Viscosity of liquid Al–Co alloys with a cobalt content up to 15 at %

By means of the torsional vibrations method, the temperature dependences (from the liquidus up to 1200°C) of the kinematic viscosity of liquid aluminum and Al–Co melts with a cobalt content up to 15 at % were obtained. For all the liquid alloys investigated, the temperature dependences of the viscosity obtained in the heating and cooling regimes coincide. The temperature dependences were approximated by the Arrhenius equation. For liquid aluminum and melts with a cobalt content below 1.4 at % inclusive, a viscosity polytherm deviation from the Arrhenius dependence was discovered. The viscosity dependences on the concentration at a fixed temperature and the activation energy of the viscous flow were plotted. An increase in the cobalt content in the melt results in an increase in the viscosity and the activation energy of the viscous flow values.     

Predicting the viscosity of liquid refrigerant blends: comparison with experimental data

A method is presented for predicting the viscosity of liquid refrigerant mixtures. The method has no adjustable parameters and, in essence, relies upon the knowledge of the viscosity of the pure components to predict the viscosity of a mixture by means of kinetic theory and rigid-sphere formalism. The predictions have been compared with the available experimental data for a number of refrigerant mixtures. Based on this comparison and previous studies, the accuracy of the proposed method is assessed to be of the order of ±7%.     

基于人工神经网络的乐甫波液体密度粘度并行检测研究

乐甫波器件负载液体时,液体的密度和粘度相互耦合,难以通过乐甫波器件直接实现其并行检测。基于上述背景,建立了基底与薄膜同时采用压电材料的双压电结构乐甫波器件液体传感理论模型,提出了基于人工神经网络的乐甫波液体密度粘度并行检测方法,以理论模型计算出的数据作为人工神经网络的训练数据,采用乐甫波的波速和衰减来并行预测液体密度和粘度,预测结果与理论仿真的对比表明了该方法的有效性。     

Development of Laser-Induced Capillary Wave Method for Viscosity Measurement Using Pulsed Carbon Dioxide Laser

A new experimental apparatus, based on the laser-induced capillary wave method involving the use of a pulsed carbon dioxide laser (wavelength 10.6 m, pulse width 50 ns, power 65 mJ) as a heating source has been developed. Since the present technique is applicable to a wide range of viscosity, this method is applicable to the process in which the viscosity drastically changes within a short period of time. In this method, interfering laser beams heat a liquid surface and generate a capillary wave (the wavelength can be adjusted from 20 to 200 m) caused by a spatially sinusoidal temperature distribution. The temporal behavior of the capillary wave is detected by a diffracted probe beam (He–Ne laser, 15 mW) at the heated area. The dynamics of the capillary wave provide information regarding thermophysical properties such as viscosity and surface tension. In the present study, several liquid samples spanning the viscosity range from 0.33 to 7080 MPa·s (e.g., acetone, toluene, 1-hexanol, ethylene glycol, JS1000, and JS14000) were investigated at room temperature. The detected signals for several liquid samples exhibiting a wide range of viscosity agree well with theoretical calculations, taking into account the influence of the distribution of surface tension.     

EFFECTS OF LIQUID VISCOSITY ON RHEOLOGY OF CONCENTRATED SUSPENSIONS

ABSTRACT

This paper presents the experimental results on the effects of liquid viscosity on the rheology of concentrated suspensions of solid particles in Newtonian liquids. Specifically, the relative viscosity of a pseudoplastic suspension decreases as the viscosity of the suspending liquid increases, indicating excess energy dissipation in a less viscous liquid. In contrast, the relative viscosity of a Newtonian suspension is only slightly affected by the liquid viscosity. It is in excellent agreement with the value predicted from the rigid sphere model which neglects nonhydrodynamic interactions, and assumes zero particle-to-liquid relative velocity. The flow behavior indices of both concentrated suspensions are independent of the liquid viscosity.     

Shear viscosity coefficients of compressed gaseous and liquid carbon dioxide at temperatures between 220 and 320 K and at pressures to 30 MPa

The shear viscosity coefficients of compressed gaseous and liquid carbon dioxide hav been measured with the torsional piezoelectric crystal method at temperatures between 220 and 320 K and at pressures to 30 MPa. The dependencies of the viscosity on pressure, density, and temperature and the dependencies of the fluidity (inverse viscosity) on molar volume and temperature have been examined. The measurements on the compressed liquid were correlated with a modified Hildebrand equation.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Generalization of data on the thermophysical properties of petroleum products. Viscosity

We describe the investigation and generalization of data on the viscosity of fractions of Romashkin petroleum. We develop a method for calculating the viscosity of petroleum products in the liquid phase.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 3, pp. 417–422, March, 1982.     

Rheology and flow-induced liquid crystal phase transitions in thermotropic polyethers

This work investigates the interdependence of the phase behaviour, viscosity, temperature, molecular weight and shear rates of thermotropic liquid crystalline polyethers. The viscosity of the isotropic and nematic phases are quantitatively compared; a positive variation in viscosity with respect to temperature is found, with the isotropic viscosity being about an order of magnitude higher than the liquid crystalline viscosity. The dependence of viscosity upon molecular weight of well defined fractions is investigated in both the liquid-crystal and isotropic phases. In the liquid crystalline state the viscosity scales with M ^3.5–5. Variations in the viscosity due to temperature changes affect the isotropic phase more than the liquid crystal phase. No evidence for a negative first normal stress difference is seen. Finally, it is shown how the phase diagram of the material can be altered by shearing the material in the isotropic phase. This is evident by the onset of a shear thinning region at temperatures slightly above T _i, which can be attributed to the formation of shear induced liquid crystallinity.     

Viscosity measurement using drop coalescence in microgravity

We present in here validation studies of a new method for application in microgravity environment which measures the viscosity of highly viscous undercooled liquids using drop coalescence. The method has the advantage of avoiding heterogeneous nucleation at container walls caused by crystallization of undercooled liquids during processing. Homogeneous nucleation can also be avoided due to the rapidity of the measurement using this method. The technique relies on measurements from experiments conducted in near zero gravity environment as well as highly accurate analytical formulation for the coalescence process. The viscosity of the liquid is determined by allowing the computed free surface shape relaxation time to be adjusted in response to the measured free surface velocity for two coalescing drops. Results are presented from two sets of validation experiments for the method which were conducted on board aircraft flying parabolic trajectories. In these tests the viscosity of a highly viscous liquid, namely glycerin, was determined at different temperatures using the drop coalescence method described in here. The experiments measured the free surface velocity of two glycerin drops coalescing under the action of surface tension alone in low gravity environment using high speed photography. The liquid viscosity was determined by adjusting the computed free surface velocity values to the measured experimental data. The results of these experiments were found to agree reasonably well with the known viscosity for the test liquid used.     

Simulating sedimentation of liquid drops

This work was carried out to investigate the effect of fluid properties on the flow pattern and on the sedimentation velocity of an axisymmetric steady flow of a Newtonian fluid past a liquid drop in an unbounded region. The governing equations of motion were solved by the finite element method. The results show that the flow pattern of a liquid drop depends strongly both on the Reynolds number and on the ratio of the viscosity between the drop and the surrounding flowing fluids. The viscosity ratio in the range 0.02<μ^*<50 has appreciable effect on the drag coefficient. Finally, a correlation for the sedimentation velocity is presented. Copyright © 2004 John Wiley & Sons, Ltd.     

Propagation of Uncertainty in Establishing the Viscosity Scale

The viscosity scale is established by step up method, in which several master viscometers and standard liquids are used. Starting point is the distilled water. The basic measurand is the efflux time. Uncertainty in the determination of viscometer constant of a viscometer or the kinematic viscosity of standard liquid at a particular step is carried forward for subsequent steps. The expressions for uncertainty for viscometer constant of the viscometer and kinematic viscosity of the liquid in nth step have been derived. Various applicable corrections and their contribution to uncertainty have been discussed.     

A Comparison of Surface Tension,Viscosity, and Density of Sn and Sn–Ag Alloys Using Different Measurement Techniques

This work is aimed at comparing several methods for the measurement of physical properties for molten Sn and Sn–Ag alloys, namely, surface tension, density, and viscosity. The method used for viscosity in this work is the modified capillary method. For surface tension and density, the data used for comparison were previously measured using the maximum bubble pressure method and the dilatometer technique, respectively, for four Sn–Ag alloys having (3.8, 32, 55, and 68) at% Ag. The results are compared with those obtained using a new method based on a fluid draining from a crucible under the influence of gravity, designated the Roach–Henein (RH) method. This new method enables the determination of these three physical properties in one set of measurements. Liquid Sn was used as well as two liquid Sn–Ag alloys having (3.8 and 34.6) at% Ag with the RH method. It was determined that the RH method may be used to simultaneously obtain surface tension, viscosity, and density and that the errors associated with these measurements were similar to those obtained using traditional and separate techniques. Comparisons of the measured viscosity and surface tension to those predicted using thermodynamic models will also be presented. Finally a comparison of mixing model predictions with the experimentally measured alloy surface tension and viscosity is also presented.     

Effects of polymer viscosity on the polymerization switching and electro-optical properties of unaligned liquid crystal/UV curable polymer composites

Polymer dispersed ferroelectric liquid crystal composite films consisting of varying polymer viscosities were prepared by polymerization induced phase separation (PIPS) technique. It was found that polymer viscosity influences the polarization switching and optical responses. A polymer dispersed ferroelectric liquid crystal film of low polymer viscosity shows faster switching, however a higher optical transmission at ~ 70% was observed in a higher polymer viscosity film.     

An acoustic study of the relaxation properties of ZhK-1282 nematic liquid crystals in the vicinity of the nematic-isotropic phase transition

The viscous and elastic properties of a ZhK-1282 nematic liquid crystal (NLC) were studied in a temperature interval from 290 to 360 K by method of ultrasonic spectroscopy in the 3–63 MHz frequency range. The temperature dependences of the NLC density and shear viscosity are presented. The results of measurements of the velocity and attenuation of ultrasound and the shear viscosity were used to calculate the volume viscosity coefficient, the moduli of dilatation and isothermal compressibility, the relaxation times of the elastic and viscous properties, and the corresponding critical characteristics of the given NLC.     

Viscosity of liquid toluene in the temperature range 25–75°C

New accurate experimental data are presented for the viscosity of liquid toluene. The viscosity was measured relative to the viscosity of liquid water with the aid of an Ubbelohde capillary viscometer. The data cover a temperature range from approximately 25 to 75°C and are represented with high precision by an Arrhenius equation     

Frequency-Dependent Elongational Viscosity by Nonequilibrium Molecular Dynamics

The elongational viscosity of a liquid describes the response of the liquid to simultaneous stretching and compression in various directions, subject to the restriction that the trace of the rate of the strain tensor is zero (or the density is constant). Despite the growing popularity and usefulness of nonequilibrium molecular dynamics methods in studies of the shear viscosity of simple and complex fluids, the elongational viscosity remains a relatively neglected property in computer simulation studies. This stems from some significant technical difficulties that arise when standard methods such as the constant strain rate SLLOD algorithm are applied to elongational flow. For example, if planar elongational flow with a constant elongation rate is applied in a computer simulation with periodic boundary conditions, the box size in the contracting direction quickly becomes smaller than twice the range of the potential, violating the minimum image convention. The time at which this occurs may be less than the time required for the system to reach a steady state, making it impossible to compute the steady-state elongational viscosity. This difficulty can be avoided by applying an oscillating elongational strain rate to the liquid, and computing frequency dependent elements of the stress tensor, which can then be extrapolated to zero frequency to evaluate the steady-state elongational viscosity. We have used this method to compute the elongational viscosity of a simple atomic liquid and discuss its possible application to a model polymeric liquid.     

The examination of water potentials by simulating viscosity

The shear viscosity of liquid water is simulated by molecular-dynamics (MD) method with a variety of nonpolarizable potentials (SPC, MCY, TIPS2 and TIP4P). By comparisons with experimental data, it shows that Stokes–Einstein relation can be used to calculate the viscosity of water. The calculated viscosity is lower than the experimental value at these temperatures bellow 293 K, but it is reasonably agreement with experimental values at temperatures higher than 313 K. The viscous activation energy for the different potential models is also calculated, the results indicate that the MCY potential is in better agreement with the experimental values than the others.     

The viscosity of liquid R134a

The paper reports new measurements of the viscosity of liquid R134a over the temperature range 235 to 343 K and pressures up to 50 MPa. The measurements have been carried out in a vibrating-wire viscometer calibrated with respect to the viscosity of several liquid hydrocarbons. It is estimated that the uncertainty in the viscosity data reported is ±0.6%. The data therefore have a lower uncertainty than that of earlier measurements of the viscosity of this environmentally acceptable regrigerant. The viscosity data have been represented as a function of density by means of a formulation based upon the rigid, hard-sphere theory of dense fluids with a maximum deviation of ±0.3%. This representation allows the present body of experimental data to be extended to regions of thermodynamic state not covered by the measurements.     

Surface Oscillations of an Electromagnetically Levitated Droplet

The natural oscillation frequency of freely suspended liquid droplets can be related to the surface tension of the material, and the decay of oscillations to the liquid viscosity. However, the fluid flow inside the droplet must be laminar to measure viscosity with existing correlations; otherwise the damping of the oscillations is dominated by turbulent dissipation. Because no experimental method has yet been developed to visualize flow in electromagnetically levitated oscillating metal droplets, mathematical modeling can assist in predicting whether or not turbulence occurs, and under what processing conditions. In this paper, three mathematical models of the flow: (1) assuming laminar conditions, (2) using the k−ɛ turbulence model, and (3) using the RNG turbulence model, respectively, are compared and contrasted to determine the physical characteristics of the flow. It is concluded that the RNG model is the best suited for describing this problem when the interior flow is turbulent. The goal of the presented work was to characterize internal flow in an oscillating droplet of liquid metal, and to verify the accuracy of the characterization by comparing calculated surface tension and viscosity values to available experimental results.     

Volumetric meter error due to changes in the viscosity of the measured liquid

Conclusions The volumetric meters' reading error due to variations in the viscosity of the measured liquid and the boundary of its variations can be determined by the above method based on the meter test results. This error is insignificant for liquids whose viscosity exceeds 10^–4 m²/sec.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 22–24, November, 1968.