Topic
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.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, it was shown that the low-stress Newtonian viscosity is an artifact that arises in non-steady state experiments, and that the value of the "Newtonian viscoity" increases indefinitely.
Abstract: For more than 20 years it has been debated if yield stress fluids are solid below the yield stress or actually flow; whether true yield stress fluids exist or not. Advocates of the true yield stress picture have demonstrated that the effective viscosity increases very rapidly as the stress is decreased towards the yield stress. Opponents have shown that this viscosity increase levels off, and that the material behaves as a Newtonian fluid of very high viscosity below the yield stress. In this paper, we demonstrate experimentally (on four different materials, using three different rheometers, five different geometries, and two different measurement methods) that the low-stress Newtonian viscosity is an artifact that arises in non–steady-state experiments. For measurements as long as 104 seconds we find that the value of the "Newtonian viscosity" increases indefinitely. This proves that the yield stress exists and marks a sharp transition between flowing states and states where the steady-state viscosity is infinite —a solid!
175 citations
TL;DR: In this paper, the effects of fluid overpressures and seepage forces in tectonics using the results of scaled physical models were demonstrated using experiments where air flows through sand packs.
173 citations
TL;DR: In this article, the authors describe non-Newtonian effects on the viscosity of two-phase fluids with complex structure, such as macromolecular fluids, soap solutions, and soap solutions.
Abstract: Here 1t is the total momentum flux (or stress tensor), defined in such a way that the force transmitted from the negative side of a surface element of unit area and normal vector n is [n· 1t] (Bird, Stewart & Lightfoot 1960). The symbol b stands for the unit tensor, , is the extra stress tensor, p is the isotropic pressure, and y = (Vv) + (Vv)t is the rate-of-strain tensor; the viscosity Il depends on temperature, pressure, and concentration, but not on the time t or on any kinematic quantities such as y. It is well known that liquids with complex structure, such as macromolecular fluids, soap solutions, and two-phase fluids are not described by (1). The following are some of the "non-Newtonian" effects that have been observed:
172 citations
TL;DR: This work applies sensitivity-based optimization procedure to a flow through an idealized arterial graft, and introduces an additional factor in the form of a geometric parameter, and study its effect on the optimal shape obtained.
Abstract: We investigate the influence of the fluid constitutive model on the outcome of shape optimization tasks, motivated by optimal design problems in biomedical engineering. Our computations are based on the Navier-Stokes equations generalized to non-Newtonian fluid, with the modified Cross model employed to account for the shear-thinning behavior of blood. The generalized Newtonian treatment exhibits striking differences in the velocity field for smaller shear rates. We apply sensitivity-based optimization procedure to a flow through an idealized arterial graft. For this problem we study the influence of the inflow velocity, and thus the shear rate. Furthermore, we introduce an additional factor in the form of a geometric parameter, and study its effect on the optimal shape obtained.
171 citations
TL;DR: In this article, the authors discuss the ability of regularized Herschel-Bulkley models such as the Papanastasiou, the bi-viscosity and the Bercovier and Engelman models in determining the topography of the yield surface.
Abstract: Herschel–Bulkley fluids are materials that behave as rigid solids when the local stress τ is lower than a finite yield stress τ0, and flow as nonlinearly viscous fluids for τ>τ0. The flow domain then is characterized by two distinct areas, τ τ0. The surface τ=τ0 is known as the yield surface. In this paper, by using analytic solutions for antiplane shear flow in a wedge between two rigid walls, we discuss the ability of regularized Herschel–Bulkley models such as the Papanastasiou, the bi-viscosity and the Bercovier and Engelman models in determining the topography of the yield surface. Results are shown for different flow parameters and compared to the exact solutions. It is concluded that regularized models with a proper choice of the regularizing parameters can be used to both predict the bulk flow and describe the unyielded zones. The Papanastasiou model predicts well the yield surface, while both the Papanastasiou and the bi-viscosity models predict well the stress field away from τ=τ0. The ...
168 citations