Micro dimpling can be used to create surfaces with reduced effective friction for solids flows. Therefore, micro dimpling is a candidate for surface treatment of the walls of bins and hoppers to improve solids flow without using a coating. In the current work, we experimentally evaluate the effective wall friction reduction associated with micro dimpling using Schulze Ring Shear testing and a Jenike Shear testing to measure the wall friction angle. Specifically, we measure the wall friction angle of bulk solids on wall coupons before and after micro dimpling. To evaluate whether the reduction in effective wall friction angle is due to a reduction in surface friction or a reduction in adhesion, the wall friction angle is measured for both cohesive (limestone) and non-cohesive (silica sand) bulk solids. We also consider different initial finishes (prior to micro dimpling) of the wall coupons. We find that micro dimpling does not improve the effective wall friction angle for certain initial coupon finishes.
