Effects of asymmetric helical modes combination on transitional structure in a supersonic jet

Abstract

The three-dimensional compressible Navier-Stokes equations are numerically solved to study the transitional structure and the resultant acoustic emission in a supersonic round jet at high convective Mach numbers. Numerical results for the convective Mach number M_c = 1.00 (M_j=2.0) and Re_r0=2000 based on the jet nozzle radius r0 are presented. Five cases of inlet disturbance for Mach number M_j=2.0 are presented. The first case is the jet flow forced randomly. The second case is the jet forced by a pair of unstable helical modes (m=1, 2, 3) with different azimuthal wave number. The numerical results show that the jet potential core region is reduced in the jet forced by a pair helical modes. Additionally, the weak Mach wave radiation was observed in the jet forced by a pair of helical modes with low phase velocity.