Only one mesh is allowed in FSI module?

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Alex Lan

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Mar 13, 2024, 3:39:56 AM3/13/24
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Hi everyone,

I tried to model vehicle with four flexible wheels in a CRMTerrain. I referenced demo_VEH_CRMTerrain_WheeledVehicle and demo_FSI_Flexible_Toroidal_Tire. However, the simulation was stopped at the step of terrain.Initialize(). I tried to modelled two flexble wheel in demo_FSI_Flexible_Toroidal_Tire, and the simulation also stopped at the stage of terrain.Initialize(). So, is only one mesh allowed in the CRM-FEM cosimulation?

Best regards

Radu Serban

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Mar 13, 2024, 4:04:57 AM3/13/24
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Alex, you are correct. Currently Chrono::FSI is limited to working with a single FEA mesh.  To model multiple flexible tires, you would need to put all nodes and elements into a single mesh.

Better support for FEA in Chrono::FSI, including allowing multiple meshes, is something that is on the todo list and will be worked on soon.

 

Best,
Radu

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Alex Lan

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Mar 13, 2024, 5:28:20 AM3/13/24
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Thank you Dr. Radu.
 
These tires are associated with different wheels.  How can I model multiple flexible tires with a single mesh? Can I implement it with the implementation of demo_FSI_Flexible_Toroidal_Tire?

Best regards,
Alex

Alex Lan

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Mar 13, 2024, 9:02:07 AM3/13/24
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Oh, I implement it with a single mesh. Thank you for pointing out!

Best regards,
Alex

Radu Serban

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Mar 13, 2024, 9:16:49 AM3/13/24
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That’s correct. For something like demo_FSI_Flexible_Toroidal_tire, it’s easy to build the meshes for all flexible tires within the same ChMesh object.  But that’s not the case if you want top use a vehicle model with its own flexible tire models (as those encapsulate their own ChMesh objects).

--Radu

Alex Lan

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Mar 13, 2024, 10:53:49 PM3/13/24
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Hi,
I'm going to implement a new tire class for the vehicle in this condition. I would ask if the collision or contact model of tires is not used for MBD or FSI system update in the SPH environment? Because the tire interacts with terrain through BCE markers.

Best regards,
Alex

Radu Serban

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Mar 14, 2024, 3:04:49 AM3/14/24
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Alex,

 

You are correct that you do not need to specify a collision shape for the tire in order to capture the interaction between the tire and the CRM terrain.  You would need one if you also wanted the tire to interact with other potential rigid objects in the environment.

 

You can certainly try to implement a tire class to work around the current Chrono::FSI limitations, but it may be better to wait until we get to the Chrono::FSI refactoring I mentioned before.

Alex Lan

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Mar 14, 2024, 4:47:30 AM3/14/24
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Hi Dr. Radu,

I'm using the old version of Chrono. I have implemented the tire class, and it works well. It is indeed a feasible approach to model the tires into a single mesh. Thanks for your answer and your team's efforts!

Best regards,
Alex

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