Experimental and numerical studies on the wall-roughness effect to particle dynamics in various gas-particle flows

The effect of wall roughness on particle dynamics in gas-particle flows has been studied both experimentally and numerically, but mainly for channel, pipe, and boundary-layer flows. The present authors did numerical studies and detailed phase-Doppler particle anemometry (PDPA) measurements on the effect of wall roughness for particle dynamics in separating (sudden-expansion and swirling) gas-particle flows, as well as channel flows. The simulated gas-particle flow showed that the prediction results accounting for the wall roughness agree well with the measurement results. The PDPA measurements of backward-facing step gas-particle flows showed that as the wall roughness increases, the longitudinal and the transverse time-averaged particle velocities decrease, but the longitudinal and transverse particle fluctuation velocities i ncrease.