H. J. M. Hanley

Non‐Newtonian phenomena in simple fluids

Almost a hundred years ago, Osborne Reynolds carried out a simple experiment. He filled a leather bag with marbles, topped it with water and then twisted it, thereby inducing a shear. The water level drops because the close packing of the marbles is disrupted as layers of marbles slide over each other during the twisting motion; as a result the marbles are further apart on average, creating space that the water has to fill.

A thermodynamics for a system under shear

A thermodynamics is introduced for fluids subjected to a constant shear. The theory is based primarily on the results of computer simulations using the technique of homogeneous shear nonequilibrium molecular dynamics applied to a system of 108 Lennard‐Jones particles. It is supported qualitatively by the results of several authors for other systems. The shear rate γ enters explicitly into the description of the fluid: the equation of state is p = p(V,T,γ) and thermodynamic equation is dE = TdS −pdV+ζdγ, where ζ is a state function. Using the relations found previously to be valid for a wide range of γ: p = p0+p1γ3/2 and E = E0+E1γ3/2, the thermodynamics can be checked numerically for consistency and several consequences, such as stability criteria criteria, can be verified. The criteria indicate that phase changes are influenced by the shear rate when the system is subjected to the shear.

A correlation of the viscosity and thermal conductivity data of gaseous and liquid propane

Data for the viscosity and thermal conductivity coefficient of gaseous and liquid ethylene have been evaluated and represented by an empirical function, developed in previous work. Tables of values are presented for the range 110–500 K for pressures to 50 MPa (≊500 atm). Both the viscosity and thermal conductivity coefficients are estimated to have uncertainties of about ±5% increasing to 10% in the dense liquid. It is stressed that the data base could be improved. As in our work with other fluids, the anomalous contribution to the thermal conductivity in the vicinity of the critical point is included.

Liquid structure under shear: comparison between computer simulations and colloidal suspensions

Simulated scattered light intensity plots are calculated for a soft sphere inverse‐12 system subjected to a shear and are compared to experimental plots for a colloidal suspension under approximately equivalent conditions. The simulated plots were obtained by a Fourier transform of the radial distribution function. The two sets show points of striking similarity: The Debye–Scherrer rings become elliptical when both systems are subjected to the shear, and the light intensity around the rings is a function of polar angle. An interesting feature is the degree to which the experimental plots display non‐Newtonian characteristics of the suspension. Overall, the work is a direct comparison of the results of a computer simulation with real experimental data. Suggestions for future work are given.

The viscosity and thermal conductivity coefficients for dense gaseous and liquid methane

Data for the viscosity and thermal conductivity coefficients of dense gaseous and liquid methane have been evaluated. Selected data were fitted to a function derived in our previous work and tables of values were generated for temperatures from 95 to 500 K and for pressures up to 50 MPa (∠500 atm). The uncertainties of the tabular values are estimated to be approximately 3% and 5% for the viscosity and thermal conductivity coefficients, respectively. The contribution for the thermal conductivity enhancement in the critical region is included in the tables. Care has been taken to ensure that the calculated values are consistent with reliable equation‐of‐state data and also with dilute gas transport coefficients determined previously.

A thermodynamics of steady homogeneous shear flow

Abstract Simulation data from model systems subjected to a shear can be described consistently by a thermodynamic formalism that includes the pressure and energy dependence on the strain rate. Stability criteria are examined for a system of soft spheres.

Shearing apparatus for neutron scattering studies on fluids: Preliminary results for colloidal suspensions

A Couette-type concentric cylinder apparatus to investigate liquids at equilibrium and under shear has been constructed and tested. The apparatus is designed for a neutron facility and is optimized as a general purpose adjunct to the small-angle neutron scattering (SANS) equipment. It is versatile and rugged; a wide range of shear rates and operating temperatures can be covered; and controls are fully automated. Test results with sheared colloidal suspensions of 91-nm polystyrene spheres are presented. Evidence of shear-induced structure changes is clear.

Selection of the intermolecular potential. Part 2.—From data of state and transport properties taken in pairs

A method previously developed to evaluate quantitatively the relationship between intermolecular potential functions and individual macroscopic properties is extended to the simultaneous fit of all possible pair combinations of these properties. As before the relationship between function families available has been clarified. New results from this investigation give important information1on the possible simultaneous fit of a simple function to more than one property. The function families studied were the m-6, Kihara, exp-6 and Morse functions. A reduced temperature range was found over which the simultaneous fit to pairs of properties is insensitive to the potential function. When a transport property is involved, this range is given by 2.0 < T*12-6 < 5.0, while if only equilibrium properties are involved, this range becomes 2.0 < T*12-6 < 10.0. Quantitative limits are given for the experimental error which can be tolerated without masking the sensitivity to the potential function outside these ranges.

Stokes-Maxwell relations for the distorted fluid microstructure☆

Abstract Relationships between the coefficients of the expansion of the pair correlation function for a fluid subjected to a shear are derived from a model kinetic equation. They equate a relaxation time with the viscosity and shear modulus of the fluid. Nonlinear phenomena are considered. The results are tested using nonequilibrium molecular dynamic simulation data for a soft sphere system close to freezing. Agreement between the theory and the simulations is satisfactory.

Rayleigh scattering from a methane–ethane mixture

The Rayleigh linewidth of a methane (71.07%)–ethane mixture was measured by dynamic light scattering near the plait point. Results are reported for the concentration diffusivity and (preliminary only) for the thermal diffusivity. It was found that a large background contribution is present in the concentration diffusivity, in agreement with theoretical predictions. The thermal diffusivity is compared to a one‐fluid model introduced previously. A critical temperature of 236.36±0.03 K and a critical pressure of 6.66±0.02 MPa was determined for the mixture.