Volume fraction gradient effects in compressible particle-laden flow

The effect of volume fraction gradients in compressible particle-laden flow is investigated using data from particle-resolved simulations of flows through random beds of fixed particles. Accurate prediction of particle forces is essential for simulations of engineering systems such as pneumatic conveying, fluidized beds and more. The results of the present study shows that the forces on the particles can be predicted reasonably well by a drag law developed for homogeneous flow conditions; however, a systematic underprediction with steepening volume fraction gradient is observed. This indicates that particle gradient effects should be accounted for in the drag law to obtain more accurate results. Sharper volume fraction gradients also result in increasing pseudo turbulent stress contributions in the momentum balances. Nevertheless, the overall direct contribution of the pseudo turbulence remains small for the cases considered here.