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Old   April 5, 2005, 03:45
Default aerodynamic analysis
  #1
wilson
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Hi guys

I am doing aerodynamic analysis of a small size car. Now I have put the car model in a rectangular box for simulation just like a wind tunnel testing experiment. But I am still uncertain about the distance between the wall of the tunnel and the car that should be kept in order to obtain no boundary effect of the wall. I read the documentation in which it is said to keep good distance between the wall and the car but nothing specific is mentioned. The wall boundary condition that I am setting is "free slip". if anyone can tell me a numerical ratio or a thumb rule for this problem.

regards wilson
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Old   April 5, 2005, 19:26
Default Re: aerodynamic analysis
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Glenn Horrocks
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Hi,

Do a sensitivity analysis and work it out. I don't work in the field so I don't know a rule of thumb.

Glenn Horrocks
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Old   April 6, 2005, 03:45
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wilson
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hi glenn can u elaborate on sensitivity analysis. if i am not wrong u mean to say that i increase or decrease the distance and check any effect occuring.

regards wilson
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Old   April 6, 2005, 05:40
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Akin
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Look in the Ahmed body Model.
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Old   April 6, 2005, 05:42
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Michael Bo
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Rule of thumb: Only up to 5% of the cross section area should be occupied by the car.
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Old   April 6, 2005, 18:34
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Glenn Horrocks
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Hi Wilson,

That is correct. Even if you use a rule of thumb you should check the sensitivity for your model, so you know the level of accuracy you can expect from your model.

Glenn Horrocks
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Old   April 29, 2005, 11:25
Default Re: aerodynamic analysis
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Marco Melo
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Hi Wilson!

My Engineering thesis was the simulation of the FSAE car of my university, look you have to do like Micheal said. The cross section area of the car has to be 5-10 % of the cross section of the tunnel. I also put free slip for the upper surfaces and i put the bottom surface to move at the car speed. I'd like to know if you already have values of the aerodynamisc coefficient, so we can compare because we had problems with the magnitude.

Regards Wilson!

PS: my email adress is marcoamelo@usb.ve
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