Yesterday I received my copy of the March issue of Racecar Engineering and was very pleased to read the first of a new series of articles dealing with aerodynamics. If you are not a subscriber and wish to read the article, rush out to your nearest Barnes & Noble to purchase the magazine.
The new series is written by noted race car aerodynamics designer and author Simon McBeath, and the first installment is sub-titled How is downforce is generated by a profiled underbody? Like his books, this article can be read by the casual reader without reference to the equations, yet there is enough math in there to keep engineering types entertained as well. Anyone interested in tunnels should give this article a good read.
Anyway, McBeath compares classical Bernoulli Theory with the results of computational fluid dynamics on a range of tunnel configurations (much like Tudor Minor did in the Ralt Tunnels thread, only with a finer grid), and I was surprised to read that much lower diffuser slopes than used in the Ralt appear to be optimal. This is very good news for those desiring to build their own tunnels, as it will allow much more compact designs to function as well as taller designs.
McBeath's studies conclude that diffuser slopes as low as 6 degrees can yield optimal results. That got me to thinking about the slope of the Ralt tunnels, so I took a quick look at the coordinates file I shared with you last month. The Ralt's tunnels raise approximately 9.5 inches from the 25" point to the 75" point, an 11-degree slope -- right where McBeath expects separation to occur. Hmm, that's certainly useful information. I hope you get a chance to read about it!
Cheers! Stan Clayton
The new series is written by noted race car aerodynamics designer and author Simon McBeath, and the first installment is sub-titled How is downforce is generated by a profiled underbody? Like his books, this article can be read by the casual reader without reference to the equations, yet there is enough math in there to keep engineering types entertained as well. Anyone interested in tunnels should give this article a good read.
Anyway, McBeath compares classical Bernoulli Theory with the results of computational fluid dynamics on a range of tunnel configurations (much like Tudor Minor did in the Ralt Tunnels thread, only with a finer grid), and I was surprised to read that much lower diffuser slopes than used in the Ralt appear to be optimal. This is very good news for those desiring to build their own tunnels, as it will allow much more compact designs to function as well as taller designs.
McBeath's studies conclude that diffuser slopes as low as 6 degrees can yield optimal results. That got me to thinking about the slope of the Ralt tunnels, so I took a quick look at the coordinates file I shared with you last month. The Ralt's tunnels raise approximately 9.5 inches from the 25" point to the 75" point, an 11-degree slope -- right where McBeath expects separation to occur. Hmm, that's certainly useful information. I hope you get a chance to read about it!
Cheers! Stan Clayton

















