A novel hybrid method for aerodynamic noise prediction of high-lift devices

Aerodynamic noise of High-Lift Devices (HLDs) is one of the main sources of airframe noise, and has immediate impacts on the airworthiness certification, environmental protection and security of commercial aircraft. In this study, a novel hybrid method is proposed for the aerodynamic noise prediction of HLD. A negative Spalart-Allmaras (S-A) turbulence model based Improved Delayed Detached Eddy Simulation (IDDES) method coupling with AFT-2017b transition model is developed, in order to elaborately simulate the complex flow field around the HLD and thus obtain the information of acoustic sources. A Farassat-Kirchhoff hybrid method is developed to filter the spurious noise sources caused by the vortex motions in solving the Ffowcs Williams-Hawkings (FW-H) equation with permeable integral surfaces, and accurately predict the far-field noise radiation of the HLD. The results of the 30P30N HLD indicate that, the computational Sound Pressure Levels (SPLs) obtained by the Farassat-Kirchhoff hybrid method conform well with the experimental ones in the spectrum for the given observation point, and are more accurate than those obtained by the Farassat 1A method. Based on the hybrid method, the acoustic directivity of the HLD of a commercial aircraft is obtained, and the variation of the SPLs in the spectrum with the deflection angle of the slat is analyzed.