A numerical study is presented of an axisymmetric turbulent over-expanded Mach 2 jet. The time dependent characteristics of jet screech are modelled by a joint computational fluid dynamics and acoustic analogy approach. This study specifically addresses the unsteady aerodynamic pressure in the vicinity of the nozzle outlet, its jet instability feed-back role, and the related far-field screech noise. Unsteady aerodynamic predictions are obtained by solutions of the short-time averaged Navier-Stokes equations with turbulence closure. The second order accurate finite volume approach uses an approximate Riemann method and explicit multi-step Runge-Kutta time integration. The time advancing aerodynamic predictions are the data base for the application of the Lighthill acoustic analogy to estimate the far-field noise. A large-scale shear layer instability and shock cell unsteadiness drive the aerodynamic field oscillations. This essentially inviscid instability is the main source of the predicted screech noise.
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