Quote:
Originally Posted by khafra
According to my calculations, based on stuff I just looked up all over the internet, if 20mph air at 1:1 scale is enough to observe the relevant turbulence, 30mph water will work at 1:18 scale; a scale at which models of most of our cars are widely and cheaply available. That takes like 40,000gph at a 6 inch by 6 inch cross section, so a pump would be pretty expensive. A powerboat would probably be cheaper, although whatever cord you dragged your model by and the boat's wake would keep the water pretty turbulent.
But if you could hoist a lot of water 30 feet in the air, and get a few seconds of flow at the correct speed at ground level--assuming you could keep the flow laminar and drag-free--you'd have the correct ratio. The challenge, then, would be keeping the model from being immediately pulverized.
We don't have any waterfalls here in Florida, because we don't have any elevation changes. Does anybody who lives near one wanna give this a try?
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water has 833X the density of water so small models are just fine under water.The trick is how you 'work' inside the test section.
A model can be drilled and tapped with dye outlets for food coloring joined to a common reservoir outside the tunnel.The colorant ejection velocity must be matched to the flow velocity to prevent a jet.Once calibrated,selective ports can be selected for release and observing/photography.When the water becomes saturated with colorant,chlorine bleach is injected to clear up the water.
------------------------------------------------------------------------- An underwater tow tank can also be constructed in which models are towed underwater from a traveling overhead crane ( as at the US NAVY David Taylor Tow Basin in Maryland) .Dye injection and tufts can be used for flow imaging.