A Two-Step Computational Aeroacoustics Method Applied to High-Speed Flows

This study numerically investigates the generated noise and perturbation fields from an excited high-speed jet flow (air), which is modeled by the linearized Euler equations. The mean flow is prescribed by experimental-analytical approach. Harmonic hydrodynamic excitation is applied at the nozzle exit to mimic a previous experimental setup, and to enhance the periodic component of the perturbation field. We investigate the propagation of this excitation in the pressure (acoustic), velocity, and density waves, looking at details that were not addressed in the experiments. We integrate the governing equations using the finite-difference method and a special scheme that is second-order accurate in time and fourth-order accurate in space. Alternating one-sided differences are implemented to eliminate spatial biases in the calculations. We use an appropriate set of boundary conditions that minimizes spurious reflections, including the characteristics-based Thompson inflow, acoustic radiation, Tam and Webb outflow, and centerline conditions. We investigate the characteristics of these waves, including the spatial growth and damping, and the noise radiation pattern.