Research On Friction Reducetion Mechanism And Design Method Of The Bionic Micro-structure Surface

The study aims at the demand of high efficiency drag reduction technology for underwater vehicles,with the help of advanced numerical simulation technology and the principle of experimental verification,and establishes the relationship between the characteristic parameters of fine flow structure and friction in the near wall turbulent boundary layer,reveals the mechanism and law of friction drag reduction technology of bionic wall.The theoretical basis and technical support for the research and development of new bionic drag reduction technology are developed.Firstly,a thorough literature review was carried out.Secondly,the shear stress measurement technology underwater based on MEMS were established which can provide the effective validate means for the numerical simulation of the turbulence boundary layer coherent structure.A calculation method by LES for the numerical simulation of the fine flow structure on the surface of bionic microstructure was developed and verified by the results of MEMS shear stress test and direct numerical simulation,which can realized the global computation of the surface flow of bionic micro structures under high Reynolds number.The characteristic parameters of the coherent structure of the turbulent boundary layer and the significant parameters which determine the wall friction were extracted;the relationship between the wall friction and the characteristic parameters of mean flow and coherent structure was discussed,which provides a theoretical basis for the quantitative research and design application of the drag reduction mechanism on the bionic microstructure surface.The different drag reduction mechanisms of two typical bionic surfaces of the grooves and the traveling waves are quantitatively revealed which can provide the technical guidance for the design of bionic drag reduction surface microstructure.Finally,a new design method of the surface structure for compound friction reduction is presented,which is based on the coupling optimization of the friction reduction mechanisms of the grooves and the traveling wave.A kind of bionic fish scale composite drag reducing surface was designed,the drag reduction effect was evaluated,and the design idea of the friction reducing resistance and the friction resistance of the bionic composite surface were verified which can offer the technical basis for bionic drag reduction technique research.