Development and Validation of an Open-Source Finite-Volume Method Solver for Viscoplastic Flows

Abstract

In the present paper, we discuss implementation details of a free and opensource numerical solver based on the finite volume method for numerical simulation of viscoplastic non-Newtonian fluids. In addition to the fact that they are involved in many industrial applications, both their physical properties and their rheological behavior make them challenging for numerical simulation. Viscoplastic fluids are known to behave as solid unless the shear stress reaches a critical level, known as yield-stress, beyond which they behave as liquid. In most cases, both yielded and unyielded regions coexist in the fluid domain. In mathematical model of viscoplastic fluid, the constitutive equation is a non-differentiable function. This is often overcome by using the approximate constitutive equation that has a regularized form, e.g. the Papanastasiou regularization model. Using the same approach, we assess the influence of regularization parameters on simulation convergence and results accuracy. In this study, we give implementation details of viscoplastic fluid models in freeCappuccino open-source Computational Fluid Dynamics code. Moreover, we perform validation on several well known benchmark cases and compare proposed approach with those existing in published literature. We also perform a parametric analysis and show the effect of Reynolds and Bingham numbers on the extent of the yielded regions. Conclusions of the study have relevance in practical application of computational fluid dynamics to viscoplastic fluids in particular and to non-Newtonian fluids in general.