A Study on Pressure Wave Emitted from Transonic Pulsating Jet

Abstract

A pulsating flow through a pipe and the jet discharged from the pipe end were numerically simulated. The mechanism of pressure wave radiation from the transonic pulsating jet was examined. Noise emanates from a jet issuing from an exhaust pipe of automotive engines and reciprocating compressors. The jet is unsteady and has some sources of noise such as the jet itself, shock wave and the interaction between shock and vortex, etc. The present study focuses on the mechanism of noise generation, in particular the noise caused by the shock-vortex interaction. The Random-Choice Method was employed for the calculation of the flow field in the pipe and the TVD scheme was used for the flow field downstream of the pipe end. The flow fields with the pulsation at the different frequencies were examined. The numerical results are compared with Schlieren pictures obtained by the experiment. The behavior of the small vortex formed along the jet boundary and the formation of shock in the vortex are found to be closely related to the pressure wave emitted from the transonic pulsating jet.