could you please explain what the reason of the results as the picture showing? Answered

I built three models in Analyst a while ago.The difference of them is that the diameter of the each excitation source is 20mm, 15mm and 10mm.But the simulation result is vert different.And why the results of 15mm excitation source and 10mm excitation source are so disorder and abnormal? Is there anything wrong with the code ?

The following pictures are  screenshot of the output video files.The first is the result of 20mm  excitation source,the second is 15mm and  the third is 10mm.
①20mm  excitation source

②15mm  excitation source
③10mm  excitation source


  • hey,anyone?

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  • Hi,

    Meshing will likely be the source of these abnormalities. What is the element size compared to the size of the source?

    Can you share the files via your prefered cloud sharing service and we can look into this.

    Best regards,


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  • Hi,Mr Oliver

    I have upload my model input file to the CloudApp. You can download the file through following three links:



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  • Hi,Mr Oliver

    Have you looked into my code input files?What's the results and the reason of my results?And how to deal with it?

    Best regards 

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  • Hi Hxd,

    It is widely understood that a plane wave will propagate along a uniform FE mesh; however, it propagates at the wrong velocity yielding a progressive phase error in the FE solution. This is known as Numerical Dispersion. There's multiple resources online that covers this topic and can give you a better understanding of it. The reason for this in your case is due to the propagation distance the wave needs to travel the wavelength in steel of the wave is 1.55mm which means that the before reaching the defect it travels 555 wavelengths this is only one trip to propagte back to the source it needs to travel double that.

    Have a look at this example

    You can completely remove this section of the model meaning solve times wil be much quicker and the issues that arise due to numerical dispersion can be avoided.





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  • Hi,Mr Oliver,

    Frankly speaking,I can't understand that.But, why only the result of 20mm excitation source is normal? Other tow are very abnormal and disorder?

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  • Sorry I thought I mentioned this in my last comment another reason this could be happening is the size of the source vs the element size. Are you changing the size of the mesh with each model? A finer mesh might improve the results, but there will be trade off between this and simulation time

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  • Ok,all right.Thanks for your help.I will try a smaller element size and see the result.

    Best Regards

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