Aeroacoustic Calculations of the 30P30N High-lift Airfoil using Hybrid RANS/LES methods: Modeling and Grid Resolution Effects

Abstract

This study presents several unsteady computations of the 30P30N three-element high-lift airfoil, focused on slat noise prediction. These simulations rely on several RANS/LES approaches: two global hybrid approaches, DDES (Delayed Detached Eddy Simulation) and ZDES (Zonal Detached Eddy Simulation) and one zonal approach, the NLDE (Non-Linear Disturbance Equations). Global approaches compute all the geometry, while zonal simulations only consider an LES domain clustered around the slat to save computational resources. Two grid resolutions are considered, in order to perform a critical comparison of both the modeling and grid resolution effects for this kind of configuration. The obtained results are favorably compared to near-field results measurements obtained in JAXA low-speed Wind Tunnel (JAXA-LWT2): narrow band peaks present in the pressure spectra are well recovered by all the simulations, with a very good agreement with the measurements for the fine grid results, while the medium grid simulations tend to over-estimate the magnitude of these peaks. It is also observed that the DDES approach seems to delay the development of instabilities in the slat cusp shear layer, while other approaches lead to a faster break-up of the shear layer. The zonal NLDE approach leads to significant CPU time savings due to the reduced number of grid points, as well as to shorter transient times. However, such simulations do not account for the whole diffraction and reflection effects, as observed on the far-field acoustic field.