Repeating Water Tunnel Studies in Wind Tunnel

[doubled]

Is there any significance in repeating a water tunnel study in a wind tunnel?
If so, would the results be publishable or would it just be considered repetition of a previously published water tunnel study?

 

[boneh3ad]

There really is no significance if both flows are incompressible and at the same Reynolds number. All it really means is that the air really was incompressible. The main reason you would want to use a water tunnel would be if you need to reach a flow regime that you were simply unable to achieve for one reason or another in air or if you for some reason needed it to be incredibly easy to do PIV or various flow visualization techniques or something along those lines. Otherwise they are essentially interchangeable in most cases where they can both be used.

 

[doubled]

There really is no significance if both flows are incompressible and at the same Reynolds number. All it really means is that the air really was incompressible. The main reason you would want to use a water tunnel would be if you need to reach a flow regime that you were simply unable to achieve for one reason or another in air or if you for some reason needed it to be incredibly easy to do PIV or various flow visualization techniques or something along those lines. Otherwise they are essentially interchangeable in most cases where they can both be used.

Btw, why are flow visualization techniques easier in water tunnels?

 

[boneh3ad]

Do you watch Mythbusters? Have you seen them inject neutrally buoyant dye into the water tunnel and watch it flow over their models? You can't really do that with air. Nothing visible is neutrally buoyant in air like that.

 

[doubled]

Do you watch Mythbusters? Have you seen them inject neutrally buoyant dye into the water tunnel and watch it flow over their models? You can't really do that with air. Nothing visible is neutrally buoyant in air like that.

I don't watch Mythbusters.
Oh I see. I've never tried dye visualization. Have you tried smoke visualization using the smoke-wire technique in Lex Smits' Flow Visualization book? I presume that can only be done in wind tunnels?

 

[boneh3ad]

Sure I've used a smoke wire, which is all well and good, but it isn't truly neutrally buoyant so it doesn't work below a certain speed. The smoke particles will just settle.

Of course on the contrary, things like naphthalene sublimation only work in air flow. I'd imagine that temperature- and pressure-sensitive paints work in water, but I've never seen or heard of it being done.

Really, the reason to use water is if you need the match conditions that water can give you. Same goes for air. If you application would work in either, use the one that gives you the best chance of making the measurements you want.