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Need Help setting up Test Environment For a Moving Object through Air

4 REPLIES 4
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Message 1 of 5
brutorknight
497 Views, 4 Replies

Need Help setting up Test Environment For a Moving Object through Air

Hello,

 

I would really appreciate some help setting up a testing environmet to simulate the movement of a truck and trailer model moving at 65 mph through air space.

 

My goal is to calculate the static pressure applied to a front and certain other areas.

 

That way when I apply different spoilers and attachments I could measure the difference at different speeds of the moving object ( i.e. 65mph , 75mph ) and at different wind speeds ( 0mph , 15mph opposite direction wind etc.)

 

Thank you in advance.

 

 

4 REPLIES 4
Message 2 of 5
Jon.Wilde
in reply to: brutorknight

Hi,

 

All you need to do here really is to model the truck within a wind tunnel (all drawn in CAD).

You would have a wind speed at the inlet, summing both moving speed and wind speed together and a P=0 at the outlet.

 

Kind regards,

Jon

Message 3 of 5
AstroJohnPE
in reply to: Jon.Wilde

 

I do not have too much experience with CFD, so I do not know if this would be beneficial or not. If brutorknight were to test the same spoiler with two slightly different meshes, how much would the results change? If the mesh is too coarse, I imagine that the results could change by X%. Therefore, should a mesh study should performed on each design to make sure the results have really converged.

 

So here is my real suggestion. If the relative difference between spoiler designs is suitable, my suggestion would be to include all of the spoiler designs in one model -- if that is possible. Then each study would change certain parts from solid to air. (Think of a 2D model. Parts of the different spoiler designs would overlap. Other parts would be unique. If all of the designs were overlaid, there would be a bunch of different "parts" which could be changed between solid and air to get whichever spoiler design was needed for a given study.)

 

Since the mesh would be the same in all studies (other than what is solid and what is air), the inaccuracies may be similar in all studies. So even though it would be hard to say with confidence that the pressure changes from X to Y psi between two designs, it may be reasonable to say that the pressure changes by (1-Y/X)% between the two designs.

 

Just a thought.

Message 4 of 5
Jon.Wilde
in reply to: AstroJohnPE

Hi John,

 

It might be wise to utilise the mesh adaption for each study, this should minimise error.

 

Personally (depending how many models there are) I would utilise the design study manager and run multiple designs side by side, with a single spoiler in each. That way the model may only need to be set up once. A mesh region might be useful here.

 

To really capture compariative designs though, a 2D approach might be more suitable. Once the level of mesh (which will be high) is ascertained, this can be applied to the 3D model if possible.

 

I see what you are saying though and that is usually how we do approach initial studies. It depends on the focus, if we just want a relative comparison or need to lean more towards accuracy.

 

Thanks for the input 🙂

Message 5 of 5
brutorknight
in reply to: brutorknight

Thank you all for confirming my testing conditions. I draw the air volume box around my model in inventor and set up inlet velocity at lets say 65 mph and 0 pressure at outlet.

Thanks again

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