Numerical investigation of the noise source locations of supersonic jets using the beamformed method

A numerical study is presented of the noise source distributions of supersonic jets from military style nozzles. The beamformed method is used for noise source location based on the acoustic pressures predicted on a virtual microphone array. To perform the predictions, a hybrid method combining unsteady CFD and the acoustic analogy is used for the jet noise simulations. A modified version of the Detached Eddy Simulation (DES) approach is solved with a fourth order DRP scheme based on a multi-block structured mesh to capture the unsteady turbulent noise sources. Noise predictions are made with the permeable surface Ffowcs Williams and Hawkings (FWH) solution. A good agreement of the predicted noise spectra with the acoustic measurements is found to reach St ≈ 3.0. It is observed that an over-prediction of the noise source levels occurs at some angles in the mid- to high-frequency range. The auto spectrum of the acoustic pressures gives the characteristics of the noise source distributions associated with different scales of the turbulent eddies at the focus of the microphone array. Comparisons are made with the experimental measurements of peak-noise source locations at similar operating conditions. The predicted source locations are in good agreement with measurements for an unheated jet case. However, poorer agreement is obtained for a heated jet. The possible reasons for this discrepancy are discussed.