# Help finding Cd and Cl on 3D car wing stabilizer

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 September 2, 2009, 09:08 Help finding Cd and Cl on 3D car wing stabilizer #1 New Member   Join Date: Sep 2009 Posts: 7 Rep Power: 9 This is the 3D object (is just an example to learn to use fluent): Designed with Solidworks and meshed with gambit (unit lenght is not m so i changed it on the fluet units task). I want to analyse the drag and lift coefficient with an airspeed of 10m/s only on X axis. What type on boundary i must set on layer A,B,C? Wich kind of viscous i must use? thanks for the help, I am a student and a beginner on fluent.

 September 3, 2009, 00:02 #2 New Member   Sean Delfel Join Date: Aug 2009 Posts: 27 Rep Power: 9 Hi Rizz, That's a bit of a tricky problem as a starter (especially to mesh), but it should be fun. You will most likely just want to use wall boundary conditions (no slip) for all your surfaces, which should be the default. If you are going to model it in 3D, I would recommend using the symmetry of the problem to cut the size of your mesh in half (define a symmetry plane down the middle of the wing). I would then just put a velocity inlet several chord lengths ahead of the wing set to 10 m/s and an outflow or pressure outlet several chord lengths behind the wing. In terms of turbulence models, you can really take your pick. The spallart-almaras model might be a good starting point for this problem. In terms of reporting the lift and drag coefficients, Fluent can report and plot the integrated forces and their components for any of the surfaces you define once you have a solution (report -> forces). Hopefully that all makes sense. I would highly recommend you look at some of the tutorials in the fluent documentation to save yourself some headaches. I believe there's actually a 2D airfoil tutorial which may help you out. Cheers, -sean

 September 4, 2009, 20:06 #3 New Member   Join Date: Sep 2009 Posts: 7 Rep Power: 9 How can i make this symmetry? Is there a option in fluent or i must construct it before meshing?

 September 13, 2009, 18:30 #4 New Member   Anastasios Join Date: Mar 2009 Posts: 17 Rep Power: 10 Either you import it from Solidworks into Gambit or you design it from scratch in Gambit, design the half of your wing and define the face that lies on as "SYMMETRY". As there is symmetry, there is no need to spend time on calculating the other side. FLUENT will understand that symmetry and there is an option to see it mirrored.

 September 13, 2009, 20:06 #5 New Member   Join Date: Sep 2009 Posts: 7 Rep Power: 9 ok but where is the mirror options? with this mirroring, should i do create something like control volume or surface around the wing?

 September 14, 2009, 06:45 #6 New Member   Anastasios Join Date: Mar 2009 Posts: 17 Rep Power: 10 You create the geometry and the mesh exactly as you would do with the whole model. When you define the boundary conditions, you define the face that is symmetrical as "SYMMETRY". Run in like this and in FLUENT and watching it mirrored is just an option of view. It doesnt' matter in the analysis.

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