How Big Can You Go?

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How Big Can You Go?

Post  firemandave on Thu Apr 09, 2015 6:57 am

I have seen and started to research how to make a lighted laminar nozzle. My question is how large of a nozzle can I make? I am a Captain on a fireboat and my original quest was to light up the water coming out of the deck monitor but this flow is to turbulent. Is it possible to make a nozzle that will give me a 2" laminar flow? Water pressure or quantity is not a problem. At larger volumes of water can I use 1/2" pvc pipe as my interior tubes instead of straws? Any insight will be greatly appreciated.

Thanks,
Dave

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Re: How Big Can You Go?

Post  Ike on Sun Apr 12, 2015 1:49 pm

That would be crazy indeed!

My first step would be to play around with the reynolds number for your build. Check out this blog post I wrote a while ago and scroll down to the laminar maths section: http://scuttlebots.com/2014/06/17/laminar-fountains-what-are-they/

That should get you in the ball park of whether your build parameters will work. If you have questions post your math here and I can lend a hand. Disclaimer: real world issues not taken in to account in the equation always play a part.

Second, gives some thought to a few of these issues and how you will deal with them at scale:
1) The less turbulent the water input the better. Air chamber dampers prior to your fountain can help but you'll need big ones for that much flow.
2) The pressure in the fountain needs to be as evenly distributed as possible across the diameter of the outside tube. If some of the "straws" see higher pressure than others then the water will flow faster in those and slower in the others which will make the water much less laminar at the exit. The swirling tangential water input and the filter foam present in the bottom of most design is included for this purpose.
3) With that much flow you might want to try screens instead of straws. The other way to build a laminar fountain is to put a series of finer and finer mesh screens in place of the straws. The spaces holes formed by the mesh of the screen act like micro straws. Many commercial fountains use this. My experience has been that these are slightly less laminar but much easier to build. In your case it would still allow you to have very tiny openings/straws without to much build complication. You just need a good way to secure the series of meshes.

Those are my initial two sense. Let me know if I can clarify anything. I'm really curious to see what you come up with!

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