Unsteady RANS simulation of turbulent flow over a weapon-bay cavity
Publish date: 2006-01-01
Report number: FOI-R--1983--SE
Written in: English
The unsteady turbulent flow over a weapon-bay cavity configuration was numerically investigated. The rectangular cavity has an aspect ratio of 5 : 1 : 1, which is configured to model an embedded weapon-bay geometry of military aircraft in a freestream with a Mach number of M? = 0.85. The turbulent cavity flow was modelled with the Spalart-Allmaras RANS model based on the unstructured CFD solver EDGE. The result was focused on the surface pressure fluctuations and resulting sound resonance from the cavity due to unsteady pressure oscillations, for which experiment was conducted by QinetiQ and had been used in this work for comparison. The RANS-computed flow features arising within the cavity were also analyzed, and the mean flow was compared with a well-resolved large eddy simulation. As compared with experimental data, the prediction of the pressure-induced tonal modes (for both the tonal frequency and magnitude) was significantly improved over previous 2D URANS computations. It was shown that the URANS simulation is able to produce reasonable simulations, in particular, for the amplitude of the second pressure mode and the frequency of the third mode in the analysis of the sound resonance radiated from the cavity. The predicted mean flow was shown in reasonable agreement with the LES data, but the velocity in the inner edge of the shear layer next to the recirculation was somewhat underestimated in the rear part of the cavity.