Eulerian-Lagrangian Analysis of Cloud Evolution using CFD Coupled with a Sediment Tracking Algorithm

The two-phase flowfield environment around a hovering micro-rotor is simulated using a fluid dynamics solver coupled with a Lagrangian sediment tracking algorithm. The present work attempts to examine the capabilities of a high fidelity CFD analysis together with a sediment tracking algorithm to analyze the evolution of brownout clouds. The effect of particle size on the evolution of the cloud and the predominant transport mechanisms are analyzed and compared with experimental data. The resolution of vortices for longer wake ages by the CFD solver along with better estimation of velocity profiles further outboard of the rotor were shown to be vital for the coupled simulation to achieve qualitative agreement with experiment. This better resolution is achieved through the use of additional overset meshes placed near the ground. Three size ranges of spherical particles are used to represent the sediment bed. The variation of the phenomenological attributes of the cloud evolution as a function of particle size was analyzed and found to agree with experimental evidence.