Water Tunnel Flow Visualizations

[Bill in Houston]

Originally Posted by red91sit

I used to dream of building one of these in my room haha, but decided the lack of compressability would make it not so worth while?

Like Trebuchet03 said, the lack of compressability is no big thing. If you want to satisfy yourself, get an aeronautics textbook and see what kind of speeds they are talking about before they start talking about a compressability factor, or have some sort of integration applied to the density, or something like that.

[Nerds laugh at me]

I have used a Shop-Vac and 2" yarn tufts to visualize flow on a full size car.

The problem is the air become stagnant very quickly, so you cannot use it for areas larger than around a foot.
Testing on the front and sides of the car was useful, but there is not enough velocity to test the areas around the back of the car.

Tuft testing the car on the road showed that the ShopVac testing was accurate.

I have thought of creating a wind tunnel using a ShopVac and an enclosed length of PVC pipe.
The Shop Vac would be sealed so that one side of the pipe would blow , and the other suck ) I still have to find a model of my car ( A 1993 Civic hatchback ) that is a useable scale though. So far all that I have found is a 1:24 madel.

As far as using water as a visualization tool, why not just take a length of pipe and a model car into the pool with you the next time that you go swimming ?
If you unhook the pool pump and attach it so that it cycles the flow back and forth, it seems like it could be useful.

[Nerds laugh at me]

Is that pink thing on the third of fourth picture .... what I think it is ????
( It seems to be slightly arroused in the picture that follows. )

[GasSavers_RoadWarrior]

I've been trying to figure something out with my bathtub. I'm thinking a weight and pulley arrangement to draw a model through water a measured distance in a measured time would make for some useful data. Also might be possible to find some neutral buoyancy colored beads, so one could get some flow visualisation out of it too. Can't think of a convenient material to make the models in though... or scale, 1:43 is a tad small still, 1:20 would be more like it... but then there's issues with the bath being deep enough....

I for one won't worry tooooo much about the compressibilty of air compared to water until I have my speedo marked out in Mach numbers... (i.e. worry about that when you're planning 350mph and faster)

[GasSavers_Pete]

Peakster,
You may have more success in finding a model of the Suzuki Swift the Geo was based on.
Several appeared in a quick Google search.

Cheers , Pete.