Detached-eddy simulation of shock unsteadiness in an overexpanded planar nozzle

This work investigates the self-excited shock-wave oscillations in a three-dimensional planar overexpanded nozzle turbulent flow by means of detached-eddy simulations. Time-resolved wall pressure measurements are used as primary diagnostics. The statistical analysis reveals that the shock unsteadiness has common features in terms of the standard deviation of the pressure fluctuations with other classical shock-wave/boundary-layer interactions, like compression ramps and incident shocks on a flat plate. The Fourier transform and the continuous wavelet transform are used to conduct the spectral analysis. The results of the former indicate that the pressure in the shock region is characterized by a broad low-frequency content, without any resonant tone. The wavelet analysis, which is well suited to study non stationary process, reveals that the pressure signal is characterized by an amplitude and a frequency modulation in time.