Transition of supersonic plane jet due to symmetric/antisymmetric unstable modes

Abstract

Results from viscous linear stability analysis are presented for plane jets with different convective Mach numbers (Mc). The convective Mach number characterizes the stability modes. It is found that the dominant mode is two-dimensional antisymmetric (A1) for Mc less than 0.8, three-dimensional antisymmetric (A1) for Mc larger than 0.8 and less than 1.5 and two-dimensional symmetric (S2) for Mc larger than 1.5. Two-dimensional spatially developing and three-dimensional temporally developing direct numerical simulations are performed using high-order compact schemes. The flow structures perturbed with various unstable modes and their sound fields are examined. Two-dimensional simulations for Mc = 1.55 and 1.17 indicate that two-dimensional A1 modes of supersonic phase velocity lead to noise radiation. The results of three-dimensional simulations, for Mc = 1.17, forced with the most unstable two-dimensional S2 mode, the supersonic two-dimensional A1 mode and a pair of oblique A1 modes show that the steep compression waves are generated and radiate away from the jet with the growth and decay of the wave amplitude of the supersonic phase two-dimensional A1 mode.

This article was chosen from Selected Proceedings of the Second International Symposium on Turbulence and Shear Flow Phenomena (KTH-Stockholm, 27-29 June 2001) ed E Lindborg, A Johansson, J Eaton, J Humphrey, N Kasagi, M Leschziner and M Sommer feld.