An analysis of flow and screech tone from supersonic axisymmetric jet at the initial stage

The screech tone from jet Mach number 1.18 is numerically calculated from the initial stage. A fourth-order optimized compact scheme and fourth-order Runge-Kutta method are used to solve the 2D axisymmetric Euler equation. Pulse jet problem with Mach number 1.56 is solved to validate the present method. Not only two important components of generating screech tones, shock cell structure and vortices, but also the transient behavior of the screech tone are investigated at the initial stage. Additional time is necessary to generate periodic screech tone after formation of shock cell structures. As time goes on, the location of the vortex generation becomes fixed near the nozzle exit, which is farther downstream initially, and the screech tone becomes periodic. The FFT results of three different periods are compared. It is observed that the component of lower frequency is dominant at the beginning, and the component of the screech tone becomes dominant as time increases. It can be concluded that the screech tones can be also numerically reproduced at the initial stage with the present inviscid method.