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.

Effects of couple stress on the growth rate of rayleigh-taylor instability at the interface in a finite thickness couple stress fluid

Abstract: In this paper the effects of couple stress fluid on the control of Rayleigh-Taylor instability at the interface between a dense fluid accelerated by a lighter fluid is studied. A simple theory, based on fully developed approximations, is used to derive the growth rate of Rayleigh-Taylor instability. The cutoff and maximum wave numbers and the corresponding maximum frequency are obtained. It is shown that the effect of couple stress parameter reduces the growth rate considerably compare to the classical growth rate in the absence of couple-stress and hence favorable to control the growth rate of surface instabilities in many practical problems.

Hall Effect on the Flow of a Dusty Bingham Fluid in a Circular Pipe

Abstract: In this paper, the transient flow of a dusty viscous incompressible electrically conducting non-Newtonian Bingham fluid through a circular pipe is studied taking the Hall effect into consideration. A constant pressure gradient in the axial direction and a uniform magnetic field directed perpendicular to the flow direction are applied. The particle phase is assumed to behave as a viscous fluid. A numerical solution is obtained for the governing nonlinear equations using finite differences. It is found that the magnetic field decreases the fluid and particle velocities; however, the Hall parameter leads to an increase in the average velocities of both the fluid and particle phases and, consequently, in their flow rates and the velocity gradients at the wall.

A free-boundary problem for viscous fluid flow in injection moulding

Abstract: The injection of a viscous fluid into a mould formed by two parallel plates is considered. The flow front is supposed to move at constant speed. It is assumed that there is complete adherence between the fluid and the mould walls, and that the environmental pressure is constant. For a Newtonian fluid the problem is described in terms of two analytic complex functions. The shape of the fluid surface is calculated by means of a conformal-mapping technique, which leads to a Hilbert problem. The results are compared with known finite-element simulations.

A numerical method for determining the shear stress of magnetorheological fluids using the parallel-plate measuring system

Abstract: This work proposes a new numerical method for determining the shear stress, which does not need any preassumption about the exact behavior of the fluid to achieve absolute data using a parallel-plate measuring system. The ability for representing different behaviors along the entire shear-rate range makes this method particularly interesting for the study of magnetorheological (MR) fluids. In this work, the conversion factors used by the rheometer for concentric-cylinder, cone-plate, and parallel-plate measuring systems are first analyzed. This analysis shows that the software used by the rheometer is not appropriate for the quantitative characterization of non-Newtonian fluids using the parallel-plate measuring system. Therefore, a new method for conversion of the parameters measured by the rheometer to the rheological parameters of the fluid is proposed; simultaneously, this new method is compared with other correction methods proposed in the literature: the Rabinowitsch-type method and the single-point method. Finally, the proposed method is applied for the quantitative characterization of an MR fluid.

Starting solutions for the flow of second grade fluids in a rectangular channel due to an oscillating shear stress

Abstract: The unsteady motion of a second grade fluid between two parallel side walls perpendicular to a plate is studied by means of the Fourier sine and cosine transforms. Initially, the fluid is at rest and at time t = 0+, the plate applies an oscillating shear to the fluid. The solutions that have been obtained, presented under integral and series form and written as a sum between steady time-periodic and transient solutions can be easily reduced to the similar solutions for Newtonian fluids performing the same motion. They describe the motion of the fluid some time after its initiation. After that time, when the transient solutions disappear, the motion of the fluid is described by the steady time-periodic solutions that are independent of the initial conditions. In the absence of side walls, more exactly when the distance between walls tends to infinity, all solutions reduce to those corresponding to the motion over an infinite plate. As it was to be expected, the steady time-periodic solutions corresponding to sine and cosine oscillations of the shear stress on the boundary differ by a phase shift. Finally, the influence of side walls on the fluid motion, the required time to reach the steady periodic flow, as well as the distance between walls for which the velocity of the fluid in the middle of the channel is unaffected by their presence are established by numerical calculus and graphical illustrations. As expected, the time needed to reach the steady periodic flows is lower in the presence of side walls. It is lower for Newtonian fluids in comparison with second grade fluids and greater for sine oscillations in comparison to the cosine oscillations of the boundary shear.