脉冲磁激励的磁声效应和热声效应的仿真研究

Simulation research on magnetoacoustic effect and thermoacoustic effect of pulsed magnetic excitation

我们根据电磁场辐照低电导率样本时电磁场和声波场之间的耦合关系,对脉冲磁激励的磁声效应和热声效应展开研究。本文基于电磁场理论和声波传播理论知识,推导了脉冲磁激励的声压波动方程;构建二维载流线圈和低电导率圆形薄片模型以模拟成像物理环境,利用有限元方法分析瞬态电磁场;并且根据电磁场仿真结果,进行磁声效应和热声效应所产生的声场仿真计算。仿真结果表明,微秒级高斯脉冲磁场激励下,低电导率样本中热声效应比磁声效应大,且起主要作用;微秒级高斯脉冲磁场和0.2 T静磁场激励下,低电导率样本中热声效应和磁声效应共存。该研究为感应式磁声成像和磁热声成像的进一步应用奠定了基础。

According to the coupling relationship of electromagnetic field and acoustic field when electromagnetic field irradiates low conductivity objects, we carried out a study on the magnetoacoustic effect and thermoacoustic effect in pulsed magnetic excitation. In this paper, we provide the pressure wave equation in pulsed magnetic excitation based on the theory of electromagnetic field and acoustic wave propagation. A 2-dimensional coil carrying current and a circular thin sheet model were constructed to simulate the physical imaging environment. The transient electromagnetic field was simulated using finite element method. Numerical studies were conducted to simulate the pressures excited by magnetoacoustic effect and thermoacoustic effect according to the result of electromagnetic simulation. It was shown that the thermoacoustic effect played a leading role in the low conductivity objects on the microsecond Gauss pulsed magnetic excitation, and thermoacoustic effect and magnetoacoustic effect coexisted on the microsecond Gauss pulsed magnetic field and 0.2 T static magnetic field excitation. This study lays the foundation for the further application of magnetoacoustic tomography with magnetic induction and magnetically mediated thermoacoustic imaging.