Transferred quantity in System Coupling

mesemese Member Posts: 7

I have a fluid model in Fluent and a mechanical model in Transient Structural which are linked through System Coupling. My problem is about the quantity which is transferred from the mechanical model to the Fluent. System Coupling accepts only the “Displacement” from the Transient Structural, not “Location” or “deformation”. Here I explain why that is an issue for my model.

In the Fluent, I am using Overset Mesh for movement of two solid objects which are surrounded by fluid. Each of the objects is defined in its own Overset component, and both meshes are appended to a stationary background mesh. I tend to use Mesh Motion for the movement of each component because in that case, the object and its mesh are moved together and it will not be needed to modify the mesh by dynamic Remeshing. However, one of the objects is flexible and deforms in contact with the other object (which is rigid), and it is needed to modify its surfaces in Structural before Fluent uses it in the fluid model. The model in the Structural contains one flexible and one rigid objects. Note that as the rigid object is not deformed, we need to transfer only the surfaces of the flexible one.

Anyway, if we use Mesh Motion in Fluent, this is what will happen at each time step: Fluent moves the two component meshes so the objects move as rigid bodies. Structural moves the two objects, modifies the surfaces of the flexible one and sends “displacement (incremental displacement)” of the flexible object to the System Coupling. System Coupling sends the displacement to the Fluent. So, in Fluent, the rigid object moves correctly by mesh motion, but the flexible object moves twice: once it moves (with a deformation) because of Structural model and moves another time as a rigid body by mesh motion.

If we could transfer “location” from Structural to Fluent, only one movement would happen for the flexible object because the movement done by mesh motion would be overwritten by the locations coming from the Structural. Also, if we could transfer “deformation”, we could add it to the rigid body mesh motion in the fluent, which again would give us the correct movement.

Is there any way to transfer either Location or Deformation from Structural to Fluent?


  • SteveSteve Posts: 153Forum Coordinator


    There isn't a way to transfer Location or Deformation from Structural to Fluent. Please add some screenshots so we can get a better understanding of your setup.

  • mesemese Posts: 28Member
    edited September 2020

    Thank you for your answer. In the following, I put some photos with explanations. To clarify, each of the objects is a part of a disc which rotates.

    (Please note that here I'm showing the "ideal" case where the motions are all defined by Mesh motion. As the Fluent cannot receive the Location, I have changed the model so that the meshing for disc 2 is stationary and instead, the wall movement for that disc is solely caused by Structural. I wished there was a better solution ? )

    All solid objects and the domain are shown in the below picture. Arrows indicate the directions for rotations.

    The background mesh is inside the below picture (The mesh itself is not shown):

    The component mesh for the disc 1 is shown here. Note that the mesh is very fine and we see the meshing part in black. The borders for the mesh are all defined as Overset.

    The following picture shows the walls for the disc 2 which is surrounded by a mesh. The borders for the mesh are all defined as Overset.

    Hope that helps to clarify.

  • mesemese Posts: 28Member

    Dear Steve, I have added the pictures as you asked. Any thoughts/ suggestions?

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