Quote:
Originally Posted by autogyro
Oh, good grief! I suppose everybody on this thread has a hobby horse to ride, so I'll saddle up too.
At least in my copy of Hucho (chapter 4) he mentions that there are other basic body shapes that surpass the Klemperer/Gottingen shape form the 20's, specifically the Morelli shape from 1976. (I actually have the paper)
That's not my point. A big part of chapter 4 is " detail optimization". This is where the rubber meets the road, literally. Drag caused by wheel turbulence is a huge factor, and has only recently begun to be modeled and tested with any sophistication. Trailing wheel vortices from the rear wheels alone can consume 5kW. (Morelli again)
Likewise cooling system drag.
Hucho's answer, and mine, is to test, and test again, using reasonably sized (30%) models to get reasonable Reynolds numbers. My belief is that you don't need the MIRA wind tunnel to do this.
Automotive body engineering - Roof Rack "Wind Tunnel": A Naive Idea?
Sure, play with all the basic Shapes you want, but the devil is in the Detail Optimization. |
*If you look at a transverse section slice of the Morrelli shape, the degree of diffuser angle necessary for that form to work,and necessary ground clearance,you may wonder if this 'template' would lend itself to modifications to a conventional passenger car.
*The 'Template' encompasses full wheel skirts at all four wheels and delivers Cd 0.13.
*When detail optimization of the wheels is performed drag potential rises to sub-Cd 0.1.
Walter Korff gave us the lowest drag form cooling system as of 1963.That technology has been available to all ever since.A no-brainer.
*Hucho says that detail optimization can only get you so far.
*Hucho also says that the only way to lower drag is the 'Template.'
*The basic shape for the 'Template' is Hucho's.Some of the references are listed in Part-C of the 'Template thread.
*My belief is that enough wind tunnel testing has already been done.
*Low-drag shapes are off-the-shelf technology.There are no mysteries regarding low drag.
*People appear to suffer from the tyranny of unity.It's impossible for them to believe that there can be a single solution to low drag.
* And it smacks of intellectual dishonesty when high-efficiency is presumed for sub-mariners going aboard an Akula,kayakers entering white-water,travelers boarding a commercial airliner,or a perrigrine falcon departing from a stoop at 280 mph,but then this same 'technology' couldn't possibly impact their road vehicle.