Cavity flow noise predictions

Description/Abstract

The near and far pressure fields of three-dimensional turbulent cavity flow are studied by time-accurate simulations coupled with aeroacoustic predictions. A large-eddy simulation (LES) method is applied to a cavity with a 5:1:1 length to depth to width ratio at high Reynolds number (6.8 million based on cavity length) and compared with experiment. A good agreement is found for Rossiter mode amplitudes for all but the first mode, a finding that is in agreement with other numerical simulations. A detached eddy simulation (DES) is carried out at a lower Reynolds number of 45000. For the DES simulation, results from both coarse and fine grids have no obvious differences, suggesting that a grid of one million cells is sufficient. A low-storage Ffowcs Williams-Hawkings (FW-H) solver for far field noise prediction is validated fro both closed and open integration surfaces. For three-dimensional calculations it is found that spanwise integration lengths of a least 20 cavity depths give the most accurate far field predictions. For the high Reynolds number cavity peak radiation is found in the range of 57-60 degrees (with angles measured relative to the upstream direction). For the lower Reynolds number cavity both fine and coarse grid cases predict a peak radiation angle of 54 degrees. Noise attenuation is studied by placing a liner on the inner cavity walls. It is found that liners have a positive effect for the broadband noise reduction. Optimum noise reduction is found with complete coverage of the cavity floor and walls.