A two-fluid model for numerical simulation of shear-dominated suspension flows. (November 2019)

• Record Type: Journal Article
• Authors: Municchi, Federico; Nagrani, Pranay P.; Christov, Ivan C.
• Is Part Of: International journal of multiphase flow. Volume 120(2019)
• Publication Date: 2019-11
• Subjects: Suspensions -- Two-fluid model -- Particle migration -- Multiphase flow -- OpenFOAM; Multiphase flow -- Periodicals; Écoulement polyphasique -- Périodiques; Multiphase flow; Periodicals; 620.1064
• DOI: 10.1016/j.ijmultiphaseflow.2019.07.015
• Languages: English
• ISSNs: 0301-9322

Abstract

Highlights: Robust modeling framework for non-Brownian suspensions without the assumption of steady suspension velocity. Successful implementation of a TFM for dense suspensions using closures from the literature. Publicly available implementation of the TFM using the FVM toolbox OpenFOAM®. Series of successful benchmark problems, including curvilinear coordinates and 3D flows. Graphical abstract: Abstract: Suspension flows are ubiquitous in nature (hemodynamics, subsurface fluid mechanics, etc.) and industrial applications (hydraulic fracturing, CO2 storage, etc.). However, such flows are notoriously difficult to model due to the variety of fluid-particle and particle-particle interactions that can occur. In this work, we focus on non-Brownian shear-dominated suspensions, where kinetic collisions are negligible and frictional effects play a dominant role. Under these circumstances, irreversible phenomena such as particle diffusion and migration arise, requiring anisotropic stress models to describe the suspension rheology. On a continuum level, reduced-order models such as the suspension balance model (SBM) or the diffusive flux model are commonly used to predict particle migration phenomena. We propose a new method based on a two-fluid model (TFM), where both the phases are considered as interpenetrating continua with their own conservation of mass and momentum equations. Without employing the nowadays customary simplifications in applying the SBM, we close the "full" TFM instead. Specifically, we show that when an anisotropic stress analogous to that used in the SBM is added to the equilibrium equations for the particle phase, the TFM is able to accurately predict particle migration. Thus, the TFM does not require the assumptions of a steady suspension velocity and a Stokesian (inertialess) fluid, and the TFM can be easily extended to include buoyancy and even kinetic collisional models. We present several benchmark simulations of our TFM implementation in OpenFOAM®, including in curvilinear coordinates and three-dimensional flow. Good agreement between the TFM solutions and previous experimental and numerical results is found.