Comparing Turbulent Dispersion Models for RANS Simulations of Particle-Laden Flows

The ingestion of sand-particles into turbomachinery decreases their longevity and perfor- mance and can even lead to failure. To address these problems, studying particle-laden flows is of high interest in the field. Due to their low computational cost, RANS simulations remain the preferred method in the design phase of engineering solutions. The reduction in computational cost stems from the fact that RANS simulations neglect velocity fluctuations and solve for the time averaged velocity field. This leads to non-physical results since these velocity fluctuations affect the particle trajectories. To improve the accuracy, the simula- tions of the particles are adapted with particle dispersion models that calculate the velocity fluctuations. This work investigates the dispersion of sand particles due to different types of particle dispersion models. A converging pipe with subsequent impact plate is used for this study. Spherical sand-particles ranging in size from 5 to 100 microns in diameter are injected against the main fluid flow into the pipe. The commercial CFD software Ansys Fluent is used and the RANS simulations are run with the k-omega SST turbulence model. Variants of both the Discrete Random Walk (DRW) and Continuous Random Walk (CRW) dispersion models are looked at. Tracer particles stayed close to the center axis inside the pipe and showed the largest dispersion through the models. The dispersion was higher for the CRW compared to the DRW model for all particle sizes. Inertial particles reached the inner walls of the pipe and showed a reduced effect by the dispersion models. The dispersion for larger particles mainly depends on the particle-wall interactions.