The flow control strategy combined upstream wakes and surface roughness on boundary layer development were investigated experimentally

and the effect of freestream turbulence intensity(FSTI) on the separations and transitions characteristic of the boundary layer in the flow control process was also studied.Result shows that the roughness strip with the ratio of roughness height and chord of 1.05×10-4 deposits between the velocity peak and separation onset can reduce the profile loss at freestream turbulence intensity of 0.4% and 2.2% in the low Reynolds number. At Reynolds number of 85000

the boundary layer momentum thickness in wakes passing region

wakes-induced transition region and natural transition region is affected by the FSTI

thus

resulting in a difference of the profile loss at the two operating conditions. However

there is no variation of the calmed region at different FSTI.