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Old 07-31-2019, 02:35 PM   #97 (permalink)
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Originally Posted by Snax View Post
Challenge accepted!

Seriously though, I didn't realize the order of magnitude was so great. Time to think 'water' perhaps.
Yes,water is 833-X more dense than air.You can hit critical Reynolds number at very low velocity.
Texas Tech used to have two water tunnels.One was for 1/24th-scale models,where they just injected food coloring to image the flow.No drag measurements.
They also had a large water tank with overhead gantry-crane,providing a multi-axis strain-gauge sting,onto which an 1/8th scale model was towed along the floor of the tank,and the lift-drag-pitch-roll data transmitted through the sting to a computer.
The model of the Ford Taurus they had when I visited in 1991 cost them $68,000.Ouch!
Daimler's Mecedes-Benz has also used this technique.
Another technique is a water table,used for 2-D flow only.Blocks of wood are band-sawed into a side profile of the shape of interest,and placed onto and weighted down to the outflow table,which has laminar flow.Food coloring allows flow visualization.No measurements though.When the water gets cloudy from the coloring,you throw in a little bleach,and it clears right up.
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