Time-efficient simulations of fighter aircraft weapon bay

Abstract

A cavity flow exhibits aero-acoustic coupling between the separated shear layer and reflecting waves within the walls of the cavity, which leads to emergence of dominant modes. It is of primary importance that this flow mechanism inside the cavity is understood to provide insights and control the relevant parameters and that it can be properly predicted using state-of-the-art CFD tools. In this study, an open-cavity configuration with doors attached on the sides and a length-to-depth ratio of mathbf{5}.7 have been studied numerically using the TAU code developed by the German Aerospace Center for transonic flows with three simulation methods such as DES with wall functions and SST-SAS with resolved wall flow or wall function techniques. The free-stream conditions investigated are Mach number (Ma) mathbf{0}.8 with Reynolds number (Re) mathbf{12} times mathbf{10} ^mathbf{6 }. The Rossiter modes occurring in the cavity due to the acoustic feedback mechanism have been numerically computed and validated. The SST-SAS model is around 90% more computationally efficient compared to the hybrid RANS-LES model providing excellent accuracy in predicting the Rossiter modes. The SST-SAS model with wall functions is 50% more computationally efficient than wall-resolving SAS simulations showing good behaviour in predicting modal frequencies and shapes, with further scope for improvement in the spectral magnitude levels.