The Numerical Research of Drag Reduction Over Bionic Fluctuation-adaptive Non-smooth Surface

This paper does some research about the drag reduction mechanism of dolphin's soft and adaptive skin in view of bionics. The study shows that dolphin skin is very sensitive to pressure changed by external flow field, and can do a wave-like movement with the uneven pressure, resulting in a traveling wave of the non-smooth surface which reducing frictional resistance on the wall surface in the turbulent flow field. Based on Karman vortex street and momentum theory, we described the relationship between the geometry of traveling wave and the drag reduction efficiency, and with the help of numerical simulations of traveling wave surface using RNG k-epsilon model and a series of experiments, we get the friction coefficient near the wall boundary, the turbulence intensity, and the distribution of the velocity field. The results show that, compared with smooth surface, the non-smooth surface of traveling wave reduces frictional resistance of the adhesion surface owing to changing the fluid flow state. Moreover, the non-smooth surface of traveling wave shows significant drag reduction effect at the stream velocity about 6 m / s.