Dear ANSYS community,

I did a modal analysis for a stator-housing combination of a motor using ANSYS Mechanical.

In order to avoid fluid dynamic simulations I modeled oil as a solid using the following material parameters:

- density: 822 kg m^-3
- linear elastic behavior with
- bulk modulus: 1.476E+09
- Poisson's ratio: 0.499

The density and bulk modulus are taken from a datasheet. Since liquids can be assumed to be incompressible I set the Poisson's ratio to 0.499.

In the results of the modal analysis there are hundreds of eigenshapes which only show a deformation of the surrogate solid. These deformations look strange and do not lead to noticeable deformations of the outer housing (not displayed in attached screenshot). Furthermore, the eigenfrequencies of these eigenshapes lie close together. A picture of the deformations of the surrogate solid which should represent the oil is attached.

Do you have any ideas why the deformations look like this? Do I have to choose other material parameters to substitute the oil with a solid? I am glad for each hint you can provide.

Kind regards

Marius Hensgens