Numerical prediction of supersonic jet screech frequency

Screech frequency is predicted using three different approaches, which make use of different quantities measured from the same computed flow field. The three different approaches are based on shock cell spacing in the imperfectly expanded supersonic jet, the wavelength of standing wave formed at the edge of the shear layer due to interference between downstream propagating hydrodynamic instabilities and upstream propagating acoustic waves, and from a spectral analysis of near-field pressure fluctuations. The computed flowfield for underexpanded and overexpanded axisymmetric screeching jets are obtained by solving the unsteady Navier-Stokes equations using a higher order Weighted Essentially Non-Oscillatory (WENO) discretization along with a subgrid scale Large-Eddy Simulation (LES) model.