脉冲与连续声源激发的 Scholte 波频散特性研究

Dispersion characteristics of Scholte waves excited by pulsed and continuous sound sources

摘要

浅海中声源激发的 Scholte 波频散及极化特性对于目标探测有着重要意义，当前对脉冲与连续点声源激发的 Scholte 波认识仍不够充分。分别运用简正波理论，时域有限元模型结合小波变换对这两种声源激发的 Scholte 波进行研究。首先基于浅海半无限弹性海底声场模型，利用简正波理论分析了 Scholte 波的频散特性，得出硬质海底和软质海底条件下 Scholte 波都存在频散现象。然后，利用时域有限元模型结合小波变换探究了脉冲与连续声源激发的 Scholte 波频散和质点运动轨迹的极化特性。结果表明，从时频分析看，两种声源在硬质海底时均可观察到 Scholte 波的频散现象。连续声源在软质海底时可观察到 Scholte 波的频散，但脉冲声源难以观察频散现象。从 Scholte 波极化特性看，脉冲声源激发的 Scholte 波椭圆率先减小后增大，连续声源下的椭圆率保持稳定；脉冲声源激发的 Scholte 波在硬质海底下以垂直振动为主；连续声源激发的 Scholte 波在硬质海底下以垂直振动为主，在软质海底下以水平振动为主。研究结果可为浅海中脉冲与连续声源的探测提供初步依据。

Abstract

The dispersion and polarization characteristics of Scholte waves excited by sound sources in shallow sea are of great significance for target detection. The Scholte waves excited by pulse and continuous point sound sources are still not well understood. The Scholte waves excited by these two sound sources are studied by using the theory of normal wave，the finite element model in time domain，and the wavelet transform. First，based on the semi-infinite elastic submarine sound field model in shallow sea，the dispersion characteristics of Scholte waves are analyzed by using the normal wave theory，and the dispersion phenomenon of Scholte waves exists in both hard and soft seabed conditions. Then，the time domain finite element model combined with wavelet transform is used to investigate the dispersion of Scholte waves and the polarization characteristics of particle motion trajectory excited by pulse and continuous sound source. The results show that the dispersion of Scholte waves can be observed when the two acoustic sources are in the hard seabed. The dispersion of Scholte waves can be observed for continuous sound sources in the soft seabed，but it is difficult for pulsed sound sources to observe the dispersion phenomenon. According to the polarization characteristics of Scholte waves，the ellipse of the waves excited by pulsed sound source decreases first and then increases，while the ellipticity of Scholte waves under continuous sound source remains stable. Scholte waves excited by pulsed sound source vibrate vertically under hard seafloor mainly. Those excited by continuous sound source mainly vibrate vertically under hard seafloor and horizontally under soft seafloor. The results can provide a preliminary basis for the detection of pulse and continuous sound sources in shallow sea.

关键词

Scholte 波 / 弹性海底 / 频散特性 / 极化特性 / 数值模拟

Key words

Scholte wave / elastic seafloor / dispersion property / polarization property / numerical simulation

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基金资助

国家自然科学基金资助项目(52201334)