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 increase.