#21
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Look at these two cases, the static head pressure at the valve (X) is identical for both cases. It's science don't argue with it cause you'll loose Shortening the pipe will do nothing for pressure and unless you're getting a vertex it will make no difference for adjustment and only result in issues relating to the entire overflow box draining during shut down. Last edited by sphelps; 12-13-2012 at 05:42 PM. |
#22
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Glad you got everything working. |
#23
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so what you're trying to say is that size doesn't matter??
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#24
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You assume that the volume of water coming over the weir is constant but it's not. Having a larger volume of water over the drain makes adjustment easier because it evens it out.
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#25
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First it is constant unless your pump is fluctuating which it shouldn't be and second volume has nothing to do with static head pressure.
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#26
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http://www.efunda.com/formulae/fluids/draining_tank.cfm It has been my experience that this increase in velocity makes adjusting a gate or ball valve on the drain MUCH easier. Determining the reason for this goes well beyond my math skills but it's very easy to demonstrate. I think it's because you end up with a full pipe before the drain valve which ends up giving you a more even flow rate. Regardless it translates into easy, repeatable and reliable adjustments. |
#27
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The issues you've experience are likely from the pipe being too close to the surface creating a partial or occasional vortex like I've mentioned a few times now. You need enough space from top of the pipe to the water surface to eliminate any vortex effects but you certainly don't need to remove it all together. I assure you the typical Herbie has an extended pipe to prevent the overflow from draining and it doesn't cause issues. This you should have noticed with the problem already being corrected with an extended pipe. If you wish to continue learning about fluid mechanics PM me, I'll happily discuss it with you but don't post incorrect information in this guys build thread. Last edited by sphelps; 12-13-2012 at 11:01 PM. |
#28
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.........
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#29
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I'll take some of the blame for this as I'm the one who first posted increased head on his main drain
When I lowered my main from 10" to 4" I thought I saw improved drainage, even though I had no vortex issues, hence my assumption Thanks for the great info Steve |
#30
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