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-   -   [ANSYS Meshing] External aerodynamics of car (geometry and mesh mothod) (http://www.cfd-online.com/Forums/ansys-meshing/111463-external-aerodynamics-car-geometry-mesh-mothod.html)

 qbus_r January 8, 2013 00:09

External aerodynamics of car (geometry and mesh mothod)

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Hi everyone.
I have question about external aerodynamics of car, in specific question about preparation of the model.
I have prepared my model in SolidWorks and then exported into Design modeler. Now I got problem with wheels. If I want to have my car accurate on road I have to cut out tires tangent to the road, but no modeler ( i think) will allow such an operation because it will fire the "zero width geometry" error. So I thought of lifting my car up for example for one millimeter. But how can I connect later in mesher surfaces of my wheels and road as I don't want to have slim gap there ?

My other question is about meshing methods. I heard from Ansys re-seller and my tutor in university that for CFD simulations I should use new CutCell method, but i can't find any information about this method ( besides ansys' ads :) ). On the other hand everyone says that for aerodynamic simulation tetra should be used. Which one is better and why ? I couldn't find any comparison of those methods.

 Far January 8, 2013 02:41

cutcell is good method. But I guess with tetra + prism + Hexcore (upto wall) will do the job.

But two points are important to consider before proceeding to the volume mesh (in ICEM or Tgrid):

1. Geometry should be of high quality and water tight

2. Very good quality surface mesh.

Another option in ICEM would to use the octree (hence no step 2). Delete volume mesh and smooth surface. For volume meshing use denauly with AF and Tglib in ICEM or use Tgrid.

 qbus_r January 8, 2013 11:00

Thanks for quick response.
I am kind of stuck with Ansys + Fluent system. I think my geometry is tight as it is not created from surfaces -> I exported solids from Solidworks.
About mesh quality- I know that i should consider mesh with skewness < 0,98 ( 0,95). For now I have bigger skewness, how can I show those skewed cells (I know itis possible, but i couldn't manage to) ? Without that I can only predict where the mesh is highly skewed.
And about my second question, the wheels, how should I connect them to the road?

 Crank-Shaft January 8, 2013 22:36

Quote:
 Originally Posted by qbus_r (Post 400738) Thanks for quick response. I am kind of stuck with Ansys + Fluent system. I think my geometry is tight as it is not created from surfaces -> I exported solids from Solidworks. About mesh quality- I know that i should consider mesh with skewness < 0,98 ( 0,95). For now I have bigger skewness, how can I show those skewed cells (I know itis possible, but i couldn't manage to) ? Without that I can only predict where the mesh is highly skewed. And about my second question, the wheels, how should I connect them to the road?
The contact patch with the road may be modeled in different ways depending on the simulation intent. Are you trying to simulation a moving ground or a static vehicle? This will dictate what type of boundary condition you specify.

 qbus_r January 8, 2013 23:30

I want to do both simulation. For now i modeled something more like "wheel chocks" (as solid)and now I am trying to obtain mesh.

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