Acoustic energy generation of “air-jet” instruments: Energy transfer between jet oscillation and acoustic field

Abstract

In this talk, we discuss how to estimate the acoustic energy generation of “air-jet” instruments with numerical simulation. To attack this problem, we use Howe’s energy corollary, with which we can estimate energy transfer between unsteady flow, i.e., oscillating jet and acoustic field. To calculate Howe’s formula, we need solenoidal velocity of the flow and its vorticity together with acoustic particle velocity separated from the whole velocity of compressible fluid. Recently, a method, which allows us to approximately calculate Howe’s formula, was developed in experiments by Bamberger and Yoshikawa et al., and it can be applied for the numerical calculation. We apply the method for the numerical calculation of a flue organ pipe model. We also introduce a toy model of the oscillating jet to investigate the mechanism of sound generation from the oscillating jet in detail. The acoustic energy is mainly generated in the downstream of the oscillating jet near the edge of the mouth opening, but it is consumed in the upstream near the flue exit to synchronize the jet motion with it. Our results are in good agreement with the experimental result by Yoshikawa et al. as well as Howe’s theoretical prediction.