Simulation of Particle-laden Turbulent Flow in OpenFOAM

Our work attempts to provide a comprehensive analysis of modelling two-phase flows (fluid-particle) with regard to computational requirements, available models, challenges and limitations. The adopted case (particle-laden backward facing step (BFS) flow) is numerically simulated in the framework of Eulerian-Lanrangian method (RANS-DEM) using OpenFOAM. Firstly, the case was simulated as single-phase (fluid without particles) using solver pimpleFOAM in order to define the simulation parameters and the meshing requirement, giving good agreement with the measured fluid velocity profiles in the experiment. Later on, the case was modified as a two-phase system by including the particles and simulated using two similar yet different solvers namely DPMFoam (standard OpenFOAM solver) and pimpleLPTFoam (self-compiled solver). The simulation results obtained from these two solvers demonstrate almost no difference due to small concentration of particles, indicating that one can save significant computational resources by not considering void fraction in the governing fluid flow equations. Investigation on the coupling regime demonstrates almost no difference in predicted fluid and particle velocity profiles corresponding 1-way and 2-way coupling, as the small number of particles in each CFD cell are unable to modify flow fields significantly. Analysis on different initial velocities of particles shows that by proving zero initial velocity to the particles, they get the opportunity to attain the real velocity depending upon the flow around them and the particle response time (Stokes number). Our study shows that RANS-DEM with simple dispersion models is unable to predict the particle dispersion correctly, thus more sophisticated dispersion models are required.