Validation of Jet Noise Simulations and Resulting Insights of Acoustic Near Field

Abstract

A hybrid lattice Boltzmann method–very-large-eddy simulation (LBM-VLES) solver for high-speed nonisothermal subsonic flows is used to simulate the unsteady jet flow exhausting from a single axi-symmetric nozzle, as well as the associated noise spectra and directivity. The jet exit Mach number and temperature ratio are set according to three representative operating conditions from the NASA SMC000 experimental campaign. The farfield noise is computed through a Ffowcs Williams and Hawkings analogy applied to a fluid surface encompassing the jet plume. Both time- and frequency-domain formulations are used, the latter in combination with an azimuthal Fourier transform of the linear source terms to analyze the contribution of the different azimuthal components. A resolution study is carried out for both aerodynamic and acoustic results. The near- and far-field results confirm that the underlying flow features and noise mechanisms are fully represented by the numerical solution. A wavelet decomposition technique is applied to analyze the source mechanisms for a heated core case. This is achieved by separating the coherent flow motion from the chaotic perturbations in the turbulent flows. Finally, a frequencydomain integral formulation is used to analyze the acoustic far-field of the two segregated components.