Experimental Study Of Drag Reduction Performance And Mechanism Of Thermally Conductive Elastic Bionic Wall In Internal Flow

Thermally conductive elastic bionic wall is a composite surface which both with good elasticity and thermal conductivity,and it is designed to solve the aging problem of the elastic surface which imitated dolphin skin,which due to the transformed heat couldn't conduction to the outside timely,and improve its drag reduction performance.In this paper,the material properties of the thermally conductive elastic bionic wall made of graphite with high thermal conductivity as the filler and the silicone rubber as the base material were tested and analyzed.The drag reduction performance and mechanism of thermally conductive elastic bionic wall which used as the wall of internal flow field were studied.The complex relationship between thermally conductive elastic bionic wall and the fluid is a multi-physics coupling of the flow-solid-heat.According to GB7757,GB528,GB12830 and other standards,the compression performance,tensile properties and shear properties of of thermally conductive elastic bionic wall with different graphene content were studied.The results show that their elastic modulus is basically the same,and showing a high degree of non-linearity.The hysteresis curves in the compression mode were obtained by the rubber electronic tensile testing machine.The heat loss was calculated at 0.25,and the loss factor was obtained.The results were verified by the dynamic thermomechanical analyzer.Indicating that the content of graphene has little effect on the dynamic heat generating capacity of the elastic thermal biomimetic surface.The results show that the thermal conductivity of the silica gel can significantly improve the thermal conductivity of the silicone rubber,the greater the graphene filling,the greater the thermal conductivity of the surface of the thermally conductive elastic bionic wall.Considering of the characteristics of the surface of thermally conductive elastic bionic wall,a bionic functional surface flow test system based on differential pressure test principle was designed.Types of thermally conductive elastic walls with different thicknesses were prepared to study the drag reduction performance among elastic and rigid walls.According to the experimental results,the thermally conductive elastic wall exhibited the most optimal drag reduction effect.The maximum drag reduction rate of the elastic wall reached 8.54%.At a flow speed of 1.5 m/s,the thermally conductive elastic wall reached a maximum drag reduction rate 1.17% higher than that of the elastic wall under the same condition.The thermally conductive elastic wall had two mechanisms.First,the elasticity deformation increased the boundary layer thickness and decreased the velocity gradient,reducing the shear force.Second,the heat produced by the elastic deformation of the thermally conductive elastic wall was conducted at the boundary layer and decreased the viscosity,resulting in drag reduction.The thermally conductive elastic wall should delay the aging process and increase the service life of fluid machinery.