Hello guys! i am very very new to Arduino, but the stuff that can be made from this is uber fantastic. So i am doing a project that involves making a sensor that can detect water turbulence, and once detected will send a signal to another arduino some distance away that will trigger a bubble machine to turn on and blow bubbles. What types of devices should i be looking for? Is there a project here that is similar to this one?
making a sensor that can detect water turbulence
That is very very difficult, if not impossible.
The only way I can think of is to have some sort of dye and a web cam looking at the flow and doing some image analysis on it.
Some kind of Schlieren imaging?
Tricky though.
Interesting but super complicated method - Water turbulence detector - The United States of America as represented by the Secretary of the Navy
cool read though. check out the pdf
Having had another think about it, how about a sensor that consists of a ribbon of thin metallised mylar film, anchored at one position with a thread to the floor.
In linear flow this would align itself with the flow. However in turbulent flow this would wriggle and twist. You detect this by bouncing light off it and looking at the reflection. If the light returned is a steady value the it is linear flow, if the signal returned is rapidly varying then you have turbulent flow. It's still not easy but might just work.
You can try direct a LED+LDR to the water surface to detect rapid light changes.
Well you get can get turbulent flow without affecting the surface of the fluid.
The simple answer would be - if the bubble machine is running you have turbulence, if not - you don't. 
Then again you would not need the "turbulence sensor" in the first place - so perhaps you need to explain in more detail what you plan to build (size of pool/bowl/tank, distance from source to sense etc.).
E.g. if you want to quantify the effect of the "bubble machine" at some distance from the source, then some sort of flow meter may be appropriate.
wow! thanks for all the replies everyone!
So in terms of size and whatnot, we plan to attach the sensor in some way to a canal wall which is about 50 to200 feet in width. From there, turbulence will be detected and the arduino will send a signal to a bubble machine that is about 7 feet away to go off. My thoughts on this was to use a sort of "communication system" between each arduino, in that perhaps whenever the canal arduino LED light turns on from water turbulence, the second arduino will see the light and thus act as a battery to turn on the bubble machine(the second arduino would be in the bubble machine itself).
a canal
Oh! Dirty water!
Even harder. ;D
If it is surface turbulence, then I'd probably go with a simple optical method.
Focus on a laser spot or line and try to get some measure of scatter.
If I understand this correctly, you want to attach a sensor to the wall of a 50-100 foot wide canal and determine if the flow along the wall is laminar or turbulent.
What do you mean by "Laminar" and "Turbulent"? Do you mean these as a relative terms or are you actually going to calculate the Reynolds number for flow in a channel and base it off that. Im curious because what would cause the conditions in a canal that large to change?
As far as communicating between the two arduinos. The easiest way would be to connect them with a wire if its only 7 feet away, however if this is not possible you could look into a simple RF transmitter/receiver pair or xbee if there is a lot of noise in your environment.
If we could get some more info on what you are actually trying to measure we could probably come up with some more ideas.
Why do you need the second Arduino, the first one could just as easily turn on a bubble machine.
So it's a canal!! :o
How to make something very very hard into something impossible. I had envisaged flow in a small fish tank or water feed to a fish tank.
So what is the normal flow rate and what does it get up to when it is turbulent? Is there anything else you haven't been telling us like are there fish in the canal or are there barges trundling past?
Hello haukmoon269,
Looks like you´re controling eutrofization rates on the tank? That´s interesting.. Well it´s interesting in any case 
Im not sure if it can be applied but one idea consist of measuring the water velocity at one point of the canal. For a defined section at some point of the canal maybe there´s a correlation between the velocity range of water where the flux mantain it´s laminar flow? If so you can record values from empiric tests. Considering little differences upon different liquid density?
If it can be apllied so the solution may be easy.
Hope it helps and sorry if english here is not the best.
Regards,
Rodrigo
ok so perhaps i should further explain
ok so these canals have water boats that zip by and dock, causing boat wakes and thus undulations (and therefore turbulence). So lets imagine a still canal (kinda not normal but for example purposes let's run with it ) and a motor boat will come by. the wake produced by this boat cause large wave undulations. Now my advisor suggested we actually get a sensor that will measure these undulations. and by what i am seeing, its not gonna be that easy :P. But i think a good idea would be to have some sort of sensor or device that can determine light bouncing off the waves generated. (and i know some of you mentioned that already thanks so much!)....the purpose of this project is to HIGHLIGHT the fact that boats cause undulations which in turn corrode canal walls. THis is highlighted by a bubble machine.
It's always the way. It turns out you do not want to measure turbulent flow at all but the wake from a canal barge.
And the bubbles are just some sort of warning. Therefore you need to measure at degree of wake as I assume they are being encouraged to drive slower or further away from the bank.
So apart from the laser idea, which is good, you could consider a bobbing float and wire arrangement. Or a float turning a pot or optical encoder.
that is the idea more or less!
actually going with the bobbing float idea...is there a way to put a motion sensor in there so that at a certain degree of motion, the bob will send a signal to arduino in the bubble machine (on land about 7 feet away) via xbee?
So yeah "It's always the way. It turns out you do not want to measure turbulent flow at all but the wake from a canal barge. "
For this i have some idea that should work, i dont know the name of this in english so i made this simple scheme: http://www.minasambiente.com.br/sensor.jpg
Idea is: The moving contacts do not move one against the other but moves in relation of the fixed contact. The fixed contact do not move in relation of the axis but the moving ones will. Installed inside a floating thing disrupting "peace" in water surface will make the moving contacts to touch the fixed one (on the diagram), causing some shortcut you can use to trigger anything. You can set the sensibilty of the device by changing it´s size and natural distance from the contacts. Washing machines usually uses this type of "thing" to decide if it´s shaking to much.
Hope it helps,
Rodrigo
that is quite interesting actually! so the idea is the two outer arms will move with the water and then when a boat actually comes by and produces wakes, itll be strong enough to make the arms touch the fixed one which will trigger stuff to happen.
very very interesting!
It actually works if you design the float, the sensor, and distribute weight the right way on the float against the "size" of the waves.
This is a forum but looks like a chat ;D
Salute