I tried to implement the spectral element method1 as proposed in . I simulated an aluminum plate and a vertical concentrated force was applied at the middle of the top left quarter of the plate2. I should get a wave with circular crest, coming from the point where I exerted the force. But apparently the wavefront got inverted as illustrated in the following picture.
There must be something wrong in my code . What could have happened?
Something wrong during assembling of the stiffness and mass matrix? This link contains my python source code in pdf format and the video that illustrates the propagation of the wave. I will try rewrite my code with ordinary plate element first.
1Here, SEM is just finite element method with higher order polynomial shape functions. Some other works use sinusoidal shape functions.
2I didn't abuse symmetry since I will add something to the plate later.
Update: I tried using ordinary plate element instead, but the results are the same given that the mesh is fine enough.
Edit 2: I think my code is actually correct, given that the Abaqus simulation also show such circular pattern on the top, bottom, left and right of the main crest (they are more obscure though). But I am still puzzled about why those circular pattern appear. I guess it has to do with the concentrated load and the effect of such spurious pattern would be weakened only if I refine the mesh (h-refinement). But from my observation, p-refinement does not help.