Skin Friction Reduction Characteristics Of Flexible Non-smooth Surface

An object is acted upon by fluid drag when it moves in a fluid.Under the influence of fluid drag,which impedes the relative motion,the object needs to consume much energy to maintain its movement in a fluid.With the development of society and the enormous consumption of non-renewable energy resources,the world faces increasing severe energy risk and environment pollution.How to effectively easy up energy crisis and reduce environment destruction has aroused great attention of governments and scholars.Reducing the fluid drag of vehicle moving in a fluid can effectively reduce the energy consumption and protect the environment.In this paper,the skin friction reduction characteristics of flexible non-smooth surface is studied,which is combined with the drag reduction characteristics of flexible wall and non-smooth surface.According to the characteristics of turbulent boundary layer in flat-plate flow,the flexible non-smooth surface is designed and the hemispherical pit structure is chosen;the 3D models of both the fluid and solid domain are constructed by UG NX 8.5 software with the parametric modeling method;the simulation system is built in ANSYS Workbench and the skin friction characteristics of flexible non-smooth surface is studied based on two-way flow-solid interaction;orthogonal test and single factor tests are designed to analyze the skin friction reduction effect of different factors in different levels.Five factors with four levels,such as wall materials,wall thickness,pit diameter,pit depth and Reynolds number,affect the skin friction reduction rate.The orthogonal test results showed that the skin friction are most affected by pit depth and pit diameter;with the increase of pit depth and pit diameter in the design scope,the skin friction reduction is increase;the reduction rate obtained by orthogonal test is between 2.3%?5.8%.The single factor tests are designed with wall material,wall thickness and Reynolds number.The results showed that in the design scope the more flexible the material is,the smaller the skin friction is;the skin friction increases as the wall thickness decreases;the skin friction reduction rate increases as Reynolds number increases.Finally,the skin friction reduction mechanism is studied according to the velocity distribution,turbulent kinetic energy,wall shear stress and wall deformation.