Digital Filter-based Turbulent Inflow Generation for Jet Aeroacoustics on Non-Uniform Structured Grids

Inclusion of the nozzle geometry with a turbulent inflow boundary condition is essential for realistic jet noise simulations. In the current study, a digital filter-based turbulent inflow condition, extended in a new way to non-uniform curvilinear grids, is implemented to achieve this. The proposed method has several key features desirable for jet noise simulations, with some limitations. To validate the method, a quasi-incompressible zeropressure-gradient flat plate turbulent boundary layer is simulated at a high Reynolds number. The boundary layer produced by the current method is shown to agree reasonably well with theory and a recycling-based turbulence injection method. The length of the adjustment region necessary for synthetic inlet turbulence to recover from modeling errors is estimated. A low Reynolds number wall-resolved jet simulation including a round nozzle geometry is performed. The method is shown to be effective in producing sustained turbulence on a non-uniform, non-Cartesian grid at a barely turbulent Reynolds number. The effect of variation of the inlet integral length scales on the recovery of turbulent fluctuations is studied and recommendations are made for choosing these parameters. A possible spurious noise source is identified near the turbulent inlet for the current method. It is shown that this spurious noise does not affect the acoustic field outside of the jet significantly, though it is recommended to attenuate this noise artificially by using a sponge zone.