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.

Unsteady MHD Couette flow of a generalized Oldroyd-B fluid with fractional derivative

Abstract: This paper presents an analytical study for the magnetohydrodynamic (MHD) flow of a generalized Oldroyd-B fluid. The fractional calculus approach is used to establish the constitutive relationship model of a viscoelastic fluid. Exact analytic solutions for the velocity field and shear stress in terms of Fox H-function are obtained by means of the Laplace transform. The influence of the relaxation and retardation times, the orders of the time fractional derivative and the magnetic body force on the velocity and shear stress are analyzed. It is shown that the ordinary Oldroyd-B fluid, generalized second grade fluid and Maxwell fluid are the limiting cases of the presented results.

Flow and Displacement of Bingham Non-Newtonian Fluids in Porous Media

Abstract: well-test-analysis method was developed, and its application dem­ onstrated by analyzing two simulated pressure-drawdown and -buildup tests of a Bingham fluid. The displacement of a Bingham fluid by a Newtonian fluid is shown to proceed with rather limited efficiency owing to the presence of an ultimate (limited) displace­ ment saturation, which is a characteristic of two-phase Bingham flow. Once the saturation in the two-phase flow system reaches the ultimate saturation, no further improvement of displacement effi­ ciency can be obtained regardless of how long the displacement operation continues under the same flow conditions. We also developed a numerical model for single- and multiphase Bingham-fluid flow through porous media by suitably modifying a general-purpose multiphase reservoir simulator. The model was used to test our analytical solutions and to generate well-testing data for the proposed well-test analysis for Bingham fluids. Bingham Fluid and Rheological Model As a special kind of non-Newtonian fluid, Bingham fluids (or plas­ tics) exhibit a finite yield stress at zero shear rate. The physical behavior of fluids with a yield stress usually is explained as an in­ ternal structure in three dimensions that is capable of preventing movement for values of shear stress less than the yield value, Ty . For shear stress T> T y' the internal structure collapses completely, allowing shearing movement to occur. The characteristics of these fluids are defined by two constants: the yield stress, T y , which is the stress that must be exceeded for flow to begin, and the Bing­ ham plastic coefficient, Jl.B' The rheological equation for a Bing­ ham plastic is 14

On the role of the ambient fluid on gravitational granular flow dynamics

Abstract: The effects of the ambient fluid on granular flow dynamics are poorly understood and commonly ignored in analyses. In this article, we characterize and quantify these effects by combining theoretical and experimental analyses. Starting with the mixture theory, we derive a set of two-phase continuum equations for studying a compressible granular flow composed of homogenous solid particles and a Newtonian ambient fluid. The role of the ambient fluid is then investigated by studying the collapse and spreading of two-dimensional granular columns in air or water, for different solid particle sizes and column aspect (height to length) ratios, in which the front speed is used to describe the flow. The combined analysis of experimental measurements and numerical solutions shows that the dynamics of the solid phase cannot be explained if the hydrodynamic fluid pressure and the drag interactions are not included in the analysis. For instance, hydrodynamic fluid pressure can hold the reduced weight of the solids, thus inducing a transition from dense-compacted to dense-suspended granular flows, whereas drag forces counteract the solids movement, especially within the near-wall viscous layer. We conclude that in order to obtain a realistic representation of gravitational granular flow dynamics, the ambient fluid cannot be neglected.

Radiative flow of MHD Jeffrey fluid past a stretching sheet with surface slip and melting heat transfer

Abstract: The present paper investigates numerically the influence of melting heat transfer and thermal radiation on MHD stagnation point flow of an electrically conducting non-Newtonian fluid (Jeffrey fluid) over a stretching sheet with partial surface slip. The governing equations are reduced to non-linear ordinary differential equations by using a similarity transformation and then solved numerically by using Runge–Kutta–Fehlberg method. The effects of pertinent parameters on the flow and heat transfer fields are presented through tables and graphs, and are discussed from the physical point of view. Our analysis revealed that the fluid temperature is higher in case of Jeffrey fluid than that in the case of Newtonian fluid. It is also observed that the wall stress increases with increasing the values of slip parameter but the effect is opposite for the rate of heat transfer at the wall.