Molecular dynamics calculation of shear viscosity for molten salt

International Nuclear Information System (INIS)

Okamoto, Yoshihiro; Yokokawa, Mitsuo; Ogawa, Toru

1993-12-01

A computer program of molecular dynamics simulation has been made to calculate shear viscosity of molten salt. Correlation function for an off-diagonal component of stress tensor can be obtained as the results of calculation. Shear viscosity is calculated by integration of the correlation function based on the Kubo-type formula. Shear viscosities for a molten KCl ranging in temperature from 1047K to 1273K were calculated using the program. Calculation of 10 5 steps (1 step corresponds to 5 x 10 -15 s) was performed for each temperature in the 216 ions system. The obtained results were in good agreement with the reported experimental values. The program has been vectorized to achieve a faster computation in supercomputer. It makes possible to calculate the viscosity using a large number of statistics amounting to several million MD steps. (author)

Correlation of shear and dielectric ion viscosity of dental resins - Influence of composition, temperature and filler content.

Science.gov (United States)

Steinhaus, Johannes; Hausnerova, Berenika; Haenel, Thomas; Selig, Daniela; Duvenbeck, Fabian; Moeginger, Bernhard

2016-07-01

Shear viscosity and ion viscosity of uncured visible light-curing (VLC) resins and resin based composites (RBC) are correlated with respect to the resin composition, temperature and filler content to check where Dielectric Analysis (DEA) investigations of VLC RBC generate similar results as viscosity measurements. Mixtures of bisphenol A glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) as well as the pure resins were investigated and compared with two commercial VLC dental resins and RBCs (VOCO, Arabesk Top and Grandio). Shear viscosity data was obtained using a Haake Mars III, Thermo Scientific. Ion viscosity measurements performed by a dielectric cure analyzer (DEA 231/1 Epsilon with Mini IDEX-Sensor, Netzsch-Gerätebau). Shear viscosity depends reciprocally on the mobility of molecules, whereas the ion viscosity also depends on the ion concentration as it is affected by both ion concentration and mixture viscosity. Except of pure TEGDMA, shear and ion viscosities depend on the resin composition qualitatively in a similar manner. Furthermore, shear and ion viscosities of the commercial VLC dental resins and composites exhibited the same temperature dependency regardless of filler content. Application of typical rheological models (Kitano and Quemada) revealed that ion viscosity measurements can be described with respect to filler contents of up to 30vol.%. Rheological behavior of a VLC RBC can be characterized by DEA under the condition that the ion concentration is kept constant. Both methods address the same physical phenomenon - motion of molecules. The proposed relations allows for calculating the viscosity of any Bis-GMA-TEGDMA mixture on the base of the viscosities of the pure components. This study demonstrated the applicability of DEA investigations of VLC RBCs with respect to quality assurance purposes. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Shear viscosity, cavitation and hydrodynamics at LHC

International Nuclear Information System (INIS)

Bhatt, Jitesh R.; Mishra, Hiranmaya; Sreekanth, V.

2011-01-01

We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.

Conditions of viscosity measurement for detecting irradiated peppers

International Nuclear Information System (INIS)

Hayashi, Toru; Todoriki, Setsuko; Okadome, Hiroshi; Kohyama, Kaoru

1995-01-01

Viscosity of gelatinized suspensions of black and white peppers decreased depending upon dose. The viscosity was influenced by gelatinization and viscosity measurement conditions. The difference between unirradiated pepper and an irradiated one was larger at a higher pH and temperature for gelatinization. A viscosity parameter normalized with the starch content of pepper sample and the viscosity of a 5% suspension of corn starch could get rid of the influence of the conditions for viscosity measurement such as type of viscometer, shear rate and temperature. (author)

Shear viscosity and out of equilibrium dynamics

CERN Document Server

El, Andrej; Xu, Zhe; Greiner, Carsten

2009-01-01

Using the Grad's method we calculate the entropy production and derive a formula for the second order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance the shear tensor and the shear viscosity to entropy density ratio $\\eta/s$ are numerically calculated by an iterative and self-consistent prescription within the second order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with $\\eta/s$ obtained using the Navier-Stokes approximation, the present result is about 20% larger at a QCD coupling $\\alpha_s \\sim 0.3$(with $\\eta/s\\approx 0.18$) and is a factor of 2-3 larger at a small coupling $\\alpha_s \\sim 0.01$. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on $\\eta/s$, except when employing a small $\\alpha_s$. On the other hand, we demonstrate th...

Electrical conductivity and shear viscosity of quark gluon plasma in a quasiparticle model

International Nuclear Information System (INIS)

Srivastava, P.K.; Mohanty, B.

2014-01-01

Relativistic heavy-ion collisions (HIC) have reported the formation of a strongly coupled quark gluon plasma (sQGP). To study the properties of this sQGP is the main focus nowadays. Among these the shear viscosity (η) and electrical conductivity (σ el ) could reflect the transport properties of the medium. By studying the shear viscosity or more specifically shear viscosity to entropy density ratio (η/s), one can understand the nature of interactions among the constituents of the produced medium, it gives a measure of the fluidity. Electrical conductivity represents the linear response of the system to an applied external electric field. The basic question one could ask is that whether the matter created at heavy ion collision experiment is an electrical conductor or an insulator. Recent lattice QCD as well as phenomenological studies have shown that these transport quantities show some kind of minimum in its variation with respect to temperature near the temperature corresponding to the transition from hadronic phase to quark-gluon phase

On the measurement of the relative viscosity of suspensions

International Nuclear Information System (INIS)

Acrivos, A.; Fan, X.; Mauri, R.

1994-01-01

The relative viscosity of a suspension of rigid, noncolloidal particles immersed in a Newtonian fluid was measured in a Couette device and was found to be shear thinning even for values of the solids fraction as low as 20%. Although such behavior was reported previously, no satisfactory explanation appears to have been given thus far. It shall be shown presently, however, that, at least for our systems, this shear-thinning effect was due to a slight mismatch in the densities of the two phases. Moreover, the apparent relative viscosities measured in our apparatus were found to be in excellent agreement with those predicted theoretically using a model, originally proposed by Leighton and Acrivos [Chem. Eng. Sci. 41, 1377--1384 (1986)], to describe viscous resuspension, according to which the measured relative viscosity should depend on the bulk particle concentration and on the dimensionless Shields number A, and should attain its correct value for a well-mixed suspension only as A→∞. The predictions of this model are also in excellent agreement with the measured transient response of the apparent relative viscosity due to a sudden change in the shear rate

Steady flow on to a conveyor belt - Causal viscosity and shear shocks

Science.gov (United States)

Syer, D.; Narayan, Ramesh

1993-01-01

Some hydrodynamical consequences of the adoption of a causal theory of viscosity are explored. Causality is introduced into the theory by letting the coefficient of viscosity go to zero as the flow velocity approaches a designated propagation speed for viscous signals. Consideration is given to a model of viscosity which has a finite propagation speed of shear information, and it is shown that it produces two kinds of shear shock. A 'pure shear shock' corresponds to a transition from a superviscous to a subviscous state with no discontinuity in the velocity. A 'mixed shear shock' has a shear transition occurring at the same location as a normal adiabatic or radiative shock. A generalized version of the Rankine-Hugoniot conditions for mixed shear shocks is derived, and self-consistent numerical solutions to a model 2D problem in which an axisymmetric radially infalling stream encounters a spinning star are presented.

Shear viscosity of the quark-gluon plasma in a kinetic theory approach

International Nuclear Information System (INIS)

Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V.

2014-01-01

One of the main results of heavy ions collision (HIC) at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound η/s=1/4π for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green-Kubo relations give us an exact expression to compute these coefficients. We compute shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigate a system of particles interacting via anisotropic and energy dependent cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. The correct analytic formula for shear viscosity can be used to develop a transport theory with a fixed η/s and have a comparison with physical observables like elliptic flow

Shear viscosity and out of equilibrium dynamics

CERN Document Server

El, Andrej; Xu, Zhe; Greiner, Carsten

2009-01-01

Using Grad’s method, we calculate the entropy production and derive a formula for the second-order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance, the shear tensor and the shear viscosity to entropy density ratio η/s are numerically calculated by an iterative and self-consistent prescription within the second-order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with η/s obtained using the Navier-Stokes approximation, the present result is about 20% larger at a QCD coupling αs ∼ 0.3 (with η/s ≈ 0.18) and is a factor of 2–3 larger at a small coupling αs ∼ 0.01. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on η/s, except when employing a small αs . On the other hand, we demonstrate that for such small αs , the gluon syst...

Ratio of bulk to shear viscosity in a quasigluon plasma: from weak to strong coupling

CERN Document Server

Bluhm, M; Redlich, K

2012-01-01

The ratio of bulk to shear viscosity is expected to exhibit a different behaviour in weakly and in strongly coupled systems. This can be expressed by the dependence of the ratio on the squared sound velocity. In the high temperature QCD plasma at small running coupling, the viscosity ratio is uniquely determined by a quadratic dependence on the conformality measure, whereas in certain strongly coupled and nearly conformal theories this dependence is linear. Employing an effective kinetic theory of quasiparticle excitations with medium-modified dispersion relation, we analyze the ratio of bulk to shear viscosity of the gluon plasma. We show that in this approach the viscosity ratio comprises both dependencies found by means of weak coupling perturbative and strong coupling holographic techniques.

Steady shear viscosity of stirred yoghurts with varying ropiness

NARCIS (Netherlands)

van Marle, M.E.; van Marle, M.E.; van den Ende, Henricus T.M.; de Kruif, C.G.; de Kruif, C.G.; Mellema, J.

1999-01-01

Stirred yogurt was viewed as a concentrated dispersion of aggregates consisting of protein particles. The steady-shear behavior of three types of stirred yogurt with varying ropiness was investigated experimentally. To describe the shear-dependent viscosity, a microrheological model was used which

Shear viscosity coefficient from microscopic models

International Nuclear Information System (INIS)

Muronga, Azwinndini

2004-01-01

The transport coefficient of shear viscosity is studied for a hadron matter through microscopic transport model, the ultrarelativistic 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 π,η,ω,ρ,φ 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 on the energy density. We do not include hadron strings as degrees of freedom so as to maintain detailed balance. Hence we do not get the saturation of temperature but this leads to longer equilibration times

Blood viscosity during coagulation at different shear rates

Science.gov (United States)

Ranucci, Marco; Laddomada, Tommaso; Ranucci, Matteo; Baryshnikova, Ekaterina

2014-01-01

Abstract During the coagulation process, blood changes from a liquid to a solid gel phase. These changes are reflected by changes in blood viscosity; however, blood viscosity at different shear rates (SR) has not been previously explored during the coagulation process. In this study, we investigated the viscosity changes of whole blood in 10 subjects with a normal coagulation profile, using a cone‐on‐plate viscosimeter. For each subject, three consecutive measurements were performed, at a SR of 20, 40, 80 sec−1. On the basis of the time‐dependent changes in blood viscosity, we identified the gel point (GP), the time‐to‐gel point (TGP), the maximum clot viscosity (MCV), and the clot lysis half‐time (CLH). The TGP significantly (P = 0.0023) shortened for increasing SR, and was significantly associated with the activated partial thromboplastin time at a SR of 20 sec−1 (P = 0.038) and 80 sec−1 (P = 0.019). The MCV was significantly lower at a SR of 80 sec−1 versus 40 sec−1 (P = 0.027) and the CLH significantly (P = 0.048) increased for increasing SR. These results demonstrate that measurement of blood viscosity during the coagulation process offers a number of potentially useful parameters. In particular, the association between the TGP and the activated partial thromboplastin time is an expression of the clotting time (intrinsic and common pathway), and its shortening for increasing SR may be interpreted the well‐known activating effects of SR on platelet activation and thrombin generation. Further studies focused on the TGP under conditions of hypo‐ or hypercoagulability are required to confirm its role in the clinical practice. PMID:24994896

Shear viscosity and entropy of a pion gas

Energy Technology Data Exchange (ETDEWEB)

Rose, Jean-Bernard; Oliinychenko, Dmytro; Schaefer, Anna; Petersen, Hannah [FIAS, Goethe University, Frankfurt (Germany)

2016-07-01

A model of microscopic non-equilibrium dynamics for classical point particles is used to calculate the transport coefficients of dense hadronic matter. Specifically, the shear viscosity to entropy density ratio is investigated, and the temperature dependence between 100 MeV and 300 MeV is explored. Calculations are made at corresponding particle densities going from 0.01 to 0.34 in a pion box simulating infinite matter. The results for the entropy and shear viscosity are then compared to analytic estimates. In addition, massless particles as well as ρ-meson resonance excitations are included. This will be the starting point for the calculation of more transport coefficients as functions of T and μ{sub B}; expanding systems could also be considered.

Bulk and shear viscosities of the gluon plasma in a quasiparticle description

CERN Document Server

Bluhm, M; Redlich, K

2011-01-01

Bulk and shear viscosities of deconfined gluonic matter are investigated within an effective kinetic theory by describing the strongly interacting medium phenomenologically in terms of quasiparticle excitations with medium-dependent self-energies. In this approach, local conservation of energy and momentum follows from a Boltzmann-Vlasov type kinetic equation and guarantees thermodynamic self-consistency. We show that the resulting transport coefficients reproduce the parametric dependencies on temperature and coupling obtained in perturbative QCD at large temperatures and small running coupling. The extrapolation into the non-perturbative regime results in a decreasing specific shear viscosity with decreasing temperature, exhibiting a minimum in the vicinity of the deconfinement transition temperature, while the specific bulk viscosity is sizeable in this region falling off rapidly with increasing temperature. The temperature dependence of specific bulk and shear viscosities found within this quasiparticle d...

Shear viscosity and out of equilibrium dynamics

International Nuclear Information System (INIS)

El, Andrej; Xu Zhe; Greiner, Carsten; Muronga, Azwinndini

2009-01-01

Using Grad's method, we calculate the entropy production and derive a formula for the second-order shear viscosity coefficient in a one-dimensionally expanding particle system, which can also be considered out of chemical equilibrium. For a one-dimensional expansion of gluon matter with Bjorken boost invariance, the shear tensor and the shear viscosity to entropy density ratio η/s are numerically calculated by an iterative and self-consistent prescription within the second-order Israel-Stewart hydrodynamics and by a microscopic parton cascade transport theory. Compared with η/s obtained using the Navier-Stokes approximation, the present result is about 20% larger at a QCD coupling α s ∼0.3 (with η/s≅0.18) and is a factor of 2-3 larger at a small coupling α s ∼0.01. We demonstrate an agreement between the viscous hydrodynamic calculations and the microscopic transport results on η/s, except when employing a small α s . On the other hand, we demonstrate that for such small α s , the gluon system is far from kinetic and chemical equilibrium, which indicates the break down of second-order hydrodynamics because of the strong nonequilibrium evolution. In addition, for large α s (0.3-0.6), the Israel-Stewart hydrodynamics formally breaks down at large momentum p T > or approx. 3 GeV but is still a reasonably good approximation.

Viscosity, granular-temperature, and stress calculations for shearing assemblies of inelastic, frictional disks

International Nuclear Information System (INIS)

Walton, O.R.; Braun, R.L.

1986-01-01

Employing nonequilibrium molecular-dynamics methods the effects of two energy loss mechanisms on viscosity, stress, and granular-temperature in assemblies of nearly rigid, inelastic frictional disks undergoing steady-state shearing are calculated. Energy introduced into the system through forced shearing is dissipated by inelastic normal forces or through frictional sliding during collisions resulting in a natural steady-state kinetic energy density (granular-temperature) that depends on the density and shear rate of the assembly and on the friction and inelasticity properties of the disks. The calculations show that both the mean deviatoric particle velocity and the effective viscosity of a system of particles with fixed friction and restitution coefficients increase almost linearly with strain rate. Particles with a velocity-dependent coefficient of restitution show a less rapid increase in both deviatoric velocity and viscosity as strain rate increases. Particles with highly dissipative interactions result in anisotropic pressure and velocity distributions in the assembly, particularly at low densities. At very high densities the pressure also becomes anisotropic due to high contact forces perpendicular to the shearing direction. The mean rotational velocity of the frictional disks is nearly equal to one-half the shear rate. The calculated ratio of shear stress to normal stress varies significantly with density while the ratio of shear stress to total pressure shows much less variation. The inclusion of surface friction (and thus particle rotation) decreases shear stress at low density but increases shear stress under steady shearing at higher densities

Empirical Modelling of Nonmonotonous Behaviour of Shear Viscosity

Czech Academy of Sciences Publication Activity Database

David, Jiří; Filip, Petr; Kharlamov, Alexander

2013-01-01

Roč. 2013, August (2013) ISSN 1687-6822 R&D Projects: GA ČR GA103/09/2066 Institutional support: RVO:67985874 Keywords : shear viscosity * Galindo-rosales * Carreau-yasuda Subject RIV: BK - Fluid Dynamics Impact factor: 0.500, year: 2012 http://www.hindawi.com/journals/amse/2013/658187/

Study on viscosity of conventional and polymer modified asphalt binders in steady and dynamic shear domain

Science.gov (United States)

Saboo, Nikhil; Singh, Bhupendra; Kumar, Praveen; Vikram, Durgesh

2018-02-01

This study focuses on evaluating the flow behavior of conventional and polymer modified asphalt binders in steady- and dynamic-shear domain, for a temperature range of 20-70 °C, using a Dynamic Shear Rheometer (DSR). Steady-shear viscosity and frequency sweep tests were carried out on two conventional (VG 10 and VG 30) and two polymer (SBS and EVA) modified asphalt binders. Applicability of the Cox-Merz principle was evaluated and complex viscosity master curves were analyzed at five different reference temperatures. Cross model was used to simulate the complex viscosity master curves at different temperatures. It was found that asphalt binders exhibited shear-thinning behavior at all the test temperatures. The critical shear rate increased with increase in temperature and was found to be lowest for plastomeric modified asphalt binder. The Cox-Merz principle was found to be valid in the zero-shear viscosity (ZSV) domain and deviated at higher frequency/shear rate for all the binders. Results from the study indicated that the ratio of ZSV can be successfully used as shift factors for construction of master curves at different reference temperatures. Cross model was found to be suitable in simulating the complex viscosity master curves at all the test temperatures. Analysis of model parameters indicated that a strong relationship exists between ZSV and the critical shear rate. ZSV and critical shear rate varied exponentially with temperature. This relationship was used to propose a simple equation for assessing the shift factors for construction of master curves.

A microscopic calculation of the fourth-rank shear viscosity tensors of superfluid phases of 3He

International Nuclear Information System (INIS)

Shahzamanian, M.A.

1988-01-01

The fourth-rank shear viscosity tensor of the superfluid phases of 3 He is obtained by using the Kubo formula approach. The viscosity coefficients of 3 He-A, and shear viscosity of 3 He-B are calculated with two different relaxation time approximations. The results for the temperature- and energy-independent relaxation times are in agreement with existing experimental data. (author)

Shear viscosity and thermal conductivity of nuclear 'pasta'

International Nuclear Information System (INIS)

Horowitz, C. J.; Berry, D. K.

2008-01-01

We calculate the shear viscosity η and thermal conductivity κ of a nuclear pasta phase in neutron star crusts. This involves complex nonspherical shapes. We use semiclassical molecular dynamics simulations involving 40, 000 to 100, 000 nucleons. The viscosity η can be simply expressed in terms of the height Z* and width Δq of the peak in the static structure factor S p (q). We find that η increases somewhat, compared to a lower density phase involving spherical nuclei, because Z* decreases from form factor and ion screening effects. However, we do not find a dramatic increase in η from nonspherical shapes, as may occur in conventional complex fluids

Kubo formulas for the shear and bulk viscosity relaxation times and the scalar field theory shear τπ calculation

Science.gov (United States)

Czajka, Alina; Jeon, Sangyong

2017-06-01

In this paper we provide a quantum field theoretical study on the shear and bulk relaxation times. First, we find Kubo formulas for the shear and the bulk relaxation times, respectively. They are found by examining response functions of the stress-energy tensor. We use general properties of correlation functions and the gravitational Ward identity to parametrize analytical structures of the Green functions describing both sound and diffusion mode. We find that the hydrodynamic limits of the real parts of the respective energy-momentum tensor correlation functions provide us with the method of computing both the shear and bulk viscosity relaxation times. Next, we calculate the shear viscosity relaxation time using the diagrammatic approach in the Keldysh basis for the massless λ ϕ4 theory. We derive a respective integral equation which enables us to compute η τπ and then we extract the shear relaxation time. The relaxation time is shown to be inversely related to the thermal width as it should be.

The effect of viscosity on the resistive tearing mode with the presence of shear flow

International Nuclear Information System (INIS)

Chen, X.L.; Morrison, P.J.

1990-01-01

The effect of small isotropic viscosity on the ''constant ψ'' tearing mode in the presence of shear flow, is analyzed by the boundary layer approach. It is found that the influence of viscosity depends upon the parameter (G'(0)/F'(0)), where G'(0) and F'(0) denote that shear and magnetic field shear at the magnetic null plane, respectively. When |(G'(0)/F'(0))| much-lt 1, the tearing mode growth rate is suppressed by the viscosity, but not completely stabilized. When |(G'(0)/F'(0))| ∼ in the order of (1) and the viscosity is comparable with the resistivity, the growth rate vanishes as ((1 - G'(0) 2 /F'(0) 2 ) 1/3 ), when G'(0) 2 → F'(0) 2 from below. In the case where (1 - G'(0) 2 /F'(0) 2 ) < 0 matching cannot be achieved. 8 refs

Wave anisotropy of shear viscosity and elasticity

Science.gov (United States)

Rudenko, O. V.; Sarvazyan, A. P.

2014-11-01

The paper presents the theory of shear wave propagation in a "soft solid" material possessing anisotropy of elastic and dissipative properties. The theory is developed mainly for understanding the nature of the low-frequency acoustic characteristics of skeletal muscles, which carry important diagnostic information on the functional state of muscles and their pathologies. It is shown that the shear elasticity of muscles is determined by two independent moduli. The dissipative properties are determined by the fourth-rank viscosity tensor, which also has two independent components. The propagation velocity and attenuation of shear waves in muscle depend on the relative orientation of three vectors: the wave vector, the polarization vector, and the direction of muscle fiber. For one of the many experiments where attention was distinctly focused on the vector character of the wave process, it was possible to make a comparison with the theory, estimate the elasticity moduli, and obtain agreement with the angular dependence of the wave propagation velocity predicted by the theory.

Sensor for viscosity and shear strength measurement

Energy Technology Data Exchange (ETDEWEB)

Ebadian, M.A.; Dillion, J.; Moore, J.; Jones, K.

1998-01-01

Measurement of the physical properties (viscosity and density) of waste slurries is critical in evaluating transport parameters to ensure turbulent flow through transport pipes. The environment for measurement and sensor exposure is extremely harsh; therefore, reliability and ruggedness are critical in the sensor design. Two different viscometer techniques are being investigated in this study, based on: magnetostrictive pulse generated acoustic waves; and an oscillating cylinder. Prototype sensors have been built and tested which are based on both techniques. A base capability instrumentation system has been designed, constructed, and tested which incorporates both of these sensors. It requires manual data acquisition and off-line calculation. A broad range of viscous media has been tested using this system. Extensive test results appear in this report. The concept for each technique has been validated by these test results. This base capability system will need to be refined further before it is appropriate for field tests. The mass of the oscillating system structure will need to be reduced. A robust acoustic probe assembly will need to be developed. In addition, in March 1997 it was made known for the first time that the requirement was for a deliverable automated viscosity instrumentation system. Since then such a system has been designed, and the hardware has been constructed so that the automated concept can be proved. The rest of the hardware, which interfaced to a computer, has also been constructed and tested as far as possible. However, for both techniques the computer software for automated data acquisition, calculation, and logging had not been completed before funding and time ran out.

The shear viscosity of the non-commutative plasma

International Nuclear Information System (INIS)

Landsteiner, Karl; Mas, Javier

2007-01-01

We compute the shear viscosity of the non-commutative N = 4 super Yang-Mills quantum field theory at strong coupling using the dual supergravity background. Special interest derives from the fact that the background presents an intrinsic anisotropy in space through the distinction of commutative and non-commutative directions. Despite this anisotropy the analysis exhibits the ubiquitous result η/s = 1/4π for two different shear channels. In order to derive this result, we show that the boundary energy momentum tensor must couple to the open string metric. As a byproduct we compute the renormalised holographic energy momentum tensor and show that it coincides with one in the commutative theory

Shear viscosity and spin-diffusion coefficient of a two-dimensional Fermi gas

DEFF Research Database (Denmark)

Bruun, Georg

2012-01-01

Using kinetic theory, we calculate the shear viscosity and the spin-diffusion coefficient as well as the associated relaxation times for a two-component Fermi gas in two dimensions, as a function of temperature, coupling strength, polarization, and mass ratio of the two components. It is demonstr......Using kinetic theory, we calculate the shear viscosity and the spin-diffusion coefficient as well as the associated relaxation times for a two-component Fermi gas in two dimensions, as a function of temperature, coupling strength, polarization, and mass ratio of the two components....... It is demonstrated that the minimum value of the viscosity decreases with the mass ratio, since Fermi blocking becomes less efficient. We furthermore analyze recent experimental results for the quadrupole mode of a two-dimensional gas in terms of viscous damping, obtaining a qualitative agreement using no fitting...

Composition and Temperature Dependence of Shear Viscosity of Hydrocarbon Mixtures

Science.gov (United States)

1980-07-01

HNN- XTHDCPD Binary System IX. VTF Eq. Parameters for Shear Viscosities Using Constant B Parameter X. Results of Fits to Master Viscosity Eqs. (43...T(K) for 5 C10 Hydrocarbons I Fig. 2a. log n versus 103/T(K) for HNNi I Fig. 2b. log n versus 103/T(K) for XTHDCPD Fig. 3. Isothem of log n versus X...CD for CO-MO Binary System Fig. 4. Isotherm of log n versus XNBC for NBC-DMO Binary System ( ~Fig. 5. Isotherm of log n versus XfINN for HNN- XTHDCPD

The shear viscosity of a trapped Bose-condensed gas

International Nuclear Information System (INIS)

Shahzamanian, M.A.; Yavary, H.

2006-01-01

By obtaining Kubo formula type and using nonequilibrium Green's functions, we calculate the shear viscosity of a trapped Bose-condensed gas below and above the Bose-Einstein condensation temperature (T BEC ). The contributions of the interactions between condensate and noncondensate atoms and between noncondensate atoms take into account to the viscous relaxation time, by evaluating second order self-energies in Beliaev approximation

Absolute measurement of the viscosity of classical and quantum fluids by rotating-cylinder viscometers

International Nuclear Information System (INIS)

Donnelly, R.J.; LaMar, M.M.

1987-01-01

We discuss the use of rotating-cylinder viscometers to determine absolute shear viscosities of classical fluids and of helium II in the context of past and current knowledge of the stability and flow of these fluids between concentric cylinders. We identify a problem in measuring the absolute viscosity when the inner cylinder is rotating and the outer cylinder is at rest. We conclude by discussing the design of viscometers for absolute viscosity measurements in helium I and helium II

Shear viscosities from Kubo formalism in a large-Nc Nambu-Jona-Lasinio model

International Nuclear Information System (INIS)

Lang, Robert; Kaiser, Norbert; Weise, Wolfram

2015-01-01

In this work the shear viscosity of strongly interacting matter is calculated within a two-flavor Nambu-Jona-Lasinio model as a function of temperature and chemical potential. The general Kubo formula is applied, incorporating the full Dirac structure of the thermal quark spectral function and avoiding commonly used on-shell approximations. Mesonic fluctuations contributing via Fock diagrams provide the dominant dissipative processes. The resulting ratio η/s (shear viscosity over entropy density) decreases with temperature and chemical potential. Interpolating between our NJL results at low temperatures and hard thermal loop results at high temperatures a minimum slightly above the AdS/CFT benchmark η/s = 1/4τ is obtained. (orig.)

Shear viscosity for dense plasmas by equilibrium molecular dynamics in asymmetric Yukawa ionic mixtures

Science.gov (United States)

Haxhimali, Tomorr; Rudd, Robert E.; Cabot, William H.; Graziani, Frank R.

2015-11-01

We present molecular dynamics (MD) calculations of shear viscosity for asymmetric mixed plasma for thermodynamic conditions relevant to astrophysical and inertial confinement fusion plasmas. Specifically, we consider mixtures of deuterium and argon at temperatures of 100-500 eV and a number density of 1025 ions/cc. The motion of 30 000-120 000 ions is simulated in which the ions interact via the Yukawa (screened Coulomb) potential. The electric field of the electrons is included in this effective interaction; the electrons are not simulated explicitly. Shear viscosity is calculated using the Green-Kubo approach with an integral of the shear stress autocorrelation function, a quantity calculated in the equilibrium MD simulations. We systematically study different mixtures through a series of simulations with increasing fraction of the minority high-Z element (Ar) in the D-Ar plasma mixture. In the more weakly coupled plasmas, at 500 eV and low Ar fractions, results from MD compare very well with Chapman-Enskog kinetic results. In the more strongly coupled plasmas, the kinetic theory does not agree well with the MD results. We develop a simple model that interpolates between classical kinetic theories at weak coupling and the Murillo Yukawa viscosity model at higher coupling. This hybrid kinetics-MD viscosity model agrees well with the MD results over the conditions simulated, ranging from moderately weakly coupled to moderately strongly coupled asymmetric plasma mixtures.

Low Rm magnetohydrodynamics as a means of measuring the surface shear viscosity of a liquid metal: A first attempt on Galinstan

Science.gov (United States)

Delacroix, Jules; Davoust, Laurent; Patouillet, Kévin

2018-01-01

This paper introduces an experimental apparatus which generates the end-driven annular flow of a liquid metal pervaded by a uniform magnetic field. Unlike past viscometers involving an annular channel with particular values of the depth-to-width ratio, the present experiment enables us to drive the viscous shear at the surface of an annular liquid metal bath put in rotation. The magnetic interaction parameter N and the Boussinesq number related to the surface shear viscosity can be monitored from the magnitude of the applied magnetic field; the latter being set large enough for avoiding artefacts related to centrifugation and surface dilatation. This essential feature is obtained due to the ability of the magnetic field to set dimensionality of the annular flow in the channel between 2D-1/2 (swirling flow) and 2D axisymmetric (extinction of the overturning flow if N is large enough). By tracking the azimuthal velocity of tracers seeded along the oxidised surface of liquid Galinstan, an estimate for the surface shear viscosity of a liquid metal can be given.

Modified free volume theory of self-diffusion and molecular theory of shear viscosity of liquid carbon dioxide.

Science.gov (United States)

Nasrabad, Afshin Eskandari; Laghaei, Rozita; Eu, Byung Chan

2005-04-28

In previous work on the density fluctuation theory of transport coefficients of liquids, it was necessary to use empirical self-diffusion coefficients to calculate the transport coefficients (e.g., shear viscosity of carbon dioxide). In this work, the necessity of empirical input of the self-diffusion coefficients in the calculation of shear viscosity is removed, and the theory is thus made a self-contained molecular theory of transport coefficients of liquids, albeit it contains an empirical parameter in the subcritical regime. The required self-diffusion coefficients of liquid carbon dioxide are calculated by using the modified free volume theory for which the generic van der Waals equation of state and Monte Carlo simulations are combined to accurately compute the mean free volume by means of statistical mechanics. They have been computed as a function of density along four different isotherms and isobars. A Lennard-Jones site-site interaction potential was used to model the molecular carbon dioxide interaction. The density and temperature dependence of the theoretical self-diffusion coefficients are shown to be in excellent agreement with experimental data when the minimum critical free volume is identified with the molecular volume. The self-diffusion coefficients thus computed are then used to compute the density and temperature dependence of the shear viscosity of liquid carbon dioxide by employing the density fluctuation theory formula for shear viscosity as reported in an earlier paper (J. Chem. Phys. 2000, 112, 7118). The theoretical shear viscosity is shown to be robust and yields excellent density and temperature dependence for carbon dioxide. The pair correlation function appearing in the theory has been computed by Monte Carlo simulations.

Shear Viscosity of Hot QED at Finite Chemical Potential from Kubo Formula

International Nuclear Information System (INIS)

Liu Hui; Hou Defu; Li Jiarong

2008-01-01

Within the framework of finite temperature feld theory this paper discusses the shear viscosity of hot QED plasma through Kubo formula at one-loop skeleton diagram level with a finite chemical potential. The effective widths (damping rates) are introduced to regulate the pinch singularities and then gives a reliable estimation of the shear viscous coefficient. The finite chemical potential contributes positively compared to the pure temperature case. The result agrees with that from the kinetics theory qualitatively

Study of shear viscosity of SU(2)-gluodynamics within lattice simulation

Energy Technology Data Exchange (ETDEWEB)

Astrakhantsev, N.Yu. [Institute for Theoretical and Experimental Physics,Moscow, 117218 (Russian Federation); Moscow Institute of Physics and Technology,Dolgoprudny, 141700 (Russian Federation); Braguta, V.V. [Institute for Theoretical and Experimental Physics,Moscow, 117218 (Russian Federation); Institute for High Energy Physics NRC “Kurchatov Institute”,Protvino, 142281 Russian Federation (Russian Federation); Far Eastern Federal University, School of Biomedicine,Vladivostok, 690950 (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute),Kashirskoe highway, 31, Moscow, 115409 (Russian Federation); Kotov, A.Yu. [Institute for Theoretical and Experimental Physics,Moscow, 117218 (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute),Kashirskoe highway, 31, Moscow, 115409 (Russian Federation)

2015-09-14

This paper is devoted to the study of two-point correlation function of the energy-momentum tensor 〈T{sub 12}T{sub 12}〉 for SU(2)-gluodynamics within lattice simulation of QCD. Using multilevel algorithm we carried out the measurement of the correlation function at the temperature T/T{sub c}≃1.2. It is shown that lattice data can be described by spectral functions which interpolate between hydrodynamics at low frequencies and asymptotic freedom at high frequencies. The results of the study of spectral functions allowed us to estimate the ratio of shear viscosity to the entropy density η/s=0.134±0.057.

A sensitive dynamic viscometer for measuring the complex shear modulus in a steady shear flow using the method of orthogonal superposition

NARCIS (Netherlands)

Zeegers, J.C.H.; Zeegers, Jos; van den Ende, Henricus T.M.; Blom, C.; Altena, E.G.; Beukema, Gerrit J.; Beukema, G.J.; Mellema, J.

1995-01-01

A new instrument to carry out complex viscosity measurements in equilibrium and in a steady shear flow has been developed. A small amplitude harmonic excitation is superimposed orthogonally to the steady shear rate component. It is realized by a thin-walled cylinder, which oscillates in the axial

Shear viscosities from Kubo formalism in a large-Nc Nambu-Jona-Lasinio model

International Nuclear Information System (INIS)

Lang, Robert Friedrich

2015-01-01

The quark-gluon plasma produced in heavy-ion collisions at RHIC and LHC is a hot and dense state of strongly correlated matter. It behaves like an almost-perfect fluid featuring a small ratio of shear viscosity to entropy density. In this thesis we calculate within a two-flavor Nambu-Jona-Lasinio model the shear viscosity as function of temperature and chemical potential. A new Kubo formula is developed, incorporating the full Dirac structure of the quark spectral function and avoiding commonly used on-shell approximations. Mesonic fluctuations occurring at Fock level provide the dominant dissipative process. The resulting parameter-free ratio is an overall decreasing function of temperature and chemical potential. In combination with hard-thermal-loop results we nd this ratio to feature a minimum slightly above the AdS/CFT benchmark.

Systematic errors in transport calculations of shear viscosity using the Green-Kubo formalism

Science.gov (United States)

Rose, J. B.; Torres-Rincon, J. M.; Oliinychenko, D.; Schäfer, A.; Petersen, H.

2018-05-01

The purpose of this study is to provide a reproducible framework in the use of the Green-Kubo formalism to extract transport coefficients. More specifically, in the case of shear viscosity, we investigate the limitations and technical details of fitting the auto-correlation function to a decaying exponential. This fitting procedure is found to be applicable for systems interacting both through constant and energy-dependent cross-sections, although this is only true for sufficiently dilute systems in the latter case. We find that the optimal fit technique consists in simultaneously fixing the intercept of the correlation function and use a fitting interval constrained by the relative error on the correlation function. The formalism is then applied to the full hadron gas, for which we obtain the shear viscosity to entropy ratio.

Shear viscosity from Kubo formalism: NJL model study

International Nuclear Information System (INIS)

Lang, Robert; Weise, Wolfram

2014-01-01

A large-N c expansion is combined with the Kubo formalism to study the shear viscosity η of strongly interacting matter in the two-flavor NJL model. We discuss analytical and numerical approaches to η and investigate systematically its strong dependence on the spectral width and the momentum-space cutoff. Thermal effects on the constituent quark mass from spontaneous chiral symmetry breaking are included. The ratio η/s and its thermal dependence are derived for different parameterizations of the spectral width and for an explicit one-loop calculation including mesonic modes within the NJL model. (orig.)

Use of the McQuarrie equation for the computation of shear viscosity via equilibrium molecular dynamics

International Nuclear Information System (INIS)

Chialvo, A.A.; Debenedetti, P.G.

1991-01-01

To date, the calculation of shear viscosity for soft-core fluids via equilibrium molecular dynamics has been done almost exclusively using the Green-Kubo formalism. The alternative mean-squared displacement approach has not been used, except for hard-sphere fluids, in which case the expression proposed by Helfand [Phys. Rev. 119, 1 (1960)] has invariably been selected. When written in the form given by McQuarrie [Statistical Mechanics (Harper ampersand Row, New York, 1976), Chap. 21], however, the mean-squared displacement approach offers significant computational advantages over both its Green-Kubo and Helfand counterparts. In order to achieve comparable statistical significance, the number of experiments needed when using the Green-Kubo or Helfand formalisms is more than an order of magnitude higher than for the McQuarrie expression. For pairwise-additive systems with zero linear momentum, the McQuarrie method yields frame-independent shear viscosities. The hitherto unexplored McQuarrie implementation of the mean-squared displacement approach to shear-viscosity calculation thus appears superior to alternative methods currently in use

Shear viscosity of the quark-gluon plasma in a weak magnetic field in perturbative QCD: Leading log

Science.gov (United States)

Li, Shiyong; Yee, Ho-Ung

2018-03-01

We compute the shear viscosity of two-flavor QCD plasma in an external magnetic field in perturbative QCD at leading log order, assuming that the magnetic field is weak or soft: e B ˜g4log (1 /g )T2. We work in the assumption that the magnetic field is homogeneous and static, and the electrodynamics is nondynamical in a formal limit e →0 while e B is kept fixed. We show that the shear viscosity takes a form η =η ¯(B ¯)T3/(g4log (1 /g )) with a dimensionless function η ¯(B ¯) in terms of a dimensionless variable B ¯=(e B )/(g4log (1 /g )T2). The variable B ¯ corresponds to the relative strength of the effect of cyclotron motions compared to the QCD collisions: B ¯˜lmfp/lcyclo. We provide a full numerical result for the scaled shear viscosity η ¯(B ¯).

Shear and bulk viscosity of high-temperature gluon plasma

Science.gov (United States)

Zhang, Le; Hou, De-Fu

2018-05-01

We calculate the shear viscosity (η) and bulk viscosity (ζ) to entropy density (s) ratios η/s and ζ/s of a gluon plasma system in kinetic theory, including both the elastic {gg}≤ftrightarrow {gg} forward scattering and the inelastic soft gluon bremsstrahlung {gg}≤ftrightarrow {ggg} processes. Due to the suppressed contribution to η and ζ in the {gg}≤ftrightarrow {gg} forward scattering and the effective g≤ftrightarrow {gg} gluon splitting, Arnold, Moore and Yaffe (AMY) and Arnold, Dogan and Moore (ADM) have got the leading order computations for η and ζ in high-temperature QCD matter. In this paper, we calculate the correction to η and ζ in the soft gluon bremsstrahlung {gg}≤ftrightarrow {ggg} process with an analytic method. We find that the contribution of the collision term from the {gg}≤ftrightarrow {ggg} soft gluon bremsstrahlung process is just a small perturbation to the {gg}≤ftrightarrow {gg} scattering process and that the correction is at ∼5% level. Then, we obtain the bulk viscosity of the gluon plasma for the number-changing process. Furthermore, our leading-order result for bulk viscosity is the formula \\zeta \\propto \\tfrac{{α }s2{T}3}{ln}{α }s-1} in high-temperature gluon plasma. Supported by Ministry of Science and Technology of China (MSTC) under the “973” Project (2015CB856904(4)) and National Natural Science Foundation of China (11735007, 11521064)

Study of shear viscosity for dense plasmas by equilibrium molecular dynamics in asymmetric Yukawa ionic mixtures

Science.gov (United States)

Haxhimali, Tomorr; Rudd, Robert; Cabot, William; Graziani, Frank

2015-11-01

We present molecular dynamics (MD) calculations of shear viscosity for asymmetric mixed plasma for thermodynamic conditions relevant to astrophysical and Inertial Confinement Fusion plasmas. Specifically, we consider mixtures of deuterium and argon at temperatures of 100-500 eV and a number density of 1025 ions/cc. The motion of 30000-120000 ions is simulated in which the ions interact via the Yukawa (screened Coulomb) potential. The electric field of the electrons is included in this effective interaction. Shear viscosity is calculated using the Green-Kubo approach with an integral of the shear stress autocorrelation function, a quantity calculated in the equilibrium MD simulations. We study different mixtures with increasing fraction of the minority high-Z element (Ar) in the D-Ar plasma mixture. In the more weakly coupled plasmas, at 500 eV and low Ar fractions, results from MD compare very well with Chapman-Enskog kinetic results. We introduce a model that interpolates between a screened-plasma kinetic theory at weak coupling and the Murillo Yukawa viscosity model at higher coupling. This hybrid kinetics-MD viscosity model agrees well with the MD results over the conditions simulated. This work was performed under the auspices of the US Dept. of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344.

Evaluation of stability and viscosity measurement of emulsion from oil from production in northern oilfield in Thailand

Science.gov (United States)

Juntarasakul, O.; Maneeintr, K.

2018-04-01

Emulsion is normally present in oil due to the mixing occurring during oil recovery. The formation of emulsion can cause some problems in production and transportation. Viscosity and stability of emulsion play a key roles in oil transportation and separation to meet sales specification. Therefore, the aims of this research are to measure the viscosity of oil an emulsion and to evaluate the stability of emulsion of light oil from Fang oilfield in Thailand. The parameters of this study are temperature, shear rate and water cut ranging from 50 to 80 °C, 3.75 to 70 s-1 and 0 to 60%, respectively. These effects of parameters on viscosity and stability of emulsion are required for the design of the process and to increase oil production with various conditions. The results shows that viscosity decreases as temperature and shear rate increase. In contrast, viscosity becomes higher when water cut is lower. Furthermore, droplet sizes of water-in-oil emulsion at different conditions are investigated the stability of emulsion. The droplet sizes become smaller when high shear rate is applied and emulsion becomes more stable. Furthermore, correlations are developed to predict the viscosity and stability of the oil and emulsion from Thailand.

Ab initio calculation of the shear viscosity of neon in the liquid and hypercritical state over a wide pressure and temperature range

Science.gov (United States)

Eggenberger, Rolf; Gerber, Stefan; Huber, Hanspeter; Searles, Debra; Welker, Marc

1992-08-01

The shear viscosity is calculated ab initio for the liquid and hypercritical state, i.e. a previously published potential for Ne 2, obtained from ab initio calculations including electron correlation, is used in classical equilibrium molecular dynamics simulations to obtain the shear viscosity from a Green-Kubo integral. The quality of the results is quite uniform over a large pressure range up to 1000 MPa and a wide temperature range from 26 to 600 K. In most cases the calculated shear viscosity deviates by less than 10% from the experimental value, in general the error being only a few percent.

Numerical investigation on lateral migration and lift force of single bubble in simple shear flow in low viscosity fluid using volume of fluid method

International Nuclear Information System (INIS)

Zhongchun, Li; Xiaoming, Song; Shengyao, Jiang; Jiyang, Yu

2014-01-01

Highlights: • A VOF simulation of bubble in low viscosity fluid was conducted. • Lift force in different viscosity fluid had different lateral migration characteristics. • Bubble with different size migrated to different direction. • Shear stress triggered the bubble deformation process and the bubble deformation came along with the oscillation behaviors. - Abstract: Two phase flow systems have been widely used in industrial engineering. Phase distribution characteristics are vital to the safety operation and optimization design of two phase flow systems. Lift force has been known as perpendicular to the bubbles’ moving direction, which is one of the mechanisms of interfacial momentum transfer. While most widely used lift force correlations, such as the correlation of Tomiyama et al. (2002), were obtained by experimentally tracking single bubble trajectories in high viscosity glycerol–water mixture, the applicability of these models into low viscosity fluid, such as water in nuclear engineering system, needs to be further evaluated. In the present paper, bubble in low viscosity fluid in shear flow was investigated in a full 3D numerical simulation and the volume of fluid (VOF) method was applied to capture the interface. The fluid parameter: fluid viscosity, bubble parameter: diameter and external flow parameters: shear stress magnitude and liquid velocity were examined. Comparing with bubble in high viscosity shear flow and bubble in low viscosity still flow, relative large bubble in low viscosity shear flow keep an oscillation way towards the moving wall and experienced a shape deformation process. The oscillation amplitude increased as the viscosity of fluid decreased. Small bubble migrated to the static wall in a line with larger migration velocity than that in high viscosity fluid and no deformation occurred. The shear stress triggered the oscillation behaviors while it had no direct influence with the behavior. The liquid velocity had no effect on

Shear viscosity of neutron-rich nucleonic matter near its liquid–gas phase transition

International Nuclear Information System (INIS)

Xu, Jun; Chen, Lie-Wen; Ko, Che Ming; Li, Bao-An; Ma, Yu Gang

2013-01-01

Within a relaxation time approach using free nucleon–nucleon cross sections modified by the in-medium nucleon masses that are determined from an isospin- and momentum-dependent effective nucleon–nucleon interaction, we investigate the specific shear viscosity (η/s) of neutron-rich nucleonic matter near its liquid–gas phase transition. It is found that as the nucleonic matter is heated at fixed pressure or compressed at fixed temperature, its specific shear viscosity shows a valley shape in the temperature or density dependence, with the minimum located at the boundary of the phase transition. Moreover, the value of η/s drops suddenly at the first-order liquid–gas phase transition temperature, reaching as low as 4–5 times the KSS bound of ℏ/4π. However, it varies smoothly for the second-order liquid–gas phase transition. Effects of the isospin degree of freedom and the nuclear symmetry energy on the value of η/s are also discussed

Searching for perfect fluids: quantum viscosity in a universal Fermi gas

International Nuclear Information System (INIS)

Cao, C; Elliott, E; Wu, H; Thomas, J E

2011-01-01

We measure the shear viscosity in a two-component Fermi gas of atoms, tuned to a broad s-wave collisional (Feshbach) resonance. At resonance, the atoms strongly interact and exhibit universal behavior, where the equilibrium thermodynamic properties and transport coefficients are universal functions of density n and temperature T. We present a new calibration of the temperature as a function of global energy, which is directly measured from the cloud profiles. Using the calibration, the trap-averaged shear viscosity in units of ℎn is determined as a function of the reduced temperature at the trap center, from nearly the ground state to the unitary two-body regime. Low-temperature data are obtained from the damping rate of the radial breathing mode, whereas high-temperature data are obtained from hydrodynamic expansion measurements. We also show that the best fit to the high-temperature expansion data is obtained for a vanishing bulk viscosity. The measured trap-averaged entropy per particle and shear viscosity are used to estimate the ratio of shear viscosity to entropy density, which is compared with that conjectured for a perfect fluid.

Computing bulk and shear viscosities from simulations of fluids with dissipative and stochastic interactions

Energy Technology Data Exchange (ETDEWEB)

Jung, Gerhard, E-mail: jungge@uni-mainz.de; Schmid, Friederike, E-mail: friederike.schmid@uni-mainz.de [Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 9, D-55099 Mainz (Germany)

2016-05-28

Exact values for bulk and shear viscosity are important to characterize a fluid, and they are a necessary input for a continuum description. Here we present two novel methods to compute bulk viscosities by non-equilibrium molecular dynamics simulations of steady-state systems with periodic boundary conditions — one based on frequent particle displacements and one based on the application of external bulk forces with an inhomogeneous force profile. In equilibrium simulations, viscosities can be determined from the stress tensor fluctuations via Green-Kubo relations; however, the correct incorporation of random and dissipative forces is not obvious. We discuss different expressions proposed in the literature and test them at the example of a dissipative particle dynamics fluid.

Lennard-Jones triple-point bulk and shear viscosities. Green-Kubo theory, Hamiltonian mechanics, and nonequilibrium molecular dynamics

International Nuclear Information System (INIS)

Hoover, W.G.; Evans, D.J.; Hickman, R.B.; Ladd, A.J.C.; Ashurst, W.T.; Moran, B.

1980-01-01

A new Hamiltonian method for deformation simulations is related to the Green-Kubo fluctuation theory through perturbation theory and linear-response theory. Numerical results for the bulk and shear viscosity coefficients are compared to corresponding Green-Kubo calculations. Both viscosity coefficients depend similarly on frequency, in a way consistent with enhanced ''long-time tails.''

Shear thinning and shear thickening of a confined suspension of vesicles

Science.gov (United States)

Nait Ouhra, A.; Farutin, A.; Aouane, O.; Ez-Zahraouy, H.; Benyoussef, A.; Misbah, C.

2018-01-01

Widely regarded as an interesting model system for studying flow properties of blood, vesicles are closed membranes of phospholipids that mimic the cytoplasmic membranes of red blood cells. In this study we analyze the rheology of a suspension of vesicles in a confined geometry: the suspension, bound by two planar rigid walls on each side, is subject to a shear flow. Flow properties are then analyzed as a function of shear rate γ ˙, the concentration of the suspension ϕ , and the viscosity contrast λ =ηin/ηout , where ηin and ηout are the fluid viscosities of the inner and outer fluids, respectively. We find that the apparent (or effective viscosity) of the suspension exhibits both shear thinning (decreasing viscosity with shear rate) or shear thickening (increasing viscosity with shear rate) in the same concentration range. The shear thinning or thickening behaviors appear as subtle phenomena, dependant on viscosity contrast λ . We provide physical arguments on the origins of these behaviors.

Effect of ionic and non-ionic contrast media on whole blood viscosity, plasma viscosity and hematocrit in vitro

International Nuclear Information System (INIS)

Aspelin, P.

1978-01-01

The effect of the ionic contrast media diatrizoate, iocarmate and metrizoate and the non-ionic metrizamide on whole blood viscosity, plasma viscosity and hematocrit was investigated. All the contrast media increased whole blood and plasma viscosity and reduced the hematocrit. The whole blood viscosity increased with increasing osmolality of the contrast medium solutions, whereas the plasma viscosity increased with increasing viscosity of the contrast medium solutions. The higher the osmolality of the contrast media, the lower the hematocrit became. The normal shear-thinning (decreasing viscosity with increasing shear rate) property of blood was reduced when contrast medium was added to the blood. At 50 per cent volume ratio (contrast medium to blood), the ionic contrast media converted the blood into a shear-thickening (increasing viscosity with increasing shear rate) suspension, indicating a marked rigidification of the single red cell, while the non-ionic contrast medium still produced shear-thinning, indicating less rigidification of the red cell (p<0.01). (Auth.)

Measurement of the Surface Dilatational Viscosity of an Insoluble Surfactant Monolayer at the Air/Water Interface Using a Pendant Drop Apparatus

Science.gov (United States)

Lorenzo, Jose; Couzis, Alex; Maldarelli, Charles; Singh, Bhim S. (Technical Monitor)

2000-01-01

When a fluid interface with surfactants is at rest, the interfacial stress is isotropic (as given by the equilibrium interfacial tension), and is described by the equation of state which relates the surface tension to the surfactant surface concentration. When surfactants are subjected to shear and dilatational flows, flow induced interaction of the surfactants; can create interfacial stresses apart from the equilibrium surface tension. The simplest relationship between surface strain rate and surface stress is the Boussinesq-Scriven constitutive equation completely characterized by three coefficients: equilibrium interfacial tension, surface shear viscosity, and surface dilatational viscosity Equilibrium interfacial tension and surface shear viscosity measurements are very well established. On the other hand, surface dilatational viscosity measurements are difficult because a flow which change the surface area also changes the surfactant surface concentration creating changes in the equilibrium interfacial tension that must be also taken into account. Surface dilatational viscosity measurements of existing techniques differ by five orders of magnitude and use spatially damped surface waves and rapidly expanding bubbles. In this presentation we introduce a new technique for measuring the surface dilatational viscosity by contracting an aqueous pendant drop attached to a needle tip and having and insoluble surfactant monolayer at the air-water interface. The isotropic total tension on the surface consists of the equilibrium surface tension and the tension due to the dilation. Compression rates are undertaken slow enough so that bulk hydrodynamic stresses are small compared to the surface tension force. Under these conditions we show that the total tension is uniform along the surface and that the Young-Laplace equation governs the drop shape with the equilibrium surface tension replaced by the constant surface isotropic stress. We illustrate this technique using

Influence Of Specific Mechanical Energy On Cornmeal Viscosity Measured By An On-line System During Twin-screw Extrusion

OpenAIRE

Chang Y.K.; Martinez-Bustos F.; Park T.S.; Kokini J.L.

1999-01-01

The influence of specific mechanical energy (SME) on cornmeal viscosity during the twin-screw extrusion at feed moisture contents of 25 and 30% and screw speeds in the range from 100 to 500 rpm was measured. Cornmeal was extruded in a co-rotating, intermeshing twin-screw coupled to a slit die rheometer. One approach to the on-line rheological measurement is to use a slit die with the extruder. In the present work it was show that shear viscosity decreased as a function of SME. The viscosity o...

Determination of Viscosity-Average Molecular Weight of Chitosan using Intrinsic Viscosity Measurement

International Nuclear Information System (INIS)

Norzita Yacob; Norhashidah Talip; Maznah Mahmud

2011-01-01

Molecular weight of chitosan can be determined by different techniques such as Gel Permeation Chromatography (GPC), Static Light Scattering (SLS) and intrinsic viscosity measurement. Determination of molecular weight by intrinsic viscosity measurement is a simple method for characterization of chitosan. Different concentrations of chitosan were prepared and measurement was done at room temperature. The flow time data was used to calculate the intrinsic viscosity by extrapolating the reduced viscosity to zero concentration. The value of intrinsic viscosity was then recalculated into the viscosity-average molecular weight using Mark-Houwink equation. (author)

Measurement of the temperature-dependent threshold shear-stress of red blood cell aggregation.

Science.gov (United States)

Lim, Hyun-Jung; Nam, Jeong-Hun; Lee, Yong-Jin; Shin, Sehyun

2009-09-01

Red blood cell (RBC) aggregation is becoming an important hemorheological parameter, which typically exhibits temperature dependence. Quite recently, a critical shear-stress was proposed as a new dimensional index to represent the aggregative and disaggregative behaviors of RBCs. The present study investigated the effect of the temperature on the critical shear-stress that is required to keep RBC aggregates dispersed. The critical shear-stress was measured at various temperatures (4, 10, 20, 30, and 37 degrees C) through the use of a transient microfluidic aggregometry. The critical shear-stress significantly increased as the blood temperature lowered, which accorded with the increase in the low-shear blood viscosity with the lowering of the temperature. Furthermore, the critical shear-stress also showed good agreement with the threshold shear-stress, as measured in a rotational Couette flow. These findings assist in rheologically validating the critical shear-stress, as defined in the microfluidic aggregometry.

Shear viscosity to entropy density ratio in nuclear multifragmentation

International Nuclear Information System (INIS)

Pal, Subrata

2010-01-01

Nuclear multifragmentation in intermediate-energy heavy-ion collisions has long been associated with liquid-gas phase transition. We calculate the shear viscosity to entropy density ratio η/s for an equilibrated system of nucleons and fragments produced in multifragmentation within an extended statistical multifragmentation model. The temperature dependence of η/s exhibits behavior surprisingly similar to that of H 2 O. In the coexistence phase of fragments and light particles, the ratio η/s reaches a minimum of depth comparable to that for water in the vicinity of the critical temperature for liquid-gas phase transition. The effects of freeze-out volume and surface symmetry energy on η/s in multifragmentation are studied.

The influence of specific mechanical energy on cornmeal viscosity measured by an on-line system during twin-screw extrusion

OpenAIRE

CHANG, Y. K.; MARTINEZ-BUSTOS, F.; PARK, T. S.; KOKINI, J .L.

1999-01-01

The influence of specific mechanical energy (SME) on cornmeal viscosity during the twin-screw extrusion at feed moisture contents of 25 and 30% and screw speeds in the range from 100 to 500 rpm was measured. Cornmeal was extruded in a co-rotating, intermeshing twin-screw coupled to a slit die rheometer. One approach to the on-line rheological measurement is to use a slit die with the extruder. In the present work it was show that shear viscosity decreased as a function of SME. The viscosity o...

Viscosity measurement in the capillary tube viscometer under unsteady flow

International Nuclear Information System (INIS)

Park, Heung Jun; Yoo, Sang Sin; Suh, Sang Ho

2000-01-01

The objective of the present study is to develop a new device that the viscous characteristics of fluids are determined by applying the unsteady flow concept to the traditional capillary tube viscometer. The capillary tube viscometer consists of a small cylindrical reservoir, capillary tube, a load cell system that measures the mass flow rate, interfaces, and computer. Due to the small size of the reservoir the height of liquid in the reservoir decreases as soon as the liquid in the reservoir drains out through the capillary and the mass flow rate in the capillary decreases as the hydrostatic pressure in the reservoir decreases resulting in a decrease of the shear rate in the capillary tube. The instantaneous shear rate and driving force in the capillary tube are determined by measuring the mass flow rate through the capillary, and the fluid viscosity is determined from the measured flow rate and the driving force

Determination of viscosity-average molecular weight of chitosan using intrinsic viscosity measurement

International Nuclear Information System (INIS)

Norzita Yacob; Norhashidah Talip; Maznah Mahmud; Nurul Aizam Idayu Mat Sani; Nor Akma Samsuddin; Norafifah Ahmad Fabillah

2013-01-01

Determination of molecular weight by intrinsic viscosity measurement is a simple method for characterization of chitosan. To study the effect of radiation on molecular weight, chitosan was first irradiated using electron beam at different doses prior to measurement. Different concentrations of chitosan were prepared and measurement was done at room temperature. The flow time data was used to calculate the intrinsic viscosity by extrapolating the reduced viscosity to zero concentration. The value of intrinsic viscosity was then recalculated into the viscosity-average molecular weight using Mark-Houwink equation. (Author)

Viscosity of aluminum under shock-loading conditions

International Nuclear Information System (INIS)

Ma Xiao-Juan; Liu Fu-Sheng; Zhang Ming-Jian; Sun Yan-Yun

2011-01-01

A reliable data treatment method is critical for viscosity measurements using the disturbance amplitude damping method of shock waves. In this paper the finite difference method is used to obtain the numerical solutions for the disturbance amplitude damping behaviour of the sinusoidal shock front in a flyer-impact experiment. The disturbance amplitude damping curves are used to depict the numerical solutions of viscous flow. By fitting the experimental data to the numerical solutions of different viscosities, we find that the effective shear viscosity coefficients of shocked aluminum at pressures of 42, 78 and 101 GPa are (1500±100) Pa·s, (2800±100) Pa·s and (3500±100) Pa·s respectively. It is clear that the shear viscosity of aluminum increases with an increase in shock pressure, so aluminum does not melt below a shock pressure of 101 GPa. This conclusion is consistent with the sound velocity measurement. (interdisciplinary physics and related areas of science and technology)

Multiscale approach to link red blood cell dynamics, shear viscosity, and ATP release.

Science.gov (United States)

Forsyth, Alison M; Wan, Jiandi; Owrutsky, Philip D; Abkarian, Manouk; Stone, Howard A

2011-07-05

RBCs are known to release ATP, which acts as a signaling molecule to cause dilation of blood vessels. A reduction in the release of ATP from RBCs has been linked to diseases such as type II diabetes and cystic fibrosis. Furthermore, reduced deformation of RBCs has been correlated with myocardial infarction and coronary heart disease. Because ATP release has been linked to cell deformation, we undertook a multiscale approach to understand the links between single RBC dynamics, ATP release, and macroscopic viscosity all at physiological shear rates. Our experimental approach included microfluidics, ATP measurements using a bioluminescent reaction, and rheology. Using microfluidics technology with high-speed imaging, we visualize the deformation and dynamics of single cells, which are known to undergo motions such as tumbling, swinging, tanktreading, and deformation. We report that shear thinning is not due to cellular deformation as previously believed, but rather it is due to the tumbling-to-tanktreading transition. In addition, our results indicate that ATP release is constant at shear stresses below a threshold (3 Pa), whereas above the threshold ATP release is increased and accompanied by large cellular deformations. Finally, performing experiments with well-known inhibitors, we show that the Pannexin 1 hemichannel is the main avenue for ATP release both above and below the threshold, whereas, the cystic fibrosis transmembrane conductance regulator only contributes to deformation-dependent ATP release above the stress threshold.

Comparative evaluation of aqueous humor viscosity.

Science.gov (United States)

Davis, Kyshia; Carter, Renee; Tully, Thomas; Negulescu, Ioan; Storey, Eric

2015-01-01

To evaluate aqueous humor viscosity in the raptor, dog, cat, and horse, with a primary focus on the barred owl (Strix varia). Twenty-six raptors, ten dogs, three cats, and one horse. Animals were euthanized for reasons unrelated to this study. Immediately, after horizontal and vertical corneal dimensions were measured, and anterior chamber paracentesis was performed to quantify anterior chamber volume and obtain aqueous humor samples for viscosity analysis. Dynamic aqueous humor viscosity was measured using a dynamic shear rheometer (AR 1000 TA Instruments, New Castle, DE, USA) at 20 °C. Statistical analysis included descriptive statistics, unpaired t-tests, and Tukey's test to evaluate the mean ± standard deviation for corneal diameter, anterior chamber volume, and aqueous humor viscosity amongst groups and calculation of Spearman's coefficient for correlation analyses. The mean aqueous humor viscosity in the barred owl was 14.1 centipoise (cP) ± 9, cat 4.4 cP ± 0.2, and dog 2.9 cP ± 1.3. The aqueous humor viscosity for the horse was 1 cP. Of the animals evaluated in this study, the raptor aqueous humor was the most viscous. The aqueous humor of the barred owl is significantly more viscous than the dog (P humor viscosity of the raptor, dog, cat, and horse can be successfully determined using a dynamic shear rheometer. © 2014 American College of Veterinary Ophthalmologists.

Uniaxial Elongational viscosity of bidisperse polystyrene melts

DEFF Research Database (Denmark)

Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole

2006-01-01

The startup and steady uniaxial elongational viscosity have been measured for three bidisperse polystyrene (PS) melts, consisting of blends of monodisperse PS with molecular weights of 52 kg/mole or 103 kg/mole and 390 kg/mole. The bidisperse melts have a maximum in the steady elongational...... viscosity, of up to a factor of 7 times the Trouton limit of 3 times the zero-shear viscosity....

Viscosity of high concentration protein formulations of monoclonal antibodies of the IgG1 and IgG4 subclass - Prediction of viscosity through protein-protein interaction measurements

DEFF Research Database (Denmark)

Neergaard, Martin S; Kalonia, Devendra S; Parshad, Henrik

2013-01-01

The purpose of this work was to explore the relation between protein-protein interactions (PPIs) and solution viscosity at high protein concentration using three monoclonal antibodies (mAbs), two of the IgG4 subclass and one of the IgG1 subclass. A range of methods was used to quantify the PPI...... low or high protein concentration determined using DLS. The PPI measurements were correlated with solution viscosity (measured by DLS using polystyrene nanospheres and ultrasonic shear rheology) as a function of pH (4-9) and ionic strength (10, 50 and 150mM). Our measurements showed that the highest...... solution viscosity was observed under conditions with the most negative kD, the highest apparent radius and the lowest net charge. An increase in ionic strength resulted in a change in the nature of the PPI at low pH from repulsive to attractive. In the neutral to alkaline pH region the mAbs behaved...

Determination of liquid viscosity at high pressure by DLS

International Nuclear Information System (INIS)

Fukui, K; Asakuma, Y; Maeda, K

2010-01-01

The movement of particles with a size smaller than few microns is governed by random Brownian motion. This motion causes the fluid to flow around the particles. The force acting upon Brownian particles as well as their velocities are measured by using the dynamic light scattering (DLS) technique. It provides the relationship between fluid shear stress and shear rate over the Brownian particle and determines the viscosity properties of the fluid. In this study, we propose a new rheometer which is widely applicable to fluid viscosity measurements at both normal and high pressure levels for Newtonian and non- Newtonian fluids.

Shear viscosity and imperfect fluidity in bosonic and fermionic superfluids

Science.gov (United States)

Boyack, Rufus; Guo, Hao; Levin, K.

2014-12-01

In this paper we address the ratio of the shear viscosity to entropy density η /s in bosonic and fermionic superfluids. A small η /s is associated with nearly perfect fluidity, and more general measures of the fluidity perfection/imperfection are of wide interest to a number of communities. We use a Kubo approach to concretely address this ratio via low-temperature transport associated with the quasiparticles. Our analysis for bosonic superfluids utilizes the framework of the one-loop Bogoliubov approximation, whereas for fermionic superfluids we apply BCS theory and its BCS-BEC extension. Interestingly, we find that the transport properties of strict BCS and Bogoliubov superfluids have very similar structures, albeit with different quasiparticle dispersion relations. While there is a dramatic contrast between the power law and exponential temperature dependence for η alone, the ratio η /s for both systems is more similar. Specifically, we find the same linear dependence (on the ratio of temperature T to inverse lifetime γ (T ) ) with η /s ∝T /γ (T ) , corresponding to imperfect fluidity. By contrast, near the unitary limit of BCS-BEC superfluids a very different behavior results, which is more consistent with near-perfect fluidity.

Capillary waves with surface viscosity

Science.gov (United States)

Shen, Li; Denner, Fabian; Morgan, Neal; van Wachem, Berend; Dini, Daniele

2017-11-01

Experiments over the last 50 years have suggested a correlation between the surface (shear) viscosity and the stability of a foam or emulsion. With recent techniques allowing more accurate measurements of the elusive surface viscosity, we examine this link theoretically using small-amplitude capillary waves in the presence of the Marangoni effect and surface viscosity modelled via the Boussinesq-Scriven model. The surface viscosity effect is found to contribute a damping effect on the amplitude of the capillary wave with subtle differences to the effect of the convective-diffusive Marangoni transport. The general wave dispersion is augmented to take into account the Marangoni and surface viscosity effects, and a first-order correction to the critical damping wavelength is derived. The authors acknowledge the financial support of the Shell University Technology Centre for fuels and lubricants.

Finite element approximation of flow of fluids with shear-rate- and pressure-dependent viscosity

Czech Academy of Sciences Publication Activity Database

Hirn, A.; Lanzendörfer, Martin; Stebel, Jan

2012-01-01

Roč. 32, č. 4 (2012), s. 1604-1634 ISSN 0272-4979 R&D Projects: GA ČR GA201/09/0917; GA AV ČR IAA100300802; GA MŠk LC06052 Institutional research plan: CEZ:AV0Z10300504; CEZ:AV0Z10190503 Keywords : non-Newtonian fluid * shear-rate- and pressure-dependent viscosity * finite element method * error analysis Subject RIV: BK - Fluid Dynamics Impact factor: 1.326, year: 2012

Viscosity of Heterogeneous Silicate Melts: A Non-Newtonian Model

Science.gov (United States)

Liu, Zhuangzhuang; Blanpain, Bart; Guo, Muxing

2017-12-01

The recently published viscosity data of heterogeneous silicate melts with well-documented structure and experimental conditions are critically re-analyzed and tabulated. By using these data, a non-Newtonian viscosity model incorporating solid fraction, solid shape, and shear rate is proposed on the basis of the power-law equation. This model allows calculating the viscosity of the heterogeneous silicate melts with solid fraction up to 34 vol pct. The error between the calculated and measured data is evaluated to be 32 pct, which is acceptable considering the large error in viscosity measurement of the completely liquid silicate melt.

The effects of geometrical confinement and viscosity ratio on the coalescence of droplet pairs in shear flow

NARCIS (Netherlands)

Bruyn, De P.; Chen, Dongju; Moldenaers, P.; Cardinaels, R.M.

2014-01-01

The effects of geometrical confinement and viscosity ratio on droplet coalescence in shear flow are experimentally investigated by means of a counter rotating parallel plate device, equipped with a microscope. The ratio of droplet diameter to gap spacing is varied between 0.03 and 0.33 to study both

The influence of specific mechanical energy on cornmeal viscosity measured by an on-line system during twin-screw extrusion

Directory of Open Access Journals (Sweden)

Y. K. CHANG

1999-09-01

Full Text Available The influence of specific mechanical energy (SME on cornmeal viscosity during the twin-screw extrusion at feed moisture contents of 25 and 30% and screw speeds in the range from 100 to 500 rpm was measured. Cornmeal was extruded in a co-rotating, intermeshing twin-screw coupled to a slit die rheometer. One approach to the on-line rheological measurement is to use a slit die with the extruder. In the present work it was show that shear viscosity decreased as a function of SME. The viscosity of cornmeal at the exit die was influenced by screw speed, rate of total mass flow, mass temperature inside the extruder and SME. An increase in screw speed resulted in an increase in SME and a decrease in viscosity. A reduction in slit die height and an increase in screw speed and mass temperature led to a remarkable macromolecular degradation of the starch, as evidenced by the decrease in viscosity.

Inverse shear viscosity (fluidity) scaled with melting point properties: Almost 'universal' behaviour of heavier alkalis

International Nuclear Information System (INIS)

Tankeshwar, K.; March, N.H.

1997-07-01

Some numerical considerations relating to the potential of mean force at the melting point of Rb metal are first presented, which argue against the existence of a well defined activation energy for the shear viscosity of this liquid. Therefore, a scaling approach is developed, based on a well established formula for the viscosity η m of sp liquid metals at their melting points T m . This approach is shown to lead to an 'almost' universal plot of scaled fluidity η -1 η m against (T/T m ) 1/2 for the liquid alkali metals, excluding Li. This metal is anomalous because it is a strong scattering liquid, in marked contrast to the other alkali metals. (author). 9 refs, 3 figs, 1 tab

Study of magnetorheological fluids at high shear rates

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaojie; Gordaninejad, Faramarz [University of Nevada, Department of Mechanical Engineering, Reno, NV (United States)

2006-08-15

The tunable rheological properties of magnetorheological (MR) materials at high shear rates are studied using a piston-driven flow-mode-type rheometer. The proposed method provides measurement of the apparent viscosity and yield stress of MR fluids for a shear rate range of 50 to 40,000 s{sup -1}. The rheological properties of a commercial MR fluid, as well as a newly developed MR polymeric gel, and a ferrofluid-based MR fluid are investigated. The results for apparent viscosity and dynamic and static shear stresses under different applied magnetic fields are reported. (orig.)

Longitudinal and bulk viscosities of expanded rubidium

International Nuclear Information System (INIS)

Zaheri, Ali Hossein Mohammad; Srivastava, Sunita; Tankeshwar, K

2003-01-01

First three non-vanishing sum rules for the bulk and longitudinal stress auto-correlation functions have been evaluated for liquid Rb at six thermodynamic states along the liquid-vapour coexistence curve. The Mori memory function formalism and the frequency sum rules have been used to calculate bulk and longitudinal viscosities. The results thus obtained for the ratio of bulk viscosity to shear viscosity have been compared with experimental and other theoretical predictions wherever available. The values of the bulk viscosity have been found to be more than the corresponding values of the shear viscosity for all six thermodynamic states investigated here

Viscosity of particle laden films

Directory of Open Access Journals (Sweden)

Timounay Yousra

2017-01-01

Full Text Available 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.

Viscosity of particle laden films

Science.gov (United States)

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.

Shear viscosity of the Lennard-Jones fluid near the triple point: Green-Kubo results

International Nuclear Information System (INIS)

Erpenbeck, J.J.

1988-01-01

The long-standing disagreement over the shear viscosity coefficient of the Lennard-Jones fluid near the triple point is reexamined through a series of very extensive Monte Carlo molecular-dynamics calculations of this transport coefficient based on the Green-Kubo theory. The stress autocorrelation function is shown to exhibit a slow decay, principally in the kinetic-potential and the potential-potential terms, which is large compared with the kinetic-kinetic long-time tail predicted by simple mode-coupling theory. Nonetheless, the viscosity coefficient, exclusive of any correction for this tail for times greater than are accessible numerically, is found to agree with that of Schoen and Hoheisel (who discounted the existence of such a tail) as well as nonequilibrium molecular-dynamics calculations. The large value of the viscosity coefficient found by Levesque and co-workers for 864 particles is brought into statistical agreement with the present results by a modest, but not unrealistic, increase in its statistical uncertainty. The pressure is found to exhibit an anomalous dependence on the size of the system, but the viscosity as well as the self-diffusion constant appear to be linear in the inverse of the number of particles, within the precision of our calculations. The viscosity coefficient, including a long-time-tail contribution based on the extended mode-coupling theory is (3.796 +- 0.068)σepsilon-c/m)/sup 1/2/ for the Lennard-Jones potential, fitted to a cubic spline, and (3.345 +- 0.068)σepsilon-c/m)/sup 1/2/ for the potential truncated at 2.5σ

Nonperturbative calculation of the shear viscosity in hot $\\phi^{4}$ theory in real time

CERN Document Server

Wang, E; Wang, Enke; Heinz, Ulrich

1999-01-01

Starting from the Kubo formula we calculate the shear viscosity in hot phi**4 theory nonperturbatively by resumming ladders with a real-time version of the Bethe-Salpeter equation at finite temperature. In the weak coupling limit, the generalized Fluctuation-Dissipation Theorem is shown to decouple the Bethe-Salpeter equations for the different real-time components of the 4-point function. The resulting scalar integral equation is identical with the one obtained by Jeon using diagrammatic ``cutting rules'' in the Imaginary Time Formalism.

Elliptic Flow at Finite Shear Viscosity in a Kinetic Approach at RHIC

International Nuclear Information System (INIS)

Greco, V.; Colonna, M.; Di Toro, M.; Ferini, G.

2010-01-01

Within a covariant parton cascade, we discuss the impact of both finite shear viscosity η and freeze-out dynamics on the elliptic flow generated at RHIC. We find that the enhancement of η/s in the cross-over region of the QGP phase transition cannot be neglected in order to extract the information from the QGP phase. We also point out that the elliptic flow v 2 (p T ) for a fluid at η/s∼0.1-0.2 is consistent with the one needed by quark number scaling drawing a nice consistency between the nearly perfect fluid property of QGP and the coalescence process.

On the measurement of magnetic viscosity

Energy Technology Data Exchange (ETDEWEB)

Serletis, C. [Department of Physics, Aristotle University, Thessaloniki 54124 (Greece); Efthimiadis, K.G., E-mail: kge@auth.gr [Department of Physics, Aristotle University, Thessaloniki 54124 (Greece)

2012-08-15

This work is an investigation of the experimental method used for measuring the magnetic viscosity in a hard ferromagnetic material, i.e. the recording of the magnetization under constant applied field and temperature, after the material has been magnetically saturated. It investigates how the experimental results are affected by the initial conditions of the method (saturation field, field change rate and field oscillation prior to its stabilization), and by minor variations of field and temperature during the recording. Based on the arising conclusions and the use of a more complex fitting function of measurements, the accuracy and repeatability of experimental results is improved. - Highlights: Black-Right-Pointing-Pointer Magnetic viscosity is affected by initial measurement conditions. Black-Right-Pointing-Pointer Minor field deviations prior to its stabilization cause large changes in viscosity. Black-Right-Pointing-Pointer Viscosity is strongly dependent on the field change rate from saturation to the measurement field. Black-Right-Pointing-Pointer Small changes in field and temperature during the experiment can lead to false measurements. Black-Right-Pointing-Pointer Errors in measurements can be eliminated through the use of a proper fitting function.

Relationship between the shear viscosity and heating rate in metallic glasses below the glass transition

International Nuclear Information System (INIS)

Khonik, Vitaly A.; Kobelev, N. P.

2008-01-01

It has been shown that first-order irreversible structural relaxation with distributed activation energies must lead to a linear decrease of the logarithm of Newtonian shear viscosity with the logarithm of heating rate upon linear heating of glass. Such a behavior is indeed observed in the experiments on metallic glasses. Structural relaxation-induced viscous flow leads to infra-low-frequency Maxwell viscoelastic internal friction, which is predicted to increase with the heating rate

Gas bubble retention and its effect on waste properties: Retention mechanisms, viscosity, and tensile and shear strengths

International Nuclear Information System (INIS)

Gauglitz, P.A.; Rassat, S.D.; Powell, M.R.

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

Gas bubble retention and its effect on waste properties: Retention mechanisms, viscosity, and tensile and shear strengths

Energy Technology Data Exchange (ETDEWEB)

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 of aqueous and cyanate ester suspensions containing alumina nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Lawler, Katherine [Iowa State Univ., Ames, IA (United States)

2009-01-01

The viscosities of both aqueous and cyanate ester monomer (BECy) based suspensions of alumina nanoparticle were studied. The applications for these suspensions are different: aqueous suspensions of alumina nanoparticles are used in the production of technical ceramics made by slip casting or tape casting, and the BECy based suspensions are being developed for use in an injection-type composite repair resin. In the case of aqueous suspensions, it is advantageous to achieve a high solids content with low viscosity in order to produce a high quality product. The addition of a dispersant is useful so that higher solids content suspensions can be used with lower viscosities. For BECy suspensions, the addition of nanoparticles to the BECy resin is expected to enhance the mechanical properties of the cured composite. The addition of saccharides to aqueous suspensions leads to viscosity reduction. Through DSC measurements it was found that the saccharide molecules formed a solution with water and this resulted in lowering the melting temperature of the free water according to classic freezing point depression. Saccharides also lowered the melting temperature of the bound water, but this followed a different rule. The shear thinning and melting behaviors of the suspensions were used to develop a model based on fractal-type agglomeration. It is believed that the structure of the particle flocs in these suspensions changes with the addition of saccharides which leads to the resultant viscosity decrease. The viscosity of the BECy suspensions increased with solids content, and the viscosity increase was greater than predicted by the classical Einstein equation for dilute suspensions. Instead, the Mooney equation fits the viscosity behavior well from 0-20 vol% solids. The viscosity reduction achieved at high particle loadings by the addition of benzoic acid was also investigated by NMR. It appears that the benzoic acid interacts with the surface of the alumina particle which may

Viscosity of saturated helium-3-helium-4 mixture below 200 mK

NARCIS (Netherlands)

Zeegers, J.C.H.; Waele, de A.T.A.M.; Gijsman, H.M.

1991-01-01

The shear viscosity of saturated3He-4He mixture has been measured at temperatures between 7 mK and 200 mK using a vibrating-wire viscometer and a calibrated pressure cell. The reliability of the vibrating-wire technique was tested by measuring the viscosity of pure4He. The results are internally

Effects of oxygenation and the stress hormones adrenaline and cortisol on the viscosity of blood from the trout oncorhynchus mykiss

DEFF Research Database (Denmark)

Sørensen, Bodil; Weber, Roy

1995-01-01

Although the concentrations of the stress hormones adrenaline and cortisol in rainbow trout (Oncorhynchus mykiss) blood increase upon hypoxic exposure, the combined effects of these hormones and O2 lack upon fish blood rheology have not been investigated. Deoxygenated blood taken by caudal puncture...... exhibited lower viscosities than oxygenated samples at low shear rates, whereas the opposite was true at high shear rates. However, blood from cannulated trout had similar viscosities in its deoxygenated and oxygenated states. In the deoxygenated state, addition of adrenaline lowered viscosity at low shear...... rates and increased it at high shear rates, resembling the effects of deoxygenation observed in blood taken by venepuncture. In oxygenated blood on the contrary, no marked adrenaline effects were observed. In deoxygenated blood, addition of cortisol lowered viscosity at all measured shear rates compared...

Effect of renal replacement therapy on viscosity in end-stage renal disease patients.

Science.gov (United States)

Feriani, M; Kimmel, P L; Kurantsin-Mills, J; Bosch, J P

1992-02-01

Viscosity, an important determinant of microcirculatory hemodynamics, is related to hematocrit (HCT), and may be altered by renal failure or its treatment. To assess these factors, we studied the effect of dialysis on the viscosity of whole blood, plasma, and reconstituted 70% HCT blood of eight continuous ambulatory peritoneal dialysis (CAPD) and nine hemodialysis (HD) patients under steady shear flow conditions at different shear rates, before and after dialysis, compared with nine normal subjects. The density of the red blood cells (RBCs), a marker of cell hydration, was measured in HD patients by a nonaqueous differential floatation technique. Whole blood viscosity was higher in controls than patients, and correlated with HCT before treatment (P less than 0.05) at shear rates of 11.5 to 230 s-1) in HD patients, and 23 to 230 s-1 in all end-stage renal disease (ESRD) patients. In contrast, whole blood viscosity correlated with HCT in CAPD patients only at the lowest shear rates (2.3 and 5.75 s-1, P less than 0.05). Plasma viscosity was higher in CAPD patients than both HD patients before treatment and controls (P less than 0.05, analysis of variance [ANOVA]), despite lower plasma total protein, albumin, and similar fibrinogen concentration compared with HD patients. When all samples were reconstituted to 70% HCT, CAPD patients had higher whole blood viscosity than control subjects'. The high HCT blood viscosity of the ESRD patients was higher than control subjects' at capillary shear rates, suggesting increased RBC aggregation and decreased RBC deformability in patients with renal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Temperature dependence of bulk viscosity in water using acoustic spectroscopy

International Nuclear Information System (INIS)

Holmes, M J; Parker, N G; Povey, M J W

2011-01-01

Despite its fundamental role in the dynamics of compressible fluids, bulk viscosity has received little experimental attention and there remains a paucity of measured data. Acoustic spectroscopy provides a robust and accurate approach to measuring this parameter. Working from the Navier-Stokes model of a compressible fluid one can show that the bulk viscosity makes a significant and measurable contribution to the frequency-squared acoustic attenuation. Here we employ this methodology to determine the bulk viscosity of Millipore water over a temperature range of 7 to 50 0 C. The measured attenuation spectra are consistent with the theoretical predictions, while the bulk viscosity of water is found to be approximately three times larger than its shear counterpart, reinforcing its significance in acoustic propagation. Moreover, our results demonstrate that this technique can be readily and generally applied to fluids to accurately determine their temperature dependent bulk viscosities.

Empirical Modeling of the Viscosity of Supercritical Carbon Dioxide Foam Fracturing Fluid under Different Downhole Conditions

Directory of Open Access Journals (Sweden)

Shehzad Ahmed

2018-03-01

Full Text Available High-quality supercritical CO2 (sCO2 foam as a fracturing fluid is considered ideal for fracturing shale gas reservoirs. The apparent viscosity of the fracturing fluid holds an important role and governs the efficiency of the fracturing process. In this study, the viscosity of sCO2 foam and its empirical correlations are presented as a function of temperature, pressure, and shear rate. A series of experiments were performed to investigate the effect of temperature, pressure, and shear rate on the apparent viscosity of sCO2 foam generated by a widely used mixed surfactant system. An advanced high pressure, high temperature (HPHT foam rheometer was used to measure the apparent viscosity of the foam over a wide range of reservoir temperatures (40–120 °C, pressures (1000–2500 psi, and shear rates (10–500 s−1. A well-known power law model was modified to accommodate the individual and combined effect of temperature, pressure, and shear rate on the apparent viscosity of the foam. Flow indices of the power law were found to be a function of temperature, pressure, and shear rate. Nonlinear regression was also performed on the foam apparent viscosity data to develop these correlations. The newly developed correlations provide an accurate prediction of the foam’s apparent viscosity under different fracturing conditions. These correlations can be helpful for evaluating foam-fracturing efficiency by incorporating them into a fracturing simulator.

Dynamic viscosity study of barley malt and chicory concentrates

Directory of Open Access Journals (Sweden)

G. O. Magomedov

2016-01-01

Full Text Available The purpose of research is to find optimal conditions for dispersing and subsequent dehydration of liquid food environments in the nozzle spray drying chamber through the study of dynamic changes in viscosity according to temperature, velocities gradients and dry residue content. The objects of study were roasted chicory and malt barley concentrates with dry residue content of 20, 40, 60 and 80%. Research of dynamic viscosity were carried out at the measuring complex based on the rotational viscometer Rheotest II, analog-to-digital converter, module Laurent and a personal computer with a unique software that allows to record in real time (not only on a tape recorder, but also in the form of graphic files the behavior of the viscosity characteristics of concentrates. Registration of changes of dynamic viscosity was carried out at a shear rate gradient from 1,0 с -1 to 27,0 с -1 and the products temperature thermostating : 35, 55, 75˚ C. The research results are presented in the form of graphic dependences of effective viscosity on shear rate and flow curves (dependencies of shear stresses on the velocity gradient, which defined flow regimes, the optimal modes of dispersion concentrates into spray dryer chambers in obtaining of powdered semi-finished products and instanting were found: dry residue content - 40 %, concentrate temperature - 75 ˚C, velocity gradient in the air channel of the nozzle at least 20 c-1

Blood and plasma viscosity in diabetes: possible contribution to late organ complications?

NARCIS (Netherlands)

Schut, N. H.; van Arkel, E. C.; Hardeman, M. R.; Bilo, H. J.; Michels, R. P.; Vreeken, J.

1992-01-01

It has been postulated that an increased whole blood and plasma viscosity contribute to diabetic organ complications. Blood viscosity was measured in 30 controls and four groups of insulin-dependent diabetic patients at three shear rates: 70 sec-1, 0.5 sec-1 and 0.05 sec-1. Results were compared

Technical Note: New methodology for measuring viscosities in small volumes characteristic of environmental chamber particle samples

Directory of Open Access Journals (Sweden)

L. Renbaum-Wolff

2013-01-01

Full Text Available Herein, a method for the determination of viscosities of small sample volumes is introduced, with important implications for the viscosity determination of particle samples from environmental chambers (used to simulate atmospheric conditions. The amount of sample needed is < 1 μl, and the technique is capable of determining viscosities (η ranging between 10⁻³ and 10³ Pascal seconds (Pa s in samples that cover a range of chemical properties and with real-time relative humidity and temperature control; hence, the technique should be well-suited for determining the viscosities, under atmospherically relevant conditions, of particles collected from environmental chambers. In this technique, supermicron particles are first deposited on an inert hydrophobic substrate. Then, insoluble beads (~1 μm in diameter are embedded in the particles. Next, a flow of gas is introduced over the particles, which generates a shear stress on the particle surfaces. The sample responds to this shear stress by generating internal circulations, which are quantified with an optical microscope by monitoring the movement of the beads. The rate of internal circulation is shown to be a function of particle viscosity but independent of the particle material for a wide range of organic and organic-water samples. A calibration curve is constructed from the experimental data that relates the rate of internal circulation to particle viscosity, and this calibration curve is successfully used to predict viscosities in multicomponent organic mixtures.

Effect of Fluid Dynamic Viscosity on the Strength of Chalk

DEFF Research Database (Denmark)

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...... of the chalk decreases with increasing dynamic viscosity. The proposed qualitative explanation is that pressure difference supports and enhances the generation of microscopic shear and tensile failures....

Effects of interactions between powder particle size and binder viscosity on agglomerate growth mechanisms in a high shear mixer.

Science.gov (United States)

Johansen, A; Schaefer, T

2001-01-01

A study was performed in order to elucidate the effects of the interactions between powder particle size and binder viscosity on the mechanisms involved in agglomerate formation and growth. Calcium carbonates having mean particle sizes in the range of 5-214 microm and polyethylene glycols having viscosities in the range of approximately 50-100000 mPas were melt agglomerated in a high shear mixer. Agglomerate growth by nucleation and coalescence was found to dominate when agglomerating small powder particles and binders with a low viscosity. Increasing the binder viscosity increased the formation of agglomerates by immersion of powder particles in the surface of the binder droplets. With a larger powder particle size, an increasing binder viscosity was necessary in order to obtain an agglomerate strength being sufficient to avoid breakage. Due to a low agglomerate strength, a satisfying agglomeration of very large particles (214 microm) could not be obtained, even with very viscous binders. The study demonstrated that the optimum agglomerate growth occurred when the agglomerates were of an intermediate strength causing an intermediate deformability of the agglomerates. In order to produce spherical agglomerates (pellets), a low viscosity binder has to be chosen when agglomerating a powder with a small particle size, and a high viscosity binder must be applied in agglomeration of powders with large particles.

Rôle of contrast media viscosity in altering vessel wall shear stress and relation to the risk of contrast extravasations.

Science.gov (United States)

Sakellariou, Sophia; Li, Wenguang; Paul, Manosh C; Roditi, Giles

2016-12-01

Iodinated contrast media (CM) are the most commonly used injectables in radiology today. A range of different media are commercially available, combining various physical and chemical characteristics (ionic state, osmolality, viscosity) and thus exhibiting distinct in vivo behaviour and safety profiles. In this paper, numerical simulations of blood flow with contrast media were conducted to investigate the effects of contrast viscosity on generated vessel wall shear stress and vessel wall pressure to elucidate any possible relation to extravasations. Five different types of contrast for Iodine fluxes ranging at 1.5-2.2gI/s were modelled through 18G and 20G cannulae placed in an ideal vein at two different orientation angles. Results demonstrate that the least viscous contrast media generate the least maximum wall shear stress as well as the lowest total pressure for the same flow rate. This supports the empirical clinical observations and hypothesis that more viscous contrast media are responsible for a higher percentage of contrast extravasations. In addition, results support the clinical hypothesis that a catheter tip directed obliquely to the vein wall always produces the highest maximum wall shear stress and total pressure due to impingement of the contrast jet on the vessel wall. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Viscosity of confined two-dimensional Yukawa liquids: A nonequilibrium method

International Nuclear Information System (INIS)

Landmann, S.; Kählert, H.; Thomsen, H.; Bonitz, M.

2015-01-01

We present a nonequilibrium method that allows one to determine the viscosity of two-dimensional dust clusters in an isotropic confinement. By applying a tangential external force to the outer parts of the cluster (e.g., with lasers), a sheared velocity profile is created. The decay of the angular velocity towards the center of the confinement potential is determined by a balance between internal (viscosity) and external friction (neutral gas damping). The viscosity can then be calculated from a fit of the measured velocity profile to a solution of the Navier-Stokes equation. Langevin dynamics simulations are used to demonstrate the feasibility of the method. We find good agreement of the measured viscosity with previous results for macroscopic Yukawa plasmas

Reliable Viscosity Calculation from Equilibrium Molecular Dynamics Simulations: A Time Decomposition Method.

Science.gov (United States)

Zhang, Yong; Otani, Akihito; Maginn, Edward J

2015-08-11

Equilibrium molecular dynamics is often used in conjunction with a Green-Kubo integral of the pressure tensor autocorrelation function to compute the shear viscosity of fluids. This approach is computationally expensive and is subject to a large amount of variability because the plateau region of the Green-Kubo integral is difficult to identify unambiguously. Here, we propose a time decomposition approach for computing the shear viscosity using the Green-Kubo formalism. Instead of one long trajectory, multiple independent trajectories are run and the Green-Kubo relation is applied to each trajectory. The averaged running integral as a function of time is fit to a double-exponential function with a weighting function derived from the standard deviation of the running integrals. Such a weighting function minimizes the uncertainty of the estimated shear viscosity and provides an objective means of estimating the viscosity. While the formal Green-Kubo integral requires an integration to infinite time, we suggest an integration cutoff time tcut, which can be determined by the relative values of the running integral and the corresponding standard deviation. This approach for computing the shear viscosity can be easily automated and used in computational screening studies where human judgment and intervention in the data analysis are impractical. The method has been applied to the calculation of the shear viscosity of a relatively low-viscosity liquid, ethanol, and relatively high-viscosity ionic liquid, 1-n-butyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide ([BMIM][Tf2N]), over a range of temperatures. These test cases show that the method is robust and yields reproducible and reliable shear viscosity values.

Rapid viscosity measurements of powdered thermosetting resins

Science.gov (United States)

Price, H. L.; Burks, H. D.; Dalal, S. K.

1978-01-01

A rapid and inexpensive method of obtaining processing-related data on powdered thermosetting resins has been investigated. The method involved viscosity measurements obtained with a small specimen (less than 100 mg) parallel plate plastometer. A data acquisition and reduction system was developed which provided a value of viscosity and strain rate about 12-13 second intervals during a test. The effects of specimen compaction pressure and reduction of adhesion between specimen and parallel plates were examined. The plastometer was used to measure some processing-related viscosity changes of an addition polyimide resin, including changes caused by pre-test heat treatment, test temperature, and strain rate.

Effect of Shear History on Rheology of Time-Dependent Colloidal Silica Gels

Directory of Open Access Journals (Sweden)

Paulo H. S. Santos

2017-11-01

Full Text Available This paper presents a rheological study describing the effects of shear on the flow curves of colloidal gels prepared with different concentrations of fumed silica (4%, 5%, 6%, and 7% and a hydrophobic solvent (Hydrocarbon fuel, JP-8. Viscosity measurements as a function of time were carried out at different shear rates (10, 50, 100, 500, and 1000 s−1, and based on this data, a new structural kinetics model was used to describe the system. Previous work has based the analysis of time dependent fluids on the viscosity of the intact material, i.e., before it is sheared, which is a condition very difficult to achieve when weak gels are tested. The simple action of loading the gel in the rheometer affects its structure and rheology, and the reproducibility of the measurements is thus seriously compromised. Changes in viscosity and viscoelastic properties of the sheared material are indicative of microstructural changes in the gel that need to be accounted for. Therefore, a more realistic method is presented in this work. In addition, microscopical images (Cryo-SEM were obtained to show how the structure of the gel is affected upon application of shear.

Whole-blood viscosity and the insulin-resistance syndrome.

Science.gov (United States)

Høieggen, A; Fossum, E; Moan, A; Enger, E; Kjeldsen, S E

1998-02-01

In a previous study we found that elevated blood viscosity was linked to the insulin resistance syndrome, and we proposed that high blood viscosity may increase insulin resistance. That study was based on calculated viscosity. To determine whether directly measured whole-blood viscosity was related to the insulin-resistance syndrome in the same way as calculated viscosity had been found to be. Healthy young men were examined with the hyperinsulinemic isoglycemic glucose clamp technique, and we related insulin sensitivity (glucose disposal rate) to other metabolic parameters and to blood viscosity. We established a technique for direct measurement of whole-blood viscosity. There were statistically significant negative correlations between glucose disposal rate and whole-blood viscosity at low and high shear rates (r = -0.41, P = 0.007 for both, n = 42). Whole-blood viscosity was correlated positively (n = 15) to serum triglyceride (r = 0.54, P = 0.04) and total cholesterol (r = 0.52, P = 0.05), and negatively with high-density lipoprotein cholesterol (r = -0.53, P = 0.04) concentrations. Insulin sensitivity index was correlated positively to high-density lipoprotein cholesterol (r = 0.54, P = 0.04) and negatively to serum triglyceride (r = -0.69, P = 0.005) and to total cholesterol (r = -0.81, P = 0.0003) concentrations. The present results demonstrate for the first time that there is a negative relationship between directly measured whole-blood viscosity and insulin sensitivity as a part of the insulin-resistance syndrome. Whole-blood viscosity contributes to the total peripheral resistance, and these results support the hypothesis that insulin resistance has a hemodynamic basis.

Evaluation of Heating and Shearing on the Viscoelastic Properties of Calcium Hydroxyapatite Used in Injection Laryngoplasty.

Science.gov (United States)

Mahboubi, Hossein; Mohraz, Ali; Verma, Sunil P

2016-03-01

To compare the viscoelastic properties of calcium hydroxyapatite (CaHA) to carboxymethylcellulose (CMC) injectables used for injection laryngoplasty and determine if they are affected by heating and shearing. Experimental. University laboratory. Vocal fold injection laryngoplasty with CaHA is oftentimes challenging due to the amount of pressure necessary to push the injectate through a needle. Anecdotal techniques, such as heating the product, have been suggested to facilitate injection. The viscoelastic properties of CaHA and CMC were measured with a rheometer. The effects of heating and shearing on sample viscoelasticity were recorded. CaHA was 9.5 times more viscous than CMC (43,100 vs 4540 Pa·s). Heating temporarily decreased the viscosity of CaHA by 32%. However, it also caused the viscosity to subsequently increase after time. Shearing of CaHA reduced its viscosity by 26%. Heating and shearing together temporarily reduced the viscosity of CaHA by 52%. A combination of heating and shearing had a more profound effect than heating or shearing alone on the viscosity of CaHA, potentially making it easier to inject temporarily. Long-term and in vivo studies are required to further analyze the effect of heating and shearing on CaHA injectables. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2016.

Measuring Viscosities of Gases at Atmospheric Pressure

Science.gov (United States)

Singh, Jag J.; Mall, Gerald H.; Hoshang, Chegini

1987-01-01

Variant of general capillary method for measuring viscosities of unknown gases based on use of thermal mass-flowmeter section for direct measurement of pressure drops. In technique, flowmeter serves dual role, providing data for determining volume flow rates and serving as well-characterized capillary-tube section for measurement of differential pressures across it. New method simple, sensitive, and adaptable for absolute or relative viscosity measurements of low-pressure gases. Suited for very complex hydrocarbon mixtures where limitations of classical theory and compositional errors make theoretical calculations less reliable.

Including fluid shear viscosity in a structural acoustic finite element model using a scalar fluid representation.

Science.gov (United States)

Cheng, Lei; Li, Yizeng; Grosh, Karl

2013-08-15

An approximate boundary condition is developed in this paper to model fluid shear viscosity at boundaries of coupled fluid-structure system. The effect of shear viscosity is approximated by a correction term to the inviscid boundary condition, written in terms of second order in-plane derivatives of pressure. Both thin and thick viscous boundary layer approximations are formulated; the latter subsumes the former. These approximations are used to develop a variational formation, upon which a viscous finite element method (FEM) model is based, requiring only minor modifications to the boundary integral contributions of an existing inviscid FEM model. Since this FEM formulation has only one degree of freedom for pressure, it holds a great computational advantage over the conventional viscous FEM formulation which requires discretization of the full set of linearized Navier-Stokes equations. The results from thick viscous boundary layer approximation are found to be in good agreement with the prediction from a Navier-Stokes model. When applicable, thin viscous boundary layer approximation also gives accurate results with computational simplicity compared to the thick boundary layer formulation. Direct comparison of simulation results using the boundary layer approximations and a full, linearized Navier-Stokes model are made and used to evaluate the accuracy of the approximate technique. Guidelines are given for the parameter ranges over which the accurate application of the thick and thin boundary approximations can be used for a fluid-structure interaction problem.

Effects of Red Blood Cell Aggregation on the Apparent Viscosity of Blood Flow in Tubes.

Science.gov (United States)

Hitt, Darren L.; Lowe, Mary L.

1996-11-01

In arterioles and venules (20-200μ diameter), the low shear rates enable red blood cells to form aggregate structures of varying sizes and morphology. The size and distribution of the aggregates affect the flow impedance within a microvascular network; this effect may be characterized by an "apparent viscosity". In this study, we measure the apparent viscosity of blood flow in 50μ glass tubes as a function of shear rate and red blood cell volume fraction (hematocrit); for a fixed tube geometry and an imposed flow rate, the viscosity is determined by measuring the pressure drop across the tube. To correlate the apparent viscosity with the size and spatial distribution of the aggregates in the flow, video images of the flow are recorded and analyzed using power spectral techniques. Pig blood and sheep blood are used as the models for aggregating and non-aggregating blood, respectively. Supported by NSF PFF Award CTS-9253633

Nucleon matter equation of state, particle number fluctuations, and shear viscosity within UrQMD box calculations

Science.gov (United States)

Motornenko, A.; Bravina, L.; Gorenstein, M. I.; Magner, A. G.; Zabrodin, E.

2018-03-01

Properties of equilibrated nucleon system are studied within the ultra-relativistic quantum molecular dynamics (UrQMD) transport model. The UrQMD calculations are done within a finite box with periodic boundary conditions. The system achieves thermal equilibrium due to nucleon-nucleon elastic scattering. For the UrQMD-equilibrium state, nucleon energy spectra, equation of state, particle number fluctuations, and shear viscosity η are calculated. The UrQMD results are compared with both, statistical mechanics and Chapman-Enskog kinetic theory, for a classical system of nucleons with hard-core repulsion.

Viscosity calculated in simulations of strongly coupled dusty plasmas with gas friction

International Nuclear Information System (INIS)

Feng Yan; Goree, J.; Liu Bin

2011-01-01

A two-dimensional strongly coupled dusty plasma is modeled using Langevin and frictionless molecular dynamical simulations. The static viscosity η and the wave-number-dependent viscosity η(k) are calculated from the microscopic shear in the random motion of particles. A recently developed method of calculating the wave-number-dependent viscosity η(k) is validated by comparing the results of η(k) from the two simulations. It is also verified that the Green-Kubo relation can still yield an accurate measure of the static viscosity η in the presence of a modest level of friction as in dusty plasma experiments.

Estimation of viscosity based on transverse momentum correlations

Science.gov (United States)

Sharma, Monika

2010-02-01

The heavy ion program at RHIC created a paradigm shift in the exploration of strongly interacting hot and dense matter. An important milestone achieved is the discovery of the formation of strongly interacting matter which seemingly flows like a perfect liquid at temperatures on the scale of T ˜ 2 x10^12 K [1]. As a next step, we consider measurements of transport coefficients such as kinematic, shear or bulk viscosity? Many calculations based on event anisotropy measurements indicate that the shear viscosity to the entropy density ratio (η/s) of the fluid formed at RHIC is significantly below that of all known fluids including the superfluid ^4He [2]. Precise determination of η/s ratio is currently a subject of extensive study. We present an alternative technique for the determination of medium viscosity proposed by Gavin and Aziz [3]. Preliminary results of measurements of the evolution of the transverse momentum correlation function with collision centrality of Au + Au interactions at √sNN = 200 GeV will be shown. We present results on differential version of the correlation measure and describe its use for the experimental determination of η/s.[4pt] [1] J. Adams et al., [STAR Collaboration], Nucl. Phys. A 757 (2005) 102.[0pt] [2] R. A. Lacey et al., Phys. Rev. Lett. 98 (2007) 092301.[0pt] [3] S. Gavin and M. Abdel-Aziz, Phys. Rev. Lett. 97 (2006) 162302. )

Pressure Effect on Extensional Viscosity

DEFF Research Database (Denmark)

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....... The experiments show a significant increase in extensional viscosity with increasing pressure....

Determining Quiescent Colloidal Suspension Viscosities Using the Green-Kubo Relation and Image-Based Stress Measurements

Science.gov (United States)

Lin, Neil Y. C.; Bierbaum, Matthew; Cohen, Itai

2017-09-01

By combining confocal microscopy and stress assessment from local structural anisotropy, we directly measure stresses in 3D quiescent colloidal liquids. Our noninvasive and nonperturbative method allows us to measure forces ≲50 fN with a small and tunable probing volume, enabling us to resolve the stress fluctuations arising from particle thermal motions. We use the Green-Kubo relation to relate these measured stress fluctuations to the bulk Brownian viscosity at different volume fractions, comparing against simulations and conventional rheometry measurements. We find that the Green-Kubo analysis gives excellent agreement with these prior results, suggesting that similar methods could be applied to investigations of local flow properties in many poorly understood far-from-equilibrium systems, including suspensions that are glassy, strongly sheared, or highly confined.

Large particles increase viscosity and yield stress of pig cecal contents without changing basic viscoelastic properties.

Science.gov (United States)

Takahashi, Toru; Sakata, Takashi

2002-05-01

The viscosity of gut contents should influence digestion and absorption. Earlier investigators measured the viscosity of intestinal contents after the removal of solid particles. However, we previously found that removal of solid particles from pig cecal contents dramatically lowered the viscosity of the contents. Accordingly, we examined the contribution of large solid particles to viscoelastic parameters of gut contents in the present study. We removed large particles from pig cecal contents by filtration through surgical gauze. Then, we reconstructed the cecal contents by returning all, one half or none of the original amount of the large particles to the filtrate. We measured the viscosity, shear stress and shear rate of these reconstructed cecal contents using a tube-flow viscometer. The coefficient of viscosity was larger when the large-particle content was higher (P Bingham plastic nature irrespective of large-particle content. We calculated the yield stress of these fluids assuming that the fluids behave as Bingham plastic. The yield stress of the cecal contents was greater (P Bingham plastic characteristics to pig cecal contents.

Applicability of viscosity measurement to the detection of irradiated peppers

International Nuclear Information System (INIS)

Hayashi, T.; Todoriki, S.; Kohyama, K.

1996-01-01

Starch is degraded by ionising radiation, resulting in a decrease in viscosity. The viscosities of black and white peppers which contain large amounts of starch are reduced by irradiation so, therefore, viscosity measurement has been proposed as a method to detect the irradiation treatment of these food products. Although detection of irradiated spices by thermoluminescence measurement has been established, it is useful to establish the viscosity measuring technique for detecting irradiated peppers, as this method is carried out widely in the laboratories of food controlling authorities and food processing companies. (author)

Equation of state and viscosities from a gravity dual of the gluon plasma

Directory of Open Access Journals (Sweden)

R. Yaresko

2015-07-01

Full Text Available Employing new precision data of the equation of state of the SU(3 Yang–Mills theory (gluon plasma the dilaton potential of a gravity-dual model is adjusted in the temperature range (1–10Tc within a bottom-up approach. The ratio of bulk viscosity to shear viscosity follows then as ζ/η≈πΔvs2 for Δvs2<0.2 and achieves a maximum value of 0.94 at Δvs2≈0.3, where Δvs2≡1/3−vs2 is the non-conformality measure and vs2 is the velocity of sound squared, while the ratio of shear viscosity to entropy density is known as (4π−1 for the considered set-up with Hilbert action on the gravity side.

Shear dilatancy and acoustic emission in dry and saturated granular materials

Science.gov (United States)

Brodsky, E. E.; Siman-Tov, S.

2017-12-01

Shearing of granular materials plays a strong role in naturally sheared systems as landslides and faults. Many works on granular flows have concentrated on dry materials, but relatively little work has been done on water saturated sands. Here we experimentally investigate dry versus saturated quartz-rich sand to understand the effect of the fluid medium on the rheology and acoustic waves emission of the sheared sand. The sand was sheared in a rotary shear rheometer under applied constant normal stress boundary at low (100 µm/s) to high (1 m/s) velocities. Mechanical, acoustic data and deformation were continuously recorded and imaged. For dry and water saturated experiments the granular volume remains constant for low shear velocities ( 10-3 m/s) and increases during shearing at higher velocities ( 1 m/s). Continuous imaging of the sheared sand show that the steady state shear band thickness is thicker during the high velocity steps. No significant change observed in the shear band thickness between dry and water saturated experiments. In contrast, the amount of dilation during water saturated experiments is about half the value measured for dry material. The measured decrease cannot be explained by shear band thickness change as such is not exist. However, the reduced dilation is supported by our acoustic measurements. In general, the event rate and acoustic event amplitudes increase with shear velocity. While isolated events are clearly detected during low velocities at higher the events overlap, resulting in a noisy signal. Although detection is better for saturated experiments, during the high velocity steps the acoustic energy measured from the signal is lower compared to that recorded for dry experiments. We suggest that the presence of fluid suppresses grain motion and particles impacts leading to mild increase in the internal pressure and therefore for the reduced dilation. In addition, the viscosity of fluids may influence the internal pressure via

Viscosity evolution of anaerobic granular sludge

NARCIS (Netherlands)

Pevere, A.; Guibaud, G.; Hullebusch, van E.D.; Lens, P.N.L.; Baudu, M.

2006-01-01

The evolution of the apparent viscosity at steady shear rate of sieved anaerobic granular sludge (20¿315 ¿m diameter) sampled from different full-scale anaerobic reactors was recorded using rotation tests. The ¿limit viscosity¿ of sieved anaerobic granular sludge was determined from the apparent

Viscosity of dilute suspensions of rigid bead arrays at low shear: accounting for the variation in hydrodynamic stress over the bead surfaces.

Science.gov (United States)

Allison, Stuart A; Pei, Hongxia

2009-06-11

In this work, we examine the viscosity of a dilute suspension of irregularly shaped particles at low shear. A particle is modeled as a rigid array of nonoverlapping beads of variable size and geometry. Starting from a boundary element formalism, approximate account is taken of the variation in hydrodynamic stress over the surface of the individual beads. For a touching dimer of two identical beads, the predicted viscosity is lower than the exact value by 5.2%. The methodology is then applied to several other model systems including tetramers of variable conformation and linear strings of touching beads. An analysis is also carried out of the viscosity and translational diffusion of several dilute amino acids and diglycine in water. It is concluded that continuum hydrodynamic modeling with stick boundary conditions is unable to account for the experimental viscosity and diffusion data simultaneously. A model intermediate between "stick" and "slip" could possibly reconcile theory and experiment.

Temperature Dependence of the Viscosity of Isotropic Liquids

Science.gov (United States)

Jadzyn, J.; Czechowski, G.; Lech, T.

1999-04-01

Temperature dependence of the shear viscosity measured for isotropic liquids belonging to the three homologous series: 4-(trans-4'-n-alkylcyclohexyl) isothiocyanatobenzenes (Cn H2n+1 CyHx Ph NCS; nCHBT, n=0-12), n-alkylcyanobiphenyls (CnH2n+1 Ph Ph CN; nCB, n=2-12) and 1,n-alkanediols (HO(CH2)nOH; 1,nAD, n=2-10) were analysed with the use of Arrhenius equation and its two modifications: Vogel--Fulcher and proposed in this paper. The extrapolation of the isothermal viscosity of 1,n-alkanediols (n=2-10) to n=1 leads to an interesting conclusion concerning the expected viscosity of methanediol, HOCH2OH, the compound strongly unstable in a pure state.

The effect of shear and extensional viscosities on atomization of Newtonian and non-Newtonian fluids in ultrasonic inhaler.

Science.gov (United States)

Broniarz-Press, L; Sosnowski, T R; Matuszak, M; Ochowiak, M; Jabłczyńska, K

2015-05-15

The paper contains results of the experimental study on atomization process of aqueous solutions of glycerol and aqueous solutions of glycerol-polyacrylamide (Rokrysol WF1) in an ultrasonic inhaler. In experiments the different concentration aqueous solutions of glycerol and glycerol-polyacrylamide have been tested. The results have been obtained by the use of laser diffraction technique. The differences between characteristics of ultrasonic atomization for test liquids have been observed. The analysis of drop size histograms shows that the different sizes of drops have been formed during atomization process. The present study confirmed the previous reports which suggested that the drops size changes with the increase in viscosity of solution changes in spray characteristics were also observed. It has been shown that the shear and extensional viscosities affect the process of atomization. Copyright © 2015 Elsevier B.V. All rights reserved.

Viscosity of two-dimensional strongly coupled dusty plasma modified by a perpendicular magnetic field

Science.gov (United States)

Feng, Yan; Lin, Wei; Murillo, M. S.

2017-11-01

Transport properties of two-dimensional (2D) strongly coupled dusty plasmas have been investigated in detail, but never for viscosity with a strong perpendicular magnetic field; here, we examine this scenario using Langevin dynamics simulations of 2D liquids with a binary Yukawa interparticle interaction. The shear viscosity η of 2D liquid dusty plasma is estimated from the simulation data using the Green-Kubo relation, which is the integration of the shear stress autocorrelation function. It is found that, when a perpendicular magnetic field is applied, the shear viscosity of 2D liquid dusty plasma is modified substantially. When the magnetic field is increased, its viscosity increases at low temperatures, while at high temperatures its viscosity diminishes. It is determined that these different variational trends of η arise from the different behaviors of the kinetic and potential parts of the shear stress under external magnetic fields.

Viscosity measurements on metal melts at high pressure and viscosity calculations for the earth's core

International Nuclear Information System (INIS)

Mineev, Vladimir N; Funtikov, Aleksandr I

2004-01-01

A review is given of experimental and calculated data on the viscosity of iron-based melts on the melting curve. The interest in these data originates in the division of opinion on whether viscosity increases rather moderately or considerably in the high-pressure range. This disagreement is especially pronounced in the interpretation of the values of molten iron and its compounds in the environment of the earth's outer core. The conclusion on a substantial rise in viscosity mostly follows from the universal law, proposed by Brazhkin and Lyapin [1], of viscosity changing along the metal melting curve in the high-pressure range. The review analyzes available experimental and computational data, including the most recent ones. Data on viscosity of metals under shock wave compression in the megabar pressure range are also discussed. It is shown that data on viscosity of metal melts point to a small increase of viscosity on the melting curve. Specifics are discussed of the phase diagram of iron made more complex by the presence of several phase transitions and by the uncertainty in the position of the melting curve in the high-pressure range. Inaccuracies that arise in extrapolating the results of viscosity measurements to the pressure range corresponding to the earth's core environment are pointed out. (reviews of topical problems)

A viscosity and density meter with a magnetically suspended rotor

International Nuclear Information System (INIS)

Bano, Mikulas; Strharsky, Igor; Hrmo, Igor

2003-01-01

A device for measuring the viscosity and density of liquids is presented. It is a Couette-type viscometer that uses a submerged rotor to measure the viscosity without errors originating in the contact of the rotor with the sample/air boundary. The inner cylinder is a glass rotor suspended in the liquid, and the outer cylinder is also made of glass. The rotor is stabilized on the axis of the outer cylinder by an electromagnetic force controlled by feedback from the rotor's vertical position. In the lower part of the rotor is an aluminum cylinder located in a magnetic field generated by rotating permanent magnets. The interaction of this rotating magnetic field with eddy currents generated in the aluminum cylinder causes rotation of the rotor. This rotation is optically detected, and viscosity is calculated from the measured angular velocity of rotor. The density of the liquid is calculated from the applied vertical equilibrating force. A computer controls the whole measurement. The device works at constant temperature or while scanning temperature. The sample volume is 1.6 ml, and the accuracy of measurement of both viscosity and density is ∼0.1%. The range of measured densities is (0.7-1.4) g/ml, and viscosity can be measured in the range (3x10 -4 -0.3) Pa s. The shear rate of the viscosity measurement varies in the range (20-300) s-1. The accuracy of the temperature measurement is 0.02 K

Study on viscosity measurement using fiber Bragg grating micro-vibration

International Nuclear Information System (INIS)

Song, Le; Fang, Fengzhou; Zhao, Jibo

2013-01-01

It is now ascertained that traditional electric sensors are vulnerable to electromagnetic interference when measuring viscosity. Here, we propose a new viscosity-sensitive structure based on the fiber Bragg grating (FBG) sensing principle and a micro-vibration measurement method. The symmetric micro-vibration motivation method is also described, and a mathematical model for compensational voltage and fluid viscosity is established. The probe amplitude, which is produced by reciprocating stimulation, is accessible by means of an FBG sensor mounted on an equal-strength beam. Viscosity can be therefore calculated using a demodulation technique based on linear edge filtering with long period grating. After performing a group of verifying tests, the sensor has been subsequently calibrated with a series of standard fluids to determine uncertain parameters in the mathematical model. The results of the experiment show that the relative measurement error was less than 2% when the viscosity ranged from 200 to 500 mPa s. The proposed architecture utilizes the characteristics of anti-interference, fast response speed, high resolution and compact structure of FBG, thereby offering a novel modality to achieve an online viscosity measurement. (paper)

Shear thinning behaviors in magmas

Science.gov (United States)

Vetere, F. P.; Cassetta, M.; Perugini, D.

2017-12-01

Studies on magma rheology are of fundamental importance to understanding magmatic processes from depth to surface. Since viscosity is one of the most important parameter controlling eruption mechanisms, as well as lava flow emplacement, a comprehensive knowledge on the evolution of magma viscosities during crystallization is required. We present new viscosity data on partly crystalized basalt, andesite and analogue lavas comparable to those erupted on Mercury's northern volcanic plains. High-temperature viscosity measurements were performed using a rotational Anton Paar RheolabQC viscometer head at the PVRG labs, in Perugia (Italy) (http://pvrg.unipg.it). The relative proportion of phases in each experimental run were determined by image analysis on BS-SEM images at different magnifications; phases are glasses, clinopyroxene, spinel, plagioclase for the basalt, plagioclase and spinel for the andesite and pure enstatite and clinopyroxenes, for the analogue Mercury's composition. Glass and crystalline fractions determined by image analysis well correlate with compositions of residual melts. In order to constrain the viscosity (η) variations as a function of crystallinity, shear rate (γ) was varied from 0.1 to 5 s-1. Viscosity vs. time at constant temperature shows a typical S-shape curve. In particular, for basaltic composition η vary from 3.1-3.8 Pa s [log η] at 1493 K and crystallinity of 19 area % as γ vary from 1.0 to 0.1 s-1; the andesite viscosity evolution is 3.2 and 3.7 Pa s [log η] as γ varies from 1 to 0.1 at 1493 K and crystal content of 17 area %; finally, Mercury's analogue composition was investigated at different temperature ranging from 1533 to 1502 K (Vetere et al., 2017). Results, for γ = 0.1, 1.0 and 5.0 s-1, show viscosity variation between 2.7-4.0, 2.5-3.4 and 2.0-3.0 [log η inPa s] respectively while crystallinity vary from 9 to 27 (area %). As viscosity decreases as shear rate increases, these data points to a shear thinning behaviour

Relating Fresh Concrete Viscosity Measurements from Different Rheometers.

Science.gov (United States)

Ferraris, Chiara F; Martys, Nicos S

2003-01-01

Concrete rheological properties need to be properly measured and predicted in order to characterize the workability of fresh concrete, including special concretes such as self-consolidating concrete (SCC). It was shown by a round-robin test held in 2000 [1,2] that different rheometer designs gave different values of viscosity for the same concrete. While empirical correlation between different rheometers was possible, for a procedure that is supposed to "scientifically" improve on the empirical slump tests, this situation is unsatisfactory. To remedy this situation, a new interpretation of the data was developed. In this paper, it is shown that all instruments tested could be directly and quantitatively compared in terms of relative plastic viscosity instead of the plastic viscosity alone. This should eventually allow the measurements from various rheometer designs to be directly calibrated against known standards of plastic viscosity, putting concrete rheometry and concrete workability on a sounder materials science basis.

Kinetic transport is needed to reliably extract shear viscosity from pA and AA data arXiv

CERN Document Server

Kurkela, Aleksi; Wu, Bin

The azimuthal anisotropies $v_n$ of particle spectra measured in proton-nucleus (pA) and nucleus-nucleus (AA) collisions play a key role in constraining QCD matter properties like the shear viscosity over entropy density ratio $\\eta/s$. Here, we compare calculations of $v_n$'s from viscous fluid dynamics and from kinetic transport which start both from the same initial conditions and which implement the same matter properties. We observe that both approaches lead to parametrically different $\\eta/s$-dependencies of the elliptic anisotropy $v_2$ and they may thus lead to quantitatively different results for the phenomenologically inferred value of $\\eta/s$. The parametric differences can be traced to the boost-invariant longitudinal expansion of pA and AA collisions which induces in fluid dynamic results of the $\\eta/s$-dependence of $v_2$ a dominant sensitivity on the initial conditions. Transport theory is free of this problem and it accounts for the order of magnitude of experimentally observed signal stren...

Comparison between apparent viscosity related to irradiation dose for corn starch and black pepper

International Nuclear Information System (INIS)

Casandroiu, T.; Oprita, N.; Ferdes, O.S.

1999-01-01

Dose-effect relationship was studied in the rheoviscometric behaviour of geliffied suspensions of irradiated corn starch and black pepper, as the variation of the apparent viscosity and the shear stress related to the dose. Irradiation has been performed up to 16 kGy. Black pepper was ground and sieved to three particle sizes to analyse also the influence of particle size on the apparent viscosity variation by dose. The rheoviscometric measurements have been carried out by a rotationary viscometer on geliffied suspensions of starch and black pepper, into equivalent starch concentration and alkalinised suspensions for pepper. For starch, shear stress variation by dose is exponential, where the coefficients depend on the shear rate. For black pepper, the curves of apparent viscosity relation to dose also fit an exponential equation and the influence of particle size is discussed, too. Viscometric behaviour similar to irradiation of both corn starch and black pepper could be attributed to starch degradation at relatively high doses and should be used to develop an identification and control method for the ionizing treatment of starch-based food materials. (author)

High-pressure viscosity measurements for the ethanol plus toluene binary system

DEFF Research Database (Denmark)

Zeberg-Mikkelsen, Claus Kjær; Baylaucq, A.; Watson, G.

2005-01-01

measured with a classical capillary viscometer (Ubbelohde) with an uncertainty of 1%. A total of 209 experimental measurements have been obtained for this binary system, which reveals a non-monotonic behavior of the viscosity as a function of the composition, with a minimum. The viscosity behavior...... interacting system showing a negative deviation from ideality. The viscosity of this binary system is represented by the Grunberg-Nissan and the Katti-Chaudhri mixing laws with an overall uncertainty of 12% and 8%, respectively. The viscosity of methanol (23 point) has also been measured in order to verify...

Structure-rheology relationship in a sheared lamellar fluid.

Science.gov (United States)

Jaju, S J; Kumaran, V

2016-03-01

The structure-rheology relationship in the shear alignment of a lamellar fluid is studied using a mesoscale model which provides access to the lamellar configurations and the rheology. Based on the equations and free energy functional, the complete set of dimensionless groups that characterize the system are the Reynolds number (ργL(2)/μ), the Schmidt number (μ/ρD), the Ericksen number (μγ/B), the interface sharpness parameter r, the ratio of the viscosities of the hydrophilic and hydrophobic parts μ(r), and the ratio of the system size and layer spacing (L/λ). Here, ρ and μ are the fluid density and average viscosity, γ is the applied strain rate, D is the coefficient of diffusion, B is the compression modulus, μ(r) is the maximum difference in the viscosity of the hydrophilic and hydrophobic parts divided by the average viscosity, and L is the system size in the cross-stream direction. The lattice Boltzmann method is used to solve the concentration and momentum equations for a two dimensional system of moderate size (L/λ=32) and for a low Reynolds number, and the other parameters are systematically varied to examine the qualitative features of the structure and viscosity evolution in different regimes. At low Schmidt numbers where mass diffusion is faster than momentum diffusion, there is fast local formation of randomly aligned domains with "grain boundaries," which are rotated by the shear flow to align along the extensional axis as time increases. This configuration offers a high resistance to flow, and the layers do not align in the flow direction even after 1000 strain units, resulting in a viscosity higher than that for an aligned lamellar phase. At high Schmidt numbers where momentum diffusion is fast, the shear flow disrupts layers before they are fully formed by diffusion, and alignment takes place by the breakage and reformation of layers by shear, resulting in defects (edge dislocations) embedded in a background of nearly aligned layers

Origin of shear thickening in semidilute wormlike micellar solutions and evidence of elastic turbulence

International Nuclear Information System (INIS)

Marín-Santibáñez, Benjamín M.; Pérez-González, José; Rodríguez-González, Francisco

2014-01-01

The origin of shear thickening in an equimolar semidilute wormlike micellar solution of cetylpyridinium chloride and sodium salicylate was investigated in this work by using Couette rheometry, flow visualization, and capillary Rheo-particle image velocimetry. The use of the combined methods allowed the discovery of gradient shear banding flow occurring from a critical shear stress and consisting of two main bands, one isotropic (transparent) of high viscosity and one structured (turbid) of low viscosity. Mechanical rheometry indicated macroscopic shear thinning behavior in the shear banding regime. However, local velocimetry showed that the turbid band increased its viscosity along with the shear stress, even though barely reached the value of the viscosity of the isotropic phase. This shear band is the precursor of shear induced structures that subsequently give rise to the average increase in viscosity or apparent shear thickening of the solution. Further increase in the shear stress promoted the growing of the turbid band across the flow region and led to destabilization of the shear banding flow independently of the type of rheometer used, as well as to vorticity banding in Couette flow. At last, vorticity banding disappeared and the flow developed elastic turbulence with chaotic dynamics

Experimental viscosity measurements of biodiesels at high pressure

Directory of Open Access Journals (Sweden)

Schaschke C.J.

2016-01-01

Full Text Available The viscosity of biodiesels of soybean and rapeseed biodiesels blended with mineral diesel fuel were measured at pressures of up to 200 MPa. Using a falling sinker-type viscometer reproducible viscosity data were obtained based on the time taken for a sinker to descend a fixed distance down an enclosed tube under the influence of gravity. Measurements were taken using pressures which correspond to those of interest in automotive common rail diesel engines, and at temperatures of between 25ºC and 80ºC. In all cases, the viscosity of the biodiesel blends were found to increase exponentially for which the blends were noted as being more viscous than pure mineral fuels. A pressure-freezing effect was not observed for the blends.

Elongational viscosity of monodisperse and bidisperse polystyrene melts

DEFF Research Database (Denmark)

Nielsen, Jens Kromann; Rasmussen, Henrik Koblitz; Hassager, Ole

2005-01-01

The startup and steady uniaxial elongational viscosity have been measured for two monodisperse polystyrene melts with molecular weights of 52 kg/mole (PS52K) and 103 kg/mole (PS103K), and for three bidisperse polystyrene melts. The bidisperse melts consist of PS103K or PS52K and a monodisperse...... (closed loop proportional regulator) using the laser in such a way that the stretch rate at the neck is kept constant. The rheometer has been described in more detail in (A. Bach, H.K. Rasmussen and O. Hassager, Journal of Rheology, 47 (2003) 429). PS390K show a decrease in the steady viscosity as a power......-law function of the elongational rate (A. Bach, K. Almdal, H.K. Rasmussen and O. Hassager, Macromolecules 36 (2003) 5174). PS52K and PS103K show that the steady viscosity has a maximum that is respectively 100% and 50% above 3 times the zero-shear-rate viscosity. The bidisperse melts show a significant...

Microfluidic method for measuring viscosity using images from smartphone

Science.gov (United States)

Kim, Sooyeong; Kim, Kyung Chun; Yeom, Eunseop

2018-05-01

The viscosity of a fluid is the most important characteristic in fluid rheology. Many microfluidic devices have been proposed for easily measuring the fluid viscosity of small samples. A hybrid system consisting of a smartphone and microfluidic device can offer a mobile laboratory for performing a wide range of detection and analysis functions related to healthcare. In this study, a new mobile sensing method based on a microfluidic device was proposed for fluid viscosity measurements. By separately delivering sample and reference fluids into the two inlets of a Y-shaped microfluidic device, an interfacial line is induced at downstream of the device. Because the interfacial width (W) between the sample and reference fluid flows was determined by their pressure ratio, the viscosity (μ) of the sample could be estimated by measuring the interfacial width. To distinguish the interfacial width of a sample, optical images of the flows at downstream of the Y-shaped microfluidic device were acquired using a smartphone. To check the measurement accuracy of the proposed method, the viscosities of glycerol mixtures were compared with those measured by a conventional viscometer. The proposed technique was applied to monitor the variations in blood and oil samples depending on storage or rancidity. We expect that this mobile sensing method based on a microfluidic device could be utilized as a viscometer with significant advantages in terms of mobility, ease-of-operation, and data management.

On viscosity measurements of nanofluids in micro and mini tube flow

International Nuclear Information System (INIS)

Egan, V M; Walsh, P A; Walsh, E J

2009-01-01

This study presents measurements on the relative viscosity of Al 2 O 3 nanofluids, obtained using capillary and rotational viscometers. Suspension volume concentrations between 0.3% and 6.3% were considered and all exhibited Newtonian behaviour. This paper questions previously published data (Jang et al 2007 Appl. Phys. Lett. 91 243112) which show effective viscosity measurements of nanofluids to be strongly dependent on the tube dimension used in a microscale capillary viscometer. Hence, tubes of diameter 337 μm and 1017 μm were employed but no effect on relative viscosity was observed as all measurements compared favourably. Additionally, all viscosity measurements were found to correlate well using classical models when aggregate size was considered in calculating volume concentration.

A viscosity measurement during the high pressure phase transition in triolein

International Nuclear Information System (INIS)

Siegoczynski, R M; Rostocki, A J; Kielczynski, P; Szalewski, M

2008-01-01

The high-pressure properties of triolein, a subject of extensive research at the Faculty of Physics of Warsaw University of Technology (WUT) have been enhanced by the results of viscosity measurement within the pressure range up to 0.8 GPa. For the measurement the authors have adopted a new ultrasonic method based on Bleustein-Gulyaev waves, successfully developed earlier for the low pressures in the Section of Acoustoelectronics of the Institute of Fundamental Technological Research. The measurements have shown: 1. Exponential rise of viscosity with pressure up to 0.5 GPa. 2. Extraordinary increment of viscosity at constant pressure during phase transition. 3. Further exponential rise of viscosity with pressure of the high-pressure phase of triolein. 4. The pressure exponents of the viscosity of both phases were different (the high-pressure phase had much smaller exponent). 5. The decomposition of the high pressure phase due to the slow decompression have shown very large hysteresis of viscosity on pressure dependence

Effect of Qingnao tablet on blood viscosity of rat model of blood stasis induced by epinephrine

Science.gov (United States)

Xie, Guoqi; Hao, Shaojun; Ma, Zhenzhen; Liu, Xiaobin; Li, Jun; Li, Wenjun; Zhang, Zhengchen

2018-04-01

To establish a rat model of blood stasis with adrenaline (Adr) subcutaneous injection and ice bath stimulation. The effects of different doses on the blood viscosity of blood stasis model rats were observed. The rats were randomly divided into 6 groups: blank control group (no model), model group, positive control group, high, middle and low dose group. The whole blood viscosity and plasma viscosity were detected by blood viscosity instrument. Compared with the blank group, model group, high shear, low shear whole blood viscosity and plasma viscosity were significantly increased, TT PT significantly shortened, APTT was significantly prolonged, FIB increased significantly, indicating that the model was successful. Compared with the model group, can significantly reduce the Naoluotong group (cut, low cut). Qingnaopian high dose group (low cut), middle dose group (cut, low shear blood viscosity) (Pgroup, high dose group (Pgroup (Pblood rheology of blood stasis mice abnormal index, decrease the blood viscosity, blood stasis has certain hemostatic effect.

Variation of velocity profile according to blood viscosity in a microfluidic channel

Science.gov (United States)

Yeom, Eunseop; Kang, Yang Jun; Lee, Sang-Joon

2014-11-01

The shear-thinning effect of blood flows is known to change blood viscosity. Since blood viscosity and motion of red blood cells (RBCs) are closely related, hemorheological variations have a strong influence on hemodynamic characteristics. Therefore, understanding on the relationship between the hemorheological and hemodynamic properties is importance for getting more detailed information on blood circulation in microvessels. In this study, the blood viscosity and velocity profiles in a microfluidic channel were systematically investigated. Rat blood was delivered in the microfluidic device which can measure blood viscosity by monitoring the flow-switching phenomenon. Velocity profiles of blood flows in the microchannel were measured by using a micro-particle image velocimetry (PIV) technique. Shape of velocity profiles measured at different flow rates was quantified by using a curve-fitting equation. It was observed that the shape of velocity profiles is highly correlated with blood viscosity. The study on the relation between blood viscosity and velocity profile would be helpful to understand the roles of hemorheological and hemodynamic properties in cardiovascular diseases. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) (No. 2008-0061991).

Viscosity measurements of molten refractory metals using an electrostatic levitator

International Nuclear Information System (INIS)

Ishikawa, Takehiko; Paradis, Paul-François; Okada, Junpei T; Watanabe, Yuki

2012-01-01

Viscosities of several refractory metals (titanium, nickel, zirconium, niobium, ruthenium, rhodium, hafnium, iridium and platinum) and terbium have been measured by the oscillation drop method with an improved procedure. The measured data were less scattered than our previous measurements. Viscosities at their melting temperatures showed good agreement with literature values and some predicted values. (paper)

Self-diffusion coefficients and shear viscosity of inverse power fluids: from hard- to soft-spheres.

Science.gov (United States)

Heyes, D M; Brańka, A C

2008-07-21

Molecular dynamics computer simulation has been used to compute the self-diffusion coefficient, D, and shear viscosity, eta(s), of soft-sphere fluids, in which the particles interact through the soft-sphere or inverse power pair potential, phi(r) = epsilon(sigma/r)(n), where n measures the steepness or stiffness of the potential, and epsilon and sigma are a characteristic energy and distance, respectively. The simulations were carried out on monodisperse systems for a range of n values from the hard-sphere (n --> infinity) limit down to n = 4, and up to densities in excess of the fluid-solid co-existence value. A new analytical procedure is proposed which reproduces the transport coefficients at high densities, and can be used to extrapolate the data to densities higher than accurately accessible by simulation or experiment, and tending to the glass transition. This formula, DX(c-1) proportional, variant A/X + B, where c is an adjustable parameter, and X is either the packing fraction or the pressure, is a development of one proposed by Dymond. In the expression, -A/B is the value of X at the ideal glass transition (i.e., where D and eta(s)(-1) --> 0). Estimated values are presented for the packing fraction and the pressure at the glass transition for n values between the hard and soft particle limits. The above expression is also shown to reproduce the high density viscosity data of supercritical argon, krypton and nitrogen. Fits to the soft-sphere simulation transport coefficients close to solid-fluid co-existence are also made using the analytic form, ln(D) = alpha(X)X, and n-dependence of the alpha(X) is presented (X is either the packing fraction or the pressure).

Measurement of viscosity of gaseous mixtures at atmospheric pressure

Science.gov (United States)

Singh, J. J.; Mall, G. H.; Chegini, H.

1986-01-01

Coefficients of viscosity of various types of gas mixtures, including simulated natural-gas samples, have been measured at atmospheric pressure and room temperature using a modified capillary tube method. Pressure drops across the straight capillary tube section of a thermal mass flowmeter were measured for small, well-defined, volume flow rates for the test gases and for standard air. In this configuration, the flowmeter provides the volumetric flow rates as well as a well-characterized capillary section for differential pressure measurements across it. The coefficients of viscosity of the test gases were calculated using the reported value of 185.6 micro P for the viscosity of air. The coefficients of viscosity for the test mixtures were also calculated using Wilke's approximation of the Chapman-Enskog (C-E) theory. The experimental and calculated values for binary mixtures are in agreement within the reported accuracy of Wilke's approximation of the C-E theory. However, the agreement for multicomponent mixtures is less satisfactory, possible because of the limitations of Wilkes's approximation of the classical dilute-gas state model.

Hemolysis in a laminar flow-through Couette shearing device: an experimental study.

Science.gov (United States)

Boehning, Fiete; Mejia, Tzahiry; Schmitz-Rode, Thomas; Steinseifer, Ulrich

2014-09-01

Reducing hemolysis has been one of the major goals of rotary blood pump development and in the investigational phase, the capability of hemolysis estimation for areas of elevated shear stresses is valuable. The degree of hemolysis is determined by the amplitude of shear stress and the exposure time, but to date, the exact hemolytic behavior at elevated shear stresses and potential thresholds for subcritical shear exposure remain vague. This study provides experimental hemolysis data for a set of shear stresses and exposure times to allow better estimations of hemolysis for blood exposed to elevated shearing. Heparinized porcine blood with a hematocrit of 40% was mechanically damaged in a flow-through laminar Couette shear flow at a temperature of 23°C. Four levels of shear stress, 24, 592, 702, and 842 Pa, were replicated at two exposure times, 54 and 873 ms. For the calculation of the shear stresses, an apparent viscosity of 5 mPas was used, which was verified in an additional measurement of the blood viscosity. The hemolysis measurements were repeated four times, whereby all conditions were measured once within the same day and with blood from the same source. Samples were taken at the inlet and outlet of the shear region and an increase in plasma-free hemoglobin was measured. An index of hemolysis (IH) was thereby calculated giving the ratio of free to total hemoglobin. The results are compared with data from previously published studies using a similar shearing device. Hemolysis was found to increase exponentially with shear stress, but high standard deviations existed at measurements with elevated IH. At short exposure times, the IH remained low at under 0.5% for all shear stress levels. For high exposure times, the IH increased from 0.84% at 592 Pa up to 3.57% at the highest shear stress level. Hemolysis was significant for shear stresses above ∼600 Pa at the high exposure time of 873 ms. Copyright © 2014 International Center for Artificial

Accurate shear measurement with faint sources

International Nuclear Information System (INIS)

Zhang, Jun; Foucaud, Sebastien; Luo, Wentao

2015-01-01

For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys

Microcantilever based disposable viscosity sensor for serum and blood plasma measurements.

Science.gov (United States)

Cakmak, Onur; Elbuken, Caglar; Ermek, Erhan; Mostafazadeh, Aref; Baris, Ibrahim; Erdem Alaca, B; Kavakli, Ibrahim Halil; Urey, Hakan

2013-10-01

This paper proposes a novel method for measuring blood plasma and serum viscosity with a microcantilever-based MEMS sensor. MEMS cantilevers are made of electroplated nickel and actuated remotely with magnetic field using an electro-coil. Real-time monitoring of cantilever resonant frequency is performed remotely using diffraction gratings fabricated at the tip of the dynamic cantilevers. Only few nanometer cantilever deflection is sufficient due to interferometric sensitivity of the readout. The resonant frequency of the cantilever is tracked with a phase lock loop (PLL) control circuit. The viscosities of liquid samples are obtained through the measurement of the cantilever's frequency change with respect to a reference measurement taken within a liquid of known viscosity. We performed measurements with glycerol solutions at different temperatures and validated the repeatability of the system by comparing with a reference commercial viscometer. Experimental results are compared with the theoretical predictions based on Sader's theory and agreed reasonably well. Afterwards viscosities of different Fetal Bovine Serum and Bovine Serum Albumin mixtures are measured both at 23°C and 37°C, body temperature. Finally the viscosities of human blood plasma samples taken from healthy donors are measured. The proposed method is capable of measuring viscosities from 0.86 cP to 3.02 cP, which covers human blood plasma viscosity range, with a resolution better than 0.04 cP. The sample volume requirement is less than 150 μl and can be reduced significantly with optimized cartridge design. Both the actuation and sensing are carried out remotely, which allows for disposable sensor cartridges. Copyright © 2013. Published by Elsevier Inc.

Shear rheological properties of fresh human faeces with different ...

African Journals Online (AJOL)

Samples were further tested for moisture content, total solids, volatile content, and ash content. Faecal samples were found to have a yield stress; there was a decrease in apparent viscosity with increasing shear rate. For any given shear rate, higher apparent viscosities are associated with lower moisture contents. Across a ...

Gravimetric capillary method for kinematic viscosity measurements

Science.gov (United States)

Rosenberger, Franz; Iwan, J.; Alexander, D.; Jin, Wei-Qing

1992-01-01

A novel version of the capillary method for viscosity measurements of liquids is presented. Viscosity data can be deduced in a straightforward way from mass transfer data obtained by differential weighing during the gravity-induced flow of the liquid between two cylindrical chambers. Tests of this technique with water, carbon tetrachloride, and ethanol suggest that this arrangement provides an accuracy of about +/- 1 percent. The technique facilitates operation under sealed, isothermal conditions and, thus can readily be applied to reactive and/or high vapor pressure liquids.

Separate density and viscosity measurements of unknown liquid using quartz crystal microbalance

Directory of Open Access Journals (Sweden)

Feng Tan

2016-09-01

Full Text Available Aqueous liquids have a wide range of applications in many fields. Basic physical properties like the density and the viscosity have great impacts on the functionalities of a given ionic liquid. For the millions kinds of existing liquids, only a few have been systematically measured with the density and the viscosity using traditional methods. However, these methods are limited to measure the density and the viscosity of an ionic liquid simultaneously especially in processing micro sample volumes. To meet this challenge, we present a new theoretical model and a novel method to separate density and viscosity measurements with single quartz crystal microbalance (QCM in this work. The agreement of experimental results and theocratical calculations shows that the QCM is capable to measure the density and the viscosity of ionic liquids.

Should you trust your heavy oil viscosity measurement?

Energy Technology Data Exchange (ETDEWEB)

Nelson, L.; Miller, K.; Almond, R. [Petrovera Resources Ltd., Edmonton, AB (Canada)

2003-07-01

For the last 60 years, the heavy oil and bitumen reservoirs from western Canada have been exploited with varying degrees of success. There are many factors that may effect heavy oil and bitumen production rates. Primary production rates, which vary greatly from field to field, were found to improve with the addition of steam. Viscosity is the single most valued criteria in predicting cold production response from a new field. It is also the criteria used to determine whether thermal process are needed to reduce oil viscosity, or whether horizontal or vertical wells should be used. This study examined why production forecasts based on oil viscosity alone have been poor. It is based on an extensive data collection project in the Elk Point area reservoir which has lower than expected and erratic cold production rates. Viscosity values from the same wells were found to vary by a factor of four or more. One of the objectives of this study was to encourage commercial labs to develop an industry-wide standard method of heavy oil sample cleaning and viscosity measurement. It is generally understood that viscosity increases with an increase in the concentration of asphaltenes, but there is little information to quantify the relationship. Some studies suggest that viscosity increases logarithmically with increasing asphaltenes. It was concluded that the prediction of the viscosity of heavy oils and bitumens is very empirical, but there are ways to improve data comparisons and evaluation by applying available information from other scientific fields. 23 refs., 5 tabs., 6 figs.

Estimation of the shear viscosity from 3FD simulations of Au + Au collisions at √(sNN) = 3.3-39 GeV

International Nuclear Information System (INIS)

Ivanov, Yu.B.; Soldatov, A.A.

2016-01-01

An effective shear viscosity in central Au+Au collisions is estimated in the range of incident energies 3.3 GeV≤√(s NN )≤39 GeV. The simulations are performed within a three-fluid model employing three different equations of state with and without the deconfinement transition. In order to estimate this effective viscosity, we consider the entropy produced in the 3FD simulations as if it is generated within the conventional one-fluid viscous hydrodynamics. It is found that the effective viscosity within the different considered scenarios is very similar at the expansion stage of the collision: as a function of temperature (T) the viscosity-to-entropy ratio behaves as η/s∝1/T 4 ; as a function of the net-baryon density (n B ), η/s∝1/s, i.e. it is mainly determined by the density dependence of the entropy density. The above dependences take place along the dynamical trajectories of Au+Au collisions. At the final stages of the expansion the η/s values are ranged from ∝0.05 at the highest considered energies to ∝.5 at the lowest ones. (orig.)

Study of shear thickening behavior in colloidal suspensions

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N Maleki Jirsaraee

2015-01-01

Full Text Available We studied the shear thickening behavior of the nano silica suspension (silica nanoparticles 12 nm in size suspended in ethylene glycol under steady shear. The critical shear rate for transition into shear thickening phase was determined at different concentrations and temperatures. The effect of temperature and concentration was studied on the shear thickening behavior. In silica suspension, it was observed that all the samples had a transition into shear thickening phase and also by increasing the temperature, critical shear rate increased and viscosity decreased. Our observations showed that movement in silica suspension was Brownian and temperature could cause a delay in transition into shear thickening phase. Yet, we observed that increasing the concentration would decrease critical shear rate and increase viscosity. Increasing temperature increased Brownian forces and increasing concentration increased hydrodynamic forces, confirming the contrast between these two forces for transition into shear thickening phase for the suspensions containing nano particles

Microstructural evolution of a model, shear-banding micellar solution during shear startup and cessation.

Science.gov (United States)

López-Barrón, Carlos R; Gurnon, A Kate; Eberle, Aaron P R; Porcar, Lionel; Wagner, Norman J

2014-04-01

We present direct measurements of the evolution of the segmental-level microstructure of a stable shear-banding polymerlike micelle solution during flow startup and cessation in the plane of flow. These measurements provide a definitive, quantitative microstructural understanding of the stages observed during flow startup: an initial elastic response with limited alignment that yields with a large stress overshoot to a homogeneous flow with associated micellar alignment that persists for approximately three relaxation times. This transient is followed by a shear (kink) band formation with a flow-aligned low-viscosity band that exhibits shear-induced concentration fluctuations and coexists with a nearly isotropic band of homogenous, highly viscoelastic micellar solution. Stable, steady banding flow is achieved only after approximately two reptation times. Flow cessation from this shear-banded state is also found to be nontrivial, exhibiting an initial fast relaxation with only minor structural relaxation, followed by a slower relaxation of the aligned micellar fluid with the equilibrium fluid's characteristic relaxation time. These measurements resolve a controversy in the literature surrounding the mechanism of shear banding in entangled wormlike micelles and, by means of comparison to existing literature, provide further insights into the mechanisms driving shear-banding instabilities in related systems. The methods and instrumentation described should find broad use in exploring complex fluid rheology and testing microstructure-based constitutive equations.

Real-time viscosity and mass density sensors requiring microliter sample volume based on nanomechanical resonators.

Science.gov (United States)

Bircher, Benjamin A; Duempelmann, Luc; Renggli, Kasper; Lang, Hans Peter; Gerber, Christoph; Bruns, Nico; Braun, Thomas

2013-09-17

A microcantilever based method for fluid viscosity and mass density measurements with high temporal resolution and microliter sample consumption is presented. Nanomechanical cantilever vibration is driven by photothermal excitation and detected by an optical beam deflection system using two laser beams of different wavelengths. The theoretical framework relating cantilever response to the viscosity and mass density of the surrounding fluid was extended to consider higher flexural modes vibrating at high Reynolds numbers. The performance of the developed sensor and extended theory was validated over a viscosity range of 1-20 mPa·s and a corresponding mass density range of 998-1176 kg/m(3) using reference fluids. Separating sample plugs from the carrier fluid by a two-phase configuration in combination with a microfluidic flow cell, allowed samples of 5 μL to be sequentially measured under continuous flow, opening the method to fast and reliable screening applications. To demonstrate the study of dynamic processes, the viscosity and mass density changes occurring during the free radical polymerization of acrylamide were monitored and compared to published data. Shear-thinning was observed in the viscosity data at higher flexural modes, which vibrate at elevated frequencies. Rheokinetic models allowed the monomer-to-polymer conversion to be tracked in spite of the shear-thinning behavior, and could be applied to study the kinetics of unknown processes.

Effects of the positioning force of electrostatic levitators on viscosity measurements

International Nuclear Information System (INIS)

Ishikawa, Takehiko; Paradis, Paul-Francois; Koike, Noriyuki; Watanabe, Yuki

2009-01-01

Electrostatic levitators use strong electric fields to levitate and accurately position a sample against gravity. In this study, the effects of the electric field are investigated with regard to viscosity measurements conducted with the oscillating drop method. The effects of the external field on viscosity measurements are experimentally confirmed by changing the sample size. Moreover, a numerical simulation based on a simple mass-spring-damper system can reproduce the experimental observations. Based on the above results, measurement procedures are improved. These help to minimize the effect of the positioning force and to increase the accuracy of the viscosity measurements.

Measurement of viscosity as a means to identify irradiated food

International Nuclear Information System (INIS)

Nuernberger, E.; Heide, L.; Boegl, K.W.

1990-01-01

The measurement of viscosity is a simple method to identify previous irradiation of some kinds of spices and foods, at least in combination with other methods. A possible change of the soaking capacity was examined up to a storage period of 18 months after irradiation of black pepper, white pepper, cinnamon, ginger and onion powder with a radiation dose of 10 kGy each. After irradiation, either increased or decreased viscosity values were measured; the results showed, also after the 18-months-storage period, considerable differences of the viscosity behaviour in non-irradiated and irradiated samples. The time of storage had no effect to the individual viscosity values, so that this method could also be applied to the examined spices after a longer storage period. (orig.) With 51 figs., 25 tabs [de

Radiation effects in polyolefins below the gel point as measured by torque rheometry

International Nuclear Information System (INIS)

Markovic, V.; Babic, D.; Silverman, J.

1981-01-01

Torque rheometry is used to obtain information about radiation effects on polymers (crosslinking, degradation) below the gel point. It is shown that rheometric melt viscosity measurements at different shear rates are related changes in the relaxation spectrum. In particular there is a significant radiation effect on low shear rate viscosities but a negligible effect on high shear rate viscosities. The fact that the shear rate in the torque rheometer oscillates about a mean value is utilized to relate torque amplitude measurements to entanglements at zero dose and to crosslink density at absorbed doses below or close to the gel point. (author)

Effects of Nattokinase on Whole Blood Viscosity and Mortality

Directory of Open Access Journals (Sweden)

Melike Cengiz

2011-12-01

Full Text Available Objective: Nattokinase is a serin protease having potent fibrinolytic effect derived from fermentation of boiled soy bean by the use of Basillus Subtilis Natto. The aim of this experimental study is to investigate the effects of intragastric Nattokinase (6 mg/day administration for 7 days prior to formation of sepsis on plasma fibrinogen levels, whole blood viscosity and mortality in rats. Materials and Methods: Intraabdominal sepsis were performed by cecal ligation and puncture in rats supplemented with nattokinase or olive oil for 7 days prior to sepsis formation. Plasma fibrinogen, whole blood viscosity analysis and survival analysis was performed after intraabdominal sepsis formation. Results: Mean blood viscosity of rats was lower in Nattokinase and cecal ligation group at lowest shear rate (p<0.05. However, the differences between groups were not significant at higher shear rates. No difference was found in survival rates and survival times of Nattokinase and cecal ligation and cecal ligation and puncture groups. Conclusion: Our results were unable to show the effects of intragastric nattokinase supplementation prior to sepsis on plasma fibrinogen levels or whole blood viscosity, except low shear rate. Nattokinase did not altered survival in septic rats. (Journal of the Turkish Society Intensive Care 2011; 9: 85-9

Viscosity estimation utilizing flow velocity field measurements in a rotating magnetized plasma

International Nuclear Information System (INIS)

Yoshimura, Shinji; Tanaka, Masayoshi Y.

2008-01-01

The importance of viscosity in determining plasma flow structures has been widely recognized. In laboratory plasmas, however, viscosity measurements have been seldom performed so far. In this paper we present and discuss an estimation method of effective plasma kinematic viscosity utilizing flow velocity field measurements. Imposing steady and axisymmetric conditions, we derive the expression for radial flow velocity from the azimuthal component of the ion fluid equation. The expression contains kinematic viscosity, vorticity of azimuthal rotation and its derivative, collision frequency, azimuthal flow velocity and ion cyclotron frequency. Therefore all quantities except the viscosity are given provided that the flow field can be measured. We applied this method to a rotating magnetized argon plasma produced by the Hyper-I device. The flow velocity field measurements were carried out using a directional Langmuir probe installed in a tilting motor drive unit. The inward ion flow in radial direction, which is not driven in collisionless inviscid plasmas, was clearly observed. As a result, we found the anomalous viscosity, the value of which is two orders of magnitude larger than the classical one. (author)

Shear flow simulations of biaxial nematic liquid crystals

Science.gov (United States)

Sarman, Sten

1997-08-01

We have calculated the viscosities of a biaxial nematic liquid crystal phase of a variant of the Gay-Berne fluid [J. G. Gay and B. J. Berne, J. Chem. Phys. 74, 3316 (1981)] by performing molecular dynamics simulations. The equations of motion have been augmented by a director constraint torque that fixes the orientation of the directors. This makes it possible to fix them at different angles relative to the stream lines in shear flow simulations. In equilibrium simulations the constraints generate a new ensemble. One finds that the Green-Kubo relations for the viscosities become linear combinations of time correlation function integrals in this ensemble whereas they are complicated rational functions in the conventional canonical ensemble. We have evaluated these Green-Kubo relations for all the shear viscosities and all the twist viscosities. We have also calculated the alignment angles, which are functions of the viscosity coefficients. We find that there are three real alignment angles but a linear stability analysis shows that only one of them corresponds to a stable director orientation. The Green-Kubo results have been cross checked by nonequilibrium shear flow simulations. The results from the different methods agree very well. Finally, we have evaluated the Miesowicz viscosities [D. Baalss, Z. Naturforsch. Teil A 45, 7 (1990)]. They vary by more than 2 orders of magnitude. The viscosity is consequently highly orientation dependent.

A simple model to understand the role of membrane shear elasticity and stress-free shape on the motion of red blood cells in shear flow

Science.gov (United States)

Viallat, Annie; Abkarian, Manouk; Dupire, Jules

2015-11-01

The analytical model presented by Keller and Skalak on the dynamics of red blood cells in shear flow described the cell as a fluid ellipsoid of fixed shape. It was extended to introduce shear elasticity of the cell membrane. We further extend the model when the cell discoid physiological shape is not a stress-free shape. We show that spheroid stress-free shapes enables fitting experimental data with values of shear elasticity typical to that found with micropipettes and optical tweezers. For moderate shear rates (when RBCs keep their discoid shape) this model enables to quantitatively determine an effective cell viscosity, that combines membrane and hemoglobin viscosities and an effective shear modulus of the membrane that combines shear modulus and stress-free shape. This model allows determining RBC mechanical parameters both in the tanktreading regime for cells suspended in a high viscosity medium, and in the tumbling regime for cells suspended in a low viscosity medium. In this regime,a transition is predicted between a rigid-like tumbling motion and a fluid-like tumbling motion above a critical shear rate, which is directly related to the mechanical parameters of the cell. A*MIDEX (n ANR-11-IDEX-0001-02) funded by the ''Investissements d'Avenir'', Region Languedoc-Roussillon, Labex NUMEV (ANR-10-LABX-20), BPI France project DataDiag.

Shear Resistance Variations in Experimentally Sheared Mudstone Granules: A Possible Shear-Thinning and Thixotropic Mechanism

Science.gov (United States)

Hu, Wei; Xu, Qiang; Wang, Gonghui; Scaringi, Gianvito; Mcsaveney, Mauri; Hicher, Pierre-Yves

2017-11-01

We present results of ring shear frictional resistance for mudstone granules of different size obtained from a landslide shear zone. Little rate dependency of shear resistance was observed in sand-sized granules in any wet or dry test, while saturated gravel-sized granules exhibited significant and abrupt reversible rate-weakening (from μ = 0.6 to 0.05) at about 2 mm/s. Repeating resistance variations occurred also under constant shear displacement rate. Mudstone granules generate mud as they are crushed and softened. Shear-thinning and thixotropic behavior of the mud can explain the observed behavior: with the viscosity decreasing, the mud can flow through the coarser soil pores and migrate out from the shear zone. This brings new granules into contact which produces new mud. Thus, the process can start over. Similarities between experimental shear zones and those of some landslides in mudstone suggest that the observed behavior may play a role in some landslide kinematics.

Gas viscosity measurement with diamagnetic-levitation viscometer based on electromagnetically spinning system.

Science.gov (United States)

Shimokawa, Y; Matsuura, Y; Hirano, T; Sakai, K

2016-12-01

Utilizing a graphite-disk probe attached with a thin aluminum disk, we have developed a friction-free viscosity measurement system. The probe is levitated above a NdFeB magnet because of diamagnetic effect and rotated by an electromagnetically induced torque. The probe is absolutely free form mechanical friction, and therefore, the accurate measurements of the viscosity of gases can be achieved. To demonstrate the accuracy and sensitivity of our method, we measured the viscosity of 8 kinds of gases and its temperature change from 278 K to 318 K, and we confirmed a good agreement between the obtained values and literature values. This paper demonstrates that our method has the ability to measure the fluid viscosity in the order of μPa ⋅ s.

Gas viscosity measurement with diamagnetic-levitation viscometer based on electromagnetically spinning system

Science.gov (United States)

Shimokawa, Y.; Matsuura, Y.; Hirano, T.; Sakai, K.

2016-12-01

Utilizing a graphite-disk probe attached with a thin aluminum disk, we have developed a friction-free viscosity measurement system. The probe is levitated above a NdFeB magnet because of diamagnetic effect and rotated by an electromagnetically induced torque. The probe is absolutely free form mechanical friction, and therefore, the accurate measurements of the viscosity of gases can be achieved. To demonstrate the accuracy and sensitivity of our method, we measured the viscosity of 8 kinds of gases and its temperature change from 278 K to 318 K, and we confirmed a good agreement between the obtained values and literature values. This paper demonstrates that our method has the ability to measure the fluid viscosity in the order of μPa ṡ s.

On the viscosity of two 1-butyl-1-methylpyrrolidinium ionic liquids: effect of the temperature and pressure

DEFF Research Database (Denmark)

Gaciño, Félix M.; Comuñas, María J.P.; Regueira Muñiz, Teresa

2015-01-01

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...

Design of a High Viscosity Couette Flow Facility for Patterned Surface Drag Measurements

Science.gov (United States)

Johnson, Tyler; Lang, Amy

2009-11-01

Direct drag measurements can be difficult to obtain with low viscosity fluids such as air or water. In this facility, mineral oil is used as the working fluid to increase the shear stress across the surface of experimental models. A mounted conveyor creates a flow within a plexiglass tank. The experimental model of a flat or patterned surface is suspended above a moving belt. Within the gap between the model and moving belt a Couette flow with a linear velocity profile is created. PIV measurements are used to determine the exact velocities and the Reynolds numbers for each experiment. The model is suspended by bars that connect to the pillow block housing of each bearing. Drag is measured by a force gauge connected to linear roller bearings that slide along steel rods. The patterned surfaces, initially consisting of 2-D cavities, are embedded in a plexiglass plate so as to keep the total surface area constant for each experiment. First, the drag across a flat plate is measured and compared to theoretical values for laminar Couette flow. The drag for patterned surfaces is then measured and compared to a flat plate.

Vesicle dynamics in shear and capillary flows

International Nuclear Information System (INIS)

Noguchi, Hiroshi; Gompper, Gerhard

2005-01-01

The deformation of vesicles in flow is studied by a mesoscopic simulation technique, which combines multi-particle collision dynamics for the solvent with a dynamically triangulated surface model for the membrane. Shape transitions are investigated both in simple shear flows and in cylindrical capillary flows. We focus on reduced volumes, where the discocyte shape of fluid vesicles is stable, and the prolate shape is metastable. In simple shear flow at low membrane viscosity, the shear induces a transformation from discocyte to prolate with increasing shear rate, while at high membrane viscosity, the shear induces a transformation from prolate to discocyte, or tumbling motion accompanied by oscillations between these two morphologies. In capillary flow, at small flow velocities the symmetry axis of the discocyte is found not to be oriented perpendicular to the cylinder axis. With increasing flow velocity, a transition to a prolate shape occurs for fluid vesicles, while vesicles with shear-elastic membranes (like red blood cells) transform into a coaxial parachute-like shape

About a mechanism of the influence of shear stress for viscosity of the blood in vessels of small diameter

Directory of Open Access Journals (Sweden)

Лев Николаевич Катюхин

2014-12-01

Full Text Available It is proposed a physiological and experimentally confirmed explanation of Fåhraeus-Lindqvist-effect in capillaries using the profile analyses of osmotic deformability of red blood cells. It was shown the dose-dependent change of the erythrocytes deformability in the stage of isotropic spheres after forming artificial water pores (nystatin and occlusion (PbCl2 of available pores. The Sigma-effect reducing of hematocrit and viscosity in a shear flow of blood through the vessels of a small diameter was conditioned by the interchange of liquid phase between the erythrocyte and the plasma.

Laboratory Tests for Dispersive Soil Viscosity Determining

Science.gov (United States)

Ter-Martirosyan, Z. G.; Ter-Martirosyan, A. Z.; Sobolev, E. S.

2017-11-01

There are several widespread methods for soil viscosity determining now. The standard shear test device and torsion test apparatus are the most commonly used installations to do that. However, the application of them has a number of disadvantages. Therefore, the specialists of Moscow State University of Civil Engineering proposed a new device to determine the disperse soil viscosity on the basis of a stabilometer with the B-type camera (viscosimeter). The paper considers the construction of a viscosimeter and the technique for determining soil viscosity inside this tool as well as some experimental verification results of its work.

Gluon gas viscosity in nonperturbative region

International Nuclear Information System (INIS)

Il'in, S.V.; Mogilevskij, O.A.; Smolyanskij, S.A.; Zinov'ev, G.M.

1992-01-01

Using the Green-Kubo-type formulae and the cutoff model motivated by Monte Carlo lattice gluodynamics simulations we find the temperature behaviour of shear viscosity of gluon gas in the region of deconfinement phase transition. 22 refs.; 1 fig. (author)

Viscosity characteristics of selected volcanic rock melts

Science.gov (United States)

Hobiger, Manuel; Sonder, Ingo; Büttner, Ralf; Zimanowski, Bernd

2011-02-01

A basic experimental study of the behavior of magma rheology was carried out on remelted volcanic rocks using wide gap viscometry. The complex composition of magmatic melts leads to complicated rheologic behavior which cannot be described with one simple model. Therefore, measurement procedures which are able to quantify non-Newtonian behavior have to be employed. Furthermore, the experimental apparatus must be able to deal with inhomogeneities of magmatic melts. We measured the viscosity of a set of materials representing a broad range of volcanic processes. For the lower viscous melts (low-silica compositions), non-Newtonian behavior is observed, whereas the high-silica melts show Newtonian behavior in the measured temperature and shear rate range (T = 1423 K - 1623 K, γ˙ = 10 - 2 s - 1 - 20 s - 1 ). The non-Newtonian materials show power-law behavior. The measured viscosities η and power-law indexes m lie in the intervals 8 Pa s ≤ η ≤ 210 3 Pa s, 0.71 ≤ m ≤ 1.0 (Grímsvötn basalt), 0.9 Pa s ≤ η ≤ 350 Pa s, 0.61 ≤ m ≤ 0.93 (Hohenstoffeln olivine-melilitite), and 8 Pa s ≤ η ≤ 1.510 4 Pa s, 0.55 ≤ m ≤ 1.0 (Sommata basalt). Measured viscosities of the Newtonian high-silica melts lie in the range 10 4 Pa s ≤ η ≤ 310 5 Pa s.

The microstructure and rheology of a model, thixotropic nanoparticle gel under steady shear and large amplitude oscillatory shear (LAOS)

International Nuclear Information System (INIS)

Min Kim, Jung; Kate Gurnon, A.; Wagner, Norman J.; Eberle, Aaron P. R.; Porcar, Lionel

2014-01-01

The microstructure-rheology relationship for a model, thermoreversible nanoparticle gel is investigated using a new technique of time-resolved neutron scattering under steady and time-resolved large amplitude oscillatory shear (LAOS) flows. A 21 vol. % gel is tested with varying strength of interparticle attraction. Shear-induced structural anisotropy is observed as butterfly scattering patterns and quantified through an alignment factor. Measurements in the plane of flow show significant, local anisotropy develops with alignment along the compressional axis of flow, providing new insights into how gels flow. The microstructure-rheology relationship is analyzed through a new type of structure-Lissajous plot that shows how the anisotropic microstructure is responsible for the observed LAOS response, which is beyond a response expected for a purely viscous gel with constant structure. The LAOS shear viscosities are observed to follow the “Delaware-Rutgers” rule. Rheological and microstructural data are successfully compared across a broad range of conditions by scaling the shear rate by the strength of attraction, providing a method to compare behavior between steady shear and LAOS experiments. However, important differences remain between the microstructures measured at comparatively high frequency in LAOS experiments and comparable steady shear experiments that illustrate the importance of measuring the microstructure to properly interpret the nonlinear, dynamic rheological response

The microstructure and rheology of a model, thixotropic nanoparticle gel under steady shear and large amplitude oscillatory shear (LAOS)

Energy Technology Data Exchange (ETDEWEB)

Min Kim, Jung; Kate Gurnon, A.; Wagner, Norman J., E-mail: wagnernj@udel.edu [Department of Chemical and Biomolecular Engineering and Center for Neutron Science, University of Delaware, Newark, Delaware 19716 (United States); Eberle, Aaron P. R. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Porcar, Lionel [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9 (France)

2014-09-01

The microstructure-rheology relationship for a model, thermoreversible nanoparticle gel is investigated using a new technique of time-resolved neutron scattering under steady and time-resolved large amplitude oscillatory shear (LAOS) flows. A 21 vol. % gel is tested with varying strength of interparticle attraction. Shear-induced structural anisotropy is observed as butterfly scattering patterns and quantified through an alignment factor. Measurements in the plane of flow show significant, local anisotropy develops with alignment along the compressional axis of flow, providing new insights into how gels flow. The microstructure-rheology relationship is analyzed through a new type of structure-Lissajous plot that shows how the anisotropic microstructure is responsible for the observed LAOS response, which is beyond a response expected for a purely viscous gel with constant structure. The LAOS shear viscosities are observed to follow the “Delaware-Rutgers” rule. Rheological and microstructural data are successfully compared across a broad range of conditions by scaling the shear rate by the strength of attraction, providing a method to compare behavior between steady shear and LAOS experiments. However, important differences remain between the microstructures measured at comparatively high frequency in LAOS experiments and comparable steady shear experiments that illustrate the importance of measuring the microstructure to properly interpret the nonlinear, dynamic rheological response.

Impact of viscosity variation and micro rotation on oblique transport of Cu-water fluid.

Science.gov (United States)

Tabassum, Rabil; Mehmood, R; Nadeem, S

2017-09-01

This study inspects the influence of temperature dependent viscosity on Oblique flow of micropolar nanofluid. Fluid viscosity is considered as an exponential function of temperature. Governing equations are converted into dimensionless forms with aid of suitable transformations. Outcomes of the study are shown in graphical form and discussed in detail. Results revealed that viscosity parameter has pronounced effects on velocity profiles, temperature distribution, micro-rotation, streamlines, shear stress and heat flux. It is found that viscosity parameter enhances the temperature distribution, tangential velocity profile, normal component of micro-rotation and shear stress at the wall while it has decreasing effect on tangential component of micro-rotation and local heat flux. Copyright © 2017 Elsevier Inc. All rights reserved.

The Contribution of Red Blood Cell Dynamics to Intrinsic Viscosity and Functional ATP Release

Science.gov (United States)

Forsyth, Alison; Abkarian, Manouk; Wan, Jiandi; Stone, Howard

2010-11-01

In shear flow, red blood cells (RBCs) exhibit a variety of behaviors such as rouleaux formation, tumbling, swinging, and tank-treading. The physiological consequences of these dynamic behaviors are not understood. In vivo, ATP is known to signal vasodilation; however, to our knowledge, no one has deciphered the relevance of RBC microrheology to the functional release of ATP. Previously, we correlated RBC deformation and ATP release in microfluidic constrictions (Wan et al., 2008). In this work, a cone-plate rheometer is used to shear a low hematocrit solution of RBCs at varying viscosity ratios (λ) between the inner cytoplasmic hemoglobin and the outer medium, to determine the intrinsic viscosity of the suspension. Further, using a luciferin-luciferase enzymatic reaction, we report the relative ATP release at varying shear rates. Results indicate that for λ = 1.6, 3.8 and 11.1, ATP release is constant up to 500 s-1, which suggests that the tumbling-tanktreading transition does not alter ATP release in pure shear. For lower viscosity ratios, λ = 1.6 and 3.8, at 500 s-1 a change in slope occurs in the intrinsic viscosity data and is marked by an increase in ATP release. Based on microfluidic observations, this simultaneous change in viscosity and ATP release occurs within the tank-treading regime.

Artificial Neural Network Model to Estimate the Viscosity of Polymer Solutions for Enhanced Oil Recovery

Directory of Open Access Journals (Sweden)

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.

Effective viscosity of confined hydrocarbons

DEFF Research Database (Denmark)

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...

The Effect of the Operating Conditions on the Apparent Viscosity of Crude Palm Oil During Oil Clarification

Directory of Open Access Journals (Sweden)

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 

Origins of the anomalous stress behavior in charged colloidal suspensions under shear.

Science.gov (United States)

Kumar, Amit; Higdon, Jonathan J L

2010-11-01

Numerical simulations are conducted to determine microstructure and rheology of sheared suspensions of charged colloidal particles at a volume fraction of ϕ=0.33. Over broad ranges of repulsive force strength F0 and Péclet number Pe, dynamic simulations show coexistence of ordered and disordered stable states with the state dependent on the initial condition. In contrast to the common view, at low shear rates, the disordered phase exhibits a lower viscosity (μ(r)) than the ordered phase, while this behavior is reversed at higher shear rates. Analysis shows the stress reversal is associated with different shear induced microstructural distortions in the ordered and disordered systems. Viscosity vs shear rate data over a wide range of F0 and Pe collapses well upon rescaling with the long-time self-diffusivity. Shear thinning viscosity in the ordered phase scaled as μ(r)∼Pe(-0.81) at low shear rates. The microstructural dynamics revealed in these studies explains the anomalous behavior and hysteresis loops in stress data reported in the literature.

High Resolution Viscosity Measurement by Thermal Noise Detection

Directory of Open Access Journals (Sweden)

Felipe Aguilar Sandoval

2015-11-01

Full Text Available An interferometric method is implemented in order to accurately assess the thermal fluctuations of a micro-cantilever sensor in liquid environments. The power spectrum density (PSD of thermal fluctuations together with Sader’s model of the cantilever allow for the indirect measurement of the liquid viscosity with good accuracy. The good quality of the deflection signal and the characteristic low noise of the instrument allow for the detection and corrections of drawbacks due to both the cantilever shape irregularities and the uncertainties on the position of the laser spot at the fluctuating end of the cantilever. Variation of viscosity below 0.03 mPa·s was detected with the alternative to achieve measurements with a volume as low as 50 µL.

Simulation of shear thickening in attractive colloidal suspensions.

Science.gov (United States)

Pednekar, Sidhant; Chun, Jaehun; Morris, Jeffrey F

2017-03-01

The influence of attractive forces between particles under conditions of large particle volume fraction, ϕ, is addressed using numerical simulations which account for hydrodynamic, Brownian, conservative and frictional contact forces. The focus is on conditions for which a significant increase in the apparent viscosity at small shear rates, and possibly the development of a yield stress, is observed. The high shear rate behavior for Brownian suspensions has been shown in recent work [R. Mari, R. Seto, J. F. Morris and M. M. Denn PNAS, 2015, 112, 15326-15330] to be captured by the inclusion of pairwise forces of two forms, one a contact frictional interaction and the second a repulsive force often found in stabilized colloidal dispersions. Under such conditions, shear thickening is observed when shear stress is comparable to the sum of the Brownian stress, kT/a 3 , and a characteristic stress based on the combination of interparticle force, i.e. σ ∼ F 0 /a 2 with kT the thermal energy, F 0 the repulsive force scale and a the particle radius. At sufficiently large ϕ, this shear thickening can be very abrupt. Here it is shown that when attractive interactions are present with the noted forces, the shear thickening is obscured, as the viscosity shear thins with increasing shear rate, eventually descending from an infinite value (yield stress conditions) to a plateau at large stress; this plateau is at the same level as the large-shear rate viscosity found in the shear thickened state without attractive forces. It is shown that this behavior is consistent with prior observations in shear thickening suspensions modified to be attractive through depletion flocculation [V. Gopalakrishnan and C. F. Zukoski J. Rheol., 2004, 48, 1321-1344]. The contributions of the contact, attractive, and hydrodynamics forces to the bulk stress are presented, as are the contact networks found at different attractive strengths.

Non-homogeneous flow profiles in sheared bacterial suspensions

Science.gov (United States)

Samanta, Devranjan; Cheng, Xiang

Bacterial suspensions under shear exhibit interesting rheological behaviors including the remarkable ``superfluidic'' state with vanishing viscosity at low shear rates. Theoretical studies have shown that such ``superfluidic'' state is linked with non-homogeneous shear flows, which are induced by coupling between nematic order of active fluids and hydrodynamics of shear flows. However, although bulk rheology of bacterial suspensions has been experimentally studied, shear profiles within bacterial suspensions have not been explored so far. Here, we experimentally investigate the flow behaviors of E. coli suspensions under planar oscillatory shear. Using confocal microscopy and PIV, we measure velocity profiles across gap between two shear plates. We find that with increasing shear rates, high-concentration bacterial suspensions exhibit an array of non-homogeneous flow behaviors like yield-stress flows and shear banding. We show that these non-homogeneous flows are due to collective motion of bacterial suspensions. The phase diagram of sheared bacterial suspensions is systematically mapped as functions of shear rates an bacterial concentrations. Our experiments provide new insights into rheology of bacterial suspensions and shed light on shear induced dynamics of active fluids. Chemical Engineering and Material Science department.

Viscosity measurement - probably a means for detecting radiation treatment of spices?

International Nuclear Information System (INIS)

Heide, L.; Albrich, S.; Boegl, K.W.

1987-12-01

The viscosity of 13 different spices and dried vegetables in total was measured. Optimal conditions were first determined for each product, i.e. concentration, pH-value, temperature, particle size and soaking time. For method evaluation, examinations were primarily performed to study the effect of storage, the reproducibility and the influence of the different varieties of the same spice. In supplement, for pepper, the viscosity was measured as a function of radiation dose. In summation, significant changes in the gel forming capability after irradiation could be observed after preliminary experiments in 8 dried spices (ginger, carrots, leek, cloves, pepper, celery, cinnamon and onions). With 3 spices (ginger, pepper and cinnamon) could the results from examining all different varieties of the same spice be substantiated. An additional influence of storage time on viscosity could not be proved during the investigative period of 8 months. Generally seen, there is no possibility of being able to identify an irradiated spice on the basis of viscosity measurements alone, since the difference between the varieties of one and the same spice is considerably great. However, radiation treatment can be reliably excluded with ginger, pepper and cinnamon, if the viscosities are high (10-20 Pa x s). (orig./MG) [de

Theoretical study of the flow in a fluid damper containing high viscosity silicone oil: Effects of shear-thinning and viscoelasticity

Science.gov (United States)

Syrakos, Alexandros; Dimakopoulos, Yannis; Tsamopoulos, John

2018-03-01

The flow inside a fluid damper where a piston reciprocates sinusoidally inside an outer casing containing high-viscosity silicone oil is simulated using a finite volume method, at various excitation frequencies. The oil is modeled by the Carreau-Yasuda (CY) and Phan-Thien and Tanner (PTT) constitutive equations. Both models account for shear-thinning, but only the PTT model accounts for elasticity. The CY and other generalised Newtonian models have been previously used in theoretical studies of fluid dampers, but the present study is the first to perform full two-dimensional (axisymmetric) simulations employing a viscoelastic constitutive equation. It is found that the CY and PTT predictions are similar when the excitation frequency is low, but at medium and higher frequencies, the CY model fails to describe important phenomena that are predicted by the PTT model and observed in experimental studies found in the literature, such as the hysteresis of the force-displacement and force-velocity loops. Elastic effects are quantified by applying a decomposition of the damper force into elastic and viscous components, inspired from large amplitude oscillatory shear theory. The CY model also overestimates the damper force relative to the PTT model because it underpredicts the flow development length inside the piston-cylinder gap. It is thus concluded that (a) fluid elasticity must be accounted for and (b) theoretical approaches that rely on the assumption of one-dimensional flow in the piston-cylinder gap are of limited accuracy, even if they account for fluid viscoelasticity. The consequences of using lower-viscosity silicone oil are also briefly examined.

Nonlinear interaction of Rayleigh--Taylor and shear instabilities

International Nuclear Information System (INIS)

Finn, J.M.

1993-01-01

Results on the nonlinear behavior of the Rayleigh--Taylor instability and consequent development of shear flow by the shear instability [Phys. Fluids B 4, 488 (1992)] are presented. It is found that the shear flow is generated at sufficient amplitude to reduce greatly the convective transport. For high viscosity, the time-asymptotic state consists of an equilibrium with shear flow and vortex flow (with islands, or ''cat's eyes''), or a relaxation oscillation involving an interplay between the shear instability and the Rayleigh--Taylor instability in the presence of shear. For low viscosity, the dominant feature is a high-frequency nonlinear standing wave consisting of convective vortices localized near the top and bottom boundaries. The localization of these vortices is due to the smaller shear near the boundary regions. The convective transport is largest around these convective vortices near the boundary and there is a region of good confinement near the center. The possible relevance of this behavior to the H mode and edge-localized modes (ELM's) in the tokamak edge region is discussed

Measuring the density and viscosity of H2S-loaded aqueous methyldiethanolamine solution

International Nuclear Information System (INIS)

Shokouhi, Mohammad; Ahmadi, Reza

2016-01-01

Highlights: • Measurement solubility of H 2 S in 46.78 mass% MDEA aqueous solutions. • Measurement density of H 2 S loaded of MDEA aqueous solution. • Measurement viscosity of H 2 S loaded of MDEA aqueous solution. • Correlation of the density and viscosity of H 2 S loaded of MDEA aqueous solution using modified setchenow equation. - Abstract: The density and viscosity of H 2 S-loaded aqueous 46.78 mass% methyldiethanolamine solution were experimentally measured accompanied with the solubility of H 2 S at temperatures (313.15, 328.15 and 343.15) K, pressures from vapor pressure of fresh solution up to 1.0 MPa and loadings up to 1.00 mol of H 2 S per 1 mol of amine. All experimental trials have been carried out using the new setup developed in our laboratory. It was observed that both density and viscosity of mixtures decrease by increasing temperature and density increase by increasing acid gas solubility (loading) by about 4.7%, whereas viscosity has a complicated behavior with H 2 S solubility. Viscosity decreases by increasing acid gas solubility (loading) at 313.15 K by about 20.6% and at 328.15 K by about 15.0%, but it is comparable at 343.15 K in terms of H 2 S solubility. Finally, the experimental density and viscosity data correlated using Modified Setchenow equation.

Study of viscosity of aluminum melt during glass transition by molecular dynamics and Green–Kubo formula

International Nuclear Information System (INIS)

Kirova, E M; Pisarev, V V

2016-01-01

Molecular dynamics study of shear viscosity behavior of liquid aluminum is performed. The embedded atom method potential is used at the simulation of isobaric cooling. The viscosity is calculated using the Green–Kubo formula. The stress autocorrelation functions are obtained in the range 300-1200 K. The calculated kinematic viscosity is in agreement with the experimental data for the temperatures above melting temperature. The steep change of the shear viscosity is found below 650 K which we associate with the glass transition and is in a good agreement with the temperature which is obtained using the calorimetric criterion Kolotova et al (2015 J. Non-Cryst. Solids 429 98). The viscosity coefficient can not be calculated using the direct atomistic simulations below that temperature. (paper)

Open quantum system model of the one-dimensional Burgers equation with tunable shear viscosity

International Nuclear Information System (INIS)

Yepez, Jeffrey

2006-01-01

Presented is an analysis of an open quantum model of the time-dependent evolution of a flow field governed by the nonlinear Burgers equation in one spatial dimension. The quantum model is a system of qubits where there exists a minimum time interval in the time-dependent dynamics. Each temporally discrete unitary quantum-mechanical evolution is followed by state reduction of the quantum state. The mesoscopic behavior of this quantum model is described by a quantum Boltzmann equation with a naturally emergent entropy function and H theorem and the model obeys the detailed balance principle. The macroscopic-scale effective field theory for the quantum model is derived using a perturbative Chapman-Enskog expansion applied to the linearized quantum Boltzmann equation. The entropy function is consistent with the quantum-mechanical collision process and a Fermi-Dirac single-particle distribution function for the occupation probabilities of the qubit's energy eigenstates. Comparisons are presented between analytical predictions and numerical predictions and the agreement is excellent, indicating that the nonlinear Burgers equation with a tunable shear viscosity is the operative macroscopic scale effective field theory

Experimental density and viscosity measurements of di(2ethylhexyl)sebacate at high pressure

International Nuclear Information System (INIS)

Paredes, Xavier; Fandino, Olivia; Pensado, Alfonso S.; Comunas, Maria J.P.; Fernandez, Josefa

2012-01-01

Highlights: → We measure viscosities for di(2-ethylhexyl)sebacate from (298.15 to 398.15) K and up to 60 MPa. → We measure densities for DEHS from (298.15 to 373.15) K and from (0.1 to 60) MPa. → The reported and lit. data were used in a viscosity correlation from (273 to 491) K and up to 1.1 GPa. → This correlation could be used in industrial equipment that operate at high pressures. - Abstract: Experimental densities and dynamic viscosities of di(2-ethylhexyl)sebacate (DEHS) are the object of study in this work. DEHS could be a useful industrial reference fluid for moderately high viscosity at high pressures as it is often used as a pressure transmitting fluid. At atmospheric pressure the density and viscosity measurements have been performed in a rotational SVM 3000 Stabinger viscometer from (273.15 to 373.15) K, whereas from (0.1 to 60) MPa and from (298.15 to 398.15) K an automated Anton Paar DMA HPM vibrating-tube densimeter, and a high-pressure rolling-ball viscometer were used. Several Vogel-Fulcher-Tammann type equations were used to fit the experimental values of viscosity to the pressure and temperature. The measured viscosity data have been used together with previous data found in the literature to establish a correlation of the viscosity surface η(T, p) of DEHS, covering a temperature range from (273 to 491) K and pressure up to 1.1 GPa. This correlation could be used in industrial equipment like viscometers and other devices that operate at high pressures. Our viscosity data have also been fitted as a function of temperature and volume to the thermodynamic scaling model of Roland et al. [C.M. Roland, S. Bair, R. Casalini, J. Chem. Phys. 125 (2006) 124508].

Viscosity Measurements of SiO2-"FeO"-MgO System in Equilibrium with Metallic Fe

Science.gov (United States)

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2014-01-01

The present study delivers the measurements of viscosities in the SiO2-"FeO"-MgO system in equilibrium with metallic Fe. The rotational spindle technique was used for the measurements at the temperature range of 1523 K to 1773 K (1250 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The viscosity measurements were carried out at 31 to 47 mol pct SiO2 and up to 18.8 mol pct MgO. Analysis of the quenched sample by Electron probe X-ray microanalysis after the viscosity measurement enables the composition and microstructure of the slag to be directly linked with the viscosity. The replacement of "FeO" by MgO was found to increase viscosity and activation energy of the SiO2-"FeO"-MgO slags. The modified Quasi-chemical Viscosity Model was further optimized in this system based on the current viscosity measurements.

Viscosity Measurements of "FeO"-SiO2 Slag in Equilibrium with Metallic Fe

Science.gov (United States)

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2013-06-01

The current study delivered the measurements of viscosities in the system "FeO"-SiO2 in equilibrium with metallic Fe in the composition range between 15 and 40 wt pct SiO2. The experiments were carried out in the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C) using a rotational spindle technique. An analysis of the quenched sample by electron probe X-ray microanalysis (EPMA) after the viscosity measurement enables the composition and microstructure of the slag to be directly linked with the viscosity. The current results are compared with available literature data. The significant discrepancies of the viscosity measurements in this system have been clarified. The possible reasons affecting the accuracy of the viscosity measurement have been discussed. The activation energies derived from the experimental data have a sharp increase at about 33 wt pct SiO2, which corresponds to the composition of fayalite (Fe2SiO4). The modified quasi-chemical model was constructed in the system "FeO"-SiO2 to describe the current viscosity data.

Viscosity Measurement: A Virtual Experiment - Abstract of Issues 9907W

Science.gov (United States)

Papadopoulos, N.; Pitta, A. T.; Markopoulos, N.; Limniou, M.; Lemos, M. A. N. D. A.; Lemos, F.; Freire, F. G.

1999-11-01

Viscosity Measurement: A Virtual Experiment simulates a series of viscosity experiments. Viscosity is an important subject in chemistry and chemical engineering. It is important when dealing with intermolecular forces in liquids and gases and it has enormous relevance in all technological aspects of equipment dealing with liquids or gases. Most university-level chemistry courses include viscosity to some extent. Viscosity Measurement includes three virtual experiments: an Ostwald viscometer simulator, a falling-ball viscometer simulator, and a balance simulator for a simple determination of the density of a liquid. The Ostwald viscometer simulator and the balance simulator allow the student to find out how composition and temperature influence the density and viscosity of an ethanol-water mixture. The falling-ball viscometer simulator allows the student to determine experimentally the size and density of the ball required to measure viscosity of various liquids. Each virtual experiment includes a corresponding theoretical section. Support from the program is sufficient to enable the students to carry out a virtual experiment sensibly and on their own. Preparation is not essential. Students can use the program unsupervised, thus saving staff time and allowing flexibility in students' time. The design of the program interface plays a key role in the success of a simulated experiment. Direct manipulation has greater intuitive appeal than alternative interface forms such as menus and has been observed to provide performance and learning advantages (1). We tried to design an interface that is visually attractive, is user friendly with simple and intuitive navigation, and provides appropriate schematic animations to clarify the principles of the laboratory procedures. The opening screen presents the virtual experiments that can be selected. Clicking an icon takes the student to the appropriate section. Viscosity Measurement allows the student to concentrate on the

Viscosity and Liquid Density of Asymmetric n-Alkane Mixtures: Measurement and Modelling

DEFF Research Database (Denmark)

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 a vibrating U-tube densimeter. Pure component results agreed, oil average, with literature values within 0.2% for liquid density and 3% for viscosity. The measured data were used to evaluate the performance of two models for their predictions: the friction theory coupled with the Peng-Robinson equation...... 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....

Imaging the Microscopic Structure of Shear Thinning and Thickening Colloidal Suspensions

KAUST Repository

Cheng, X.

2011-09-01

The viscosity of colloidal suspensions varies with shear rate, an important effect encountered in many natural and industrial processes. Although this non-Newtonian behavior is believed to arise from the arrangement of suspended particles and their mutual interactions, microscopic particle dynamics are difficult to measure. By combining fast confocal microscopy with simultaneous force measurements, we systematically investigate a suspension\\'s structure as it transitions through regimes of different flow signatures. Our measurements of the microscopic single-particle dynamics show that shear thinning results from the decreased relative contribution of entropic forces and that shear thickening arises from particle clustering induced by hydrodynamic lubrication forces. This combination of techniques illustrates an approach that complements current methods for determining the microscopic origins of non-Newtonian flow behavior in complex fluids.

Viscosity and transient electric birefringence study of clay colloidal aggregation.

Science.gov (United States)

Bakk, Audun; Fossum, Jon O; da Silva, Geraldo J; Adland, Hans M; Mikkelsen, Arne; Elgsaeter, Arnljot

2002-02-01

We study a synthetic clay suspension of laponite at different particle and NaCl concentrations by measuring stationary shear viscosity and transient electrically induced birefringence (TEB). On one hand the viscosity data are consistent with the particles being spheres and the particles being associated with large amount bound water. On the other hand the viscosity data are also consistent with the particles being asymmetric, consistent with single laponite platelets associated with a very few monolayers of water. We analyze the TEB data by employing two different models of aggregate size (effective hydrodynamic radius) distribution: (1) bidisperse model and (2) log-normal distributed model. Both models fit, in the same manner, fairly well to the experimental TEB data and they indicate that the suspension consists of polydisperse particles. The models also appear to confirm that the aggregates increase in size vs increasing ionic strength. The smallest particles at low salt concentrations seem to be monomers and oligomers.

Rheo-SAXS investigation of shear-thinning behaviour of very anisometric repulsive disc-like clay suspensions.

Science.gov (United States)

Philippe, A M; Baravian, C; Imperor-Clerc, M; De Silva, J; Paineau, E; Bihannic, I; Davidson, P; Meneau, F; Levitz, P; Michot, L J

2011-05-18

Aqueous suspensions of swelling clay minerals exhibit a rich and complex rheological behaviour. In particular, these repulsive systems display strong shear-thinning at very low volume fractions in both the isotropic and gel states. In this paper, we investigate the evolution with shear of the orientational distribution of aqueous clay suspensions by synchrotron-based rheo-SAXS experiments using a Couette device. Measurements in radial and tangential configurations were carried out for two swelling clay minerals of similar morphology and size, Wyoming montmorillonite and Idaho beidellite. The shear evolution of the small angle x-ray scattering (SAXS) patterns displays significantly different features for these two minerals. The detailed analysis of the angular dependence of the SAXS patterns in both directions provides the average Euler angles of the statistical effective particle in the shear plane. We show that for both samples, the average orientation is fully controlled by the local shear stress around the particle. We then apply an effective approach to take into account multiple hydrodynamic interactions in the system. Using such an approach, it is possible to calculate the evolution of viscosity as a function of shear rate from the knowledge of the average orientation of the particles. The viscosity thus recalculated almost perfectly matches the measured values as long as collective effects are not too important in the system.

Rheo-SAXS investigation of shear-thinning behaviour of very anisometric repulsive disc-like clay suspensions

International Nuclear Information System (INIS)

Philippe, A M; Baravian, C; Imperor-Clerc, M; De Silva, J; Davidson, P; Paineau, E; Bihannic, I; Michot, L J; Meneau, F; Levitz, P

2011-01-01

Aqueous suspensions of swelling clay minerals exhibit a rich and complex rheological behaviour. In particular, these repulsive systems display strong shear-thinning at very low volume fractions in both the isotropic and gel states. In this paper, we investigate the evolution with shear of the orientational distribution of aqueous clay suspensions by synchrotron-based rheo-SAXS experiments using a Couette device. Measurements in radial and tangential configurations were carried out for two swelling clay minerals of similar morphology and size, Wyoming montmorillonite and Idaho beidellite. The shear evolution of the small angle x-ray scattering (SAXS) patterns displays significantly different features for these two minerals. The detailed analysis of the angular dependence of the SAXS patterns in both directions provides the average Euler angles of the statistical effective particle in the shear plane. We show that for both samples, the average orientation is fully controlled by the local shear stress around the particle. We then apply an effective approach to take into account multiple hydrodynamic interactions in the system. Using such an approach, it is possible to calculate the evolution of viscosity as a function of shear rate from the knowledge of the average orientation of the particles. The viscosity thus recalculated almost perfectly matches the measured values as long as collective effects are not too important in the system.

Improved viscosity modeling in patients with type 2 diabetes mellitus by accounting for enhanced red blood cell aggregation tendency

NARCIS (Netherlands)

Mutsaerts, Henri J. M. M.; Out, Mattijs; Goedhart, Peter T.; Ince, Can; Hardeman, Max R.; Romijn, Johannes A.; Rabelink, Ton J.; Reiber, Johan H. C.; Box, Frieke M. A.

2010-01-01

Aims: Distorted wall shear stress (WSS) in patients with type 2 diabetes mellitus (T2DM) may be partly explained by an altered red blood cell aggregation tendency (RAT) on viscosity at low shear rate (SR). The present study evaluates viscosity modeling by implementation of hematocrit and RAT in

On the measurement of magnetic viscosity

Science.gov (United States)

Serletis, C.; Efthimiadis, K. G.

2012-08-01

This work is an investigation of the experimental method used for measuring the magnetic viscosity in a hard ferromagnetic material, i.e. the recording of the magnetization under constant applied field and temperature, after the material has been magnetically saturated. It investigates how the experimental results are affected by the initial conditions of the method (saturation field, field change rate and field oscillation prior to its stabilization), and by minor variations of field and temperature during the recording. Based on the arising conclusions and the use of a more complex fitting function of measurements, the accuracy and repeatability of experimental results is improved.

Mean wall-shear stress measurements using the micro-pillar shear-stress sensor MPS3

International Nuclear Information System (INIS)

Große, S; Schröder, W

2008-01-01

A new sensor to measure the mean turbulent wall-shear stress in turbulent flows is described. The wall-shear stress sensor MPS 3 has been tested in a well-defined fully developed turbulent pipe flow at Reynolds numbers Re b based on the bulk velocity U b and the pipe diameter D in the range of Re b = 10 000–20 000. The results demonstrate a convincing agreement of the mean wall-shear stress obtained with the new sensor technique with analytical and experimental results from the literature. The sensor device consists of a flexible micro-pillar that extends from the wall into the viscous sublayer. Bending due to the exerting fluid forces, the pillar-tip deflection serves as a measure for the local wall-shear stress. The sensor concept, calibration techniques, the achievable accuracy and error estimates, the fields of application and the sensor limits will be discussed. Furthermore, a first estimate of the pillar dynamic response will be derived showing the potential of the sensor to also measure the turbulent fluctuating wall-shear stress

Stress relaxation of shear in metals during shock loading

International Nuclear Information System (INIS)

Glazyrin, V.P.; Platova, T.M.

1988-01-01

Constructed determining equation, taking into account stress relaxation of shear, was used to calculate the evolution of plane shock waves of primary and secondary compression in metals. Values of shear stress and viscosity coefficient were

Boundary Effects and Shear Thickening of Colloidal Suspensions: A study based on measurement of Suspension Microstructure

Science.gov (United States)

Perera, M. Tharanga D.

Microstructure is key to understanding rheological behaviors of flowing particulate suspensions. During the past decade, Stokesian Dynamics simulations have been the dominant method of determining suspension microstructure. Structure results obtained numerically reveal that an anisotropic structure is formed under high Peclet (Pe) number conditions. Researchers have used various experimental techniques such as small angle neutron scattering (SANS) and light scattering methods to validate microstructure. This work outlines an experimental technique based on confocal microscopy to study microstructure of a colloidal suspension in an index-matched fluid flowing in a microchannel. High resolution scans determining individual particle locations in suspensions 30-50 vol % yield quantitative results of the local microstructure in the form of the pair distribution function, g(r). From these experimentally determined g(r), the effect of shear rate, quantified by the Peclet number as a ratio of shear and Brownian stress, on the suspension viscosity and normal stress follow that seen in macroscopic rheological measurements and simulations. It is generally believed that shear thickening behavior of colloidal suspensions is driven by the formation of hydroclusters. From measurements of particle locations, hydroclusters are identified. The number of hydroclusters grows exponentially with increasing Pe, and the onset of shear thickening is driven by the increase in formation of clusters having 5-8 particles. At higher Pe, we notice the emergence of 12 or more particle clusters. The internal structure of these hydroclusters has been investigated, and there is some evidence that particles internal to hydroclusters preferentially align along the 45° and 135° axis. Beyond observations of bulk suspension behavior, the influence of boundaries on suspension microstructure is also investigated. Experiments were performed for suspensions flowing over smooth walls, made of glass

Non-Invasive Diagnostics for Measuring Physical Properties and Processes in High Level Wastes

International Nuclear Information System (INIS)

Robert Powell; David Pfund

2005-01-01

This research demonstrated the usefulness of tomographic techniques for determining the physical properties of slurry suspensions. Of particular interest was the measurement of the viscosity of suspensions in complex liquids and modeling these. We undertook a long rage program that used two techniques, magnetic resonance imaging and ultrasonic pulsed Doppler velocimetry. Our laboratory originally developed both of these for the measurement of viscosity of complex liquids and suspensions. We have shown that the relationship between shear viscosity and shear rate can be determined over a wide range of shear rates from a single measurement. We have also demonstrated these techniques for many non-Newtonian fluids which demonstrate highly shear thinning behavior. This technique was extended to determine the yield stress with systems of interacting particles. To model complex slurries that may be found in wastes applications, we have also used complex slurries that are found in industrial applications

Aspiration of human neutrophils: effects of shear thinning and cortical dissipation.

Science.gov (United States)

Drury, J L; Dembo, M

2001-12-01

It is generally accepted that the human neutrophil can be mechanically represented as a droplet of polymeric fluid enclosed by some sort of thin slippery viscoelastic cortex. Many questions remain however about the detailed rheology and chemistry of the interior fluid and the cortex. To address these quantitative issues, we have used a finite element method to simulate the dynamics of neutrophils during micropipet aspiration using various plausible assumptions. The results were then systematically compared with aspiration experiments conducted at eight different combinations of pipet size and pressure. Models in which the cytoplasm was represented by a simple Newtonian fluid (i.e., models without shear thinning) were grossly incapable of accounting for the effects of pressure on the general time scale of neutrophil aspiration. Likewise, models in which the cortex was purely elastic (i.e., models without surface viscosity) were unable to explain the effects of pipet size on the general aspiration rate. Such models also failed to explain the rapid acceleration of the aspiration rate during the final phase of aspiration nor could they account for the geometry of the neutrophil during various phases of aspiration. Thus, our results indicate that a minimal mechanical model of the neutrophil needs to incorporate both shear thinning and surface viscosity to remain valid over a reasonable range of conditions. At low shear rates, the surface dilatation viscosity of the neutrophil was found to be on the order of 100 poise-cm, whereas the viscosity of the interior cytoplasm was on the order of 1000 poise. Both the surface viscosity and the interior viscosity seem to decrease in a similar fashion when the shear rate exceeds approximately 0.05 s(-1). Unfortunately, even models with both surface viscosity and shear thinning studied are still not sufficient to fully explain all the features of neutrophil aspiration. In particular, the very high rate of aspiration during the

Exact solutions for oscillatory shear sweep behaviors of complex fluids from the Oldroyd 8-constant framework

Science.gov (United States)

Saengow, Chaimongkol; Giacomin, A. Jeffrey

2018-03-01

In this paper, we provide a new exact framework for analyzing the most commonly measured behaviors in large-amplitude oscillatory shear flow (LAOS), a popular flow for studying the nonlinear physics of complex fluids. Specifically, the strain rate sweep (also called the strain sweep) is used routinely to identify the onset of nonlinearity. By the strain rate sweep, we mean a sequence of LAOS experiments conducted at the same frequency, performed one after another, with increasing shear rate amplitude. In this paper, we give exact expressions for the nonlinear complex viscosity and the corresponding nonlinear complex normal stress coefficients, for the Oldroyd 8-constant framework for oscillatory shear sweeps. We choose the Oldroyd 8-constant framework for its rich diversity of popular special cases (we list 18 of these). We evaluate the Fourier integrals of our previous exact solution to get exact expressions for the real and imaginary parts of the complex viscosity, and for the complex normal stress coefficients, as functions of both test frequency and shear rate amplitude. We explore the role of infinite shear rate viscosity on strain rate sweep responses for the special case of the corotational Jeffreys fluid. We find that raising η∞ raises the real part of the complex viscosity and lowers the imaginary. In our worked examples, we thus first use the corotational Jeffreys fluid, and then, for greater accuracy, we use the Johnson-Segalman fluid, to describe the strain rate sweep response of molten atactic polystyrene. For our comparisons with data, we use the Spriggs relations to generalize the Oldroyd 8-constant framework to multimode. Our generalization yields unequivocally, a longest fluid relaxation time, used to assign Weissenberg and Deborah numbers to each oscillatory shear flow experiment. We then locate each experiment in the Pipkin space.

Using Quartz Crystal Microbalance for Field Measurement of Liquid Viscosities

Directory of Open Access Journals (Sweden)

Qingsong Bai

2016-01-01

Full Text Available The field measurement of liquid viscosities, especially the high viscous liquids, is challenging and often requires expensive equipment, long processing time, and lots of reagent. We use quartz crystal microbalances (QCMs operating in solution which are also sensitive to the viscosity and density of the contacting solution. QCMs are typically investigated for sensor applications in which one surface of QCM completely immersed in Newtonian liquid, but the viscous damping in liquids would cause not only large frequency shifts but also large losses in the quality factor Q leading to instability and even cessation of oscillation. A novel mass-sensitivity-based method for field measurement of liquid viscosities using a QCM is demonstrated in this paper and a model describing the influence of the liquid properties on the oscillation frequency is established as well. Two groups of verified experiments were performed and the experimental results show that the presented method is effective and possesses potential applications.

Pharmaceutical grade phyllosilicate dispersions: the influence of shear history on floc structure.

Science.gov (United States)

Viseras, C; Meeten, G H; Lopez-Galindo, A

1999-05-10

The effect of mixing conditions on the flow curves of some clay-water dispersions was studied. Two Spanish fibrous phyllosilicates (sepiolite from Vicálvaro and palygorskite from Turón) and a commercial bentonite (Bentopharm Copyright, UK) were selected as model clays. The disperse systems were made up using a rotor-stator mixer working at two different mixing rates (1000 and 8000 rpm), for periods of 1 and 10 min. Rheological measurements were taken and the corresponding flow curves obtained immediately after interposition and then after a period of 24 h under low shear caused by a roller apparatus. Aqueous sepiolite dispersions showed the highest viscosity and were easily interposed, whereas palygorskite dispersions were more difficult to obtain, resulting in low to medium viscosity gels. Bentonite dispersions provided medium viscosity systems, which greatly increased their viscosity after the low shear treatment (as a result of swelling), whereas the viscosity of the fibrous clays stayed at approximately the same values or even decreased. A linear relation was found between mixing energy and apparent viscosity in the bentonite systems, while apparent viscosity in the sepiolite samples was related to mixing power, with minor influence of mixing times. All the systems studied had thixotropic behaviour, changing from clearly positive to even negative thixotropy in some palygorskite systems. Finally, we studied the effect of drastic pH changes on the system structure. Results showed that rheological properties were highly sensitive to pH in the fibrous dispersions, but less sensitive behaviour was found in the laminar clay systems. Copyright.

Flexible Micropost Arrays for Shear Stress Measurement

Science.gov (United States)

Wohl, Christopher J.; Palmieri, Frank L.; Hopkins, John W.; Jackson, Allen M.; Connell, John W.; Lin, Yi; Cisotto, Alexxandra A.

2015-01-01

Increased fuel costs, heightened environmental protection requirements, and noise abatement continue to place drag reduction at the forefront of aerospace research priorities. Unfortunately, shortfalls still exist in the fundamental understanding of boundary-layer airflow over aerodynamic surfaces, especially regarding drag arising from skin friction. For example, there is insufficient availability of instrumentation to adequately characterize complex flows with strong pressure gradients, heat transfer, wall mass flux, three-dimensionality, separation, shock waves, and transient phenomena. One example is the acoustic liner efficacy on aircraft engine nacelle walls. Active measurement of shear stress in boundary layer airflow would enable a better understanding of how aircraft structure and flight dynamics affect skin friction. Current shear stress measurement techniques suffer from reliability, complexity, and airflow disruption, thereby compromising resultant shear stress data. The state-of-the-art for shear stress sensing uses indirect or direct measurement techniques. Indirect measurements (e.g., hot-wire, heat flux gages, oil interferometry, laser Doppler anemometry, small scale pressure drag surfaces, i.e., fences) require intricate knowledge of the studied flow, restrictive instrument arrangements, large surface areas, flow disruption, or seeding material; with smaller, higher bandwidth probes under development. Direct measurements involve strain displacement of a sensor element and require no prior knowledge of the flow. Unfortunately, conventional "floating" recessed components for direct measurements are mm to cm in size. Whispering gallery mode devices and Fiber Bragg Gratings are examples of recent additions to this type of sensor with much smaller (?m) sensor components. Direct detection techniques are often single point measurements and difficult to calibrate and implement in wind tunnel experiments. In addition, the wiring, packaging, and installation

Measurement of changes in viscosity in polymers with gamma-ray dose using a differential viscometer

International Nuclear Information System (INIS)

Santra, L.; Bhaumik, D.; Roy, S.C.

1988-01-01

Although some works on changes in viscosity of liquids with gamma-ray dose have been made near the ''gel point'', very little works have been done bellow this point. Changes in viscosities of different-grade silicone fluids below gel point have been measured using a differential viscometer developed in our laboratory, capable of measuring change in viscosities of two liquids directly. Preliminary results on viscosity changes when irradiated with energetic alpha particles will also be reported [pt

Measurement of changes in viscosity in polymers with gamma-ray dose using a differential viscometer

International Nuclear Information System (INIS)

Santra, L.; Bhaumik, D.; Roy, S.C.

1989-01-01

Although some works on changes in viscosity of liquids with gamma-ray dose have been made near the 'gel point', very little works have been done below this point. Changes in viscosities of different-grade silicone fluids below gel point have been measured using a differential viscometer developed in our laboratory, capable of measuring change in viscosities of two liquids directly. Preliminary results on viscosity changes when irradiated with energetic alpha particles will also be reported. (orig.)

The rheological properties of shear thickening fluid reinforced with SiC nanowires

Directory of Open Access Journals (Sweden)

Jianhao Ge

Full Text Available The rheological properties of shear thickening fluid (STF reinforced with SiC nanowires were investigated in this paper. Pure STF consists of 56 vol% silica nano-particles and polyethylene glycol 400 (PEG 400 solvent was fabricated; and a specific amount of SiC nanowires were dispersed into this pure STF, and then the volume fraction of PEG400 was adjusted to maintain the volume fraction of solid phase in the STF at a constant of 56%. The results showed there was almost 30% increase in the initial and shear thickening viscosity of the STF reinforced with SiC nanowires compared to the pure STF. Combining with the hydrodynamic cluster theory, the effect of the mechanism of SiC nanowire on the viscosity of STF was discussed, and based on the experimental results, an analytical model of viscosity was used to describe the rheological properties of STF, which agreed with the experimental results. Keywords: Shear thickening fluid (STF, Nanowire, Rheology, Viscosity, Analytical model

The influence of viscosity stratification on boundary-layer turbulence

Science.gov (United States)

Lee, Jin; Jung, Seo Yoon; Sung, Hyung Jin; Zaki, Tamer A.

2012-11-01

Direct numerical simulations of turbulent flows over isothermally-heated walls were performed to investigate the influence of viscosity stratification on boundary-layer turbulence and drag. The adopted model for temperature-dependent viscosity was typical of water. The free-stream temperature was set to 30°C, and two wall temperatures, 70°C and 99°C, were simulated. In the heated flows, the mean shear-rate is enhanced near the wall and reduced in the buffer region, which induces a reduction in turbulence production. On the other hand, the turbulence dissipation is enhanced near the wall, despite the the reduction in fluid viscosity. The higher dissipation is attributed to a decrease in the smallest length scales and near-wall fine-scale motions. The combined effect of the reduced production and enhanced dissipation leads to lower Reynolds shear stresses and, as a result, reduction of the skin-friction coefficient. Supported by the Engineering and Physical Sciences Research Council (Grant EP/F034997/1) and partially supported by the Erasmus Mundus Build on Euro-Asian Mobility (EM-BEAM) programme.

Simultaneous viscosity and density measurement of small volumes of liquids using a vibrating microcantilever.

Science.gov (United States)

Payam, A F; Trewby, W; Voïtchovsky, K

2017-05-02

Many industrial and technological applications require precise determination of the viscosity and density of liquids. Such measurements can be time consuming and often require sampling substantial amounts of the liquid. These problems can partly be overcome with the use of microcantilevers but most existing methods depend on the specific geometry and properties of the cantilever, which renders simple, accurate measurement difficult. Here we present a new approach able to simultaneously quantify both the density and the viscosity of microliters of liquids. The method, based solely on the measurement of two characteristic frequencies of an immersed microcantilever, is completely independent of the choice of a cantilever. We derive analytical expressions for the liquid's density and viscosity and validate our approach with several simple liquids and different cantilevers. Application of our model to non-Newtonian fluids shows that the calculated viscosities are remarkably robust when compared to measurements obtained from a standard rheometer. However, the results become increasingly dependent on the cantilever geometry as the frequency-dependent nature of the liquid's viscosity becomes more significant.

Detection of irradiated peppers by viscosity measurement at extremely high pH

International Nuclear Information System (INIS)

Hayashi, Toru; Todoriki, Setsuko

1996-01-01

The viscosities of aqueous suspensions of irradiated peppers determined after heat gelatinization were influenced by the pH of the suspension to a greater degree than those of unirradiated ones. Viscosity measurement under an extremely alkaline condition (pH 13.8) resulted in a significant different between irradiated peppers and unirradiated ones, irrespective of the planting locality and storage period. All of the pepper samples irradiated at 5 kGy showed viscosity values significantly lower than unirradiated ones. (Author)

Shear and extensional properties of kefiran.

Science.gov (United States)

Piermaría, Judith; Bengoechea, Carlos; Abraham, Analía Graciela; Guerrero, Antonio

2016-11-05

Kefiran is a neutral polysaccharide constituted by glucose and galactose produced by Lactobacillus kefiranofaciens. It is included into kefir grains and has several health promoting properties. In the present work, shear and extensional properties of different kefiran aqueous dispersions (0.5, 1 and 2% wt.) were assessed and compared to other neutral gums commonly used in food, cosmetic and pharmaceutics industries (methylcellulose, locust bean gum and guar gum). Kefiran showed shear flow characteristics similar to that displayed by other representative neutral gums, although it always yielded lower viscosities at a given concentration. For each gum system it was possible to find a correlation between dynamic and steady shear properties by a master curve including both the apparent and complex viscosities. When studying extensional properties of selected gums at 2% wt. by means of a capillary break-up rheometer, kefiran solutions did not show important extensional properties, displaying a behaviour close the Newtonian. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermal conductivity as influenced by the temperature and apparent viscosity of dairy products.

Science.gov (United States)

Gonçalves, B J; Pereira, C G; Lago, A M T; Gonçalves, C S; Giarola, T M O; Abreu, L R; Resende, J V

2017-05-01

This study aimed to evaluate the rheological behavior and thermal conductivity of dairy products, composed of the same chemical components but with different formulations, as a function of temperature. Subsequently, thermal conductivity was related to the apparent viscosity of yogurt, fermented dairy beverage, and fermented milk. Thermal conductivity measures and rheological tests were performed at 5, 10, 15, 20, and 25°C using linear probe heating and an oscillatory rheometer with concentric cylinder geometry, respectively. The results were compared with those calculated using the parallel, series, and Maxwell-Eucken models as a function of temperature, and the discrepancies in the results are discussed. Linear equations were fitted to evaluate the influence of temperature on the thermal conductivity of the dairy products. The rheological behavior, specifically apparent viscosity versus shear rate, was influenced by temperature. Herschel-Bulkley, power law, and Newton's law models were used to fit the experimental data. The Herschel-Bulkley model best described the adjustments for yogurt, the power law model did so for fermented dairy beverages, and Newton's law model did so for fermented milk and was then used to determine the rheological parameters. Fermented milk showed a Newtonian trend, whereas yogurt and fermented dairy beverage were shear thinning. Apparent viscosity was correlated with temperature by the Arrhenius equation. The formulation influenced the effective thermal conductivity. The relationship between the 2 properties was established by fixing the temperature and expressing conductivity as a function of apparent viscosity. Thermal conductivity increased with viscosity and decreased with increasing temperature. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Practical Weak-lensing Shear Measurement with Metacalibration

Energy Technology Data Exchange (ETDEWEB)

Sheldon, Erin S. [Brookhaven National Laboratory, Bldg. 510, Upton, NY 11973 (United States); Huff, Eric M. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States)

2017-05-20

Metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observe that for images with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measured galaxy properties to induce significant selection effects. Using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.

Application of SH surface acoustic waves for measuring the viscosity of liquids in function of pressure and temperature.

Science.gov (United States)

Kiełczyński, P; Szalewski, M; Balcerzak, A; Rostocki, A J; Tefelski, D B

2011-12-01

Viscosity measurements were carried out on triolein at pressures from atmospheric up to 650 MPa and in the temperature range from 10°C to 40°C using ultrasonic measuring setup. Bleustein-Gulyaev SH surface acoustic waves waveguides were used as viscosity sensors. Additionally, pressure changes occurring during phase transition have been measured over the same temperature range. Application of ultrasonic SH surface acoustic waves in the liquid viscosity measurements at high pressure has many advantages. It enables viscosity measurement during phase transitions and in the high-pressure range where the classical viscosity measurement methods cannot operate. Measurements of phase transition kinetics and viscosity of liquids at high pressures and various temperatures (isotherms) is a novelty. The knowledge of changes in viscosity in function of pressure and temperature can help to obtain a deeper insight into thermodynamic properties of liquids. Copyright © 2011 Elsevier B.V. All rights reserved.

Changes in nucleoid viscosity following X-irradiation of rat thymic and splenic cells in vitro

International Nuclear Information System (INIS)

Tempel, K.

1990-01-01

In the present investigations, damage and repair of DNA supercoiling was measured in T- and S-cells following X-irradiation in vitro by using the nucleoid sedimentation technique and a simplified low-shearing viscometric test. - X-irradiation resulted in a dose(0.6-19.2 Gy)-dependent reduction in sedimentation and viscosity of nucleoids. Within a post-irradiation period of 30-45 min after a challenge dose of 19.2 Gy, DNA repair was accompanied by an increase in nucleoid sedimentation and viscosity in T-cells by about 60 and 300, in S-cells by almost 40 and 100%, resp. The increase in nucleoid viscosity within a 30 min repair period could be reduced in a concentration-dependent manner by DNA polymerase-inhibitors and proteinase K. - The higher DNA repair capacity of T-cells as reflected by UDS is confirmed therefore by the nucleoid characteristics. A part from this suggestion, measuring nucleoid viscosity may be considered as a sensitive, simple and rapid device to detect radiation-induced DNA supercoiling phenomena. (orig./MG)

Nonlinear damping for vibration isolation of microsystems using shear thickening fluid

Science.gov (United States)

Iyer, S. S.; Vedad-Ghavami, R.; Lee, H.; Liger, M.; Kavehpour, H. P.; Candler, R. N.

2013-06-01

This work reports the measurement and analysis of nonlinear damping of micro-scale actuators immersed in shear thickening fluids (STFs). A power-law damping term is added to the linear second-order model to account for the shear-dependent viscosity of the fluid. This nonlinear model is substantiated by measurements of oscillatory motion of a torsional microactuator. At high actuation forces, the vibration velocity amplitude saturates. The model accurately predicts the nonlinear damping characteristics of the STF using a power-law index extracted from independent rheology experiments. This result reveals the potential to use STFs as adaptive, passive dampers for vibration isolation of microelectromechanical systems.

On-line slurry viscosity and concentration measurement as a real-time waste stream characterization tool. 1998 annual progress report

International Nuclear Information System (INIS)

Powell, R.L.

1998-01-01

flow. Pressure drops will also be recorded to obtain shear stress distribution. Plot of shear stress versus the shear rate, obtained from the velocity profile, will yield the shear viscosity over a wide range of shear rate. The velocity images will also be analyzed to compare the effects of fluctuations with those of turbulent flow experiments For single phase fluids, the NMRI and the UDV work will be compared with measurements using LAV. In their LAV, flow apparatus, the working fluid, water, is gravity fed from a reservoir into a horizontal one inch Pyrex tube, 180 diameters in length. The system enables traverses of the optical probe in the horizontal and vertical directions, with a resolution of 200 micrometers. Radial distributions of the axial component of velocity were obtained at a location 150 diameters from the tube entrance. Measurements in the laminar regime indicate a precision of within one percent, as indicated by the root mean square fluctuations. In the turbulent regime, radial profiles of the mean and fluctuation velocities agree with literature values. In the laminar regime, symmetry of the radial velocity distribution was observed in the horizontal plane passing through the axis, but was not in general observed in the vertical plane passing through the axis. Further investigation revealed that the asymmetry was a result of buoyancy due to heat transfer between the working fluid and the surroundings, even though the pipe was not actively heated or cooled. Temperature differences as little as 1 degree Celsius were found to result in significant asymmetry. To have a reproducible result in the laminar regime, it was necessary to control the reservoir temperature to within 0.1 degree Celsius.'

Study of thermal and chemical effects on cellulase enzymes: Viscosity measurements

International Nuclear Information System (INIS)

Ghaouar, N.; Aschi, A.; Belbahri, L.; Trabelsi, S.; Gharbi, A.

2009-01-01

The behaviour of cellulase enzymes in phosphate saline buffer has been studied over a wide range of temperatures and enzyme concentrations by using viscosity measurements. To characterize the conformation change of cellulase versus temperature and chemical denaturants, such as guanidinium chloride (GdmCl) and urea, the information about the intrinsic viscosity and the hydrodynamic radius are necessary. The dependence of the intrinsic viscosity and the hydrodynamic radius in its random coil conformation on temperature and denaturant concentration were studied. Our results and discussions are limited to the dilute regime of concentration because of abnormalities in conformation observed in the very dilute regime due to the presence of capillary absorption effects.

Study of thermal and chemical effects on cellulase enzymes: Viscosity measurements

Energy Technology Data Exchange (ETDEWEB)

Ghaouar, N., E-mail: naoufel-ghaouar@lycos.co [Laboratoire de Physique de la Matiere Molle, Faculte des Sciences de Tunis, Campus Universitaire, 2092 (Tunisia); Institut National des Sciences Appliquees et de Technologie, INSAT, Centre Urbain Nord, BP. 676, Tunis (Tunisia); Aschi, A. [Laboratoire de Physique de la Matiere Molle, Faculte des Sciences de Tunis, Campus Universitaire, 2092 (Tunisia); Belbahri, L. [Agronomy Department, School of Engineering of Lullier, University of Applied Sciences of Western Switzerland, 150, Route de Presinge, 1254 Jussy (Switzerland); Trabelsi, S.; Gharbi, A. [Laboratoire de Physique de la Matiere Molle, Faculte des Sciences de Tunis, Campus Universitaire, 2092 (Tunisia)

2009-11-15

The behaviour of cellulase enzymes in phosphate saline buffer has been studied over a wide range of temperatures and enzyme concentrations by using viscosity measurements. To characterize the conformation change of cellulase versus temperature and chemical denaturants, such as guanidinium chloride (GdmCl) and urea, the information about the intrinsic viscosity and the hydrodynamic radius are necessary. The dependence of the intrinsic viscosity and the hydrodynamic radius in its random coil conformation on temperature and denaturant concentration were studied. Our results and discussions are limited to the dilute regime of concentration because of abnormalities in conformation observed in the very dilute regime due to the presence of capillary absorption effects.

Hydrodynamic radii of polyethylene glycols in different solvents determined from viscosity measurements

NARCIS (Netherlands)

Dohmen-Speelmans, M.P.J.; Pereira, A.M.; Timmer, J.M.K.; Benes, N.E.; Keurentjes, J.T.F.

2008-01-01

The hydrodynamic radius, rh, of low molar mass polyethylene glycol, MPEG = (200 to 1000) g·mol-1, in a homologous series of primary alcohols, acetone, and toluene has been determined from viscosity measurements. The viscosity data have been collected using a fast one-point method as well as a more

Viscosity and attenuation of sound wave in high density deuterium

International Nuclear Information System (INIS)

Inoue, Kazuko; Ariyasu, Tomio

1985-01-01

The penetration of low frequency sound wave into the fuel deuterium is discussed as for laser fusion. The sound velocity and the attenuation constant due to viscosity are calculated for high density (n = 10 24 -- 10 27 cm -3 , T = 10 -1 -- 10 4 eV) deuterium. The shear viscosity of free electron gas and the bulk viscosity due to ion-ion interaction mainly contribute to the attenuation of sound wave. The sound wave of the frequency below 10 10 Hz can easily penetrate through the compressed fuel deuterium of diameter 1 -- 10 3 μm. (author)

Viscosities in the Gluon-Plasma within a Quasiparticle Model

CERN Document Server

Bluhm, M; Redlich, K

2009-01-01

A phenomenological quasiparticle model, featuring dynamically generated self-energies of excitation modes, successfully describes lattice QCD results relevant for the QCD equation of state and related quantities both at zero and non-zero net baryon density. Here, this model is extended to study bulk and shear viscosities of the gluon-plasma within an effective kinetic theory approach. In this way, the compatibility of the employed quasiparticle ansatz with the apparent low viscosities of the strongly coupled deconfined gluonic medium is shown.

Simultaneous measurement of surface tension and viscosity using freely decaying oscillations of acoustically levitated droplets

Science.gov (United States)

Kremer, J.; Kilzer, A.; Petermann, M.

2018-01-01

Oscillations of small liquid drops around a spherical shape have been of great interest to scientists measuring physical properties such as interfacial tension and viscosity, over the last few decades. A powerful tool for contactless positioning is acoustic levitation, which has been used to simultaneously determine the surface tension and viscosity of liquids at ambient pressure. In order to extend this acoustic levitation measurement method to high pressure systems, the method is first evaluated under ambient pressure. To measure surface tension and viscosity using acoustically levitated oscillating drops, an image analysis method has to be developed and factors which may affect measurement, such as sound field or oscillation amplitude, have to be analyzed. In this paper, we describe the simultaneous measurement of surface tension and viscosity using freely decaying shape oscillations of acoustically levitated droplets of different liquids (silicone oils AK 5 and AK 10, squalane, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol) in air. These liquids vary in viscosity from 2 to about 30 mPa s. An acoustic levitation system, including an optimized standing wave acoustic levitator and a high-speed camera, was used for this study. An image analysis was performed with a self-written Matlab® code. The frequency of oscillation and the damping constant, required for the determination of surface tension and viscosity, respectively, were calculated from the evolution of the equatorial and polar radii. The results and observations are compared to data from the literature in order to analyze the accuracy of surface tension and viscosity determination, as well as the effect of non-spherical drop shape or amplitude of oscillation on measurement.

Magnetically-charged black branes and viscosity/entropy ratios

Energy Technology Data Exchange (ETDEWEB)

Liu, Hai-Shan [Institute for Advanced Physics & Mathematics,Zhejiang University of Technology, Hangzhou 310023 (China); George P. & Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy,Texas A& M University, College Station, TX 77843 (United States); Lü, H. [Department of Physics, Beijing Normal University,Beijing 100875 (China); Pope, C.N. [George P. & Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy,Texas A& M University, College Station, TX 77843 (United States); DAMTP, Centre for Mathematical Sciences,Cambridge University, Wilberforce Road, Cambridge CB3 OWA (United Kingdom)

2016-12-19

We consider asymptotically-AdS n-dimensional black brane solutions in a theory of gravity coupled to a set of Np-form field strengths, in which the field strengths carry magnetic charges. For appropriately chosen charges, the metrics are isotropic in the (n−2) transverse directions. However, in general the field strength configurations break the full Euclidean symmetry of the (n−2)-dimensional transverse space, and the shear viscosity tensor in the dual theory is no longer isotropic. We study the linearised equations for transverse traceless metric perturbations in these backgrounds, and by employing the Kubo formula we obtain expressions for the ratios η/S of the shear viscosity components divided by the entropy density. We find that the KSS bound on the ratios η/S is generally violated in these solutions. We also extend the discussion by including a dilatonic scalar field in the theory, leading to solutions that are asymptotically Lifshitz with hyperscaling violation.

Triglyceride glucose index and common carotid wall shear stress.

Science.gov (United States)

Tripolino, Cesare; Irace, Concetta; Scavelli, Faustina B; de Franceschi, Maria S; Esposito, Teresa; Carallo, Claudio; Gnasso, Agostino

2014-02-01

Alterations in wall shear stress contribute to both clinical and subclinical atherosclerosis. Several conditions such as hypertension, diabetes, and obesity can impair shear stress, but the role of insulin resistance has never been investigated. The present study was designed to investigate whether insulin resistance assessed by TyG Index associates with wall shear stress in the common carotid artery. One hundred six individuals were enrolled. Blood pressure, lipids, glucose, and cigarette smoking were evaluated. TyG Index was calculated as log[fasting triglycerides × fasting glucose / 2]. Subjects underwent blood viscosity measurement and echo-Doppler evaluation of carotid arteries to calculate wall shear stress. The association between TyG Index and carotid wall shear stress was assessed by simple and multiple regression analyses. TyG Index was significantly and inversely associated with carotid wall shear stress both in simple (r = -0.44, P glucose greater than 100 mg/dL, and triglycerides greater than 150 mg/dL. The present findings suggest that increasing insulin resistance, as assessed by TyG Index, associates with atherosclerosis-prone shear stress reduction in the common carotid artery.

Experimental study on density, thermal conductivity, specific heat, and viscosity of water-ethylene glycol mixture dispersed with carbon nanotubes

Directory of Open Access Journals (Sweden)

Ganeshkumar Jayabalan

2017-01-01

Full Text Available This article presents the effect of adding multi wall carbon nanotubes (MWCNT in water – ethylene glycol mixture on density and various thermophysical properties such as thermal conductivity, specific heat and viscosity. Density of nanofluids was measured using standard volumetric flask method and the data showed a good agreement with the mixing theory. The maximum thermal conductivity enhancement of 11 % was noticed for the nanofluids with 0.9 wt. %. Due to lower specific heat of the MWCNT, the specific heat of the nanofluids decreased in proportion with the MWCNT concentration. The rheological analysis showed that the transition region from shear thinning to Newtonian extended to the higher shear stress range compared to that of base fluids. Viscosity ratio of the nanofluids augmented anomalously with respect to increase in temperature and about 2.25 fold increase was observed in the temperature range of 30 – 40 ˚C. The modified model of Maron and Pierce predicted the viscosity of the nanofluids with the inclusion of effect of aspect ratio of MWCNT and nanoparticle aggregates.

Scaling of turbulence spectra measured in strong shear flow near the Earth’s surface

Science.gov (United States)

Mikkelsen, T.; Larsen, S. E.; Jørgensen, H. E.; Astrup, P.; Larsén, X. G.

2017-12-01

Within the lowest kilometer of the Earth’s atmosphere, in the so-called atmospheric boundary layer, winds are often gusty and turbulent. Nearest to the ground, the turbulence is predominately generated by mechanical wall-bounded wind shear, whereas at higher altitudes turbulent mixing of heat and moisture also play a role. The variance (square of the standard deviation) of the fluctuation around the mean wind speed is a measure of the kinetic energy content of the turbulence. This kinetic energy can be resolved into the spectral distributions, or spectra, as functions of eddy size, wavenumber, or frequency. Spectra are derived from Fourier transforms of wind records as functions of space or time corresponding to wavenumber and frequency spectra, respectively. Atmospheric spectra often exhibit different subranges that can be distinguished and scaled by the physical parameters responsible for: (1) their generation; (2) the cascade of energy across the spectrum from large- to small-scale; and (3) the eventual decay of turbulence into heat owing to viscosity effects on the Kolmogorov microscale, in which the eddy size is only a fraction of a millimeter. This paper addresses atmospheric turbulence spectra in the lowest part of the atmospheric boundary layer—the so-called surface layer—where the wind shear is strong owing to the nonslip condition at the ground. Theoretical results dating back to Tchen’s early work in 1953 ‘on the spectrum of energy in turbulent shear flow’ led Tchen to predict a shear production subrange with a distinct inverse-linear power law for turbulence in a strongly sheared high-Reynolds number wall-bounded flow, as is encountered in the lowest sheared part of the atmospheric boundary layer, also known as the eddy surface layer. This paper presents observations of spectra measured in a meteorological mast at Høvsøre, Denmark, that support Tchen’s prediction of a shear production subrange following a distinct power law of degree -1

Living bacteria rheology: Population growth, aggregation patterns, and collective behavior under different shear flows

Science.gov (United States)

Patrício, P.; Almeida, P. L.; Portela, R.; Sobral, R. G.; Grilo, I. R.; Cidade, T.; Leal, C. R.

2014-08-01

The activity of growing living bacteria was investigated using real-time and in situ rheology—in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus—strain COL and its isogenic cell wall autolysis mutant, RUSAL9—were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage.

[Relations between plasma-erythrocyte viscosity factors and ESR].

Science.gov (United States)

Cortinovis, A; Crippa, A; Crippa, M; Bosoni, T; Moratti, R

1992-09-01

The ESR is usually put in relationship: to the real density of the RBCs (erythrocytes) (difference between the RBC specific gravity and the plasma one), and to the resistance that the RBCs meet moving in a medium, which is due to the plasma viscosity and to the total external RBC surface. When the RBCs take shape of aggregates, their external surface is decreased and ESR increases. The most important plasma factor causing changes in ESR is the fibrinogen level followed by the plasma globulins and by the products arising from the tissue damage. The resistance that the RBCs meet moving in the plasma is well expressed by the measurement of the plasma-RBC viscosity considering that is inclusive of both factors that are the plasma viscosity and the external RBC surface. The plasma-RBC viscosity is the resultant of several factors: Fa = Fb - Fe - Fs - Fm, were: Fa is the resultant, Fb the attracting forces due to the proteic macromolecules, Fe the repulsing forces due the negative charges. Fs the repulsing forces due to the shear-stress, Fm the force which opposes itself against the surface tension of the aggregation; it depends on the RBC morphology and on the RBC rigidity. The ESR has been recently used like an index of the RBC aggregation. The Authors study the relationship between several hemorheological parameters and the ESR in infective and inflammatory processes.(ABSTRACT TRUNCATED AT 250 WORDS)

On the behaviour of gelled fibre suspensions in steady shear

Energy Technology Data Exchange (ETDEWEB)

Wolf, Bettina [Unilever Corporate Research, Bedford (United Kingdom); University of Nottingham, Division of Food Sciences, Loughborough (United Kingdom); White, Duncan; Melrose, John R.; Frith, William J. [Unilever Corporate Research, Bedford (United Kingdom)

2007-03-15

The shear rheological properties of suspensions of gelled agar fibres in a low viscosity Newtonian matrix fluid were investigated. Two classes of fibres, low aspect ratio fibres and high aspect ratio fibres with an aspect ratio of the order of 10 and 100 respectively were included in the investigations. For all fibre phase volumes investigated, from as low as 0.01 upwards, the flow curves are characterised by an apparent yield stress followed by shear-thinning which was independent of the fibre aspect ratio. Based on our analysis of the flow curves, we conclude that the high aspect ratio fibres behave like flexible threads in contrast to the low aspect ratio fibres whose high shear relative viscosity is successfully described by a relation for long rigid rods. These findings are supported by flow visualisation using an optical shearing stage coupled to a light microscope. (orig.)

Determination of temperature dependant viscosity values of lubricants via simultaneous measurements of refractive index

International Nuclear Information System (INIS)

Yaltkaya, S.

2005-01-01

Viscosity is one of the most important parameter in rheological and tribological properties of fluids. The objective of this study is to obtain the viscosity values from the simultaneous refractive-index measurements of lubricants, simply by dipping the fiber-optic probe into the oil to be measured. Due to the fact that these parameters are temperature dependent, within the interval under consideration, oil heated up steadily while measuring the viscosity and refractive index at the same time. The refractive index sensor, the digital viscometer and the thermometer were connected to a PC via an analog to digital converter and the values were acquired at the same time. The fiber optic refractive index sensor has been designed in our laboratory. By utilising Fresnel's fundamental reflection law, the intensity of reflected light from boundary surface (optic fiber core-motor oil) was measured at 660 nm wavelength and then refractive index of the oil was calculated. The derived refractive index values were converted viscosity values that acquired by using the calibration equation. The viscometer, used during the study, was the rotational Brookfield type

A Study of Nonlinear Variable Viscosity in Finite-Length Tube with Peristalsis

Directory of Open Access Journals (Sweden)

Y. Abd Elmaboud

2014-01-01

Full Text Available Peristaltic motion of an incompressible Newtonian fluid with variable viscosity induced by periodic sinusoidal traveling wave propagating along the walls of a finite-length tube has been investigated. A perturbation method of solution is sought. The viscosity parameter α (α << 1 is chosen as a perturbation parameter and the governing equations are developed up to the first-order in the viscosity parameter (α. The analytical solution has been derived for the radial velocity at the tube wall, the axial pressure gradient across the length of the tube, and the wall shear stress under the assumption of low Reynolds number and long wavelength approximation. The impacts of physical parameters such as the viscosity and the parameter determining the shape of the constriction on the pressure distribution and on the wall shear stress for integral and non-integral number of waves are illustrated. The main conclusion that can be drawn out of this study is that the peaks of pressure fluctuate with time and attain different values with non-integral numbers of peristaltic waves. The considered problem is very applicable in study of biological flow and industrial flow.

High Resolution Shear Profile Measurements in Entangled Polymers

KAUST Repository

Hayes, Keesha A.; Buckley, Mark R.; Cohen, Itai; Archer, Lynden A.

2008-01-01

spanning a wide range of molecular weights and number of entanglements (8≤Z≤56), but reveal large differences between the imposed and measured shear rates. These findings disagree with recent reports that shear banding is a characteristic flow response

Thermal convection of viscoelastic shear-thinning fluids

International Nuclear Information System (INIS)

Albaalbaki, Bashar; Khayat, Roger E; Ahmed, Zahir U

2016-01-01

The Rayleigh–Bénard convection for non-Newtonian fluids possessing both viscoelastic and shear-thinning behaviours is examined. The Phan-Thien–Tanner (PTT) constitutive equation is implemented to model the non-Newtonian character of the fluid. It is found that while the shear-thinning and viscoelastic effects could annihilate one another for the steady roll flow, presence of both behaviours restricts the roll stability limit significantly compared to the cases when the fluid is either inelastic shear-thinning or purely viscoelastic with constant viscosity. (paper)

The shear and bulk relaxation times from the general correlation functions

Science.gov (United States)

Czajka, Alina; Jeon, Sangyong

2017-11-01

In this paper we present two quantum field theoretical analyses on the shear and bulk relaxation times. First, we discuss how to find Kubo formulas for the shear and the bulk relaxation times. Next, we provide results on the shear viscosity relaxation time obtained within the diagrammatic approach for the massless λϕ4 theory.

Behavior of pressure and viscosity at high densities for two-dimensional hard and soft granular materials

NARCIS (Netherlands)

Otsuki, Michio; Hayakawa, Hisao; Luding, Stefan

2010-01-01

The pressure and the viscosity in two-dimensional sheared granular assemblies are investigated numerically. The behavior of both pressure and viscosity is smoothly changing qualitatively when starting from a mono-disperse hard-disk system without dissipation and moving towards a system of (i)

Nuclear quadrupole relaxation and viscosity in liquid metals

International Nuclear Information System (INIS)

Schirmacher, W.

1976-01-01

It is shown that the nuclear quadrupole relaxation rate due to the molecular motions in liquid metals is related to the shear and bulk viscosity and hence to the absorption coefficient of ultrasound. Application of the 'extended liquid phonon' model of Ortoleva and Nelkin - which is the third of a series of continued-fraction-approximations for the van Hove neutron scattering function - gives a relation to the self diffusion constant. The predictions of the theory concerning the temperature dependence are compared with quadrupole relaxation measurements of Riegel et al. and Kerlin et al. in liquid gallium. Agreement is found only with the data of Riegel et al. (orig.) [de

Calibration and Measurement of the Viscosity of DWPF Start-Up Glass

International Nuclear Information System (INIS)

Schumacher, R.F.

2001-01-01

The Harrop, High-Temperature Viscometer has been in operation at the Savannah River Technology Center (SRTC) for several years and has proven itself to be reasonably accurate and repeatable. This is particularly notable when taking into consideration the small amount of glass required to make the viscosity determination. The volume of glass required is only 2.60 cc or about 6 to 7 grams of glass depending on the glass density. This may be compared to the more traditional viscosity determinations, which generally require between 100 to 1000 grams of glass. Before starting the present investigation, the unit was re-aligned and the furnace thermal gradients measured. The viscometer was again calibrated with available NIST Standard Reference Material glasses (717a and 710a) and a spindle constant equation was determined. Standard DWPF Waste Compliance Glasses (Purex, HM, and Batch 1) were used to provide additional verification for the determinations at low temperature. The Harrop, High-Temperature Viscometer was then used to determine the viscosity of three random samples of ground and blended DWPF, Black, Start -Up Frit, which were obtained from Pacific Northwest National Laboratory (PNNL). The glasses were in powder form and required melting prior to the viscosity determination. The results from this evaluation will be compared to ''Round Robin'' measurements from other DOE laboratories and a number of commercial laboratories

In vivo wall shear measurements within the developing zebrafish heart.

Directory of Open Access Journals (Sweden)

R Aidan Jamison

Full Text Available Physical forces can influence the embryonic development of many tissues. Within the cardiovascular system shear forces resulting from blood flow are known to be one of the regulatory signals that shape the developing heart. A key challenge in investigating the role of shear forces in cardiac development is the ability to obtain shear force measurements in vivo. Utilising the zebrafish model system we have developed a methodology that allows the shear force within the developing embryonic heart to be determined. Accurate wall shear measurement requires two essential pieces of information; high-resolution velocity measurements near the heart wall and the location and orientation of the heart wall itself. We have applied high-speed brightfield imaging to capture time-lapse series of blood flow within the beating heart between 3 and 6 days post-fertilization. Cardiac-phase filtering is applied to these time-lapse images to remove the heart wall and other slow moving structures leaving only the red blood cell movement. Using particle image velocimetry to calculate the velocity of red blood cells in different regions within the heart, and using the signal-to-noise ratio of the cardiac-phase filtered images to determine the boundary of blood flow, and therefore the position of the heart wall, we have been able to generate the necessary information to measure wall shear in vivo. We describe the methodology required to measure shear in vivo and the application of this technique to the developing zebrafish heart. We identify a reduction in shear at the ventricular-bulbar valve between 3 and 6 days post-fertilization and demonstrate that the shear environment of the ventricle during systole is constantly developing towards a more uniform level.

In vivo wall shear measurements within the developing zebrafish heart.

Science.gov (United States)

Jamison, R Aidan; Samarage, Chaminda R; Bryson-Richardson, Robert J; Fouras, Andreas

2013-01-01

Physical forces can influence the embryonic development of many tissues. Within the cardiovascular system shear forces resulting from blood flow are known to be one of the regulatory signals that shape the developing heart. A key challenge in investigating the role of shear forces in cardiac development is the ability to obtain shear force measurements in vivo. Utilising the zebrafish model system we have developed a methodology that allows the shear force within the developing embryonic heart to be determined. Accurate wall shear measurement requires two essential pieces of information; high-resolution velocity measurements near the heart wall and the location and orientation of the heart wall itself. We have applied high-speed brightfield imaging to capture time-lapse series of blood flow within the beating heart between 3 and 6 days post-fertilization. Cardiac-phase filtering is applied to these time-lapse images to remove the heart wall and other slow moving structures leaving only the red blood cell movement. Using particle image velocimetry to calculate the velocity of red blood cells in different regions within the heart, and using the signal-to-noise ratio of the cardiac-phase filtered images to determine the boundary of blood flow, and therefore the position of the heart wall, we have been able to generate the necessary information to measure wall shear in vivo. We describe the methodology required to measure shear in vivo and the application of this technique to the developing zebrafish heart. We identify a reduction in shear at the ventricular-bulbar valve between 3 and 6 days post-fertilization and demonstrate that the shear environment of the ventricle during systole is constantly developing towards a more uniform level.

Role of shear stress in nitric oxide-dependent modulation of renal angiotensin II vasoconstriction.

Science.gov (United States)

Endlich, K; Muller, C; Barthelmebs, M; Helwig, J J

1999-08-01

1. Renal vasoconstriction in response to angiotensin II (ANGII) is known to be modulated by nitric oxide (NO). Since shear stress stimulates the release of a variety of vasoactive compounds from endothelial cells, we studied the impact of shear stress on the haemodynamic effect of ANGII in isolated perfused kidneys of rats under control conditions and during NO synthase inhibition with L-NAME (100 microM). 2. Kidneys were perfused in the presence of cyclo-oxygenase inhibitor (10 microM indomethacin) with Tyrode's solution of relative viscosity zeta=1 (low viscosity perfusate, LVP) or, in order to augment shear stress, with Tyrode's solution containing 7% Ficoll 70 of relative viscosity zeta=2 (high viscosity perfusate, HVP). 3. Vascular conductance was 3.5+/-0.4 fold larger in HVP as compared with LVP kidneys, associated with an augmentation of overall wall shear stress by 37+/-5%. During NO inhibition, vascular conductance was only 2.5+/-0.2 fold elevated in HVP vs LVP kidneys, demonstrating shear stress-induced vasodilatation by NO and non-NO/non-prostanoid compound(s). 4. ANGII (10 - 100 pM) constricted the vasculature in LVP kidneys, but was without effect in HVP kidneys. During NO inhibition, in contrast, ANGII vasoconstriction was potentiated in HVP as compared with LVP kidneys. 5. The potentiation of ANGII vasoconstriction during NO inhibition has been shown to be mediated by endothelium-derived P450 metabolites and to be sensitive to AT2 receptor blockade in our earlier studies. Accordingly, in HVP kidneys, increasing concentrations of the AT2 receptor antagonist PD123319 (5 and 500 nM) gradually abolished the potentiation of ANGII vasoconstriction during NO inhibition, but did not affect vasoconstriction in response to ANGII in LVP kidneys. 6. Our results demonstrate, that augmentation of shear stress by increasing perfusate viscosity induces vasodilatation in the rat kidney, which is partially mediated by NO. Elevated levels of shear stress attenuate

Effect of non-Newtonian viscosity on the fluid-dynamic characteristics in stenotic vessels

Science.gov (United States)

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

Shear weakening for different lithologies observed at different saturation stages

Science.gov (United States)

Diethart-Jauk, Elisabeth; Gegenhuber, Nina

2018-01-01

For this study, samples from different lithologies ("Leitha"-limestone, "Dachstein"-limestone, "Haupt"-dolomite, "Bunt"-sandstone, Grey Berea sandstone, granite, quartzite and basalt) were selected. Samples were dried at 70 °C, respectively 105 °C and were saturated with brine. Mass, porosity, permeability, compressional and shear wave velocity were determined from dry and brine saturated samples at laboratory conditions, based on an individual measurement program. Shear modulus was calculated to find out, if shear weakening exists for the dataset. Shear weakening means that shear modulus of dry samples is higher than of saturated samples, but it is assumed that shear modulus is unaffected by saturation. "Dachstein"-limestone and basalt show shear weakening, quartzite samples show both weakening and hardening. Granite samples are affected by temperature, after drying with 105 °C no change can be observed anymore. "Bunt"-sandstone samples show a change in the shear modulus in a small extent, although they may contain clay minerals. The other lithologies show no effect. Explanations for carbonate samples can be the complicated pore structure, for basalt it could be that weathering creates clay minerals which are known as causes for a change of the shear modulus. Fluid viscosity can also be an important factor.

The experimental viscosity and calculated relative viscosity of liquid In-Sn allcoys

International Nuclear Information System (INIS)

Wu, A.Q.; Guo, L.J.; Liu, C.S.; Jia, E.G.; Zhu, Z.G.

2007-01-01

The experimental measured viscosity of liquid pure Sn, In 20 Sn 80 and In 80 Sn 20 alloys was studied, and to make a comparison, the calculated relative viscosity based on the pair distribution functions, g(r), has also been studied. There is one peak in each experimental viscosity and calculated relative-viscosity curve of liquid pure Sn about 1000 deg. C. One valley appears in each experimental viscosity and calculated viscosity curve of liquid In 20 Sn 80 alloy about 700 deg. C. There is no abnormal behavior on In 80 Sn 20 alloy. The behavior of experimental viscosity and calculated relative viscosity is coincident with each other. Those results conformed that the temperature-induced structure anomalies reported before did take place

Increases in core temperature counterbalance effects of haemoconcentration on blood viscosity during prolonged exercise in the heat.

Science.gov (United States)

Buono, Michael J; Krippes, Taylor; Kolkhorst, Fred W; Williams, Alexander T; Cabrales, Pedro

2016-02-01

What is the central question of this study? The purpose of the present study was to determine the effects of exercise-induced haemoconcentration and hyperthermia on blood viscosity. What is the main finding and its importance? Exercise-induced haemoconcentration, increased plasma viscosity and increased blood aggregation, all of which increased blood viscosity, were counterbalanced by increased red blood cell (RBC) deformability (e.g. RBC membrane shear elastic modulus and elongation index) caused by the hyperthermia. Thus, blood viscosity remained unchanged following prolonged moderate-intensity exercise in the heat. Previous studies have reported that blood viscosity is significantly increased following exercise. However, these studies measured both pre- and postexercise blood viscosity at 37 °C even though core and blood temperatures would be expected to have increased during the exercise. Consequently, the effect of exercise-induced hyperthermia on mitigating change in blood viscosity may have been missed. The purpose of this study was to isolate the effects of exercise-induced haemoconcentration and hyperthermia and to determine their combined effects on blood viscosity. Nine subjects performed 2 h of moderate-intensity exercise in the heat (37 °C, 40% relative humidity), which resulted in significant increases from pre-exercise values for rectal temperature (from 37.11 ± 0.35 to 38.76 ± 0.13 °C), haemoconcentration (haematocrit increased from 43.6 ± 3.6 to 45.6 ± 3.5%) and dehydration (change in body weight = -3.6 ± 0.7%). Exercise-induced haemoconcentration significantly (P blood viscosity by 9% (from 3.97 to 4.33 cP at 300 s(-1)), whereas exercise-induced hyperthermia significantly decreased blood viscosity by 7% (from 3.97 to 3.69 cP at 300 s(-1)). When both factors were considered together, there was no overall change in blood viscosity (from 3.97 to 4.03 cP at 300 s(-1)). The effects of exercise-induced haemoconcentration, increased plasma

A MEMS Resonant Sensor to Measure Fluid Density and Viscosity under Flexural and Torsional Vibrating Modes

Directory of Open Access Journals (Sweden)

Libo Zhao

2016-06-01

Full Text Available Methods to calculate fluid density and viscosity using a micro-cantilever and based on the resonance principle were put forward. Their measuring mechanisms were analyzed and the theoretical equations to calculate the density and viscosity were deduced. The fluid-solid coupling simulations were completed for the micro-cantilevers with different shapes. The sensing chips with micro-cantilevers were designed based on the simulation results and fabricated using the micro electromechanical systems (MEMS technology. Finally, the MEMS resonant sensor was packaged with the sensing chip to measure the densities and viscosities of eight different fluids under the flexural and torsional vibrating modes separately. The relative errors of the measured densities from 600 kg/m3 to 900 kg/m3 and viscosities from 200 μPa·s to 1000 μPa·s were calculated and analyzed with different microcantilevers under various vibrating modes. The experimental results showed that the effects of the shape and vibrating mode of micro-cantilever on the measurement accuracies of fluid density and viscosity were analyzed in detail.

Measurement of Viscosity of Hydrocarbon Liquids Using a Microviscometer

DEFF Research Database (Denmark)

Dandekar, Abhijit; Andersen, Simon Ivar; Stenby, Erling Halfdan

1998-01-01

The viscosity of normal alkanes, their mixtures, and true boiling point (TBP) fractions (C (sub 6) -C (sub 19)) of four North Sea petroleum reservoir fluids have been measured by use of an automatic rolling ball mixroviscometer at 20°C. The equipment is specially suited for samples of limited amo...

Discontinuous Shear Thickening and Dilatancy: Frictional Effects in Viscous Suspensions

Science.gov (United States)

Morris, Jeffrey

2015-03-01

Shear thickening in concentrated suspensions has been well-known for quite a long time, yet a firm consensus on the basis for very abrupt or ``discontinuous'' shear thickening (DST) seen in suspensions of large solid fraction, ϕ, has not been reached. This work addresses the DST phenomenon, and proposes a simulation method based in the Stokesian Dynamics algorithm to explore the role of various forces between the particles, including hydrodynamic, conservative potential, and frictional interactions. This work shows that allowance for friction between spherical particles suspended in a viscous liquid causes a significant reduction in the jamming solid fraction of the mixture, ϕmax, taken as the maximum fraction at which the suspension will flow. A consequence of this is a shifting of the singularity in the effective viscosity, η, to smaller ϕmax, and the frictional suspension has a larger viscosity than does the frictionless suspension of the same solid fraction, as is clear from the standard empirical modeling of η (ϕ) =(1 - ϕ /ϕmax) - α , α ~ 2 . When a counterbalancing repulsive force between the particles, representative for example of charge-induced repulsion, is incorporated in the dynamics, the mixture undergoes a transition from frictionless to frictional interactions, and from low to high effective viscosity, at a critical shear rate. Comparison with experimental data shows remarkable agreement in the features of DST captured by the method. The basic algorithm and results of both rate-controlled and stress-controlled simulations will be presented. Like the shear stress, the magnitude of the normal stress exerted by the suspended particles also increases abruptly at the critical shear rate, consistent with the long-standing notion that dilatancy and shear-thickening are synonymous. We will show that considering all shear thickening materials as dilatant is a misconception, but demonstrate the validity of the connection of dilatancy with DST in

Applicability of Stokes method for measuring viscosity of mixtures with concentration gradient

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César Medina

2017-12-01

Full Text Available After measuring density and viscosity of a mixture of glycerin and water contained in a vertical pipe, a variation of these properties according to depth is observed. These gradients are typical of non-equilibrium states related to the lower density of water and the fact that relatively long times are necessary to achieve homogeneity. In the same pipe, the falling velocity of five little spheres is measured as a function of depth, and then a numerical fit is performed which agrees very well with experimental data. Based on the generalization of these results, the applicability of Stokes method is discussed for measuring viscosity of mixtures with a concentration gradient.

Study of cellulase enzymes self-assembly in aqueous-acetonitrile solvent: Viscosity measurements

Energy Technology Data Exchange (ETDEWEB)

Ghaouar, N., E-mail: naoufel-ghaouar@lycos.co [Laboratoire de Physique de la Matiere Molle, Faculte des Sciences de Tunis, Campus Universitaire, 2092 (Tunisia); Institut National des Sciences Appliquees et de Technologie, INSAT, Centre Urbain Nord, BP. 676, Tunis (Tunisia); Aschi, A. [Laboratoire de Physique de la Matiere Molle, Faculte des Sciences de Tunis, Campus Universitaire, 2092 (Tunisia); Belbahri, L. [School of Engineering of Lullier, University of Applied Sciences of Western Switzerland, 150, Route de Presinge, 1254 Jussy (Switzerland); Trabelsi, S.; Gharbi, A. [Laboratoire de Physique de la Matiere Molle, Faculte des Sciences de Tunis, Campus Universitaire, 2092 (Tunisia)

2009-11-15

The present study extends the viscosity measurements performed by Ghaouar et al. [Physica B, submitted for publication.] to study the conformational change of the cellulase enzymes in aqueous-acetonitrile mixture. We aim to investigate: (i) the denaturation process by measuring the specific viscosity for temperatures varying between 25 and 65 deg. C and acetonitrile concentrations between 0% and 50%, (ii) the enzyme-enzyme interaction by calculating the Huggins coefficient and (iii) the enzyme sizes by following the hydrodynamic radius for various temperatures. The precipitation of cellulases versus acetonitrile concentration is also considered. We show from all physical quantities measured in this work that the precipitation and the denaturation processes of cellulase enzymes exist together.

Study of cellulase enzymes self-assembly in aqueous-acetonitrile solvent: Viscosity measurements

International Nuclear Information System (INIS)

Ghaouar, N.; Aschi, A.; Belbahri, L.; Trabelsi, S.; Gharbi, A.

2009-01-01

The present study extends the viscosity measurements performed by Ghaouar et al. [Physica B, submitted for publication.] to study the conformational change of the cellulase enzymes in aqueous-acetonitrile mixture. We aim to investigate: (i) the denaturation process by measuring the specific viscosity for temperatures varying between 25 and 65 deg. C and acetonitrile concentrations between 0% and 50%, (ii) the enzyme-enzyme interaction by calculating the Huggins coefficient and (iii) the enzyme sizes by following the hydrodynamic radius for various temperatures. The precipitation of cellulases versus acetonitrile concentration is also considered. We show from all physical quantities measured in this work that the precipitation and the denaturation processes of cellulase enzymes exist together.

Rheological study of two-dimensional very anisometric colloidal particle suspensions: from shear-induced orientation to viscous dissipation.

Science.gov (United States)

Philippe, A M; Baravian, C; Bezuglyy, V; Angilella, J R; Meneau, F; Bihannic, I; Michot, L J

2013-04-30

In the present study, we investigate the evolution with shear of the viscosity of aqueous suspensions of size-selected natural swelling clay minerals for volume fractions extending from isotropic liquids to weak nematic gels. Such suspensions are strongly shear-thinning, a feature that is systematically observed for suspensions of nonspherical particles and that is linked to their orientational properties. We then combined our rheological measurements with small-angle X-ray scattering experiments that, after appropriate treatment, provide the orientational field of the particles. Whatever the clay nature, particle size, and volume fraction, this orientational field was shown to depend only on a nondimensional Péclet number (Pe) defined for one isolated particle as the ratio between hydrodynamic energy and Brownian thermal energy. The measured orientational fields were then directly compared to those obtained for infinitely thin disks through a numerical computation of the Fokker-Plank equation. Even in cases where multiple hydrodynamic interactions dominate, qualitative agreement between both orientational fields is observed, especially at high Péclet number. We have then used an effective approach to assess the viscosity of these suspensions through the definition of an effective volume fraction. Using such an approach, we have been able to transform the relationship between viscosity and volume fraction (ηr = f(φ)) into a relationship that links viscosity with both flow and volume fraction (ηr = f(φ, Pe)).

Fabrication and Testing of Viscosity Measuring Instrument (Viscometer

Directory of Open Access Journals (Sweden)

A. B. HASSAN

2006-01-01

Full Text Available This paper presents the fabrication and testing of a simple and portable viscometer for the measurement of bulk viscosity of different Newtonian fluids. It is aimed at making available the instrument in local markets and consequently reducing or eliminating the prohibitive cost of importation. The method employed is the use of a D.C motor to rotate a disc having holes for infra-red light to pass through and fall on a photo-diode thus undergoing amplification and this signal being translated on a moving-coil meter as a deflection. The motor speed is kept constant but varies with changes in viscosity of the fluid during stirring, which alter signals being read on the meter. The faster is revolution per minute of the disc, the less the deflection on the meter and vise-versa. From the results of tests conducted on various sample fluids using data on standard Newtonian fluids as reliable guide the efficiency of the viscometer was 76.5%.

Nondimensional scaling of magnetorheological rotary shear mode devices using the Mason number

Science.gov (United States)

Becnel, Andrew C.; Sherman, Stephen; Hu, Wei; Wereley, Norman M.

2015-04-01

Magnetorheological fluids (MRFs) exhibit rapidly adjustable viscosity in the presence of a magnetic field, and are increasingly used in adaptive shock absorbers for high speed impacts, corresponding to high fluid shear rates. However, the MRF properties are typically measured at very low (γ ˙10,000 s-1) Searle cell magnetorheometer, along with a full scale rotary-vane magnetorheological energy absorber (γ ˙>25,000 s-1) are employed to analyze MRF property scaling across shear rates using a nondimensional Mason number to generate an MRF master curve. Incorporating a Reynolds temperature correction factor, data from both experiments is shown to collapse to a single master curve, supporting the use of Mason number to correlate low- and high-shear rate characterization data.

The Effect of the Operating Conditions on the Apparent Viscosity of Crude Palm Oil During Oil Clarification

OpenAIRE

Sulaiman Al-Zuhair, Mirghani I. Ahmed and Yousif A. Abakr

2012-01-01

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...

Noncontact surface tension and viscosity measurements of rhenium in the liquid and undercooled states

International Nuclear Information System (INIS)

Ishikawa, Takehiko; Paradis, Paul-Francois; Yoda, Shinichi

2004-01-01

Surface tension and viscosity of liquid rhenium, which have hardly been measured due to the extremely high melting temperature of rhenium, were measured using an electrostatic levitation method combined with the oscillation drop technique. Sample position instability problems caused by the photon pressure of the heating lasers and by sample evaporation were solved by modifying the electrodes design. Good sample stability allowed the measurements of the surface tension and the viscosity over wide temperature ranges including the undercooled states. Over the 2800-3600 K interval, the surface tension of rhenium was measured as σ(T)=2.71x10 3 -0.23(T-T m ), where T m is the melting temperature, 3453 K. At T m , the datum agrees well with the literature values. Similarly, on the same temperature range, the viscosity was determined as η(T)=0.08 exp[1.33x10 5 /(RT)] (mPa s)

Direct observations of the viscosity of Earth's outer core and extrapolation of measurements of the viscosity of liquid iron

International Nuclear Information System (INIS)

Smylie, D E; Brazhkin, Vadim V; Palmer, Andrew

2009-01-01

Estimates vary widely as to the viscosity of Earth's outer fluid core. Directly observed viscosity is usually orders of magnitude higher than the values extrapolated from high-pressure high-temperature laboratory experiments, which are close to those for liquid iron at atmospheric pressure. It turned out that this discrepancy can be removed by extrapolating via the widely known Arrhenius activation model modified by lifting the commonly used assumption of pressure-independent activation volume (which is possible due to the discovery that at high pressures the activation volume increases strongly with pressure, resulting in 10 2 Pa s at the top of the fluid core, and in 10 11 Pa s at its bottom). There are of course many uncertainties affecting this extrapolation process. This paper reviews two viscosity determination methods, one for the top and the other for the bottom of the outer core, the former of which relies on the decay of free core nutations and yields 2371 ± 1530 Pa s, while the other relies on the reduction in the rotational splitting of the two equatorial translational modes of the solid inner core oscillations and yields an average of 1.247 ± 0.035 Pa s. Encouraged by the good performance of the Arrhenius extrapolation, a differential form of the Arrhenius activation model is used to interpolate along the melting temperature curve and to find the viscosity profile across the entire outer core. The viscosity variation is found to be nearly log-linear between the measured boundary values. (methodological notes)

3-D FDTD simulation of shear waves for evaluation of complex modulus imaging.

Science.gov (United States)

Orescanin, Marko; Wang, Yue; Insana, Michael

2011-02-01

The Navier equation describing shear wave propagation in 3-D viscoelastic media is solved numerically with a finite differences time domain (FDTD) method. Solutions are formed in terms of transverse scatterer velocity waves and then verified via comparison to measured wave fields in heterogeneous hydrogel phantoms. The numerical algorithm is used as a tool to study the effects on complex shear modulus estimation from wave propagation in heterogeneous viscoelastic media. We used an algebraic Helmholtz inversion (AHI) technique to solve for the complex shear modulus from simulated and experimental velocity data acquired in 2-D and 3-D. Although 3-D velocity estimates are required in general, there are object geometries for which 2-D inversions provide accurate estimations of the material properties. Through simulations and experiments, we explored artifacts generated in elastic and dynamic-viscous shear modulus images related to the shear wavelength and average viscosity.

Numerical simulation of bubble induced shear in membrane bioreactors: effects of mixed liquor rheology and membrane configuration.

Science.gov (United States)

Liu, Xuefei; Wang, Yuan; Waite, T David; Leslie, Greg

2015-05-15

A CFD model, incorporating an empirically determined rheology model and a porous media model, was developed to simulate bubble induced surface shear in membrane bioreactors configured with hollow fibre membranes with outer diameters ranging from 1.3 to 2.4 mm, arranged in vertically orientated modules with packing density from 200 to 560 m(2)/m(3). The rheology model was developed for mixed liquor suspended solids (MLSS) concentrations of 3 to 16 gL(-1) in the presence and absence of coagulant (generated by addition of a ferrous salt) for shear rates ranging from 0 to 500 s(-1). Experimentally determined particle relaxation times for the biological flocs in the mixed liquor, both in the absence and presence of iron, were negligible, consistent with an environment where positive buoyancy forces were greater than negative settling forces thereby allowing the sludge mixture to be modelled as a single continuous phase. The non-Newtonian behaviour of the mixed liquor was incorporated into the CFD simulations using an Ostwald-de Waele rheology model. Interactions between mixed liquor and hollow fibre membranes of different fibre size and packing density were described using a porous media model that was calibrated by empirical measurement of inertial loss coefficients over a range of viscosities (0.8 × 10(-3) to 2.1 × 10(-3) Pa.s) and velocities (0 to 0.35 m/s) typically encountered in full scale MBRs. Experimental results indicated that addition of iron salts resulted in an increase in MLSS and sludge viscosity. Shear stress is affected by both velocity and viscosity. The increase in sludge viscosity resulted in an increase in resistance to flow through the hollow fibre membrane bundles and, as a result, decreased the liquid flow velocities. CFD simulations provided insight on the effects of point of coagulant addition and MLSS concentration on bubble-induced shear over a range of industrially relevant conditions. A 12% increase in shear stress was observed when

How the dispersion of magnesium oxide nanoparticles effects on the viscosity of water-ethylene glycol mixture: Experimental evaluation and correlation development

Science.gov (United States)

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.

Stress tensor and viscosity of water: Molecular dynamics and generalized hydrodynamics results

Science.gov (United States)

Bertolini, Davide; Tani, Alessandro

1995-08-01

The time correlation functions (CF's) of diagonal and off-diagonal components of the stress tensor of water have been calculated at 245 and 298 K in a molecular dynamics (MD) study on 343 molecules in the microcanonical ensemble. We present results obtained at wave number k=0 and at a few finite values of k, in the atomic and molecular formalism. In all cases, more than 98% of these functions are due to the potential term of the stress tensor. At k=0, their main features are a fast oscillatory initial decay, followed by a long-time tail more apparent in the supercooled region. Bulk and shear viscosities, calculated via Green-Kubo integration of the relevant CF at k=0, are underestimated with respect to experimental data, mainly at low temperature, but their ratio (~=2) is correctly reproduced. Both shear and bulk viscosity decrease as a function of k, the latter more rapidly, so that they become almost equal at ~=1 Å-1. Also, both viscosities drop rapidly from their maximum at ω=0. This behavior has been related to the large narrowing observed in the acoustic band, mainly in the supercooled region. The infinite frequency bulk and shear rigidity moduli have been shown to be in fair agreement with the experimental data, provided the MD value used for comparison is that corresponding to the frequency range relevant to ultrasonic measurements. The MD results of stress-stress CF's compare well with those predicted by Bertolini and Tani [Phys. Rev. E 51, 1091 (1995)] at k=0, by an application of generalized hydrodynamics [de Schepper et al., Phys. Rev. A 38, 271 (1988)] in the molecular formalism, to the same model of water (TIP4P) [Jorgensen et al., J. Chem. Phys. 79, 926 (1983)]. These CF's are essentially equal in the atomic and molecular formalism, the only minor difference being restricted to the high frequency librational region of the shear function. By a comparison of atomic and molecular results, we show here that neglecting libration has no effect on the

Measurement and calculation of the viscosity of metals—a review of the current status and developing trends

International Nuclear Information System (INIS)

Cheng, J; Hort, N; Kainer, K U; Gröbner, J; Schmid-Fetzer, R

2014-01-01

Viscosity is an important rheological property of metals in casting because it controls the rate of transport of liquid metals, which may lead to casting defects such as hot tearing and porosity. The measurement methods and numerical models of the viscosity of liquid and semi-solid state metals that have been published to date are reviewed in this paper. Most experimental measurements have been performed with rotational and oscillatory viscometers, which offer advantages at low viscosities in particular. Besides these two traditional methods for measuring viscosities, a couple of studies also introduced the technique of isothermal compression for alloys in the semi-solid state, and even an optical basicity method for the viscosity of slags. As to numerical models, most published results show that the viscosity of liquid and semi-solid state metals can be described by the Arrhenius, Andrade, Kaptay or Budai–Bemkő–Kaptay equations. In addition, there are some alternative models, such as the power model and the isothermal stress–strain model. (topical review)

Study of Bovine Serum Albumin Solubility in Aqueous Solutions by Intrinsic Viscosity Measurements

Directory of Open Access Journals (Sweden)

Martin Alberto Masuelli

2013-01-01

Full Text Available The behavior of bovine serum albumin (BSA in water is scarcely studied, and the thermodynamic properties arising from the experimental measurements have not been reported. Intrinsic viscosity measurements are very useful in assessing the interaction between the solute and solvent. This work discussed in a simple determination of the enthalpy of BSA in aqueous solution when the concentration ranges from 0.2 to 36.71% wt. and the temperature from 35 to 40°C. The relationship between the concentration and intrinsic viscosity is determined according to the method of Huggins. The temperature increase reduces the ratio between inherent viscosity and concentration (ηi/c. This is reflected in the Van't Hoff curve. Furthermore, this work proposes hydrodynamic cohesion value as an indicator of the degree of affinity of protein with water and thermodynamic implications in conformational changes.

Near-surface viscosity measurements with a love acoustic wave device

International Nuclear Information System (INIS)

Collings, A.F.; Cooper, B.J.; Lappas, S.; Sor, J.A.

1999-01-01

Full text: In the last decade, considerable research effort has been directed towards interfacing piezoelectric transducers with biological detection systems to produce efficient and highly selective biosensors. Several types of piezoelectric or, more specifically, acoustic wave transducers have been investigated. Our group has developed Love wave (guided surface skimming wave) devices which are made by attaching a thin overlayer with the appropriate acoustic properties to the surface of a conventional surface horizontal mode device. An optimised layer concentrates most of the propagating wave energy in the guiding layer and can improve the device sensitivity in detecting gas-phase mass loading on the surface some 20- to 40-fold. Love wave devices used in liquid phase sensing will also respond to viscous, as well as mass, loading on the device surface. We have studied the propagation of viscous waves into liquid sitting on a Love wave device both theoretically and experimentally. Modelling of the effect of a viscous liquid layer on a Love wave propagating in a layered medium predicts the velocity profile in the solid substrate and in the adjoining liquid. This is a function of the thickness of the guiding layer, the elastic properties of the guiding layer and the piezoelectric substrate, and of the viscosity and density of the liquid layer. We report here on measurements of the viscosity of aqueous glycerine solutions made with a quartz Love wave device with a 5.5 μm SiO 2 guiding layer. The linear relationship between the decrease in the device frequency and the square root of the viscosity density product is accurately observed at Newtonian viscosities. At higher viscosities, there is an increase in damping, the insertion loss of the device saturates, Δf is no longer proportional to (ηp) l/2 and reaches a maximum. We also show results for the determination of the gelation time in protein and inorganic aqueous gels and for the rate of change of viscosity with

Viscosity of ring polymer melts

KAUST Repository

Pasquino, Rossana

2013-10-15

We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η 0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/ η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z 1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z 1.6±0.3) and the simulations (η0,linear/ η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem. © 2013 American Chemical Society.

Viscosity of ring polymer melts

KAUST Repository

Pasquino, Rossana; Vasilakopoulos, Thodoris C.; Jeong, Youncheol; Lee, Hyojoon; Rogers, Simon A.; Sakellariou, Georgios; Allgaier, Jü rgen B.; Takano, Atsushi; Brá s, Ana Rita E; Chang, Taihyun; Gooß en, Sebastian; Pyckhout-Hintzen, Wim; Wischnewski, Andreas; Hadjichristidis, Nikolaos; Richter, Dieter R.; Rubinstein, Michael H.; Vlassopoulos, Dimitris

2013-01-01

We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η 0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/ η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z 1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z 1.6±0.3) and the simulations (η0,linear/ η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem. © 2013 American Chemical Society.

Green-Kubo relation for viscosity tested using experimental data for a two-dimensional dusty plasma

Science.gov (United States)

Feng, Yan; Goree, J.; Liu, Bin; Cohen, E. G. D.

2011-10-01

The theoretical Green-Kubo relation for viscosity is tested using experimentally obtained data. In a dusty plasma experiment, micron-sized dust particles are introduced into a partially ionized argon plasma, where they become negatively charged. They are electrically levitated to form a single-layer Wigner crystal, which is subsequently melted using laser heating. In the liquid phase, these dust particles experience interparticle electric repulsion, laser heating, and friction from the ambient neutral argon gas, and they can be considered to be in a nonequilibrium steady state. Direct measurements of the positions and velocities of individual dust particles are then used to obtain a time series for an off-diagonal element of the stress tensor and its time autocorrelation function. This calculation also requires the interparticle potential, which was not measured experimentally but was obtained using a Debye-Hückel-type model with experimentally determined parameters. Integrating the autocorrelation function over time yields the viscosity for shearing motion among dust particles. The viscosity so obtained is found to agree with results from a previous experiment using a hydrodynamical Navier-Stokes equation. This comparison serves as a test of the Green-Kubo relation for viscosity. Our result is also compared to the predictions of several simulations.

Automation of a high-speed imaging setup for differential viscosity measurements

Science.gov (United States)

Hurth, C.; Duane, B.; Whitfield, D.; Smith, S.; Nordquist, A.; Zenhausern, F.

2013-12-01

We present the automation of a setup previously used to assess the viscosity of pleural effusion samples and discriminate between transudates and exudates, an important first step in clinical diagnostics. The presented automation includes the design, testing, and characterization of a vacuum-actuated loading station that handles the 2 mm glass spheres used as sensors, as well as the engineering of electronic Printed Circuit Board (PCB) incorporating a microcontroller and their synchronization with a commercial high-speed camera operating at 10 000 fps. The hereby work therefore focuses on the instrumentation-related automation efforts as the general method and clinical application have been reported earlier [Hurth et al., J. Appl. Phys. 110, 034701 (2011)]. In addition, we validate the performance of the automated setup with the calibration for viscosity measurements using water/glycerol standard solutions and the determination of the viscosity of an "unknown" solution of hydroxyethyl cellulose.

Automation of a high-speed imaging setup for differential viscosity measurements

Energy Technology Data Exchange (ETDEWEB)

Hurth, C.; Duane, B.; Whitfield, D.; Smith, S.; Nordquist, A.; Zenhausern, F. [Center for Applied Nanobioscience and Medicine, The University of Arizona College of Medicine, 425 N 5th Street, Phoenix, Arizona 85004 (United States)

2013-12-28

We present the automation of a setup previously used to assess the viscosity of pleural effusion samples and discriminate between transudates and exudates, an important first step in clinical diagnostics. The presented automation includes the design, testing, and characterization of a vacuum-actuated loading station that handles the 2 mm glass spheres used as sensors, as well as the engineering of electronic Printed Circuit Board (PCB) incorporating a microcontroller and their synchronization with a commercial high-speed camera operating at 10 000 fps. The hereby work therefore focuses on the instrumentation-related automation efforts as the general method and clinical application have been reported earlier [Hurth et al., J. Appl. Phys. 110, 034701 (2011)]. In addition, we validate the performance of the automated setup with the calibration for viscosity measurements using water/glycerol standard solutions and the determination of the viscosity of an “unknown” solution of hydroxyethyl cellulose.

Elongational viscosity of photo-oxidated LDPE

Science.gov (United States)

Rolón-Garrido, Víctor H.; Wagner, Manfred H.

2014-05-01

Sheets of low-density polyethylene (LDPE) were photo-oxidatively treated at room temperature, and subsequently characterized rheologically in the melt state by shear and uniaxial extensional experiments. For photo-oxidation, a xenon lamp was used to irradiate the samples for times between 1 day and 6 weeks. Linear-viscoelastic characterization was performed in a temperature range of 130 to 220°C to obtain the master curve at 170°C, the reference temperature at which the elongational viscosities were measured. Linear viscoelasticity is increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by an increasing gel fraction as determined by a solvent extraction method. The elongational measurements reveal a strong enhancement of strain hardening until a saturation level is achieved. The elongational data are analyzed in the frame work of two constitutive equations, the rubber-like liquid and the molecular stress function models. Within the experimental window, timedeformation separability is confirmed for all samples, independent of the degree of photo-oxidation.

On-line measurement of food viscosity during flow

DEFF Research Database (Denmark)

Mason, Sarah Louise; Friis, Alan

2006-01-01

Sarah L. Mason and Alan Friis discuss some of the principles and equipment used to monitor food viscosity in real time.......Sarah L. Mason and Alan Friis discuss some of the principles and equipment used to monitor food viscosity in real time....

Viscosity of concentrated solutions and of human erythrocyte cytoplasm determined from NMR measurement of molecular correlation times

International Nuclear Information System (INIS)

Endre, Z.H.; Kuchel, P.W.

1986-01-01

Metabolically active human erythrocytes were incubated with [α- 13 C]glycine which led to the specific enrichment of intracellular glutathione. The cells were then studied using 13 C-NMR in which the longitudinal relaxation times (T 1 ) and nuclear Overhauser enhancements of the free glycine and glutathione were measured. Bulk viscosities of the erythrocyte cytoplasm were measured using Ostwald capillary viscometry. Large differences existed between the latter viscosity estimates and those based upon NMR-T 1 measurements. The authors derived an equation from the theory of the viscosity of concentrated solutions which contains two phenomenological interaction parameters, a 'shape' factor and a 'volume' factor; it was fitted to data relating to the concentration dependence of viscosity measured by both methods. Under various conditions of extracellular osmotic pressure, erythrocytes change volume and thus the viscosity of the intracellular milieu is altered. The volume changes resulted in changes in the T 1 of [α- 13 C]glycine. Conversely, the authors showed that alterations in T 1 , when appropriately calibrated, could be used for monitoring changes in volume of metabolically active cells. (Auth.)

Performance of a Polymer Flood with Shear-Thinning Fluid in Heterogeneous Layered Systems with Crossflow

Directory of Open Access Journals (Sweden)

Kun Sang Lee

2011-08-01

Full Text Available Assessment of the potential of a polymer flood for mobility control requires an accurate model on the viscosities of displacement fluids involved in the process. Because most polymers used in EOR exhibit shear-thinning behavior, the effective viscosity of a polymer solution is a highly nonlinear function of shear rate. A reservoir simulator including the model for the shear-rate dependence of viscosity was used to investigate shear-thinning effects of polymer solution on the performance of the layered reservoir in a five-spot pattern operating under polymer flood followed by waterflood. The model can be used as a quantitative tool to evaluate the comparative studies of different polymer flooding scenarios with respect to shear-rate dependence of fluids’ viscosities. Results of cumulative oil recovery and water-oil ratio are presented for parameters of shear-rate dependencies, permeability heterogeneity, and crossflow. The results of this work have proven the importance of taking non-Newtonian behavior of polymer solution into account for the successful evaluation of polymer flood processes. Horizontal and vertical permeabilities of each layer are shown to impact the predicted performance substantially. In reservoirs with a severe permeability contrast between horizontal layers, decrease in oil recovery and sudden increase in WOR are obtained by the low sweep efficiency and early water breakthrough through highly permeable layer, especially for shear-thinning fluids. An increase in the degree of crossflow resulting from sufficient vertical permeability is responsible for the enhanced sweep of the low permeability layers, which results in increased oil recovery. It was observed that a thinning fluid coefficient would increase injectivity significantly from simulations with various injection rates. A thorough understanding of polymer rheology in the reservoir and accurate numerical modeling are of fundamental importance for the exact estimation

Tensile and shear methods for measuring strength of bilayer tablets.

Science.gov (United States)

Chang, Shao-Yu; Li, Jian-Xin; Sun, Changquan Calvin

2017-05-15

Both shear and tensile measurement methods have been used to quantify interfacial bonding strength of bilayer tablets. The shear method is more convenient to perform, but reproducible strength data requires careful control of the placement of tablet and contact point for shear force application. Moreover, data obtained from the shear method depend on the orientation of the bilayer tablet. Although more time-consuming to perform, the tensile method yields data that are straightforward to interpret. Thus, the tensile method is preferred in fundamental bilayer tableting research to minimize ambiguity in data interpretation. Using both shear and tensile methods, we measured the mechanical strength of bilayer tablets made of several different layer combinations of lactose and microcrystalline cellulose. We observed a good correlation between strength obtained by the tensile method and carefully conducted shear method. This suggests that the shear method may be used for routine quality test of bilayer tablets during manufacturing because of its speed and convenience, provided a protocol for careful control of the placement of the tablet interface, tablet orientation, and blade is implemented. Copyright © 2017 Elsevier B.V. All rights reserved.

High Resolution Shear Profile Measurements in Entangled Polymers

KAUST Repository

Hayes, Keesha A.

2008-11-17

We use confocal microscopy and particle image velocimetry to visualize motion of 250-300 nm. fluorescent tracer particles in entangled polymers subject to a rectilinear shear flow. Our results show linear velocity profiles in polymer solutions spanning a wide range of molecular weights and number of entanglements (8≤Z≤56), but reveal large differences between the imposed and measured shear rates. These findings disagree with recent reports that shear banding is a characteristic flow response of entangled polymers, and instead point to interfacial slip as an important source of strain loss. © 2008 The American Physical Society.

Microrheometric upconversion-based techniques for intracellular viscosity measurements

Science.gov (United States)

Rodríguez-Sevilla, Paloma; Zhang, Yuhai; de Sousa, Nuno; Marqués, Manuel I.; Sanz-Rodríguez, Francisco; Jaque, Daniel; Liu, Xiaogang; Haro-González, Patricia

2017-08-01

Rheological parameters (viscosity, creep compliance and elasticity) play an important role in cell function and viability. For this reason different strategies have been developed for their study. In this work, two new microrheometric techniques are presented. Both methods take advantage of the analysis of the polarized emission of an upconverting particle to determine its orientation inside the optical trap. Upconverting particles are optical materials that are able to convert infrared radiation into visible light. Their usefulness has been further boosted by the recent demonstration of their three-dimensional control and tracking by single beam infrared optical traps. In this work it is demonstrated that optical torques are responsible of the stable orientation of the upconverting particle inside the trap. Moreover, numerical calculations and experimental data allowed to use the rotation dynamics of the optically trapped upconverting particle for environmental sensing. In particular, the cytoplasm viscosity could be measured by using the rotation time and thermal fluctuations of an intracellular optically trapped upconverting particle, by means of the two previously mentioned microrheometric techniques.

Contribution to viscosity from the structural relaxation via the atomic scale Green-Kubo stress correlation function

Science.gov (United States)

Levashov, V. A.

2017-11-01

We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.

On the propagation of linear longitudinal acoustic waves in isotropic media with shear and volume viscosity and a tensorial internal variable. II. Some cases of special interest (Poynting-Thomson, Jeffreys, Maxwell, Kelvin-Voigt, Hooke and Newton media)

NARCIS (Netherlands)

Ciancio, V.; Turrisi, E.; Kluitenberg, G.A.

1986-01-01

In a previous paper the propagation of linear longitudinal acoustic waves in isotropic media with shear and volume viscosity and a tensorial internal variable was considered and the expressions for the velocity and attenuation of the waves were obtained. In the present paper we investigate the

Gas Near a Wall: Shortened Mean Free Path, Reduced Viscosity, and the Manifestation of the Knudsen Layer in the Navier-Stokes Solution of a Shear Flow

Science.gov (United States)

Abramov, Rafail V.

2018-06-01

For the gas near a solid planar wall, we propose a scaling formula for the mean free path of a molecule as a function of the distance from the wall, under the assumption of a uniform distribution of the incident directions of the molecular free flight. We subsequently impose the same scaling onto the viscosity of the gas near the wall and compute the Navier-Stokes solution of the velocity of a shear flow parallel to the wall. Under the simplifying assumption of constant temperature of the gas, the velocity profile becomes an explicit nonlinear function of the distance from the wall and exhibits a Knudsen boundary layer near the wall. To verify the validity of the obtained formula, we perform the Direct Simulation Monte Carlo computations for the shear flow of argon and nitrogen at normal density and temperature. We find excellent agreement between our velocity approximation and the computed DSMC velocity profiles both within the Knudsen boundary layer and away from it.

Sheared flow layer formation in tokamak plasmas with reversed magnetic shear

International Nuclear Information System (INIS)

Dong, J.Q.; Long, Y.X.; Mou, Z.Z.; Zhang, J.H.; Li, J.Q.

2005-01-01

Sheared flow layer (SFL) formation due to magnetic energy release through tearing-reconnections in tokamak plasmas is investigated. The characteristics of the SFLs created in the development of double tearing mode, mediated by electron viscosity in configurations with non-monotonic safety factor q profiles and, therefore, two rational flux surfaces of same q value, are analyzed in detail as an example. Quasi-linear simulations demonstrate that the sheared flows induced by the mode have desirable characteristics (lying at the boundaries of the magnetic islands), and sufficient levels required for internal transport barrier (ITB) formation. A possible correlation of the SFLs with experimental observations, that double transport barrier structures are preferentially formed in proximity of the two rational surfaces, is also proffered. (author)

Experimental Research on Boundary Shear Stress in Typical Meandering Channel

Science.gov (United States)

Chen, Kai-hua; Xia, Yun-feng; Zhang, Shi-zhao; Wen, Yun-cheng; Xu, Hua

2018-06-01

A novel instrument named Micro-Electro-Mechanical System (MEMS) flexible hot-film shear stress sensor was used to study the boundary shear stress distribution in the generalized natural meandering open channel, and the mean sidewall shear stress distribution along the meandering channel, and the lateral boundary shear stress distribution in the typical cross-section of the meandering channel was analysed. Based on the measurement of the boundary shear stress, a semi-empirical semi-theoretical computing approach of the boundary shear stress was derived including the effects of the secondary flow, sidewall roughness factor, eddy viscosity and the additional Reynolds stress, and more importantly, for the first time, it combined the effects of the cross-section central angle and the Reynolds number into the expressions. Afterwards, a comparison between the previous research and this study was developed. Following the result, we found that the semi-empirical semi-theoretical boundary shear stress distribution algorithm can predict the boundary shear stress distribution precisely. Finally, a single factor analysis was conducted on the relationship between the average sidewall shear stress on the convex and concave bank and the flow rate, water depth, slope ratio, or the cross-section central angle of the open channel bend. The functional relationship with each of the above factors was established, and then the distance from the location of the extreme sidewall shear stress to the bottom of the open channel was deduced based on the statistical theory.

The viscosity of dimethyl ether

DEFF Research Database (Denmark)

Sivebæk, Ion Marius; Jakobsen, Jørgen

2007-01-01

and NOx traps are installed. The most significant problem encountered when engines are fuelled with DME is that the injection equipment breaks down prematurely due to extensive wear. This tribology issue can be explained by the very low lubricity and viscosity of DME. Recently, laboratory methods have...... appeared capable of measuring these properties of DME. The development of this is rendered difficult because DME has to be pressurised to remain in the liquid state and it dissolves most of the commercially available elastomers. This paper deals fundamentally with the measurement of the viscosity of DME...... and extends the discussion to the difficulty of viscosity establishing of very thin fluids. The main issue here is that it is not easy to calibrate the viscometers in the very low viscosity range corresponding to about one-fifth of that of water. The result is that the low viscosity is measured at high...

Viscosity of nanoconfined polyamide-6,6 oligomers: atomistic reverse nonequilibrium molecular dynamics simulation.

Science.gov (United States)

Eslami, Hossein; Müller-Plathe, Florian

2010-01-14

Our new simulation scheme in isosurface-isothermal-isobaric ensemble [Eslami, H.; Mozaffari, F.; Moghadasi, J.; Müller-Plathe, F. J. Chem. Phys. 2008, 129, 194702], developed to simulate confined fluids in equilibrium with bulk, is applied to simulate polyamide-6,6 oligomers confined between graphite surfaces. The reverse nonequilibrium molecular dynamics simulation technique is employed to shear the graphite surfaces. In this work, six confined systems, with different surface separations, as well as the bulk fluid are simulated. Our results show a viscosity increase with respect to the bulk fluid, with decreasing distance between surfaces. Also, the calculated viscosities of the confined systems show an oscillatory behavior with maxima corresponding to well-formed layers between the surfaces. We observe a substantial slip at the surfaces, with the slip length depending on the shear rate and on the slit width. The slip length and the slip velocity show oscillatory behavior with out-of-phase oscillations with respect to the solvation force oscillations. Moreover, the temperature difference between coldest and hottest parts of the simulation box depends on the shear rate and on the layering effect (solvation force oscillations). An analysis of oligomer deformation under flow shows preferential alignment of oligomers parallel to the surfaces with increasing shear rate.

Rheological measurements on cement grouts

International Nuclear Information System (INIS)

Dalton, M.J.

1986-06-01

This report describes the techniques which have been developed at Winfrith for assessing the rheological properties of cement grouts. A discussion of the theory of rheology and its application to cement is given and the methodology for calibrating a special paddle measuring system for a commercial viscometer is described. The use of the system for determining flow curves, equilibrium viscosity, viscosity as a function of shearing time and structure changes is also discussed. (author)

A blood-oxygenation-dependent increase in blood viscosity due to a static magnetic field

International Nuclear Information System (INIS)

Yamamoto, Toru; Nagayama, Yuki; Tamura, Mamoru

2004-01-01

As the magnetic field of widely used MR scanners is one of the strongest magnetic fields to which people are exposed, the biological influence of the static magnetic field of MR scanners is of great concern. One magnetic interaction in biological subjects is the magnetic torque on the magnetic moment induced by biomagnetic substances. The red blood cell is a major biomagnetic substance, and the blood flow may be influenced by the magnetic field. However, the underlying mechanisms have been poorly understood. To examine the mechanisms of the magnetic influence on blood viscosity, we measured the time for blood to fall through a glass capillary inside and outside a 1.5 T MR scanner. Our in vitro results showed that the blood viscosity significantly increased in a 1.5 T MR scanner, and also clarified the mechanism of the interaction between red blood cells and the external magnetic field. Notably, the blood viscosity increased depending on blood oxygenation and the shear rate of the blood flow. Thus, our findings suggest that even a 1.5 T magnetic field may modulate blood flow

Experimental investigation of non-Newtonian droplet collisions : the role of extensional viscosity

NARCIS (Netherlands)

Finotello, Giulia; De, Shauvik; Vrouwenvelder, Jeroen C.R.; Padding, J.T.; Buist, Kay A.; Jongsma, Alfred; Innings, Fredrik; Kuipers, J.

2018-01-01

We investigate the collision behaviour of a shear thinning non-Newtonian fluid xanthan, by binary droplet collision experiments. Droplet collisions of non-Newtonian fluids are more complex than their Newtonian counterpart as the viscosity no longer remains constant during the collision process.

Development of a shear force measurement dummy for seat comfort.

Science.gov (United States)

Kim, Seong Guk; Ko, Chang-Yong; Kim, Dong Hyun; Song, Ye Eun; Kang, Tae Uk; Ahn, Sungwoo; Lim, Dohyung; Kim, Han Sung

2017-01-01

Seat comfort is one of the main factors that consumers consider when purchasing a car. In this study, we develop a dummy with a shear-force sensor to evaluate seat comfort. The sensor has dimensions of 25 mm × 25 mm × 26 mm and is made of S45C. Electroless nickel plating is employed to coat its surface in order to prevent corrosion and oxidation. The proposed sensor is validated using a qualified load cell and shows high accuracy and precision (measurement range: -30-30 N; sensitivity: 0.1 N; linear relationship: R = 0.999; transverse sensitivity: <1%). The dummy is manufactured in compliance with the SAE standards (SAE J826) and incorporates shear sensors into its design. We measure the shear force under four driving conditions and at five different speeds using a sedan; results showed that the shear force increases with speed under all driving conditions. In the case of acceleration and deceleration, shear force significantly changes in the lower body of the dummy. During right and left turns, it significantly changes in the upper body of the dummy.

Measuring Viscosity with a Levitating Magnet: Application to Complex Fluids

Science.gov (United States)

Even, C.; Bouquet, F.; Remond, J.; Deloche, B.

2009-01-01

As an experimental project proposed to students in fourth year of university, a viscometer was developed, consisting of a small magnet levitating in a viscous fluid. The viscous force acting on the magnet is directly measured: viscosities in the range 10-10[superscript 6] mPa s are obtained. This experiment is used as an introduction to complex…

Accounting for the speed shear in wind turbine power performance measurement

DEFF Research Database (Denmark)

Wagner, Rozenn

the vertical wind shear and the turbulence intensity. The work presented in this thesis consists of the description and the investigation of a simple method to account for the wind speed shear in the power performance measurement. Ignoring this effect was shown to result in a power curve dependant on the shear...... for turbulence intensity suggested by Albers. The second method was found to be more suitable for normalising the power curve for the turbulence intensity. Using the equivalent wind speed accounting for the wind shear in the power performance measurement was shown to result in a more repeatable power curve than......The power curve of a wind turbine is the primary characteristic of the machine as it is the basis of the warranty for it power production. The current IEC standard for power performance measurement only requires the measurement of the wind speed at hub height and the air density to characterise...

An evaluation of the pressure-dependent melt viscosity of Polyphenylsulfone

Czech Academy of Sciences Publication Activity Database

Sedláček, T.; Hausnerová, B.; Filip, Petr

2014-01-01

Roč. 54, č. 3 (2014), s. 711-715 ISSN 0032-3888 R&D Projects: GA ČR GA103/08/1307 Grant - others:GA MŠk(CZ) ED2.1.00/03.0111 Institutional support: RVO:67985874 Keywords : polyphenysulfone * shear viscosity * PVT behaviour Subject RIV: BK - Fluid Dynamics Impact factor: 1.520, year: 2014

An eddy viscosity model for flow in a tube bundle

International Nuclear Information System (INIS)

Soussan, D.; Grandotto, M.

1998-01-01

The work described in this paper is part of the development of GENEPI a 3-dimensional finite element code, designed for the thermalhydraulic analysis of steam generators. It focuses on the implementation of two-phase flow turbulence-induced viscosity in a tube bundle. The GENEPI code, as other industrial codes, uses the eddy viscosity concept introduced by Boussinesq for single phase flow. The concept assumes that the turbulent momentum transfer is similar to the viscous shear stresses. Eddy viscosity formulation is reasonably well known for single phase flows, especially in simple geometries (i.e., in smooth tube, around a single body, or behind a row of bars/tubes), but there exists very little information on it for two-phase flows. An analogy between single and two-phases is used to set up a model for eddy viscosity. The eddy viscosity model examined in this paper is used for a tube bundle geometry and, therefore, is extended to include anisotropy to the classic model. Each of the main flow directions (cross flow inline, cross flow staggered, and parallel flows) gives rise to a specific eddy viscosity formula. The results from a parametric study indicate that the eddy viscosity in the staggered flow is roughly 1.5 times as large as that for the inline cross flow, 60 times as large as that for the parallel flow, and 105 as large as that for the molecular viscosity. Then, the different terms are combined with each other to result in a global eddy viscosity model for a steam generator tube bundle flow. (author)

Viscosity of dilute suspensions of rodlike particles: A numerical simulation method

Science.gov (United States)

Yamamoto, Satoru; Matsuoka, Takaaki

1994-02-01

The recently developed simulation method, named as the particle simulation method (PSM), is extended to predict the viscosity of dilute suspensions of rodlike particles. In this method a rodlike particle is modeled by bonded spheres. Each bond has three types of springs for stretching, bending, and twisting deformation. The rod model can therefore deform by changing the bond distance, bond angle, and torsion angle between paired spheres. The rod model can represent a variety of rigidity by modifying the bond parameters related to Young's modulus and the shear modulus of the real particle. The time evolution of each constituent sphere of the rod model is followed by molecular-dynamics-type approach. The intrinsic viscosity of a suspension of rodlike particles is derived from calculating an increased energy dissipation for each sphere of the rod model in a viscous fluid. With and without deformation of the particle, the motion of the rodlike particle was numerically simulated in a three-dimensional simple shear flow at a low particle Reynolds number and without Brownian motion of particles. The intrinsic viscosity of the suspension of rodlike particles was investigated on orientation angle, rotation orbit, deformation, and aspect ratio of the particle. For the rigid rodlike particle, the simulated rotation orbit compared extremely well with theoretical one which was obtained for a rigid ellipsoidal particle by use of Jeffery's equation. The simulated dependence of the intrinsic viscosity on various factors was also identical with that of theories for suspensions of rigid rodlike particles. For the flexible rodlike particle, the rotation orbit could be obtained by the particle simulation method and it was also cleared that the intrinsic viscosity decreased as occurring of recoverable deformation of the rodlike particle induced by flow.

Measurement of Flow Properties of Mammalian Blood with Different Hematocrit Values Using Falling Needle Rheometer

Directory of Open Access Journals (Sweden)

Takamasa Suzuki

2014-08-01

Full Text Available The development of viscometry with high accuracy and quick operation, as well as the establishment of a data evaluation method by pathology are largely required. Especially, the flow properties of human blood are an important factor in the evaluation of blood disease on the medicine, but the method of viscometry and the data collection are not so easy. This study has been described on the viscosity measurement and their evaluations for mammalian blood (rabbit, pig and horse including human blood. A compact-sized falling needle rheometer (FNR and a flow analysis method using this device for blood have been developed, and the relationship between the apparent viscosity and physical properties (density, hematocrit value of blood have also been evaluated. Measured flow properties of blood are evaluated as a flow curve showing the relationship between the shear stress and shear rate. Observed flow curves of mammalian bloods show three typical fluid regions, these are, the Non-newtonian fluid region for a low shear rate range, the transition region and the Newtonian fluid region for a high shear rate range. Flow properties of blood in the Casson fluid region and the apparent viscosity (μ in the Newtonian fluid region are measured, and they are compared between mammals.

Extensional viscosity for polymer melts measured in the filament stretching rheometer

DEFF Research Database (Denmark)

Bach, Anders; Rasmussen, Henrik K.; Hassager, Ole

2003-01-01

A new filament stretching rheometer has been constructed to measure the elongational viscosity of polymer melts at high temperatures. Two polymer melts, a LDPE and a LLDPE, were investigated with this rheometer. A constant elongational rate has been obtained by an iterative application of the Orr...

Dynamic viscosity of polymer solutions

Energy Technology Data Exchange (ETDEWEB)

Peterlin, A

1982-03-01

The dynamic viscosity investigation of solutions of long chain polymers in very viscous solvents has definitely shown the existence of the low and high frequency plateau with the gradual transition between them. In both extreme cases the extrapolation of the measured Newtonian viscosities of the plateaus to the infinite dilution yields the limiting intrinsic viscosities. Such a behavior is expected from the dynamic intrinsic viscosity of the necklace model of the linear polymer with finite internal viscosity. The plateau at low frequency shows up in any model of polymer solution. This work shows the constant dynamic intrinsic viscosity in both extreme cases is well reproducible by the necklace model with the internal viscosity acting only between the beads on the same link. 20 references.

Measuring viscosity with a levitating magnet: application to complex fluids

International Nuclear Information System (INIS)

Even, C; Bouquet, F; Deloche, B; Remond, J

2009-01-01

As an experimental project proposed to students in fourth year of university, a viscometer was developed, consisting of a small magnet levitating in a viscous fluid. The viscous force acting on the magnet is directly measured: viscosities in the range 10-10 6 mPa s are obtained. This experiment is used as an introduction to complex fluids and soft matter physics

Viscosity Measurements and Correlations for 1,1,1,2-tetrafluoroethane (HFC-134a) up to 140 MPa

DEFF Research Database (Denmark)

Comuñas, M.J.P.; Baylaucq, A.; Cisneros, Sergio

2003-01-01

In spite of being one of the most studied refrigerants, large discrepancies in the experimental determination of the dynamic viscosity of 1, 1, 1,2-tetrafluoroethane (HFC-134a) prevail. Additionally, there is a need for supplementary high-pressure measurements that can help to derive sound general...... correlations for the viscosity of this compound. Hence, in this work new dynamic viscosity measurements for HFC-134a using a falling-body viscometer in the temperature range of 293.15-373.15 K and pressures up to 140 MPa are presented. This work high-pressure data in combination with already published data...

Density and Viscosity Measurement of Diesel Fuels at Combined High Pressure and Elevated Temperature

Directory of Open Access Journals (Sweden)

Carl Schaschke

2013-07-01

Full Text Available We report the measurement of the viscosity and density of various diesel fuels, obtained from British refineries, at elevated pressures up to 500 MPa and temperatures in the range 298 K to 373 K. The measurement and prediction procedures of fluid properties under high pressure conditions is of increasing interest in many processes and systems including enhanced oil recovery, automotive engine fuel injection, braking, and hydraulic systems. Accurate data and understanding of the fluid characteristic in terms of pressure, volume and temperature is required particularly where the fluid is composed of a complex mixture or blend of aliphatic or aromatic hydrocarbons. In this study, high pressure viscosity data was obtained using a thermostatically-controlled falling sinker-type high pressure viscometer to provide reproducible and reliable viscosity data based on terminal velocity sinker fall times. This was supported with density measurements using a micro-pVT device. Both high-pressure devices were additionally capable of illustrating the freezing points of the hydrocarbon mixtures. This work has, thus, provided data that can extend the application of mixtures of commercially available fuels and to test the validity of available predictive density and viscosity models. This included a Tait-style equation for fluid compressibility prediction. For complex diesel fuel compositions, which have many unidentified components, the approach illustrates the need to apply appropriate correlations, which require accurate knowledge or prediction of thermodynamic properties.

Local viscosity distribution in bifurcating microfluidic blood flows

Science.gov (United States)

Kaliviotis, E.; Sherwood, J. M.; Balabani, S.

2018-03-01

The red blood cell (RBC) aggregation phenomenon is majorly responsible for the non-Newtonian nature of blood, influencing the blood flow characteristics in the microvasculature. Of considerable interest is the behaviour of the fluid at the bifurcating regions. In vitro experiments, using microchannels, have shown that RBC aggregation, at certain flow conditions, affects the bluntness and skewness of the velocity profile, the local RBC concentration, and the cell-depleted layer at the channel walls. In addition, the developed RBC aggregates appear unevenly distributed in the outlets of these channels depending on their spatial distribution in the feeding branch, and on the flow conditions in the outlet branches. In the present work, constitutive equations of blood viscosity, from earlier work of the authors, are applied to flows in a T-type bifurcating microchannel to examine the local viscosity characteristics. Viscosity maps are derived for various flow distributions in the outlet branches of the channel, and the location of maximum viscosity magnitude is obtained. The viscosity does not appear significantly elevated in the branches of lower flow rate as would be expected on the basis of the low shear therein, and the maximum magnitude appears in the vicinity of the junction, and towards the side of the outlet branch with the higher flow rate. The study demonstrates that in the branches of lower flow rate, the local viscosity is also low, helping us to explain why the effects of physiological red blood cell aggregation have no adverse effects in terms of in vivo vascular resistance.

Non-Newtonian behavior and molecular structure of Cooee bitumen under shear flow

DEFF Research Database (Denmark)

Lemarchand, Claire; Bailey, Nicholas; Daivis, Peter

2015-01-01

The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences, and pressure of the bitumen mixture are computed at different shear...... rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. In addition, the Cooee model is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules in bitumen. These nanoaggregates...

Nondimensional quasi-steady analysis of magnetorheological dampers utilizing a Herschel-Bulkley model with preyield viscosity

Science.gov (United States)

John, Shaju; Wereley, Norman M.

2003-07-01

Dampers based on electrorheological (ER) and magnetorheolgical (MR) fluids can be analyzed under assumptions of quasi-steady, fully developed flow behavior. Models that have been used to characterize ER and MR dampers include the Bingham-plastic, the Herschel-Bulkley and biviscous models. In the Bingham-plastic and the Herschel-Bulkley models, the fluid exhibits rigid behavior in the preyield flow region. The difference between these two models lie in the modeling of the postyield behavior. In the case of the Bingham-plastic model, the postyield behavior is such that the shear stress is proportional to the shear rate. In contrast, the Herschel-Bulkley model assumes that the shear stress is proportional to a power law of the shearrate. In the biciscous model, the relationship between the shear stres and shear rate is linear in both the preyield and postyield regions with constant values of viscosities for the two regions. However, the preyield flow behavior exhibits a much high viscosity than that in the postyield. In the propose model, the assumption of preyield rigid behavior within the Herschel-Bulkley model has been relaxed while the postyield relationship based on the power law has been retained. Here the fluid undergoes Newtonian preyield viscous flow and has a non-Newtonian postyield behavior. Based on this model, we have analyzed the performance of a rectangular duct ER or MR valve. Typical results include shear stress and velocity profiles across the valve gap, equivalent damping and damping coefficients.

Development of a shear force measurement dummy for seat comfort.

Directory of Open Access Journals (Sweden)

Seong Guk Kim

Full Text Available Seat comfort is one of the main factors that consumers consider when purchasing a car. In this study, we develop a dummy with a shear-force sensor to evaluate seat comfort. The sensor has dimensions of 25 mm × 25 mm × 26 mm and is made of S45C. Electroless nickel plating is employed to coat its surface in order to prevent corrosion and oxidation. The proposed sensor is validated using a qualified load cell and shows high accuracy and precision (measurement range: -30-30 N; sensitivity: 0.1 N; linear relationship: R = 0.999; transverse sensitivity: <1%. The dummy is manufactured in compliance with the SAE standards (SAE J826 and incorporates shear sensors into its design. We measure the shear force under four driving conditions and at five different speeds using a sedan; results showed that the shear force increases with speed under all driving conditions. In the case of acceleration and deceleration, shear force significantly changes in the lower body of the dummy. During right and left turns, it significantly changes in the upper body of the dummy.

INCREASES IN CORE TEMPERATURE COUNTERBALANCE EFFECTS OF HEMOCONCENTRATION ON BLOOD VISCOSITY DURING PROLONGED EXERCISE IN THE HEAT

Science.gov (United States)

Buono, Michael J.; Krippes, Taylor; Kolkhorst, Fred W.; Williams, Alexander T.; Cabrales, Pedro

2015-01-01

Previous studies have reported that blood viscosity is significantly increased following exercise. However, these studies measured both pre- and post-exercise blood viscosity at 37 °C even though core and blood temperatures would be expected to have increased during the exercise. Consequently, the effect of exercise-induced hyperthermia on mitigating change in blood viscosity may have been missed. The purpose of this study was to isolate the effects of exercise-induced hemoconcentration and hyperthermia, as well as determine their combined effects, on blood viscosity. Nine subjects performed 2 h of moderate-intensity exercise in the heat (37 °C, 40% rH), which resulted in significant increases from pre-exercise values for rectal temperature (37.11 ± 0.35 °C to 38.76 ± 0.13 °C), hemoconcentration (hematocrit = 43.6 ± 3.6% to 45.6 ± 3.5%), and dehydration (Δbody weight = −3.6 ± 0.7%). Exercise-induced hemoconcentration significantly (P viscosity by 9% (3.97 to 4.30 cP at 300 s−1) while exercise-induced hyperthermia significantly decreased blood viscosity by 7% (3.97 to 3.70 cP at 300 s−1). However, when both factors were considered together, there was no overall change in blood viscosity (3.97 to 4.03 cP at 300 s−1). The effects of exercise-induced hemoconcentration, increased plasma viscosity, and increased red blood cell aggregation, all of which increased blood viscosity, were counterbalanced by increased RBC deformability (e.g., RBC membrane shear elastic modulus and elongation index) caused by the hyperthermia. Thus, blood viscosity remained unchanged following prolonged moderate-intensity exercise in the heat. PMID:26682653

Possible ambiguities when testing viscosity in compendial monographs - characterisation of grades of cellulose ethers.

Science.gov (United States)

Doelker, E

2010-10-01

The European Pharmacopoeia (Ph. Eur.) monographs for the water-soluble cellulose ethers require viscosity determination, either in the "Tests" section or in the non-mandatory "Functionality-related characteristics" section. Although the derivatives are chemically closely related and used for similar applications, the viscosity tests strongly differ. Some monographs generically speak of the rotating viscometer method (2.2.10) and a fixed shear rate (e.g. 10 s-1), which would necessitate an absolute measuring system, while others recommend the capillary viscometer method for product grades of less than 600 mPa∙s and the rotating viscometer method and given operating conditions for grades of higher nominal viscosity. Viscometer methods also differ between the United States Pharmacopeia/National Formulary (USP/NF) and the Japanese Pharmacopoeia (JP) monographs. In addition, for some cellulose ethers the tests sometimes diverge from one pharmacopoeia to the other, although the three compendiums are in a harmonisation process. But the main issue is that the viscometer methods originally employed by the product manufacturers are often not those described in the corresponding monographs and generally vary from one manufacturer to the other. The aim of this study was therefore to investigate whether such a situation could invalidate the present pharmacopoeial requirements. 2 per cent solutions of several viscosity grades of hydroxyethylcellulose, hypromellose and methylcellulose were prepared and their (apparent) viscosity determined using both relative and absolute viscometer methods. The viscometer method used not only affects the measured viscosity but experimental values generally do not correspond to the product nominal viscosities. It emerges that, in contrast to Newtonian solutions (i.e. those of grades of up to ca. 50 mPa∙s nominal viscosity), some of the viscometer methods currently specified in the monographs are not able unambiguously to characterise the

Shear-Induced Membrane Fusion in Viscous Solutions

KAUST Repository

Kogan, Maxim

2014-05-06

Large unilamellar lipid vesicles do not normally fuse under fluid shear stress. They might deform and open pores to relax the tension to which they are exposed, but membrane fusion occurring solely due to shear stress has not yet been reported. We present evidence that shear forces in a viscous solution can induce lipid bilayer fusion. The fusion of 1,2-dioleoyl-sn-glycero-3- phosphocholine (DOPC) liposomes is observed in Couette flow with shear rates above 3000 s-1 provided that the medium is viscous enough. Liposome samples, prepared at different viscosities using a 0-50 wt % range of sucrose concentration, were studied by dynamic light scattering, lipid fusion assays using Förster resonance energy transfer (FRET), and linear dichroism (LD) spectroscopy. Liposomes in solutions with 40 wt % (or more) sucrose showed lipid fusion under shear forces. These results support the hypothesis that under suitable conditions lipid membranes may fuse in response to mechanical-force- induced stress. © 2014 American Chemical Society.

Numerical study of shear thickening fluid with discrete particles embedded in a base fluid

Directory of Open Access Journals (Sweden)

W Zhu

2016-09-01

Full Text Available The Shear Thickening Fluid (STF is a dilatant material, which displays non-Newtonian characteristics in its unique ability to transit from a low viscosity fluid to a high viscosity fluid. The research performed investigates the STF behavior by modeling and simulation of the interaction between the base flow and embedded rigid particles when subjected to shear stress. The model considered the Lagrangian description of the rigid particles and the Eulerian description of fluid flow. The numerical analysis investigated key parameters such as applied flow acceleration, particle distribution and arrangement, volume concentration of particles, particle size, shape and their behavior in a Newtonian and non-Newtonian fluid base. The fluid-particle interaction model showed that the arrangement, size, shape and volume concentration of the particles had a significant effect on the behavior of the STF. Although non-conclusive, the addition of particles in non-Newtonian fluids showed a promising trend of improved shear thickening effects at high shear strain rates.

Clustering of color sources and the shear viscosity of the QGP in heavy ion collisions at RHIC and LHC energies

Energy Technology Data Exchange (ETDEWEB)

Dias de Deus, J. [Instituto Superior Tecnico, CENTRA, Lisbon (Portugal); Hirsch, A.S.; Scharenberg, R.P.; Srivastava, B.K. [Purdue University, Department of Physics, West Lafayette, IN (United States); Pajares, C. [Universidale de Santiago de Compostela and Instituto Galego de Fisica de Atlas Enerxias (IGFAE), Departamento de Fisica de Particulas, Santiago, de Compostela (Spain)

2012-08-15

We present our results on the shear viscosity to entropy ratio ({eta}/s) in the framework of the clustering of the color sources of the matter produced at RHIC and LHC energies. The onset of de-confinement transition is identified by the spanning percolating cluster in 2D percolation. The relativistic kinetic theory relation for {eta}/s is evaluated using the initial temperature (T) and the mean free path ({lambda}{sub mfp}). The analytic expression for {eta}/s covers a wide temperature range. At T{proportional_to}150 MeV below the hadron to QGP transition temperature of {proportional_to}168 MeV, with increasing temperatures the {eta}/s value drop sharply and reaches a broad minimum {eta}/s{proportional_to}0.20 at T{proportional_to}175-185 MeV. Above this temperature {eta}/s grows slowly. The measured values of {eta}/s are 0.204{+-}0.020 and 0.262{+-}0.026 at the initial temperature of 193.6{+-}3 MeV from central Au+Au collisions at {radical}(s{sub NN})=200{proportional_to}GeV (RHIC) and 262.2{+-}13 MeV in central Pb+Pb collisions at {radical}(s{sub NN})= 2.76{proportional_to}TeV (LHC). These {eta}/s values are 2.5 and 3.3 times the AdS/CFT conjectured lower bound 1/4{pi} but are consistent with theoretical {eta}/s estimates for a strongly coupled QGP. (orig.)

Rheological Behavior of Tomato Fiber Suspensions Produced by High Shear and High Pressure Homogenization and Their Application in Tomato Products

Science.gov (United States)

Sun, Ping; Adhikari, Benu P.; Li, Dong

2018-01-01

This study investigated the effects of high shear and high pressure homogenization on the rheological properties (steady shear viscosity, storage and loss modulus, and deformation) and homogeneity in tomato fiber suspensions. The tomato fiber suspensions at different concentrations (0.1%–1%, w/w) were subjected to high shear and high pressure homogenization and the morphology (distribution of fiber particles), rheological properties, and color parameters of the homogenized suspensions were measured. The homogenized suspensions were significantly more uniform compared to unhomogenized suspension. The homogenized suspensions were found to better resist the deformation caused by external stress (creep behavior). The apparent viscosity and storage and loss modulus of homogenized tomato fiber suspension are comparable with those of commercial tomato ketchup even at the fiber concentration as low as 0.5% (w/w), implying the possibility of using tomato fiber as thickener. The model tomato sauce produced using tomato fiber showed desirable consistency and color. These results indicate that the application of tomato fiber in tomato-based food products would be desirable and beneficial. PMID:29743890

Dynamics of shear-induced ATP release from red blood cells.

Science.gov (United States)

Wan, Jiandi; Ristenpart, William D; Stone, Howard A

2008-10-28

Adenosine triphosphate (ATP) is a regulatory molecule for many cell functions, both for intracellular and, perhaps less well known, extracellular functions. An important example of the latter involves red blood cells (RBCs), which help regulate blood pressure by releasing ATP as a vasodilatory signaling molecule in response to the increased shear stress inside arterial constrictions. Although shear-induced ATP release has been observed widely and is believed to be triggered by deformation of the cell membrane, the underlying mechanosensing mechanism inside RBCs is still controversial. Here, we use an in vitro microfluidic approach to investigate the dynamics of shear-induced ATP release from human RBCs with millisecond resolution. We demonstrate that there is a sizable delay time between the onset of increased shear stress and the release of ATP. This response time decreases with shear stress, but surprisingly does not depend significantly on membrane rigidity. Furthermore, we show that even though the RBCs deform significantly in short constrictions (duration of increased stress <3 ms), no measurable ATP is released. This critical timescale is commensurate with a characteristic membrane relaxation time determined from observations of the cell deformation by using high-speed video. Taken together our results suggest a model wherein the retraction of the spectrin-actin cytoskeleton network triggers the mechanosensitive ATP release and a shear-dependent membrane viscosity controls the rate of release.

Measurements of the viscosity of carbon dioxide at temperatures from (253.15 to 473.15) K with pressures up to 1.2 MPa

International Nuclear Information System (INIS)

Schäfer, Michael; Richter, Markus; Span, Roland

2015-01-01

Highlights: • A new rotating-body viscometer for the low-pressure region was presented. • A viscosity dependent offset was compensated by calibrating the viscometer. • The viscosity of carbon dioxide was measured at low pressures. • Measurements were carried out from T = (253.15 to 473.15) K with p ≤ 1.2 MPa. • The relative expanded combined uncertainty (k = 2) was U r,c (η) = (0.20 to 0.41)%. - Abstract: The viscosity of carbon dioxide was measured over the temperature range T = (253.15 to 473.15) K with pressures up to 1.2 MPa utilizing a new rotating-body viscometer. The relative expanded combined uncertainty (k = 2) in viscosity (including uncertainties of temperature and pressure) was (0.20 to 0.41)%. The instrument was specifically designed for measurements at low gas densities and enables measurements of the dynamic viscosity at temperatures between T = 253.15 K and T = 473.15 K with pressures up to 2 MPa. For carbon dioxide, the fluid specific measuring range with regard to pressure was limited to 1.2 MPa due to the formation of disturbing vortices inside the measuring cell at higher pressures. The model function for the viscosity measurement was extended in such a way that the dynamic viscosity was measured relative to helium. Therefore, the influence of the geometry of the concentric cylindrical system inside the measuring cell became almost negligible. Moreover, a systematic offset resulting from a small but inevitable eccentricity of the cylindrical system was compensated for. The residual damping, usually measured in vacuum, was calibrated in the entire temperature range using viscosity values of helium, neon and argon calculated ab initio; at T = 298.15 K recommended reference values were used. A viscosity dependent offset of the measured viscosities, which was observed in previously published data, did not occur when using the calibrated residual damping. The new carbon dioxide results were compared to other experimental literature data

Nano-viscosity of supercooled liquid measured by fluorescence correlation spectroscopy: Pressure and temperature dependence and the density scaling

Science.gov (United States)

Meier, G.; Gapinski, J.; Ratajczyk, M.; Lettinga, M. P.; Hirtz, K.; Banachowicz, E.; Patkowski, A.

2018-03-01

The Stokes-Einstein relation allows us to calculate apparent viscosity experienced by tracers in complex media on the basis of measured self-diffusion coefficients. Such defined nano-viscosity values can be obtained through single particle techniques, like fluorescence correlation spectroscopy (FCS) and particle tracking (PT). In order to perform such measurements, as functions of pressure and temperature, a new sample cell was designed and is described in this work. We show that this cell in combination with a long working distance objective of the confocal microscope can be used for successful FCS, PT, and confocal imaging experiments in broad pressure (0.1-100 MPa) and temperature ranges. The temperature and pressure dependent nano-viscosity of a van der Waals liquid obtained from the translational diffusion coefficient measured in this cell by means of FCS obeys the same scaling as the rotational relaxation and macro-viscosity of the system.

Kubo formulae for the shear and bulk viscosity relaxation times and the scalar field theory shear $\\tau_\\pi$ calculation

OpenAIRE

Czajka, Alina; Jeon, Sangyong

2017-01-01

In this paper we provide a quantum field theoretical study on the shear and bulk relaxation times. First, we find Kubo formulas for the shear and the bulk relaxation times, respectively. They are found by examining response functions of the stress-energy tensor. We use general properties of correlation functions and the gravitational Ward identity to parametrize analytical structures of the Green functions describing both sound and diffusion mode. We find that the hydrodynamic limits of the r...

Photo-oxidation of LDPE: Effects on elongational viscosity

Science.gov (United States)

Rolón-Garrido, Víctor H.; Wagner, Manfred H.

2013-04-01

Sheets of low-density polyethylene (LDPE) were photo-oxidatively treated at room temperature, and subsequently characterized rheologically in the melt state by shear and uniaxial extensional experiments. For photo-oxidation, a xenon lamp was used to irradiate the samples for times between 1 day and 6 weeks. Linear-viscoelastic characterization was performed in a temperature range of 130 to 220°C to obtain the master curve at 170°C, the reference temperature at which the elongational viscosities were measured. Linear viscoelasticity is increasingly affected by increasing photo-oxidation due to crosslinking of LDPE, as corroborated by an increasing gel fraction as determined by a solvent extraction method. The elongational measurements reveal a strong enhancement of strain hardening until a saturation level is achieved. The elongational data are analyzed in the frame work of two constitutive equations, the rubber-like liquid and the molecular stress function models. Within the experimental window, time-deformation separability is confirmed for all samples, independent of the degree of photo-oxidation.

Shear thinning behavior of monolayer liquid lubricant films measured by fiber wobbling method

International Nuclear Information System (INIS)

Hamamoto, Y; Itoh, S; Fukuzawa, K; Zhang, H

2010-01-01

It is essential to clarify mechanical properties of monolayer lubricant films coated on magnetic disks under shearing motion for designing future hard disk drives with ultra-low flying height. Many of previous researchers reported that strong shear rate dependence of viscoelasticity was one of the typical phenomena observed with molecularly thin liquid films. However, it has not been clarified whether or not perfluoropolyether (PFPE) lubricant films, which are used for the head-disk interface (HDI) lubrication, show shear thinning behavior under actual HDI conditions. In this study, we used the fiber wobbling method that can achieve both highly-sensitive shear force measurement and precise gap control and measured shear rate dependence of viscoelastic properties of monolayer PFPE films coated on the magnetic disk. Our experimental results showed that shear thinning does occur at high shear rate ranged from 10 2 to 10 6 s -1 .

Non-perturbative unitarity constraints on the ratio of shear viscosity to entropy density in UV complete theories with a gravity dual

CERN Document Server

Brustein, Ram

2011-01-01

We reconsider, from a novel perspective, how unitarity constrains the corrections to the ratio of shear viscosity \\eta\\ to entropy density s. We start with higher-derivative extensions of Einstein gravity in asymptotically anti-de Sitter spacetimes. It is assumed that these theories are derived from string theory and thus have a unitary UV completion that is dual to a unitary, UV-complete boundary gauge theory. We then propose that the gravitational perturbations about a solution of the UV complete theory are described by an effective theory whose linearized equations of motion have at most two time derivatives. Our proposal leads to a concrete prescription for the calculation of \\eta/s for theories of gravity with arbitrary higher-derivative corrections. The resulting ratio can take on values above or below 1/4\\pi\\ and is consistent with all the previous calculations, even though our reasoning is substantially different. For the purpose of calculating \\eta/s, our proposal also leads to only two possible cand...

Direct test of a nonlinear constitutive equation for simple turbulent shear flows using DNS data

Science.gov (United States)

Schmitt, François G.

2007-10-01

Several nonlinear constitutive equations have been proposed to overcome the limitations of the linear eddy-viscosity models to describe complex turbulent flows. These nonlinear equations have often been compared to experimental data through the outputs of numerical models. Here we perform a priori analysis of nonlinear eddy-viscosity models using direct numerical simulation (DNS) of simple shear flows. In this paper, the constitutive equation is directly checked using a tensor projection which involves several invariants of the flow. This provides a 3 terms development which is exact for 2D flows, and a best approximation for 3D flows. We provide the quadratic nonlinear constitutive equation for the near-wall region of simple shear flows using DNS data, and estimate their coefficients. We show that these coefficients have several common properties for the different simple shear flow databases considered. We also show that in the central region of pipe flows, where the shear rate is very small, the coefficients of the constitutive equation diverge, indicating the failure of this representation for vanishing shears.

Computation of shear-induced collective-diffusivity in emulsions

Science.gov (United States)

Malipeddi, Abhilash Reddy; Sarkar, Kausik

2017-11-01

The shear-induced collective-diffusivity of drops in an emulsion is calculated through simulation. A front-tracking finite difference method is used to integrate the Navier-Stokes equations. When a cloud of drops is subjected to shear flow, after a certain time, the width of the cloud increases with the 1/3 power of time. This scaling of drop-cloud-width with time is characteristic of (sub-)diffusion that arises from irreversible two-drop interactions. The collective diffusivity is calculated from this relationship. A feature of the procedure adopted here is the modest computational requirement, wherein, a few drops ( 70) in shear for short time ( 70 strain) is found to be sufficient to get a good estimate. As far as we know, collective-diffusivity has not been calculated for drops through simulation till now. The computed values match with experimental measurements reported in the literature. The diffusivity in emulsions is calculated for a range of Capillary (Ca) and Reynolds (Re) numbers. It is found to be a unimodal function of Ca , similar to self-diffusivity. A sub-linear increase of the diffusivity with Re is seen for Re < 5 . This work has been limited to a viscosity matched case.

On the Measurements of Numerical Viscosity and Resistivity in Eulerian MHD Codes

Energy Technology Data Exchange (ETDEWEB)

Rembiasz, Tomasz; Obergaulinger, Martin; Cerdá-Durán, Pablo; Aloy, Miguel-Ángel [Departamento de Astronomía y Astrofísica, Universidad de Valencia, C/Dr. Moliner 50, E-46100 Burjassot (Spain); Müller, Ewald, E-mail: tomasz.rembiasz@uv.es [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany)

2017-06-01

We propose a simple ansatz for estimating the value of the numerical resistivity and the numerical viscosity of any Eulerian MHD code. We test this ansatz with the help of simulations of the propagation of (magneto)sonic waves, Alfvén waves, and the tearing mode (TM) instability using the MHD code Aenus. By comparing the simulation results with analytical solutions of the resistive-viscous MHD equations and an empirical ansatz for the growth rate of TMs, we measure the numerical viscosity and resistivity of Aenus. The comparison shows that the fast magnetosonic speed and wavelength are the characteristic velocity and length, respectively, of the aforementioned (relatively simple) systems. We also determine the dependence of the numerical viscosity and resistivity on the time integration method, the spatial reconstruction scheme and (to a lesser extent) the Riemann solver employed in the simulations. From the measured results, we infer the numerical resolution (as a function of the spatial reconstruction method) required to properly resolve the growth and saturation level of the magnetic field amplified by the magnetorotational instability in the post-collapsed core of massive stars. Our results show that it is most advantageous to resort to ultra-high-order methods (e.g., the ninth-order monotonicity-preserving method) to tackle this problem properly, in particular, in three-dimensional simulations.

Effect of magnetic field on thermal conductivity and viscosity of a magnetic nanofluid loaded with carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

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.

New instrument for on-line viscosity measurement of fermentation media.

Science.gov (United States)

Picque, D; Corrieu, G

1988-01-01

In an attempt to resolve the difficult problem of on-line determination of the viscosity of non-Newtonian fermentation media, the authors have used a vibrating rod sensor mounted on a bioreactor. The sensor signal decreases nonlinearly with increased apparent viscosity. Electronic filtering of the signal damps the interfering effect of aeration and mechanical agitation. Sensor drift is very low (0.03% of measured value per hour). On the rheological level the sensor is primarily an empirical tool that must be specifically calibrated for each fermentation process. Once this is accomplished, it becomes possible to establish linear or second-degree correlations between the electrical signal from the sensor and the essential parameters of the fermentation process in question (pH of a fermented milk during acidification, concentration of extra cellular polysaccharide). In addition, by applying the power law to describe the rheological behavior of fermentation media, we observe a second-order polynomial correlation between the sensor signal and the behavior index (n).

Investigations on the detection of irradiated food by measuring the viscosity of suspended spices and dried vegetables

Science.gov (United States)

Heide, L.; Nürnberger, E.; Bögl, K. W.

Studies on the viscosity behavior were performed with 20 different spices or dried vegetables. In nine spices (cinnamon, ginger, mustard seed, celery, onions, shallots, lemon peel, black and white pepper) differences between unirradiated and irradiated samples were observed. Further lots were investigated to estimate the variations of viscosity depending on the origin of the samples. Additional storage experiments showed that measuring the viscosity may be a simple method to identify some radiation treated spices even after years.

A microfluidic device for simultaneous measurement of viscosity and flow rate of blood in a complex fluidic network

OpenAIRE

Jun Kang, Yang; Yeom, Eunseop; Lee, Sang-Joon

2013-01-01

Blood viscosity has been considered as one of important biophysical parameters for effectively monitoring variations in physiological and pathological conditions of circulatory disorders. Standard previous methods make it difficult to evaluate variations of blood viscosity under cardiopulmonary bypass procedures or hemodialysis. In this study, we proposed a unique microfluidic device for simultaneously measuring viscosity and flow rate of whole blood circulating in a complex fluidic network i...

Shape and shear guide sperm cells spiraling upstream

Science.gov (United States)

Kantsler, Vasily; Dunkel, Jorn; Goldstein, Raymond E.

2014-11-01

A major puzzle in biology is how mammalian sperm determine and maintain the correct swimming direction during the various phases of the sexual reproduction process. Currently debated mechanisms for sperm long range travel vary from peristaltic pumping to temperature sensing (thermotaxis) and direct response to fluid flow (rheotaxis), but little is known quantitatively about their relative importance. Here, we report the first quantitative experimental study of mammalian sperm rheotaxis. Using microfluidic devices, we investigate systematically the swimming behavior of human and bull sperm over a wide range of physiologically relevant shear rates and viscosities. Our measurements show that the interplay of fluid shear, steric surface-interactions and chirality of the flagellar beat leads to a stable upstream spiraling motion of sperm cells, thus providing a generic and robust rectification mechanism to support mammalian fertilization. To rationalize these findings, we identify a minimal mathematical model that is capable of describing quantitatively the experimental observations.

A microfluidic device for simultaneous measurement of viscosity and flow rate of blood in a complex fluidic network.

Science.gov (United States)

Jun Kang, Yang; Yeom, Eunseop; Lee, Sang-Joon

2013-01-01

Blood viscosity has been considered as one of important biophysical parameters for effectively monitoring variations in physiological and pathological conditions of circulatory disorders. Standard previous methods make it difficult to evaluate variations of blood viscosity under cardiopulmonary bypass procedures or hemodialysis. In this study, we proposed a unique microfluidic device for simultaneously measuring viscosity and flow rate of whole blood circulating in a complex fluidic network including a rat, a reservoir, a pinch valve, and a peristaltic pump. To demonstrate the proposed method, a twin-shaped microfluidic device, which is composed of two half-circular chambers, two side channels with multiple indicating channels, and one bridge channel, was carefully designed. Based on the microfluidic device, three sequential flow controls were applied to identify viscosity and flow rate of blood, with label-free and sensorless detection. The half-circular chamber was employed to achieve mechanical membrane compliance for flow stabilization in the microfluidic device. To quantify the effect of flow stabilization on flow fluctuations, a formula of pulsation index (PI) was analytically derived using a discrete fluidic circuit model. Using the PI formula, the time constant contributed by the half-circular chamber is estimated to be 8 s. Furthermore, flow fluctuations resulting from the peristaltic pumps are completely removed, especially under periodic flow conditions within short periods (T viscosity with respect to varying flow rate conditions [(a) known blood flow rate via a syringe pump, (b) unknown blood flow rate via a peristaltic pump]. As a result, the flow rate and viscosity of blood can be simultaneously measured with satisfactory accuracy. In addition, the proposed method was successfully applied to identify the viscosity of rat blood, which circulates in a complex fluidic network. These observations confirm that the proposed method can be used for

Giant deviation of a relaxation time from generalized Newtonian theory in discontinuous shear thickening suspensions

Science.gov (United States)

Maharjan, Rijan; Brown, Eric

2017-12-01

We investigated the transient relaxation of a discontinuous shear thickening (DST) suspension of cornstarch in water. We performed two types of relaxation experiments starting from a steady shear in a parallel-plate rheometer, followed either by stopping the top plate rotation and measuring the transient torque relaxation or by removing the torque on the plate and measuring the transient rotation of the tool. We found that at low effective weight fraction ϕeffmodel. The regime where the relaxation was inconsistent with the generalized Newtonian model was the same where we found positive normal stress during relaxation, and in some cases we found an oscillatory response, suggestive of a solidlike structure consisting of a system-spanning contact network of particles. This regime also corresponds to the same packing fraction range where we consistently found discontinuous shear thickening in rate-controlled, steady-state measurements. The relaxation time in this range scales with the inverse of the critical shear rate at the onset of shear thickening, which may correspond to a contact relaxation time for nearby particles in the structure to flow away from each other. In this range, the relaxation time was the same in both stress- and rate-controlled relaxation experiments, indicating the relaxation time is more intrinsic than an effective viscosity in this range and is needed in addition to the steady-state viscosity function to describe transient flows. The discrepancy between the measured relaxation times and the generalized Newtonian prediction was found to be as large as four orders of magnitude, and extrapolations diverge in the limit as ϕeff→ϕc as the generalized Newtonian prediction approaches 0. This quantitative discrepancy indicates the relaxation is not controlled by the dissipative terms in the constitutive relation. At the highest weight fractions, the relaxation time scales were measured to be on the order of ˜1 s. The fact that this time scale is

Synergy of plasma resistivity and electron viscosity in mediating double tearing modes in cylindrical plasmas

International Nuclear Information System (INIS)

He Zhixiong; He, H D; Long, Y X; Mou, Z Z; Dong, J Q; Gao Zhe

2010-01-01

The linear behaviors of the double tearing mode (DTM) mediated by parallel electron viscosity and plasma resistivity in cylindrical plasmas with reversed magnetic shear and thus two resonant rational flux surfaces are numerically investigated in this paper. It is shown that DTMs mediated by electron viscosity alone behave similarly to the DTMs mediated by resistivity alone. DTMs mediated by electron viscosity are found to be enhanced by plasma resistivity, which is in such a range that the growth rate of the modes induced by the latter alone is comparable with that of the modes mediated by the former alone, and vice versa. Otherwise the growth rate of the modes is equal to the higher of the modes mediated by resistivity or electron viscosity alone when both resistivity and electron viscosity are taken into account. The enhancement is found to be closely related to the profiles of the stream function.

Effect of viscosity on tear drainage and ocular residence time.

Science.gov (United States)

Zhu, Heng; Chauhan, Anuj

2008-08-01

An increase in residence time of dry eye medications including artificial tears will likely enhance therapeutic benefits. The drainage rates and the residence time of eye drops depend on the viscosity of the instilled fluids. However, a quantitative understanding of the dependence of drainage rates and the residence time on viscosity is lacking. The current study aims to develop a mathematical model for the drainage of Newtonian fluids and also for power-law non-Newtonian fluids of different viscosities. This study is an extension of our previous study on the mathematical model of tear drainage. The tear drainage model is modified to describe the drainage of Newtonian fluids with viscosities higher than the tear viscosity and power-law non-Newtonian fluids with rheological parameters obtained from fitting experimental data in literature. The drainage rate through canaliculi was derived from the modified drainage model and was incorporated into a tear mass balance to calculate the transients of total solute quantity in ocular fluids and the bioavailability of instilled drugs. For Newtonian fluids, increasing the viscosity does not affect the drainage rate unless the viscosity exceeds a critical value of about 4.4 cp. The viscosity has a maximum impact on drainage rate around a value of about 100 cp. The trends are similar for shear thinning power law fluids. The transients of total solute quantity, and the residence time agrees at least qualitatively with experimental studies. A mathematical model has been developed for the drainage of Newtonian fluids and power-law fluids through canaliculi. The model can quantitatively explain different experimental observations on the effect of viscosity on the residence of instilled fluids on the ocular surface. The current study is helpful for understanding the mechanism of fluid drainage from the ocular surface and for improving the design of dry eye treatments.

Comparison of parallel viscosity with neoclassical theory

International Nuclear Information System (INIS)

Ida, K.; Nakajima, N.

1996-04-01

Toroidal rotation profiles are measured with charge exchange spectroscopy for the plasma heated with tangential NBI in CHS heliotron/torsatron device to estimate parallel viscosity. The parallel viscosity derived from the toroidal rotation velocity shows good agreement with the neoclassical parallel viscosity plus the perpendicular viscosity. (μ perpendicular = 2 m 2 /s). (author)

Methods of viscosity measurements in sealed ampoules

Science.gov (United States)

Mazuruk, Konstantin

1999-07-01

Viscosity of semiconductors and metallic melts is usually measured by oscillating cup method. This method utilizes the melts contained in vacuum sealed silica ampoules, thus the problems related to volatility, contamination, and high temperature and pressure can be alleviate. In a typical design, the time required for a single measurement is of the order of one hour. In order to reduce this time to a minute range, a high resolution angular detection system is implemented in our design of the viscometer. Furthermore, an electromagnet generating a rotational magnetic field (RMF) is incorporated into the apparatus. This magnetic field can be used to remotely and nonintrusively measure the electrical conductivity of the melt. It can also be used to induce a well controlled rotational flow in the system. The transient behavior of this flow can potentially yield of the fluid. Based on RMF implementation, two novel viscometry methods are proposed in this work: a) the transient torque method, b) the resonance method. A unified theoretical approach to the three methods is presented along with the initial test result of the constructed apparatus. Advantages of each of the method are discussed.

Development, implementation, and characterization of a standalone embedded viscosity measurement system based on the impedance spectroscopy of a vibrating wire sensor

Science.gov (United States)

Santos, José; Janeiro, Fernando M.; Ramos, Pedro M.

2015-10-01

This paper presents an embedded liquid viscosity measurement system based on a vibrating wire sensor. Although multiple viscometers based on different working principles are commercially available, there is still a market demand for a dedicated measurement system capable of performing accurate, fast measurements and requiring little or no operator training for simple systems and solution monitoring. The developed embedded system is based on a vibrating wire sensor that works by measuring the impedance response of the sensor, which depends on the viscosity and density of the liquid in which the sensor is immersed. The core of the embedded system is a digital signal processor (DSP) which controls the waveform generation and acquisitions for the measurement of the impedance frequency response. The DSP also processes the acquired waveforms and estimates the liquid viscosity. The user can interact with the measurement system through a keypad and an LCD or through a computer with a USB connection for data logging and processing. The presented system is tested on a set of viscosity standards and the estimated values are compared with the standard manufacturer specified viscosity values. A stability study of the measurement system is also performed.

Development, implementation, and characterization of a standalone embedded viscosity measurement system based on the impedance spectroscopy of a vibrating wire sensor

International Nuclear Information System (INIS)

Santos, José; Ramos, Pedro M; Janeiro, Fernando M

2015-01-01

This paper presents an embedded liquid viscosity measurement system based on a vibrating wire sensor. Although multiple viscometers based on different working principles are commercially available, there is still a market demand for a dedicated measurement system capable of performing accurate, fast measurements and requiring little or no operator training for simple systems and solution monitoring. The developed embedded system is based on a vibrating wire sensor that works by measuring the impedance response of the sensor, which depends on the viscosity and density of the liquid in which the sensor is immersed. The core of the embedded system is a digital signal processor (DSP) which controls the waveform generation and acquisitions for the measurement of the impedance frequency response. The DSP also processes the acquired waveforms and estimates the liquid viscosity. The user can interact with the measurement system through a keypad and an LCD or through a computer with a USB connection for data logging and processing. The presented system is tested on a set of viscosity standards and the estimated values are compared with the standard manufacturer specified viscosity values. A stability study of the measurement system is also performed. (paper)

Viscosity sinergism of hydrozypropmethyl and carboxy methyl cellulose

Directory of Open Access Journals (Sweden)

Katona Jaroslav M.

2008-01-01

Full Text Available Rheology modifiers are common constituents of food, cosmetic and pharmaceutic products. Often, by using two or more of them, better control of the product rheological properties can be achieved. In this work, rheological properties of hydroxypropymethyl cellulose (HPMC and sodium carboxymethyl cellulose (NaCMC solutions of different concentrations were investigated and compared to the flow properties of 1% HPMC/NaCMC binary mixtures at various HPMC/NaCMC mass ratios. Solutions of HPMC and NaCMC were found to be pseudoplastic, where pseudoplasticity increases with increase in the macromolecules concentration. Changes of the degree of pseudoplasticity, n as well as the coefficient of consistency, K with the concentration are more pronounced in HPMC solutions when compared to the NaCMC ones. This is mostly due to the ability of HPMC molecules to associate with each other at concentrations above critical overlap concentration, c , and greater flexibility of macromolecular chains. Binary mixtures of HPMC/NaCMC were also found to be pseudoplastic. Experimentally obtained viscosities of the mixture were proved to be larger than theoretically expected ones, indicating viscosity synergism as a consequence of HPMC-NaCMC interaction. Maximum in synergy was observed when HPMC/NaCMC mass ratio was 0.4/0.6, no matter of the shear rate applied. On the other hand, it was found that relative positive deviation, RPD decreases when shear rate is increased.

Viscosity measurement - probably a means for detecting radiation treatment of spices. Viskositaetsmessung - ein Verfahren zur Identifizierung strahlenbehandelter Gewuerze

Energy Technology Data Exchange (ETDEWEB)

Heide, L; Albrich, S; Boegl, K W; Mohr, E; Wichmann, G

1987-12-01

The viscosity of 13 different spices and dried vegetables in total was measured. Optimal conditions were first determined for each product, i.e. concentration, pH-value, temperature, particle size and soaking time. For method evaluation, examinations were primarily performed to study the effect of storage, the reproducibility and the influence of the different varieties of the same spice. In supplement, for pepper, the viscosity was measured as a function of radiation dose. In summation, significant changes in the gel forming capability after irradiation could be observed after preliminary experiments in 8 dried spices (ginger, carrots, leek, cloves, pepper, celery, cinnamon and onions). With 3 spices (ginger, pepper and cinnamon) could the results from examining all different varieties of the same spice be substantiated. An additional influence of storage time on viscosity could not be proved during the investigative period of 8 months. Generally seen, there is no possibility of being able to identify an irradiated spice on the basis of viscosity measurements alone, since the difference between the varieties of one and the same spice is considerably great. However, radiation treatment can be reliably excluded with ginger, pepper and cinnamon, if the viscosities are high (10-20 Pa x s).

Separate measurement of the density and viscosity of a liquid using a quartz crystal microbalance based on admittance analysis (QCM-A)

International Nuclear Information System (INIS)

Itoh, Atsushi; Ichihashi, Motoko

2011-01-01

We previously used a quartz crystal microbalance (QCM) to identify a frequency f 2 that allows measurement of the mass load without being affected by the viscous load of a liquid in the liquid phase. Here, we determined that frequency in order to separately measure the density and viscosity of a Newtonian liquid. Martin et al separately measured the density and viscosity of a liquid by immersing two quartz resonators, i.e. a smooth-surface resonator and a textured-surface resonator, in the liquid. We used a QCM based on admittance analysis (QCM-A) in the current study to separately measure the viscosity and density of a liquid using only a textured-surface resonator. In the current experiments, we measured the density and viscosity of 500 µl of 10%, 30%, and 50% aqueous glycerol solutions and compared the measured values to reference values. The density obtained had an error of ±1.5% of reference values and the viscosity had an error of about ±5% of reference values. Similar results were obtained with 500 µl of 10%, 30%, and 50% ethanol solutions. Measurement was possible with a quartz resonator, so measurements were made with even smaller samples. The density and viscosity of a liquid were successfully determined with an extremely small amount of liquid, i.e. 10 µl, with almost the same precision as when using 500 µl of the liquid

Comparison of erythrocyte dynamics in shear flow under different stress-free configurations

Science.gov (United States)

Cordasco, Daniel; Yazdani, Alireza; Bagchi, Prosenjit

2014-04-01

An open question that has persisted for decades is whether the cytoskeleton of a red blood cell is stress-free or under a stress. This question is important in the context of theoretical modeling of cellular motion under a flowing condition where it is necessary to make an assumption about the stress-free state. Here, we present a 3D numerical study to compare the cell dynamics in a simple shear flow under two different stress-free states, a biconcave discocyte representing the resting shape of the cell, and a nearly spherical oblate shape. We find that whether the stress-free states make a significant difference or not depends on the viscosity of the suspending medium. If the viscosity is close to that of blood plasma, the two stress-free states do not show any significant difference in cell dynamics. However, when the suspending medium viscosity is well above that of the physiological range, as in many in vitro studies, the shear rate separating the tank-treading and tumbling dynamics is observed to be higher for the biconcave stress-free state than the spheroidal state. The former shows a strong shape oscillation with repeated departures from the biconcave shape, while the latter shows a nearly stable biconcave shape. It is found that the cell membrane in the biconcave stress-free state is under a compressive stress and a weaker bending force density, leading to a periodic compression of the cell. The shape oscillation then leads to a higher energy barrier against membrane tank-tread leading to an early transition to tumbling. However, if the cells are released with a large off-shear plane angle, the oscillations can be suppressed due to an azimuthal motion of the membrane along the vorticity direction leading to a redistribution of the membrane points and lowering of the energy barrier, which again results in a nearly similar behavior of the cells under the two different stress-free states. A variety of off-shear plane dynamics is observed, namely, rolling

RheoSAXS studies of anisotropic complex fluids under shear

International Nuclear Information System (INIS)

Silva, J P de; Petermann, D; Kasmi, B; Imperor-Clerc, M; Davidson, P; Pansu, B; Meneau, F; Perez, J; Paineau, E; Bihannic, I; Michot, L J; Baravian, C

2010-01-01

We discuss the application of in-situ rheological small angle X-ray scattering experiments to the study of complex fluids under shear, implemented using custom Couette cylinder rheometers mounted on the SWING beamline of the SOLEIL Synchrotron. We discuss several applications of this technique to the study of phase transitions in nanoparticle doped liquid crystals and shear alignment of clay suspensions. The concurrent capture of rheological and scattering data provides vital information that relates macroscopic properties such as viscosity to the microstructure of the fluid.

Relationship between blood viscosity and infarct size in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention.

Science.gov (United States)

Cecchi, Emanuele; Liotta, Agatina Alessandriello; Gori, Anna Maria; Valente, Serafina; Giglioli, Cristina; Lazzeri, Chiara; Sofi, Francesco; Gensini, Gian Franco; Abbate, Rosanna; Mannini, Lucia

2009-05-15

Previous studies explored the association between hemorheological alterations and acute myocardial infarction, pointing out the role of hematological components on microvascular flow. The aim of this study was to evaluate the association between blood viscosity and infarct size, estimated by creatine kinase (CK) peak activity and cardiac Troponin I (cTnI) peak concentration in ST-segment elevation myocardial infarction (STEMI) patients after primary percutaneous coronary intervention (PCI). The study population included 197 patients with diagnosis of STEMI undergoing PCI. Hemorheological studies were performed by assessing whole blood viscosity (measured at shear rates of 0.512 s(-1) and 94.5 s(-1)) and plasma viscosity using the Rotational Viscosimeter LS 30 and erythrocyte deformability index by Myrenne filtrometer. Significant correlations between CK peak activity, cTnI peak concentration, left ventricular ejection fraction and hemorheological variables were observed. At linear regression analysis (adjusted for age, gender, traditional cardiovascular risk factors, renal dysfunction, timeliness of reperfusion, pre-PCI TIMI flow, infarct location, multivessel disease and previous coronary artery disease) leukocytes and whole blood viscosity at 0.512 s(-1) and 94.5 s(-1) were independently and positively associated with infarct size. These results demonstrate a significant and independent association between hemorheology and infarct size in STEMI patients after PCI suggesting that blood viscosity, in a condition of low flow, might worsen myocardial perfusion leading to an increased infarct size. The measurement of whole blood viscosity in STEMI patients could help to identify those who may benefit from new therapeutic strategies.

Buoyant miscible displacement flow of shear-thinning fluids: Experiments and Simulations

Science.gov (United States)

Ale Etrati Khosroshahi, Seyed Ali; Frigaard, Ian

2017-11-01

We study displacement flow of two miscible fluids with density and viscosity contrast in an inclined pipe. Our focus is mainly on displacements where transverse mixing is not significant and thus a two-layer, stratified flow develops. Our experiments are carried out in a long pipe, covering a wide range of flow-rates, inclination angles and viscosity ratios. Density and viscosity contrasts are achieved by adding Glycerol and Xanthan gum to water, respectively. At each angle, flow rate and viscosity ratio are varied and density contrast is fixed. We identify and map different flow regimes, instabilities and front dynamics based on Fr , Re / Frcosβ and viscosity ratio m. The problem is also studied numerically to get a better insight into the flow structure and shear-thinning effects. Numerical simulations are completed using OpenFOAM in both pipe and channel geometries and are compared against the experiments. Schlumberger, NSERC.

Shear flow generation by Reynolds stress and suppression of resistive g modes

International Nuclear Information System (INIS)

Sugama, H.; Horton, W.

1993-01-01

The authors have investigated suppression of the resistive g mode turbulence by background shear flow produced by the external source and by the fluctuation-induced Reynolds stress. For that purpose, the authors used the model consisting of the equations describing the electrostatic potential φ≡(φ 0 +φ) and the pressure fluctuation p of the resistive g mode, and the equation for the background poloidal flow. They have done the single-helicity nonlinear simulations using the model equations in the sheared slab configuration. They find that, in the nonlinear turbulent regime, significant suppression of the turbulent transport is realized only when the shear flow v' E exceeds that which makes the fastest-growing linear modes marginally stable. With the shear flow which decreases the fastest linear growth rates by about a half, the turbulent transport in the saturated state is about the same as in the case of no shear flow. As seen from the equation for the background flow v E , the relative efficiency of the external flow and the Reynolds stress for producing shear flow depends on the parameter ν. For large ν, the external flow is a dominant contribution to the total background poloidal shear flow although its strength predicted by the neoclassical theory is not enough to suppress the turbulence significantly. On the other hand, for small ν, they observe that, as the fluctuations grow, the Reynolds stress becomes large and suddenly at some critical point in time shear flow much larger than the external one is generated and leads to the significant reduction of the turbulent transport just like that of the L-H transition in tokamak experiments. It is remarkable that the Reynolds stress due to the resistive g mode fluctuations works not as a conventional viscosity term weakening the shear flow but as a negative viscosity term enhancing it

Viscosity Meaurement Technique for Metal Fuels

Energy Technology Data Exchange (ETDEWEB)

Ban, Heng [Utah State Univ., Logan, UT (United States). Mechanical and Aerospace Engineering; Kennedy, Rory [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2015-02-09

Metallic fuels have exceptional transient behavior, excellent thermal conductivity, and a more straightforward reprocessing path, which does not separate out pure plutonium from the process stream. Fabrication of fuel containing minor actinides and rare earth (RE) elements for irradiation tests, for instance, U-20Pu-3Am-2Np-1.0RE-15Zr samples at the Idaho National Laboratory, is generally done by melt casting in an inert atmosphere. For the design of a casting system and further scale up development, computational modeling of the casting process is needed to provide information on melt flow and solidification for process optimization. Therefore, there is a need for melt viscosity data, the most important melt property that controls the melt flow. The goal of the project was to develop a measurement technique that uses fully sealed melt sample with no Americium vapor loss to determine the viscosity of metallic melts and at temperatures relevant to the casting process. The specific objectives of the project were to: develop mathematical models to establish the principle of the measurement method, design and build a viscosity measurement prototype system based on the established principle, and calibrate the system and quantify the uncertainty range. The result of the project indicates that the oscillation cup technique is applicable for melt viscosity measurement. Detailed mathematical models of innovative sample ampoule designs were developed to not only determine melt viscosity, but also melt density under certain designs. Measurement uncertainties were analyzed and quantified. The result of this project can be used as the initial step toward the eventual goal of establishing a viscosity measurement system for radioactive melts.

Viscosity Meaurement Technique for Metal Fuels

International Nuclear Information System (INIS)

Ban, Heng

2015-01-01

Metallic fuels have exceptional transient behavior, excellent thermal conductivity, and a more straightforward reprocessing path, which does not separate out pure plutonium from the process stream. Fabrication of fuel containing minor actinides and rare earth (RE) elements for irradiation tests, for instance, U-20Pu-3Am-2Np-1.0RE-15Zr samples at the Idaho National Laboratory, is generally done by melt casting in an inert atmosphere. For the design of a casting system and further scale up development, computational modeling of the casting process is needed to provide information on melt flow and solidification for process optimization. Therefore, there is a need for melt viscosity data, the most important melt property that controls the melt flow. The goal of the project was to develop a measurement technique that uses fully sealed melt sample with no Americium vapor loss to determine the viscosity of metallic melts and at temperatures relevant to the casting process. The specific objectives of the project were to: develop mathematical models to establish the principle of the measurement method, design and build a viscosity measurement prototype system based on the established principle, and calibrate the system and quantify the uncertainty range. The result of the project indicates that the oscillation cup technique is applicable for melt viscosity measurement. Detailed mathematical models of innovative sample ampoule designs were developed to not only determine melt viscosity, but also melt density under certain designs. Measurement uncertainties were analyzed and quantified. The result of this project can be used as the initial step toward the eventual goal of establishing a viscosity measurement system for radioactive melts.

Nonlinear shear wave in a non Newtonian visco-elastic medium

Energy Technology Data Exchange (ETDEWEB)

Banerjee, D.; Janaki, M. S.; Chakrabarti, N. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064 (India); Chaudhuri, M. [Max-Planck-Institut fuer extraterrestrische Physik, 85741 Garching (Germany)

2012-06-15

An analysis of nonlinear transverse shear wave has been carried out on non-Newtonian viscoelastic liquid using generalized hydrodynamic model. The nonlinear viscoelastic behavior is introduced through velocity shear dependence of viscosity coefficient by well known Carreau-Bird model. The dynamical feature of this shear wave leads to the celebrated Fermi-Pasta-Ulam problem. Numerical solution has been obtained which shows that initial periodic solutions reoccur after passing through several patterns of periodic waves. A possible explanation for this periodic solution is given by constructing modified Korteweg de Vries equation. This model has application from laboratory to astrophysical plasmas as well as in biological systems.

Shear Resistance Properties of Modified Nano-SiO2/AA/AM Copolymer Oil Displacement Agent

Directory of Open Access Journals (Sweden)

Nanjun Lai

2016-12-01

Full Text Available To address the problem regarding poor shear resistance of commonly employed polymers for oil displacement, modified nano-SiO2/AA/AM copolymer (HPMNS oil displacement agents were synthesized using acrylic acid (AA, acrylamide (AM, and modified nano-SiO2 of different modification degrees as raw materials. HPMNS was characterized by means of infrared spectroscopy (IR, nuclear magnetic resonance (1H-NMR, 13C-NMR, dynamic/static light scattering, and scanning electron microscope. A comparative study of the shear resistance properties for partially hydrolyzed polyacrylamide (HPAM and HPMNS was conducted. Compared to HPAM, the introduced hyperbranched structure endowed HPMNS with good shear resistance, which was quantified from the viscosity retention ratio of the polymer solutions. From the perspective of rheological property, HPMNS also showed great shear stability after shearing by a Mixing Speed Governor and porous media shear model. Furthermore, with a higher degree of modification, HPMNS-2 had better shear stability in terms of viscosity and rheological property than HPMNS-1. The phenomena were due to its lower hydrodynamic radius, weight-average molecular weight, and better flexibility of its molecular chains. In addition, upon the indoor displacement test, the resistance factor and residual resistance factor values of HPMNS-2 were higher than those of HPAM. This behavior is beneficial for increasing oil recovery.

Predicting the viscosity of digesta from the physical characteristics of particle suspensions using existing rheological models.

Science.gov (United States)

Hardacre, Allan K; Lentle, Roger G; Yap, Sia-Yen; Monro, John A

2018-05-01

The measurement of the viscosity of digesta is complicated by settling and compositional changes that accompany digestion. The current work determined whether the apparent and relative viscosities ( η a and η r ) of digesta could be accurately determined from the actual and maximum solid volume fractions ( ϕ and ϕ max , respectively) using the Maron-Pierce equation. The rheological properties of digesta from the small intestine of six pigs were determined at a shear rate of 1 s -1 at 37°C. A series of suspensions of plant fibre in a Newtonian liquid (70% aqueous fructose) were made at viscosities similar to pig digesta by adjusting ϕ The relationships between the apparent and relative viscosities ( η a and η r ) and the plant fibre properties; aspect ratio (AR) and ϕ and ϕ max were then determined for digesta and the suspensions. The ARs for the digesta and plant fibre particles were determined using image analysis of scanning electron micrographs and η a from rheometric flow curves at 37°C, ϕ from image analysis and gas pycnometry, and ϕ max from AR and suspension viscosity. The η r of pig digesta and the test suspensions calculated using the Maron-Pierce equation were, with the exception of two outliers, in proportion with η a determined using a rheometer, indicating that η r could be successfully predicted from the Maron-Pierce equation. © 2018 The Author(s).

Effective viscosity of 2D suspensions - Confinement effects

Science.gov (United States)

Peyla, Philippe; Priem, Stephane; Vincent, Doyeux; Farutin, Alexander; Ismail, Mourad

2014-11-01

We study the rheology of a sheared 2D suspension of non-Brownian disks in presence of walls. Although, it is of course possible today with modern computers and powerful algorithms to perform direct numerical simulations that fully account for multiparticle 3D interactions, the analysis of the simple case of a 2D suspension, provides valuable insights and helps to understand 3D results. For instance, we examine the role of particle-wall and particle-particle interactions in determining the rheology of confined sheared suspensions. In addition we evaluate the intrinsic viscosity as well as the contribution of hydrodynamic interactions to the dissipation as a function of a wide range of confinements. Thanks to the direct visualisation of the whole 2D Stokes flow, we are able to give a clear interpretation about the rheology of semi-dilute confined suspensions.

The calculation of viscosity of liquid n-decane and n-hexadecane by the Green-Kubo method

Science.gov (United States)

Cui, S. T.; Cummings, P. T.; Cochran, H. D.

This short commentary presents the result of long molecular dynamics simulation calculations of the shear viscosity of liquid n-decane and n-hexadecane using the Green-Kubo integration method. The relaxation time of the stress-stress correlation function is compared with those of rotation and diffusion. The rotational and diffusional relaxation times, which are easy to calculate, provide useful guides for the required simulation time in viscosity calculations. Also, the computational time required for viscosity calculations of these systems by the Green-Kubo method is compared with the time required for previous non-equilibrium molecular dynamics calculations of the same systems. The method of choice for a particular calculation is determined largely by the properties of interest, since the efficiencies of the two methods are comparable for calculation of the zero strain rate viscosity.

Correlations and the Ring-Kinetic Equation in Dense Sheared Granular Flows

Science.gov (United States)

Kumaran, V.

A formal way of deriving fluctuation-correlation relations in densesheared granular media, starting with the Enskog approximation for the collision integral in the Chapman-Enskog theory, is discussed. The correlation correction to the viscosity is obtained using the ring-kinetic equation, in terms of the correlations in the hydrodynamic modes of the linearised Enskog equation. It is shown that the Green-Kubo formula for the shear viscosity emerges from the two-body correlation function obtained from the ring-kinetic equation.

Supersonic shear imaging provides a reliable measurement of resting muscle shear elastic modulus

International Nuclear Information System (INIS)

Lacourpaille, Lilian; Hug, François; Bouillard, Killian; Nordez, Antoine; Hogrel, Jean-Yves

2012-01-01

The aim of the present study was to assess the reliability of shear elastic modulus measurements performed using supersonic shear imaging (SSI) in nine resting muscles (i.e. gastrocnemius medialis, tibialis anterior, vastus lateralis, rectus femoris, triceps brachii, biceps brachii, brachioradialis, adductor pollicis obliquus and abductor digiti minimi) of different architectures and typologies. Thirty healthy subjects were randomly assigned to the intra-session reliability (n = 20), inter-day reliability (n = 21) and the inter-observer reliability (n = 16) experiments. Muscle shear elastic modulus ranged from 2.99 (gastrocnemius medialis) to 4.50 kPa (adductor digiti minimi and tibialis anterior). On the whole, very good reliability was observed, with a coefficient of variation (CV) ranging from 4.6% to 8%, except for the inter-operator reliability of adductor pollicis obliquus (CV = 11.5%). The intraclass correlation coefficients were good (0.871 ± 0.045 for the intra-session reliability, 0.815 ± 0.065 for the inter-day reliability and 0.709 ± 0.141 for the inter-observer reliability). Both the reliability and the ease of use of SSI make it a potentially interesting technique that would be of benefit to fundamental, applied and clinical research projects that need an accurate assessment of muscle mechanical properties. (note)

Length-scales of Slab-induced Asthenospheric Deformation from Geodynamic Modeling, Mantle Deformation Fabric, and Synthetic Shear Wave Splitting

Science.gov (United States)

Jadamec, M. A.; MacDougall, J.; Fischer, K. M.

2017-12-01

The viscosity structure of the Earth's interior is critically important, because it places a first order constraint on plate motion and mantle flow rates. Geodynamic models using a composite viscosity based on experimentally derived flow laws for olivine aggregates show that lateral viscosity variations emerge in the upper mantle due to the subduction dynamics. However, the length-scale of this transition is still not well understood. Two-dimensional numerical models of subduction are presented that investigate the effect of initial slab dip, maximum yield stress (slab strength), and viscosity formulation (Newtonian versus composite) on the emergent lateral viscosity variations in the upper-mantle and magnitude of slab-driven mantle flow velocity. Significant viscosity reductions occur in regions of large flow velocity gradients due to the weakening effect of the dislocation creep deformation mechanism. The dynamic reductions in asthenospheric viscosity (less than 1018 Pa s) occur within approximately 500 km from driving force of the slab, with peak flow velocities occurring in models with a lower yield stress (weaker slab) and higher stress exponent. This leads to a sharper definition of the rheological base of the lithosphere and implies lateral variability in tractions along the base of the lithosphere. As the dislocation creep mechanism also leads to mantle deformation fabric, we then examine the spatial variation in the LPO development in the asthenosphere and calculate synthetic shear wave splitting. The models show that olivine LPO fabric in the asthenosphere generally increases in alignment strength with increased proximity to the slab, but can be transient and spatially variable on small length scales. The vertical flow fields surrounding the slab tip can produce shear-wave splitting variations with back-azimuth that deviate from the predictions of uniform trench-normal anisotropy, a result that bears on the interpretation of complexity in shear

The Viscosity of Organic Liquid Mixtures

Science.gov (United States)

Len, C. W.; Trusler, J. P. M.; Vesovic, V.; Wakeham, W. A.

2006-01-01

The paper reports measurements of the viscosity and density of two heavy hydrocarbon mixtures, Dutrex and Arab Light Flashed Distillate (ALFD), and of their mixtures with hydrogen. The measurements have been carried out with a vibrating-wire device over a range of temperatures from 399 to 547 K and at pressures up to 20 MPa. Measurements have also been carried out on systems in which hydrogen at different concentrations has been dissolved in the liquids. The measurements have an estimated uncertainty of ±5% for viscosity and ±2% for density and represent the first results on these prototypical heavy hydrocarbons. The results reveal that the addition of hydrogen reduces both the density and viscosity of the original hydrocarbon mixture at a particular temperature and pressure.

Application and Analysis of Measurement Model for Calibrating Spatial Shear Surface in Triaxial Test

Science.gov (United States)

Zhang, Zhihua; Qiu, Hongsheng; Zhang, Xiedong; Zhang, Hang

2017-12-01

Discrete element method has great advantages in simulating the contacts, fractures, large displacement and deformation between particles. In order to analyze the spatial distribution of the shear surface in the three-dimensional triaxial test, a measurement model is inserted in the numerical triaxial model which is generated by weighted average assembling method. Due to the non-visibility of internal shear surface in laboratory, it is largely insufficient to judge the trend of internal shear surface only based on the superficial cracks of sheared sample, therefore, the measurement model is introduced. The trend of the internal shear zone is analyzed according to the variations of porosity, coordination number and volumetric strain in each layer. It shows that as a case study on confining stress of 0.8 MPa, the spatial shear surface is calibrated with the results of the rotated particle distribution and the theoretical value with the specific characteristics of the increase of porosity, the decrease of coordination number, and the increase of volumetric strain, which represents the measurement model used in three-dimensional model is applicable.

Cosmic shear measurement with maximum likelihood and maximum a posteriori inference

Science.gov (United States)

Hall, Alex; Taylor, Andy

2017-06-01

We investigate the problem of noise bias in maximum likelihood and maximum a posteriori estimators for cosmic shear. We derive the leading and next-to-leading order biases and compute them in the context of galaxy ellipticity measurements, extending previous work on maximum likelihood inference for weak lensing. We show that a large part of the bias on these point estimators can be removed using information already contained in the likelihood when a galaxy model is specified, without the need for external calibration. We test these bias-corrected estimators on simulated galaxy images similar to those expected from planned space-based weak lensing surveys, with promising results. We find that the introduction of an intrinsic shape prior can help with mitigation of noise bias, such that the maximum a posteriori estimate can be made less biased than the maximum likelihood estimate. Second-order terms offer a check on the convergence of the estimators, but are largely subdominant. We show how biases propagate to shear estimates, demonstrating in our simple set-up that shear biases can be reduced by orders of magnitude and potentially to within the requirements of planned space-based surveys at mild signal-to-noise ratio. We find that second-order terms can exhibit significant cancellations at low signal-to-noise ratio when Gaussian noise is assumed, which has implications for inferring the performance of shear-measurement algorithms from simplified simulations. We discuss the viability of our point estimators as tools for lensing inference, arguing that they allow for the robust measurement of ellipticity and shear.

Viscosity bound violation in holographic solids and the viscoelastic response

Energy Technology Data Exchange (ETDEWEB)

Alberte, Lasma [Abdus Salam International Centre for Theoretical Physics (ICTP),Strada Costiera 11, 34151, Trieste (Italy); Baggioli, Matteo [Institut de Física d’Altes Energies (IFAE),The Barcelona Institute of Science and Technology (BIST),Campus UAB, 08193 Bellaterra, Barcelona (Spain); Department of Physics, Institute for Condensed Matter Theory, University of Illinois,1110 W. Green Street, Urbana, IL 61801 (United States); Pujolàs, Oriol [Institut de Física d’Altes Energies (IFAE),The Barcelona Institute of Science and Technology (BIST),Campus UAB, 08193 Bellaterra, Barcelona (Spain)

2016-07-14

We argue that the Kovtun-Son-Starinets (KSS) lower bound on the viscosity to entropy density ratio holds in fluid systems but is violated in solid materials with a non-zero shear elastic modulus. We construct explicit examples of this by applying the standard gauge/gravity duality methods to massive gravity and show that the KSS bound is clearly violated in black brane solutions whenever the massive gravity theories are of solid type. We argue that the physical reason for the bound violation relies on the viscoelastic nature of the mechanical response in these materials. We speculate on whether any real-world materials can violate the bound and discuss a possible generalization of the bound that involves the ratio of the shear elastic modulus to the pressure.

Viscosity bound violation in holographic solids and the viscoelastic response

International Nuclear Information System (INIS)

Alberte, Lasma; Baggioli, Matteo; Pujolàs, Oriol

2016-01-01

We argue that the Kovtun-Son-Starinets (KSS) lower bound on the viscosity to entropy density ratio holds in fluid systems but is violated in solid materials with a non-zero shear elastic modulus. We construct explicit examples of this by applying the standard gauge/gravity duality methods to massive gravity and show that the KSS bound is clearly violated in black brane solutions whenever the massive gravity theories are of solid type. We argue that the physical reason for the bound violation relies on the viscoelastic nature of the mechanical response in these materials. We speculate on whether any real-world materials can violate the bound and discuss a possible generalization of the bound that involves the ratio of the shear elastic modulus to the pressure.

Numerical Simulation of Neoclassical Currents, Parallel Viscosity, and Radial Current Balance in Tokamak Plasmas

International Nuclear Information System (INIS)

Kiviniemi, T.

2001-01-01

One of the principal problems en route to a fusion reactor is that of insufficient plasma confinement, which has lead to both theoretical and experimental research into transport processes in the parameter range relevant for fusion energy production. The neoclassical theory of tokamak transport is well-established unlike the theory of turbulence driven anomalous transport in which extensive progress has been made during last few years. So far, anomalous transport has been dominant in experiments, but transport may be reduced to the neoclassical level in advanced tokamak scenarios. This thesis reports a numerical study of neoclassical fluxes, parallel viscosity, and neoclassical radial current balance in tokamaks. Neoclassical parallel viscosity and particle fluxes are simulated over a wide range of collisionalities, using the fully kinetic five-dimensional neoclassical orbit-following Monte Carlo code ASCOT. The qualitative behavior of parallel viscosity derived in earlier analytic models is shown to be incorrect for high poloidal Mach numbers. This is because the poloidal dependence of density was neglected. However, in high Mach number regime, it is the convection and compression terms, rather than the parallel viscosity term, that are shown to dominate the momentum balance. For fluxes, a reasonable agreement between numerical and analytical results is found in the collisional parameter regime. Neoclassical particle fluxes are additionally studied in the banana regime using the three-dimensional Fokker-Planck code DEPORA, which solves the drift-kinetic equation with finite differencing. Limitations of the small inverse aspect ratio approximation adopted in the analytic theory are addressed. Assuming that the anomalous transport is ambipolar, the radial electric field and its shear at the tokamak plasma edge can be solved from the neoclassical radial current balance. This is performed both for JET and ASDEX Upgrade tokamaks using the ASCOT code. It is shown that

Disentangling the role of hydrodynamic and frictional forces in a shear-thickening suspension

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Cohen, Itai

2015-03-01

Who among us has not spent countless hours squeezing, rubbing, and smushing gooey substances like, tooth paste, silly putty, corn starch, and even bodily fluids between our fingers? If we could magnify our view and look deep within the substances we are handling what structures would we find? How, do these structures lead to the fascinating mechanical properties that we experience on the scale of our fingers. In this talk I will address the phenomenon of shear thickening in which the viscosity of a suspension increases with increasing shear rate. I will describe recent measurements we have made using a newly developed confocal rheoscope that, for the first time, experimentally visualize the hydrodynamically induced particle clusters. Such clusters have been implicated in continuous shear thickening. It remains controversial as to whether thickening in such suspensions also arises from frictional interactions between particles. The distinct contributions of frictional and hydrodynamic forces are typically difficult to measure independently using conventional techniques. Here, I will describe our approach for using both bulk rheometry techniques and our confocal rheoscope to disentangle their contributions to the total stress response.

Direct measurement of wall shear stress in a reattaching flow with a photonic sensor

International Nuclear Information System (INIS)

Ayaz, U K; Ioppolo, T; Ötügen, M V

2013-01-01

Wall shear stress measurements are carried out in a planar backward-facing step flow using a micro-optical sensor. The sensor is essentially a floating element system and measures the shear stress directly. The transduction method to measure the floating element deflection is based on the whispering gallery optical mode (WGM) shifts of a dielectric microsphere. This method is capable of measuring floating element displacements of the order of a nanometer. The floating element surface is circular with a diameter of ∼960 µm, which is part of a beam that is in contact with the dielectric microsphere. The sensor is calibrated for shear stress as well as pressure sensitivity yielding 7.3 pm Pa −1 and 0.0236 pm Pa −1 for shear stress and pressure sensitivity, respectively. Hence, the contribution by the wall pressure is less than two orders of magnitude smaller than that of shear stress. Measurements are made for a Reynolds number range of 2000–5000 extending to 18 step heights from the step face. The results are in good agreement with those of earlier reports. An analysis is also carried out to evaluate the performance of the WGM sensor including measurement sensitivity and bandwidth. (paper)

The effect of refining step on the changes in viscosity values of vegetable oils

International Nuclear Information System (INIS)

Ergonul, P.G.

2013-01-01

In this work, the viscosity values of chemically refined vegetable oils (sunflower, corn, soybean and rapeseed) and physically refined vegetable oils (olive and palm) were determined during refining processes. At this point of view, fatty acid compositions and viscosity values of oil samples were determined. The edible vegetable oils presented Newtonian behavior in shear rates at ranges 6.28-20.93 s/sup -1/. It was observed that palm oil is more viscous than the others. During physical refining, the effect of both oil type and refining steps were significantly important, whereas in chemical refining only the effect of oil type was found statistically important (p<0.01). It was observed that correlation among fatty acid compositions and viscosity values of the samples showed differences according to oil type. (author)

Normalization of flow-mediated dilation to shear stress area under the curve eliminates the impact of variable hyperemic stimulus.

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Padilla, Jaume; Johnson, Blair D; Newcomer, Sean C; Wilhite, Daniel P; Mickleborough, Timothy D; Fly, Alyce D; Mather, Kieren J; Wallace, Janet P

2008-09-04

Normalization of brachial artery flow-mediated dilation (FMD) to individual shear stress area under the curve (peak FMD:SSAUC ratio) has recently been proposed as an approach to control for the large inter-subject variability in reactive hyperemia-induced shear stress; however, the adoption of this approach among researchers has been slow. The present study was designed to further examine the efficacy of FMD normalization to shear stress in reducing measurement variability. Five different magnitudes of reactive hyperemia-induced shear stress were applied to 20 healthy, physically active young adults (25.3 +/- 0. 6 yrs; 10 men, 10 women) by manipulating forearm cuff occlusion duration: 1, 2, 3, 4, and 5 min, in a randomized order. A venous blood draw was performed for determination of baseline whole blood viscosity and hematocrit. The magnitude of occlusion-induced forearm ischemia was quantified by dual-wavelength near-infrared spectrometry (NIRS). Brachial artery diameters and velocities were obtained via high-resolution ultrasound. The SSAUC was individually calculated for the duration of time-to-peak dilation. One-way repeated measures ANOVA demonstrated distinct magnitudes of occlusion-induced ischemia (volume and peak), hyperemic shear stress, and peak FMD responses (all p index of endothelial function.

Weakly sheared active suspensions: hydrodynamics, stability, and rheology.

Science.gov (United States)

Cui, Zhenlu

2011-03-01

We present a kinetic model for flowing active suspensions and analyze the behavior of a suspension subjected to a weak steady shear. Asymptotic solutions are sought in Deborah number expansions. At the leading order, we explore the steady states and perform their stability analysis. We predict the rheology of active systems including an activity thickening or thinning behavior of the apparent viscosity and a negative apparent viscosity depending on the particle type, flow alignment, and the anchoring conditions, which can be tested on bacterial suspensions. We find remarkable dualities that show that flow-aligning rodlike contractile (extensile) particles are dynamically and rheologically equivalent to flow-aligning discoid extensile (contractile) particles for both tangential and homeotropic anchoring conditions. Another key prediction of this work is the role of the concentration of active suspensions in controlling the rheological behavior: the apparent viscosity may decrease with the increase of the concentration.

Shear thickening in suspensions: the lubricated-to-frictional contact scenario

Science.gov (United States)

Morris, Jeffrey

2017-11-01

Suspensions of solid particles in viscous liquids can vary from low-viscosity liquids to wet granular materials or soft solids depending on the solids loading and the forces acting between particles. When the particles are very concentrated, these mixtures are ''dense suspensions.'' Dense suspensions often exhibit shear thickening, an increase in apparent viscosity as the shear rate is increased. In its most extreme form, order of magnitude increases in viscosity over such a narrow range in shear rate occur that the term discontinuous shear thickening (DST) is applied. DST is particularly striking as it occurs in the relatively simple case of nearly hard spheres in a Newtonian liquid, and is found to take place for submicron particles in colloidal dispersions to much larger particle corn starch dispersions. We focus on simulations of a recently developed ``lubricated-to-frictional'' rheology in which the interplay of viscous lubrication, repulsive surface forces, and contact friction between particle surfaces provides a scenario to explain DST. Our simulation method brings together elements of the discrete-element method from granular flow with a simplified Stokesian Dynamics, and can rationalize not only the abrupt change in properties with imposed shear rate (or shear stress), but also the magnitude of the change. The large change in properties is associated with the breakdown of lubricating films between particles, with activation of Coulomb friction between particles. The rate dependence is caused by the shearing forces driving particles to contact, overwhelming conservative repulsive forces between surfaces; the repulsive forces are representative of colloidal stabilization by surface charge or steric effects, e.g. due to adsorbed polymer. The results of simulation are compared to developments by other groups, including a number of experimental studies and a theory incorporating the same basic elements as the simulation. The comparison to experiments of the

Increasing Accuracy of Tissue Shear Modulus Reconstruction Using Ultrasonic Strain Tensor Measurement

Science.gov (United States)

Sumi, C.

Previously, we developed three displacement vector measurement methods, i.e., the multidimensional cross-spectrum phase gradient method (MCSPGM), the multidimensional autocorrelation method (MAM), and the multidimensional Doppler method (MDM). To increase the accuracies and stabilities of lateral and elevational displacement measurements, we also developed spatially variant, displacement component-dependent regularization. In particular, the regularization of only the lateral/elevational displacements is advantageous for the lateral unmodulated case. The demonstrated measurements of the displacement vector distributions in experiments using an inhomogeneous shear modulus agar phantom confirm that displacement-component-dependent regularization enables more stable shear modulus reconstruction. In this report, we also review our developed lateral modulation methods that use Parabolic functions, Hanning windows, and Gaussian functions in the apodization function and the optimized apodization function that realizes the designed point spread function (PSF). The modulations significantly increase the accuracy of the strain tensor measurement and shear modulus reconstruction (demonstrated using an agar phantom).

Viscosidade extensional e em cisalhamento de suspensões acidificadas de amido de amaranto e caseinato de sódio Extensional and shear viscosity of acidified amaranth starch-sodium caseinate suspensions

Directory of Open Access Journals (Sweden)

Angela Maria Gozzo

2009-09-01

Full Text Available Foram avaliadas as viscosidades extensional e em cisalhamento de suspensões acidificadas de amido de amaranto-caseinato de sódio. Sistemas mistos de amido de amaranto-caseinato de sódio acidificados com glucona-delta-lactona (GDL foram estudados por ensaios reológicos em compressão biaxial e cisalhamento. Os efeitos da velocidade de acidificação (lenta e rápida e pH final (neutro e no ponto isoelétrico da caseína foram avaliados considerando as interações entre os biopolímeros e sua consequente influência nos parâmetros reológicos. Todas as amostras apresentaram comportamento pseudoplástico, no entanto, a adição de caseinato de sódio nas suspensões de amido, em pH neutro, promoveu um efeito negativo sobre a viscosidade aparente. Amostras acidificadas apresentaram um aumento na complexidade do sistema devido à formação da rede de amido e caseína, observando que a força necessária para o escoamento foi sempre maior para as amostras contendo concentrações maiores de caseinato. Isso mostra que a agregação e gelificação da proteína promovidas pela acidificação, impediram a microsseparação de fases. Esta rede foi mais forte em sistemas gelificados lentamente, devido à formação de uma rede de proteína mais organizada. Apesar da técnica de compressão biaxial imperfeita ser limitada para avaliação de determinados sistemas, neste estudo, mostrou ser um modo prático e eficiente de se mensurar o comportamento reológico.Extensional and shear viscosity of acidified amaranth starch-sodium caseinate suspensions were evaluated. Mixed systems of amaranth starch-sodium caseinate acidified with glucone-delta-lactone (GDL were studied using rheological measurements under biaxial compression and shear. The effects of the acidification rate (slow and fast and final pH (neutral and isoelectric point of casein were evaluated considering the interactions between biopolymers and their influence on the rheological parameters

Irradiated pepper and ginger detected by viscosity and starch measurements

International Nuclear Information System (INIS)

Wegmueler, F.; Meier, W.

1999-01-01

Starch and rheological measurements of alkaline suspensions of white pepper, black pepper and ginger are a useful tool to distinguish not irradiated samples from the gamma-treated spices (dose gtoreq 2 kGy). In addition it is shown that starch is not the material which determines the different rheological behaviour of the alkaline suspensions of the spices. The differences in the viscosity data are rather due to irradiation damages of polymers which are enriched in the cell wall material of the pepper grains and the roots of the ginger

A mathematical model for the movement of food bolus of varying viscosities through the esophagus

Science.gov (United States)

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 effects of size and period of administration of gold nanoparticles on rheological parameters of blood plasma of rats over a wide range of shear rates: In vivo

Directory of Open Access Journals (Sweden)

Abdelhalim Mohamed Anwar K

2011-10-01

Full Text Available Abstract Background Blood viscosity appears to be independent predictor of stroke, carotid intima-media thickening, atherosclerosis and most cardiovascular diseases. In an attempt to understand the toxicity and the potential threat of GNPs therapeutic and diagnostic use, an array of rheological parameters were performed to quantify the blood plasma response to different sizes and administration periods of GNPs over a wide range of shear rates. Methods Healthy, thirty male Wistar-Kyoto rats, 8-12 weeks old (approximately 250 g body weight were divided into control group (NG: n = 10, group 1 (G1A: intraperitoneal infusion of 10 nm GNPs for 3 days, n = 5 and G1B: intraperitoneal infusion of 10 nm GNPs for 7 days, n = 5, group 2 (G2A: intraperitoneal infusion of 50 nm GNPs for 3 days, n = 5 and G2B: intraperitoneal infusion of 50 nm GNPs for 7 days, n = 5. Dose of 100 μl of GNPs was administered to the animals via intraperitoneal injection. Blood samples of nearly 1 ml were obtained from each rat. Various rheological parameters such as torque, shear stress, shear rate, viscosity, plastic velocity, yield stress, consistency index (k and flow index (n were measured in the blood plasma of rats after the intraperitoneal administration of 10 and 50 nm GNP for 3 and 7 days using Brookfield LVDV-III Programmable rheometer. Results The relationship between shear stress and shear rate for control, G1A, G1B, G2A and G2B was linearly related. The plastic viscosity and the yield stress values for G1A, G1B, G2A and G2B significantly (p Conclusions At these particular shear rates, the estimated rheological parameters are not influenced by GNPs size and shape, number of NPs, surface area and administration period of GNPs. This study demonstrates that the highly decrease in blood plasma viscosity was accompanied with the smaller 10 nm GNPs compared with the 50 nm GNPs. The decrease in blood plasma viscosity induced with 10 and 50 nm GNPs may be attributed to

Interaction between a normal shock wave and a turbulent boundary layer at high transonic speeds. II - Wall shear stress

Science.gov (United States)

Liou, M. S.; Adamson, T. C., Jr.

1980-01-01

Asymptotic methods are used to calculate the shear stress at the wall for the interaction between a normal shock wave and a turbulent boundary layer on a flat plate. A mixing length model is used for the eddy viscosity. The shock wave is taken to be strong enough that the sonic line is deep in the boundary layer and the upstream influence is thus very small. It is shown that unlike the result found for laminar flow an asymptotic criterion for separation is not found; however, conditions for incipient separation are computed numerically using the derived solution for the shear stress at the wall. Results are compared with available experimental measurements.

Cosmic shear measurements with Dark Energy Survey Science Verification data

International Nuclear Information System (INIS)

Becker, M. R.

2016-01-01

Here, we present measurements of weak gravitational lensing cosmic shear two-point statistics using Dark Energy Survey Science Verification data. We demonstrate that our results are robust to the choice of shear measurement pipeline, either ngmix or im3shape, and robust to the choice of two-point statistic, including both real and Fourier-space statistics. Our results pass a suite of null tests including tests for B-mode contamination and direct tests for any dependence of the two-point functions on a set of 16 observing conditions and galaxy properties, such as seeing, airmass, galaxy color, galaxy magnitude, etc. We use a large suite of simulations to compute the covariance matrix of the cosmic shear measurements and assign statistical significance to our null tests. We find that our covariance matrix is consistent with the halo model prediction, indicating that it has the appropriate level of halo sample variance. We also compare the same jackknife procedure applied to the data and the simulations in order to search for additional sources of noise not captured by the simulations. We find no statistically significant extra sources of noise in the data. The overall detection significance with tomography for our highest source density catalog is 9.7σ. Cosmological constraints from the measurements in this work are presented in a companion paper

Effects of iodinated contrast media on common carotid and brachial artery blood flow and wall shear stress

International Nuclear Information System (INIS)

Irace, C.; Tamburini, S.; Bertucci, B.; Franceschi, M.S. de; Gnasso, A.

2006-01-01

The aim of our study was to evaluate the effect of the intravenous contrast media iomeprol on wall shear stress, blood flow and vascular parameters in the common carotid and brachial artery. Thirty outpatients undergoing thoracic or abdominal spiral CT scans were studied. The internal diameter and flow velocity of the common carotid and brachial artery were evaluated by ultrasound, and blood viscosity was measured before and after low osmolality iomeprol (Iomeron 350) injection. The wall shear stress, blood flow and pulsatility index were calculated. To test the differences between groups, the Wilcoxon rank test and Mann Whitney U test were applied. Blood viscosity decreased slightly, but significantly after contrast media (4.6±0.7 vs. 4.5±0.7 mPa.s, P=0.02). Contrarily, blood flow and wall shear stress did not change in the common carotid artery, but significantly decreased in the brachial artery (0.9±0.4 vs. 0.6±0.3 ml/s, P<0.0001, and 41.5±13.9 vs. 35.3±11.0 dynes/cm2, P<0.002, respectively), whereas the pulsatility index significantly increased in the brachial artery (5.0±3.3 vs. 7.5±5.3, P<0.001). Iomeprol injection causes blood flow and wall shear stress reduction of the brachial artery; the rise in the pulsatility index suggests an increase in peripheral vascular resistance. Further investigation is needed to evaluate whether these modifications can be clinically relevant. (orig.)

Soft-Matter Resistive Sensor for Measuring Shear and Pressure Stresses

Science.gov (United States)

Tepayotl-Ramirez, Daniel; Roberts, Peter; Majidi, Carmel

2013-03-01

Building on emerging paradigms in soft-matter electronics, we introduce liquid-phase electronic sensors that simultaneously measures elastic pressure and shear deformation. The sensors are com- posed of a sheet of elastomer that is embedded with fluidic channels containing eutectic Gallium- Indium (EGaIn), a metal alloy that is liquid at room temperature. Applying pressure or shear traction to the surface of the surrounding elastomer causes the elastomer to elastically deform and changes the geometry and electrical properties of the embedded liquid-phase circuit elements. We introduce analytic models that predict the electrical response of the sensor to prescribed surface tractions. These models are validated with both Finite Element Analysis (FEA) and experimental measurements.

Rheological Investigation on the Effect of Shear and Time Dependent Behavior of Waxy Crude Oil

Directory of Open Access Journals (Sweden)

Japper-Jaafar A.

2014-07-01

Full Text Available Rheological measurements are essential in transporting crude oil, especially for waxy crude oil. Several rheological measurements have been conducted to determine various rheological properties of waxy crude oil including the viscosity, yield strength, wax appearance temperature (WAT, wax disappearance temperature (WDT, storage modulus and loss modulus, amongst others, by using controlled stress rheometers. However, a procedure to determine the correct parameters for rheological measurements is still unavailable in the literature. The paper aims to investigate the effect of shear and time dependent behaviours of waxy crude oil during rheological measurements. It is expected that the preliminary work could lead toward a proper rheological measurement guideline for reliable rheological measurement of waxy crude oil.

Determination of the shear impedance of viscoelastic liquids using cylindrical piezoceramic resonators.

Science.gov (United States)

Kiełczyński, Piotr; Pajewski, Wincenty; Szalewski, Marek

2003-03-01

In this paper, a new method for determining the rheological parameters of viscoelastic liquids is presented. To this end, we used the perturbation method applied to shear vibrations of cylindrical piezoceramic resonators. The resonator was viscoelastically loaded on the outer cylindrical surface. Due to this loading, the resonant frequency and quality factor of the resonator changed. According to the perturbation method, the change in the complex resonant frequency deltaomega = deltaomega(re) + jdeltaomega(im) is directly proportional to the specific acoustic impedance for cylindrical waves Zc of a viscoelastic liquid surrounding the resonator, i.e., deltaomega is approximately equal to jZc, where j = (-1)1/2. Hence, the measurement of the real and imaginary parts of the complex resonant frequency deltaomega determines the real part, Rc, and imaginary part, Xc, of the complex acoustic impedance for cylindrical waves Zc of an investigated liquid. Furthermore, the specific impedance ZL for plane waves was related to the specific impedance Zc for cylindrical waves. Using theoretical formulas established and the results of the experiments performed, the shear storage modulus mu and the viscosity eta for various liquids (e.g., epoxy resins) were determined. Moreover, the authors derived for cylindrical resonators a formula that relates the shift in resonant frequency to the viscosity of the liquid. This formula is analogous to the Kanazawa-Gordon formula that was derived for planar resonators and Newtonian liquids.

Resistor capacitor, primitive variable solution of buoyant fluid flow within an enclosure with highly temperature dependent viscosity

Energy Technology Data Exchange (ETDEWEB)

Burns, S.P. [Texas Univ., Austin, TX (United States); Gianoulakis, S.E. [Sandia National Labs., Albuquerque, NM (United States)

1995-07-01

A numerical solution for buoyant natural convection within a square enclosure containing a fluid with highly temperature dependent viscosity is presented. Although the fluid properties employed do not represent any real fluid, the large variation in the fluid viscosity with temperature is characteristic of turbulent flow modeling with eddy-viscosity concepts. Results are obtained using a primitive variable formulation and the resistor method. The results presented include velocity, temperature and pressure distributions within the enclosure as well as shear stress and heat flux distributions along the enclosure walls. Three mesh refinements were employed and uncertainty values are suggested for the final mesh refinement. These solutions are part of a contributed benchmark solution set for the subject problem.

Determining a membrane's shear modulus, independent of its area-dilatation modulus, via capsule flow in a converging micro-capillary.

Science.gov (United States)

Dimitrakopoulos, P; Kuriakose, S

2015-04-14

Determination of the elastic properties of the membrane of artificial capsules is essential for the better design of the various devices that are utilized in their engineering and biomedical applications. However this task is complicated owing to the combined effects of the shear and area-dilatation moduli on the capsule deformation. Based on computational investigation, we propose a new methodology to determine a membrane's shear modulus, independent of its area-dilatation modulus, by flowing strain-hardening capsules in a converging micro-capillary of comparable size under Stokes flow conditions, and comparing the experimental measurements of the capsule elongation overshooting with computational data. The capsule prestress, if any, can also be determined with the same methodology. The elongation overshooting is practically independent of the viscosity ratio for low and moderate viscosity ratios, and thus a wide range of capsule fluids can be employed. Our proposed experimental device can be readily produced via glass fabrication while owing to the continuous flow in the micro-capillary, the characterization of a large number of artificial capsules is possible.

Green-Kubo relations for the viscosity of biaxial nematic liquid crystals

Science.gov (United States)

Sarman, Sten

1996-09-01

We derive Green-Kubo relations for the viscosities of a biaxial nematic liquid crystal. In this system there are seven shear viscosities, three twist viscosities, and three cross coupling coefficients between the antisymmetric strain rate and the symmetric traceless pressure tensor. According to the Onsager reciprocity relations these couplings are equal to the cross couplings between the symmetric traceless strain rate and the antisymmetric pressure. Our method is based on a comparison of the microscopic linear response generated by the SLLOD equations of motion for planar Couette flow (so named because of their close connection to the Doll's tensor Hamiltonian) and the macroscopic linear phenomenological relations between the pressure tensor and the strain rate. In order to obtain simple Green-Kubo relations we employ an equilibrium ensemble where the angular velocities of the directors are identically zero. This is achieved by adding constraint torques to the equations for the molecular angular accelerations. One finds that all the viscosity coefficients can be expressed as linear combinations of time correlation function integrals (TCFIs). This is much simpler compared to the expressions in the conventional canonical ensemble, where the viscosities are complicated rational functions of the TCFIs. The reason for this is, that in the constrained angular velocity ensemble, the thermodynamic forces are given external parameters whereas the thermodynamic fluxes are ensemble averages of phase functions. This is not the case in the canonical ensemble. The simplest way of obtaining numerical estimates of viscosity coefficients of a particular molecular model system is to evaluate these fluctuation relations by equilibrium molecular dynamics simulations.

Final rubbery state characterization using a hollow cylinder dynamic shear sample on DMA7

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Vilaiporn Luksameevanish

2004-09-01

Full Text Available Dynamic properties of raw natural rubber were examined using a hollow cylinder shaped samplesubjected to shear deformation on a laboratory Dynamic Mechanical Analyser. According to Cox-Merz’s study, dynamic complex viscosity obtained by this method showed a good agreement with shear flow viscosity measured by capillary rheometer. A master curve derived from the dynamic properties were then characterized. A crossing point of storage modulus (G’ and loss modulus (G’’ curves in the master curves was used to identify the final rubbery state, which indicated the transition of rubbery state and molten state. The position of this point depends on quantities and types of reinforcing or non-reinforcing fillers. The final rubbery state was shifted to higher frequency or lower temperature. It was found that the final rubbery state of CaCO3-filled rubber compounds was shifted to higher frequency or lower temperature by approximately 4 decades, while the translation of carbon black-filled rubber compounds was lower than unfilled rubber by about 1 decade. This phenomenon can be used to explain rubber elasticity, i.e. a decreasing of die swell of CaCO3 filled compounds at any high processing temperature. On the other hand, high magnitude of die swell for carbon black filled compound was still obtained.

Effect of viscosity on seismic response of waste storage tanks

International Nuclear Information System (INIS)

Tang, Yu; Uras, R.A.; Chang, Yao-Wen.

1992-06-01

The dynamic response of liquid-storage tanks subjected to harmonic excitations and earthquake ground motions has been studied. A rigid tank of negligible mass, rigidly supported at the base having a diameter of 50 ft. and fluid height of 20.4 ft. was used in the computer analysis. The liquid is assumed to have a density of 1.5 g/ml. Viscosity values, μ = 60, 200, 100, and 10,000 cP, were used in the numerical analyses to study the effects of viscosity on sloshing wave height, impulsive and convective pressure on the tank wall, base shear and base moments. Harmonic excitations as well as earthquake ground motions were used as input motions. The harmonic excitations used in the analyses covers a wide range of frequencies, including both the resonant and non-resonant frequencies. Two earthquake motions were used. One matches the Newmark-Hall median response spectrum and is anchored at 0.24 g for a rock site with a damping of 2% and a time duration of 10 s. The other is the 1978 Tabas earthquake which had a peak ZPA of 0.81 g and a time duration of 29 s. A small tank, about 1/15 the size of the typical waste storage tank, was used in the harmonic excitation study to investigate the effect of viscosity on the response of liquid-storage tanks and how the viscosity effect is affected by the size of the storage tank. The results of this study show that for the typical waste storage tank subjected to earthquake motions, the effect of viscosity on sloshing wave height and impulsive and convective pressures is very small and can be neglected. For viscosity effect to become noticeable in the response of the typical waste storage tank, the waste viscosity must be greater than 10,000 cP. This value is far greater than the estimated viscosity value of the high level wastes, which may range from 60 to 200 cP for some tanks

Formation of structural steady states in lamellar/sponge phase-separating fluids under shear flow

Science.gov (United States)

Panizza, P.; Courbin, L.; Cristobal, G.; Rouch, J.; Narayanan, T.

2003-05-01

We investigate the effect of shear flow on a lamellar-sponge phase-separating fluid when subjected to shear flow. We show the existence of two different steady states (droplets and ribbons structures) whose nature does not depend on the way to reach the two-phase unstable region of the phase diagram (temperature quench or stirring). The transition between ribbons and droplets is shear thickening and its nature strongly depends on what dynamical variable is imposed. If the stress is fixed, flow visualization shows the existence of shear bands at the transition, characteristic of coexistence in the cell between ribbons and droplets. In this shear-banding region, the viscosity oscillates. When the shear rate is fixed, no shear bands are observed. Instead, the transition exhibits a hysteretic behavior leading to a structural bi-stability of the phase-separating fluid under flow.

Measuring Local Strain Rates In Ductile Shear Zones: A New Approach From Deformed Syntectonic Dykes

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Sassier, C.; Leloup, P.; Rubatto, D.; Galland, O.; Yue, Y.; Ding, L.

2006-12-01

At the Earth surface, deformation is mostly localized in fault zones in between tectonic plates. In the upper crust, the deformation is brittle and the faults are narrow and produce earthquakes. In contrast, deformation in the lower ductile crust results in larger shear zones. While it is relatively easy to measure in situ deformation rates at the surface using for example GPS data, it is more difficult to determinate in situ values of strain rate in the ductile crust. Such strain rates can only be estimated in paleo-shear zones. Various methods have been used to assess paleo-strain rates in paleo-shear zones. For instance, cooling and/or decompression rates associated with assumptions on geothermic gradients and shear zone geometry can lead to such estimates. Another way to estimate strain rates is the integration of paleo-stress measurements in a power flow law. But these methods are indirect and imply strong assumptions. Dating of helicitic garnets or syntectonic fibres are more direct estimates. However these last techniques have been only applied in zones of low deformation and not in major shear zones. We propose a new direct method to measure local strain rates in major ductile shear zones from syntectonic dykes by coupling quantification of deformation and geochronology. We test our method in a major shear zone in a well constrained tectonic setting: the Ailao-Shan - Red River Shear Zone (ASRRsz) located in SE Asia. For this 10 km wide shear zone, large-scale fault rates, determined in three independent ways, imply strain rates between 1.17×10^{-13 s-1 and 1.52×10^{-13 s-1 between 35 and 16 Ma. Our study focused on one outcrop where different generations of syntectonic dykes are observed. First, we quantified the minimum shear strain γ for each dyke using several methods: (1) by measuring the stretching of dykes with a surface restoration method (2) by measuring the final angle of the dykes with respect to the shear direction and (3) by combining the two

Measurement and study of density, surface tension, and viscosity of quaternary ammonium-based ionic liquids ([N222(n)]Tf2N)

International Nuclear Information System (INIS)

Ghatee, Mohammad Hadi; Bahrami, Maryam; Khanjari, Neda

2013-01-01

Highlights: • Characterization of high purity synthesized alkyl quaternary ammonium ionic liquids. • Measurement of temperature dependent surface tension, density, viscosity and critical point. • Systematic increase of surface energy and surface entropy having plateau at high chain length. • Accurate application of VFT and fluidity equations to temperature dependent viscosities. • Particular variation of fluidity exponent with a plateau at high alkyl chain length. -- Abstract: In this work five quaternary ammonium-based ionic liquids with bis(trifluoromethylsulfonyl)imide anion were synthesized and their density, viscosity and surface tensions were measured in the temperature range (298 to 373) K. Surface tensions were measured by capillary rise method using a homemade capillary apparatus, in which the liquid/vapor can be brought into equilibrium practically. Measurements of viscosities and surface tensions were performed under water–vapor free atmosphere. The surface tension of quaternary ammonium-based ILs decreases as the alkyl chain length increases. Also surface energy and surface entropy are found as increasing functions of alkyl chain length with a plateau at high lengths in the surface. The viscosities measured by capillary viscometer fit in VFT equation, indication of non-Arrhenius ionic liquids. Viscosities are also fitted quite accurately in the relation we have developed recently as the fluidity equation with the characteristics exponent ϕ. Values of ϕ for ionic liquids are close to one another and tend to the limiting value, almost 0.328, asymptotically as the alkyl chain length increases. The critical temperatures predicted via the temperature dependent surface tensions decrease with increasing alkyl chain length of the cation. The trend of predicted critical temperature of these ionic liquids conforms to those of imidazolium-based ILs

Hydrodynamic characterization and molecular weight estimation of ultrasonically sheared DNA

International Nuclear Information System (INIS)

Casal, J. I.; Garces, F.; Garcia-Sacristan, A.

1981-01-01

The sedimentation coefficients and intrinsic viscosities of ultrasonically sheared calf thymus DNA have been determined. The molecular weight estimation according to this parameters have been compared with the ones obtained from the electrophoretic migration rates based on the calibration proposed using the known molecular weight restriction fragments of X-ENA. (Author) 35 refs

Hydrodynamic caracterization and molecular weight stimation of ultrasonically sheared DNA

International Nuclear Information System (INIS)

Garces, F.; Casal, J.I.; Garcia, A.

1981-01-01

The sedimentation coefficients and intrinsec viscosities of ultrasonically sheared calf thymus DNA have been determined. The molecular weight stimation according to this parameters have been compared with the ones obtained from the electrophoretic migration rates based on the calibration proposed using the known molecular weight restriction fragments of lambds-DNA. (author) [es

Swimming efficiency in a shear-thinning fluid

Science.gov (United States)

Nganguia, Herve; Pietrzyk, Kyle; Pak, On Shun

2017-12-01

Micro-organisms expend energy moving through complex media. While propulsion speed is an important property of locomotion, efficiency is another factor that may determine the swimming gait adopted by a micro-organism in order to locomote in an energetically favorable manner. The efficiency of swimming in a Newtonian fluid is well characterized for different biological and artificial swimmers. However, these swimmers often encounter biological fluids displaying shear-thinning viscosities. Little is known about how this nonlinear rheology influences the efficiency of locomotion. Does the shear-thinning rheology render swimming more efficient or less? How does the swimming efficiency depend on the propulsion mechanism of a swimmer and rheological properties of the surrounding shear-thinning fluid? In this work, we address these fundamental questions on the efficiency of locomotion in a shear-thinning fluid by considering the squirmer model as a general locomotion model to represent different types of swimmers. Our analysis reveals how the choice of surface velocity distribution on a squirmer may reduce or enhance the swimming efficiency. We determine optimal shear rates at which the swimming efficiency can be substantially enhanced compared with the Newtonian case. The nontrivial variations of swimming efficiency prompt questions on how micro-organisms may tune their swimming gaits to exploit the shear-thinning rheology. The findings also provide insights into how artificial swimmers should be designed to move through complex media efficiently.

Coherent Rayleigh-Brillouin scattering measurements of bulk viscosity of polar and nonpolar gases, and kinetic theory

NARCIS (Netherlands)

Meijer, A.S.; Wijn, de A.S.; Peters, M.F.E.; Dam, N.J.; Water, van de W.

2010-01-01

We investigate coherent Rayleigh–Brillouin spectroscopy as an efficient process to measure the bulk viscosity of gases at gigahertz frequencies. Scattered spectral distributions are measured using a Fizeau spectrometer. We discuss the statistical error due to the fluctuating mode structure of the