1:24 water tunnel for flow visualization
 

I just started to fabricate my own water tunnel. Plan is to make the tunnel so big that you can test 1:24 truck.

Truck main dimensions are 100mm (W) x 150mm (H) Tunnel dimensions will be 5x those -->500x750mm.

Trucks length is about 700mm
What is enough length for this tunnel?
Is that turn too tigth?

DIY Water tunnel.jpg - Windows Live

All pictures, datasheets and videos of working water tunnels are welcome. There will be huge acryl window to see the test sections flow properly

That straight section is 1260mm long at the moment. That is enough for small car but is it enough for truck and trailer which was that 700mm long? Project will continue on wednesday ;).
http://cid-acb1f13bac776768.photos.l...comparison.jpg

How high is the water going to be in the tunnel ?

If you're going to fill it up to anywhere near the height of these side boards, the seams are going to pop unless you SERIOUSLY strengthen them.
Some nails or screws and glue ain't gonna do the job.

Look into angled steel reinforcement at the bottom corners, with steel straps keeping the tops properly spaced.

750mm high if the truck is on testing. I will add glasfibre layers inside and also put more streghtening ribs where I think it will need them.

A friend of mine has built a temporary 2.5 m3 wooden fish tank to relocate his fish.
He's the kind who'd rather put in an extra nail, but despite looking pretty sturdy to me, it's already coming apart at the seams.

Since no better info has come conserning the length it will be at the first tunnel that 1260mm long. Inner corners are done and also the reinforcement glasfiber layers to hold the corners and keep the water out of the seams.
DIY Water tunnel inner corners.jpg - Windows Live

Tomorrow target is to get outer corners and ready glasfiber layer to whole inside so I can add water. Still wondering will I buy boat electric motor or build similar wheel like here any ideas which would be better? that wheel is no problem but how to be able to control rotating speed is a problem and also at what speed :/.

http://www.youtube.com/watch?v=L0ki-FtPYrA

Costs so far:
Glues 25€
bolts 20€
wood 15€
glasfibers stuff 15€

time=priceless :D.

An off-the-wall suggestion here, but what about using water flow from a river in a water tunnel? It's an endless supply of fast moving water. Use a small stream and it'll be steeper (easier to get onto the bank) and cleaner.

Speed control should be fine with an electric motor

In the film the water is flowing rather slowly when you see the flow tank - until the aero shapes are shown, then the flow is faster, though I think these are sped up after recording.

Wouldn't the Reynolds number combined with the viscosity determine your water flow speed range ?

Myth-Busters
 

Vekke,did you happen to catch the Myth-Busters episode in which they tested pickups for tailgate up/down fuel economy?
In that episode they constructed a simple 'atmospheric' open-top water tunnel which looked akin to a horse race track.
A 24-VDC electric trolling motor was used to move the water.
A clear Plex window allowed viewing of the model pickup as the water flowed by.
And they simply put something like breakfast cereal in the water to reveal what the flow was doing in proximity to the model.
With the grain in the water you could clearly discern the open pickup truck bed 3-D vorticity as is depicted in CFD images.
Dirt simple technology!

MetroMPG has posted the video here:

http://ecomodder.com/forum/showthrea...html#post13237

My current tank is looking 90% same. They didint have any vanes at the end of the tank and flow was turbulent. I will anyway build this tank ready and try get the flow under control.

I can see I'm not the only one that thinks the idea of having a scale model wind tunnel in their home is the coolest ecomodding toy one can own! :)

My wife does not think that way, but I do.

water 'table'
 

This would be a water 'table',rather than a wasserkanal/water tunnel.
Your flows would be only 2-dimensional and it would be impossible to evaluate wake flow.
You can analyze center-line body flow though.
Texas Tech has a water table.They pump water to an upper reservoir where the water bleeds through a porous media onto a slightly slanted backlit glass sluice.The water flows down by gravity.Simple!

Is that not 3D if my water "table" is 750mm deep/high? Mythbusters version was just like mine...

Aerohead was referring to the video. These days, they still use setups like that, but with a transparent bottom, and they image the light refracted through. It offers a decent way of approximating compressible flows in 2d, like those that happen inside a jet engine.

If the water's 750mm deep, and the model and flow speed are scaled appropriately to that, it'll be a 3d simulation.

750mm
 

Vekke,750mm sounds like a good direction.With the heat we're having here I'd be tempted to 'dive in'.
Wind tunnels attempt to limit the frontal area of the model to 4-5% of the test section cross-sectional area.This might be a good general rule for any tunnel regardless of 'fluid'.
Alan Pope,in his book,was pretty adamant about blockage ratios.
If you're around that figure you should have great results.
I'll look forward to future posts.Great project!

I want to make test tank , I have a 3ft long empty fish tank to test in , I am thinking to use it as the video test tank , with water flowing into and out of the tank so the dye leaves the tank water after being flowed. This off the top of my head so the plan is in its infancy ..

edit: My tank theory seems sound , here is test tank set up done by a university aerospace department -
http://elearning.eng.cu.edu.eg/aeros...gprojects&id=3



a tester testing in his tank
https://www.youtube.com/watch?v=wm_hX4QpfP4

3ft long?

This was my proposal for a water tunnel, using paddle wheels to reduce turbulence. It wasn't very well received.

http://ecomodder.com/forum/member-fr...6-12-26-10.png

It could work with two, or only one wheel. Then you could put a window in the side of it.

I think if Vekke does not give his brain a rest the heat generated is going to melt the polar ice cap. He's pretty close.

How about an inclined plain using gravity to keep turbulence low, or a vertical tube with some form of flow control to a horizontal viewpoint. Might be better for it to be circular, maybe a piece of plexiglass that could be curved into a tube.

I think I burned my brain out trying to fiugure the right way to spell plain (plane?) in this context.

regards
Mech

You may be right. :)

According to To Predict Turbulence, Just Count the Puffs - Issue 15: Turbulence - Nautilus 'puffs' are an analog to the virtual quantum particles that presage quarks.

This suggests that a test section coated on the inside with some hydrophobic material might supress the puffs that lead to turbulence, reducing the necessary cross-section.

To me it looks like those paddle wheels would block the flow of water, even when they were moving.

http://upload.wikimedia.org/wikipedi...wheeler%29.jpg

If the paddles were tightly fitted against the top, bottom and dividing wall I think it would eliminate the [edge][wing-tip] effects of a paddle or propeller blade moving in open water.