Numerical Study Of Bionic Non-smooth Surface For Drag Reduction

With the gradual improvement of human environmental awareness,energy conservation and low-carbon environmental protection have become the common goals of mankind.Therefore,in the field of industrial development today,research on drag reduction technology has become the key to reducing energy consumption.Among the many drag reduction technologies,the bionic groove drag reduction technology has been widely used in many fields such as aerospace,oil pipeline transportation,sports competition and marine transportation due to its advantages of low cost,easy implementation,and outstanding effects.Therefore,the bionic trench drag reduction technology has very high research significance and practical application value.The paper first summarizes several typical drag reduction technologies at home and abroad.For example,a variety of drag reduction technologies such as groove surface drag reduction technology,pit convex hull drag reduction,etc.,and the bionic groove surface reduction technology are discussed.The resistance technology was highlighted.Then,it briefly introduces the concept of boundary layer and related theoretical knowledge of turbulent burst near the wall.Taking the shark skin microstructure and desert landform as bionic objects,the thesis established V-shaped,L-shaped,U-shaped and n-shaped longitudinal groove surface models,and V-shaped,U-shaped,semi-circular transverse groove surface models,and then used the ICEM CFD software performs grid division and boundary condition naming,and finally sets the calculation domain boundary conditions,numerical calculation,and post-processing through Fluent software.For the two groove surface models arranged longitudinally and laterally,the paper analyzes the influence characteristics of the groove wall on the resistance from the perspectives of surface shear stress,flow field velocity,flow field flow characteristics,etc.Through comparison,it is found that the groove surfaces of the two arrangement methods show a certain drag reduction effect on the smooth surface.For the groove surfaces arranged longitudinally,?1?at the same speed?U₀=6m/s?,The shear force and velocity clouds of the V-shaped,L-shaped,U-shaped and n-shaped micro grooves found that the drag reduction effect of the L-shaped groove is better than the other three structures,but the strength stability of the structure is considered,Select the surface of the V-shaped groove as the research object;?2?Within the speed range of 2?10m/s?when h=s=0.1mm?,the drag reduction effect of the surface of the V-shaped longitudinal groove first increases and then In the downward trend,when U₀=6m/s,the drag reduction rate reaches the maximum value?=3.268%,then,the drag reduction rate begins to decrease and eventually the phenomenon of increased resistance appears.?3?Through simulation,it is found that the"secondary vortex"at the peak of the longitudinal groove surface will increase the thickness of the viscous bottom layer and reduce the surface shear stress to achieve drag reduction.For the groove surfaces arranged in the lateral direction,?1?in the laterally distributed grooves,obvious vortices rotating clockwise and at a lower speed appear.These vortices will isolate the main flow in the flow field from the wall surface and play the role of rolling bearings.As a result,the frictional force will be changed from sliding friction to rolling friction to achieve drag reduction.?2?For the groove surfaces of different intervals,the differential pressure resistance and the viscous resistance on the surface are also different.When the groove spacing is too large,it will increase the resistance value.