Simulation Of Porous Airfoils Acoustics Based On LBM-LES Method And The Noise Reduction Mechanism

As people pay more and more attention to noise pollution,more and more attention has been paid to the noise reduction of rotating machinery and aircraft.In recent years,more and more researches have been done on the noise reduction of airfoil using porous media.Experiments also show that the noise reduction has a good effect,but the noise reduction mechanism needs further research.The calculation method of aerodynamic noise of direct numerical understanding and reducing medium Reynolds number of Aircraft Fuselage Aerodynamic noise is crucial,however,by solving the compressible Navier-Stokes equations(N-S)and the flow field and the far field direct calculation method of noise are restricted in low Maher number conditions.The LBM-LES method combined with Lattice Boltzmann Method(LBM)and Large Eddy Simulation(LES)can simulate numerically the high Reynolds number flow and aerodynamic noise in a relatively high parallel efficiency.Use the LBM-LES method of SD-7003 airfoil at Reynolds number 8.0e5 and Maher number 0.147 under the condition of aerodynamic noise of direct numerical calculation,LBM method based on the multiple relaxation time approximation,the lattice discrete velocity model for the D2Q9 model;LES method using dynamic Smagorinsky subgrid model.The simulation result of solid and porous airfoil match with the experiment result showing the LBM-LES method has good accuracy.Based on the influence of porous media on noise and flow field,4 kinds of porous materials with different flow resistance are used to explore the noise reduction principle of porous airfoil and to find that different material has different noise reduction frequency in order to reveal the mechanism of the noise reduction.Result shows that by using porous material the air flows in and out from the pressure side and suction side,which reduce the pressure fluctuation and the noise source.That is why the OSPL reduce by adding porous material and the high resistance porous has a good reduction in middle frequency and the low resistance porous material has a good reduction in high frequency.