Numerical simulation of flow-excited cavity tones

Abstract

The objective was to develop a numerical model for investigating the effect of obstructions in the opening on the frequency and amplitude of flow-excited cavity pressure fluctuations. A hybrid Reynolds-averaged Navier–Stokes/large eddy simulation (RANS/LES) method was used. The RANS/LES method ensures that important turbulence scales outside of the boundary layer are resolved, while permitting more economical RANS modeling of the smaller turbulent scales immediately adjacent to walls. Solutions were obtained at the speed where the cavity Helmholtz resonance was excited and at a speed well below resonance. A solution was also obtained where the cavity opening was partially obstructed. Results were compared to experimental data obtained for the same configuration. In all cases, the frequency of the shear layer oscillations was accurately predicted. Resonant cases also showed excellent agreement on the amplitude of the first harmonic. Some initial difficulties in predicting the amplitude in the nonresonant case are attributed to excessive dissipation in the LES calculations. Nonresonant cases are being resimulated using a less dissipative advective scheme and SGS turbulence model. A comparison of some flow field results showed reasonable agreement in certain cases.