Photoacoustics in a Cylindrical Resonator Containing a Flowing Gas

Abstract

Adetailed study of photoacoustics in circular resonators and waveguides in the presence of agas flowispresented based on the Green'sfunction method. In the first part of the paper,awaveequation is deriveddescribing sound propagation in afl owing (perfect)g as due to al ocalized heating source. Analytical results are obtained for the acoustic pressure in the case of aconstant gasflow subject to different boundary conditions. In the second part of the paper,the derivedwaveequation is solved for aparabolic flowprofile using the finite-element method and results are compared with the constant-flowcase. It is demonstrated that the gas-flowprofile does not change the pattern of acoustic resonance frequencies significantly.Inparticular it is noted that the presence of flowgives rise to newpeaks and we showthat non-linearities with respect to the mean flowvelocity appear already at 1% of the speed of sound at certain frequencies. PACS no. 43.20.-f,43.58.-e ©S.Hirzel Verlag · EAA 797 ACTA ACUSTICA UNITED WITH ACUSTICA Willatzen et al.:P hotoacoustics in acylindrical resonator Vol. 96 (2010)