Numerical Analysis Of Turbulent Flow And Aerodynamic Noise At Trailing Edge Of Three-dimensional Porous Media Bionic Airfoil

When the Reynolds number of porous airfoil based on bionics is in a certain range,turbulent noise will be generated at the trailing edge of the airfoil.The research on the turbulent flow and aerodynamic noise at the trailing edge of the bionic airfoil in porous media can further understand the effective mechanism of aerodynamic noise control of the bionic airfoil,and provide a theoretical basis for the control of aerodynamic noise of the aircraft.In this paper,Large Eddy Simulation（LES）is used to numerically study the trailing edge turbulent flow of Selig-Donovan（SD）7003 bionic airfoil with Reynolds number of8×10⁵ and inlet velocity U₀ of 50m/s.Seven porous airfoils with different permeability were designed.The far field aerodynamic noise of different bionic airfoil is numerically studied by finite element/infinite element method based on acoustic analogy theory.The turbulent flow at the trailing edge of the bionic airfoil has the following characteristics:the change of the surface pressure coefficient of the trailing edge of the porous airfoil causes the fluid to flow through the trailing edge of the porous medium,causing the aerodynamic load of the airfoil to fluctuate,and the amplitude of the fluctuation depends on the permeability of the porous media.The trailing edge of porous media material has a weak effect on the time-mean pressure distribution upstream of the airfoil,but decreases the time-mean pressure coefficient and pulsation pressure intensity near the trailing edge wall.The porous trailing edge changes the three-dimensional vortex structure and vorticity distribution near the trailing wall,and slows down the vortex fragmentation in the trailing edge region.The results show that the trailing edge aerodynamic noise of the airfoil can be suppressed by using porous media materials.The Over All Sound Pressure Level（OSPL）of the porous airfoil decreases first and then increases with the decrease of the permeability of the porous media,and the noise suppression effect is most significant when the permeability of the porous media is 5e^-11m².At the same time,it is found that the SPL of St between 2.35 and 9.4 at the monitoring point has the greatest contribution to the total SPL at the monitoring point,and its influence on noise is the same as the trend of the total SPL.The directional characteristics show that the dipole source is dominant in the low and middle frequency bands,while the quadrupole source is dominant in the high frequency bands.