Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post

aerohead · 03-26-2011, 04:38 PM

your reading should have revealed that your model cannot exceed 5% of the cross-sectional area of the tunnels test-section.
So 5% of your garage test-section will define your model size.
Verisimilitude is your next challenge.Based on your models frontal area, the test-section air velocity would need to be such that you achieved at least the same Reynolds number as say at 20mph at full-scale.
If say you had a 1/4-scale model,you'd need a minimum of 80 mph air in the test-section to get your Reynolds number.
For a 1/4 model of a 22 sq ft frontal area car you'd need a 110 sq ft section.
That would require 774,400 cubic-feet per minute of air.
It would get loud and expensive.
The tunnel at Texas Tech has only a nozzle of around 3X4 feet,@ 80 mph and requires a 50-hp motor ( 37,300 Watts ) which exceeds the typical electrical service for a home.
And my experience is that models cost more to build than a real car.

03-26-2011, 04:38 PM	#32 (permalink)
aerohead Master EcoModder Join Date: Jan 2008 Location: Sanger,Texas,U.S.A. Posts: 16,312 Thanks: 24,439 Thanked 7,386 Times in 4,783 Posts	tunnel your reading should have revealed that your model cannot exceed 5% of the cross-sectional area of the tunnels test-section. So 5% of your garage test-section will define your model size. Verisimilitude is your next challenge.Based on your models frontal area, the test-section air velocity would need to be such that you achieved at least the same Reynolds number as say at 20mph at full-scale. If say you had a 1/4-scale model,you'd need a minimum of 80 mph air in the test-section to get your Reynolds number. For a 1/4 model of a 22 sq ft frontal area car you'd need a 110 sq ft section. That would require 774,400 cubic-feet per minute of air. It would get loud and expensive. The tunnel at Texas Tech has only a nozzle of around 3X4 feet,@ 80 mph and requires a 50-hp motor ( 37,300 Watts ) which exceeds the typical electrical service for a home. And my experience is that models cost more to build than a real car.