Research On Underwater Drag Reduction Technology Of Bionic Non-smooth Surface

In this paper,the development status and characteristics of various turbulence drag reduction methods are compared and analyzed,and the direction of this research is determined to be bionic non-smooth surface drag reduction technology.And based on the background of research on drag reduction in underwater vehicles,the bionic inspiration was taken from the skin structure of killer whales.In this study,a new bionic traveling wave surface that can significantly reduce the drag of underwater vehicle is designed based on bionic principles using the killer whale skin ridge as a bionic prototype.The effect of depth,width-to-depth ratio and inlet velocities on the drag reduction performance of the traveling wave surface was investigated by numerical simulation.And the effects of periodic traveling wave structures aligned perpendicular to the flow direction on the evolution of a turbulent boundary layer flow was explored.The results evidence that the smaller the depth,the better the drag reduction effect of the traveling wave surface,and the maximum total drag reduction ratio reaches 9.63%.Comparing the flow fields of the traveling wave surface and smooth surface,it is found that the bionic traveling wave surface can increase the thickness of the bottom layer of the turbulent boundary layer,reduce the velocity gradient,inhibit the burst of turbulence,make the flow more stable,and thus resulting in a decrease in f friction drag of the surface.The bionic traveling wave surface was applied to the SUBOFF submarine model for drag reduction optimization design to verify the drag reduction performance of the traveling wave surface,and the numerical simulation model of the SUBOFF submarine was calculated.It was found that compared with the smooth submarine model,the accompanying traveling wave structure arranged in the parallel midbody effectively reduced the wall shear stress in the parallel midbody and aft body regions of the submarine,suppressed the turbulent velocity pulsation,resulting in a significant decrease in turbulent kinetic energy,and verified the drag reduction mechanism.Moreover,the submarine with the traveling wave surface achieved a maximum total drag reduction of 11.31%.The calculation results show that the new bionic traveling wave surface has a wide range of application,which can effectively reduce the total drag of underwater vehicles.This will provide a useful reference for the practical application of bionic non-smooth drag reducing surfaces.The active motion standing wave surface was investigated by the dynamic mesh model and user defined function.It was found that although the periodic motion standing wave surface can achieve good drag reduction effect at high frequency,the drag reduction performance will be limited by the inlet velocities and is not stable.And the periodic variation of the flow field on the standing wave surface is analyzed to explore its drag reduction mechanism.