[Federico Vegetti]

Hi,
I've performed an incompressible RANS simulaztion with simpleFoam of a race car but i get a CL>0 and I don't know why.
Looking at the results it seems that the CL(f) is positive and generally higher in modulus with respect to CL(r).

I didn't performed mesh convergence, the mesh is only 2 milions of cells but I expected a result quite different from the current one.
I provide the slice of a section of the car with pressure field visible and the system folder.

I hope someone can help me.

Thanks you in advice.

[Martin_Sz]

A positive lift coefficient (CL>0) in your incompressible RANS simulation with simpleFoam for a race car indicates that the simulation is capturing some force acting upwards on the car. Here are some potential reasons why this might be happening and troubleshooting steps you can take:
1. Geometric Errors:
* Double-check your race car geometry for any inconsistencies or imperfections that might be causing an asymmetrical pressure distribution leading to lift. Ensure the car's underbody and wing are modeled accurately.
2. Boundary Conditions:
* Verify that the pressure boundary conditions are set correctly, especially for the ground plane. The pressure at the ground plane should be set to static pressure, not zero pressure.
3. Mesh Issues:
* While you haven't performed mesh convergence, a coarse mesh with only 2 million cells might not capture the flow details around the car accurately. Refining the mesh, particularly near the car's underbody and wings, can improve the results.
4. SimpleFoam Limitations:
* SimpleFoam is a basic RANS solver and might not be ideal for complex aerodynamic simulations involving race cars. Consider using a more advanced turbulence model or solver designed for external aerodynamics.
Troubleshooting Steps:
* Refine your mesh and check if the lift coefficient converges to a more reasonable value.
* Simulate a simpler bluff body case (e.g., a box) with simpleFoam and validate your setup against known results to ensure it's working correctly.
* Explore using a more advanced RANS solver or a detached-eddy simulation (DES) approach for better accuracy in race car aerodynamics.
If you can share more details about your setup, such as the specific boundary conditions and meshing strategy, it might be possible to provide more specific guidance.