MTF与隐式有限元结合的数值模拟效果

Numerical Simulation Results of MTF Combined with Implicit Finite Element Method

多次透射公式(multi-transmitting formula,MTF)是一种应用性较广的局部人工边界条件,对于求解近场波动问题中的波源问题,MTF与隐式有限元相结合,波源振动是以集中荷载的方式施加在计算模型中间地表面上的一个作用点处。采用简单的空间内插方法实现高阶MTF。最后通过有限元数值模拟实验比较和讨论高阶与低阶透射边界数值结果的精度和稳定性。结果表明:对于一阶MTF,数值结果不易发生振荡失稳和漂移失稳;二阶、三阶、四阶MTF,数值模拟的结果易发生漂移失稳和振荡失稳,且随着N的增大,数值模拟的结果精确度越高,N越大,振荡失稳和漂移失稳出现的越早,失稳的程度越厉害,需要相应的抑制参数值也越大。

The multiple transmission formula is a widely used local artificial boundary condition.For solving the wave source problem in near-field wave propagation,MTF is combined with implicit finite element method.By means of concentrated load,the force is applied on the surface of the middle surface of the calculation model.A simple spatial interpolation method is used to realize high-order transmission boundary.Finally,the accuracy and stability of numerical results of high-order and low-order transmission boundary are compared and discussed through finite element numerical simulation experiments.The results show that for the first order MTF,the numerical results are not easy to cause oscillation instability and drift instability;for the second,third and fourth order MTF,the numerical results are prone to drift instability and oscillation instability,and with the increase of N,the higher the accuracy of numerical simulation results,the larger the N,the earlier the oscillation instability and drift instability appear,the more serious the instability is,and the corresponding suppression parameters are needed.The higher the value.