Cox B T, Beard P C
Department of Medical Physics and Bioengineering, University College London, Gower Street, London WCIE 6BT, United Kingdom.
J Acoust Soc Am. 2005 Jun;117(6):3616-27. doi: 10.1121/1.1920227.
Two related numerical models that calculate the time-dependent pressure field radiated by an arbitrary photoacoustic source in a fluid, such as that generated by the absorption of a short laser pulse, are presented. Frequency-wavenumber (k-space) implementations have been used to produce fast and accurate predictions. Model I calculates the field everywhere at any instant of time, and is useful for visualizing the three-dimensional evolution of the wave field. Model II calculates pressure time series for points on a straight line or plane and is therefore useful for simulating array measurements. By mapping the vertical wavenumber spectrum directly to frequency, this model can calculate time series up to 50 times faster than current numerical models of photoacoustic propagation. As the propagating and evanescent parts of the field are calculated separately, model II can be used to calculate far- and near-field radiation patterns. Also, it can readily be adapted to calculate the velocity potential and thus particle velocity and acoustic intensity vectors. Both models exploit the efficiency of the fast Fourier transform, and can include the frequency-dependent directional response of an acoustic detector straightforwardly. The models were verified by comparison with a known analytic solution and a slower, but well-understood, numerical model.
本文提出了两个相关的数值模型，用于计算流体中任意光声源辐射的随时间变化的压力场，例如短激光脉冲吸收所产生的压力场。频率 - 波数（k 空间）实现方式已被用于进行快速且准确的预测。模型 I 可计算任意时刻空间中任意位置的场，有助于可视化波场的三维演化。模型 II 计算直线或平面上各点的压力时间序列，因此可用于模拟阵列测量。通过将垂直波数谱直接映射到频率，该模型计算时间序列的速度比当前光声传播数值模型快 50 倍。由于场的传播部分和倏逝部分是分别计算的，模型 II 可用于计算远场和近场辐射方向图。此外，它可以很容易地用于计算速度势，进而计算粒子速度和声强矢量。这两个模型都利用了快速傅里叶变换的效率，并且可以直接包含声学探测器的频率相关方向响应。通过与已知解析解以及一个较慢但理解良好的数值模型进行比较，对这些模型进行了验证。
