SimScale CAE Forum

Need help simulating wind flow through a house


I am a new user to CAD simulation, and I am facing some issues when trying to simulate wind flow from different directions through the house:

To simulate the air outside the house flowing in, I tried to use the external flow volume function. When I tried running it without inputting anything, I got the error message: “The flow region could not be created. Please search for potential problems around the following entities… and consider cleanup operations in your CAD tool.”

To try and solve this problem, I then tried to form a union between all the walls and doors in the house to only meet another error message: “Union operation failed as the result does not constitute a usable manifold body. Trying narrowing down your selection set, or contact our support team for assistance.”

(Every part except the unselected parts as shown in the picture are part of the union)

Can someone please advise me on how I should go about running this simulation? Thank you!

Hi wcw thanks for reaching out to use in the forum.

I took a look at you issue and please make sure that your bodies clearly intersect with other bodies.

Please have a look at the solids that are causing the issue. and use the translate tool to have clear intersections.

Best regards Sebastian

Thanks Sebastian for your reply!
I managed to solve it by forming an assembly with all the parts on Comsol (where I imported the design from).

Hello, after tinkering around for awhile, I have reached the simulation step.

However, I got the error message: “A setup with 37 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”

I found a forum post that raised a similar issue:

The first advice is to make a boolean union in the CAD software, which I have already done, and the second is to select ‘Add geometry operation’ and merge all solids into one.

I am not sure how to proceed after this step to merge all the solids together, can someone help me?

Hi just make sure that after you created the flow region you delete all bodies except the flow region

The number of solids should be one for such simulations.


Please have a look on our documentation about this issue here

Hello! After doing what you said, I realised that I should be using inner flow region instead, or it will turn out like this :joy::

However, for my model, I am not sure what constitutes as “seed face” or “boundary face” even after referring to this article: How to Create Flow Volume Extraction? | Knowledge Base | SimScale

I tried to choose a random window as a seed face, and the outer walls as the boundary faces, but that did not quite work out. May I know what I should do in this case?

Thank you!

Hello, to create a closed inner fluid volume you can just use a face on the inside of your room and the outside face of the wall with the open window.

You can also import the missing window. This would mean that you have a closed inner volume. with that you won’t have to select a boundary surface.

Hello! I am finally able to get my simulation up and running!

But I had some confusion initially, which I thought I should mention for others’ reference.
Initially, I chose the window as the seed face, and the inner and outer walls as the boundary face, which gave me this error message.

After hiding the outer wall, I realised that my walls and windows both consist of two faces, which I did not account for :sweat_smile:

I was able to generate the inner flow region after selecting the inner window face as the seed face and inner wall face as the boundary face.

Thank you for all the help @SBlock :slight_smile: , I could not have done this without all your help!

P.S. I set the second post as the solution, since it is the answer to my initial question.

Hi great work there, I’m happy that I could help and that’s what’s the forum is there fore. :slight_smile:

Have a good time simulating :smiley:

Best regards Sebastian

Cool, glad to have joined. Now I can learn more useful information