| With the widely application of the ultrasonic nondestructive testing technology,the research of the ultrasonic propagation characteristics provides the conditions with which ultrasound can be widely applied.In this paper, we use traditional FDTD and improved FDTD method. Firstly, we use traditional FDTD method, we establish the two-dimensional elastic solid of second-order and fourth-order difference FDTD sound field equation, we use the algorithm of PML boundary absorption to absorb the border,so that the limited border can take place of infinite space. In order to prove the fourth-order index difference FDTD method is more effective, it simulates for second-order and fourth-order index difference FDTD equations under the environment of Microsoft Visual Studio. After comparing simulation, simulation result of fourth-order index difference FDTD method is more stable and less volatile, but simulation time of fourth-order index difference FDTD method is longer. It shows that simulation accuracy of the fourth order index difference FDTD algorithm is higher.What’s more, in view of the traditional FDTD, the second-order approximate difference in the space but lower calculation precision, four-order approximate difference in the space to ensure higher calculation precision but longer the simulation time. In order to improve difference scheme in the space, a new difference method,namely compact difference schemes, has been proposed; then the compact difference scheme based on the discrete form of acoustic wave equation is proposed in detail, and analysis the numerical stability of improved FDTD method; compared with the compact difference scheme and the high-order compact difference scheme equation of the FDTD method. The simulation results show that the compact FDTD method than the traditional FDTD method reduces the simulation time, high- order compact scheme FDTD method is an effective method to improve the calculation accuracy and calculation speed. |
