Author:
Zhou Yanling,Fan Jun,Wang Bin
Abstract
Observation of the backscattering form function for a solid polymethylmeth-acrylate(PMMA) sphere reveals a significant enhancement at low frequencies, which is associated with the subsonic Rayleigh waves resonance. The presence of these resonances suggests that solid PMMA spheres may be used as passive sonar targets for certain applications.The slightly deformed PMMA spheres with regular corrugation are constructed for studying and manipulating the low-frequency resonances of subsonic Rayleigh waves. For the regular-corrugated PMMA spheres, the first-order approximate of Rayleigh normal mode solution is obtained with the perturbation method and the backscattering form function is analyzed in each order. It can be found that coupling among multiple resonance modes is introduced by the boundary deformation and leads to the shift of resonance frequency. An approximate formula for the frequency shift with respect to the parameters of corrugated boundary is deduced. Based on this formula, it is possible to evaluate resonance frequency of subsonic Rayleigh waves quickly and then manipulate acoustic scattering filed of the slightly deformed PMMA spheres in water passively.