Fluids

Fluids

Two-Way FSI: Size Limits Issue

    • simonhackett
      Subscriber

      I am running a student license version of ANSYS 2020 R1.

      I am attempting to simulate a rocket fin in supersonic flight (air at 686 m/s) using Transient Structural, Fluid Flow (Fluent) and System Coupling. I've been trying to follow tutorials, but I've been stuck now on solving the simulation even after some major simplification down from an assembly to a single part.

      The first error message that appears tells me I am exceeding the version size limits, when my structural mesh has 11950/5640 nodes/elements (it was closer to 28k before but I just greatly reduced it to see if it would help) and my fluid mesh has 37638/198326 nodes/elements (again, it was around 350k before, but I reduced it to try and fix it and it did not work). I ran into a similar issue with a one-way FSI simulation which was throwing size limit errors, and was able to solve it by clearing generated data but the same method is not working here.

      Does anyone know why this might be happening, or a quick fix other than what I have already tried?

    • mese
      Subscriber
      I have had similar issue and managed to solve it. Please tell me how you are generating your geometry. Do you define the geometry in Transient Studtural itslef or you import it from another module?n
    • simonhackett
      Subscriber
      I import the geometry from a STEP file which was initially modelled in SolidWorks.n
    • mese
      Subscriber
      I used DesignModeler for geometry definition. I used to define the geometry in the Fluent block and import it to Structural and I always had Size Limits error. Once I defined the geometry in the Block for Structural itself, the error disappeared although I was using exactly the same geometry.nFor your case, I don't know how to get rid of that error because you are not using ANSYS for geometry definition.n
    • simonhackett
      Subscriber
      Yeah and I'd say it's a bit complex for me to be using DesignModeler to create the geometry. This current simulation is simplified, so maybe it's worth a shot, but if it works then I need to move forward with making it more complex, by importing the assembly as a SETP file rather than just a single part of it.n
    • Rob
      Ansys Employee
      You may need to renumber the Mech model nodes. When you remesh it (as I understand it) starts numbering the nodes from where the previous mesh finished. So, you may have 28k nodes but the numbering is 28-56k for the node IDs. There are a few threads in the Structural section to explain this. In CFD we count the cells (and not the IDs) so don't have the same problem. n
    • simonhackett
      Subscriber
      Hi Rob, I think that may have solved the size limits issue, but I still get some other errors and I'm not sure what they mean. Thanks for the tip on mesh renumbering, I think it helped me solve a size limits issue before but I don't recall needing to do it every time that error message appeared. nI'll be making a new thread for the new error messages to try and understand what I need to change for this to work.n
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