SimScale CAE Forum

Simulations of pipe with shrinkage

I am working on a simulation of a pipe with shrinkage and I am really having a problem to get good results. I’ve tried several mesh configurations and I’ve changed the numerical settings but none of these tries worked. The pipe has the following dimensions:
Diameter 1: 40 mm; Diameter 2: 20mm; Length of the 1st section: 1000 mm; Length of the 2nd section: 500 mm. Total length: 1500 mm.

This is the link of my last simulation try:

Someone would have a solution or a tip to help me solving this problem? Do you think the sharp corners/edges would be an issue?

I thank you for your attention!

All the best!

Hi @bertrand,

have you had a look at the shrink fit analysis by my colleague @ahmedhussain18? You can use this as an inspiration.

Shrink Fit Analysis of Tool Holder

Let me know if that helps.



Hi @jousefm,
Thank you for your answer.
I think I cannot use your colleague simulation as an inspiration because it is a FEA analysis and in my case it is a CFD simulation.

Hi @bertrand,

thanks for pointing this out. Did not have a look at the project you posted. Will have a look at it as soon as I have time and come back to you.

Could you explain what kind of result you would expect from the simulation as you are talking about “good results”.



Hi @jousefm ,
When I say “good results” I would like to say coherent to reality. The velocity and pressure field that I have got as answer are clearly false. In the velocity fields, for example, one cannot see the fluid recirculation zones; The pressure fields are almost constants (Almost all the results are constants according to the field charts). I expect to see at least a pressure drop due to losses between the inlet and the outlet of the fluid domain.

The residuals charts do not descend to at least 10^-4 as well, but for that I need to check the convergence criteria of this solver.

Thank you very much for you attention!

All the best

Hi @bertrand,

I get you now. Let me check that out as soon as I have time. :slight_smile: :+1: Feel free to try some adaptions in the boundary conditions if you have time. If you do not want to use own core hours you can contact me and I can run the simulations for you. No worries about that!

Cheers and all the best!


OK @jousefm, thank you very much!

Best wishes!

Sorry for the small delay @bertrand!

Some things I would recommend to you:

1. Could you try using the standard wall boundary condition and not the customizable one?

2. The simulation has to run for a longer period of time - only 20 timesteps are performed in your simulation. An incompressible flow case requires something more than approx. 200 to get to steady-state. An ideal number will be 1000 to 2000.

See if these changes have a significant impact on your simulation and let me know how things go!

Good luck!