Investigation of subharmonic generation by finite-amplitude waves in a rigid-walled tube

Abstract

Finite-amplitude standing waves contained within an air filled rigid-walled tube at ambient temperature and pressure were investigated experimentally. The pressure waveform in the tube was analyzed for subharmonic content for comparison with several existing theoretical models. Due to limitations of the experimental apparatus, the only model for which the predicted threshold for subharmonic generation could be exceeded was that of Coppens which predicts subharmonic generation when the strength parameter exceeds 2.0. Strength parameter is defined as M2BetaQ1 where M2 is the Mach number of the driving frequency, Beta = 1.2 in air, and Q1 is the quality facotr associated with the subharmonic resonance. Strength parameters up to 2.89 were investigated and no threshold effect was observed.