FDTD方法的改进及在超声波声场计算中的应用

时域有限差分法(FDTD, Finite Difference Time Domain)是建立超声检测模型的有效手段,然而在相邻两种介质的分界面上,两种介质声阻抗的突变会引起差分计算的不稳定.为了解决上述问题,从常规FDTD方法入手,提出将界面两边介质的声学参数在界面处进行平均处理的方法,对FDTD方法进行了改进;然后分别采用常规FDTD方法和改进方法对相邻两种介质声阻抗相差5个数量级的模型进行了声场计算;最后对超声换能器进行了有限差分声场计算和实际检测实验对比.研究结果表明:改进的FDTD方法是超声波声场计算中一种有效可行的数值方法.

Improvement of finite difference time domain method and its application to calculation of ultrasonic sound fields

Finite difference time domain (FDTD) method is an effective way to establish ultrasonic testing model. However, a big difference between acoustic impedances of two adjacent materials may cause instability of the difference computation in the interface of two materials. To solve this problem, based on the conventional FDTD algorithm, an improved FDTD method was introduced by taking the average of the ultrasonic parameters of two materials on both sides of the interface. The model was built for the sound field calculation of the media consisted by two adjacent materials, one of which the acoustical impedance is five orders larger than the other, and the conventional and improved FDTD method were used respectively. Numerical calculation and practical experiments for an ultrasonic probe were accomplished. The results show that the improved FDTD method is a feasible and effective method for ultrasonic sound filed calculation.