Acoustic nonlinearities and power losses at orifices

Abstract

Acoustic power losses occur when high-amplitude sound waves impinge on an orifice in the absence of mean flow. Described is a simple theoretical model of these losses, in which a harmonic, linear acoustic field is coupled to a nonlinear hydrodynamic flowfield at the orifice. Experimental and theoretical data on power losses at orifices with both pc and flanged acoustic terminations are compared, and fairly good agreement is noted. The structure of the flowfield in the neighborhood of the orifice is broadly described and some quantitative comparisons are made between the measured translational velocity of the ring vortices shed from both sides of the orifice and theoretical predictions. Again, the theory is seen to give generally reasonable results.