Need help with perforated duct simulation

Hi all, I’ve linked my project below:

I’m attempting to model two perforated ducts to analyze the velocity of air coming out of it. Thus I’ve created a geometry primitive for that. Two problems I’m having is:

  1. A setup with 2 regions is being used in a single-region analysis type. Please make sure that all regions except for one have an Advanced Concept assigned to them.

  2. In single region simulations, only the fluid region can be assigned to a material. Please review your material assignments, making sure that only the flow volume region is assigned.

How do i resolve this? Additionally, is it better to create an external flow volume in CAD model or create a primitive box to analyze the flow coming out of the ducts?

Lastly, what is the difference between incompressible and convective simulation in this for this instance?

Thank you for the help!

Hello dunnoebruh,

thanks for reaching out to us here in the forum.

  1. To your first question please have a look at this article:
    Error: Multi-Region Mesh in Non-CHT Simulation | SimScale

This goes also for the material assignment.

What I would suggest is that like in your first case you create an external fluid volume and delete the piping, since you are only interested in the fluid domain.

Best regards Sebastian

Hi Sebastian,

Thanks for getting back to me. If you can take a look at my project again, would the perforated_duct corrected and convective heat transfer 4 reflect your comments?

I’m still confused on what is the difference between the incompressible and convective simulation options for this project? Additionally, when would one use a geometry primitive? I’m a beginner, apologies if these questions are too simple for this forum.


Hello dunnoebruh,

unfortunately, it seems like the link to your project is not working anymore.
And no problems to your questions, we all have started at some point.

To answer your question, the incompressible solver can solve gas until Mach 0.3 with assuming constant temperature.
the convective heat transfer solver, can also solve temperature changes within the fluid.


You mostly use geometry primitives to create mesh refinement regions. All other Cad geometry you usually provide with the CAD Upload.

Best regards

Hi Sebestian,

I’m looking for your help. The link to the project should work again.

In my simulation, the velocity at the outlet isn’t converging properly. I was wondering what can be done to resolve this issue as seen in run 4?


Hi dunnoebruh,

when I have a look at your setup. I notice that you have faces which is the outlet of the pipe.
Whenever you define an outlet, the air will exit the fluid domain and therefore will not be taken into account when simulating the air flowing into the box.
Therefore after creating the external fluid volume delete the CAD parts, so that you are left with only the air volume.
You can keep the setup for the inlets and outlets of the pressure outlets for the sides.

Also, make sure that the mesh is finer enough for the perforated holes.
If your simulation is diverging you can also use this method to detect bad regions.

Best regards Sebastian.