Numerical investigation of screech tones in 3-D modes by using an inviscid approach

Abstract

Screech tones from supersonic inviscid jet were numerically investigated using computational aeroacoustics methods. A fourth order optimized compact scheme and fourth order Runge-Kutta scheme were used to solve three dimensional Euler equations. The tool was validated at the conditions of two supersonic flows: one is a perfectly expanded jet, and the other is three under-expanded jets. Extensive analysis was performed to investigate the characteristics of two three-dimensional modes, known as B and C modes, of screech tones including two mode transitions for various Mach numbers from 1.2 to 1.9. The directivity of a B-mode screech is investigated with the spectra of a Mach 1.3 jet. The directivity of B-mode screech tones is similar to the directivity of an acoustic dipole, whereas the directivity of C-mode screech tones is close to the directivity of an acoustic monopole. The wavelengths and amplitude of the reproduced screech tones showed good agreement with other results. The azimuthal directivity of both B and C modes becomes asymmetric after the second mode transition. It can be concluded that the present inviscid tool can numerically reproduce the screech tone including its non-linear mode transition without considering a viscous effect.