Impact of a binary size distribution on particle erosion due to an impinging gas plume

Abstract

Solid particles of nonuniform sizes exhibit behaviors not seen in monodisperse distributions. Following a previous study of monodisperse particles, the goal of this study is to investigate effects of a binary-size distribution on erosion of lunar soil from a rocket landing. The discrete element method is used to examine near-field (near impingement) and far-field behavior. For near-field simulations, small particles preferentially collide with large particles from below, due to a difference in velocity caused by gas forces, which is analogous to behavior for entrainment in gas-solid fluidized beds. These collisions cause vertical momentum transfer from small to large particles that affects species and total erosion flux. For far-field simulations, collisions result in an increase in vertical dispersion (binary) and a reduction in maximum horizontal velocity (binary and monodisperse). These results have implications on the most appropriate modeling framework to use for predictions over large distances utilizing wide size distributions. V C 2015 American Institute of Chemical Engineers AIChE J, 62: 984-995, 2016Initial simulation domain is in the bottom left corner (50 wt % large; size ratio 4).