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  • Documentation

    Error: Multi-Region Mesh in Non-CHT CFD Simulations


    A setup with at least X regions is being used in a single-region analysis type. Please ensure that only one fluid region exists and that all other bodies are assigned to an advanced concept. If you have already meshed the geometry, ensure that all the meshing regions except one are cell zones.

    What Happened?

    The platform detected a multi-region mesh for non-CHT CFD simulations.

    What Could Be the Possible Reason?

    For non-CHT simulations, multiple bodies are not allowed, unless the additional bodies will be used as advanced concepts.

    What Can I Do Now?

    The most common cause for this error in non-CHT simulations is the lack of a flow volume extraction operation. Please note that non-CHT analysis types are single-region analysis. Therefore, they only require the flow volume to run correctly.

    Taking a meeting room as an example, if we attempt to run an incompressible analysis with the following geometry, it will fail. The geometry consists of the solid parts, which is not intended for non-CHT simulations:

    multi-region mesh error
    Figure 1: This geometry contains 17 solid parts (regions). This configuration is not appropriate for non-CHT simulations.

    To make this geometry appropriate to run a simulation, we need to create the flow volume and delete the solid parts. Figure 2 shows the resulting geometry for the meeting room, after following the outlined steps:

    room with flow volume
    Figure 2: Meeting room geometry that works for a non-CHT simulation. Note how we have a single volume in the geometry, representing the flow region.

    In case you are in doubt about the flow volume creation process, please visit this tutorial for a more in-depth guide.

    A second common cause is related to the Advanced concepts. For single-region analysis, we may intentionally have more volumes when we are modeling advanced concepts:

    lists of available advanced concepts in simscale that can be used to resolve multiple bodies in non cht simulations
    Figure 3: List of advanced concepts for a sample transient incompressible analysis.

    If the user forgets to create a cell zone and assign it to an advanced concept, it will result in a multi-region mesh error when running a simulation.

    Important Information

    If none of the above suggestions solved your problem, then please post the issue on our forum or contact us.


    Last updated: July 6th, 2023