Study On The Drag Reduction And Airfoil Lift Increasing Effect Of Gas Permeable Shell In Air

The power of vehicles such as cars,high-speed rail and other objects running at high speed in the air is mainly used to overcome the air resistance,so reducing the air resistance of moving objects is of great significance for energy conservation and emission reduction.For the aircraft,increasing the lift means more transportation,so improving the lift of the aircraft wing can improve the travel economy.In this paper,wind tunnel tests are carried out to study the air film drag reduction effect of the cylinder and cone-shaped porous shell models and the air film lift increase effect of the wing shaped porous shell model.The effect of the air film on the flow field near the moving object wall is studied by CFD.In this paper,the porous stainless steel material is made of multi-layer stainless steel wire mesh by pressing,rolling and sintering.According to the test requirements and test conditions,the structure and size of the test section and pressure vessel of the test tunnel are designed.The simulation calculation and test research are carried out on the venting characteristics of the test tunnel.The results show that the wind speed of the wind tunnel designed in this paper is large and the venting time of the pressure vessel can meet the test requirements.The porous stainless steel plate is made into the wall of the porous shell of the test model.In this paper,the wind tunnel test is carried out to study the effect of the film drag reduction of the shell model of the cylinder and the shell model of the cone.The results show that the air resistance of the model can be significantly reduced by the air film permeated from the surface of the test model.With the increase of the infiltration speed of the model surface and the decrease of the main flow speed,the air resistance of the model can be significantly reduced and the effect of air film drag reduction will be enhanced.Aiming at the problem of reducing the pressure difference resistance of moving objects,this paper studies how to install a dome at the end of the cylinder model,so as to reduce the air resistance of the test model and improve the effect of air film drag reduction.The air film drag reduction ratio of the cylinder and cone test models is 19.74% and 23.33% respectively.When the air film permeated from the lower surface of the airfoil shell model,the lift of the airfoil model will be greatly improved.Keeping the main flow velocity constant,when the pressure in the air cavity of the airfoil model increases from 0.02 MPa to 0.1MPa,the lift of the airfoil model will increase from 18.33% to 44.57%.The results show that the increasing effect of the wing model is obviously improved by increasing the gas permeation velocity on the lower surface of the wing.Finally,the air resistance of the test model is simulated.The results show that the difference between the numerical simulation results and the test results is not significant,which verifies the reliability of the numerical simulation.Through numerical simulation,the influence of air film permeated from micropores on the flow field near the wall of the model is studied.The results show that the low velocity gas film permeated by micropores can reduce the wall friction resistance.Keeping the main flow velocity to be 50m/s constant,when the seepage velocity of micropores increases from 1m/s to 7m/s,the maximum drag reduction rate of wall friction increases from 19.3% to 82%.The results also show that the low-speed fluid permeated from the micropores will reduce the pressure near the micropores.The low-speed fluid permeated from the micropores will change the velocity structure of the flow field near the wall and the thickness of the boundary layer near the wall will be increased obviously.