fppf said:
Well, I read most of this thread (8 long pages, cut the chat geezs).
I have a lot of hydraulics and pneumatics background and some thoughts.
> My hydraulics and pneumatics background is only experience, and plenty of it, but no formal training. Some of the statements that I have made are "seat of the pants" so to speak, but, I am ready to defend them right up to the "understanding"!
fppf said:
Have you tried doing a test draw in a tub with some food coloring streamers? I don't think your going to get the even flow your wanting..
> No, not with food coloring, but I did do a flow test for even flow at the "plenum" ( meaning through the feeder holes ), and it was consistent to within 10%. In other words, the plenum plumbing itself, flows consistently, pressure, or, "vacuum wise" to within 10%, using the "total feeder hole area" to "draw tube area" restriction ratio "method" for accomplishing "balanced flow", and that is again, 33-50% restriction, by way of total feeder hole volume, to "draw tube area". This will "fall-off" if "low flow rates" are used, which I insist on avoiding. "High Flow" only.
fppf said:
I would strongly suggest you setup this in a tub, then drop some food coloring in there but don't mix it. Then do a test draw and see if the coloring at the ends moves the same as near the draw pipe. I don't think it will given the fluid dynamics.
>If that test is conducted by anyone on my design, they will observe even flow balancing within 10%. I cannot conduct such a test now, because the plenum that I built is under 6" of substrate, and 35 #'s of live rock.
fppf said:
Basiclly to have flow you need a delta pressure, each hole in the pipe will provide a way to decrease that delta pressure so by time you get to the end there wont be as much so then you get less flow through that hole.
> And that is the reason for "CaptiveReef's" suggestion for "more holes near the extremities", and that is one of several remedies, available to counteract "delta loss" near the "extremities".
fppf said:
As for the amount of water you want to pull its not going to be the volume of the area of the tank times you wanted depth. It will be that volume minus the volume the sand takes up. Depending on the size of grain used it will vary the amount of water actually held in the sand and then the limit of the draw to protect the teria.
>You are quite right here, and thank you very much! One pint of flow, on my system, might now be 1", if we find that "substrate typicaly uses up 87.5% of the "available volume". Thanks for the contribution, "we" all needed that. ( very important seriously! )
fppf said:
As for a system to get the wanted flow pattern thats a little harder (IF the system now has flaws, testing needed).
>All systems will have flaws, we must overcome this with better information. Until we know more about the depths of these bacterial processes, we cannot accurately estimate the appropriate depths of the "substrate", relative to the "Bacterial recovery time", relative to downward "flowrate", "relative" to E=MC squared. ( and Particle Size, of course )
I could easily bombard this thread with mathematical formulas, that I can take right out of my head ( and further with real fancy ones that I will research, just as soon as anyone gets past the "former" ) until it only took a "Nano-Second" for everyone to "head for the hills" ( or down one of Bombers'
"worm holes" ) on this idea. I have been very careful not to do so.
If this project is going to be successful for the "Typical aquarist", it must be understandable in reasonable "laymans terms".
Typical Aquarists are rather intelligent people, so far as I have noticed anyway.
fppf said:
Think about this one. For a given area of sand you will have a maxium flow value based on the porosity of the sand and water colume above it. I would suggest to use a matterial that has the same porosity or a little less than the TOTAL sand bed.
> Huh? Is this "relative" to "Particle Migration", or something else? Material for what? ( TOTAL what? )
Could you "expound" on this? ( "I don't get it" )
fppf said:
Then make the "plenum" or draw space the size of the wanted water draw. Then provide away to rapidly drain this area and replace it with a nitrogen purge. This would then allow for the fastest most even flow the bed could take.
Look, I'm listening here, but you're "gonna hafta" run "thatun" by me "agin there pardner".
fppf said:
The amount of water moved would be limited when the space is filled backup with water again. The nitrogen would be pushed out through a vent as the water flows down.
]
And the "function" here is?
fppf said:
I totally understand what your end need is and why you want to do it. But like what has been said, its going to take a lot of good testing and TIME to prove out a system. I don't even feel the true book writting "experts" have spent the time to prove out there ideas 100% yet.
Or 20% for that matter, in this case, but you are quite right.
Look, this may have seemed a bit "reactionary", if you like, but, I've left you with some questions, and if there is something else that you think that I am not understanding properly, by all means, "lay it out here".
And thank you very much for becoming involved, "we" need all the help we can get!]
> barryhc
:thumbsup:
