看那本《从入门到精通》的书中,一直以为阻抗边界条件其实和PML、AML一样,只是用来定义声音的无反射边界而已。后来在一篇论文里《Numerical evaluation of source-receiver transfer functions with the Fast Multipole Boundary Element Method for predicting pass-by noise levels of automotive vehicles》以及相应的另一篇中有一句话,是the application of the interior impedance boundary condition for the suppression of fictious eigenfrequencies,而采用这种方法的原因是,这些频率are resonant frequencies of the interior cavities that are enclosed by the BEM surface mesh.at these frequencies the solution the surface unknowns in non-unique. 不明白这倒底表示什么,想来作者想说的是,可以用阻抗边界条件来抑制负频率吗?为什么会因为车体结构上的频率与这些谐振频率的问题,就需要去抑制它呢?这种方法的原理,可以有老师用直观的方法来指导下吗?
对对,确实是这个问题,不好意思,这个问题之前没有描述清楚,确实是在快速多极边界元中使用的,模型是一辆车的结构模型。只是有些我不明白,对于一辆车,它的结构网格是面网格,我知道可以对面网格进行定义吸声面板属性,可以使用阻抗,只是,什么叫在结构内部施加阻抗呢,而且作者施加的阻抗却是声学特性阻抗,作者是这样说的:since the solver is based on the indirect BEM formulation, irregular frequencies are treated by the application of an impedance boundary condition with the characteristic inpedance of air, being 416.3kg/m2s,on the interior surface of the mesh.