Effects of localized blowing on the turbulent boundary layer over 2D roughness

Planar particle image velocimetry was utilized to investigate the effects of localized blowing (injection) on the turbulent boundary layer over two-dimensional k -type roughness. The experiments were performed at a Reynolds number of 100,000, based on the boundary layer thickness and the free-stream velocity. The roughness was composed of identical transverse square bars at a pitch to height ratio p/k = 11 ; the bars occupied ∼ 13-14% of the boundary layer thickness. In addition to a baseline no-injection case, localized blowing through five small spanwise jets was considered at two rates and for two injection locations. The volumetric flow rate through the jets was below 0.12