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.

Viscoelastic constitutive model of unvulcanized rubber

Abstract: Based on rheological test results, a new viscoelastic constitutive equation for unvulcanized rubber has been set up, with mathematical justification to describe its mechanical properties in relation to the yield stress and shear-thinning effect. In this model, every term or coefficient has an explicit physical meaning. The proposed model indicates that the yield stress is one of the main causes for the shear-thinning effect and reveals why some materials possess double-Newtonian regions with the shear viscosity in the first region higher than that in the second region. The yield stress makes the flow index of the power law fluid model vary widely, so that it needs to be eliminated from the power law fluid model. The model can also distinguish the true shear viscosity from the apparent shear viscosity effectively. The parameters of the equation are determined by the step fitting method, which is the precondition for quantitative analysis. However, the equation is a one-dimensional model, so further research is needed.

Effect of Regularization Parameter on Flow Field and Power Consumption in Agitated Vessel by Two Blade Impeller

Abstract: The existence of residual stress, or yield stress, in fluid mechanics has been first modeled by Bingham (1), who foresaw a value for the limit tension beyond which the material would present a viscous flow using a linear model. Such physical system not only raises the viscosity but also imposes a resistance that shall be exceeded for the material to flow normally, requiring the destruction of the material structure so that it flows in a viscous manner. For this model there is lack of numerical methods able to deal with the inequality restriction. Thus, regularization methods have been proposed where, in a way, they eliminate the restriction and, on the other hand, they introduce constitutive nonlinearities in the relation between the stress tension and the shear rate. In this work, the characterization of hydrodynamic fields of incompressible yield stress fluid with regularization model of Bercovier and Engelman in a cylindrical vessel not chicaned equipped with two blade stirrer was undertaken using a code Fluent CFD 6.2.13 based on discretization to finite volume method the Navier Stokes equations formulated variables to study the influence of inertia by varying the Reynolds number and the influence of plasticity by the number variation Bingham fluid flow and show that the existence a flow threshold characterized by the number of Hedstrom can lead to a quasi-immobilization zones within the system agitation for the simulated geometry.

Pressure Distribution in a Porous Squeeze Film Bearing Lubricated with a Herschel-Bulkley Fluid

Abstract: Abstract The influence of a wall porosity on the pressure distribution in a curvilinear squeeze film bearing lubricated with a lubricant being a viscoplastic fluid of a Herschel-Bulkley type is considered. After general considerations on the flow of the viscoplastic fluid (lubricant) in a bearing clearance and in a porous layer the modified Reynolds equation for the curvilinear squeeze film bearing with a Herschel-Bulkley lubricant is given. The solution of this equation is obtained by a method of successive approximation. As a result one obtains a formula expressing the pressure distribution. The example of squeeze films in a step bearing (modeled by two parallel disks) is discussed in detail.

Features of viscous-fluid flow in an elastic pipeline

Abstract: Based on N. E. Zhukovskii’s investigations of fluid flow in a pipe whose walls can expand, the basic hydrodynamic equations in such a pipeline have been found with the vector form of the Newton law for a viscous fluid. The analog of the Poiseuille formula for the fluid flow rate in an elastic pipeline has been determined. A comparative analysis of the viscous flow in elastic and rigid pipelines has been made. It has been shown that the relationship between the maximum velocity of the fluid in the pipeline cross section and the crosssection-average velocity is the same for elastic and rigid pipelines.