SimScale CAE Forum

Getting natural frequencies of liquid in container

Hi all

I need to get the first few natural frequencies of liquid in a pot at different fill levels and pouring angles. I imported the pot geometry and generated a mesh for it using the tet-dominant algorithm. I’m wondering how to proceed from here. Namely:

  • Which analysis mode should I use? I’m guessing Incompressible should be it, but will this give me the natural frequencies of the liquid?
  • Should I import a separate geometry/mesh for the liquid in the pot or can I generate it in SimScale more easily?
  • Can I modify the liquid geometry/mesh to capture different liquid fill levels in the pot?
  • Can I rotate the pot relative to the direction of gravity?

Many thanks in advance!
Tony

Hi @tsoares and interesting application you are working on!

Darren (@1318980), you simulated sloshing and have more experience in that topic. Do you know if we can incorporate frequency analysis to the simulation?

As for the rotation you can freely choose the axis of rotation.

Best,

Jousef

Hi @tsoares, unfortunately, I am not experienced in fluid natural frequencies, I know we are capable of applying a oscillation to a body containing liquid, that oscillation could be used to set a frequency. How would you determine if the liquid is at a natural frequency?

Multiphase would show the surface of the liquid and would be used for sloshing.

Best,
Darren

Thank you both for responding so fast!

Sadly, I have little hands-on experience with modal analysis, and not much more with general FEA or CFD analysis. I frankly don’t know how engineers elsewhere would go about determining the natural frequencies of beams—I only know that they do…

I asked in the hopes that someone would have a ready answer to ease my learning curve, but no worries. Everyone is trying to do a different type of analysis, and I don’t even know what mine is supposed to look like.

I’ll start by learning about modal analysis and see if and how I can do it in SimScale. I hope that I can, because I’d rather not have to install new software (flat out of memory for more programs). If SimScale won’t do today, I hope that in a few years it will…

I’ll post an answer if I figure out how to get these natural frequencies. Thanks for being so responsive!

Tony

2 Likes

Well if its just the natural frequency of the pot and maybe the liquid could be modelled somehow maybe FEA is the way to go. @jousefm?

Best,
Darren

Sure Darren! In another post I answered @tsoares already saying that the release of the feature might take a bit but it is on our roadmap so stay tuned :sunglasses:

Best,

Jousef

Hi all,
computing the eigenfrequencies of a partially filled container is a very specific topic and can be realized in a variety of different approaches.
One example is having a coupled fluid+structure solver, where the fluid is modeled with a simplified model for the fluid and its free surface.
This method can be used with Code-Aster, which is the solver for all FEA simulations on SimScale and we will also use it as the solver for the new eigenmode analysis on SimScale.
Here you have an example from the Code-Aster validation cases, which deals exactly with sloshing modes of partially fille containers: https://www.code-aster.org/V2/doc/v13/en/man_v/v8/v8.21.101.pdf
These methods are under steady development as can be seen by (a rather) recent news post: https://www.code-aster.org/spip.php?article993

As these are very advanced methods for eigenmode calculations they wont be in the scope of the initial release on SimScale.

Best,
Richard

2 Likes

This looks just like what I’m after—determining the sloshing frequencies for a liquid in a container (of arbitrary shape, at different fill levels/tilt angles relative to gravity). Any idea when this functionality might be ready? Thanks!!!

Tony

Hi @tsoares!

We have no specific date for the release but we would encourage you to post your feature request into this section: Vote For Features. The number of votes tells us how much users would like to see a new feature on our platform so make sure to put your request in there :slight_smile:

Cheers,

Jousef