Numerical and experimental analysis of second-order effects and loss mechanisms in axisymmetrical cavities

Abstract

This paper deals with the analysis of finite amplitude acoustic waves in three-dimensional resonant cavities. A specific finite element model is proposed which includes: ͑i͒ the pressure field nonlinearity using a perturbative method; ͑ii͒ the loss mechanisms using an experimentally determined effective bulk attenuation or modeling viscous and thermal losses at the walls and acoustic radiation through the aperture with complex impedances. An axisymmetrical cavity with transversal dimension larger than the wavelength has been experimentally studied. The acoustic field is generated by a high-power flexurally vibrating transducer which generates high pressures. Measurements are performed for the fundamental and second-order pressure components for several cavity resonance modes. An important standard deviation is observed. Experimental data are compared to predicted pressure field distributions. Numerical models describe the pressure distribution correctly but overestimate the amplitude.

Numerical and experimental analysis of strongly nonlinear standing acoustic waves in axisymmetric cavities

“…The classical article of Coppens and Sanders [9], dealing with three-dimensional cavities, as the more recent [10], dealing with axisymmetric cavities, pointed out the difficulties of this type of experiments, in particular due to losses evaluation and degeneracies.…”

“…The attenuation of the resonator at the studied mode is experimentally evaluated by measuring the ''spatial quality factor'' [10]. The narrow band of the transducer makes impossible to sweep the frequency to obtain the quality factor of the chamber [9].…”

“…Refs. [9,10] present experimental analysis and perturbation models of complicated modes in realistic cavities. The model in Ref.…”

“…It has to be noted that the 0041 perturbation methods developed in Refs. [9,10] are limited to quasi-linear waves. Recently, the time domain simulation of the behaviour of nonlinear waves inside two-dimensional resonators at complicated modes has been published [12].…”

“…Ref. [10] deals with a second order perturbation model based on the finite element method. An axisymmetric cavity is experimentally analyzed in this reference.…”