Numerical modeling of finite-amplitude sound beams: Shock formation in the near field of a cw plane piston source
Numerical modeling of finite-amplitude sound beams: Shock formation in the near field of a cw plane piston source
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DOI：
10.1121/1.1369097
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发表时间：
2001-07-01
影响因子：
2.4
通讯作者：
Cathignol, D
中科院分区：
文献类型：
--
作者：
Khokhlova, VA;Souchon, R;Cathignol, D
提出了描述水中强连续波源辐射的非线性声波束的两个理论模型和相应的数值编码。在第一个模型中，使用瑞利积分包括衍射效应，而非线性和热粘性吸收则在准平面近似中考虑。利用先前开发的用于在具有任意频率依赖吸收的介质中进行单脉冲传播的代码在时域内进行模拟。第二个模型是基于Khokhlov-Zabolotskaya-Kuznetsov方程，它与第一个模型相反，在抛物线近似中解释了衍射。仿真是在频域使用一种新的算法已经开发。为了提高计算速度，算法中采用了随波谱非线性展宽而变化的谐波数。为了验证这两个程序的正确性和有效性，对水中强超声圆形活塞源的近场衍射和非线性效应进行了模拟。将两种规范的模拟结果进行了比较，并与已知的实验数据进行了比较，结果吻合较好。然后使用频域代码详细研究强非线性传播机制，当冲击在靠近震源的波形中发展时。结果表明，衍射在激波形成过程中起着重要作用。预测了每个周期中两次冲击的发展及其进一步碰撞。研究还表明，与线性传播情况下的最大值相比，非线性传播和激波形成在峰值正压的两倍以上的距离上发生。通过与无衍射平面波传播强度的比较，研究了由冲击形成的光束总功率衰减随传播距离的变化规律。结果表明，光束的非线性能量衰减开始较早，但随着距离的增加衰减较慢。(C) 2001美国声学学会。
Two theoretical models and the corresponding numerical codes for the description of nonlinear acoustic beams radiated from intense cw sources in water are presented. In the first model, diffraction effects are included using the Rayleigh integral, whereas nonlinearity and thermoviscous absorption are accounted for in a quasi-plane approximation. The simulations are performed in the time domain using the code previously developed for single-pulse propagation in medium having arbitrary frequency-dependent absorption. The second model is based on the Khokhlov-Zabolotskaya-Kuznetsov equation, which, contrary to the first model, accounts for diffraction in the parabolic approximation. The simulations are performed in the frequency domain using a novel algorithm that has been developed. A variable number of harmonics, which follows the nonlinear broadening of the wave spectrum are employed in the algorithm to speed up calculations. In order to prove the validity and the accuracy of the two codes developed, the simulation of diffraction and nonlinear effects in the near field of an intense ultrasound circular piston source in water is performed. The results of modeling obtained by both codes are compared with each other and with known experimental data, and are found to be in a good agreement. Frequency-domain code is then used for detailed study of the strongly nonlinear regime of propagation, when shocks are developed in the waveform close to the source. It is demonstrated that diffraction plays a major role in shock formation. Development of two shocks in each cycle and their further collision is predicted. It is also shown that nonlinear propagation and shock formation result at some distance in the two times excess of peak positive pressure in comparison with the maximum value obtained in the case of linear propagation. The beam total power decay due to formation of shocks as a function of the propagation distance is compared with the intensity in a plane wave propagation without diffraction. It is shown that nonlinear energy decay starts earlier for the beam, but decreases slower over longer distances. (C) 2001 Acoustical Society of America.