Displacement (module) animation only shows x direction?

Project Support
1

I am analyzing the effects of sound pressure on a frog middle ear throughout a frequency range using harmonic analysis. To do this I am gathering displacement data at the innermost and outermost ear components and analyzing the motion of the components relative to each other. When I animate the results using the “Displacement Module” field, the pressure appears to be applied only in the x direction, and the motion does not look right. When I use the field “Displacement (real)”, the motion is like what I would expect. But I see in the documentation that for real/imaginary “The components have no physical meaning on their own, thus we recommend using the magnitude and phase representation by default.”

Is there an error occurring, or is there some problem with my setup?

In this project see “Help: Standard Simulation” > Simulation runs for examples of what I’m seeing. I scaled the displacement by 1000x.

Thanks,
Rachel

2

Hi Rachel!

There are a few details about harmonic simulations that need to be cleared before interpreting the results, because they are complex numbers. I think that the best would be for you to refer to the documentation or some book on the matter.

Here go some pointers:

  • For each degree of freedom (X, Y and Z displacements for example, are one degree of freedom each), the harmonic response at a given frequency is represented by a complex number.
  • The complex number has a real and imaginary parts, but the real value of using it lies in the phasor representation, capturing an oscillation amplitude and a phase angle.
  • In the postprocessor, we recently released a change to distinguish the ‘module’ of the complex number (amplitude of oscillation) from the ‘Magnitude’ of the displacement vector. Previously we talked about ‘magnitude and phase’ representation, but now it is being changed to ‘module and phase’.
  • In the postprocessor, you can select the vector for the deformed shape, it should be the ‘Displacement module’.
  • To distinguish that the deformation is not only happening in the X direction, you can switch the coloring between Displacement (module) X, Y and Z components (although the X component can perfectly be dominating due to the boundary conditions and load).