[Jam Racing 2015]

Hello.Need help.I want to put an S.T.L file of my Formula Vee racing car in place of motorbike.Do I need to change size of wind tunnel,reynolds number??I have read on an F1 forum and someone there says garbage in garbage out.How accurate will my results be.Forces,streamlines and cutting plane.Thanks John

[Jam Racing 2015]

Why wud my post be terrible.I am asking question that I do not the answer to frm u experts and get rated TERRIBLE???? What is the purpose of this forum then

[chegdan]

John,

Pay no attention to the rating, I was not aware that one could rate these posts ... plus, your question isn't terrible. So no worries

Now, to answer or provide some guidance. To mesh your car it is a little more than just replacing your STL in the motorbike tutorial. You will need to think about a few things:

1. What are the physical dimensions of you car? --> this influences the size of the wake boxes and placement around the vehicle
2. How big is your wind tunnel? --> you will need to change the blockMeshDict or add a wind tunnel stl.
3. What is the smallest feature you want to capture on your car? --> this will influence the selection of base mesh size and also local refinement level
4. Is the floor stationary or moving? --> this will influence boudnary conditions or if you need something else like a slip to no-slip boundary on the floor

You will need to edit the system/snappyHexMesh and add entries for the new geometry, edit surface (and volume) refinements, change any size of the wake boxes, configure layer controls and most likely the locationInMesh entry. For vehicles, these meshes can become really large (in fact the motorbike isn't detailed enough for analysis) so think about your computing resources available. To get a nice match with experimental results on a detailed vehicle, we are talking about 10's of millions of cells. My colleague gave a brief introduction to snappyHexMesh (search for snappyHexMesh) at the last OpenFOAM workshop (there are others from previous workshops too). Good luck and just ignore the ratings

[Jam Racing 2015]

First of all u are an Officer and a Gentleman.U too the time to answer my question.What I was trying to get at is if I put my s.t.l file in of my racing car without change any settings,the results wud not be correct.So the guy on the F1 forum was correct in saying that if u do not know how to set up OpenFoam,ur results will not be accurate.

[chegdan]

No problem! I'd definitely agree with the F1 Forum comment and your earlier comment of "Garbage in, garbage out". These simulations take some time to wrap your head around, but you start with deciding what you want to achieve and then go from there. Ask away.

[Jam Racing 2015]

I did the drawing of car in Rhino cad.I did not know how to round off edges as on real car.But the streamlines show a problem at front suspension which is off a Beetle.Two 50 mm pipes.I see the flow seperates big time behind them.That was my area of concern.I do not know how to have wheels rotating either.They wud have a huge effect on the aero around body too.So moral of this is C.F.D is not childs play.Have built a small wind tunnel and my test around a model of my car show similar flow past front suspension when smoke added.I am not doing this for gain but rather as a hobby.

[chegdan]

This sounds like a pretty fantastic hobby.

You may want to look at some OpenFOAM material on Automotive Simulation like this one i found. For rotating wheels, you can set a rotational boundary condition with something like a rotatingWallVelocity (How to use rotatingWallVelocity boundary condition).

[Jam Racing 2015]

Thanks.Was reading up on our friend snappy. So much to learn.Ur help is appreciated

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[Jam Racing 2015]

Do the wheels have to separate from model?

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