Spatial Stability of the Slab Jet. II. Numerical Simulations

Results of numerical simulations of a supersonic slab jet wiggled at different frequencies are presented and compared with the linearized spatial stability analysis performed in Paper I. Slabs with different densities and Mach numbers have been simulated. In general, results from the numerical simulations compare favorably with predictions of the linearized analysis. In all simulations the slab jet is disrupted by sinusoidal oscillation at or near the resonant wavelength of the fundamental sinusoidal mode, independent of the driving frequency. The jet then propagates behind a jet front and forms a lobe, and the jet flaps within the growing lobe. The sinusoidal oscillation approaches a wavelength corresponding to the driving frequency except when the driving frequency is much less than or significantly exceeds the resonant frequency. In addition to sinusoidal oscillation, the simulations also show weak oblique shock waves which cross the jet channel at about the Mach angle. These oblique shock waves can be identified with the first and second sinusoidal reflection modes predicted by the linearized analysis.