Turbulence Noise of Slat Trailing Edge Controlled by Porous Material

Abstract

The utilization of porous materials is regarded as an effective strategy for mitigating aerodynamic noise at the trailing edge. In this study, a two-step computational fluid mechanics/computational aeroacoustics (CFD/CAA) hybrid method was employed to evaluate the noise impact of porous materials located at the trailing edge of high-lift slats. The turbulence field variable information was extracted from steady-state volume-averaged Navier-Stokes (VANS) equations using a spatial filter model based on Euler discretization, which generated turbulence velocity and determined the broadband noise source term. The linear Euler equation (LEE) with a source term was utilized to compute sound wave propagation in the fluid region, while the volume-averaged linearized Euler equation (VALEE) was applied for sound wave propagation in the porous region. Prior to conducting calculations and analyses, we validated our self-developed solver’s flow field computations in porous media against commercial software Fluent. Subsequently, verification of our method’s accuracy involved comparing synthetic turbulence velocities generated by the spatial filter model with two-point intercorrelation data from two-dimensional uniform and inhomogeneous artificial turbulence. Finally, we confirmed the applicability of Darcy terms and Forchheimer terms for sound propagation in homogeneous and anisotropic porous media as part of our study. Based on the establishment of an effective numerical model, the flow field and sound field of porous materials embedded at various positions within the slats were calculated and analyzed. The noise reduction effects of porous materials located in different areas exhibited significant variations. When the trailing edge of the slat was fully embedded with porous material, the turbulent kinetic energy at that location increased due to interactions between the porous material and the incoming shear layer airflow, leading to an increase in noise levels. Conversely, when only a portion of the tail edge of the slat was embedded with porous material, there was a notable reduction in slat noise; specifically, the sound pressure level (SPL) decreased by approximately 5 dB across most directions.