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  1. Paul6

    GROUND EFFECTS DIFFUSERS DATA

    Correction, I meant expansion ratio.
  2. Paul6

    GROUND EFFECTS DIFFUSERS DATA

    Mike, I think you're right. It is very likely to be a dimension. From the diagram on page 40, the only important missing dimension is the height of the diffuser exit. If this were to be the mysterious "d", h/d would be the inverse of the expansion ration, a very important factor. But why the...
  3. Paul6

    GROUND EFFECTS DIFFUSERS DATA

    I’ve searched the internet for a long time for hard data on ground effects diffuser design. Finally I found what I thought was a gold mine: Ground Effects Aerodynamics of Race Cars. SITE:http://eprints.soton.ac.uk/42969/1/GetPDFServlet.pdf Actually it’s a review of many ground effects...
  4. Paul6

    How much extra lift can I expect installing gourney flap?

    allblowdup, Are you running endplates on your wing? If not, what you have is a wing with a very poor Aspect Ratio (AR=Span/Chord). Your AR is about 1.3 which means the lift induced drag will be nearly as great as the lift (you reported 28 lbs. to 50 lbs.) You can do much better than...
  5. Paul6

    Automotive Diffuser Questions

    Yes, your wing looks fine, although mounted a bit close to the rear deck. Perhaps you've duplicated the raised front floor inlet as seen on recent Le Mans cars. That was a rule introduced by the organizers to REDUCE downforce and improve safety at very high speeds. If you go from a 2" high...
  6. Paul6

    Automotive Diffuser Questions

    1. Yes, you need to make the diffuser as long as possible & practical. Katz’s data shows that a wing perched completely on top of a street car body still makes a surprising amount of improvement in diffuser downforce generation. Of course, much will depend on whether your wing is actually...
  7. Paul6

    Automotive Diffuser Questions

    bensalasko, You really need to get a copy of Joe Katz, Race Car Aerodynamics. It answers all your questions plus a bunch more you should be asking. You have the wing/diffuser relationship backwards. Ground effect systems, of which the diffuser is the final piece, are far more efficient...
  8. Paul6

    Lift curve slope for NACA0012 at low Re

    The low Re data you seek is available at: http://naca.central.cranfield.ac.uk/reports/1937/naca-report-586.pdf Data was gathered in their variable density tunnel. Their lowest Re is 42,000. Lacking is any data at Re=0 I would imagine the stall characteristic there is quite nasty, altho...
  9. Paul6

    Lift curve slope for NACA0012 at low Re

    I'm fairly sure you'll find what you're looking for here: http://www.ae.uiuc.edu/m-selig/ads.html An outstanding university group who specialize in model aircraft airfoils - 1550 of them! The data is available for sale in booklets and the data should be reliable. It's backed up by tests at...
  10. Paul6

    Would holes in flat surface increase net pressure?

    Correction: The actual title of the book is Fluid Dynamic Drag by Dr. Sighard F. Hoerner. Very readable and nearly comprehensive.
  11. Paul6

    Would holes in flat surface increase net pressure?

    It is tempting to rely on intuition, but before you do, you might want to look at previous uses of this hole cutting technique. In WWII US dive bombers used dive flaps to slow their descent toward target ships, providing more time to correct their trajectory before releasing their bombs. The...
  12. Paul6

    Race Car End Plate-cutout vs full

    The answer to your question is to be found on p. 62 of the latest RACE TECH magazine, No. 49. In short, the only time downforce is of interest in a race car is when it is turning and pulling high lateral G-forces. This results in a yaw of 6-8° depending on the tires and other factors. Solid...
  13. Paul6

    Blow Augmented Diffuser

    As i278 suggests, in the simplest form: think of it as an unusually shaped wing with a Fowler flap running inverted just above the ground. The back edge of the flap continues into the bodywork. The bottom flow of the flap is ducted thru to points outside the car. Is Matt suggesting there...
  14. Paul6

    Blow Augmented Diffuser

    On an enclosed body race car I am designing a diffuser for ground effects. Because of the bodywork, there is no source of high speed flowing over the trailing edge of the diffuser. This is an important feature for entraining air out of diffusers and enhancing the flow. I plan on introducing...

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