Numerical Modelling of Mineral-Slurry Like Flows in a 3D Lid-Driven Cavity Using a Finite Element Method Based Tool

Mining companies continuously set aside large amounts of resources to optimize their mineral extraction processes. This is because energy costs and greenhouse gas emissions can be significantly reduced by optimizing such processes. Mineral processing often involves transporting mixtures of water and/or chemical solutions carrying ground rocks known as mineral-slurries. Mineral-slurry transport entails indeed multiphase flows featuring solid, liquid and gas phases. During normal operation of mineral-slurry transport systems, a turbulent regime has to be maintained in order to avoid solid particle sedimentation on system walls. Based on their rheological behavior, mineral-slurries may exhibit Newtonian or non-Newtonian rheological properties.

Finite element methods (FEM) can be used to numerically solve different multiphase flows present in practical applications. Industrial device designing and/or operating conditions optimization are some of the main FEM practical applications. In order to numerical model mineral-slurry transport processes, a FEM based module belonging to a larger computational package called CFLOWSS (Complex FLOWS Solver) is utilized in this work. CFLOWSS is an in-house code under continuous development. Previous works carried out using the referred computational tool, including 2D laminar mineral-slurry transport and neighbor particle searching methods based on discrete element methods (DEM), are currently publicly available. A three dimensional FEM based model is particularly utilized here for numerically simulating turbulent mineral-slurry transport in horizontal pipes.

Accordingly, the development of a 3D FEM module and its implementation in the CFLOWSS computational package is firstly described. Galerkin’s method is utilized in the CFLOWSS FEM module because of its known advantages when compared to other similar methods. The implementation in CFLOWSS of a Large Eddy Simulation (LES) model to deal with turbulence is described next. In particular, turbulent inflow boundary conditions and filtering processes of Navier-Stokes equations accounting for large and small eddy scales are discussed. An object-oriented programming (OOP) paradigm is utilized in both implementations. The developed models and algorithms are validated using canonical configurations involving turbulent flows in horizontal pipes as well as Newtonian and non-Newtonian fluids. The multiple block computational grid employed in the simulation of the referred configurations features a Cartesian mesh in the center of the pipe and a cylindrical one around it. Finally, a practical application of mineral-slurry transport in horizontal pipes is studied using CFLOWSS. In this application, the mineral-slurry transport is described by a turbulent non-Newtonian flow. The main results highlight the CFLOWSS applicability  for realistically representing mineral-slurry transport related processes in horizontal pipes. Future developments of CFLOWSS will include accounting for multiphase flows and fluid-particle interaction models.