Quote:
Originally Posted by freebeard
Are your Photobucket albums public? (Answered my own question: Yes)
Uniform proximity in these examples. What is the distance, some % of the width?
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Paul Jaray discovered the effect and published about it in 1922.He found that when you brought an airship body down into ground proximity its drag would rise,reaching a maximum of 2X when pushed halfway into the ground,creating the half-body.
Walter lay took an airship body of Cd 0.04 and found that at a standard automotive ground clearance the Cd would be 0.08,or 2X.
Ludwig Prandtl and Edmund Rumpler continued the research,and later Stollery got into it as well as Rolf Buchheim,one of Hucho's associates at VW.
Hucho published a drag table illustrating the drag deviation as a function of ground clearance and uses it to flesh out the concept of "Effective-Bluffness or "Effective -Fineness Ratio" as it's one of the most important concepts in road vehicle aerodynamics.
I tried to illustrate the concept at the A.S.Template Part-A,B,C,maybe D.
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Since pictures are working better than text,I'll try 'n get that posted unless someone else with Hucho's book would like to do that post.
At the time of Kamm and Koenig-Fachsenfeld's research at the FKFS they were using 25 cm as a 'standard' automotive ground clearance.Their 'reproduction' of Lay's 1933 model suggests that 25cm was kinda what Lay used and got 2X drag increase.No dimensions are given for Jaray's 'pumpkin seed tested by Klemperer.It would be straight-forward to do a non-dimensional G.C. as a function of % overall height as a reference datum.
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Essentially though,whatever ground clearance we have on our 'store-bought' cars is what we're gonna have to work with.
If we
mirror-image our cars and look at their effective bluffness,we can compare to the relatively 'ideal' L/D= 2.5 in reflection,or L/H = 5 as the half-body.
Let's get the image going!
