Herschel–Bulkley fluid

About: Herschel–Bulkley fluid is a research topic. Over the lifetime, 1946 publications have been published within this topic receiving 49318 citations.

On the thermodynamic properties of the Lennard-Jones fluid

Abstract: An analytical scheme for the evaluation of the compressibility factor of a simple fluid is presented. It is based on the clasical perturbation theory and on a recent (analytical) approximation for the radial distribution function of the hard-sphere fluid. The scheme, which provides, in the case of the Lennard-Jones fluid, explicit expressions for both structural and thermodynamic quantities in a closed form, requires the hard-sphere fluid equation of state as the sole input. Using the Carnahan–Starling equation of state for the hard-sphere reference fluid, the prediction of the critical point as well as the behavior of the pressure of the Lennard-Jones fluid are an improvement in relation to previous work and compare rather well with recent numerical simulations. The same applies to the radial distribution function computed with the present scheme and the Weeks–Chandler–Andersen approach. From a knowledge of the freezing and melting transitions in the hard-sphere system, the liquid and solid branches of the reduced temperature vs. reduced density curve at coexistence for the Lennard-Jones fluid are simply obtained.

Fully-Developed Circular-Pipe Flow of a Non-Newtonian Pseudoplastic Fluid

Abstract: A fully-developed flow of a non-Newtonian pseudoplastic fluid through a circular pipe has been studied using a four-parameter model, as an example, for the shear-rate dependent apparent viscosity. The model used in this investigation is a modification of the two-parameter Ostwald-de Waele power law [1], which correctly represents the lower and upper regions of Newtonian behavior characteristic of pseudoplastic polymer melts and solutions. Since there has only one set complete experimental data available for the shear-rate dependent viscosity, we use them to show that a perfect match can be achieved between the modified power-law viscosity model and the experimental data. Such a perfect match is required for an accurate prediction of the flow behavior in internal flow problems.

Approximate constitutive equations for slow flow of rigid plastic viscoelastic fluids

Abstract: A theory of slow flow of rigid plastic viscoelastic fluids is developed, which expresses the stress tensor in terms of a von Mises yield surface plus an expansion of acceleration tensors. The purpose of this theory is to represent the flow of concentrated suspensions of small interacting particles in polymer fluids. The 0th-order fluid turns out to be von Mises theory for perfectly plastic solids. The first-order fluid is equivalent to Oldroyd's theory of Bingham plastics. A second-order fluid theory, which is rather complex in form, is also derived.

High speed journal bearings lubricated with electro-rheological fluids: an experimental investigation

Abstract: It is well known that the imposition of an electric field on an Electro-Rheological (ER) fluid alters the viscosity and as a consequence the f flow properties of the f fluid. If such a fluid is used to lubricate a journal bearing system, it is expected that the imposition of an electric field between the rotor and the stator will cause the alteration of the dynamic properties of the journal bearing. For the present, it has been proved that this is valid only for low speeds and high radial clearances of Couette type viscometers. In this paper an experiment in a high speeds (16000 to 65000 s−1) journal bearing with small radial clearance is presented. The experiment performed has showed the phenomenon and has proved that the ER FLUID at high shear rates under constant temperature, follows the Bingham model in realistic bearings. Properties such as wall shear stress, dynamic yield stress relative viscosity are experimentally determined as functions of the electric field, for different particle concentrations and the shear strain rate under constant or free to vary temperature (due to operating conditions, angular velocity, friction). Concluding the ER fluids can be used to create “smart” journal bearings. Vibration controllers can be constructed to control the stability of the ER fluid lubricated bearings.

Axisymmetric creeping flow of a micropolar fluid over a sphere coated with a thin fluid film

Abstract: Consideration is given to the problem of steady axisymmetric Stokes flow of a micropolar fluid past a sphere coated with a thin, immiscible Newtonian fluid layer. Inertial effects are neglected for both the outer fluid and the fluid film. The stream function solutions of the governing equations are obtained in terms of modified Bessel functions and Gegenbauer functions. The explicit expressions of flow fields are determined by applying the boundary conditions at the coated sphere interface and uniform velocity at infinity. The drag force experienced by the fluid-coated sphere is evaluated and its variation is studied with respect to various geometric and material parameters. It is found that a sphere without coating experience greater resistance in comparison to coated fluid. Some well-known results are then deduced from the present study.