The first surface structure (鈥渧elvet聽1鈥? mimics the length and density of the hairs and the softness of the natural owl-wing surface. It diminishes the size of the separation bubble or completely prevents separation. However, at three-dimensional flow the effect of the 鈥渧elvet聽1鈥?surface is clearly reduced. The 鈥渧elvet聽2鈥?surface consists of longer and thinner filaments than the 鈥渧elvet聽1鈥?surface. At the lower Reynolds numbers (), the 鈥渧elvet 2鈥?surface structure does not alter the near-wall flow field significantly. However, at the 鈥渧elvet聽2鈥?surface structure serves as a distributed field of moving roughness elements such that the size of the separation bubble is reduced and becomes nearly independent of the angle of attack. When the three-dimensional flow field at the highest Reynolds number () is considered it is evident that the 鈥渧elvet聽2鈥?surface yields the aerodynamically more stable flow field.