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

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: (i) the pressure field nonlinearity using a perturbative method; (ii) 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.