Computation of Multiphase of Particle Laden Complex Fluids
Over the last five decades, particle dynamics in viscoelastic fluids have been extensively studied experimentally; however, the interplay of multiple physical variables and flow parameters turn experiments into a high-dimensional challenge. Therefore, when dealing with such complex fluid/solid multiphase systems, the availability of comprehensive computational fluid dynamic (CFD) tools can play a major role in exploring parameter space. With ever-increasing computing power, it is becoming possible to develop robust and accurate computational tools that can resolve the behavior of multiphase complex fluids, involving the effects of microstructural evolution, nonlinear matrix fluid rheology, particle and fluid inertia, viscoelasticity, flow-unsteadiness, and many-body interactions, in addition to complex multi-connected and evolving computational domains.
The flow of complex fluids is a ubiquitous problem in advanced manufacturing operations, e.g., polymer processing of highly-filled viscoelastic melts and elastomers, cementing and hydraulic fracturing operations using solids-filled muds and slurries as well as biological applications, e.g., the flow-induced migration of circulating cancer cells in biopolymeric media such as blood. In a viscoelastic fluid, in addition to the complexities coming from the particle shape and volume fraction, the presence of a wide range of internal time-scales and length-scales describing the material microstructure makes the dynamics very challenging to parameterize, both experimentally and numerically. For the latter to be applied to systems with a large number of particles, a detailed coupling model, between the discrete and continuous phases, is required, and it should integrate all interactions on various length scales.
To simulate the bulk flow of complex fluids, comprising a viscoelastic fluid with disperse particles, a robust three-dimensional numerical model, based on the Eulerian-Lagrangian multiphase approach, is being developed. This model integrates the presence of particles as the discrete phase embedded in a viscoelastic fluid, which is treated as a continuum phase. The continuity, momentum and constitutive rheology equations are solved for the viscoelastic continuum, and a momentum exchange model is used to couple the constituent phases. Therefore, several constitutive laws for drag, lift, hindrance and retardation are required to account for the transport of the discrete phase. To develop drag and lift models, we use a detailed 3D numerical model to study the viscoelastic flow past a single particle. For the hindrance and retardation, we separately consider the flow past a collection of particles randomly distributed, which involves a large number of production runs, O(104). These extensive CFD investigations with detailed meshes, requires powerful computing resources as offered by Gompute. The capacity of the Gompute cluster and booking scheme can be customized conveniently to meet the requirements of this computational rheological framework. The opensource computational library OpenFOAM® is being used to perform all the studies and numerical developments.
Results and benefits
The access to Gompute computational facilities allows us to perform the large number of parametric numerical studies mandatory to devise accurate coupling models, covering a wide range of flow conditions and material system properties, within a reasonable timeframe. Moreover, with such computational power, the EulerianLagrangian solver under development can be used to study in detail the complex behavior of multiphase material systems of interest in several fields, such as: polymer processing, cementing and hydraulic fracturing operations and many biological applications. These possibilities are expected to provide us with a better understanding of the major underlying physical phenomena and, consequently, have a major impact on the design of systems composed of the multiphase complex materials of interest.