[freebeard]

http://ecomodder.com/forum/showthrea...low-34134.html

Originally Posted by aerohead

I don't have my work book with me,nor calculator but here are some considerations:
* a 1/10-scale passenger car tunnel would require a test section cross-sectional area of 4-meters-square minimum,to counter blockage effects.
*a minimum test section airspeed would be 200-mph to reach a critical Reynolds number/turbulent boundary layer.(dynamic similarity).
*at 200-mph,we have 17,600 feet/minute,and with 44-sq-ft of cross-sectional area,we get 774,400-Cubic Feet per Minute (CFM).
*high-speed tunnels have boundary layer thickness issues,and the ground borad must be elevated above the boundary layer,or suctioned off the flooor of the tunnel,as in the real world,the ground has no boundary layer.
*you'd need help from an air conditioning company to determine wall friction coefficients/losses,and total static pressure requirements to determine net horsepower for the air mover(s).
*Alan Pope published a great book on Low Speed Wind Tunnel Design.It's worth an inter-library loan if your school doesn't have it.
*small-scale model features cannot be successfully investigated except in near-full-scale CFD or wind tunnel.(Ferrari is spending 100-hours just to refine a single spoiler in their tunnel,at a cost of $4,000 (US)/hour.[$400,000]
*Texas Tech had a small tunnel and did 1/12th-scale work.With 50-hp (electric) they could get an 80-mph section velocity,not enough for a TBL Reynolds number,and they had to back things up in a water tow tank.

aerohead hasn't posted in a week, he's busy prepping for the A2 wind tunnel. The quote is from a similar thread.

I see elsewhere that blockage should not exceed 5%.