequency occurs. In small longitudes, viscosity damping is strong . Since the observations confirms strong damping of oscillations corona, can be said viscosity alone can justify the oscillation damping in elongated loops, the oscillation period is between 2 and 48 min, corresponds to the actual data.
Effect of viscosity on dust–ion acoustic shock wave in dusty plasma with negative ions
Adhikary, Nirab C., E-mail: nirab_iasst@yahoo.co.in [Physical Sciences Division, Institute of Advanced Study in Science and Technology, Vigyan Path, Paschim Boragaon, Garchuk, Guwahati 781035, Assam (India)
2012-03-26
The properties of dust–ion acoustic (DIA) shock wave in a dusty plasma containing positive and negative ions is investigated. The reductive perturbation method has been used to derive the Korteweg–de Vries–Burgers equation for dust acoustic shock waves in a homogeneous, unmagnetized and collisionless plasma whose constituents are Boltzmann distributed electrons, singly charged positive ions, singly charged negative ions and cold static dust particles. The KdV–Burgers equation is derived and its stationary analytical solution is numerically analyzed where the effect of viscosity on the DIA shock wave propagation is taken into account. It is found that the viscosity in the dusty plasma plays as a key role in dissipation for the propagation of DIA shock. -- Highlights: ► Dust–ion acoustic shock wave propagation is studied in multi-component dusty plasma. ► KdV–Burgers equation is derived and its stationary solution is numerically analyzed. ► Viscosity in dusty plasma plays as a key role in dissipation of DIA shock wave.
Azzopardi Barry John
2012-04-01
Full Text Available The effect of liquid viscosity on slug flow in a 50 mm diameter bubble column was investigated experimentally using air-silicone oil as operating fluid with silicone oil of viscosities 5, 100, 1000 and 5000 mPa.s. Data was collected using Electrical Capacitance Tomography (ECT, a non-intrusive advanced instrumentation measuring technique and the high Speed Video Camera, through which the slug parameters such as length of Taylor bubbles and liquid slug, void fraction in Taylor bubbles and liquid slug, slug frequency, film thickness and pressure gradient in the slug, were measured and analyzed. The analysis was done using the void fraction time series, probability density function and power spectral density plots. Superficial gas velocities of 0.02≤Ugs≤0.361 m/s were used in the experiment. It was also observed that as viscosity increases, slug frequency, structure velocity, length of liquid slug, void fraction in liquid slug and void fraction in Taylor bubbles decreases; while the length of Taylor bubble, film thickness and pressure gradient in the slug increases.
A Preliminary Study Of The Effect Of Some Pressurising Gasses On The Viscosity Of Dimethyl Ether
Sivebæk, Ion Marius
2006-01-01
Dimethyl Ether (DME) has been recognised as a clean substitute for diesel oil as it does not form soot during combustion. DME has a vapour pressure of 6 bar at 25 C so pressurisation is necessary to keep DME liquid at ambient temperature. Inert gases are good candidates as pressurising media...... for DME but their effect on DME viscosity is unknown. Argon (Ar), nitrogen (N2), carbon dioxide (CO2), hydrogen (H2) and Propane (C3H8) have been investigated at pressure levels of 12 – 15 bars. A Cannon-Manning semi-micro capillary glass viscometer, size 25, enclosed in a cylindrical pressure container......-micro glass viscometers, size 25, submerged completely in a constant temperature bath. A kinematic viscosity of 0,188 cSt 0,001 cSt @ 25 C, was found, consistent with the previous and initial result 0,186 cSt 0,002 cSt. Key words: Dimethyl Ether (DME), a clean substitute for diesel oil. DME viscosity...
The role of viscosity contrast on plume structure in laboratory modeling of mantle convection
Prakash, Vivek N; Arakeri, Jaywant H
2016-01-01
We have conducted laboratory experiments to model important aspects of plumes in mantle convection. We focus on the role of the viscosity ratio U (between the ambient fluid and the plume fluid) in determining the plume structure and dynamics. In our experiments, we are able to capture geophysical convection regimes relevant to mantle convection both for hot spots (when U > 1) and plate-subduction (when U < 1) regimes. The planar laser induced fluorescence (PLIF) technique is used for flow visualization and characterizing the plume structures. The convection is driven by compositional buoyancy generated by the perfusion of lighter fluid across a permeable mesh and the viscosity ratio U is systematically varied over a range from 1/300 to 2500. The planform, near the bottom boundary for U=1, exhibits a well-known dendritic line plume structure. As the value of U is increased, a progressive morphological transition is observed from the dendritic-plume structure to discrete spherical plumes, accompanied with th...
Chang, Cheng-Ling; Peyroux, Juliette; Perez, Alex; Tsui, Chi-Leung; Wang, Wei-Chih
2009-03-01
Viscosity measurement by bend loss of fiber is presented. The sensing principle makes use of the damping characteristic of a vibrating optical fiber probe with fix-free end configuration. By measuring the displacement of the fiber probe, the viscosity can be determined by matching the probe's displacement with the displacement built in the database obtained by either experimental method or Finite element calculation. Experimental results are presented by measuring the sucrose and glycerol solutions of different concentrations with a viscosity varying from 1 to 15 cP. Stokes' flow assumption is utilized to attenuate the mass density effect and simplify the viscosity measurement.
Goumiri, I. R. [Princeton Univ., NJ (United States). Mechanical and Aerospace Dept.; Rowley, C. W. [Princeton Univ., NJ (United States). Mechanical and Aerospace Dept.; Sabbagh, S. A. [Columbia Univ., New York, NY (United States). Dept. of Applied Physics and Applied Mathematics; Gates, D. A. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Gerhardt, S. P. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Boyer, M. D. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Andre, R. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Kolemen, E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Taira, K. [Florida State Univ, Dept Mech Engn, Tallahassee, FL USA.
2016-02-19
A model-based feedback system is presented to control plasma rotation in a magnetically confined toroidal fusion device, to maintain plasma stability for long-pulse operation. This research uses experimental measurements from the National Spherical Torus Experiment (NSTX) and is aimed at controlling plasma rotation using two different types of actuation: momentum from injected neutral beams and neoclassical toroidal viscosity generated by three-dimensional applied magnetic fields. Based on the data-driven model obtained, a feedback controller is designed, and predictive simulations using the TRANSP plasma transport code show that the controller is able to attain desired plasma rotation profiles given practical constraints on the actuators and the available measurements of rotation.
Measuring and overcoming limits of the Saffman-Delbrück model for soap film viscosities.
Vivek, Skanda; Weeks, Eric R
2015-01-01
We observe tracer particles diffusing in soap films to measure the two-dimensional (2D) viscous properties of the films. Saffman-Delbrück type models relate the single-particle diffusivity to parameters of the film (such as thickness h) for thin films, but the relation breaks down for thicker films. Notably, the diffusivity is faster than expected for thicker films, with the crossover at h/d = 5.2 ± 0.9 using the tracer particle diameter d. This indicates a crossover from purely 2D diffusion to diffusion that is more three-dimensional. We demonstrate that measuring the correlations of particle pairs as a function of their separation overcomes the limitations of the Saffman-Delbrück model and allows one to measure the viscosity of a soap film for any thickness.
Zhu, Peicheng
2009-01-01
In the present article, we are interested in an initial boundary value problem for a coupled system of partial differential equations arising in martensitic phase transition theory of elastically deformable solid materials, e.g., steel. This model was proposed and investigated in previous work by Alber and Zhu in which the weak solutions are defined in a standard way, however the key technique is not applicable to multi-dimensional problem. Intending to solve this multi-dimensional problem and to investigate the sharp interface limits of our models, we thus define weak solutions in a different way by using the notion of viscosity solution, then prove the existence of weak solutions to this problem in one space dimension, yet the multi-dimensional problem is still open.
Abbass Ghanbari–Niaki
2015-07-01
Full Text Available A limited number of studies has been carried out concerning the combined effects of resistance training and saffron supplementation on cardiovascular risk factors. The aim of this study was to assess the effects of circuit resistance training with Crocus sativus (saffron supplementation on plasma viscosity and fibrinogen. For this purpose, 44 healthy male subjects, based on individual characteristics and after homogenization, were divided into four groups, including water-training (WT n=11, petal sweat–training (PST n=10, bottom part of flower-training (BFT n=11, and upper part of flower-training (UFT n=12. Resistance training consisted of 12 stations (each station for 30 seconds with 40% of one repetition maximum for 2 weeks (5 sessions per week. Saffron in the amount of 500 mg was used twice daily, i.e. in the morning and immediately after exercise. Blood samples were taken before and 48 hours after the last exercise session and were analyzed for fibrinogen and plasma viscosity. Significant differences were observed between groups in plasma levels of fibrinogen (P=0.01. The post hoc test showed significant differences between the UFT and PST groups and the UFT and BFT groups (respectively, P=0.04 and P=0.014. In the post-test, plasma fibrinogen had significantly decreased in the WT (P=0.005, PWT (P=0.003, and UFT (P=0.001 groups compared with pre-test data (within group difference. Moreover, plasma viscosity was significantly changed among groups (F3, 37=3.52, P=0.024. The post hoc test showed significant differences between the UFT and WT groups (P=0.037. In post-test data, plasma viscosity had significantly decreased in the WT (P=0.015 and UFT (P<0.001 groups compared with pre-test data. The present results show that circuit resistance training with saffron supplements can reduce cardiovascular risk factors (fibrinogen and plasma viscosity.
Ghosh, Uday Narayan, E-mail: unghosh1@rediffmail.com; Chatterjee, Prasanta; Roychoudhury, Rajkumar [Department of Mathematics, Siksha Bhavana, Visva Bharati, Santiniketan 731235 (India)
2015-07-15
Recently Gun Li et al. discussed “Effects of damping solitary wave in a viscosity bounded plasma” [Phys. Plasmas 21, 022118 (2014)]. The paper contains some serious errors which have been pointed out in this Comment.
Sunil; Pavan Kumar Bharti; Divya Sharma; R. C. Sharma
2004-01-01
The effect of the magnetic field dependent (MFD) viscosity on the thermal convection in a ferromagnetic fluid in the presence of a uniform vertical magnetic field is considered for a fluid layer in a porous medium, heated from below...
Neitzel, Anne-Christin; Stamer, Eckhard; Junge, Wolfgang; Thaller, Georg
2015-05-01
Laboratory somatic cell count (LSCC) records are usually recorded monthly and provide an important information source for breeding and herd management. Daily milk viscosity detection in composite milking (expressed as drain time) with an automated on-line California Mastitis Test (CMT) could serve immediately as an early predictor of udder diseases and might be used as a selection criterion to improve udder health. The aim of the present study was to clarify the relationship between the well-established LSCS and the new trait,'drain time', and to estimate their correlations to important production traits. Data were recorded on the dairy research farm Karkendamm in Germany. Viscosity sensors were installed on every fourth milking stall in the rotary parlour to measure daily drain time records. Weekly LSCC and milk composition data were available. Two data sets were created containing records of 187,692 milkings from 320 cows (D1) and 25,887 drain time records from 311 cows (D2). Different fixed effect models, describing the log-transformed drain time (logDT), were fitted to achieve applicable models for further analysis. Lactation curves were modelled with standard parametric functions (Ali and Schaeffer, Legendre polynomials of second and third degree) of days in milk (DIM). Random regression models were further applied to estimate the correlations between cow effects between logDT and LSCS with further important production traits. LogDT and LSCS were strongest correlated in mid-lactation (r = 0.78). Correlations between logDT and production traits were low to medium. Highest correlations were reached in late lactation between logDT and milk yield (r = -0.31), between logDT and protein content (r = 0.30) and in early as well as in late lactation between logDT and lactose content (r = -0.28). The results of the present study show that the drain time could be used as a new trait for daily mastitis control.
Whittington, A. G.; Romine, W. L.
2014-12-01
Understanding the dynamics of rhyolitic conduits and lava flows, requires precise knowledge of how viscosity (η) varies with temperature (T), pressure (P) and volatile content (X). In order to address the paucity of viscosity data for high-silica rhyolite at low water contents, which represent water saturation at near-surface conditions, we made 245 viscosity measurements on Mono Craters (California) rhyolites containing between 0.01 and 1.1 wt.% H2O, at temperatures between 796 and 1774 K using parallel plate and concentric cylinder methods at atmospheric pressure. We then developed and calibrated a new empirical model for the log of the viscosity of rhyolitic melts, where non-linear variations due to temperature and water content are nested within a linear dependence of log η on P. The model was fitted to a total of 563 data points: our 245 new data, 255 published data from rhyolites across a wide P-T-X space, and 63 data on haplogranitic and granitic melts under high P-T conditions. Statistically insignificant parameters were eliminated from the model in an effort to increase parsimony and the final model is simple enough for use in numerical models of conduit or lava flow dynamics: log η = -5.142+(13080-2982log(w+0.229))/(T-(98.9-175.9 log(w+0.229)))- P(0.0007-0.76/T ) where η is in Pa s, w is water content in wt.%, P is in MPa and T is in K. The root mean square deviation (rmsd) between the model predictions and the 563 data points used in calibration is 0.39 log units. Experimental constraints have led previously to spurious correlations between P, T, X and η in viscosity data sets, so that predictive models may struggle to correctly resolve the individual effects of P, T and X, and especially their cross-correlations. The increasing water solubility with depth inside a simple isothermal sheet of obsidian suggests that viscosity should decrease by ~1 order of magnitude at ~20m depth and by ~2 orders of magnitude at ~100m depth. If equilibrium water
A Binder Viscosity Effect on the Wet-Wounded Composite Porosity in the Impregnating Bath
M. A. Komkov
2014-01-01
Full Text Available The aim of this work is to define experimentally an impregnation rate of VM-1 glass fibers and CBM aramid bundles with the epoxy binder EDB-10 using wet method of winding. During the impregnation process of the fibrous fillers by the liquid binder, air is displaced from the interfiber space of fiber and bundle. With the composite product winding a fiber impregnation process is short. That is why gas inclusions or pores are formed in the polymer-fiber compositeThe impregnation rate or porosity of wound material will depend directly on the binder viscosity. To reduce an epoxy binder viscosity temporarily is possible by two ways. The first is to heat a liquid epoxy composition EDB-10 to the maximum possible temperature during the winding process of the product. The second method is to dilute the binder by a solvent, such as acetone or alcohol. However, the solvent reduces its strength.The paper presents experimental data to show the volumetric content of pores in the wound composite affected only by the viscosity of the epoxy binder. Heating a binder allowed us to regulate a changing conditional viscosity of the binder in the impregnating bath for the normal conditions of impregnation. Other impacts on the impregnation and filament-winding processes, such as filler kinks, squeeze, vacuuming binder, highly tensioned winding, and others were not used.Experimentally obtained dependences of the porosity value of wound composite on the conditional viscosity of binder are nonlinear and can be used to design heaters for impregnating devices of winders. The research technique and results can be used in development of technological processes to manufacture composite structures by winding from the other reinforcing fibrous fillers and thermo-active binders.The results show that the volumetric content of pores can significantly vary within 8 - 14 % of material volume. Therefore, to reduce the number of pores in the wound composite to 1-2 %, auxiliary
McCubbin, A. J.; Smith, S. P.; Ferraro, N. M.; Callen, J. D.; Meneghini, O.
2012-10-01
Understanding the torque applied by resonant and non-resonant magnetic perturbations and its effect on rotation is essential to predict confinement and stability in burning plasmas. Non-axisymmetric 3D fields produced in the DIII-D tokamak apply a torque to the plasma, which can be evaluated through its effect on the plasma rotation. One explanation for this torque is Neoclassical Toroidal Viscosity (NTV) acting through non-resonant field components [1]. We have developed a software framework in which magnetic perturbations calculated by the state of the art two fluid MHD code M3D-C1 can be used in NTV calculations. For discharges with applied external magnetic fields in DIII-D, the experimentally determined torques will be analyzed and compared with NTV models.[4pt] [1] J.D. Callen, Nucl. Fusion 51, 094026 (2011).
Müller, Christian; Hansen, K.; Szabo, Peter
2003-01-01
broth was significantly affected by the biomass concentration, the morphology, and also by pH. The chsB disruption strain had lower consistency index K values for all biomass concentrations investigated, which is a desirable trait for industrial Aspergillus fermentations. (C) 2003 Wiley Periodicals, Inc........4-22.5 g kg(-1) biomass) and the power-law model adequately described the rheological properties. In the cultivations there were pellets, clumps, and freely dispersed hyphal elements. The different morphological fractions were quantified using image analysis. The apparent viscosity of the fermentation...
The Role of Viscosity in TATB Hot Spot Ignition
Fried, L E; Zepeda-Ruis, L; Howard, W M; Najjar, F; Reaugh, J E
2011-08-02
The role of dissipative effects, such as viscosity, in the ignition of high explosive pores is investigated using a coupled chemical, thermal, and hydrodynamic model. Chemical reactions are tracked with the Cheetah thermochemical code coupled to the ALE3D hydrodynamic code. We perform molecular dynamics simulations to determine the viscosity of liquid TATB. We also analyze shock wave experiments to obtain an estimate for the shock viscosity of TATB. Using the lower bound liquid-like viscosities, we find that the pore collapse is hydrodynamic in nature. Using the upper bound viscosity from shock wave experiments, we find that the pore collapse is closest to the viscous limit.
Dominguez, J.C.; Oliet, M.; Alonso, María Virginia
2016-01-01
of modeling the evolution of the complex viscosity using a widely used chemorheological model such as the Arrhenius model for each tested temperature, the change of the complex viscosity as a function of the degree-of-cure was predicted using a new exponential type model. In this model, the logarithm...
Contribution to modeling the viscosity Arrhenius-type equation for saturated pure fluids
Tian, Jianxiang; Zhang, Laibin
2016-09-01
Recently, Haj-Kacem et al. proposed an equation modeling the relationship between the two parameters of viscosity Arrhenius-type equations [Fluid Phase Equilibria 383, 11 (2014)]. The authors found that the two parameters are dependent upon each other in an exponential function form. In this paper, we reconsidered their ideas and calculated the two parameter values for 49 saturated pure fluids by using the experimental data in the NIST WebBook. Our conclusion is different with the ones of Haj-Kacem et al. We found that (the linearity shown by) the Arrhenius equation stands strongly only in low temperature range and that the two parameters of the Arrhenius equation are independent upon each other in the whole temperature range from the triple point to the critical point.
Accretion discs models with the "beta"-viscosity prescription derived from laboratory experiments
Huré, J M; Zahn, J P; Hur\\'e, Jean-Marc; Richard, Denis; Zahn, Jean-Paul
2001-01-01
We examine under which conditions one may apply, to steady state keplerian accretion discs, the "beta"-viscosity prescription which has been derived from rotating shear flow experiments (Richard & Zahn 1999). Using a vertically averaged model, we show that this law may be suitable for all three families of known systems: in young stellar objects, evolved binary stars and Active Galactic Nuclei discs (except in their outer gas pressure dominated regions where turbulence becomes hypersonic). According to the standard criterion for viscous stability, "beta"-discs are always stable throughout. Using realistic opacities and equation of state, we demonstrate that these discs are thermally unstable in the temperature domain where hydrogen recombines, when they are optically thick, and this could lead to limit cycle behavior. Radiation pressure dominated regions are thermally stable, in contrast with "alpha"-discs. This results in a fully stable solution for the innermost parts of AGN discs.
La Spina, Giuseppe; Burton, Mike; de'Michieli Vitturi, Mattia; Landi, Patrizia; Polacci, Margherita
2016-04-01
Magma permeability is the most important factor controlling the transition between effusive and explosive activity of a basaltic eruption. Indeed, when low viscosity magmas are not permeable enough, volatiles stay trapped into the melt, expanding and pushing up more and more magma as the pressure decreases. As soon as the volume fraction of the gas, or the overpressure of the bubbles, or the strain rate of the melt becomes too large, magma fragments, generating an explosive eruption. On the contrary, if magma is sufficiently permeable, gas is able to decouple from the melt and fragmentation does not occur, causing, thus, an effusive eruption. A correct modelisation of gas/magma decoupling is, therefore, fundamental to properly understand the ascent dynamics occurring during an eruption. Here we study several permeability models for a low viscosity magma using a 1D steady-state model for magma ascent dynamics, focussing, in particular, on the 2007 effusive eruption at Stromboli volcano, Italy. We compare the numerical solutions computed using respectively Darcy's and Forchheimer's law. We also take into account the different expressions for Darcian permeability introduced by Bai et al. (2010, 2011) for Stromboli volcano, comparing them against a new expression for permeability derived from the data collected by Polacci et al. (2009) on Stromboli scoria. The numerical results show that using the permeability expressions of Bai et al. (2010, 2011) with Darcy's law, magma fragments into an explosive eruption. Using the new permeability model, instead, the decoupling between gas and magma is sufficient to generate an effusive eruption. However, when Forchheimer's law is adopted, fragmentation is always achieved, even with our new permeability. For a broader investigation on permeability, we also adopt the permeability relation introduced by Degruyter et al. (2012) as a function of three parameters: bubble number density, throat-bubble size ratio, and tortuosity factor
Effects of Velocity-Slip and Viscosity Variation in Squeeze Film Lubrication of Two Circular Plates
R.R. Rao
2013-03-01
Full Text Available A generalized form of Reynolds equation for two symmetrical surfaces is taken by considering velocity-slip at the bearing surfaces. This equation is applied to study the effects of velocity-slip and viscosity variation for the lubrication of squeeze films between two circular plates. Expressions for the load capacity and squeezing time obtained are also studied theoretically for various parameters. The load capacity and squeezing time decreases due to slip. They increase due to the presence of high viscous layer near the surface and decrease due to low viscous layer.
Effect of Viscosity on Free-Surface Waves in Oseen Flows
卢东强
2004-01-01
Based on the complex dispersion relation for the two-dimensional free-surface waves generated by a moving body in the steady Oseen flows, the effect of viscosity on wavelength and wave amplitude was investigated by means of an asymptotic method and a numerical analysis. A comparison between the asymptotic and numerical analysis for the viscous decay factor demonstrates the validity of the perturbation expansions for the wave profile. The numerical result shows that the wavelength of viscous wave is slightly elongated in comparison with that of inviscid wave.
Measurement on Effective Shear Viscosity Coefficient of Iron under Shock Compression at 100 GPa
LI Yi-Lei; LIU Fu-Sheng; ZHANG Ming-Jian; MA Xiao-Juan; LI Ying-Lei; ZHANG Ji-Chun
2009-01-01
The oscillatory damping curve of a shock front propagating in iron shocked to 103 GPa is measured by use of two-stage light-gas gun and electric pin techniques. The corresponding effective shear viscosity coefficient is deduced to be about 2000 Pa.s from Miller and Ahrens' formula.The result is consistent with that of Mineev's data at 31GPa,while it is higher by five orders than the predictions based on the static measurements at about 5 GPa and 2000K and molecular dynamic simulation up to 135-375 GPa and 4300-6000 K,and the discussions are presented.
Shit, G C; Sinha, A
2012-01-01
This paper presents a theoretical study of blood flow through a tapered and overlapping stenosed artery under the action of an externally applied magnetic field. The fluid (blood) medium is assumed to be porous in nature. The variable viscosity of blood depending on hematocrit (percentage volume of erythrocytes) is taken into account in order to improve resemblance to the real situation. The governing equation for laminar, incompressible and Newtonian fluid subject to the boundary conditions is solved by using a well known Frobenius method. The analytical expressions for velocity component, volumetric flow rate, wall shear stress and pressure gradient are obtained. The numerical values are extracted from these analytical expressions and are presented graphically. It is observed that the influence of hematocrit, magnetic field and the shape of artery have important impact on the velocity profile, pressure gradient and wall shear stress. Moreover, the effect of primary stenosis on the secondary one has been sig...
G. C. Shit
2014-01-01
Full Text Available This paper presents a theoretical study of blood flow through a tapered and overlapping stenosed artery under the action of an externally applied magnetic field. The fluid (blood medium is assumed to be porous in nature. The variable viscosity of blood depending on hematocrit (percentage volume of erythrocytes is taken into account in order to improve resemblance to the real situation. The governing equation for laminar, incompressible and Newtonian fluid subject to the boundary conditions is solved by using a well known Frobenius method. The analytical expressions for velocity component, volumetric flow rate, wall shear stress and pressure gradient are obtained. The numerical values are extracted from these analytical expressions and are presented graphically. It is observed that the influence of hematocrit, magnetic field and the shape of artery have important impact on the velocity profile, pressure gradient and wall shear stress. Moreover, the effect of primary stenosis on the secondary one has been significantly observed.
Viscosity, thermal diffusivity and Prandtl number of nanoparticle suspensions
WANG Buxuan; ZHOU Leping; PENG Xiaofeng
2004-01-01
Using our reported experimental data of effective thermal conductivity, specific heat capacity and viscosity for CuO nanoparticle suspensions, the corresponding thermal diffusivity and Prandtl number are calculated. With the hard sphere model and considering effects of particle clustering and surface adsorption, the increase of viscosity for nanoparticle suspension observed is explained. It is shown that the effective thermal conductivity will be strongly affected by the formation and correlated spatial distribution of nanoparticle clusters when compared to viscosity in hosting liquid.
Prediction of viscosities and surface tensions of fuels using a new corresponding states model
Queimada, A.J.; Rolo, L.I.; Caco, A.I.
2006-01-01
While some properties of diesels are cheap, easy and fast to measure, such as densities, others such as surface tensions and viscosities are expensive and time consuming. A new approach that uses some basic information such as densities to predict viscosities and surface tensions is here proposed...
Modeling and prediction of non-Newtonian viscosity of crude oils
Ramirez-Gonzalez, P.V. [Univ. Nacional Autonoma de Mexico (Mexico). Dept. de Ingenieria Quimica; Quinones-Cisneros, S.E.; Manero, O. [Univ. Nacional Autonoma de Mexico (Mexico). Dept. de Reologia, Inst. de Investigaciones en Materiales; Creek, J. [Chevron Energy Technology Co., Houston, TX (United States); Deiters, U.K. [Cologne Univ., Cologne (Germany). Inst. of Physical Chemistry
2008-07-01
Non-Newtonian rheological behaviour in crude oils can be induced by the presence of precipitated wax in reservoir fluids or by low ambient temperatures in heavy oils. This type of behaviour exists at low temperature operating conditions in deep-water production, or in the case of vapor extraction (VAPEX) processes of heavy oils involving strong compositional related changes to the already non-Newtonian viscosity of the oil. Reliable rheological models are needed for crude oils over the wide range of conditions that the fluid may encounter. The models should be of a compositional nature because the rheological behaviour of the fluid must be predicted in many applications, including VAPEX processes or fluid blending for piping. This study compared some published models that describe the non-Newtonian behaviour of crude oils. The emphasis was on the stability of the models predictions within the wide range of conditions that may be encountered. The study also evaluated the prediction potential of the analyzed models.
Garrido, M; Larrechi, M S; Rius, F X
2004-12-01
The present study investigates the relationship between the changes in complex viscosity and near-infrared spectra. Principal component regression analysis is applied to a near-infrared data set obtained from the in situ monitoring of the curing of diglycidyl ether of bisphenol A with the diamine 4,4'-diaminodiphenylmethane. The values of complex viscosity obtained by dynamic mechanical analysis during the cure process were used as a reference. The near-infrared spectra recorded throughout the reaction, unlike the univariate data analysis at some wavelengths of the spectra, contain a sufficient amount of information to estimate the complex viscosity. The relationship found was high and the results demonstrate the quality of the fitted model. Also, a simple user-friendly procedure for applying the model, focused on the user, is shown.
Experimental model for non-Newtonian fluid viscosity estimation: Fit to mathematical expressions
Guillem Masoliver i Marcos
2017-01-01
Full Text Available The construction process of a viscometer, developed in collaboration with a final project student, is here presented. It is intended to be used by first year's students to know the viscosity as a fluid property, for both Newtonian and non-Newtonian flows. Viscosity determination is crucial for the fluids behaviour knowledge related to their reologic and physical properties. These have great implications in engineering aspects such as friction or lubrication. With the present experimental model device three different fluids are analyzed (water, kétchup and a mixture with cornstarch and water. Tangential stress is measured versus velocity in order to characterize all the fluids in different thermal conditions. A mathematical fit process is proposed to be done in order to adjust the results to expected analytical expressions, obtaining good results for these fittings, with R2 greater than 0.88 in any case.
La Spina, G.; Polacci, M.; Burton, M.; de'Michieli Vitturi, M.
2017-09-01
Magma permeability is the most important factor controlling the transition between effusive and explosive styles during magma ascent at active volcanoes. When magma permeability is low, gas bubbles in the melt expand as the pressure decreases; above a critical gas volume fraction threshold, magma fragments, generating an explosive eruption. On the contrary, if magma is sufficiently permeable, gas ascends through the conduit towards the surface faster than the magma ascent speed, producing decoupling of gas and magma and reducing the maximum vesicularity. This decoupled flow inhibits fragmentation and leads to either an effusive eruption or quiescent degassing. Accurate modelling of permeability behaviour is therefore fundamental when simulating magma ascent processes. In this work, we compare different permeability models for low viscosity magmas using a 1D steady-state model. We use, as a test case, the 2007 effusive eruption at Stromboli volcano, Italy. We compare the numerical solutions computed using the linear Darcy's law with those obtained using the non-linear Forchheimer relation. Our numerical results show that, using Darcy's law and appropriate permeability models, it is possible to obtain an effusive eruption in agreement with observations. However, we found that, in the shallow conduit, the limit of applicability of Darcy's law (that is the modified Reynolds number Rem < 10) is exceeded due to high gas flow rates. Furthermore, we show that using Forchheimer's law and some parametric expressions for viscous and inertial permeabilities, results can be compatible with an effusive eruption, once appropriate values are chosen. However, one of the parameters required to obtain an effusive eruption, the friction coefficient between gas and melt, is several orders of magnitude lower than that determined from measurements of solid erupted samples. This result requires further experimental verification. We propose that our novel permeability modelling regime is
T. Salahuddin
2015-12-01
Full Text Available The purpose of present analysis is to examine the effects of temperature dependent viscosity and thermal conductivity on MHD stagnation point flow over a stretching cylinder. The momentum and the temperature equations are modeled by using tangent hyperbolic fluid and the effect of viscous dissipation is also considered. The requisite partial differential equations are metamorphosed into ordinary differential equations by using similarity transformations. The succeeding ordinary differential equations are solved by using shooting method. The physical behavior of non-dimensional parameters for momentum and temperature profiles is deliberated through graphs. The numerical values of skin friction coefficient and local Nusselt number are calculated in order to recognize the behavior of fluid near the surface. The comparison with previous literature is completed in order to check the accuracy of the present work. It is found the velocity reduces with increasing power law index, Weissenberg number, Hartmann number and variable viscosity parameter. With the increasing values of curvature parameter, velocity is found to increase. Variable thermal conductivity parameter and Prandtl number shows opposite behavior for temperature profile.
Liu, Haihu; Ju, Yaping; Wang, Ningning; Xi, Guang; Zhang, Yonghao
2015-09-01
Contact angle hysteresis is an important physical phenomenon omnipresent in nature and various industrial processes, but its effects are not considered in many existing multiphase flow simulations due to modeling complexity. In this work, a multiphase lattice Boltzmann method (LBM) is developed to simulate the contact-line dynamics with consideration of the contact angle hysteresis for a broad range of kinematic viscosity ratios. In this method, the immiscible two-phase flow is described by a color-fluid model, in which the multiple-relaxation-time collision operator is adopted to increase numerical stability and suppress unphysical spurious currents at the contact line. The contact angle hysteresis is introduced using the strategy proposed by Ding and Spelt [Ding and Spelt, J. Fluid Mech. 599, 341 (2008)JFLSA70022-112010.1017/S0022112008000190], and the geometrical wetting boundary condition is enforced to obtain the desired contact angle. This method is first validated by simulations of static contact angle and dynamic capillary intrusion process on ideal (smooth) surfaces. It is then used to simulate the dynamic behavior of a droplet on a nonideal (inhomogeneous) surface subject to a simple shear flow. When the droplet remains pinned on the surface due to hysteresis, the steady interface shapes of the droplet quantitatively agree well with the previous numerical results. Four typical motion modes of contact points, as observed in a recent study, are qualitatively reproduced with varying advancing and receding contact angles. The viscosity ratio is found to have a notable impact on the droplet deformation, breakup, and hysteresis behavior. Finally, this method is extended to simulate the droplet breakup in a microfluidic T junction, with one half of the wall surface ideal and the other half nonideal. Due to the contact angle hysteresis, the droplet asymmetrically breaks up into two daughter droplets with the smaller one in the nonideal branch channel, and the
Liu, Haihu; Ju, Yaping; Wang, Ningning; Xi, Guang; Zhang, Yonghao
2015-09-01
Contact angle hysteresis is an important physical phenomenon omnipresent in nature and various industrial processes, but its effects are not considered in many existing multiphase flow simulations due to modeling complexity. In this work, a multiphase lattice Boltzmann method (LBM) is developed to simulate the contact-line dynamics with consideration of the contact angle hysteresis for a broad range of kinematic viscosity ratios. In this method, the immiscible two-phase flow is described by a color-fluid model, in which the multiple-relaxation-time collision operator is adopted to increase numerical stability and suppress unphysical spurious currents at the contact line. The contact angle hysteresis is introduced using the strategy proposed by Ding and Spelt [Ding and Spelt, J. Fluid Mech. 599, 341 (2008), 10.1017/S0022112008000190], and the geometrical wetting boundary condition is enforced to obtain the desired contact angle. This method is first validated by simulations of static contact angle and dynamic capillary intrusion process on ideal (smooth) surfaces. It is then used to simulate the dynamic behavior of a droplet on a nonideal (inhomogeneous) surface subject to a simple shear flow. When the droplet remains pinned on the surface due to hysteresis, the steady interface shapes of the droplet quantitatively agree well with the previous numerical results. Four typical motion modes of contact points, as observed in a recent study, are qualitatively reproduced with varying advancing and receding contact angles. The viscosity ratio is found to have a notable impact on the droplet deformation, breakup, and hysteresis behavior. Finally, this method is extended to simulate the droplet breakup in a microfluidic T junction, with one half of the wall surface ideal and the other half nonideal. Due to the contact angle hysteresis, the droplet asymmetrically breaks up into two daughter droplets with the smaller one in the nonideal branch channel, and the behavior of
Bhatti, M M; Zeeshan, A; Ellahi, R
2016-12-01
In this article, heat transfer analysis on clot blood model of the particle-fluid suspension through a non-uniform annulus has been investigated. The blood propagating along the whole length of the annulus was induced by peristaltic motion. The effects of variable viscosity and slip condition are also taken into account. The governing flow problem is modeled using lubrication approach by taking the assumption of long wavelength and creeping flow regime. The resulting equation for fluid phase and particle phase is solved analytically and closed form solutions are obtained. The physical impact of all the emerging parameters is discussed mathematically and graphically. Particularly, we considered the effects of particle volume fraction, slip parameter, the maximum height of clot, viscosity parameter, average volume flow rate, Prandtl number, Eckert number and fluid parameter on temperature profile, pressure rise and friction forces for outer and inner tube. Numerical computations have been used to determine the behavior of pressure rise and friction along the whole length of the annulus. The present study is also presented for an endoscope as a special case of our study. It is observed that greater influence of clot tends to rise the pressure rise significantly. It is also found that temperature profile increases due to the enhancement in Prandtl number, Eckert number, and fluid parameter. The present study reveals that friction forces for outer tube have higher magnitude as compared to the friction forces for an inner tube. In fact, the results for present study can also be reduced to the Newtonian fluid by taking ζ → ∞.
Su, Kung-Yi; Hayward, Christopher C; Faucher-Giguere, Claude-Andre; Keres, Dusan; Ma, Xiangcheng; Robles, Victor H
2016-01-01
Using high-resolution simulations with explicit treatment of stellar feedback physics based on the FIRE (Feedback in Realistic Environments) project, we study how galaxy formation and the interstellar medium (ISM) are affected by magnetic fields, anisotropic Spitzer-Braginskii conduction and viscosity, and sub-grid turbulent metal diffusion. We consider controlled simulations of isolated (non-cosmological) galaxies but also a limited set of cosmological "zoom-in" simulations. Although simulations have shown significant effects from these physics with weak or absent stellar feedback, the effects are much weaker than those of stellar feedback when the latter is modeled explicitly. The additional physics have no systematic effect on galactic star formation rates (SFRs). In contrast, removing stellar feedback leads to SFRs being over-predicted by factors of $\\sim 10 -100$. Without feedback, neither galactic winds nor volume filling hot-phase gas exist, and discs tend to runaway collapse to ultra-thin scale-height...
Lanzafame, Giuseppe
2012-01-01
Physical damping, regarding the nonlinear Navier-Stokes viscous flow dynamics, refers to a tensorial turbulent dissipation term, attributed to adjacent moving macroscopic flow components. Mutual dissipation among these parts of fluid is described by a braking term in the momentum equation together with a heating term in the energy equation, both responsible of the damping of the momentum variation and of the viscous conversion of mechanical energy into heat. A macroscopic mixing scale length is currently the only characteristic length needed in the nonlinear modelling of viscous fluid dynamics describing the nonlinear eddy viscosity through the kinematic viscosity coefficient in the viscous stress tensor, without any reference to the chemical composition and to the atomic dimensions. Therefore, in this paper, we write a new formulation for the kinematic viscosity coefficient to the turbulent viscous physical dissipation in the Navier-Stokes equations, where molecular parameters are also included. Results of 2...
The effects of dissolved CO 2 on the density and viscosity of silicate melts: a preliminary study
Bourgue, Emmanuelle; Richet, Pascal
2001-11-01
A potassium silicate liquid with 56.9 mol% SiO 2 (KS 1.3) has been used as a model system to determine at 1 bar the influence of carbon dioxide on the viscosity and density of magma. For the maximum concentration of 3.5 wt% that could be dissolved, the viscosity decreases by two orders of magnitude near the glass transition at around 750 K. For 1 wt% CO 2, the decrease is 1 and only 0.04 log unit at 750 and 1500 K, respectively. Dissolved CO 2 has a composition independent partial molar volume of 25.6±0.8 cm 3/mol in glasses at room temperature, and does not affect the thermal expansion coefficient of the supercooled liquid which is (12.3±0.3)×10 -5 K -1 for CO 2 contents varying from 0.6 to 2.2 wt%. Qualitatively, these effects are similar to those of water. However, the density of dissolved CO 2 varies from about 1.7 to 1.5 g/cm 3 in a 700 K interval above the glass transition, and lowers the density of the glass less than water whose density decreases from 1.5 to 1.2 g/cm 3 under the same conditions. The relevance of these results to natural magma is finally pointed out.
EFFECT OF ANIONIC SURFACTANT UPON THE VISCOSITY OF POLYMER GUAR GUM SOLUTIONS
Xiao-ming Chen; Hai-yang Yang; Xian You; Ping-ping Zhu; Ping-sheng Hea
2006-01-01
The reduced viscosity of polymer guar gum solutions containing a certain concentration of sodium dodecyl benzene sulfonate (SDBS) was measured. It has been found that the Huggins coefficient kH of polymer solutions is verysensitive to the concentration of the surfactant, cSDBS, in solutions. If cSDBS is lower than CMC, the critical micelle concentration of SDBS, kH increases rapidly with cSDBS. On the other hand, if cSDBS is larger than CMC, kH decreases rapidly with cSDBS. Comparatively, the intrinsic viscosity of polymer solution does not show a notable change with cSDBS. The experimental results indicate that the interchain association of polymer guar gum in solution is greatly associated with SDBS interacted with polymer chains through hydrogen bonds. However, the effect of SDBS upon the intrachain association of polymer guar gum solution is negligible, presumably due to the fact that guar gum is a slightly stiffened random-coil chain polymer.
Ziółek, Marcin; Burdziński, Gotard; Douhal, Abderrazzak
2012-08-01
In this study, we report on the effects of solvent viscosity and polarity on the photochromic salicylaldehyde azine (SAA) molecule by examining the steady-state and UV-visible absorption results in the time scale from nanoseconds to hours, in solution and in a polymer film. For the neutral structure, the viscosity strongly affects the lifetime of the photochromic (trans-keto) tautomer by suppressing the second order quenching process, and thus increasing the photochrome lifetimes in highly viscous solvents to 500 μs in polar triacetine, and to 65 μs in non-polar squalane. Trapping SAA in a non-polar polymer film (polyethylene) results in further elongation of the photochromic lifetime (700 μs) by one order of magnitude (with respect to that in squalane), due to the retardation of the intramolecular back-isomerization. Another species, living significantly longer and absorbing more in the UV comparing to the photochrome, was identified as the syn-enol tautomer. The lifetime of this tautomer, created in a competitive mechanism to the photochrome creation, is much longer in non-polar solvents (hundreds of minutes) than in polar ones (tens of minutes), opposite to the trend observed for the photochrome. For the SAA anion, the transient living on the ns-μs time scale can be exclusively assigned to the triplet state, which is not observed for the neutral form at room temperature.
Effects of a physical fitness program on memory and blood viscosity in sedentary elderly men
H.K. Antunes
2015-01-01
Full Text Available The aim of this study was to investigate the effects of a 6-month exercise program on cognitive function and blood viscosity in sedentary elderly men. Forty-six healthy inactive men, aged 60–75 years were randomly distributed into a control group (n=23 and an experimental group (n=23. Participants underwent blood analysis and physical and memory evaluation, before and after the 6-month program of physical exercise. The control group was instructed not to alter its everyday activities; the experimental group took part in the fitness program. The program was conducted using a cycle ergometer, 3 times per week on alternate days, with intensity and volume individualized at ventilatory threshold 1. Sessions were continuous and maximum duration was 60 min each. There was significant improvement in memory (21%; P<0.05, decreased blood viscosity (−19%; P<0.05, and higher aerobic capacity (48%; P<0.05 among participants in the experimental group compared with the control group. These data suggest that taking part in an aerobic physical fitness program at an intensity corresponding to ventilatory threshold-1 may be considered a nonmedication alternative to improve physical and cognitive function.
Ruan, Qichao; Siddiqah, Nadia; Li, Xiaochen; Nutt, Steven; Moradian-Oldak, Janet
2015-01-01
We recently reported an amelogenin-chitosan (CS-AMEL) hydrogel as a promising biomimetic material for future in situ human enamel regrowth. To further optimize the necessary conditions for clinical applicability of CS-AMEL hydrogel, herein we studied the effects of viscosity and supersaturation degree on the size and orientation of synthetic crystals by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Raising the hydrogel viscosity by increasing chitosan concentration from 1% to 2% (w/v) improved the orientation of the crystals, while a higher supersaturation (σ(HAp) >10.06, [Ca2+] >5 mM) resulted in the formation of random crystals with larger sizes and irregular structures. We conclude that optimal conditions to produce organized enamel-like crystals in a CS-AMEL hydrogel are: 2% (w/v) chitosan, 2.5 mM calcium, and 1.5 mM phosphate (degree of supersaturation = 8.23) and 200 μg/ml of amelogenin. PMID:25158201
Ruan, Qichao; Siddiqah, Nadia; Li, Xiaochen; Nutt, Steven; Moradian-Oldak, Janet
2014-08-01
We recently reported an amelogenin-chitosan (CS-AMEL) hydrogel as a promising biomimetic material for future in situ human enamel regrowth. To further optimize the necessary conditions for clinical applicability of CS-AMEL hydrogel, herein we studied the effects of viscosity and supersaturation degree on the size and orientation of synthetic crystals by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Raising the hydrogel viscosity by increasing chitosan concentration from 1% to 2% (w/v) improved the orientation of the crystals, while a higher supersaturation (σ(HAp) >10.06, [Ca(2+)] >5 mM) resulted in the formation of random crystals with larger sizes and irregular structures. We conclude that optimal conditions to produce organized enamel-like crystals in a CS-AMEL hydrogel are: 2% (w/v) chitosan, 2.5 mM calcium, and 1.5 mM phosphate (degree of supersaturation = 8.23) and 200 µg/ml of amelogenin.
The Effects of Temperature, Viscosity, and Molecular Size on the Aluminum-27 QCT NMR of Transferrins
Aramini, James M.; Vogel, Hans J.
1996-02-01
A number of reports in recent years have demonstrated the feasibility of detecting quadrupolar metal ions bound tightly to rather large proteins via the quadrupolar central transition (QCT) NMR approach. In this article, an in-depth investigation of several interesting properties of transferrin-bound27Al NMR signals, namely, their dependence on temperature, viscosity, and molecular size is presented. It is shown that (1) decreasing temperature and (2) increasing viscosity by adding reagents such as glycerol and ethylene glycol perturb only the linewidths of transferrin-bound27Al signals, and, in fact, produce a decrease in signal linewidth. These effects are in accord with quadrupolar relaxation theory, which predicts that the linewidth of the central transition of a half-integer quadrupolar nucleus should decrease with increasing correlation time of the protein under nonextreme narrowing conditions. Furthermore, it is demonstrated that these trends, which are completely opposite to those generally observed in NMR spectroscopy, can be exploited to monitor ovotransferrin half-molecule reassociation reactions. In combination with the peculiar properties of transferrin-bound quadrupolar nuclei reported in the literature to date, the phenomena described here provide the basis for understanding the conditions and experimental parameters which may facilitate the application of the QCT NMR technique to the study of other quadrupolar nuclei and proteins.
Effect of viscosity of petroleum products on deformation properties of concrete
A.P. Svintsov
2014-11-01
Full Text Available This paper presents the results of studies of the effect of petroleum products, impregnating in concrete, on its deformation properties. Petroleum products, impregnating in concrete and reinforced concrete structures, have a negative impact on their strength and deformation characteristics. The negative impact of petroleum products on concrete and reinforced concrete is associated with changes in the hydration process of cement, as well as changes in the structure of the concrete. Strength and deformation characteristics of concrete change due to hydraulic pressure of petroleum products in the pores exerted on the skeleton of cement stone. In this aspect, the crucial point is the porosity of concrete as a permeability factor for petroleum products. One of the most important factors affecting the physical and mechanical characteristics of oil-impregnated concrete is their viscosity. In this paper, the mathematical description of the change of deformation depending on the relative viscosity of impregnating of petroleum products, the value of the axial load and the concrete class was proposed. The obtained results allow assessing changes in deformation characteristics of load-bearing concrete and reinforced concrete of industrial buildings, where petroleum products are used in the technological processes.
Fink, J.; Gault, D.; Greeley, R.
1984-01-01
Impact experiments in Newtonian fluids with a range of viscosities of 0.001 to 60 Pa s demonstrate that transient crater volume and shape depend on target viscosity as well as on gravity. Volume is reduced, and depth-to-diameter ratio is increased for cratering events in which viscosity plays a dominant role. In addition to being affected by target kinematic viscosity, viscous scaling is most strongly influenced by projectile diameter, less strongly by projectile velocity, and least strongly by gravity. In a planetary context, viscous effects can occur for craters formed by small or slow moving impacting bodies, low planetary surface densities, high surface viscosities, and low gravity values; conditions all likely for certain impacts into the icy satellites of Saturn and Jupiter, especially if liquid mantles were still present beneath solid crusts. Age dating based on crater counts and size-frequency distributions for these icy bodies may have to be modified to account for the possibility that viscosity-dominated craters were initially smaller and deeper than their gravity-controlled counterparts.
The Effect of Copper Addition on the Fluidity and Viscosity of an Al-Mg-Si Alloy
Heidarzadeh, A.; Emamy, M.; Rahimzadeh, A.; Soufi, R.; Sohrabi Baba Heidary, D.; Nasibi, Sh.
2013-12-01
This study was undertaken to investigate the effect of Cu addition on the fluidity and viscosity of Al-%15Mg2Si in-situ metal matrix composite. The flowability of the composites was studied by measuring strip fluidity, cast in a permanent mold. The effect of casting parameters such as casting and mold temperatures on fluidity was studied. After obtaining an optimum condition for casting and mold temperatures, the effect of Cu addition on the fluidity and viscosity was studied. DSC thermal analysis was applied for studying the effect of Cu on solidification characteristics. Also, composites were characterized by optical and scanning electron microscopy (SEM). The results showed that casting fluidity of composites increases with the increase of mold and melt temperatures, but decreases with increase of Cu addition. Similarly, the viscosity of composites was increased by adding Cu content. The main effect of Cu was on the solidification mode.
Renormalization Group Flow, Stability, and Bulk Viscosity in a Large N Thermal QCD Model
Dasgupta, Keshav; Gale, Charles; Richard, Michael
2016-01-01
The ultraviolet completion of a large N QCD model requires introducing new degrees of freedom at certain scale so that the UV behavior may become asymptotically conformal with no Landau poles and no UV divergences of Wilson loops. These UV degrees of freedom are represented by certain anti-branes arranged on the blown-up sphere of a warped resolved conifold in a way that they are separated from the other set of branes that control the IR behavior of the theory. This separation of the branes and the anti-branes creates instability in the theory. Further complications arise from the curvature of the ambient space. We show that, despite these analytical hurdles, stability may still be achieved by switching on appropriate world-volume fluxes on the branes. The UV degrees of freedom, on the other hand, modify the RG flow in the model. We discuss this in details by evaluating the flow from IR confining to UV conformal. Finally we lay down a calculational scheme to study bulk viscosity which, in turn, would signal t...
Bianchi Type-I String Cosmological Model with Bulk Viscosity and Time-Dependent A term
R.K.Tiwari; S.Sharma
2011-01-01
Einstein Geld equations with the cosmological constant is considered in the presence of bulk viscosity in a Bianchi type-I universe. Solutions of the field equations are obtained by assuming the following conditions: the bulk viscosity is proportional to the expansion scalar ￡ oc 0; the expansion scalar is proportional to shear scalar 6 oc cr; and A is proportional to the Hubble parameter A on H. The corresponding interpretations of the cosmological solutions are also discussed.%@@ Einstein field equations with the cosmological constant is considered in the presence of bulk viscosity in a Bianchi type-I universe.Solutions of the field equations are obtained by assuming the following conditions:the bulk viscosity is proportional to the expansion scalar ξ∝θ;the expansion scalar is proportional to shear scalar θ∝σ;and ∧ is proportional to the Hubble parameter ∧∝ H.The corresponding interpretations of the cosmological solutions are also discussed.
Laskowski, Gregory Michael
2005-12-01
Flows with strong curvature present a challenge for turbulence models, specifically eddy viscosity type models which assume isotropy and a linear and instantaneous equilibrium relation between stress and strain. Results obtained from three different codes and two different linear eddy viscosity turbulence models are compared to a DNS simulation in order to gain some perspective on the turbulence modeling capability of SIERRA/Fuego. The Fuego v2f results are superior to the more common two-layer k-e model results obtained with both a commercial and research code in terms of the concave near wall behavior predictions. However, near the convex wall, including the separated region, little improvement is gained using the v2f model and in general the turbulent kinetic energy prediction is fair at best.
Modelling transverse turbulent mixing in a shallow flow by using an eddy viscosity approach
Gualtieri, C.
2009-04-01
The mixing of contaminants in streams and rivers is a significant problem in environmental fluid mechanics and rivers engineering since to understand the impact and the fate of pollutants in these water bodies is a primary goal of water quality management. Since most rivers have a high aspect ratio, that is the width to depth ratio, discharged pollutants become vertically mixed within a short distance from the source and vertical mixing is only important in the so-called near-field. As a rule of thumb, neutrally buoyant solute becomes fully mixed vertically within 50-75 depths from the source. Notably, vertical mixing analysis relies on well-known theoretical basis, that is Prandtl mixing length model, which assumes the hypothesis of plane turbulent shear flow and provides theoretical predictions of the vertical turbulent diffusivity which closely match experimental results. In the mid-field, the vertical concentration gradients are negligible and both subsequent transverse and longitudinal changes of the depth-averaged concentrations of the pollutants should be addressed. In the literature, for the application of one-dimensional water quality models the majority of research efforts were devoted to estimate the rate of longitudinal mixing of a contaminant, that is the development of a plume resulting from a temporally varying pollutant source once it has become cross-sectionally well-mixed, in the far-field. Although transverse mixing is a significant process in river engineering when dealing with the discharge of pollutants from point sources or the mixing of tributary inflows, no theoretical basis exists for the prediction of its rate, which is indeed based upon the results of experimental works carried on in laboratory channels or in streams and rivers. Turbulence models based on the eddy viscosity approach, such as the k-É model, k-? and their variation are the most widely used turbulence models and this is largely due to their ease in implementation
K. Hooman; H. Gurgenci
2007-01-01
Effect of temperature-dependent viscosity on fully developed forced convection in a duct of rectangular cross-section occupied by a fluid-saturated porous medium is investigated analytically. The Darcy flow model is applied and the viscosity-temperature relation is assumed to be an inverse-linear one. The case of uniform heat flux on the walls,i.e. the H boundary condition in the terminology of Kays and Crawford [12], is treated.For the case of a fluid whose viscosity decreases with temperature, it is found that the effect of the variation is to increase the Nusselt number for heated wails. Having found the velocity and the temperature distribution, the second law of thermodynamics is invoked to find the local and average entropy generation rate. Expressions for the entropy generation rate, the Bejan number, the heat transfer irreversibility, and the fluid flow viscosity variation number, the dimensionless wall heat flux, and the aspect ratio (width to height ratio). These expressions let a parametric study of the problem based on which it is observed that the entropy generated due to flow in a duct of square cross-section is more than those of rectangular counterparts while increasing the aspect ratio decreases the entropy generation rate similar to what previously reported for the clear flow case by Ratts and Raut [14].
Jung, Ilyong; Valles, James M.
2013-03-01
Previous studies have shown that paramecia exhibit negative gravi-kinesis. They exert a stronger propulsive force when swimming up than when swimming down. This behavior is very surprising since it suggests they sense their tiny apparent weight of only ~ 80pN. In an effort to understand the mechanism of this sensing, we are testing how the viscosity of the swimming medium influences their gravi-kinetic response. We employ the technique of magnetic force buoyancy variation to simulate different effective gravity levels on swimming Paramecia. We are analyzing their swimming response employing a phenomenological model that relates the parameters describing their helical trajectories to the beating of their cilia. This work was supported by NSF PHY0750360 and at the NHMFL by NSF DMR-0084173
Barnhoorn, A.; van der Wal, W.; Drury, M. R.
2012-04-01
The Vatnajökull glacier, located in the south-east of Iceland is the largest ice cap of Iceland having a mean radius of ~50 km covering an area of ˜8100 km2. The Vatnajökull glacier is situated directly on top of the spreading axis in the eastern volcanic zone (EVZ) of the Icelandic mid-ocean ridge and near the inferred center of the Icelandic hotspot. Due to the vicinity of the glacier to the active tectonic area, the response of the solid earth to melting of the ice cap is strongly controlled by the properties of the hot newly formed upper mantle underneath the mid-ocean ridge. The relatively high temperatures in the mantle during rifting result in relatively low upper mantle viscosities and fast relaxation times in comparison with tectonically inactive glaciated areas such as in. In this study, estimates for lithospheric thickness and upper mantle viscosity under Iceland are produced by a microphysical modelling approach using the theoretical temperature distribution under mid-ocean ridges combined with olivine diffusion and dislocation creep flow laws. Large lateral variations in upper mantle viscosity and especially lithospheric thickness are expected for Iceland perpendicular to the ridge axis due to the large changes in temperatures away from the ridge axis. The lithospheric thickness (27-40 km) and upper mantle viscosity (2 × 1018-1019 Pa s) outcomes for the recent glaciation are consistent with previous reports of viscosity and lithospheric thickness from glacial isostatic adjustment studies. A combination of a 40 km thick elastic lithosphere and an average upper mantle viscosity of 5 × 1018 Pa s would suggest that the upper mantle under Iceland is most likely dry. Also, the results indicate that the presence of a plume under Iceland cannot explain the recent low viscosity values reported for Iceland. Using a larger extent and larger thickness of the Icelandic icecap during the Weichselian glaciation event (˜10,000 BP) this study predicts that during
Room-temperature ionic liquids: slow dynamics, viscosity, and the red edge effect.
Hu, Zhonghan; Margulis, Claudio J
2007-11-01
Ionic liquids (ILs) have recently attracted significant attention from academic and industrial sources. This is because, while their vapor pressures are negligible, many of them are liquids at room temperature and can dissolve a wide range of polar and nonpolar organic and inorganic molecules. In this Account, we discuss the progress of our laboratory in understanding the dynamics, spectroscopy, and fluid dynamics of selected imidazolium-based ILs using computational and analytical tools that we have recently developed. Our results indicate that the red edge effect, the non-Newtonian behavior, and the existence of locally heterogeneous environments on a time scale relevant to chemical and photochemical reactivity are closely linked to the viscosity and highly structured character of these liquids.
Oluwole D. Makinde
2015-11-01
Full Text Available In this paper, we employed both first and second laws of thermodynamics to analyze the flow and thermal decomposition in a variable viscosity Couette flow of a conducting fluid in a rotating system under the combined influence of magnetic field and Hall current. The non-linear governing differential equations are obtained and solved numerically using shooting method coupled with fourth order Runge–Kutta–Fehlberg integration technique. Numerical results obtained for velocities and temperature profiles are utilized to determine the entropy generation rate, skin fictions, Nusselt number and the Bejan number. By plotting the graphs of various values of thermophysical parameters, the features of the flow characteristics are analyzed in detail. It is found that fluid rotation increases the dominant effect of heat transfer irreversibility at the upper moving plate region while the entropy production is more at the lower fixed plate region.
Effect of Viscosity on the GTA Welds Bead Penetration in Relation with Surface Tension Elements
K. Touileb
2016-04-01
Full Text Available The aim of this paper is to study the effect of the viscous dissipation on the surface tension and its role on the shape of weld pool. Experiments were conducted on four different casts of ferritic stainless steel with different content in the sulfur and titanium. The results show in particular that the presence of titanium solid compounds affects the role of sulfur as surfactant element. Titanium in the presence of carbon and oxygen, titanium forms solid compounds which affect the Marangoni convection due to the sulfur element in the weld pool. The viscous dissipation due to these compounds alters the flow rate of the molten metal. We expect that the viscosity of metal liquid was altered by these solid compounds. The viscous dissipation due to these compounds contributes to heat the molten metal leading to larger weld bead.
Hickey, M. P.
1988-01-01
The chemical-dynamical model of Walterscheid et al. (1987), which describes wave-driven fluctuations in OH nightglow, was modified to include the effects of both eddy thermal conduction and viscosity, as well as the Coriolis force (with the shallow atmosphere approximation). Using the new model, calculations were performed for the same nominal case as used by Walterscheid et al. but with only wave periods considered. For this case, the Coriolis force was found to be unimportant at any wave period. For wave periods greater than 2 or 3 hours, the inclusion of thermal conduction alone greatly modified the results (in terms of a complex ratio 'eta' which expresses the relationship between the intensity oscillation about the time-averaged intensity and the temperature oscillation about the time-averaged temperature); this effect was reduced with the further inclusion of the eddy viscosity.
Effects of activation energy and activation volume on the temperature-dependent viscosity of water
Kwang-Hua, Chu Rainer
2016-08-01
Water transport in a leaf is vulnerable to viscosity-induced changes. Recent research has suggested that these changes may be partially due to variation at the molecular scale, e.g., regulations via aquaporins, that induce reductions in leaf hydraulic conductance. What are the quantitative as well as qualitative changes in temperature-dependent viscosity due to the role of aquaporins in tuning activation energy and activation volume? Using the transition-state approach as well as the boundary perturbation method, we investigate temperature-dependent viscosity tuned by activation energy and activation volume. To validate our approach, we compare our numerical results with previous temperature-dependent viscosity measurements. The rather good fit between our calculations and measurements confirms our present approach. We have obtained critical parameters for the temperature-dependent (shear) viscosity of water that might be relevant to the increasing and reducing of leaf hydraulic conductance. These parameters are sensitive to temperature, activation energy, and activation volume. Once the activation energy increases, the (shear) viscosity of water increases. Our results also show that as the activation volume increases (say, 10-23m3 ), the (shear) viscosity of water decreases significantly and the latter induces the enhancing of leaf hydraulic conductance. Within the room-temperature regime, a small increase in the activation energy will increase the water viscosity or reduce the leaf hydraulic conductance. Our approach and results can be applied to diverse plant or leaf attributes.
The effect of a power-law mantle viscosity on trench retreat rate
Holt, Adam F.; Becker, Thorsten W.
2017-01-01
The subduction of lithospheric plates is partitioned between subducting plate motion and lateral slab migration (i.e. trench retreat and advance). We use 3-D, dynamic models of subduction to address the role of a power-law mantle viscosity on subduction dynamics and, in particular, rates of trench retreat. For all numerical models tested, we find that a power-law rheology results in reduced rates of trench retreat, and elevated slab dip angles, relative to the equivalent isoviscous mantle model. We analyse the asthenospheric pressure distribution and the style of mantle flow, which exhibits only limited variability as a function of mantle rheology, in order to compute estimates of the mantle forces associated with subduction. The inclusion of a power-law rheology reduces the mantle shear force (which resists subducting plate motion) to a greater degree than it reduces the dynamic pressure gradient across the slab (which resists trench retreat). Therefore, the inclusion of a power-law mantle rheology favours a shift towards a subduction mode with a reduced trench retreat component, typically a relative reduction of order 25 per cent in our 3-D models. We suggest that this mechanism may be of importance for reducing the high trench retreat rates observed in many previous models to levels more in line with the average subduction partitioning observed on Earth at present (i.e. trench velocity ≤ plate velocity), for most absolute plate motion reference frames.
Effect of viscosity on the shaking-induced fluidization in a liquid-immersed granular medium.
Yasuda, Nao; Sumita, Ikuro
2016-02-01
of the linear stability analyses for Rayleigh-Taylor instability. Using the measured λ and p, we infer that (i) only a thin layer beneath the two-layer boundary is mobile and the rest of the lower layer remains jammed and (ii) the effective viscosity of the upper granular layer relative to the liquid is smaller for the HV case as a result of smaller friction.
Effect of Cerium on the Viscosity of Liquid Fe-C Alloy of Eutectic Content
滕新营; 叶以富; 刘含莲; 王焕荣; 石志强; 耿浩然
2002-01-01
The viscosities of liquid Fe-4.30C and Fe-4.30C-Ce alloys were measured by oscillating crucible viscometer. The results show that viscosity of Fe-4.30C alloy changes from 5.50 to 8.30 MPa*s when the liquid is cooled from 1425 ℃ to the melting point. The abnormity of viscosity of Fe-4.30C alloy near the melting point is reasonable due to the formation of graphite. The addition of cerium especially with content higher than 0.21% causes an evidently decrease in viscosity for eutectic alloy resulting from increase of free volume and size decrease of atom cluster in the liquids. It can be concended that the existence of C-Ce compound contributes to the discontinuous of viscosity at 1340～1370 ℃ for the Fe-4.30C-Ce alloy by experinments with differential scanning calorimeter.
Aliste, Antonio J.; Del Mastro, Nelida L. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)
1999-11-01
The application of food radiation processing is increasing worldwide mainly because of its efficiency in the industrial decontamination of packaged food products. Indeed, the process neither introduces any undesirable elements nor increases the temperature, thus allowing the preparation of ready-to-use products which remain stable for long periods at room temperature. The aim of this work was to study the effect of Co-60 gamma radiation on the viscosity of agar. This hydrocolloid derived from seaweed is a galactose polymer with a high hysteresis capacity (great difference among melting and gelification temperature) which is extremely important when used as additive for the food industry. Commercial agar was irradiated with doses of 0, 1, 5 and 10 kGy. Proper dilutions were prepared and the viscosity was measured in a Brookfield model LVDVIII viscosimeters. The relationships viscosity/dose for the temperatures of 45 deg C and 60 deg C were established. The decrease of the viscosity was 71.4% and 49.6% respectively when the applied dose was 10 kGy. The implications of the use of this additive in food irradiation are discussed. (author) 9 refs., 2 figs.
Welty, C. (Drexel Univ., Philadelphia, PA (United States)); Gelhar, L.W. (Massachusetts Inst. of Tech., Cambridge (United States))
1991-08-01
Both porous medium heterogeneities and fluid density and viscosity contrasts affect solute transport in miscible fluid displacement. The effect of interaction of these processes on large-scale mixing are evaluated using spectral-based perturbation theory. A three-dimensional, statistically isotropic, exponential log permeability autocovariance is used to represent the spatial variability of the porous medium. State equations linearly relating log density and log viscosity perturbations to concentration perturbations represent the density and viscosity variability and strongly couple the flow and solute transport perturbation equations. Analytical expressions for longitudinal macrodispersivity, derived for one-dimensional mean solute transport, are functionally dependent on mean displacement distance, mean concentration and concentration gradient, density and viscosity differences, mean velocity, gravity, and correlation scale and variance of the log permeability process. Transient analysis shows that longitudinal macrodispersivity grows exponentially in time (or mean displacement distance) without bound for the case where instabilities due to viscous or gravity fingering arise (the unstable or fingering case) and that it grows at early time then decreases exponentially to an asymptotic value close to that of local dispersivity for the case where density or viscosity contrasts produce a stabilizing effect (the stable case).
Huang, Hsin-Fu; Zahn, Markus; LEMAIRE, Elisabeth
2010-01-01
International audience; A continuum mechanical model is presented to analyze the negative electrorheological responses of a particle-liquid mixture with the suspended micro-particles undergoing Quincke rotation for both Couette and Poiseuille flow geometries by combining particle electromechanics and continuum antisymmetric/couple stress analyses in the zero spin viscosity limit. We propose a phenomenological polarization relaxation model to incorporate both the micro-particle rotation speed ...
Shayganpour, A.; Idris, M. H.; Izman, S.; Farahany, S.
2012-06-01
The effects of pouring temperature and slurry viscosity in terms of heat transfer on surface roughness during lost foam casting (LFC) of LM6 alloy were investigated experimentally. Heat transfer of molten materials is an important factors to changes the microstructure which is considered in the present study. It is primarily dependent on the pouring temperature, casting thickness, mould material, mould temperature and surrounding medium. The pouring temperature changed from 700 to740°C and slurry viscosity altered from 20 to 36 sec. A full 2-level factorial design experimental technique was used to identify the significant factors that effect on surface roughness of castings. The results show that surface roughness improved by lower pouring temperature, whereas slurry viscosity has less influence on the quality of surface.
Zhou, C L; Fang, D Q; Zhang, G Q
2013-01-01
Thermodynamic and transport properties of nuclear fireball created in the central region of heavy-ion collisions below 200 MeV/nucleon are investigated within the isospin-dependent quantum molecular dynamic (IQMD) model. These properties include time evolutions of the density, temperature, chemical potential, entropy density ($s$) and shear viscosity ($\\eta$) as well as density and temperature dependencies of the ratio of shear viscosity over entropy density ($\\eta/s$) etc. Based on the shear viscosity parametrization developed by Danilewicz and entropy density which is obtained by a generalized hot Thomas Fermi formalism, the ratio of shear viscosity over entropy density is calculated in the whole collision process as well as in the freeze-out stage. With the collision goes on, a transient minimal $\\eta/s$ with the value around 5/$4\\pi$ occurs in the largest compression stage. While, the relationship of $\\eta/s$ to tempertaure ($T$) in the freeze-out stage displays a local minimum which is about 9-10 times $...
E. J. Suarez-Dominguez
2016-12-01
Full Text Available Production of heavy crude oil in Mexico, and worldwide, is increasing which has led to the application of different methods to reduce viscosity or to enhance transport through stratified flow to continue using the existing infrastructures. In this context, injecting a viscosity improver that does not mix completely with the crude, establishes a liquid-liquid stratified flow. On the basis of a parallel plates model, comparing the increase of flow that occurs in the one-phase case which assumes a complete mixture between the crude and the viscosity improver against another stratified liquid-liquid (no mixing between the oil and compared improver; it was found that in both cases there is a flow increase for the same pressure drop with a maximum for the case in which the flow improver is between the plates and the crude.
Jiang, Fei
2016-11-01
In this article, we investigate the effect of viscosity on the largest growth rate in the linear Rayleigh-Taylor (RT) instability of a three-dimensional nonhomogeneous incompressible viscous flow in a bounded domain. By adapting a modified variational approach and careful analysis, we show that the largest growth rate in linear RT instability tends to zero as the viscosity coefficient goes to infinity. Moreover, the largest growth rate increasingly converges to one of the corresponding inviscid fluids as the viscosity coefficient goes to zero. Applying these analysis techniques to the corresponding viscous magnetohydrodynamic fluids, we can also show that the largest growth rate in linear magnetic RT instability tends to zero as the strength of horizontal (or vertical) magnetic field increasingly goes to a critical value.
De Loubens, Clément; Doyennette, Marion; Tréléa, Ioan Cristian; Souchon, Isabelle
2013-01-01
After swallowing a liquid or a semi-liquid food product, a thin film responsible for the dynamic profile of aroma release coats the pharyngeal mucosa. The objective of the present article was to understand and quantify physical mechanisms explaining pharyngeal mucosa coating. An elastohydrodynamic model of swallowing was developed for Newtonian liquids that focused on the most occluded region of the pharyngeal peristaltic wave. The model took lubrication by a saliva film and mucosa deformability into account. Food bolus flow rate and generated load were predicted as functions of three dimensionless variables: the dimensionless saliva flow rate, the viscosity ratio between saliva and the food bolus, and the elasticity number. Considering physiological conditions, the results were applied to predict aroma release kinetics. Two sets of conditions were distinguished. The first one was obtained when the saliva film is thin, in which case food bolus viscosity has a strong impact on mucosa coating and on flavour rel...
How emulsions composition and structure affect sensory perception of low-viscosity model emulsions
Vingerhoeds, M.H.; Wijk, de R.A.; Zoet, F.D.; Nixdorf, R.R.; Aken, van G.A.
2008-01-01
The oral residence time of low-viscosity emulsions, like milk, is relatively short. Despite this short residence time, people can easily perceive differences between these emulsions. Our research is dedicated to unravel the oral behaviour of emulsions in relation to sensory perception. The aim of
How emulsions composition and structure affect sensory perception of low-viscosity model emulsions
Vingerhoeds, M.H.; Wijk, de R.A.; Zoet, F.D.; Nixdorf, R.R.; Aken, van G.A.
2008-01-01
The oral residence time of low-viscosity emulsions, like milk, is relatively short. Despite this short residence time, people can easily perceive differences between these emulsions. Our research is dedicated to unravel the oral behaviour of emulsions in relation to sensory perception. The aim of th
A HAMMADI
2002-12-01
Full Text Available Viscosity B‑coefficients in glycerol obtained at 25 °C for many salts by a rearrangement in the Jones‑Dole expression are compared with those calculated applying existing theories, based on the model of hard‑charged spheres moving in a solvent continuum. Specific agreement between theory and experiment was not generally good. While the results show that Einstein’s relation can be applied to large aqueous ions, provided that the true volume‑fraction of the ions in solution can be ascertained; this expression does not lead to accurate B‑values in glycerol. For the ion‑size dependence of the B‑coefficient in aqueous solutions, Clark’s theoretical predictions agree with experiments qualitatively, in the case of glycerol, however, the model shows limitations even for small ions, for which the dielectric friction theory is expected to be applicable. Finally, all the above theories give a positive B‑coefficient, while experimental evidences showed that B could be negative.
The systematic study of the effect of binder viscosity on the sensitivity of a tyrosinase-based carbon paste electrode (CPE) biosensor for phenol and catechol is reported. Silicon oil binders with similar (polydimethylsiloxane) chemical composition were used to represent a wid...
Amador, Julia; Hartel, Rich; Rankin, Scott
2017-08-01
The purpose of this work was to investigate iciness perception and other sensory textural attributes of ice cream due to ice and fat structures and mix viscosity. Two studies were carried out varying processing conditions and mix formulation. In the 1st study, ice creams were collected at -3, -5, and -7.5 °C draw temperatures. These ice creams contained 0%, 0.1%, or 0.2% emulsifier, an 80:20 blend of mono- and diglycerides: polysorbate 80. In the 2nd study, ice creams were collected at -3 °C draw temperature and contained 0%, 0.2%, or 0.4% stabilizer, a blend of guar gum, locust bean gum, and carrageenan. Multiple linear regressions were used to determine relationships between ice crystal size, destabilized fat, and sensory iciness. In the ice and fat structure study, an inverse correlation was found between fat destabilization and sensory iciness. Ice creams with no difference in ice crystal size were perceived to be less icy with increasing amounts of destabilized fat. Destabilized fat correlated inversely with drip-through rate and sensory greasiness. In the ice cream mix viscosity study, an inverse correlation was found between mix viscosity and sensory iciness. Ice creams with no difference in ice crystal size were perceived to be less icy when formulated with higher mix viscosity. A positive correlation was found between mix viscosity and sensory greasiness. These results indicate that fat structures and mix viscosity have significant effects on ice cream microstructure and sensory texture including the reduction of iciness perception. © 2017 Institute of Food Technologists®.
The role of fluctuations and stress on the effective viscosity of cell aggregates.
Marmottant, Philippe; Mgharbel, Abbas; Käfer, Jos; Audren, Benjamin; Rieu, Jean-Paul; Vial, Jean-Claude; van der Sanden, Boudewijn; Marée, Athanasius F M; Graner, François; Delanoë-Ayari, Hélène
2009-10-13
Cell aggregates are a tool for in vitro studies of morphogenesis, cancer invasion, and tissue engineering. They respond to mechanical forces as a complex rather than simple liquid. To change an aggregate's shape, cells have to overcome energy barriers. If cell shape fluctuations are active enough, the aggregate spontaneously relaxes stresses ("fluctuation-induced flow"). If not, changing the aggregate's shape requires a sufficiently large applied stress ("stress-induced flow"). To capture this distinction, we develop a mechanical model of aggregates based on their cellular structure. At stress lower than a characteristic stress tau*, the aggregate as a whole flows with an apparent viscosity eta*, and at higher stress it is a shear-thinning fluid. An increasing cell-cell tension results in a higher eta* (and thus a slower stress relaxation time t(c)). Our constitutive equation fits experiments of aggregate shape relaxation after compression or decompression in which irreversibility can be measured; we find t(c) of the order of 5 h for F9 cell lines. Predictions also match numerical simulations of cell geometry and fluctuations. We discuss the deviations from liquid behavior, the possible overestimation of surface tension in parallel-plate compression measurements, and the role of measurement duration.
Scaling of the viscosity of the Lennard-Jones chain fluid model, argon, and some normal alkanes.
Galliero, Guillaume; Boned, Christian; Fernández, Josefa
2011-02-14
In this work, we have tested the efficiency of two scaling approaches aiming at relating shear viscosity to a single thermodynamic quantity in dense fluids, namely the excess entropy and the thermodynamic scaling methods. Using accurate databases, we have applied these approaches first to a model fluid, the flexible Lennard-Jones chain fluid (from the monomer to the hexadecamer), then to real fluids, such as argon and normal alkanes. To enlarge noticeably the range of thermodynamics conditions for which these scaling methods are applicable, we have shown that the use of the residual viscosity instead of the total viscosity is preferable in the scaling procedures. It has been found that both approaches, using the adequate scaling, are suitable for the Lennard-Jones chain fluid model for a wide range of thermodynamic conditions whatever the chain length when scaling law exponents and prefactors are adjusted for each chain length. Furthermore, these results were found to be well respected by the corresponding real fluids.
Non-Newtonian Viscosity Modeling of Crude Oils—Comparison Among Models
Ramírez-González, Patsy V.; Aguayo, Juan Pablo; Quiñones-Cisneros, Sergio E.; Deiters, Ulrich K.
2009-04-01
The presence of precipitated wax or even just low temperatures may induce non-Newtonian rheological behavior in crude oils. Such behavior can be found at operating conditions, for instance, in reservoirs at deep-water conditions. Therefore, reliable rheological models for crude oils applicable over the wide range of conditions the fluid may encounter are essential for a large number of oil technology applications. Such models must also be composition dependent, as many applications require predicting the rheological behavior of the fluid under strong compositional changes, e.g., recovery applications such as vapor extraction (VAPEX) processes or blending of fluids for improved rheological characteristics for piping, among many other applications. In this study, a comparative analysis between some published models applicable to the description of the non-Newtonian behavior of crude oils is carried out. Emphasis is placed on the stability of the model predictions within the wide range of conditions that may be encountered.
A Model for Hydrogen Thermal Conductivity and Viscosity Including the Critical Point
Wagner, Howard A.; Tunc, Gokturk; Bayazitoglu, Yildiz
2001-01-01
In order to conduct a thermal analysis of heat transfer to liquid hydrogen near the critical point, an accurate understanding of the thermal transport properties is required. A review of the available literature on hydrogen transport properties identified a lack of useful equations to predict the thermal conductivity and viscosity of liquid hydrogen. The tables published by the National Bureau of Standards were used to perform a series of curve fits to generate the needed correlation equations. These equations give the thermal conductivity and viscosity of hydrogen below 100 K. They agree with the published NBS tables, with less than a 1.5 percent error for temperatures below 100 K and pressures from the triple point to 1000 KPa. These equations also capture the divergence in the thermal conductivity at the critical point
Viscosity and medium effects on the fluorescence and photochemical behaviour of some aryl chalcones
Ebeid, El-Zeiny M.; Abdel-Kader, Mahmood H.; Issa, Raafat M.; El-Daly, Samy A.
1988-05-01
The emission, excitation and absorption spectra toghether with the fluorescence and photochemical quantum yields of some chalcone derivatives have been studied in organic solvents and micellar and microemulsion media. Both 4-[2-(2-pyridyl)ethenyl] ( I) and 4-[2-(4-pyridyl)ethenyl ( II) chalcones show large positive solvatochromic effects. The fluorescence quantum yields increase substantially as the medium viscosity increases with a subsequent decrease in the photochemical quatum yield. Compounds I and II undergo excited-state molecular aggregation in concentrated solutions giving excimer-like emission that coincides with emission from crystalline samples. The enthalpies of photoassociation have been estimated. The chalcone derivative I acts as an efficient quencher of the fluorescence of the laser dye 1,4-bis (β-pyridyl-2-vinyl)benzene via a long-range mechanism. The excited-state lifetimes of both I and II are short and at 20°C their τ values are less than 800 ps.
Hodas, N.; Zuend, A.; Shiraiwa, M.; Flagan, R. C.; Seinfeld, J.; Schilling, K.; Berkemeier, T.
2015-12-01
The presence of oligomers in biomass burning aerosol, as well as secondary organic aerosol derived from other sources, influences particle viscosity and can introduce kinetic limitations to water uptake. This, in turn, impacts aerosol optical properties and the efficiency with which these particles serve as cloud condensation nuclei (CCN). To explore the influence of organic-component viscosity on aerosol hygroscopicity, the water-uptake behavior of aerosol systems comprised of polyethylene glycol (PEG) and mixtures of PEG and ammonium sulfate (AS) was measured under sub- and supersaturated relative humidity (RH) conditions. Experiments were conducted with systems containing PEG with average molecular weights ranging from 200 to 10,000 g/mol, corresponding to a range in viscosity of 0.004 - 4.5 Pa s under dry conditions. While evidence suggests that viscous aerosol components can suppress water uptake at RH activity with increasing PEG molecular weight was observed. We attribute this to an increase in the efficiency with which PEG serves as a surfactant with increasing molecular weight. This effect is most pronounced for PEG-AS mixtures and, in fact, a modest increase in CCN activity is observed for the PEG 10,000-AS mixture as compared to pure AS, as evidenced by a 4% reduction in critical activation diameter. Experimental results are compared with calculations of hygroscopic growth at thermodynamic equilibrium using the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients model and the potential influence of kinetic limitations to observed water uptake is further explored with the Kinetic Multi-Layer Model of Gas-Particle Interactions. Results suggest the competing effects of organic-component viscosity and surface-tension depression may lead to RH-dependent differences in hygroscopicity for oligomers and other surface-active compounds present in atmospheric aerosols, for which PEG serves as a surrogate in these experiments.
Effects of Resistivity and Viscosity on m =0 Rise and Fall Time in the RFP
Futch, A. M.; Craig, D.; Hesse, R.; Jacobson, C. M.
2016-10-01
In the reversed field pinch (RFP), poloidal mode number m =0 fluctuations are driven in a sawtooth cycle via nonlinear coupling with unstable m =1 tearing modes. We explore how the rise and fall time of these m =0 fluctuations depends on resistivity and viscosity in visco-resistive MHD simulations using the DEBS code. Both the Lundquist number (S) and magnetic Prandtl number (Pr) affect the rise/fall time. Analysis of MST experimental data also shows that both the rise and fall times of the m =0 amplitude vary with S. The variation observed in experiment is consistent with simulation results for rise time, but shows some differences for fall time. Rise time is insensitive to the resistivity profile but depends slightly on the viscosity profile. Fall time is strongly correlated with the duration of the crash which depends on both resistivity and viscosity profiles. These results suggest that the rise and fall time of the m =0 modes at the sawtooth crash is not strongly influenced by the local resistivity near the resonant surface but instead is primarily determined by the overall dynamics of the entire sawtooth cycle. The role of viscosity is less clear though the edge viscosity affects the m =0 evolution more than the core. This work has been supported by the U.S.D.O.E.
Nardone, Erika; Dey, Tania; Kevan, Peter G
2013-09-01
Nectar is an essential resource for bumblebees and many other flower-visiting insects. The main constituents of nectar are sugars, which vary in both composition and concentration between plant species. We assessed the influence of sugar concentration, sugar solution viscosity and sugar solution composition on the imbibition and energy intake rate of bumblebees, Bombus impatiens Cresson (Hymenoptera: Apidae). To do this, we measured their rate of solution intake for 49 different sugar solution treatments, which varied in both sugar composition and concentration. In general, the imbibition rates of bumblebees were found to increase with increasing sugar concentration, probably due to their preference for high sugar concentrations, up to a concentration of 27% (w/w), at which point solutions reached a threshold viscosity of approximately 1.5-1.6 mPa.s. Above this threshold, the increasing viscosity of the solutions physically inhibited the imbibition rates of bees, and imbibition rate began to decrease as the concentration increased. Nevertheless, bumblebee energy intake rate increased with increasing concentration up to about 42-56%. Although we found that sugar solution composition had an impact on both imbibition and energy intake rate, its effect was not as straightforward as that of sugar concentration and viscosity. Copyright © 2013 Elsevier Ltd. All rights reserved.
Hashiguchi, N; Takeda, A; Yasuyama, Y; Chishaki, A; Tochihara, Y
2013-10-01
The purpose of this study was to investigate the effects of 6-h exposure to low relative humidity (RH) and low air pressure in a simulated air cabin environment on body fluid loss (BFL) and blood viscosity. Fourteen young healthy male subjects were exposed to four conditions, which combined RH (10% RH or 60% RH) and air pressure (NP: sea level or LP: equivalent to an altitude of 2000 m). Subjects remained seated on a chair in the chamber for 6 h. Their diet and water intake were restricted before and during the experiment. Insensible water loss (IWL) in LP10% condition was significantly greater than in NP60% condition; thus, combined 10%RH and LP conditions promoted a greater amount of IWL. The BFL under the LP condition was significantly greater than that under the NP condition. Blood viscosity significantly increased under LP conditions. Increases in red blood cell counts (RBCs) and BFL likely contributed to the increased blood viscosity. These findings suggest that hypobaric-induced hypoxia, similar to the conditions in the air cabin environment, may cause increased blood viscosity and that the combined low humidity and hypobaric hypoxia conditions increase IWL. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Viscosity of confined inhomogeneous nonequilibrium fluids.
Zhang, Junfang; Todd, B D; Travis, Karl P
2004-12-01
We use the nonlocal linear hydrodynamic constitutive model, proposed by Evans and Morriss [Statistical Mechanics of Nonequilibrium Liquids (Academic, London, 1990)], for computing an effective spatially dependent shear viscosity of inhomogeneous nonequilibrium fluids. The model is applied to a simple atomic fluid undergoing planar Poiseuille flow in a confined channel of several atomic diameters width. We compare the spatially dependent viscosity with a local generalization of Newton's law of viscosity and the Navier-Stokes viscosity, both of which are known to suffer extreme inaccuracies for highly inhomogeneous systems. The nonlocal constitutive model calculates effective position dependent viscosities that are free from the notorious singularities experienced by applying the commonly used local constitutive model. It is simple, general, and has widespread applicability in nanofluidics where experimental measurement of position dependent transport coefficients is currently inaccessible. In principle the method can be used to predict approximate flow profiles of any arbitrary inhomogeneous system. We demonstrate this by predicting the flow profile for a simple fluid undergoing planar Couette flow in a confined channel of several atomic diameters width.
Kang, Kyungho; Lim, Hyunpil; Yun, Kwi-Dug; Park, Sangwon; Jeong, Cheolwoong; Lee, Kwangmin
2015-07-01
Hydroxyapatite (HA) coating on biomaterials is crucial for bone growth. TiO2 naotubes having a larger specific area can also improve an osseointegration. In this study, anodized TiO2 nanotubes were coated with HA using sol-gel method with different viscosities of solution. Morphological characterization and crystal structures of the coated specimens were measured via field emission scanning electron microscope, transmission electron microscope, X-ray diffractometer, and fourier transforrm infrared spectroscopy. Nanosized hydroxyapatite particles were observed with sol viscosities at 1.95 cP and 0.94 cP inside the TiO2 nanotubes. When coated with the lower viscosity of solution, the TiO2 nanotubes were clearly observed. The crystallinity of HA increased as the temperature of heat treatment increased. The HA phase on the specimen was identified by PO4(3-) and OH-ion peaks in FT-IR spectra.
Viscosity and inertia in cosmic-ray transport - Effects of an average magnetic field
Williams, L. L.; Jokipii, J. R.
1991-01-01
A generalized transport equation is introduced which describes the transport and propagation of cosmic rays in a magnetized, collisionless medium. The equation is valid if the cosmic-ray distribution function is nearly isotropic in momentum, if the ratio of fluid speed to fluid-flow particle speed is small, and if the ratio of collision time to time for change in the macroscopic flow is small. Five independent cosmic-ray viscosity coefficients are found, and the ralationship of this viscosity to particle orbits in a magnetic field is presented.
Hrma, P.; Piepel, G.F.; Smith, D.E.; Redgate, P.E.; Schweiger, M.J.
1993-04-01
Viscosity and electrical conductivity of 79 simulated borosilicate glasses in the expected range of compositions to be produced in the Hanford Waste Vitrification Plant were measured within the temperature span from 950 to 1250[degree]C. The nine major oxide components were SiO[sub 2], B[sub 2]O[sub 3], Li[sub 2]O, Na[sub 2]O, CaO, MgO, Fe[sub 2]O[sub 3], Al[sub 2]O[sub 3], and ZrO[sub 2]. The test compositions were generated statistically. The data were fitted by Fulcher and Arrhenius equations with temperature coefficients being multilinear functions of the mass fractions of the oxide components. Mixture models were also developed for the natural logarithm of viscosity and that of electrical conductivity at 1150[degree]C. Least squares regression was used to obtain component coefficients for all the models.
Viscosity of colloidal suspensions
Cohen, E.G.D. [Rockefeller Univ., New York, NY (United States); Schepper, I.M. de [Delft Univ. of Technology (Netherlands)
1995-12-31
Simple expressions are given for the effective Newtonian viscosity as a function of concentration as well as for the effective visco-elastic response as a function of concentration and imposed frequency, of monodisperse neutral colloidal suspensions over the entire fluid range. The basic physical mechanisms underlying these formulae are discussed. The agreement with existing experiments is very good.
Burseg, Kerstin Martha Mensien; Camacho, Sara; Bult, Johannes Hendrikus Franciscus
2011-05-25
Oral stimulation with high-tastant concentrations that are alternared with low-tastant concentrations or water rinses (pulsatile stimulation) results in taste intensity ratings that are higher than continuous stimulation with the same average tastant concentration. This study tested the combined effects of taste pulsation rate and viscosity on pulsation-induced taste enhancement in apple juice. According to a tastant-kinetics hypothesis, less pulsation-induced taste enhancement is expected at enhanced pulsation rates in the high-viscous proximal stimulus compared to lower viscous stimuli. High-concentration sucrose apple juice pulses and low-concentration sucrose apple juice intervals were alternated at different pulsation periods (pulse + interval in seconds) every 2.5 s (period length = 5 s) or every 1.25 s (period length = 2.5 s). Pulsed stimuli were presented at two viscosity levels by the addition of pectin (0 and 10 g/L). Sweetness intensities of pulsed stimuli were compared to a continuous reference of the same net but nonalternating sucrose concentration. Sweetness ratings were higher for pulsatile stimuli than for continuous stimuli. In low-viscous stimuli, enhancement depended on the pulsation period and peaked at 5 s periods. In high-viscous stimuli, the same enhancement was observed for both pulsation periods. These results contradict a tastant-kinetics hypothesis of viscosity-induced taste suppression because impaired tastant kinetics by viscosity would predict the opposite: lower pulsation-induced taste enhancement for viscous stimuli, especially at higher pulsation rates. Instead, these observations favor an explanation based on perceptual texture-taste interactions, which predict the observed independence between viscosity and pulsation rate.
Yousefi, Fakhri; Karimi, Hajir; Mohammadiyan, Somayeh
2016-11-01
This paper applies the model including back-propagation network (BPN) and principal component analysis (PCA) to estimate the effective viscosity of carbon nanotubes suspension. The effective viscosities of multiwall carbon nanotubes suspension are examined as a function of the temperature, nanoparticle volume fraction, effective length of nanoparticle and the viscosity of base fluids using artificial neural network. The obtained results by BPN-PCA model have good agreement with the experimental data.
Power Law of Shear Viscosity in Einstein-Maxwell-Dilaton-Axion model
Ling, Yi; Zhou, Zhenhua
2016-01-01
We construct charged black hole solutions with hyperscaling violation in the infrared(IR) region in Einstein-Maxwell-Dilaton-Axion theory and investigate the temperature behavior of the ratio of holographic shear viscosity to the entropy density. When translational symmetry breaking is relevant in the IR, the power law of the ratio is testified numerically at low temperature $T$, namely, $\\eta/s\\sim T^\\kappa$, where the values of exponent $\\kappa$ coincide with the analytical results. We also find that the exponent $\\kappa$ is not affected by irrelevant current, but is reduced by the relevant current.
EFFECT OF INCREASED WHOLE-BLOOD VISCOSITY ON REGIONAL BLOOD FLOWS IN CHRONICALLY HYPOXEMIC LAMBS
DALINGHAUS, M; KNOESTER, H; GRATAMA, JWC; VANDERMEER, J; ZIJLSTRA, WG; KUIPERS, JRG
1994-01-01
In chronic hypoxemia blood flow and oxygen supply to vital organs are maintained, but to nonvital organs they are decreased. We measured organ blood flows (microspheres) and whole blood viscosity in 10 chronically hypoxemic lambs, with an atrial septal defect and pulmonary stenosis, and in 8 control
Mehta, R; Teckoe, J; Schoener, C; Workentine, S; Ferrizzi, D; Rajabi-Siahboomi, A
2016-12-01
Ethylcellulose is one of the most commonly used polymers to develop reservoir type extended release multiparticulate dosage forms. For multiparticulate extended release dosage forms, the drug release is typically governed by the properties of the barrier membrane coating. The ICH Pharmaceutical Development Guideline (ICH Q8) requires an understanding of the influence of critical material attributes and critical process parameters on the drug release of a pharmaceutical product. Using this understanding, it is possible to develop robust formulations with consistent drug release characteristics. Critical material attributes for ethylcellulose were evaluated, and polymer molecular weight variation (viscosity) was considered to be the most critical attribute that can impact drug release. To investigate the effect of viscosity variation within the manufacturer's specifications of ethylcellulose, extended release multiparticulate formulations of two model drugs, metoprolol tartrate and acetaminophen, were developed using ETHOCEL™ as the rate controlling polymer. Quality by Design (QbD) samples of ETHOCEL Std. 10, 20, and 100 Premium grades representing the low, medium, and high molecular weight (viscosity) material were organically coated onto drug layered multiparticulates to a 15% weight gain (WG). The drug release was found to be similar (f 2 > 50) for both metoprolol tartrate and acetaminophen multiparticulates at different coating weight gains of ethylcellulose, highlighting consistent and robust drug release performance. The use of ETHOCEL QbD samples also serves as a means to develop multiparticulate dosage formulations according to regulatory guidelines.
Monaco, Davide; Fatnassi, Meriem; Padalino, Barbara; Hammadi, Mohamed; Khorchani, Touhami; Lacalandra, Giovanni Michele
2016-04-01
Ejaculates from five clinically healthy dromedary camels (Camelus dromedarius) were used to evaluate the effects of different enzymatic treatments (Amylase, Papain, Spermfluid) on liquefaction and seminal parameters. After collection, ejaculates were divided into 5 aliquots: (1) kept undiluted (control); or diluted 1:1 with: (2) Tris-Citrate-Fructose (TCF), (3) TCF containing Amylase, (4) TCF containing Papain or (5) Spermfluid containing Bromelain. At 120 min after dilution, each aliquot was evaluated, at 20-min intervals, for viscosity, motility, viability and agglutination. Only the aliquots diluted with TCF containing Papain underwent complete liquefaction. Sperm motility decreased significantly during the observation times, except for the samples diluted with Spermfluid (P=0.005). Diluted samples showed different levels of agglutination, with the lowest being observed in the control and the highest in the Papain-treated samples. The viscosity of dromedary camel ejaculates could be effectively reduced by using the proteolytic enzyme Papain.
Shahsavar, Amin [Kermanshah University of Technology, Kermanshah (Iran, Islamic Republic of); Salimpour, Mohammad Reza; Saghafian, Mohsen [Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Shafii, M. B. [Sharif University of Technology, Tehran(Iran, Islamic Republic of)
2016-02-15
The present work examines experimentally the effect of magnetic field on the viscosity and thermal conductivity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe{sub 3}O{sub 4} nanoparticles and Gum arabic (GA) coated carbon nanotubes (CNTs). The hybrid nanofluid was prepared by using ultrasonic dispersion method. Magnetic field was created by a pair of spaced apart magnet plates. The effect of temperature on the time variation of thermal conductivity under applied magnetic field was also investigated. According to the results of this study, viscosity of the hybrid nanofluid increases with the strength of magnetic field, while it decreases with the increase of temperature. Additionally, it is found that the hybrid nanofluid behaves as a shear thinning fluid at low shear rates while it exhibits Newtonian behavior at high shear rates. Furthermore, results show that when an external magnetic field is applied to the studied magnetic nanofluids, the thermal conductivity experiences a peak.
Selim, Mohamed Y.E. [Mech. Eng. Dept., UAE University, Al-Ain, Abu Dhabi 17555 (United Arab Emirates)
2009-07-15
An experimental investigation has been carried out to test two approaches to reduce the viscosity of the Jojoba Methyl Ester (JME) diesel fuel. The first approach is the heating of the fuel to two temperatures of 50 and 70 C as compared to the base ambient temperature and to diesel fuel too. The second approach is adding one chemical which is considered by its own as alternative and renewable fuel which is Diethyl Ether (DEE). The viscosity has been reduced by both methods to close to diesel values. The performance of a diesel engine using those fuels has been tested in a variable compression research engine Ricardo E6 with the engine speed constant at 1200 rpm. The measured parameters included the exhaust gas temperature, the ignition delay period, the maximum pressure rise rate, maximum pressure, and indicated mean effective pressure and maximum heat release rate. The engine performance is presented and the effects of both approaches are scrutinized. (author)
Mukisa, Ivan M.; Muyanja, Charles M. B. K.; Byaruhanga, Yusuf B.; Schüller, Reidar B.; Langsrud, Thor; Narvhus, Judith A.
2012-03-01
Malted and un-malted sorghum ( Sorghum bicolor (L.) Moench) flour was gamma irradiated with a dose of 10 kGy and then re-irradiated with 25 kGy. The effects of irradiation on microbial decontamination, amylase activity, fermentability (using an amylolytic L. plantarum MNC 21 strain), starch granule structure and viscosity were determined. Standard methods were used during determinations. The 10 kGy dose had no effect on microbial load of un-malted flour but reduced that of malted flour by 3 log cycles. Re-irradiation resulted in complete decontamination. Irradiation of malt caused a significant ( pgelatinization. Production of high dry matter density porridge (200 g dry matter/L) with a viscosity of 3500 cP was achieved by irradiation of un-malted flout at 10 kGy. Gamma irradiation can be used to decontaminate flours and could be utilized to produce weaning porridge from sorghum.
彭康; 臧坤堂
2005-01-01
BACKGROUND: Wu long dan is the experienced formula summarized in the long-term clinical practice on the treatment ischemic cerebral vascular disorder and aims at "benefiting qi,strengthening spleen,tonifying kidney,activating blood circulation,promoting circulation of collaterals and resolving phlegm". It is indicated in the previous researches that such formula acts on improving microcirculation of cerebrum,regulating neural endocrinal system and being against cerebral ischemic injury. The increased blood viscosity and disturbance endothelin and nitric oxide(NO) secreted from vessels and nerve cells have participated in the pathological progression of multi-infarct dementia(MID) and affect mutually.OBJECTIVE: To probe into the effect of wu long dan on blood viscosity,NO and endothelin in MID model in rats by duplicating MID rat model.DESIGN: A randomized controlled and experimental study based on the experimental animals.SETTING: Department of traditional Chinese medicine in a military medical university of Chinese PLA.MATERIALS: The experiment was performed in Laboratory of Department of Traditional Chinese Medicine in First Military Medical University of Chinese PLA and Laboratory of Department of Neurological Internal Medicine in affiliated Zhujiang Hospital from January to August 2002. SD male rats of clean grade were employed,weighted(270 ± 30) g (Qualified No. 2000337). In the experiment,there were blank control,model group,wu long dan low dosage group and wu long dan high dosage group.METHODS: After internal carotid artery isolated,dried blood suspension of homologous rats was injected at the ratio of 1:200 to prepare MID rat model. Cone-plate stationary method was adopted for the determination of blood viscosity,radioimmunoassay was for the determination of endothelin and cadmium-reduction-colorimetric method was for NO determination. Water-alcohol sedimentation was for the preparation of wu long dan.MAIN OUTCOME MEASURES: Primary indexes: whole blood
Paquet-Mercier, Francois; Bellavance, Julien; Taghavi, Seyed Mohammad; Greener, Jesse
2016-01-01
A method combining video imaging in parallel microchannels with a semi-empirical mathematical model provides non-intrusive, high-throughput measurements of time-varying biofilm viscosity. The approach is demonstrated for early growth Pseudomonas sp. biofilms exposed to constant flow streams of nutrient solutions with different ionic strengths. The ability to measure viscosities at early growth stages, without inducing a shear-thickening response, enabled measurements that are among the lowest reported to date. In addition, good time resolution enabled the detection of a rapid thickening phase, which occurred at different times after the exponential growth phase finished, depending on the ionic strength. The technique opens the way for a combinatorial approach to beter understand the complex dynamical response of biofilm mechanical properties under well-controlled physical, chemical and biological growth conditions and time-limited perturbations.
Stefanie Bärwinkel
2016-08-01
Full Text Available Morphology formation during compounding, as well as injection molding of blends containing 60 wt % polycarbonate (PC and 40 wt % polybutadiene rubber-modified styrene-acrylonitrile copolymers (ABS, has been investigated by transmission electron microscopy (TEM. Profiles of the blend morphology have been recorded in injection-molded specimens and significant morphology gradients observed between their skin and core. A <10 µm thick surface layer with strongly dispersed and elongated nano-scale (streak-like styrene acrylonitrile (SAN phases and well-dispersed, isolated SAN-grafted polybutadiene rubber particles is followed by a 50–150 µm thick skin layer in which polymer morphology is characterized by lamellar SAN/ABS phases. Thickness of these lamellae increases with the distance from the specimen’s surface. In the core of the specimens the SAN-grafted polybutadiene rubber particles are exclusively present within the SAN phases, which exhibit a much coarser and less oriented, dispersed morphology compared to the skin. The effects of the viscosity of the SAN in the PC/ABS blends on phase morphologies and correlations with fracture mechanics in tensile and impact tests were investigated, including scanning electron microscopy (SEM assessment of the fracture surfaces. A model explaining the mechanisms of morphology formation during injection molding of PC/ABS blends is discussed.
Katz, J.I.
1980-01-01
Both HerX-1 and SS433 may contain accretion disks slaved to a precessing companion star. If so, it is possible to bound the effective viscosity in these disks. The results, in terms of the disk parameter alpha, are lower bounds of 0.01 for HerX-1 and of 0.1 for SS433.
Barletta, V. R.; Bevis, M.; Smith, B. E.; Wilson, T. J.; Willis, M. J.; Brown, A.; Bordoni, A.; Khan, S. A.; Smalley, R., Jr.; Kendrick, E. C.; Konfal, S. A.; Caccamise, D.; Aster, R.; Chaput, J. A.; Heeszel, D.; Wiens, D.; Lloyd, A. J.
2015-12-01
The Amundsen Embayment sector of West Antarctica is experiencing some of the fastest sustained bedrock uplift rates in the world. These motions, recorded by the Antarctic GPS Network (ANET), cannot be explained in terms of the earth's elastic response to contemporary ice loss, and the residues are far too rapid to be explained using traditional GIA models. We use 13 years of very high resolution DEM-derived ice mass change fields over the Amundsen sector to compute the elastic signal and remove it from the observed geodetic time series. We obtain a very large residual - up to 5 times larger than the computed elastic response. Low or very low mantle viscosities are expected in this area based on existing heat flow estimates, seismic velocity anomalies, thin crust, and active volcanism, all of which are associated with geologically recent rifting. We hypothesize that the rapid crustal displacement manifests a low viscosity short-time-scale response to post- Little Ice Age ice mass changes, including ice losses developed in the last decade or so. A plausible ice history for the last hundred years is made by using the actual measurements from 2002 to 2014, and 25% of the present day melting rate before 2002. We then simulate and fit the bedrock displacement - both vertical and horizontal - with a spherical compressible viscoelastic Earth model having a low viscosity shallow upper mantle. We show that we can constrain the shallow upper mantle viscosity very well and also explain most of the signal (amplitude and direction) by using 2 x10^18 Pa s. However we are not able to precisely constrain the thickness of the lithosphere (the preferred thickness is more than 50 km, quite thick for that region) or ice history. By using our preferred set up (earth model + ice history) we compute the GIA gravitational signature and convert it in equivalent superficial water density (see figure) that can be directly used to correct the mass changes observed by GRACE.For the Amundsen
Wang, Jeen-Hwa
2017-08-01
This study is focused on multistable slip of earthquakes based on a one-degree-of-freedom spring-slider model in the presence of thermal-pressurized slip-weakening friction and viscosity by using the normalized equation of motion of the model. The major model parameters are the normalized characteristic displacement, Uc, of the friction law and the normalized viscosity coefficient, η, between the slider and background plate. Analytic results at small slip suggest that there is a solution regime for η and γ ( = 1/Uc) to make the slider slip steadily. Numerical simulations exhibit that the time variation in normalized velocity, V/Vmax (Vmax is the maximum velocity), obviously depends on Uc and η. The effect on the amplitude is stronger due to η than due to Uc. In the phase portrait of V/Vmax versus the normalized displacement, U/Umax (Umax is the maximum displacement), there are two fixed points. The one at large V/Vmax and large U/Umax is not an attractor, while that at small V/Vmax and small U/Umax can be an attractor for some values of η and Uc. When Uc1, the related Fourier spectra show only one peak, thus suggesting linear behavior of the system.
Joshi, Vimal Kumar; Ram, Paras; Sharma, Ravi Kumar; Tripathi, Dharmendra
2017-06-01
The aim of this paper is to study the Bodewadt flow of a magnetic nanofluid in the presence of geothermal viscosity. The effects of porosity on an unsteady boundary layer flow of water-based magnetic nanofluids over a uniformly heated stationary disk are discussed numerically. Fluid viscosity is considered as a function of both depth and temperature. The Runge-Kutta fourth-order method along with the shooting technique is employed for solving a set of coupled ordinary differential equations. The computed results reveal that heat transfer is appreciably enhanced with more porosity and rotation of the fluid. Also, varying the fluids Prandtl number from 20 to 80, the rate of heat transfer increases by 93.35% and faster cooling of the system occurs.
Ghurri, Ainul; Kim, Jae Duk; Kim, Hyung Gon; Jung, Jae Youn; Song, Kyu Keun [Chonbuk National Univ., Deokjin Gu (Korea, Republic of)
2012-09-15
An experimental study was conducted to examine the effect of injection pressure and fuel type on the spray tip penetration length and the angle of spray injected into atmospheric chamber. The objective of the present study is to formulate empirical correlations of the spray tip penetration and the spray angle for non evaporative condition. The experiment was performed by a common rail type high pressure injector for the diesel engine at the injection pressure 40{approx}100 MPa and four different fuels (D100, BD25, BD45, and BD65). The results showed that the biodiesel content increased the spray tip penetration and decreased the spray angle. The correlation of spray tip penetration is expressed for each region before and after spray break up time in terms of injection pressure, fuel viscosity and time after start of injection. The correlation is also obtained for spray angle equation terms of injection pressure and fuel viscosity.
Motsa SS
2010-01-01
Full Text Available The problem of magnetohydrodynamic flow and heat transfer of a viscous, incompressible, and electrically conducting fluid past a semi-infinite unsteady stretching sheet is analyzed numerically. The problem was studied under the effects of Hall currents, variable viscosity, and variable thermal diffusivity. Using a similarity transformation, the governing fundamental equations are approximated by a system of nonlinear ordinary differential equations. The resultant system of ordinary differential equations is then solved numerically by the successive linearization method together with the Chebyshev pseudospectral method. Details of the velocity and temperature fields as well as the local skin friction and the local Nusselt number for various values of the parameters of the problem are presented. It is noted that the axial velocity decreases with increasing the values of the unsteadiness parameter, variable viscosity parameter, or the Hartmann number, while the transverse velocity increases as the Hartmann number increases. Due to increases in thermal diffusivity parameter, temperature is found to increase.
MODIFICATION OF EYRING'S MODEL AND STUDY ON VISCOSITY OF LIQUID MIXTURES%Eyring模型的修正及液体混合物粘度的研究
叶长志; 虞大红; 刘国杰
1999-01-01
The molecular model of viscous flow of liquid proposed by Eyring is modified from two respects, namely, the activated energy of viscous flow and the frequency with which activated molecule falls into the hole. A viscosity equation with a single adjustable parameter is obtained, which can be satisfactorily used to correlate and predict the viscosity of various liquid mixtures except aqueous systems. The calculated results show that the agreement with experimental values prevails over Grunberg-Nissan and Wei-Rowley equations etc.
Kruger, Albert A.; Piepel, Gregory F.; Landmesser, S. M.; Pegg, I. L.; Heredia-Langner, Alejandro; Cooley, Scott K.; Gan, H.; Kot, W. K.
2013-11-13
This report is the last in a series of currently scheduled reports that presents the results from the High Level Waste (HLW) glass formulation development and testing work performed at the Vitreous State Laboratory (VSL) of the Catholic University of America (CUA) and the development of IHLW property-composition models performed jointly by Pacific Northwest National Laboratory (PNNL) and VSL for the River Protection Project-Waste Treatment and Immobilization Plant (RPP-WTP). Specifically, this report presents results of glass testing at VSL and model development at PNNL for Product Consistency Test (PCT), one-percent crystal fraction temperature (T1%), electrical conductivity (EC), and viscosity of HLW glasses. The models presented in this report may be augmented and additional validation work performed during any future immobilized HLW (IHLW) model development work. Completion of the test objectives is addressed.
Gunter, Amy-Lee; Ng, Hoi Dick
2012-11-01
This experimental study aims to investigate the phenomenon of a bouncing soap droplet on a horizontal soap film, and how this behavior is affected by variations in the glycerol content of the solution for both the droplet and film. Direct visualization of the bouncing dynamics using high-speed photography allows determination of droplet size and rebound height as the viscosity is varied. In addition, the upper and lower limits of the mixture composition at which the viscosity of the fluid prevents the droplet from bouncing are determined. A thorough examination of this fluid trampoline was recently conducted by Gilet and Bush, the focus of which was to compare the effect of vibration in the soap film [T. Gilet and J.W.M. Bush, J. Fluid Mech. 625: 167-203, 2009]. A small amount of attention was given to the effect of viscosity changes in the droplet and film, and this work aims to expand on those findings. This work is supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).
Abbass Ghanbari-Niaki
2013-09-01
Full Text Available The present study examined the effects of progressive exercise (pyramidal short-term program on plasma fibrinogen, lipid profile and blood viscosity in untrained young men. Changes and imbalances in homeostasis lead to cause of heart attacks. There is conflicting information about the effect of exercise on these factors. 19 young healthy untrained men were randomly assigned to the exercise group (n = 10 and controls (n = 9 groups. Exercise training group with increasing severity of heart maximum 25 to 100 percent began to run the practice (pyramid in 42-minute sessions, 3 times a week, for 4 weeks. There was no significant difference between the parameters of body composition, control, and training groups. Levels of total cholesterol and low density lipoprotein density and viscosity of the blood significantly decreased in the training group compared with the control group (p value, respectively is 0.001, 0.001 and 0.035. The changes in the concentration of fibrinogen, high-density lipoprotein and triglycerides in both groups are not significant in both groups (p value, respectively is 0.645, 0.993 and 0.421. The present results show that it is possible that progressive training (pyramidal short-term program changed the levels of cardiovascular risk factors by reducing blood viscosity.
Power law of shear viscosity in Einstein-Maxwell-Dilaton-Axion model
Ling, Yi; Xian, Zhuoyu; Zhou, Zhenhua
2017-02-01
We construct charged black hole solutions with hyperscaling violation in the infrared (IR) region in Einstein-Maxwell-Dilaton-Axion theory and investigate the temperature behavior of the ratio of holographic shear viscosity to the entropy density. When translational symmetry breaking is relevant in the IR, the power law of the ratio is verified numerically at low temperature T, namely, η/s ∼ T κ , where the values of exponent κ coincide with the analytical results. We also find that the exponent κ is not affected by irrelevant current, but is reduced by the relevant current. Supported by National Natural Science Foundation of China (11275208, 11575195), Opening Project of Shanghai Key Laboratory of High Temperature Superconductors (14DZ2260700) and Jiangxi Young Scientists (JingGang Star) Program and 555 Talent Project of Jiangxi Province
2009-06-01
Full Text Available Thermoplastics having various short and long-chain branches, characterized by the melt index measured at the processing temperature – according to their average molecular mass – can be processed using universal principles, independently of their chemical composition. The average molecular mass is the result of a molecular mass distribution, being the fingerprint of the chemical synthetic technology. The actual shape of the shear viscosity function aiming at the quantitative characterization of viscous flow, containing material-dependent parameters, depends on the ratio of high and low molecular mass fractions, the width of the molecular mass distribution function and on the number of short and long chain branches. This publication deals with the critical analysis of the mathematical methods of transforming these two curves of basic importance into each other.
Effects of substrate loading on enzymatic hydrolysis and viscosity of pretreated barley straw
Rosgaard, L.; Andric, Pavle; Dam-Johansen, Kim
2007-01-01
for the reaction with a substrate loading of 5% w/w DM after 72 h. The reactions subjected to gradual loading of substrate or substrate plus enzymes to increase the substrate levels from 5 to 15% w/w DM, consistently provided lower concentrations of glucose after 72 h of reaction; however, the initial rates...... of conversion varied in the different reactions. Rapid cellulose degradation was accompanied by rapid decreases in viscosity before addition of extra substrate, but when extra substrate or substrate plus enzymes were added, the viscosities of the slurries increased and the hydrolytic efficiencies decreased......In this study, the applicability of a "fed-batch" strategy, that is, sequential loading of substrate or substrate plus enzymes during enzymatic hydrolysis was evaluated for hydrolysis of steam-pretreated barley straw. The specific aims were to achieve hydrolysis of high substrate levels, low...
Effect of Fe Content on Olivine Viscosity at the P-T Conditions of Terrestrial-Planet Interiors
Raterron, P.; Holyoke, C. W., III; Tokle, L.; Hilairet, N.; Merkel, S.; Hirth, G.; Weidner, D. J.
2016-12-01
The top parts of the mantle of terrestrial planets are olivine-rich, with Fe/(Mg+Fe) ratio lower than 2% for Mercury, up to 25-30% for Mars, and intermediate compositions for the Earth, the Moon and Venus. Results of experiments at low pressure (Zhao et al., 2009, EPSL, 287, 229-240) indicate that increasing Fe content dramatically decreases olivine viscosity. Thus, the Martian upper mantle may be 10 times less viscous than the Earth's at the same conditions. However, there is no data available on the effect of iron on olivine plasticity at pressures relevant to planetary interiors. We deformed polycrystalline olivine specimens with various Fe contents ranging from 0% (pure forsterite) to 100% (pure fayalite), at temperatures (T) in excess of 1000°C and pressures (P) in the range of 2 - 6 GPa, in the Deformation-DIA apparatus (D-DIA) coupled with X-ray synchrotron radiation. Pressure, differential stress and strain rate were measured in situ by X-ray diffraction and radiography. Stacked cylindrical specimens with different iron contents were deformed in series to compare their viscosities at identical T, P and differential stress. We observed that increasing pressure dramatically decreases the viscosity contrast between Fe-poor olivine and Fe-rich olivine, while increasing differential stress has the opposite effect. Hence, the range of viscosities expected in planetary mantles - in the low-P and high-stress regime of the uppermost mantle and in the high-P and low-stress regime of the deep mantle - may be radically different, depending on their iron contents. We will present these new data which may have significant implications for the convection mode and thermal history of terrestrial-planet mantles.
Akbar, Noreen Sher; Tripathi, Dharmendra; Khan, Zafar Hayat; Bég, O. Anwar
2016-09-01
In this paper, a mathematical study is conducted of steady incompressible flow of a temperature-dependent viscous nanofluid from a vertical stretching sheet under applied external magnetic field and gravitational body force effects. The Reynolds exponential viscosity model is deployed. Electrically-conducting nanofluids are considered which comprise a suspension of uniform dimension nanoparticles suspended in viscous base fluid. The nanofluid sheet is extended with a linear velocity in the axial direction. The Buonjiornio model is utilized which features Brownian motion and thermophoresis effects. The partial differential equations for mass, momentum, energy and species (nano-particle concentration) are formulated with magnetic body force term. Viscous and Joule dissipation effects are neglected. The emerging nonlinear, coupled, boundary value problem is solved numerically using the Runge-Kutta fourth order method along with a shooting technique. Graphical solutions for velocity, temperature, concentration field, skin friction and Nusselt number are presented. Furthermore stream function plots are also included. Validation with Nakamura's finite difference algorithm is included. Increasing nanofluid viscosity is observed to enhance temperatures and concentrations but to reduce velocity magnitudes. Nusselt number is enhanced with both thermal and species Grashof numbers whereas it is reduced with increasing thermophoresis parameter and Schmidt number. The model is applicable in nano-material manufacturing processes involving extruding sheets.
[Effect of smoking on blood viscosity and arterial rigidity in normal and hypertensive subjects].
Levenson, J; Simon, A C; Cambien, F; Beretti, C
1987-06-01
The purpose of the study was to assess whether cigarettes smoking could induce blood hyperviscosity and arterial rigidity in 30 normotensive and 70 hypertensive men aged from 24 to 65 years. Of those, 20 normotensive and 20 hypertensive were cigarettes smokers, while the remaining subjects were non smokers. Age and weight were similar in the 4 groups of subjects. A couette viscometer with coaxial cylinders allowed the measurements of blood viscosity over a wide range of shear rates (0.033 to 241 sec-1) mimicking the flow condition of the circulation, and two strain gauge transducers permitted the measurements of the brachial to radial pulse wave velocity as an index of arterial wall distensibility. In normotensive subjects cigarettes smoking increased pulse wave velocity from 7.1 + 1 to 9.2 + 0.6 m/sec. (P less than 0.05) as well as blood viscosity, which increased both at higher shear rates (+10% from 52 to 241 sec-1, P less than 0.05) and lower shear rates (+20% from 11.2 to 0.2 sec-1, P less than 0.02). In hypertensives, cigarettes smoking increased pulse wave velocity (9.8 + 0.3 to 11.3 + 0.4; P less than 0.05) and blood viscosity (4% at higher shear rate P less than 0.05 and 10% at lower shear rates P less than 0.02). Although hypertensive patients had increased pulse wave velocity and blood viscosity compared to normotensive controls, these variables were not significantly different when hypertensive non smokers were compared to normotensive. The present study demonstrated that cigarettes smoking produced in normotensive and hypertensive men significant rheological disturbances of flow and wall arteries.2
Gotaas, Cecilie; Havelka, Pavel; Jakobsen, Hugo A.; Svendsen, Hallvard F.; Hase, Matthias; Roth, Norbert; Weigand, Bernhard
2007-10-01
The influence of viscosity on droplet-droplet collision behavior at ambient conditions was studied experimentally and numerically. N-decane, monoethyleneglycol (MEG), diethyleneglycol (DEG), and triethyleneglycol were used as liquid phase providing viscosities in the range from 0.9to48mPas. Collision Weber numbers ranged approximately from 10 to 420. A direct numerical simulation code, based on the volume-of-fluid concept, was used for the simulations. Experimentally, observations of two droplet streams using a modified stroboscopic technique (aliasing method) were used to investigate the whole range of impact parameters during one experimental run. The experimental method has previously been verified for the water/air system [C. Gotaas et al., Phys. Fluids 19, 102105 (2007)]. In the present work, it was tested and validated for the n-decane/air system. Measured data agree well with those published in the literature. Well-defined regions of stretching separation and coalescence were identified, while reflexive separation regions were not found by using a single sinusoidal disturbance. However, the onset of reflexive separation was identified for MEG and DEG using an amplitude modulation technique. The results show that the criteria for onset of reflexive separation for viscous fluids provided by Y. I. Jiang et al. [J. Fluid Mech. 234, 177 (1992)] are not valid. This is consistent with the results given by K. D. Willis and M. Orme [Exp. Fluids 34, 28 (2003)]. A new empirical correlation for the onset of reflexive separation for high viscosity fluids is presented. The borders between coalescing and stretching separation were shifted toward higher Weber numbers with increasing viscosity. The lack of occurrence of reflexive separation for the single sinusoidal disturbance (small droplets), as well as the stretching separation boundary shift, can be explained by dissipation of collision kinetic energy in viscous flows inside the merged droplet after collision. Results
Can bulk viscosity drive inflation
Pacher, T.; Stein-Schabes, J.A.; Turner, M.S.
1987-09-15
Contrary to other claims, we argue that bulk viscosity associated with the interactions of non- relativistic particles with relativistic particles around the time of the grand unified theory (GUT) phase transition cannot lead to inflation. Simply put, the key ingredient for inflation, negative pressure, cannot arise due to the bulk-viscosity effects of a weakly interacting mixture of relativistic and nonrelativistic particles.
Petrov, Anton S.; Douglas, Scott S.; Harvey, Stephen C.
2013-03-01
In this work, we report on simulations of double-stranded DNA (dsDNA) ejection from bacteriophage ϕ29 into a bacterial cell. The ejection was studied with a coarse-grained model, in which viral dsDNA was represented by beads on a torsion-less string. The bacteriophage’s capsid and the bacterial cell were defined by sets of spherical constraints. To account for the effects of the viscous medium inside the bacterial cell, the simulations were carried out using a Langevin dynamics protocol. Our simplest simulations (involving constant viscosity and no external biasing forces) produced results compatible with the push-pull model of DNA ejection, with an ejection rate significantly higher in the first part of ejection than in the latter parts. Additionally, we performed more complicated simulations, in which we included additional factors such as external forces, osmotic pressure, condensing agents and ejection-dependent viscosity. The effects of these factors (independently and in combination) on the thermodynamics and kinetics of DNA ejection were studied. We found that, in general, the dependence of ejection forces and ejection rates on the amount of DNA ejected becomes more complex if the ejection is modeled with a broader, more realistic set of parameters and influences (such as variation in the solvent’s viscosity and the application of an external force). However, certain combinations of factors and numerical parameters led to the opposition of some ejection-driving and ejection-inhibiting influences, ultimately causing an apparent simplification of the ejection profiles.
Pourhassan, Behnam [Damghan University, School of Physics, Damghan (Iran, Islamic Republic of); Faizal, Mir [University of British Columbia-Okanagan, Irving K. Barber School of Arts and Sciences, Kelowna, BC (Canada); University of Lethbridge, Department of Physics and Astronomy, Lethbridge, AB (Canada)
2017-02-15
In this paper, we analyze the effects of thermal fluctuations on a STU black hole. We observe that these thermal fluctuations can affect the stability of a STU black hole. We will also analyze the effects of these thermal fluctuations on the thermodynamics of a STU black hole. Furthermore, in the Jacobson formalism such a modification will produce a deformation of the geometry of the STU black hole. Hence, we use the AdS/CFT correspondence to analyze the effect of such a deformation on the dual quark-gluon plasma. So, we explicitly analyze the effect of thermal fluctuations on the shear viscosity to entropy ratio in the quark-gluon plasma, and we analyze the effects of thermal fluctuations on this ratio. (orig.)
Bi, Xiufang; Hemar, Yacine; Balaban, Murat O; Liao, Xiaojun
2015-11-01
The effect of ultrasound treatment on particle size, color, viscosity, polyphenol oxidase (PPO) activity and microstructure in diluted avocado puree was investigated. The treatments were carried out at 20 kHz (375 W/cm(2)) for 0-10 min. The surface mean diameter (D[3,2]) was reduced to 13.44 μm from an original value of 52.31 μm by ultrasound after 1 min. A higher L(∗) value, ΔE value and lower a(∗) value was observed in ultrasound treated samples. The avocado puree dilution followed pseudoplastic flow behavior, and the viscosity of diluted avocado puree (at 100 s(-1)) after ultrasound treatment for 1 min was 6.0 and 74.4 times higher than the control samples for dilution levels of 1:2 and 1:9, respectively. PPO activity greatly increased under all treatment conditions. A maximum increase of 25.1%, 36.9% and 187.8% in PPO activity was found in samples with dilution ratios of 1:2, 1:5 and 1:9, respectively. The increase in viscosity and measured PPO activity might be related to the decrease in particle size. The microscopy images further confirmed that ultrasound treatment induced disruption of avocado puree structure.
SanSoucie, M. P.; Rogers, J. R.; Kumar, V.; Rodriguez, J.; Xiao, X.; Matson, D. M.
2016-07-01
The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has recently added an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled in the range from approximately 10^{-28} {to} 10^{-9} bar, while in a vacuum atmosphere. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, has a PID-based current loop and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects on surface tension and viscosity by oxygen partial pressure in the surrounding environment and the melt dissolved oxygen content will be evaluated, and the results will be presented. The surface tension and viscosity will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension and viscosity will be measured using the oscillating droplet method.
A.M. Rashad
2014-04-01
Full Text Available This work is focused on the study of unsteady magnetohydrodynamics boundary-layer flow and heat transfer for a viscous laminar incompressible electrically conducting and rotating fluid due to a stretching surface embedded in a saturated porous medium with a temperature-dependent viscosity in the presence of a magnetic field and thermal radiation effects. The fluid viscosity is assumed to vary as an inverse linear function of temperature. The Rosseland diffusion approximation is used to describe the radiative heat flux in the energy equation. With appropriate transformations, the unsteady MHD boundary layer equations are reduced to local nonsimilarity equations. Numerical solutions of these equations are obtained by using the Runge–Kutta integration scheme as well as the local nonsimilarity method with second order truncation. Comparisons with previously published work have been conducted and the results are found to be in excellent agreement. A parametric study of the physical parameters is conducted and a representative set of numerical results for the velocity in primary and secondary flows as well as the local skin-friction coefficients and the local Nusselt number are illustrated graphically to show interesting features of Darcy number, viscosity-variation, magnetic field, rotation of the fluid, and conduction radiation parameters.
Figueiredo Reis, André; Giannini, Marcelo; Ambrosano, Gláucia Maria Bovi; Chan, Daniel C N
2003-01-01
The aim of this study was to test the hypothesis that the effects of filling technique, cavity configuration and use of a low-viscosity composite liner influence resin bond strength to the dentin of class II cavities gingival floor; and analyze the failure modes of fractured specimens. Standardized class II cavities were prepared in the proximal surfaces of freshly extracted third molars, which were randomly assigned to 10 experimental groups. All prepared surfaces were acid-etched, bonded with Single Bond adhesive system and restored with TPH composite, according to each technique: G1 and G2-horizontal layering, G3 and G4-faciolingual layering, G5 and G6-oblique layering, G7 and G8-bulk filling, G9 and G10-control (flat dentin surfaces). Groups were tested, with or without a low-viscosity composite liner (Tetric Flow Chroma). After storage in water for 24h, teeth were vertically serially sectioned to yield a series of 0.8mm thick slabs. Each slab was trimmed into an hourglass shape of approximately 0.8mm(2) area at the gingival resin-dentin interface. Specimens were tested in tension at 0.5mm/min until failure. Fractured specimens were analyzed in an SEM to determine the failure modes. No significant difference was found between groups restored with and without a low-viscosity composite liner (p>0.05). Among filling techniques, the bulk filling groups presented the lowest bond strength values (pcomposite liner. Bond strengths were not improved when a low-viscosity composite liner was applied, but it remarkably influenced the failure modes. Incremental techniques improved bond strength.
Numerical solutions of Williamson fluid with pressure dependent viscosity
Zehra, Iffat; Yousaf, Malik Muhammad; Nadeem, Sohail
In the present paper, we have examined the flow of Williamson fluid in an inclined channel with pressure dependent viscosity. The governing equations of motion for Williamson fluid model under the effects of pressure dependent viscosity and pressure dependent porosity are modeled and then solved numerically by the shooting method with Runge Kutta Fehlberg for two types of geometries i.e., (i) Poiseuille flow and (ii) Couette flow. Four different cases for pressure dependent viscosity and pressure dependent porosity are assumed and the physical features of pertinent parameters are discussed through graphs.
Numerical solutions of Williamson fluid with pressure dependent viscosity
Iffat Zehra
2015-01-01
Full Text Available In the present paper, we have examined the flow of Williamson fluid in an inclined channel with pressure dependent viscosity. The governing equations of motion for Williamson fluid model under the effects of pressure dependent viscosity and pressure dependent porosity are modeled and then solved numerically by the shooting method with Runge Kutta Fehlberg for two types of geometries i.e., (i Poiseuille flow and (ii Couette flow. Four different cases for pressure dependent viscosity and pressure dependent porosity are assumed and the physical features of pertinent parameters are discussed through graphs.
R. K. Tiwari; Sonia Sharma
2011-01-01
We study the non existence of shear in locally rotationally symmetric Bianchi type-Ⅲ string cosmological models with bulk viscosity and variable cosmological term Λ. Exact solutions of the field equations are obtained by assuming the conditions: the bulk viscosity is proportional to the expansion scalar, ε ∝ θ, expansion scalar is proportional to shear scalar, θ ∝ σ, and Λ is proportional to the Hubble parameter. The coefficient of bulk viscosity is assumed to be a power function of mass density. The corresponding physical interpretations of the cosmological solutions are also discussed.%@@ We study the non existence of shear in locally rotationally symmetric Bianchi type-M string cosmological models with bulk viscosity and variable cosmological term Λ.Exact solutions of the field equations are obtained by assuming the conditions: the bulk viscosity is proportional to the expansion scalar, ξ∝θ, expansion scalar is proportional to shear scalar, θ∝σ, and A is proportional to the Hubble parameter.The coefficient of bulk viscosity is assumed to be a power function of mass density.The corresponding physical interpretations of the cosmological solutions are also discussed.
Jantzen, C. M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Edwards, T. B. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2016-08-30
Radioactive high-level waste (HLW) at the Savannah River Site (SRS) has successfully been vitrified into borosilicate glass in the Defense Waste Processing Facility (DWPF) since 1996. Vitrification requires stringent product/process (P/P) constraints since the glass cannot be reworked once it is poured into ten foot tall by two foot diameter canisters. A unique “feed forward” statistical process control (SPC) was developed for this control rather than statistical quality control (SQC). In SPC, the feed composition to the DWPF melter is controlled prior to vitrification. In SQC, the glass product would be sampled after it is vitrified. Individual glass property-composition models form the basis for the “feed forward” SPC. The models transform constraints on the melt and glass properties into constraints on the feed composition going to the melter in order to guarantee, at the 95% confidence level, that the feed will be processable and that the durability of the resulting waste form will be acceptable to a geologic repository. The DWPF SPC system is known as the Product Composition Control System (PCCS). The DWPF will soon be receiving wastes from the Salt Waste Processing Facility (SWPF) containing increased concentrations of TiO_{2}, Na_{2}O, and Cs_{2}O . The SWPF is being built to pretreat the high-curie fraction of the salt waste to be removed from the HLW tanks in the F- and H-Area Tank Farms at the SRS. In order to process TiO_{2} concentrations >2.0 wt% in the DWPF, new viscosity data were developed over the range of 1.90 to 6.09 wt% TiO_{2} and evaluated against the 2005 viscosity model. An alternate viscosity model is also derived for potential future use, should the DWPF ever need to process other titanate-containing ion exchange materials. The ultimate limit on the amount of TiO_{2} that can be accommodated from SWPF will be determined by the three PCCS models, the waste composition of a given sludge
SU(3) Polyakov linear-sigma model: bulk and shear viscosity of QCD matter in finite magnetic field
Tawfik, Abdel Nasser; Hussein, T M
2016-01-01
Due to off-center relativistic motion of the charged spectators and the local momentum-imbalance of the participants, a short-lived huge magnetic field is likely generated, especially in relativistic heavy-ion collisions. In determining the temperature dependence of bulk and shear viscosities of the QCD matter in vanishing and finite magnetic field, we utilize mean field approximation to the SU($3$) Polyakov linear-sigma model (PLSM). We compare between the results from two different approaches; Green-Kubo correlation and Boltzmann master equation with Chapman-Enskog expansion. We find that both approaches have almost identical results, especially in the hadron phase. In the temperature dependence of bulk and shear viscosities relative to thermal entropy at the critical temperature, there is a rapid decrease in the chiral phase-transition and in the critical temperature with increasing magnetic field. As the magnetic field strength increases, a peak appears at the critical temperature ($T_c$). This can be und...
Gao, Min
2014-09-01
In this paper, we develop an efficient numerical method for the two phase moving contact line problem with variable density, viscosity, and slip length. The physical model is based on a phase field approach, which consists of a coupled system of the Cahn-Hilliard and Navier-Stokes equations with the generalized Navier boundary condition [1,2,5]. To overcome the difficulties due to large density and viscosity ratio, the Navier-Stokes equations are solved by a splitting method based on a pressure Poisson equation [11], while the Cahn-Hilliard equation is solved by a convex splitting method. We show that the method is stable under certain conditions. The linearized schemes are easy to implement and introduce only mild CFL time constraint. Numerical tests are carried out to verify the accuracy, stability and efficiency of the schemes. The method allows us to simulate the interface problems with extremely small interface thickness. Three dimensional simulations are included to validate the efficiency of the method. © 2014 Elsevier Inc.
Meng, Xuhui; Guo, Zhaoli
2015-10-01
A lattice Boltzmann model with a multiple-relaxation-time (MRT) collision operator is proposed for incompressible miscible flow with a large viscosity ratio as well as a high Péclet number in this paper. The equilibria in the present model are motivated by the lattice kinetic scheme previously developed by Inamuro et al. [Philos. Trans. R. Soc. London, Ser. A 360, 477 (2002), 10.1098/rsta.2001.0942]. The fluid viscosity and diffusion coefficient depend on both the corresponding relaxation times and additional adjustable parameters in this model. As a result, the corresponding relaxation times can be adjusted in proper ranges to enhance the performance of the model. Numerical validations of the Poiseuille flow and a diffusion-reaction problem demonstrate that the proposed model has second-order accuracy in space. Thereafter, the model is used to simulate flow through a porous medium, and the results show that the proposed model has the advantage to obtain a viscosity-independent permeability, which makes it a robust method for simulating flow in porous media. Finally, a set of simulations are conducted on the viscous miscible displacement between two parallel plates. The results reveal that the present model can be used to simulate, to a high level of accuracy, flows with large viscosity ratios and/or high Péclet numbers. Moreover, the present model is shown to provide superior stability in the limit of high kinematic viscosity. In summary, the numerical results indicate that the present lattice Boltzmann model is an ideal numerical tool for simulating flow with a large viscosity ratio and/or a high Péclet number.
Effect of viscosity and temperature on the microstructure of BBT thin films
Costa Gustavo Carneiro da
2003-01-01
Full Text Available Thin films of BBT were deposited on silicate and Pt/Ti /SiO2 (111 substrates by spin- coating from the polymeric precursor method (Pechini process. The obtained films were characterized by optical microscopy, X-ray diffraction and atomic force microscopy. The influence of viscosity on the morphology of BBT thin films as well as the influence of temperature on crystallization, morphology and properties of BBTare discussed. Surface roughness and crystallization of these films are strongly dependent on the annealing conditions.
Evaluation of Eddy Viscosity Models in Predicting Free- Stream Turbulence Penetration
M. Kahrom
2013-01-01
Full Text Available Turbulence schemes have long been developed and examined for their accuracy and stability in a variety of environments. While many industrial flows are highly turbulent, models have rarely been tested to explore whether their accuracy withstands such augmented free-stream turbulence intensity or declines to an erroneous solution. In the present study, the turbulence intensity of an air flow stream, moving parallel to a flat plate is augmented by the means of locating a grid screen at a point at which Rex=2.5×105 and the effect on the flow and the near-wall boundary is studied. At this cross section, the turbulence intensity is augmented from 0.4% to 6.6% to flow downstream. Wind tunnel measurements provide reference bases to validate the numerical results for velocity fluctuations in the main stream and at the near-wall. Numerically, four of the most popular turbulence models are examined, namely the oneequation Spalart-Almaras, the two equation Standard k , the two equation Shear Stress Transport and the anisotropy multi equation Reynolds Stress Models (RSM. The resulting solutions for the domain are compared to experimental measurements and then the results are discussed. The conclusion is made that, despite the accuracy that these turbulence models are believed to have, even for some difficult flow field, they fail to handle high intensity turbulence flows. Turbulence models provide a better approach in experiments when the turbulence intensity is at about 2% and/or when the Reynolds number is high.
Shahsavar, A.; Saghafian, M.; Salimpour, M. R.; Shafii, M. B.
2016-10-01
The aim of this paper is to investigate the thermal conductivity and viscosity of a hybrid nanofluid containing tetramethylammonium hydroxide (TMAH) coated Fe3O4 nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs), experimentally. The magnetic nanoparticles and CNTs are physically attached as the result of interaction between the TMAH and GA molecules. The morphology and structure of the samples are characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM). The experiments are carried out in the magnetic nanoparticles volume concentration range of 0.1-0.9 %, CNT volume concentration range of 0.05-1.35 % and the temperature range of 25-55 °C. The viscosity of the hybrid nanofluid increases with the increase of volume concentration, while it decreases with the increase of temperature. Besides, results show that hybrid nanofluid behaves as a shear thinning fluid. Furthermore, it is observed that the thermal conductivity of the hybrid nanofluid enhances with temperature and volume concentration.
The effect of bolus viscosity on swallowing function in neurogenic dysphagia.
Clavé, P; de Kraa, M; Arreola, V; Girvent, M; Farré, R; Palomera, E; Serra-Prat, M
2006-11-01
To assess the pathophysiology and treatment of neurogenic dysphagia. 46 patients with brain damage, 46 with neurodegenerative diseases and eight healthy volunteers were studied by videofluoroscopy while swallowing 3-20 mL liquid (20.4 mPa s), nectar (274.4 mPa s) and pudding (3931.2 mPa s) boluses. Volunteers presented a safe and efficacious swallow, short swallow response ( or =0.33 mJ). Brain damage patients presented: (i) 21.6% aspiration of liquids, reduced by nectar (10.5%) and pudding (5.3%) viscosity (P or =806 ms) with a delay in laryngeal closure (> or =245 ms), and weak bolus propulsion forces (neurogenic dysphagia presented high prevalence of videofluoroscopic signs of impaired safety and efficacy of swallow, and were at high risk of respiratory and nutritional complications. Impaired safety is associated with slow oropharyngeal reconfiguration and impaired efficacy with low bolus propulsion. Increasing bolus viscosity greatly improves swallowing function in neurological patients.
Effects of viscosity on endothelial cell damage under acoustic droplet vaporization
Seda, Robinson; Singh, Rahul; Li, David; Pitre, John; Putnam, Andrew; Fowlkes, J. Brian; Bull, Joseph
2014-11-01
Acoustic droplet vaporization (ADV) is a process by which stabilized superheated microdroplets are able to undergo phase transition with the aid of focused ultrasound. Gas bubbles resulting from ADV can provide local occlusion of the blood vessels supplying diseased tissue, such as tumors. The ADV process can also induce bioeffects that increase vessel permeability, which is beneficial for localized drug delivery. Previous in vitro studies have demonstrated that vaporization at the endothelial layer will affect cell attachment and viability. Several hypotheses have been proposed to elucidate the mechanism of damage including the generation of normal and shear stresses during bubble expansion. A single 3.5 MHz ultrasound pulse consisting of 8 cycles (~2.3 μs) and a 6 MPa peak rarefactional pressure was used to induce ADV on endothelial cells in media of different viscosities. Carboxylmethyl cellulose was added to the cell media to increase the viscosity up to 300 cP to and aid in the reduction of stresses during bubble expansion. The likelihood of cell damage was decreased when compared to our control (~1 cP), but it was still present in some cases indicating that the mechanism of damage does not depend entirely on viscous stresses associated with bubble expansion. This work was supported by NIH Grant R01EB006476.
Świergiel, Jolanta; Bouteiller, Laurent; Jadżyn, Jan
2014-11-14
Impedance spectroscopy was used for the study of the static and dynamic behavior of the electrical conductivity of a hydrogen-bonded supramolecular polymer of high viscosity. The experimental data are discussed in the frame of the Stokes-Einstein and Stokes-Einstein-Debye models. It was found that the translational movement of the ions is due to normal Brownian diffusion, which was revealed by a fulfillment of Ohm's law by the electric current and a strictly exponential decay of the current after removing the electric stimulus. The dependence of the dc conductivity on the viscosity of the medium fulfills the Stokes-Einstein model quite well. An extension of the model, by including in it the conductivity relaxation time, is proposed in this paper. A breakdown of the Stokes-Einstein-Debye model is revealed by the relations of the dipolar relaxation time to the viscosity and to the dc ionic conductivity. The importance of the C=O···H-N hydrogen bonds in that breakdown is discussed.
Volatiles Which Increase Magma Viscosity
Webb, S.
2015-12-01
The standard model of an erupting volcano is one in which the viscosity of a decompressing magma increases as the volatiles leave the melt structure to form bubbles. It has now been observed that the addition of the "volatiles" P, Cl and F result in an increase in silicate melt viscosity. This observation would mean that the viscosity of selected degassing magmas would decrease rather than increase. Here we look at P, Cl and F as three volatiles which increase viscosity through different structural mechanisms. In all three cases the volatiles increase the viscosity of peralkaline composition melts, but appear to always decrease the viscosity of peraluminous melts. Phosphorus causes the melt to unmix into a Na-P rich phase and a Na-poor silicate phase. Thus as the network modifying Na (or Ca) are removed to the phosphorus-rich melt, the matrix melt viscosity increases. With increasing amounts of added phosphorus (at network modifying Na ~ P) the addition of further phosphorus causes a decrease in viscosity. The addition of chlorine to Fe-free aluminosilicate melts results in an increase in viscosity. NMR data on these glass indicates that the chlorine sits in salt-like structures surrounded by Na and/or Ca. Such structures would remove network-modifying atoms from the melt structure and thus result in an increase in viscosity. The NMR spectra of fluorine-bearing glasses shows that F takes up at least 5 different structural positions in peralkaline composition melts. Three of these positions should result in a decrease in viscosity due to the removal of bridging oxygens. Two of the structural positons of F, however, should result in an increase in viscosity as they require the removal of network-modifying atoms from the melt structure (with one of the structures being that observed for Cl). This would imply that increasing amounts of F might result in an increase in viscosity. This proposed increase in viscosity with increasing F has now been experimentally confirmed.
Effects of Damaged Starch on Viscosity of Rice Flour%损伤淀粉对大米粉粘度性质的影响
崔凯凯; 任永胜
2012-01-01
Different methods were used to get rice flour with different contents of damaged starch,and the effect of damaged starch on viscosity of rice flour were studied with Rapid Viscosity Analyser.The results showed that damaged starch obviously influenced the viscosity property of rice flour.The lower the content of damaged starch,the higher the pasting temperature,as well as the peak viscosity,the valley viscosity,the final viscosity,the retrogradation value.But it had no distinct influence on the attenuation value.%采用不同方法得到损伤淀粉含量不同的大米粉,通过快速粘度分析仪(Rapid Viscosity Analyser,RVA)测定大米粉糊化曲线研究了损伤淀粉对大米粉粘度性质的影响.实验结果表明,损伤淀粉含量越低,大米粉糊化温度、峰值粘度、谷值粘度、末值粘度和回生值越高,而损伤淀粉对衰减值的影响却并不显著.
Anwar Daud
2012-01-01
Full Text Available An oral-dissolving drug delivery system offers a solution for those patients having difficulty in swallowing tablets/capsules, and so on. Withania somnifera has been used to promote health and longevity by augmenting defenses against disease, arresting the aging process, revitalizing the body in debilitated conditions, and thus creating a sense of well-being. Commercially, it is available either in powder or liquid dosage forms that do not offer patient compliance. In the present study, an attempt has been made to formulate W. somnifera into thin oral films. An attempt was also made to study factors like the effect of the type of solvent used for casting of the film, effect of drying temperature, and viscosity of the solution on the mouth-dissolving film of W. somnifera Linn. The mouth-dissolving films were prepared by the solvent-casting method. Prepared films were evaluated for film-forming capacity, appearance of film, tack test, thickness, in vitro disintegration time, folding endurance, tensile strength, and percentage elongation. This study illustrated that selected process variables have an influence on the physicomechanical properties of the mouth-dissolving film of W. somnifera Linn. Water was found to be an excellent solvent for casting when hydroxypropylmethylcellulose was used as a film former. When mouth-dissolving film of W. somnifera Linn was dried at lower temperatures, it showed optimum physicomechanical performances. Viscosity of the solution plays an important role in physicomechanical properties of the film; as the viscosity of solution increases, there is an increase in folding endurance, tensile strength, and percentage elongation.
Viscosity of Campi Flregrei (Italy) magmas
Misiti, Valeria; Vetere, Francesco; Scarlato, Piergiorgio; Behrens, Harald; Mangiacapra, Annarita; Freda, Carmela
2010-05-01
Viscosity is an important factor governing both intrusive and volcanic processes. The most important parameters governing silicate melts viscosity are bulk composition of melt and temperature. Pressure has only minor effect at crustal depths, whereas crystals and bubbles have significant influence. Among compositional parameters, the water content is critical above all in terms of rheological behaviour of melts and explosive style of an eruption. Consequently, without an appropriate knowledge of magma viscosity depending on the amount of dissolved volatiles, it is not possible to model the processes (i.e., magma ascent, fragmentation, and dispersion) required to predict realistic volcanic scenarios and thus forecast volcanic hazards. The Campi Flegrei are a large volcanic complex (~150 km2) located west of the city of Naples, Italy, that has been the site of volcanic activity for more than 60 ka and represents a potential volcanic hazard owing to the large local population. In the frame of a INGV-DPC (Department of Civil Protection) project devoted to design a multidisciplinary system for short-term volcano hazard evaluation, we performed viscosity measurements, under dry and hydrous conditions, of primitive melt compositions representative of two Campi Flegrei eruptions (Minopoli-shoshonite and Fondo Riccio-latite). Viscosity of the two melts have been investigated in the high temperature/low viscosity range at atmospheric pressure in dry samples and at 0.5 GPa in runs having water content from nominally anhydrous to about 3 wt%. Data in the low temperature/high viscosity range were obtained near the glass transition temperature at atmospheric pressure on samples whose water contents vary from 0.3 up to 2.43 wt%. The combination of high- and low-viscosity data permits a general description of the viscosity as a function of temperature and water content using a modified Tamman-Vogel-Fulcher equation. logν = a+ --b--+ --d--×exp(g × w-) (T - c) (T - e) T (1) where
Witte, T S; Melkus, E; Walter, I; Senge, B; Schwab, S; Aurich, C; Heuwieser, W
2012-10-01
Persistent breeding-induced endometritis is ranked as the third most common medical problem in the adult mare and leads to enormous economic loss in horse breeding. In mares suffering from persistent breeding-induced endometritis, increased amounts of intrauterine (i.u.) fluid or viscous mucus in estrus or after breeding may act as a barrier for sperm and can contribute to low fertility. Current therapies of these mares aim to eliminate i.u. fluid and mucus by uterine lavage and/or administration of ecbolic drugs. Recently, i.u. administration of N-acetylcysteine (NAC) has been shown to support therapy in mares with endometritis. It was the objective of the present study to investigate effects of an oral administration of NAC on the viscosity of i.u. fluid in estrous mares. It was hypothesized that oral treatment with NAC reduces the viscosity of i.u. fluid and has a positive effect on the inflammatory response of the endometrium. Mares (n = 12) were included in the study as soon as estrus was detected (ovarian follicle >3.0 cm and endometrial edema), which was defined as Day 1. They were randomly assigned to a treatment (10 mg/kg NAC on Days 1-4) or a control group (no treatment). On days 1 and 5 i.u. mucus was collected and its rheologic properties were accessed. On Day 5, endometrial biopsies were obtained and evaluated for integrity of the luminal epithelium, number of polymorphonuclear neutrophils (PMN), staining for cyclooxygenase 2 (COX2), staining with Kiel 67 antigen (Ki-67), lectins and periodic acid Schiff (PAS). In the treatment group, viscosity of i.u. mucus increased significantly between Days 1 and 5 (P NAC treatment the mean number of PMN in endometrial biopsies was significantly lower compared to mares of the control group (1.9 ± 0.3 vs. 4.8 ± 0.4; P NAC treatment compared to control mares (P mucus in deep uterine glands differed significantly between groups (both P NAC treatment does not reduce viscosity of uterine mucus but has an
Shear viscosity of $\\beta$-stable nuclear matter
Benhar, Omar
2009-01-01
Viscosity plays a critical role in determining the stability of rotating neutron stars. We report the results of a calculation of the shear viscosity of $\\beta$~-~stable matter, carried out using an effective interaction based on a state-of-the-art nucleon-nucleon potential and the formalism of correlated basis functions. Within our approach the equation of state, determining the proton fraction, and the nucleon-nucleon scattering probability are consistently obtained from the same dynamical model. The results show that, while the neutron contribution to the viscosity is always dominant, above nuclear saturation density the electron contribution becomes appreciable.
Yamasaki, Tadashi
2016-04-01
Development of the satellite observations (GPS and/or InSAR) has allowed us to precisely measure surface deformation. However any geodetic observation by itself does not tell us a mechanism of the deformation. All we can do the most is to compare such an observation to some quantitative predictions, only from which we can deduce a possible deformation mechanism. We therefore need to understand characteristic deformation pattern for a given source mechanism. This study particularly pays attention to magmatic activity in depth as the source, aiming to distinguish magma-induced crustal deformation by better knowing how the activity can be reflected in geodetically observable surface deformation. A parallelized 3-D finite element code, OREGANO_VE [e.g., Yamasaki and Houseman, 2015, J. Geodyn., 88, 80-89], is used to solve the linear Maxwell visco-elastic response to an applied internal inflation/deflation of magma chamber. The rectangular finite element model is composed with a visco-elastic layer overlaid by an elastic layer with thickness of H, and the visco-elastic layer extends over the rest of crust and the uppermost mantle. The visco-elastic crust has a depth-dependent viscosity (DDV) as an exponential function of depth due to temperature-dependent viscosity: hc = h0 exp[c(1 - z/L0)], where h0 is the viscosity at the bottom of the crust, c is a constant; c > 0 for DDV model and c = 0 for uniform viscosity (UNV) model, z is the depth, and L0 is a reference length-scale. The visco-elastic mantle has a spatially uniform viscosity hm. The inflation and/or deflation of sill-like magma chamber is implemented by using the split node method developed by Melosh and Raefsky [1981, Bull. Seism. Soc. Am., 71, 1391-1400]. UNV model with c = 0 employed in this study shows that the inflation-induced surface uplift would abate with time by visco-elastic relaxation. The post-inflation subsidence would erase the uplift in ~ 50 - 100 times Maxwell relaxation time of the crust
Godwin Kafui Ayetor
2015-12-01
Full Text Available In this study, the effect of H2SO4 on viscosity of methyl esters from Jatropha oil (JCME, palm kernel oil (PKOME from Elaeis guineensis species, and coconut oil (COME has been studied. Effect of methanol to oil molar mass ratio on yield of the three feedstocks has also been studied. Methyl ester yield was decreased by esterification process using sulphuric acid anhydrous (H2SO4. Jatropha methyl ester experienced a viscosity reduction of 24% (4.1–3.1 mm2/s with the addition of 1% sulphuric acid. In this work palm kernel oil (PKOME, coconut oil (COME and Jatropha oil (JCME were used as feedstocks for the production of biodiesel to investigate optimum parameters to obtain high yield. For each of the feedstock, the biodiesel yield increased with increase in NaOH concentration. The highest yield was obtained with 1% NaOH concentration for all. The effect of methanol in the range of 4:1–8:1 (molar ratio was investigated, keeping other process parameters fixed. Optimum ratios of palm kernel oil and coconut oil biodiesels yielded 98% each at methanol:oil molar ratio of 8:1. The physiochemical properties obtained for each methyl showed superior properties compared with those reported in published data.
Yuanfang Wang; Baoyu Gao; Qinyan Yue; Yah Wang
2011-01-01
A coagulation/flocculation process using the composite floceulant polyaluminum chloride-epichlorohydrin dimethylamine (PAC-EPI-DMA) was employed for the treatment of an anionic azo dye (Reactive Brilliant Red K-2BP dye).The effect of viscosity (η),basicity (B =[OH]/[Al]) and organic content (Wp) on the flocculation performance as well as the mechanism of PAC-EPI-DMA flocculant were investigated.The η was the key factor affecting the dye removal efficiency of PAC-EPI-DMA.PAC-EPI-DMA with an intermediate η (2400 mPa-sec) gave higher decolorization efficiency by adsorption bridging and charge neutralization due to the co-effect of PAC and EPI-DMA polymers.The Wp of the composite flocculant was a minor important factor for the flocculation.The adsorption bridging of PAC-EPI-DMA with η of 300 or 4300 mPa.sec played an important role with the increase of Wp,whereasthe charge neutralization of them was weaker with the increase of Wp.There was interaction between Wp and B on the removal of reactive dye.The composite flocculant with intermediate viscosity and organic content was effective for the treatment of reactive dyeing wastewater,which could achieve high reactive dye removal efficiency with low organic dosage.
Shiels, C.; Butler, S. L.
2015-09-01
Mantle convection models with a low viscosity asthenosphere and high viscosity surface plates have been shown to produce very large aspect ratio convection cells like those inferred to exist in Earth's mantle and to exhibit two asthenospheric flow regimes. When the surface plate is highly mobile, the plate velocity exceeds the flow velocities in the asthenosphere and the plate drives a Couette-type flow in the asthenospheric channel. For sluggish plates, the flow velocities in the asthenosphere exceed the plate velocity and the asthenospheric flow is more Poiseuille-like. It has been shown that under certain circumstances, flows become increasingly Couette-like as the aspect ratio of the plate is increased in numerical simulations. These models also show an increase in the average surface heat flux with aspect ratio which is counterintuitive, as one would expect that large aspect ratio models would result in older and colder oceanic lithosphere. Previous investigations have used single internal heating rates and Rayleigh numbers and a plate formulation that did not preclude significant deformation within the plate. In this paper, we investigate the conditions necessary for Couette and Poiseuille asthenospheric flows and for surface heat flux to increase with plate aspect ratio by varying the internal heating rate, the Rayleigh number and the representation of surface plates in 2D mantle convection models Plates are represented as a high viscosity layer with (1) a free-slip top surface boundary condition and (2) a force-balance boundary condition that imposes a constant surface velocity within the plate. We find that for models with a free-slip surface boundary condition, the internal heating rate and Rayleigh number do not strongly affect the dominance of Couette or Poiseuille flows in the asthenosphere but the increase in surface heat flux with model aspect ratio in the Poiseuille asthenospheric flow regime increases with internal heating rate. For models using
LI Jinlong; HE Changchun; MA Jun; PENG Changjun; LIU Honglai; HU Ying
2011-01-01
The equation of state（EOS）for square-well chain fluid with variable range（SWCF-VR） developed in our previous work based on statistical mechanical theory for chemical association is employed for the correlations of surface tension and viscosity of common fluids and ionic liquids（ILs）.A model of surface tension for multi-component mixtures is presented by combining the SWCF-VR EOS and the scaled particle theory and used to produce the surface tension of binary and ternary mixtures.The predicted surface tensions are in excellent agreement with the experimental data with an overall average absolute relative deviation（AAD）of 0.36%.A method for the calculation of dynamic viscosity of common fluids and ILs at high pressure is presented by combining Eyring’s rate theory of viscosity and the SWCF-VR EOS.The calculated viscosities are in good agreement with the experimental data with the overall AAD of 1.44% for 14 fluids in 84 cases.The salient feature is that the molecular parameters used in these models are self-consistent and can be applied to calculate different thermodynamic properties such as pVT,vapor-liquid equilibrium,caloric properties,surface tension,and viscosity.
无
2010-01-01
Viscosity is an important physical parameter of fluid,and the Eyring viscosity equation is a popular viscosity theory.Based on the Eyring reaction rate equation and Boltzmann statistical theory,and including the probabilities of creating a hole in liquid and the transition to the neighboring hole,a modified Eyring viscosity equation was proposed.According to the structural characteristics of short-range order,liquid is treated as a quasi-lattice structure in a small region.The activation energy,which is the minimum energy needed for the molecule to jump to its neighboring hole because of the restriction of other molecules around it,was analytically calculated from an intermolecular Lennard-Jones potential function and a Stockmayer potential function.The viscosity values of 37 kinds of typical liquids at 25°C and the dependence of viscosity of three kinds of liquids on temperatures were calculated with this modified viscosity equation,and the calculated results agree with the experimental values to some extent.This work not only enriches the understanding of the mechanism of liquid viscosity,but also could provide some theoretical guides for the relevant studies and applications.
Juan D Latorre
2015-08-01
Full Text Available Previously, our laboratory has screened and identified Bacillus spp. isolates as direct-fed microbials (DFM. The purpose of the present study was to evaluate the cellulase and xylanase production of these isolates and select the most appropriate Bacillus spp. candidates for DFM. Furthermore, an in vitro digestive model, simulating different compartments of the gastrointestinal tract, was used to determine the effect of these selected candidates on digesta viscosity and Clostridium perfringens proliferation in different poultry diets. Production of cellulase and xylanase were based on their relative enzyme activity. Analysis of 16S rRNA sequence classified two strains as B. amyloliquefaciens and one of the strains as B. subtilis. The DFM was included at a concentration of 108 spores/g of feed in 5 different sterile soybean-based diets containing corn, wheat, rye, barley, or oat. After digestion time, supernatants from different diets were collected to measure viscosity, and C. perfringens proliferation. Additionally, from each in vitro simulated compartment, samples were taken to enumerate viable Bacillus-spores using a plate count method after heat-treatment. Significant (P<0.05 DFM-associated reductions in supernatant viscosity and C. perfringens proliferation were observed for all non-corn diets. These results suggest that antinutritional factors such as non-starch polysaccharides from different cereals can enhance viscosity and C. perfringens growth. Remarkably, dietary inclusion of the DFM that produce cellulase and xylanase reduced both viscosity and C. perfringens proliferation compared with control diets. Regardless of diet composition, 90% of the DFM spores germinated during the first 30 min in the crop compartment of the digestion model, followed by a noteworthy increased in the intestine compartment by ~2 log10, suggesting a full-life cycle development. Further studies to evaluate in vivo necrotic enteritis effects are in progress.
Avelino, Arturo
2008-01-01
We test a cosmological model which the only component is a pressureless fluid with a constant bulk viscosity as an explanation for the present accelerated expansion of the universe. We classify all the possible scenarios for the universe according to their past, present and future evolution. We test the viability of the model performing a Bayesian statistical analysis using the Gold 2006 (182 SNe) and ESSENCE + HST (192 SNe) type Ia supernovae (SNe Ia) data sets, imposing the second law of thermodynamics on the dimensionless constant bulk viscous coefficient and comparing the predicted age of the universe with the constraints in the age of the universe coming from the oldest globular clusters. The age of the universe is found to be 15.507 Gyr and 16.501 Gyr using the Gold 2006 and ESSENCE+HST SNe Ia data sets respectively. The best estimated values obtained for this model are similar to those obtained from the LCDM model for H_0 and \\chi^2_{min} using the same SNe Ia data sets and the estimated ages of the un...
Burak Felekoglu; Kamile Tosun; Bulent Baradan; Akin Altun; Bahadir Uyulgan [Dokuz Eylul University (Turkey). Faculty of Engineering
2006-09-15
Today, self-compacting mortars are preferred for repair purposes due to the application easiness and mechanical advantages. However, for self-compatibility, the paste phase must meet some certain criteria at fresh state. The cement as well as the ingredients of the paste, powders with cementitious, pozzolanic or inert nature and plasticizing chemical admixtures should be carefully chosen in order to obtain a suitable paste composition to enrich the granular skeleton of the mix. The physical properties of powders (shape, surface morphology, fineness, particle size distribution, particle packing) and physico-chemical (time-dependent hydration reactions, zeta potentials) interactions between cement powder and plasticizer should be taken into consideration. All these parameters affect the performance of fresh paste in different manners. There is no universally accepted agreement on the effect of these factors due to the complexity of combined action; thus, it is hard to make a generalization. This study deals with the selection of amount and type of powders from the viewpoint of fresh state rheology and mechanical performance. The influence of powder materials on self-compatibility, viscosity and strength were compared with a properly designed set of test methods (the mini-slump, V-funnel tests, viscosity measurements and compressive strength tests). It may be advised that, for each cement-powder-plasticizer mixture, a series of test methods can be used to determine the optimum content and type of materials for a specified workability.
Effect of Chlorine on the Viscosities and Structures of CaO-SiO2-CaCl2 Slags
Wang, Cui; Zhang, Jianliang; Liu, Zhengjian; Jiao, Kexin; Wang, Guangwei; Yang, Junqiang; Chou, Kuochih
2016-10-01
The viscosities of CaO-SiO2-CaCl2 (CaO/SiO2 = 1.12) slags were measured to elucidate the effect of chlorine with CaCl2 content from 0 to 15 mass pct on the slags at high temperatures, and the Raman spectra of the glassy slags were detected to account for the role of chlorine in modifying the structures of the slags. The viscosity was found to increase with decreasing temperature and to decrease with increasing chlorine content at a given temperature. The critical temperature (T CR) decreased from about 1675 K to 1621 K (1402 °C to 1348 °C) with increasing CaCl2 content from 5 to 15 mass pct, and the activation energy decreased from 226 to 152 kJ/mol with CaCl2 content increasing from 0 to 15 mass pct. Meanwhile, the Raman spectra gradually shifted to lower wavenumber, the fractions of Q 0 and Q 2 units increased and the Q 1 and Q 3 units decreased continuously, and the Q 3/Q 2 ratio generally decreased with increasing the chlorine content in the investigated slags; all of these results above demonstrated the role of network modifier of the chlorine in decreasing the degree of polymerization in the silicon-oxygen tetrahedra.
Avelino, Arturo
2010-01-01
We explore the viability of a bulk viscous matter-dominated Universe to explain the present accelerated expansion of the Universe. The model is composed by two fluids: a radiation component and a pressureless fluid with bulk viscosity of the form zeta = zeta_0 + zeta_1 H where zeta_0 and zeta_1 are constants and H is the Hubble parameter. The pressureless fluid characterizes both the baryon and dark matter components. We study all the possible scenarios for the Universe according to the values of zeta_0 and zeta_1 analyzing the behavior of the scale factor as well as the curvature scalar and the matter density. On the other hand, we test the model computing the best estimated values of zeta_0 and zeta_1 using the type Ia Supernovae (SNe Ia) and the shift parameter R of the Cosmic Microwave Radiation Anisotropies (CMB) probes. We find that the model fits well to both tests. We find also that from all the possible scenarios for the Universe, the preferred one by the best estimated values of (zeta_0, zeta_1) is ...
Ghosh, Sabyasachi; Roy, Victor; Serna, Fernando E; Krein, Gastão
2015-01-01
We have calculated the temperature dependence of shear $\\eta$ and bulk $\\zeta$ viscosities of quark matter due to quark-meson fluctuations. The quark thermal width originating from quantum fluctuations of quark-$\\pi$ and quark-$\\sigma$ loops at finite temperature is calculated with the formalism of real-time thermal field theory. Temperature-dependent constituent-quark and meson masses, and quark-meson couplings are obtained in the Nambu--Jona-Lasinio model. We found a non-trivial influence of the temperature-dependent masses and couplings on the Landau-cut structure of the quark self-energy. Our results for the ratios $\\eta/s$ and $\\zeta/s$, where $s$ is the entropy density (also determined in the Nambu--Jona-Lasinio model in the quasi-particle approximation), are in fair agreement with results of the literature obtained from different models and techniques. In particular, our result for $\\eta/s$ has a minimum very close to the conjectured AdS/CFT lower bound, $\\eta/s = 1/4\\pi$.
Ghosh, Sabyasachi; Peixoto, Thiago C.; Roy, Victor; Serna, Fernando E.; Krein, Gastão
2016-04-01
We have calculated the temperature dependence of shear η and bulk ζ viscosities of quark matter due to quark-meson fluctuations. The quark thermal width originating from quantum fluctuations of quark-π and quark-σ loops at finite temperature is calculated with the formalism of real-time thermal field theory. Temperature-dependent constituent-quark and meson masses and quark-meson couplings are obtained in the Nambu-Jona-Lasinio model. We found a nontrivial influence of the temperature-dependent masses and couplings on the Landau-cut structure of the quark self-energy. Our results for the ratios η /s and ζ /s , where s is the entropy density (also determined in the Nambu-Jona-Lasinio model in the quasiparticle approximation), are in fair agreement with results of the literature obtained from different models and techniques. In particular, our result for η /s has a minimum very close to the quantum lower bound, η /s =1 /4 π .
Viscosities of the quasigluon plasma
Bluhm, M; Redlich, K
2010-01-01
We investigate bulk and shear viscosities of the gluon plasma within relaxation time approximation to an effective Boltzmann-Vlasov type kinetic theory by viewing the plasma as describable in terms of quasigluon excitations with temperature dependent self-energies. The found temperature dependence of the transport coefficients agrees fairly well with available lattice QCD results. The impact of some details in the quasigluon dispersion relation on the specific shear viscosity is discussed.
Can bulk viscosity drive inflation
Pacher, T.; Stein-Schabes, J.A.; Turner, M.S.
1987-04-01
Contrary to other claims, we argue that, bulk viscosity associated with the interactions of nonrelativistic particles with relativistic particles around the time of the grand unified theory (GUT) phase transition cannot lead to inflation. Simply put, the key ingredient for inflation, negative pressure, cannot arise due to the bulk viscosity effects of a weakly-interacting mixture of relativistic and nonrelativistic particles. 13 refs., 1 fig.
Hughes, T.J.R.; Wells, G.N.; Wray, A.A.
2004-01-01
Energy transfers within large-eddy simulation (LES) and direct numerical simulation (DNS) grids are studied. The spectral eddy viscosity for conventional dynamic Smagorinsky and variational multiscale LES methods are compared with DNS results. Both models underestimate the DNS results for a very coa
Herterich, James G.
2014-02-02
The transport of a dilute suspension of particles through a channel with porous walls, accounting for the concentration dependence of the viscosity, is analyzed. In particular, we study two cases of fluid permeation through the porous channel walls: (1) at a constant flux and (2) dependent on the pressure drop across the wall. We also consider the effect of mixing the suspension first compared with point injection by considering inlet concentration distributions of different widths. We find that a pessimal inlet distribution width exists that maximizes the required hydrodynamic pressure for a constant fluid influx. The effect of an external hydrodynamic pressure, to compensate for the reduced transmembrane pressure difference due to osmotic pressure, is investigated. © 2014 American Institute of Chemical Engineers.
Temperature Dependence Viscosity and Density of Different Biodiesel Blends
Vojtěch Kumbár
2015-01-01
Full Text Available The main goal of this paper is to assess the effect of rapeseed oil methyl ester (RME concentration in diesel fuel on its viscosity and density behaviour. The density and dynamic viscosity were observed at various mixing ratios of RME and diesel fuel. All measurements were performed at constant temperature of 40 °C. Increasing ratio of RME in diesel fuel was reflected in increased density value and dynamic viscosity of the blend. In case of pure RME, pure diesel fuel, and a blend of both (B30, temperature dependence of dynamic viscosity and density was examined. Temperature range in the experiment was −10 °C to 80 °C. Considerable temperature dependence of dynamic viscosity and density was found and demonstrated for all three samples. This finding is in accordance with theoretical assumptions and reference data. Mathematical models were developed and tested. Temperature dependence of dynamic viscosity was modeled using a polynomial 3rd polynomial degree. Correlation coefficients R −0.796, −0.948, and −0.974 between measured and calculated values were found. Temperature dependence of density was modeled using a 2nd polynomial degree. Correlation coefficients R −0.994, −0.979, and −0.976 between measured and calculated values were acquired. The proposed models can be used for flow behaviour prediction of RME, diesel fuel, and their blends.
J. W. Grayson
2017-07-01
viscosities observed in some SOA. Finally, two quantitative structure–property relationship models (Sastri and Rao, 1992; Marrero-Morejón and Pardillo-Fontdevila, 2000 were used to predict the viscosity of alkanes, alcohols, and polyols with a C3–C6 carbon backbone. Both models show reasonably good agreement with measured viscosities for the alkanes, alcohols, and polyols studied here except for the case of a hexol, the viscosity of which is underpredicted by 1–3 orders of magnitude by each of the models.
Ye, Changwen; Pei, Xiangjun; Liu, J. C.
2016-12-01
Densities and viscosities have been measured for the n-octanol + aviation kerosene (AK) + phosphoric acid (H3PO4) system with the mass fraction of H3PO4 in the range from w = 0 to 0.26 and in the temperature of 293.15-333.15 K. According to the experimental data, the measured viscosities were found well correlated with the temperature and mass fraction of H3PO4, which were fitted to regression equations. The result shows that the dilution effect of AK is obvious under the same temperature and mass fraction of H3PO4.
Gauglitz, P.A.; Rassat, S.D.; Powell, M.R. [and others
1995-08-01
Several of the underground nuclear storage tanks at Hanford have been placed on a flammable gas watch list, because the waste is either known or suspected to generate, store, and episodically release flammable gases. Because retention and episodic release of flammable gases from these tanks containing radioactive waste slurries are critical safety concerns, Pacific Northwest Laboratory (PNL) is studying physical mechanisms and waste properties that contribute to the episodic gas release from these storage tanks. This study is being conducted for Westinghouse Hanford Company as part of the PNL Flammable Gas project. Previous investigations have concluded that gas bubbles are retained by the slurry or sludge that has settled at the bottom of the tanks; however, the mechanisms responsible for the retention of these bubbles are not well understood. Understanding the rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles and the dynamics of how these bubbles are released from the waste. The presence of gas bubbles is expected to affect the rheology of the sludge, specifically its viscosity and tensile and shear strengths, but essentially no literature data are available to assess the effect of bubbles. The objectives of this study were to conduct experiments and develop theories to understand better how bubbles are retained by slurries and sludges, to measure the effect of gas bubbles on the viscosity of simulated slurries, and to measure the effect of gas bubbles on the tensile and shear strengths of simulated slurries and sludges. In addition to accomplishing these objectives, this study developed correlations, based on the new experimental data, that can be used in large-scale computations of waste tank physical phenomena.
Viscosity and surface tension effects during multiphase flow in propped fractures
Dzikowski, Michał; Dąbrowski, Marcin
2017-04-01
Geological sequestration of CO2 was proposed as an important mechanism to reduce its emission into atmosphere. CO2 exhibits a higher affinity to organic matter than methane molecules and, potentially, it could be pumped and stored in shale reservoirs while enhancing late stage shale gas production. A successful analysis of CO2 sequestration in low matrix permeability rocks such as shales requires a thorough understanding of multiphase flow in stimulated rock fractures, which provide most significant pathways for fluids in such systems. Multiphase fracture flows are also of great relevance to brine, oil and gas migration in petroleum systems, water and stream circulation in geothermal reservoirs, and chemical transport of non-aqueous phase liquids in shallow hydrogeological systems, particularly in partially saturated zones. There are various physical models that describe phenomena taking place during multiphase flow through porous media. One of key aspects that need to be considered are pore-scale effects related to capillarity. Unfortunately, detailed models that describe motion and evolution of phase or component boundary require direct numerical simulations and spatial resolutions that are hard to reach when considering industrial relevant systems. Main aim of the presented work was the development of reduced 2.5D models based on Brinkman approximation of thin domain flow that would be able to capture local scale phenomena without expensive 3D simulations. Presented approach was designed specifically to tackle incompressible and immiscible systems and is based on Continuous Surface Force approach presented by Brackbill et al., implemented using Lattice Boltzmann Method. Presented approach where firstly validated against standard test cases with known classical solution and known experimental data. In the second part, we present and discuss two component, immiscible permeability data for rough and propped fracture obtained with our code for a rage of proppants
Ikenaga, Yuki; Nishi, Shohei; Komagata, Yuka; Saito, Masashi; Lagrée, Pierre-Yves; Asada, Takaaki; Matsukawa, Mami
2013-11-01
A pulse wave is the displacement wave which arises because of ejection of blood from the heart and reflection at vascular bed and distal point. The investigation of pressure waves leads to understanding the propagation characteristics of a pulse wave. To investigate the pulse wave behavior, an experimental study was performed using an artificial polymer tube and viscous liquid. A polyurethane tube and glycerin solution were used to simulate a blood vessel and blood, respectively. In the case of the 40 wt% glycerin solution, which corresponds to the viscosity of ordinary blood, the attenuation coefficient of a pressure wave in the tube decreased from 4.3 to 1.6 dB/m because of the tube stiffness (Young's modulus: 60 to 200 kPa). When the viscosity of liquid increased from approximately 4 to 10 mPa·s (the range of human blood viscosity) in the stiff tube, the attenuation coefficient of the pressure wave changed from 1.6 to 3.2 dB/m. The hardening of the blood vessel caused by aging and the increase of blood viscosity caused by illness possibly have opposite effects on the intravascular pressure wave. The effect of the viscosity of a liquid on the amplitude of a pressure wave was then considered using a phantom simulating human blood vessels. As a result, in the typical range of blood viscosity, the amplitude ratio of the waves obtained by the experiments with water and glycerin solution became 1:0.83. In comparison with clinical data, this value is much smaller than that seen from blood vessel hardening. Thus, it can be concluded that the blood viscosity seldom affects the attenuation of a pulse wave.
氦氖激光对几种溶液粘度的影响%Effect on the viscosity of solutions by He-Ne laser
杨颖; 马勇; 耿虹; 闫秀英
2001-01-01
目的:探讨氦氖激光对蒸馏水、自来水、NaCl溶液、葡萄糖溶液粘度的影响。方法:以特定的激光强度、经不同的照射时间处理溶液,用奥氏粘度计测定溶液的粘度。结果与结论:激光对蒸馏水和NaCl溶液粘度无明显影响。激光对自来水粘度的影响随照射时间的不同呈双向结果,照射时间在10 min以内粘度低于对照组,差异显著(P 0.05)。%To probe into the effect on the viscosity of distilled water natural water Nacl solution and glucose solution by He-Ne Laser. Ubbohde＇s viscosimeter was used to examine the solutions treated by different times of irradiation under the action of certain Laser power to determine its viscosity. He-Ne Laser has not an effect on the viscosity of distilled water and NaCl solution. Effect on the viscosity of the natural water by He-Ne Laser ,the irradiating times in ten minutes, the viscosity of natural water is markedly lower than that from control groups, which are significantly different(P 0.05)
Lyly, Marika; Ohls, Nora; Lähteenmäki, Liisa
2010-01-01
Background: Soluble fibre has been proposed to suppress appetite-related perceptions and it could thus contribute favourably to the regulation of energy intake and the increasing obesity problem. Objective: To investigate the effect of an oat ingredient rich in b-glucan on perceived satiety...... at different dietary fibre (DF) concentrations, energy levels and viscosity levels. Design: A total of 29 healthy volunteers, age 1939, mean BMI 23.2 kg/m2 participated in this study. Measurement of subjective perceptions (satiety, fullness, hunger, desire to eat something/the sample food and thirst......) was performed during a 180-min period after ingestion of the sample. There were altogether six samples: two beverages without fibre at energy levels 700 and 1,400 kJ; two beverages containing 5 or 10 g oat DF (2.5 and 5 g oat b-glucan, respectively) at energy level 700 kJ, one beverage containing 10 g oat DF/1...
Monsalvo, Matias Alfonso; Baylaucq, A.; Cisneros, Sergio;
2006-01-01
In this work new dynamic viscosity measurements for binary mixtures containing a refrigerant (HFC-134a, CF3CH2F) and a lubricant (TriEGDME, CH3O(CH2OCH2)(3)CH3) are reported. The measurements were carried out at temperatures between 293.15 and 373.15 K and pressures from 10 to 100 MPa, for two mo...... with a physical and theoretical background, such as the hard-sphere scheme, the free-volume model, and the friction theory....... for this binary system have been used to test the ability of several viscosity models having different origins and theoretical backgrounds. The considered models range from simple mixing rules, through empirical correlations, such as the self-referencing model and the LBC model, to recent approaches...
Avelino, Arturo; Nucamendi, Ulises, E-mail: avelino@ifm.umich.mx, E-mail: ulises@ifm.umich.mx [Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C-3, Ciudad Universitaria, CP. 58040, Morelia, Michoacán (Mexico)
2010-08-01
We explore the viability of a bulk viscous matter-dominated Universe to explain the present accelerated expansion of the Universe. The model is composed by a pressureless fluid with bulk viscosity of the form ζ = ζ{sub 0}+ζ{sub 1}H where ζ{sub 0} and ζ{sub 1} are constants and H is the Hubble parameter. The pressureless fluid characterizes both the baryon and dark matter components. We study the behavior of the Universe according to this model analyzing the scale factor as well as some curvature scalars and the matter density. On the other hand, we compute the best estimated values of ζ{sub 0} and ζ{sub 1} using the type Ia Supernovae (SNe Ia) probe. We find that from all the possible scenarios for the Universe, the preferred one by the best estimated values of (ζ{sub 0},ζ{sub 1}) is that of an expanding Universe beginning with a Big-Bang, followed by a decelerated expansion at early times, and with a smooth transition in recent times to an accelerated expansion epoch that is going to continue forever. The predicted age of the Universe is a little smaller than the mean value of the observational constraint coming from the oldest globular clusters but it is still inside of the confidence interval of this constraint. A drawback of the model is the violation of the local second law of thermodynamics in redshifts z∼>1. However, when we assume ζ{sub 1} = 0, the simple model ζ = ζ{sub 0} evaluated at the best estimated value for ζ{sub 0} satisfies the local second law of thermodynamics, the age of the Universe is in perfect agreement with the constraint of globular clusters, and it also has a Big-Bang, followed by a decelerated expansion with the smooth transition to an accelerated expansion epoch in late times, that is going to continue forever.
Schipper, D.J.; Napel, ten W.E; Dowson, D.
1998-01-01
In this paper the influence of the viscosity-pressure relationship on the film thickness for the line contact situation is presented. The viscosity-pressure behaviour of many lubricants differs significantly from the behaviour according to Barus which is commonly used in EHL. This topic is of intere
Schipper, Dirk J.; ten Napel, W.E.; Dowson, D.
1998-01-01
In this paper the influence of the viscosity-pressure relationship on the film thickness for the line contact situation is presented. The viscosity-pressure behaviour of many lubricants differs significantly from the behaviour according to Barus which is commonly used in EHL. This topic is of
Domínguez, JC; Oliet, M.; Alonso, M. V.; Rodriguez, F.; Madsen, B.
2016-07-01
In the present study, the chemorheological behavior of a bio-based polyfurfuryl alcohol (PFA) resin has been determined by rheological isothermal tests at different curing temperatures for the post-gel curing stage of the resin, using three different amounts of catalyst (2, 4 and 6 wt %). Instead of modeling the evolution of the complex viscosity using a widely used chemorheological model such as the Arrhenius model for each tested temperature, the change of the complex viscosity as a function of the degree-of-cure was predicted using a new exponential type model. In this model, the logarithm of the normalized degree-of-cure is used to predict the behavior of the logarithm of the normalized complex viscosity. The model shows good quality of fitting with the experimental data for 4 and 6 wt % amounts of catalyst. For the 2 wt % amount of catalyst, scattered data leads to a slightly lower quality of fitting. Altogether, it is demonstrated that the new exponential model is a good alternative to conventional chemorheological models due to its simplicity and suitability.
Gaciño, Félix M.; Comuñas, María J.P.; Regueira Muñiz, Teresa
2015-01-01
A new calibration procedure was used and four new temperatureprobes have been placed on afalling-body viscometer to improve its accuracy. The new configuration and calibrationprocedure allow measuring viscosities with an uncertainty of 3.5% at pressures up to 150 MPa.This device was employed...... to measure viscosities as a function of temperature and pressure fortwo ionic liquids (ILs): 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphateand 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate.Besides, we have measured the flow curves at pressures up to 75 MPa and shear rates up...... to1000 s-1in a Couette rheometer. Dynamic viscosities were correlated as function of temperature and pressure with four differentequations with average absolute deviation lower than 1%. The pressure-viscosity and temperature-viscosity derived properties were analyzed and compared with those of other...
Jing Peng; Li Chen
2016-01-01
Objective:To study the effect of salvianolate combined with meglumine adenosine cyclphosphate on blood viscosity, inflammatory factors and NT-proBNP in angina pectoris patients after percutaneous coronary intervention (PCI).Methods:A total of 130 angina pectoris patients who received PCI treatment in our hospital from May 2012 to October 2015 were selected for study, patients' medical records were retrospectively analyzed, they were divided into the experimental group and the control group based on the different medication schemes after PCI, experimental group received routine treatment combined with salvianolate and meglumine adenosine cyclphosphate treatment after operation, and control group received conventional medical treatment after operation. The changes of perioperative blood viscosity, inflammatory factor and NT-proBNP content were compared between two groups.Results:After PCI, the blood viscosity indexes as well as inflammatory factor and NT-proBNP levels of experimental group were significantly lower than those before PCI (P0.05), inflammatory factor and NT-proBNP levels were significantly lower than those before PCI (P<0.05); 7 days after PCI, the high-shear whole blood viscosity, low-shear whole blood viscosity, plasma viscosity and aggregation index as well as TNF-α, sICAM-1, sVCAM-1, LP-PLA2, NT-proBNP, D-dimer and PTEN levels of experimental group were significantly lower than those of control group (P<0.05).Conclusions: Salvianolate combined with meglumine adenosine cyclphosphate can reduce the blood viscosity of patients with angina pectoris after PCI, and can also reduce inflammation and improve heart pump function.
Ali, M.; Alim, M. A.; Nasrin, R.; Alam, M. S.
2016-07-01
An analysis is performed to study the free convection heat and mass transfer flow of an electrically conducting incompressible viscous fluid about a semi-infinite inclined porous plate under the action of radiation, chemical reaction in presence of magnetic field with variable viscosity. The dimensionless governing equations are steady, two-dimensional coupled and non-linear ordinary differential equation. Nachtsgeim-Swigert shooting iteration technique along with Runge-Kutta integration scheme is used to solve the non-dimensional governing equations. The effects of magnetic parameter, viscosity parameter and chemical reaction parameter on velocity, temperature and concentration profiles are discussed numerically and shown graphically. Therefore, the results of velocity profile decreases for increasing values of magnetic parameter and viscosity parameter but there is no effect for reaction parameter. The temperature profile decreases in presence of magnetic parameter, viscosity parameter and Prandtl number but increases for radiation parameter. Also, concentration profile decreases for the increasing values of magnetic parameter, viscosity parameter and reaction parameter. All numerical calculations are done with respect to salt water and fixed angle of inclination of the plate.
Ali, M., E-mail: ali.mehidi93@gmail.com [Department of Mathematics, Bangladesh University of Engineering and Technology, Dhaka-1000 (Bangladesh); Department of Mathematics, Chittagong University of Engineering and Technology, Chittagong-4349 (Bangladesh); Alim, M. A., E-mail: maalim@math.buet.ac.bd; Nasrin, R., E-mail: rehena@math.buet.ac.bd [Department of Mathematics, Bangladesh University of Engineering and Technology, Dhaka-1000 (Bangladesh); Alam, M. S., E-mail: shahalammaths@gmail.com [Department of Mathematics, Chittagong University of Engineering and Technology, Chittagong-4349 (Bangladesh)
2016-07-12
An analysis is performed to study the free convection heat and mass transfer flow of an electrically conducting incompressible viscous fluid about a semi-infinite inclined porous plate under the action of radiation, chemical reaction in presence of magnetic field with variable viscosity. The dimensionless governing equations are steady, two-dimensional coupled and non-linear ordinary differential equation. Nachtsgeim-Swigert shooting iteration technique along with Runge-Kutta integration scheme is used to solve the non-dimensional governing equations. The effects of magnetic parameter, viscosity parameter and chemical reaction parameter on velocity, temperature and concentration profiles are discussed numerically and shown graphically. Therefore, the results of velocity profile decreases for increasing values of magnetic parameter and viscosity parameter but there is no effect for reaction parameter. The temperature profile decreases in presence of magnetic parameter, viscosity parameter and Prandtl number but increases for radiation parameter. Also, concentration profile decreases for the increasing values of magnetic parameter, viscosity parameter and reaction parameter. All numerical calculations are done with respect to salt water and fixed angle of inclination of the plate.
Cosmology with bulk viscosity and the gravitino problem
Buoninfante, L
2016-01-01
The gravitino problem is revisited in the framework of cosmological models in which the primordial cosmic matter is described by a relativistic imperfect fluid. Dissipative effects (or bulk viscosity effects) arise owing to the different cooling rates of the fluid components. We show that the effects of the bulk viscosity allow to avoid the late abundance of gravitinos. In particular, we found that for a particular choice of the parameters characterizing the cosmological model, the gravitino abundance turns out to be independent on the reheating temperature.
Ya-Zhong Wang; Yun Wen
2016-01-01
Objective:To analyze the effect of safflower injection on lower limb fracture healing as well as blood viscosity and blood coagulation function.Methods: A total of 118 patients with fracture of lower limb were randomly divided into observation group and control group (n=59), control group received conventional surgical treatment, observation group received surgery + postoperative safflower injection treatment, and then differences in serum content of bone turnover indexes and bone metabolism indexes as well as levels of thrombelastogram parameters and blood coagulation function indexes were compared between two groups after 1 month of treatment.Results:Bone turnover indexes sBAP, PINP and BGP content in serum of observation group after 1 month of treatment were higher than those of control group while sCTX, sTAP and TRAP-5b content were lower than those of control group; bone metabolism indexes Ca2+ and 25-OH-VitD content in serum were higher than those of control group while P, PTH andβ-CTX content were lower than those of control group; thrombelastogram parameters R time and K time were longer than those of control group while MA value, G value and angle level were lower than those of control group; blood coagulation function indexes PLT, FIB and D-D content in serum were lower than those of control group while PT, APTT and TT levels were higher than those of control group.Conclusions:Safflower injection can promote postoperative fracture end healing in patients with fracture of lower limb, and also plays a positive role in reducing blood viscosity and optimizing blood coagulation function.
Usha, R.; Ramasami, T
2004-01-30
The effect of urea and n-propanol on circular dichroism (CD) and viscosity of purified type1 collagen solution at various temperatures and differential scanning calorimetry (DSC) of rat-tail tendon (RTT) collagen fibre have been studied. CD reveals a spectrum with a positive peak at around 220 nm and a negative peak at 200 nm characteristics of collagen triple helix. The molar ellipticity decreases as the concentration of urea increases up to particular concentration (collagen solution treated with 265 {mu}M of urea) and after that it increases (collagen solution treated with 500 {mu}M of urea). There is a linear decrease in molar ellipticity as the concentration of n-propanol increases. Denaturation temperature of urea and n-propanol treated with purified collagen solution has been studied using viscosity method. Additives such as urea and n-propanol decrease the thermal stability of collagen triple helix in solution and in RTT collagen fibre. Thermal helix to coil transition of urea and n-propanol treated collagen depends on the degree of hydration and the concentration of these additives. Thermodynamic parameters such as the peak temperature, enthalpy of activation, and energy of activation for collagen-gelatin transition for native, urea and n-propanol treated RTT collagen fibre has been calculated using DSC. The change in the thermodynamic parameters has been observed for native, urea and n-propanol treated RTT collagen fibres. The experimental results show that the change in the water structure, dehydration and desolvation induced by different additives such as urea and n-propanol on RTT may vary with the type of denaturation.
Kamiguri, Junko; Tsuchiya, Noriko; Hidema, Ruri; Yatabe, Zenji; Shoji, Masahiko; Hashimoto, Chihiro; Pansu, Robert Bernard; Ushiki, Hideharu
2012-01-01
The contraction process of living Vorticella sp. in polymer solutions with various viscosities has been investigated by image processing using a high-speed video camera. The viscosity of the external fluid ranges from 1 to 5mPa·s for different polymer additives such as hydroxypropyl cellulose, polyethylene oxide, and Ficoll. The temporal change in the contraction length of Vorticella sp. in various macromolecular solutions is fitted well by a stretched exponential function based on the nucleation and growth model. The maximum speed of the contractile process monotonically decreases with an increase in the external viscosity, in accordance with power law behavior. The index values approximate to 0.5 and this suggests that the viscous energy dissipated by the contraction of Vorticella sp. is constant in a macromolecular environment.
Soltani, Omid; Akbari, Mohammad
2016-10-01
In this paper, the effects of temperature and particles concentration on the dynamic viscosity of MgO-MWCNT/ethylene glycol hybrid nanofluid is examined. The experiments carried out in the solid volume fraction range of 0 to 1.0% under the temperature ranging from 30 °C to 60 °C. The results showed that the hybrid nanofluid behaves as a Newtonian fluid for all solid volume fractions and temperatures considered. The measurements also indicated that the dynamic viscosity increases with increasing the solid volume fraction and decreases with the temperature rising. The relative viscosity revealed that when the solid volume fraction enhances from 0.1 to 1%, the dynamic viscosity increases up to 168%. Finally, using experimental data, in order to predict the dynamic viscosity of MgO-MWCNT/ethylene glycol hybrid nanofluids, a new correlation has been suggested. The comparisons between the correlation outputs and experimental results showed that the suggested correlation has an acceptable accuracy.
Horner, Angela M; Jayne, Bruce C
2008-05-01
Separate studies of terrestrial and aquatic locomotion are abundant, but research addressing locomotion in transitional environments (e.g. mud) is scant. The African lungfish (Protopterus annectens) moves in a gradation of water to mud conditions during seasonal droughts, and breathes air. Thus, the lungfish was an ideal organism for our study to determine the effects of a wide range of viscosities on lateral undulatory swimming and to simulate some of the muddy conditions early tetrapods may have encountered. Regardless of viscosity, several aspects of lungfish swimming were similar to those of other swimming vertebrates including: posteriorly propagated muscle activity that was unilateral and alternated between the left and right sides at each longitudinal location, and posterior increases in the amount of bending, the amplitude of muscle activity and the timing differences between muscle activity and bending. With increased viscosity (1-1000 cSt), significant increases occurred in the amount of lateral bending of the vertebral column and the amplitude of muscle activity, particularly in the most anterior sites, but the distance the fish traveled per tail beat decreased. The magnitude of the phase shift between EMG onset relative to bending increased by as much as 13% of a cycle with increased viscosity, so that the muscles were increasingly active during lengthening rather than shortening. Therefore, with increased viscosity the relationship between axial muscle activity and bending in the lungfish became more dissimilar rather than converging on the motor pattern used by other ectothermic vertebrates when undulating in fully terrestrial environments.
Dark goo: Bulk viscosity as an alternative to dark energy
Gagnon, Jean-Sebastien
2011-01-01
We present a simple (microscopic) model in which bulk viscosity plays a role in explaining the present acceleration of the universe. The effect of bulk viscosity on the Friedmann equations is to turn the pressure into an "effective" pressure containing the bulk viscosity. For a sufficiently large bulk viscosity, the effective pressure becomes negative and could mimic a dark energy equation of state. Our microscopic model includes self-interacting spin-zero particles (for which the bulk viscosity is known) that are added to the usual energy content of the universe. We study both background equations and linear perturbations in this model. We show that a dark energy behavior is obtained for reasonable values of the two parameters of the model (i.e. the mass and coupling of the spin-zero particles) and that linear perturbations are well-behaved. There is no apparent fine tuning involved. We also discuss the conditions under which hydrodynamics holds, in particular that the spin-zero particles must be in local eq...
Kim, Chang-Beom; Lim, Jaeho; Hong, Hyobong; Kresh, J. Yasha; Wootton, David M.
2015-07-01
Detailed knowledge of the blood velocity distribution over the cross-sectional area of a microvessel is important for several reasons: (1) Information about the flow field velocity gradients can suggest an adequate description of blood flow. (2) Transport of blood components is determined by the velocity profiles and the concentration of the cells over the cross-sectional area. (3) The velocity profile is required to investigate volume flow rate as well as wall shear rate and shear stress which are important parameters in describing the interaction between blood cells and the vessel wall. The present study shows the accurate measurement of non-Newtonian blood velocity profiles at different shear rates in a microchannel using a novel translating-stage optical method. Newtonian fluid velocity profile has been well known to be a parabola, but blood is a non-Newtonian fluid which has a plug flow region at the centerline due to yield shear stress and has different viscosities depending on shear rates. The experimental results were compared at the same flow conditions with the theoretical flow equations derived from Casson non-Newtonian viscosity model in a rectangular capillary tube. And accurate wall shear rate and shear stress were estimated for different flow rates based on these velocity profiles. Also the velocity profiles were modeled and compared with parabolic profiles, concluding that the wall shear rates were at least 1.46-3.94 times higher than parabolic distribution for the same volume flow rate.
Peršin, Zdenka; Devetak, Miha; Drevenšek-Olenik, Irena; Vesel, Alenka; Mozetič, Miran; Stana-Kleinschek, Karin
2013-08-14
Extreme non-equilibrium oxygen plasma was used for the deep functionalisation of viscose materials used for the healing of chronic wounds. Those thermal effects, which usually appear during plasma treatment due to the influence of charged particles, were avoided effectively by using electrode-less discharge at a very low power density of 25 W/l volume. A huge flux of neutrally reactive atoms at room temperature of 3x10(23)m(-2)s(-1), allowed for the effective diffusion of O-atoms into inter-fibril space and thus the activation of fibrils throughout the non-woven materials. Apart from the standard Wilhelmy balance and pedant drop method for determining the absorption dynamics on a macroscopic scale, optical polarisation microscopy was applied for studying the microscopic effects. The sorption characteristics were determined for saline solution, exudate, and blood and the results showed a dramatic improvement. Focusing on hydrophobic recovery prevention, the modified samples were stored for 10 days in air, nitrogen, and argon atmospheres. Some ageing effects occurred, whilst the absorption properties were independent of the storage atmosphere.
Avelino, Arturo; Nucamendi, Ulises, E-mail: avelino@ifm.umich.mx, E-mail: ulises@ifm.umich.mx [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio C-3, Ciudad Universitaria, CP. 58040 Morelia, Michoacan (Mexico)
2009-04-15
We test a cosmological model which the only component is a pressureless fluid with a constant bulk viscosity as an explanation for the present accelerated expansion of the universe. We classify all the possible scenarios for the universe predicted by the model according to their past, present and future evolution and we test its viability performing a Bayesian statistical analysis using the SCP ''Union'' data set (307 SNe Ia), imposing the second law of thermodynamics on the dimensionless constant bulk viscous coefficient {zeta}-tilde and comparing the predicted age of the universe by the model with the constraints coming from the oldest globular clusters. The best estimated values found for {zeta}-tilde and the Hubble constant H{sub 0} are: {zeta}-tilde = 1.922{+-}0.089 and H{sub 0} = 69.62{+-}0.59 (km/s)Mpc{sup -1} with a {chi}{sup 2}{sub min} = 314 ({chi}{sup 2}{sub d.o.f} = 1.031). The age of the universe is found to be 14.95{+-}0.42 Gyr. We see that the estimated value of H{sub 0} as well as of {chi}{sup 2}{sub d.o.f} are very similar to those obtained from {Lambda}CDM model using the same SNe Ia data set. The estimated age of the universe is in agreement with the constraints coming from the oldest globular clusters. Moreover, the estimated value of {zeta}-tilde is positive in agreement with the second law of thermodynamics (SLT). On the other hand, we perform different forms of marginalization over the parameter H{sub 0} in order to study the sensibility of the results to the way how H{sub 0} is marginalized. We found that it is almost negligible the dependence between the best estimated values of the free parameters of this model and the way how H{sub 0} is marginalized in the present work. Therefore, this simple model might be a viable candidate to explain the present acceleration in the expansion of the universe.
Seismic Constraints on the Mantle Viscosity Structure beneath Antarctica
Wiens, Douglas; Heeszel, David; Aster, Richard; Nyblade, Andrew; Wilson, Terry
2015-04-01
Lateral variations in upper mantle viscosity structure can have first order effects on glacial isostatic adjustment. These variations are expected to be particularly large for the Antarctic continent because of the stark geological contrast between ancient cratonic and recent tectonically active terrains in East and West Antarctica, respectively. A large misfit between observed and predicted GPS rates for West Antarctica probably results in part from the use of a laterally uniform viscosity structure. Although not linked by a simple relationship, mantle seismic velocities can provide important constraints on mantle viscosity structure, as they are both largely controlled by temperature and water content. Recent higher resolution seismic models for the Antarctic mantle, derived from data acquired by new seismic stations deployed in the AGAP/GAMSEIS and ANET/POLENET projects, offer the opportunity to use the seismic velocity structure to place new constraints on the viscosity of the Antarctic upper mantle. We use an Antarctic shear wave velocity model derived from array analysis of Rayleigh wave phase velocities [Heeszel et al, in prep] and examine a variety of methodologies for relating seismic, thermal and rheological parameters to compute a suite of viscosity models for the Antarctic mantle. A wide variety of viscosity structures can be derived using various assumptions, but they share several robust common elements. There is a viscosity contrast of at least two orders of magnitude between East and West Antarctica at depths of 80-250 km, reflecting the boundary between cold cratonic lithosphere in East Antarctica and warm upper mantle in West Antarctica. The region beneath the Ellsworth-Whitmore Mtns and extending to the Pensacola Mtns. shows intermediate viscosity between the extremes of East and West Antarctica. There are also significant variations between different parts of West Antarctica, with the lowest viscosity occurring beneath the Marie Byrd Land (MBL
Viscosity of liquid undercooled tungsten
Paradis, Paul-François; Ishikawa, Takehiko; Yoda, Shinichi
2005-05-01
Knowledge of the viscosity and its temperature dependence is essential to improve metallurgical processes as well as to validate theoretical and empirical models of liquid metals. However, data for metals with melting points above 2504K could not be determined yet due to contamination and containment problems. Here we report the viscosity of tungsten, the highest melting point metal (3695K), measured by a levitation technique. Over the 3350-3700-K temperature range, which includes the undercooled region by 345K, the viscosity data could be fitted as η(T )=0.108exp[1.28×105/(RT)](mPas). At the melting point, the datum agrees with the proposed theoretical and empirical models of liquid metals but presents atypical temperature dependence, suggesting a basic change in the mechanism of momentum transfer.
Bacterial accumulation in viscosity gradients
Waisbord, Nicolas; Guasto, Jeffrey
2016-11-01
Cell motility is greatly modified by fluid rheology. In particular, the physical environments in which cells function, are often characterized by gradients of viscous biopolymers, such as mucus and extracellular matrix, which impact processes ranging from reproduction to digestion to biofilm formation. To understand how spatial heterogeneity of fluid rheology affects the motility and transport of swimming cells, we use hydrogel microfluidic devices to generate viscosity gradients in a simple, polymeric, Newtonian fluid. Using video microscopy, we characterize the random walk motility patterns of model bacteria (Bacillus subtilis), showing that both wild-type ('run-and-tumble') cells and smooth-swimming mutants accumulate in the viscous region of the fluid. Through statistical analysis of individual cell trajectories and body kinematics in both homogeneous and heterogeneous viscous environments, we discriminate passive, physical effects from active sensing processes to explain the observed cell accumulation at the ensemble level.
Carmen María Romero
2011-12-01
Full Text Available In this work we present the effect of temperatureon the viscosities of aqueous solutionsof 3-aminopropanoic acid, 4-aminobutanoicacid, 5-aminopentanoic acidand 6-aminohexanoic acid as a functionof concentration. The experimental measurementswere done from 293.15 K to308.15 K. At each temperature the experimentaldata were fi tted to the Tsangaris-Martin equation and the B viscosity coefficient was determined. The dependenceof the B coeffi cients on the number ofcarbon atoms of the amino acids is linear,so the contribution of polar and apolargroups was established. The results areinterpreted in terms of amino acid hydration.
Klyukin, Y.; Lowell, R. P.; Bodnar, R. J.
2016-12-01
In order to develop realistic fluid flow models for crustal fluids, the physical and thermodynamic properties of the fluid, including the viscosity, must be known over the range of temperature, pressure and composition (PTx) conditions of interest. Many crustal fluids are reasonably well approximated by the system H2O-NaCl, and the model that is most often used to estimate viscosities of hydrothermal fluids is that of Palliser and McKibbin 1998 (P&M). Examination of the P&M model shows regions of PTx space in which calculated values are inconsistent with experimental data, and predicts trends in viscosity that are unexpected and inconsistent with known fluid behavior. The P&M model is especially unreliable at pressures greater than those on the liquid-vapor-halite coexistence curve and less than that along the liquid-vapor curve for pure H2O and the pure H2O critical isochore. We developed a model to calculate viscosity of H2O-NaCl fluids that shows good correlation with experimental values and predicts trends that are consistent with known or expected behavior outside of the region where experimental data are available. The revised model determines the viscosity of H2O-NaCl at PTx of interest based on the viscosity of H2O (estimated by IAPWS 2008 Viscosity Formulation) at T* and P, where T* is a polynomial function of x and T. The revised model can be used to estimate the viscosity over the range 0-1000 °C, ≤500 MPa and 0-100 wt. % NaCl. Viscosities predicted by the revised model agree with experimental values mostly within ±10%, whereas differences between experimental values and those predicted by the P&M model extend from -40% to >20%, especially for higher salinity fluids. The revised model shows smooth trends in viscosity versus temperature or salinity without discontinuities, unlike the P&M model. As expected, an increase in temperature at constant Px (decrease in density) results in a decrease in viscosity, while an increase in salinity at constant PT
Asadi, Amin; Asadi, Meisam; Rezaei, Mohammadhosein
2016-01-01
-lubricant shows Newtonian behavior in all the studied temperatures and solid concentrations. Furthermore, the experimental results showed that the dynamic viscosity decreased as the temperature increased. It is also revealed that increasing the solid concentration leads to increasing the dynamic viscosity...... on the experimental data, a new model to predict the dynamic viscosity of the studied nano-lubricant in terms of temperature and solid concentration has been proposed....
Zhou, Yang; Li, Yixue; Qian, Wen; He, Bi
2016-09-01
Based on dissipative particle dynamics (DPD) methods and experimental data, we used an empirical relationship between the DPD temperature and the real temperature to build a model that describes the viscosity of molten TNT fluids. The errors in the predicted viscosity based on this model were no more than 2.3 %. We also studied the steady-state shear rheological behavior of molten TNT fluids containing nanoparticles ("nanofluids"). The dependence of the nanofluid viscosity on the temperature was found to satisfy an Arrhenius-type equation, η = Ae (B/T) , where B, the flow activation energy, depends on particle content, size, and shape. We modified the Einstein-type viscosity model to account for the effects of nanoparticle solvation in TNT nanofluids. The resulting model was able to correctly predict the viscosities of suspensions containing nano- to microsized particles, and did not require any changes to the physical background of Einstein's viscosity theory. Graphical Abstract The revised Einstein viscosity model that correctly predict the viscosity of TNT suspensions containing nanoparticles.
Smits, CHM; Veldman, A; Verkade, HJ; Beynen, AC
1998-01-01
Two diets, with or without a nonfermentable carboxymethylcellulose (CMC) with high viscosity, were fed to broiler chickens beginning at 2 wk of age to study whether the anti-nutritive effect of gelling fibers on Lipid digestibility maybe associated with reduced intestinal bile salt concentration. Mo
Riisgård, Hans Ulrik; Larsen, Poul Scheel
2009-01-01
Beating cilia are important organelles, not only for water pumping in many active filter-feeding organisms, but also for the swimming activity of ciliates and other aquatic organisms that use cilia for propulsion. The present study concerns the effect of temperature-dependent viscosity of the amb...
Shinn, Sara E; Gilley, Alex D; Proctor, Andrew; Anthony, Nicolas B
2015-03-11
CLA egg accumulation studies using cis, trans (c,t) isomers have been effective, but they reported adverse egg quality. trans, trans (t,t) CLA isomers have shown superior nutritional effects in rodent studies, but reports of t,t CLA-rich yolks are limited. The objectives were to determine the effect of t,t CLA-rich soy oil in feed on egg yolk viscosity, and yolk quality during refrigerated storage. Yolk fatty acids, viscosity, weight, index, moisture, pH, and vitelline membrane strength (VMS) were determined at 0, 20, and 30 storage days. CLA had minimal effect on fatty acid profiles, relative to c,t reports. CLA-rich yolk viscosity was greater than controls, and CLA yolks maintained higher viscosities during storage. Yolk weight and index were not affected by t,t CLA-rich soy oil. Yolks with the greatest CLA concentrations had the greatest VMS after 20 days of storage, and yolks containing lower CLA levels maintained greater VMS throughout 30 days of storage, relative to controls.
Sehlke, Alexander; Whittington, Alan G.
2017-01-01
The authors regret some of the information presented in the original article was incorrect. The coefficients for five sub-parameters (s1 to s5) to calculate Sconf in Table 6 are incorrect, which resulted in lower Sconf values, affecting the viscosity prediction near the glass transition temperature (Tg). We provide the correct coefficients (s1 to s5) for in Table 6.
An, Xiaowei; Du, Xiao; Duan, Donghong; Shi, Lijuan; Hao, Xiaogang; Lu, Houfang; Guan, Guoqing; Peng, Changjun
2017-01-04
A series of new hydroxypyridine-based ionic liquids (ILs) are synthesized and applied in CO2 capture through chemical absorption, in which one IL, i.e., tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]), shows a viscosity as low as 193 cP with an absorption capacity as high as 1.20 mol CO2 per mol IL. Because the traditional anion-CO2 absorption mechanism cannot provide an explanation for the influences of cations and temperature on CO2 absorption capacity, herein, a novel cation-participating absorption mechanism based on the proton transfer is proposed to explain the high absorption capacity and the existence of a turning point of absorption capacity with the increase of temperature for the capture of CO2 using [P4444][n-Op] (n = 2, 3, 4) ILs. Also, the relationship between the viscosity of ILs and the linear interaction energy is proposed for the first time, which can guide how to design and synthesize ILs with low viscosity. Quantum chemistry calculations, which are based on the comprehensive analysis of dipole moment, cation-anion interaction energy and surface electrostatic potential, indicate that the different viscosities of hydroxypyridine-based ILs and the changes after CO2 absorption mainly resulted from the different distribution of negative charges in the anion.
Effects of Several Factors on Viscosity of Alumina-spinel Slurries
SHA Jianmin; LIU Kaiqi; LIU Zuocai
2004-01-01
The effects of several commercial dispersants, including AN- 2000, ammonium polyacrylate , sodium tripolyphosphate, sodium hexametaphosphate, and of solids loading and of electro-fused magnesia on rheological propertiesof aqueous alumina-spinel slurries were studied.The results reveal that AN- 2000 is the most effective one among the selected dispersants for alumina-spinel slurries.With 0.5% weight of AN-2000, the 57vol% solids loadobtained at shear rate of 50s-1 .
Zhen WANG; Hui ZHANG
2014-01-01
In this work, we obtain the global existence and uniqueness of classical solu-tions to a viscous liquid-gas two-phase model with mass-dependent viscosity and vacuum in one dimension, where the initial vacuum is allowed. We get the upper and lower bounds of gas and liquid masses n and m by the continuity methods which we use to study the compressible Navier-Stokes equations.
Pohlmann, Thomas
1996-02-01
The vertical eddy viscosity ( Av) is estimated using a three-dimensional baroclinic shelf sea model that treats the temperature as a prognostic quantity. Av is calculated by means of a turbulent closure approach proposed by Kochergin [(1987) Three-dimensional coastal ocean models, American Geophysical Union, pp. 201-208] which is closely related to a Mellor and Yamada [(1974) Journal of Atmospheric Science, 31, pp. 1791-1806] level-2-model that has been used very successfully in a large number of applications. The annual cycle of the vertical eddy viscosity is discussed by looking at horizontal and vertical A v-distributions for the year 1988. These examples show that the vertical eddy viscosity is subject to a pronounced annual cycle which can be related to heating and cooling processes as well as to mixing induced by wind and bottom friction. A comparison of these results with A v-distributions calculated for the year 1987 additionally demonstrates a strong inter-annual variability.
A brief review on viscosity of nanofluids
Mishra, Purna Chandra; Mukherjee, Sayantan; Nayak, Santosh Kumar; Panda, Arabind
2014-10-01
Since the past decade, rapid development in nanotechnology has produced several aspects for the scientists and technologists to look into. Nanofluid is one of the incredible outcomes of such advancement. Nanofluids (colloidal suspensions of metallic and nonmetallic nanoparticles in conventional base fluids) are best known for their remarkable change to enhanced heat transfer abilities. Earlier research work has already acutely focused on thermal conductivity of nanofluids. However, viscosity is another important property that needs the same attention due to its very crucial impact on heat transfer. Therefore, viscosity of nanofluids should be thoroughly investigated before use for practical heat transfer applications. In this contribution, a brief review on theoretical models is presented precisely. Furthermore, the effects of nanoparticles' shape and size, temperature, volume concentration, pH, etc. are organized together and reviewed.
Bulk and shear viscosity in Hagedorn fluid
Tawfik, A.; Wahba, M. [Egyptian Center for Theoretical Physics (ECTP), MTI University, Faculty of Engineering, Cairo (Egypt)
2010-11-15
Assuming that the Hagedorn fluid composed of known particles and resonances with masses m <2 GeV obeys the first-order theory (Eckart) of relativistic fluid, we discuss the transport properties of QCD confined phase. Based on the relativistic kinetic theory formulated under the relaxation time approximation, expressions for bulk and shear viscosity in thermal medium of hadron resonances are derived. The relaxation time in the Hagedorn dynamical fluid exclusively takes into account the decay and eventually van der Waals processes. We comment on the in-medium thermal effects on bulk and shear viscosity and averaged relaxation time with and without the excluded-volume approach. As an application of these results, we suggest the dynamics of heavy-ion collisions, non-equilibrium thermodynamics and the cosmological models, which require thermo- and hydro-dynamics equations of state. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Bulk and Shear Viscosity in Hagedorn Fluid
Tawfik, A
2010-01-01
Assuming that the Hagedorn fluid composed of known particles and resonances with masses $m<2\\,$GeV obeys the {\\it first-order} theory (Eckart) of relativistic fluid, we discuss the transport properties of QCD confined phase. Based on the relativistic kinetic theory formulated under the relaxation time approximation, expressions for bulk and shear viscosity in thermal medium are derived. The relaxation time in the Hagedorn dynamical fluid exclusively takes into account the decay and eventually van der Waals processes. We comment on the {\\it in-medium} thermal effects on bulk and shear viscosities and averaged relaxation time with and without the excluded-volume approach. As an application of these results, we suggest the dynamics of heavy-ion collisions, non-equlibrium thermodynamics and the cosmological models, which require thermo and hydrodynamics equations of state.
The effect of temperature dependence of viscosity on a Brownian heat engine
Taye, Mesfin Asfaw; Duki, Solomon Fekade
2015-12-01
We modeled a Brownian heat engine as a Brownian particle that hops in a periodic ratchet potential where the ratchet potential is coupled with a spatially varying temperature. The strength for the viscous friction γ( x) is considered to decrease exponentially when the temperature T( x) of the medium increases ( γ( x) = B e - AT( x)) as proposed originally by Reynolds [O. Reynolds, Phil. Trans. R. Soc. London 177, 157 (1886)]. Our result depicts that the velocity of the motor is considerably higher when the viscous friction is temperature dependent than that of the case where the viscous friction is temperature independent. The dependence of the efficiency η as well as the coefficient of performance of the refrigerator P ref on model parameters is also explored. If the motor designed to achieve a high velocity against a frictional drag, in the absence of external load f, we show that Carnot efficiency or Carnot refrigerator is unattainable even at quasistatic limit as long as the viscous friction is temperature dependent A ≠ 0. On the contrary, in the limit A → 0 or in general in the presence of an external load (for any A) f ≠ 0, at quasistatic limit, Carnot efficiency or Carnot refrigerator is attainable as long as the heat exchange via kinetic energy is omitted. For all cases, far from quasistatic limit, the efficiency and the coefficient of performance of the refrigerator are higher for constant γ case than the case where γ is temperature dependent. On the other hand, if one includes the heat exchange at the boundary of the heat baths, Carnot efficiency or Carnot refrigerator is unattainable even at quasistatic limit. Moreover, the dependence for the optimized and maximum power efficiencies on the determinant model parameters is explored.
Nefzaoui, Elyes
2010-01-01
An experimental study of liquid drop impacts on a granular medium is proposed. Four fluids were used to vary physical properties: pure distilled water, water with glycerol at 2 concentrations 1:1 and 1:2 v/v and water with Tween 20 at the concentration of 0.1g/l. The drop free fall height was varied to obtain a Weber number (We) between 10 and 2000. Results showed that obtained crater morphologies highly depend on the impacting drop kinetic energy E_{K}. Different behaviours during the drop spreading, receding and absorption are highlighted as function of the fluids viscosity and surface tension. Experimental absorption times are also commented and compared with a simplified theoretical model. Drops maximal extensions and craters diameters were found to scale as $We^{1/5}$ and $E_K^{1/5}$ respectively. In both cases, found dependencies are smaller than those reported in literature: $We^{1/4}$ for drop impacts on solid or granular surfaces and $E_K^{1/4}$ for spherical solid impacts on granular media.
Schellart, W. P.
2009-10-01
Three-dimensional laboratory subduction models are presented investigating the influence of the slab/upper mantle viscosity ratio (η SP/η UM) on the slab bending radius ( RB), with η SP/η UM = 66-1375. Here, RB is non-dimensionalized by dividing it by the upper mantle thickness ( TUM). The results show that RB/ TUM varies with time, reaching a maximum when the subduction velocity is maximum. Furthermore, RB/ TUM increases approximately linearly with increasing η SP/η UM for the investigated viscosity range. The model results show that the slab bending force ( FBe) and the energy dissipation during bending (Ф Be) are small compared to the negative buoyancy force of the slab ( FBu) and the potential energy release during sinking (Ф Bu). Maxima in Ф Be/Ф Bu (≈ FBe/ FBu) are reached in the early stage of subduction when RB/ TUM is minimum and the slab tip is at 220-440 km depth. Maximum Ф Be/Ф Bu increases with increasing η SP/η UM, with Ф Be/Ф Bu(max) = 0.06, 0.11, 0.18 and 0.22 for η SP/η UM = 66, 217, 709 and 1375, respectively. For subduction depths > 220-440 km, Ф Be/Ф Bu = 0.02-0.11 for all viscosity ratios. Assuming that in nature η SP/η UM glucose syrup and silicone oil as modelling materials, highlight the importance of accurate control on temperature during an experiment. New material investigations show that the viscosity of these two materials decreases exponentially with temperature in the range 3-33 °C, their density decreases approximately linearly with temperature, and their coefficient of thermal volumetric expansion is 3.8-4.2 × 10 - 4 C - 1 (glucose syrup) and 9.2 × 10 - 4 C - 1 (silicone oil).
Amir Hossein Saeedi Dehaghani
2016-12-01
Full Text Available Due to the high viscosity of heavy crude oils, production from these reservoirs is a demanding task. To tackle this problem, reducing oil viscosity is a promising approach. There are various methods to reduce viscosity of heavy oil: heating, diluting, emulsification, and core annular flow. In this study, dilution approach was employed, using industrial solvents and gas condensate. The viscosity of two Iranian heavy crude oils was measured by mixing with solvents at different temperatures. Dilution of both oil samples with toluene and heptane, resulted in viscosity reduction. However, their effect became less significant at higher concentrations of diluent. Because of forming hydrogen bonds, adding methanol to heavy crude oil resulted in higher viscosity. By adding condensate, viscosity of each sample reduced. Gas condensate had a greater impact on heavier oil; however, at higher temperatures its effect was reduced. Diluting with naphtha decreased heavy oil viscosity in the same way as n-heptane and toluene. Besides experimental investigation, different viscosity models were evaluated for prediction of heavy oil/solvent viscosity. It was recognized that Lederer' model is the best one.
Anti-inflammatory effects of hyaluronan in arthritis therapy: Not just for viscosity
Kayo Masuko
2009-04-01
Full Text Available Kayo Masuko1, Minako Murata2, Kazuo Yudoh2, Tomohiro Kato1, Hiroshi Nakamura31Department of Biochemistry; 2Institute of Medical Science, St. Marianna University School of Medicine, Kawasaki-shi, Kanagawa, Japan; 3Department of Joint Disease and Rheumatism, Nippon Medical School, Bunkyo-ku, Tokyo, JapanAbstract: Hyaluronic acid (HA has been widely used for viscosupplementation of diseased or aged articular joints. However, recent investigations have revealed the active anti-inflammatory or chondroprotective effect of HA, suggesting its potential role in attenuation of joint damage. In particular, interactions between HA and other inflammatory mediators are attracting interest. This review summarizes several aspects of recent investigations of the anti-inflammatory effects of HA in arthritis.Keywords: hyaluronan, inflammation, chondroprotection
Kshirsagar, A. M.; Tayade, D. T.
2012-10-01
S-triazine and thiocarbamide group containing drug create their own identity in the drug, pharmaceutical and medicinal sciences in last four decades. Hence, the viscometric measurements of recently synthesized drugs viz. 1-(4-hydroxy-6-methyl)-S-triazino-3-phenylthiocarbamide (L1) and 1-(4-hydroxy-6-methyl)-S-triazino-3-methylthiocarbamide (L2), were carried out at 60% various percentage of solvent to investigate effect of structure, on group of S-triazinothiocarbamides. The result obtained during this investigation directly through light on the dipole association of compound, intermolecular attraction between solute and solvent, dielectric constant of medium, polarizability and mutual compensation of dipoles and useful for drug absorption, transmission, stability, activity and effect of drug. %K 1-(4-hydroxy-6-methyl)-S-triazino-3-phenylthiocarbamide (L1) and 1-(4-hydroxy-6-methyl)-S-triazino-3-methylthiocarbamide (L2), dioxane-water mixture, viscometric measurements.
Bulk viscosity and deflationary universes
Lima, J A S; Waga, I
2007-01-01
We analyze the conditions that make possible the description of entropy generation in the new inflationary model by means of a nearequilibrium process. We show that there are situations in which the bulk viscosity cannot describe particle production during the coherent field oscillations phase.
The Universe With Bulk Viscosity
无
2003-01-01
Exact solutions for a model with variable G, A and bulk viscosity areobtained. Inflationary solutions with constant (de Sitter-type) and variable energydensity are found. An expanding anisotropic universe is found to isotropize duringits expansion but a static universe cannot isotropize. The gravitational constant isfound to increase with time and the cosmological constant decreases with time asAo∝t-2.
Baylaucq, A.; Boned, C.; Canet, X.;
2005-01-01
.15 and for several methane compositions. Although very far from real petroleum fluids, these mixtures are interesting in order to study the potential of extending various models to the simulation of complex fluids with asymmetrical components (light/heavy hydrocarbon). These data (575 data points) have been...... discussed in the framework of recent representative models (hard sphere scheme, friction theory, and free volume model) and with mixing laws and two empirical models (particularly the LBC model which is commonly used in petroleum engineering, and the self-referencing model). This comparative study shows...
Effects of surface oxide species and contents on SiC slurry viscosity
NING Shufan; LI Hongyan; CHEN Wei; LIU Bin; CHEN Shoutian
2005-01-01
The disadvantageous effects of colloidal SiO2 layer and micro-content of metal oxide adsorbed on SiC powder surface on SiC slurry stable dispersion were studied, and the novel method to avoid this disadvantage was proposed. By acidwashing, on the one hand, because the maximum Zeta potential of SiC powder increases to 72.49 mV with the decreasing content of metal oxide adsorbed on the SiC powder surface, the repulsion force between SiC powders that dispersed in slurry is enhanced, thus the SiC powder can be fully dispersed in slurry. On the other hand, after HF acidwashing, with the OH- group adsorbed on SiC powder surface destroyed and replaced by the F- ion, the hydrogen bond adsorbed on the OH-group is also destroyed. Therefore, the surface property of the SiC powder is changed from hydrophilic to hydrophobic;H2O that adsorbed on SiC powder surface is released and can flow freely, and it actually increases the content of the effective flow phase in the slurry. These changes of SiC powder surface property can be proved by XPS and FTIR analysis. Fivolume fraction of SiC powder in the slurry is maximized to 61.5 vol.%.
Riquelme, Mario; Verscharen, Daniel
2016-01-01
In low-collisionality plasmas, velocity-space instabilities are a key mechanism providing an effective collisionality for the plasma. We use particle-in-cell (PIC) simulations to study the interplay between electron and ion-scale velocity-space instabilities and their effect on electron pressure anisotropy, viscous heating, and thermal conduction. The adiabatic invariance of the magnetic moment in low-collisionality plasmas leads to pressure anisotropy, $p_{\\perp,j} > p_{||,j}$, if the magnetic field $\\vec{B}$ is amplified ($p_{\\perp,j}$ and $p_{||,j}$ denote the pressure of species $j$ [electron, ion] perpendicular and parallel to $\\vec{B}$). If the resulting anisotropy is large enough, it can in turn trigger small-scale plasma instabilities. Our PIC simulations explore the nonlinear regime of the mirror, ion-cyclotron, and electron whistler instabilities, through continuous amplification of the magnetic field $|\\vec{B}|$ by an imposed shear in the plasma. In the regime $1 \\lesssim \\beta_j \\lesssim 20$ ($\\be...
Tim Huber
2016-01-01
Full Text Available Aqueous solutions of sodium hydroxide (NaOH and urea are a known and versatile solvent for cellulose. The dissolution of cellulose occurs at subambient temperatures through the formation of a cellulose-NaOH-urea “inclusion complex” (IC. NaOH and urea form a hydrate layer around the cellulose chains preventing chain agglomeration. Urea is known to stabilize the solution but its direct role is unknown. Using viscometry and quartz crystal microbalance with dissipation monitoring (QCM-D it could be shown that the addition of urea reduced the solutions viscosity of the tested solutions by almost 40% and also increased the gelation temperature from approximately 40°C to 90°C. Both effects could also be observed in the presence of additional cellulose powder serving as a physical cross-linker. Using Fourier transform infrared (FTIR spectroscopy during heating, it could be shown that a direct interaction occurs between urea and the cellulose molecules, reducing their ability to form hydrogen bonds with neighbouring chains.
Viscosity kernel of molecular fluids
Puscasu, Ruslan; Todd, Billy; Daivis, Peter
2010-01-01
, temperature, and chain length dependencies of the reciprocal and real-space viscosity kernels are presented. We find that the density has a major effect on the shape of the kernel. The temperature range and chain lengths considered here have by contrast less impact on the overall normalized shape. Functional...... forms that fit the wave-vector-dependent kernel data over a large density and wave-vector range have also been tested. Finally, a structural normalization of the kernels in physical space is considered. Overall, the real-space viscosity kernel has a width of roughly 3–6 atomic diameters, which means...
Riquelme, Mario A.; Quataert, Eliot; Verscharen, Daniel
2016-06-01
In low-collisionality plasmas, velocity-space instabilities are a key mechanism providing an effective collisionality for the plasma. We use particle-in-cell (PIC) simulations to study the interplay between electron- and ion-scale velocity-space instabilities and their effect on electron pressure anisotropy, viscous heating, and thermal conduction. The adiabatic invariance of the magnetic moment in low-collisionality plasmas leads to pressure anisotropy, {{Δ }}{p}j\\equiv {p}\\perp ,j-{p}\\parallel ,j\\gt 0, if the magnetic field {\\boldsymbol{B}} is amplified ({p}\\perp ,j and {p}\\parallel ,j denote the pressure of species j (electron, ion) perpendicular and parallel to {\\boldsymbol{B}}). If the resulting anisotropy is large enough, it can in turn trigger small-scale plasma instabilities. Our PIC simulations explore the nonlinear regime of the mirror, IC, and electron whistler instabilities, through continuous amplification of the magnetic field | {\\boldsymbol{B}}| by an imposed shear in the plasma. In the regime 1≲ {β }j≲ 20 ({β }j\\equiv 8π {p}j/| {\\boldsymbol{B}}{| }2), the saturated electron pressure anisotropy, {{Δ }}{p}{{e}}/{p}\\parallel ,{{e}}, is determined mainly by the (electron-lengthscale) whistler marginal stability condition, with a modest factor of ˜1.5-2 decrease due to the trapping of electrons into ion-lengthscale mirrors. We explicitly calculate the mean free path of the electrons and ions along the mean magnetic field and provide a simple physical prescription for the mean free path and thermal conductivity in low-collisionality β j ≳ 1 plasmas. Our results imply that velocity-space instabilities likely decrease the thermal conductivity of plasma in the outer parts of massive, hot, galaxy clusters. We also discuss the implications of our results for electron heating and thermal conduction in low-collisionality accretion flows onto black holes, including Sgr A* in the Galactic Center.
Smith, P. M.; Baker, L. J.; Asimow, P. D.; Gurnis, M. C.
2007-12-01
Seismic velocity and attenuation studies have shown that 5-20 km thick low velocity layers exist above seismically fast slabs and are associated with broad zones of high attenuation in many subduction zones. These observations are generally interpreted as formation of hydrous phases by dehydration of the slab, although the impact of water in nominally anhydrous minerals (NAM) on seismic wave propagation is largely unknown. Recent petrological experiments on hydrous peridotite at subduction zone conditions suggest that chlorite will be stable adjacent to the subducting slab in sufficient quantities to be a significant water sink. We use a scheme that couples a petrological model (pHMELTS) with a 2-D thermal and variable viscosity flow model (ConMan) to model energy and mass transfer within a subduction zone. By varying input parameters including the convergence rate and slab dip we have developed models for cases in the Costa-Rica and Izu- Bonin-Marianas arc systems and are able to predict major and trace element compositions of primary melts, as well as geophysical observables, such as the topography and geoid. We find that the emergence of a slab- adjacent low-viscosity channel (LVC) is a natural consequence of the thermal and chemical controls on mantle dynamics and feedback between them. In our earlier models, as the LVC is dragged downwards by the subducting slab, hornblende breaks down at about 2.5 GPa and other hydrous phases such as serpentine are secondary in importance to the NAM water reservoir. The spatial limit of the LVC is the water-saturated solidus of the hydrated peridotite; the LVC thickens as the peridotite is progressively depleted by melting and the solidus migrates into the warmer wedge, despite water replenishment at depth. pHMELTS is a hybrid of the pMELTS model of Ghiorso and co-workers and includes amphiboles, serpentines and micas. Chlorite was lacking but we have recently rectified this omission. Following De Capitani and co- workers, we
Surface dilatational viscosity of Langmuir monolayers
Lopez, Juan; Vogel, Michael; Hirsa, Amir
2003-11-01
With increased interest in microfluidic systems, interfacial phenomena is receiving more attention. As the length scales of fluid problems decrease, the surface to volume ratio increases and the coupling between interfacial flow and bulk flow becomes increasingly dominated by effects due to intrinsic surface viscosities (shear and dilatational), in comparison to elastic effects (due to surface tension gradients). The surface shear viscosity is well-characterized, as cm-scale laboratory experiments are able to isolate its effects from other interfacial processes (e.g., in the deep-channel viscometer). The same is not true for the dilatational viscosity, because it acts in the direction of surface tension gradients. Their relative strength scale with the capillary number, and for cm-scale laboratory flows, surface tension effects tend to dominate. In microfluidic scale flows, the scaling favors viscosity. We have devised an experimental apparatus which is capable of isolating and enhancing the effects of dilatational viscosity at the cm scales by driving the interface harmonically in time, while keeping the interface flat. In this talk, we shall present both the theory for how this works as well as experimental measurements of surface velocity from which we deduce the dilatational viscosity of several monolayers on the air-water interface over a substantial range of surface concentrations. Anomalous behavior over some range of concentration, which superficially indicates negative viscosity, maybe explained in terms of compositional effects due to large spatial and temporal variations in concentration and corresponding viscosity.
DanLi; ZhiminLiu; JunLiu; XiaogangZhang; ShougangWang; XifengZhang
2001-01-01
Synchrotron radiation small-angle X-ray scattering(SAXS) and the viscosity technique were used to investigate the effect of dissolved CO2 in toluene on the conformation of polystyrene(PS) in the solution.The viscosity of PS solution decreases faster with increasing antisolvent CO2 pressure than that of the solvent in the absence of the polymer.the intrinsic viscosity [η] calculated using the wellknown Huggins equation decreases with antisolvent pressure.It was found that the second virial coefficient A2 and the apparent mean-square radius of gyration1/2 decreases with pressure of antisolvent CO2.All these phenomena can be attributed to the shrink of PS chain in the course of adding the gas antisolvent because the intercation between the polymer and solvent becomes weaker.The values1/2 at different pressures obtained from SAXS data agree reasonably with those calculated from Flory theory using the viscosity data determined in this work.This implies that Flory theory,which has been used widely for the solutions of polymers in liquid solvents,is also applicable to the polymer solution with gas antisolvent.
Sadeghi, A A; Ebadzadeh, T; Raissi, B; Ghashghaie, S; Fateminia, S M A
2013-02-14
In the present study, electrophoretic deposition (EPD) was used to obtain dense layers of TiO(2) in four organic media-methanol, ethanol, 1-propanol, and butanol-with different TiO(2) nanoparticle concenterations of 1-8 g/L. Microstructural study of the obtained layers by scanning electron (SEM) and optical microscope (OM) revealed that the multistep EPD technique could effectively prevent crack formation across the layer compared with the single-step method and will consequently increase the critical cracking thickness (CCT). The quality of EPD layers was also affected by viscosity. According to SEM and atomic force microscope (AFM) results, as the viscosity of the medium increased, more compact layers were formed which can be attributed to the lower deposition rates in heavier alcohols. High deposition rate in methanol and ethanol was also confirmed by zeta potential results. Suspension viscosity was interestingly observed to control the threshold concentration above which crack formation would occur. These values were measured to be 3 and 5 g/L for methanol and ethanol, respectively. However, in suspensions based on more viscous alcohols, the threshold concentration increased to 8 g/L which implied the decisive role of medium on concentration limits. It indicates that by employing organic vehicles of higher viscosity it is possible to maintain the CCT values obtained in less viscous media with no need to decrease the colloidal concentration of the suspension.
Koguchi, Takashi; Nakajima, Hisao; Koguchi, Hiromi; Wada, Masahiro; Yamamoto, Yuji; Innami, Satoshi; Maekawa, Akio; Tadokoro, Tadahiro
2003-10-01
This study was performed to clarify how dietary fiber (DF) with different viscosities would be associated with dietary RNA metabolism. Male Wistar strain rats, four weeks old, were fed diets containing a 3% (w/w) yeast RNA and a 5% (w/w) viscous DF for five days. Viscosity of DF samples used, in order of strength, were xanthan gum (XG) > guar gum (GG) > locust bean gum (LBG) > karaya gum (KG) > pectin (PE) = arabic gum (AG) > CM-cellulose (CMC) = inulin (IN). The serum uric acid concentration in the viscous DF groups significantly decreased as compared with that in the cellulose (CL) group. The urinary excretions of uric acid and allantoin in the respective groups given AG, GG, IN, KG, PE, and XG were significantly suppressed as compared with those in the CL group. The fecal RNA excretion was markedly increased in the IN, KG, PE, and XG groups in comparison to the CL group. The DF with high viscosity significantly suppressed RNA digestion by RNase A and decreased uptakes of 14C-labeled adenosine and adenosine 5'-monophosphate (5'-AMP) in rat jejunum. The results reveal that the suppressive effect of DF on elevation of serum uric acid concentration induced by dietary RNA in rats is associated with the strength of DF viscosity. The mechanism by which this is accomplished is suggested to be attributed to the inhibitions of digestion for dietary RNA and/or absorption of the hydrolyzed compounds.
A. Amin
2016-12-01
Full Text Available This study aimed to investigate the fuel properties like density, viscosity and calorific value of trans-esterified methyl ester using castor biodiesel and their blends with No. 2 diesel. Empirical correlations are proposed to predict the kinematic viscosity, density, and calorific value for a mixture of castor oil and No. 2 diesel. Kay mixing rule shows a good prediction for the fuel properties under study. Several polynomials are fitted using least square method, and the fitted equations show a good agreement with the experimental data from our study. The developed equations could be used as universal formulas to predict the kinematic viscosity, density, and calorific value for castor oil and No. 2 diesel blend. The equations can be used to optimize the mixing ratio of the castor oil/No. 2 diesel for different applications. Blending of castor oil with No. 2 diesel- in the range of 20% castor oil, will not violate the required specification of diesel engines.
Chakraborty S.
2002-01-01
Full Text Available The flow of a viscous incompressible electrically conducting fluid on a continuous moving flat plate in presence of uniform transverse magnetic field, is studied. The flat plate which is continuously moving in its own plane with a constant speed is considered to be isothermally heated. Assuming the fluid viscosity as an inverse linear function of temperature, the nature of fluid velocity and temperature in presence of uniform magnetic field are shown for changing viscosity parameter at different layers of the medium. Numerical solutions are obtained by using Runge-Kutta and Shooting method. The coefficient of skin friction and the rate of heat transfer are calculated at different viscosity parameter and Prandt l number. .
Bock, Steffen; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa
2002-08-01
Transport properties of pure carbon dioxide have been calculated from the intermolecular potential using the classical trajectory approach. Results are reported for shear viscosity, viscomagnetic coefficients, and self-diffusion in the dilute-gas limit and in the temperature range of 200-1500 K for the three recently proposed carbon dioxide potential energy hypersurfaces. Agreement with the measurements is, in general, within the experimental error. The calculations indicate that the corrections in the second-order approximation and those due to the angular-momentum polarization for the viscosity are small, Bukowski [et al.] potential energy hypersurface (1999) with the experimental viscosity data is consistent with the rigid-rotor assumption made in the calculations being reasonable for the three properties considered.
Pantokratoras, A
2007-01-01
The problem of forced convection along an isothermal, constantly moving plate is a classical problem of fluid mechanics that has been solved for the first time in 1961 by Sakiadis (1961). Thereafter, many solutions have been obtained for different aspects of this class of boundary layer problems. Solutions have been appeared including mass transfer, varying plate velocity, varying plate temperature, fluid injection and fluid suction at the plate. The work by Hassanien (1997) belongs to the above class of problems, including a linearly varying velocity and the variation of fluid viscosity with temperature. The author obtained similarity solutions considering that viscosity varies as an inverse function of temperature. However, the Prandtl number, which is a function of viscosity, has been considered constant across the boundary layer. It has been already confirmed in the literature that the assumption of constant Prandtl number leads to unrealistic results (Pantokratoras, 2004, 2005). The objective of the pres...
Samuel S.OKOYA
2016-01-01
Neglecting the consumption of the material, a steady incompressible flow of an exothermic reacting third-grade fluid with viscous heating in a circular cylindrical pipe is numerically studied for both cases of constant viscosity and Reynolds’ viscosity model. The coupled ordinary differential equations governing the flow in cylindrical coordinates, are transformed into dimensionless forms using appropriate transformations, and then solved numerically. Solutions using Maple are presented in tabular form and given in terms of dimensionless central fluid velocity and temperature, skin friction and heat transfer rate for three parametric values in the Reynoldsʼ case. The numerical results for the velocity and temperature fields are also presented through graphs. Bifurcationsare discussed using shooting method. Comparisons are also made between the present results and those of previous work, and thus verify the validity of the provided numerical solutions. Important properties of thermal criticality are provided for variable viscosity para- meter and reaction order. Further numerical results are presented in the form of tables and graphs for transition of physical parame- ters, while varying certain flow and fluid material parameters. Also, the flow behaviour of the reactive fluid of third-grade is com- pared with those of the Newtonian reactive fluid.
Murphy, S.; Sauerwein, B.; Drickamer, H.G.; Schuster, G.B. (Univ. of Illinois, Urbana, IL (United States))
1994-12-22
The spectroscopy of cyanine dyes was examined at atmospheric pressure and at high pressure in a series of alcohols and other solvents. Variation of external pressure provides the means to control viscosity over a wide range in one solvent at constant temperature. The findings reveal that the nonradiative relaxation of cyanines in fluid solution can occur when the motion leading to the formation of the cis isomer is stopped completely. Analysis of the viscosity dependence of the nonradiative relaxation rate constant reveals consistent deviation from the Kramers-DSE relation. 33 refs., 5 figs., 2 tabs.
VAJRAVELU Kuppalapalle; PRASAD Kerehalli Vinayaka; NG Chiu-On
2013-01-01
A numerical study is carried out to study the effects of the temperature dependent viscosity on the flow and heat transfer of a nanofluid over a flat surface in the presence of viscous dissipation.The governing nonlinear partial differential equations are transformed into nonlinear ordinary differential equations,and are solved numerically by the Keller-box method.The numerical results indicate that the effect of nanoparticle volume fraction is to increase the heat transfer and hence enhance the thermal boundary layer thickness.This is true even in the presence of variable viscosity and the viscous dissipation.Furthermore,the results obtained for heat transfer characteristics with nanoparticles reveal many interesting behaviors that warrant further study on the effects of the "nano-solid-particles".
Ferrohydrodynamic evaluation of rotational viscosity and relaxation in certain ferrofluids.
Patel, Rajesh
2012-07-01
A significant effect of aggregation dynamics for aqueous ferrofluid (AF) and kerosene based ferrofluid (KF) using magnetic field dependent capillary viscosity and magneto-optical relaxation measurements is studied. For better comparison parameters of AF and KF are kept similar. Ferrohydrodynamic equations of chain forming ferrofluids, dilute ferrofluids, and Brownian dynamic simulations are compared. It is observed that the rotational viscosity of AF is larger than that of KF due to field induced aggregates in it and strong dipolar interactions. It is also observed that at Ωτ ~ 0.04 both AF and KF viscosity becomes almost similar, suggesting similar behavior at that shear rate. The magneto-optical relaxation in AF exhibits nonexponential behavior when relaxed from higher magnetic field and follows irreversible thermodynamics, whereas for KF the relaxation is exponential and follows the effective field method. This discrepancy is explained based on aggregation dynamics of magnetic particles. Results are well described by the corresponding theoretical models.
Oosterbroek, M.; Tropper, R.; Mellema, J.
1980-01-01
The dynamic viscosity of a dilute emulsion is calculated for a pure straining motion. The emulsion consists of almost spherical drops of a Newtonian fluid immersed in another Newtonian fluid. The oscillating velocity field of the flow is derived from the Navier-Stokes equation, in which the linear
Jong Won Kim
2016-06-01
Full Text Available Generally, to produce film-type thermoplastic composites with good mechanical properties, high-performance reinforcement films are used. In this case, films used as a matrix are difficult to impregnate into tow due to their high melt viscosity and high molecular weight. To solve the problem, in this paper, three polypropylene (PP films with different melt viscosities were used separately to produce film-type thermoplastic composites. A film with a low melt viscosity was stacked so that tow was impregnated first and a film with a higher melt viscosity was then stacked to produce the composite. Four different composites were produced by regulating the pressure rising time. The thickness, density, fiber volume fraction (Vf, and void content (Vc were analyzed to identify the physical properties and compare them in terms of film stacking types. The thermal properties were identified by using differential scanning calorimetry (DSC and dynamical mechanical thermal analysis (DMTA. The tensile property, flexural property, interlaminar shear strength (ILSS, and scanning electron microscopy (SEM were performed to identify the mechanical properties. For the films with low molecular weight, impregnation could be completed fast but showed low strength. Additionally, the films with high molecular weight completed impregnation slowly but showed high strength. Therefore, appropriate films should be used considering the forming process time and their mechanical properties to produce film-type composites.
Guo, Ning; Guo, Wei; Xu, Changsheng; Du, Yongpeng; Feng, Jicai
2015-06-01
Underwater wet welding is a crucial repair and maintenance technology for nuclear plant. A boric acid environment raises a new challenge for the underwater welding maintenance of nuclear plant. This paper places emphasis on studying the influence of a boric acid environment in nuclear plant on the underwater welding process. Several groups of underwater wet welding experiments have been conducted in boric acid aqueous solution with different concentration (0-35000 ppm). The viscosity of the welding slag and the mechanical properties of welds, such as the hardness, strength, and elongation, have been studied. The results show that with increasing boric acid concentration, the viscosity of the slag decreases first and then increases at a lower temperature (less than 1441 °C). However, when the temperature is above 1480 °C, the differences between the viscosity measurements become less pronounced, and the viscosity tends to a constant value. The hardness and ductility of the joints can be enhanced significantly, and the maximum strength of the weld metal can be reached at 2300 ppm.
Roques-Carmes, Thibault; Mathieu, Vincent; Gigante, Alexandra
2010-04-01
The dynamics of drop spreading of glycerol-water mixtures with and without surfactant on hydrophilic glass surfaces has been investigated. The influence of different factors, such as viscosity, drop volume and non-ionic alkyl (8-16) glucoside (Plantacare) surfactant concentration on the number and the nature of the spreading regimes is systematically investigated. More than 25 spreading experiments have been performed in order to obtain clear trends. The results confirm the existence of several spreading regimes for the duration of an experiment (200 s). For each regime, the radius can be expressed by a power law of the form R=Kt(n). Both n and K are necessary to identify the regime. The experimental data are compared with the analytical predictions of the combined theory of spreading. One of the main results of this study is that the nature of the regimes is strongly affected by the drop volume, the viscosity and the surfactant concentration. This behavior is not predicted by the theory. For drop volume less than or equal to 15 microL, a succession of two different regimes which depend on the viscosity and surfactant concentration are observed in the following order: a molecular-kinetic regime followed by a hydrodynamic regime (for high viscosity in the presence of surfactant) or a hydrodynamic regime and lastly a final asymptotic regime corresponding to a long relaxation time to equilibrium (for high viscosity in absence of surfactant and for low viscosity regardless of the presence of surfactant). The spreading follows quantitatively the predictions of the theory. Our results demonstrate that the theory is still valid for low viscosity liquids and in the presence of surfactant. The contact angle for which the crossover between molecular-kinetic regime and hydrodynamic regime occurs is thoroughly estimated since the theories do not allow the exact calculation of this value. Here for the first time, an empirical power law exponent (n=0.08+/-0.05) is proposed for
Parlak, Z.; Biet, C.; Zauscher, S.
2013-08-01
We describe the physical understanding of a method which differentiates between the frequency shift caused by fluid viscosity and density from that caused by mass adsorption in the resonance of a quartz crystal resonator. This method uses the normalized conductance of the crystal to determine a critical frequency at which the fluid mass and fluid loss compensate each other. Tracking the shift in this critical frequency allows us to determine purely mass adsorption on the crystal. We extended this method to Maxwellian fluids for understanding the mass adsorption in non-Newtonian fluids. We validate our approach by real-time mass adsorption measurements using glycerol and albumin solutions.
Lærke, Helle Nygaard; Arent, Susan; Dalsgaard, Søren
2015-01-01
Two experiments were performed to study the effect of xylanase on ileal extract viscosity, in vivo fiber solubilization and degradation, and apparent ileal digestibility (AID) of fiber constituents, OM, CP, starch, and crude fat in rye and wheat in ileal-cannulated pigs. In Exp. 1, coarse rye...... AID of arabinoxylan by 91% to 107% (P starch and crude fat digestibility of fine wheat with enzyme addition (P ... marker. Ileal effluent was collected for 8 h on d 5 and 7 and pooled for analysis. In Exp. 1, TR reduced intestinal viscosity of pigs fed rye from 9.3 mPa·s in the control diet (NX) to 6.0 mPa·s (P effect. None of the enzymes changed the concentration of total...
P. Geetha
2011-01-01
Full Text Available Problem statement: In this research the researchers studied and made an analysis to the heat and mass transfer characteristics in a viscous fluid over a semi-infinite vertical porous plate by taking into account the variable viscosity, chemical reaction and thermal stratification effects. Approach: The governing partial differential equations were transformed into a set of coupled non-linear ordinary differential equations, which were solved numerically using the R.K. Gill method along with the shooting technique. Results: Numerical results were presented for the distribution of velocity, temperature and concentration profiles within the boundary layer. Conclusion: The effects of different thermo physical parameters like variation in viscosity due to temperature, chemical reaction parameter on the dimensionless velocity, temperature and concentration profiles were examined.
Shear time dependent viscosity of polystyrene-ethylacrylate based shear thickening fluid
Chen, Qian; Xuan, Shouhu; Jiang, Wanquan; Cao, Saisai; Gong, Xinglong
2016-04-01
In this study, the influence of the shear rate and shear time on the transient viscosity of polystyrene-ethylacrylate based shear thickening fluid (STF) is investigated. If the shear rate is stepwise changed, it is found that both the viscosity and critical shear rate are affected by the shear time. Above the critical shear rate, the viscosity of the STF with larger power law exponent (n) increases faster. However, the viscosity tends to decrease when the shear time is long enough. This phenomenon can be responsible for the reversible structure buildup and the break-down process. An effective volume fraction (EVF) mechanism is proposed to analyze the shear time dependent viscosity and it is found that viscosity changes in proportion to EVF. To further clarify the structure evolution, a structural kinetic model is studied because the structural kinetic parameter (λ) could describe the variation in the effective volume fraction. The theoretical results of the structural kinetic model agree well with the experimental results. With this model, the change in viscosity and EVF can be speculated from the variation of λ and then the structure evolution can be better illustrated.
Ronald D. Flack
2000-01-01
Full Text Available The velocity field inside a torque converter pump was studied for two separate effects: variable pump rotational speed and variable oil viscosity. Three-dimensional velocity measurements were taken using a laser velocimeter for both the pump mid- and exit planes. The effect ofvariable pump rotational speed was studied by running the pump at two different speeds and holding speed ratio (pump rotational speed]turbine rotational speed constant. Similarly, the effect of viscosity on the pump flow field was studied by varying the temperature and]or using two different viscosity oils as the working fluid in the pump. Threedimensional velocity vector plots, through-flow contour plots, and secondary flow profiles were obtained for both pump planes and all test conditions. Results showed that torque converter mass flows increased approximately linearly with increasing pump rotational speed (and fixed speed ratio but that the flow was not directly proportional to pump rotational speed. However, mass flows were seen to decrease as the oil viscosity was decreased with a resulting increased Reynolds number; for these conditions the high velocity regions were seen to decrease in size and low velocity regions were seen to increase in size. In the pump mid-plane strong counter-clockwise secondary flows and in the exit plane strong clockwise secondary flows were observed. The vorticities and slip factors were calculated from the experimental results and are presented. The torque core-to-shell and blade-to-blade torque distributions were calculated for both planes. Finally, the flow fields were seen to demonstrate similitude when Reynolds numbers were matched.