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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.
Finite Difference Time Domain (FDTD) is an effective method to establish the ultrasonic detection model. However, the discontinuity of the acoustic impedance of the two kinds of media can cause the difference calculation unstable at the interface between the two adjacent media. To solve the above problems, the FDTD method is improved based on the conventional FDTD method. The method of averaging the acoustic parameters of the media on both sides of the interface at the interface is proposed. Then the conventional FDTD method and the improved method are used respectively to measure the acoustic properties of two adjacent media Finally, the finite difference sound field calculation of the ultrasonic transducer is compared with the actual detection experiment.The results show that the improved FDTD method is an effective and feasible numerical method in the ultrasonic sound field calculation .