Research about the characteristic of drag reduction over riblets surface based on average velocity profile in the turbulent boundary layer

Through thorough analysis about the characteristic of average velocity profile in the turbulent boundary layer over riblets surface that was measured by a hot wire anemometry in a miniature special wind tunnel, the drag reduction ranges and rules were acquired. In the calculation of virtual origin and wall friction velocity of riblets surface, a modified method was presented to obtain virtual origin and wall friction velocity together by least-squares fitting method, based on Spalding formula in the turbulent boundary layer. In the calculation of the friction drag of models, a calculating method based on momentum integral equation for boundary layer was adopted, which could efficiently reduce the effect of testing errors of local testing point on calculation precision of models' friction drag. Ultimate results show that riblets thicken the viscous sub layer in the turbulent boundary layer, and decrease normal velocity grads of near wall, and boost up the buffer zone and logarithm region; the range of none dimension riblet width s⁺ is about 6 to 18, when there exists the drag reduction effect, and the maximal drag reduction quantity about 7.7% appears when s⁺ ≈ 12.