SimScale CAE Forum

Error Simulation

A multi-region mesh was assigned - this analysis-type requires a single-region mesh.

Please help me guys, I’m a beginner…

Hey @whildanry,
there are a few threads in this forum about this topic.
Did you try the advices in this threads ?

Best regards


I find that for CFD you must use “closed inner region”, is that true? Because my model have two open ventilation, that means my model have any openings to the outside.

Thanks for your atention,

1 Like

That is true indeed.

That is correct. Your simulation domain needs input and output (inlet, outlet). That way you direct the flow into simulation domain (with mostly a given velocity) and make an outflow (with mostle a pressure outlet).




@Retsam thank you so much, I will try it.

hey @Retsam, can you solve my problem please?

I still learn about HVAC in a room, I follow this tutoial
But, i got same error when i run my simulation “A multi-region mesh was assigned - this analysis-type requires a single-region mesh”.
You said that for CFD simulation you must use “closed inner region”. But in this tutorial video, he did not use “closed inner region” and that is not problem at all.

Can you please check my project please…

Thanks for your attention,

@whildanry: you have to use internal CFD simulation. You will simulate the air flow in a room, but you just need one solid representing that air in the room.

Currently you have 9 solids instead of 1, so the message about multi region mesh is justified. You need just the air volume in that room, as you simulate flow in that air volume. Your current mesh is not appropriate, as it is a model of the room with walls, open window, ventilators, etc.: everything useless for internal CFD simulation.


So please create a minimalist geometry representing the air in that room: it will be your simulation domain.

Take care,



Thank you!!