lamnar boundary layer on vehicles? 2

[rberns2]

Hello,
I'm wondering if laminar boundary layers occur on vehicle bodies. Gernerally Reynolds numbers in scale wind tunnels are relatively high. I know that there are stagnation points and areas of high pressure hence low speed, where theoretically boundary layers need to build up again.
Is the effect of droping drag over increasing Reynolds due to the fact that laminar boundary layer changes to turbulent boundary and hence separation occurs further downstream?

 

[GregLocock]

The front end design of cars is not conducive to laminar flow. With careful attention to detail, and appropriate choice of shape, a car sized vehicle can have laminar flow back to 40-60% of its length, at 100 kph. However, the shape is not a practical one.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[reidh]

I remember seeing an article sometime ago regarding the shape a car would have to be to have a full laminar flow and allow a driver to sit in the front seat. I think the car length was something like 75 feet long. It basically was a teardrop shape. Like Greg said, not practical, but interesting.

-Reidh

 

[PLeon]

This is a dead thread but I remembered the Mercedes' fish-inspired car with an impressive Cd of just 0.19.

http://www.cnn.com/2007/TECH/03/08/cars.fish.popsci/index.html

 

[timo917]

I know this thing is long dead but I read a great explanation of hows and ways that pretain to Reynolds numbers at the web site for Dreese software. John Dreese gives a great laymans explanation (with mathamatical forms.) as to airfoil efficiency. He has an e-mail contact address and got back to me with my question although I dont feel that I should leave it here.
Go to DreeseCode software and its listed.
I believe they produce airflow modelling software or something. He seemed very fluent in being able to answer the question possibly

 

[miller64917]

Wow... Pleon that Merc is crazy looking, lol.

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