Flow and Noise Predictions for Single and Dual-Stream Beveled Nozzles

Numerical simulations of the flowfield and noise of single and staggered dual, round, and beveled nozzles are carried out, with the goal of gaining insights into the flow features that are responsible for noise generation and mitigation, and ultimately arriving at better designs. For aircraft applications, the geometry of the nozzles must be satisfactory both for aerodynamic and acoustic performance. The importance of taking the nozzle internal flow into account in the simulations instead of using simple inflow profiles, especially for complex geometries of current interest, is emphasized. A two-step Reynolds-averaged Navier-Stokes/large-eddy simulation methodology is developed and applied to several nozzle geometries allowing a new level of complexity in the geometry. The predictions of the gross thrust measures by Reynolds-averaged Navier-Stokes computations are in very good agreement with experimental measurements. The spectral predictions from large-eddy simulation are also in good agreement with measured data, for a wide range of jet conditions. The measured azimuthal variations in the noise field from beveled nozzles are reproduced by large-eddy simulation. The spectra from dual-stream nozzles are also well predicted. Preliminary efforts at establishing the link between flow and noise are presented. The interpretation of the flow/noise connection is not straightforward and is a big challenge; it is far from clear how one can establish cause and effect. The ability to relate changes in flow to noise may remain an open issue for the foreseeable future.