Displacement in Modal Analysis

Using SimScale Post-processing
1

I wanted to know whether the displacements in Modal Analysis are Shapes or actual displacements (numerically accurate) ?

2

Hello @atimotors,
depends on what you exactly mean by Modal Analysis and “numerically accurate”.

The analysis type Modal on SimScale is a 2-stage analysis, where first the requested Eigenmodes and Eigenfrequencies are computed and then a transient linear dynamic analysis is done on a modal basis. The displacements generated here should be physically correct (within the limitations of the approximation by the requested modes and the overal FEA modelling limits).

If you are talking about a Frequency analysis, we compute there only the Eigenmodes and Eigenfrequencies. In general (not only within SimScale), they have an arbitrary scaling without a physical representation. You could have different measures how to normalize the modes, but ultimately they are randomly scaled. You will recognize that the modal displacements have no unit displayed in the post-processor.

I hope this explanation helps.

Best,
Richard

2 Likes
3

Thank You, that is exactly what I wanted! :grinning:

4

I am very interested in modal analysis. What analysis mode should I use in SimScale and am I limited only to the modal analysis of solids? In a different post, I learned that modal analysis for fluids is in development and may take some time to materialize—just wondering if I misunderstood (yay) or if the same limitation would apply also to solids, in which I am even more interested than fluids (bummer).

Thanks!