Hey!
Im trying to set up a CFD Analysis of a car and I need to set the reference area. However it just says that I have to find it in OnShape, but I dont know how and I would appreciate help.
The Tutorial im following is the default “aerodynamics of a car” tutorial and my project is this one:
Kind regards,
Ladan
Hi Ladan!
Maybe this posts helps you out (does use ParaView though): How to determine the coefficient drag in Paraview
Let me know if that worked for you!
Jousef
Can I use a Parasolid file in ParaView?
Edit: I have a second question, am I able to online use half of the car in ParaView as stated in the tutorial?
That doesnt really work for me, I get 19 square mm which cant be correct, is there any other program I can use for it?
Hi there 
OnShape is a great solution for your case, do you have an account? I can give you some tips.
Best regards,
Fillia
I have, it would be awesome if you told me how to do it in onshape
Hi,
This is fairly simple. Basically you need to create a sketch perpendicular to the frontal view of the car. Once you do that, you can use these 3 functions to draw/obtain the projection:
1- Line
2- Spline
3- “Use” (which projects faces/edges onto the sketch plane)
Once done, simply click on the areas of interest and then on the icon in the bottom-right corner to see the area:
Cheers
That’s due to how the geometry was constructed. Usually I will create a part studio in context from the assembly page:
Which will result in this:
You can use this representation to draw the sketch directly. I personally prefer to use a mirror function on the model first, so I have an editable copy of the assembly:
I hope this helps.
NEVERMIND, I reloaded and it showed, its 1,047059m which seems right
I have a new question 
I tried to add the first “Cartesian box”, but I dont know which coordinates to put in minimum and maximum, in the tutorial it just says specific values for the car in the tutorial.
The car tutorial provides a rule of thumb in figure 5 for a generic car. Please double check that.
Cheers
isnt that only the walls around it? I thought the cartesian box was smaller?
Hi,
Are you referring to which cartesian box, more especifically? The one from the region refinement?
If that’s the case, there is no need to be “precise” in terms of coordinates. As long as you understand the purpose of them, and size them accordingly (see fig. 32), then you should be good
If you are still worried with the placement, I would recommend checking how many car length’s the cartesian boxes from the tutorial have upstream/downstream/side/top, and replicating it with your own geometry.
Cheers
