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"From what I know abot the way ADA sets up their water flow they do try to avoid too much turbulence. I cannot say they are trying to achieve perfect laminar flow. But for sure the design of the Lily pipe now seems much more elaborate than I ever thought. I maybe way off in my thinking."

To my amateur points in my last post in the "other" thread.... Maybe what they know is that stable, laminar flow in an aquarium is impossible and therefore have designed an outlet that uses drag and vortex streets to its advantage, pushing them with acquired volume "down the street".

This seems like an optimal pattern.

How could it be made a little wider?
Keep all the vortices moving towards the intake and avoiding backflow?
What role does high-pressure at the outflow side and low-pressure at the intake side play in this movement? Assuming there is a pressure variance of course. Just assuming there is.

Love this topic, wish I know more.
 

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I haven't seen a lily pipe in action in person. I do recall discussion that one of the benefits of the whirlpool that a lily creates is an immediate downward flow and that the intake was higher than typical to encourage a u-shaped movement of water in the tank...down from lily, along bottom then up to intake.

I just gave NY 8-year old a tank of her own -new fluval Studio 600. It comes plumbed from the bottom of the tank, with both intake and outflow adjacent and rear/left of the tank. The inlet is approx 1/3 down from water kine. The outlet a little higher, is a pair of jets at 90 degree angles that I have aimed to the right. The flow in that tank is much like the gyre you have depicted above. You can see it...sinking pellets follow that path. Sophisticated test eh?

It's a 24 x 17 x 18 tank, so outflow hits walls quickly. Can't imagine that arrangement would perform the same way in a larger tank. Seems intake undercurrent would eventually overcome outflow momentum and create an area of stalled flow on the opposite side of the tank.

Given that our tanks have stuff in them I can't see how that on-it's-side U shape can be achieved in a large tank.

I tend to think of flow as a function of outflow force and shape. But I wonder what role pressure variance may play in the overall movement through a tank. Does the lily just establish a wide vortex street with a little downward force as fast as possible, depending on negative pressure to then pull through the tank?
 

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Here's a question that I've always wonders about. "how dead is a dead spot?"

Really, how dead IS a dead spot? O know, depends. I've always assumed that due to pressure variances in a tank water will circulate throughout. In "dead spots" that would mean slow movement, osmosis-like. But as long as there is good movement in the tank overall, isn't it likely that all plants get adequate exposure to co2 and ferz? They can only uptake so fast, so for plant health is a strong stream of flow in all nooks and crannies really necessary?

The benefit of deliberately eliminating dead spots then is just to keep detritus off the plants?

Just wondering. In my 84g i have had obvious areas of low flow, but the plants didn't seem to suffer.
 

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"First off, I'd like to say how cool it is to have someone who works in the fluid dynamics field in on this discussion! :whoo:"

Thanks Phil. I actually just work in sales for a major tech company. We have a division specialized in data center design and optimization. Fluid dynamics modeling is one component of what they do. I sell that service among everythin else, so I know a little about it, but I'm a real lightweight, not expert for sure.

Your comments make sense...the flowand pressures created by our equipment would make everything else irrelevant in scale.

Any thoughts on use of wave makers to create an occasional surge to and a wave of turbulence through a tank. I hate the look of waves lapping back and forth in a planted tank, but use of occasional pulses of a large volume of water as an alternative to elaborate outflows seems interesting.
 

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This isn't a perfect gyre, but moving the spray bar to the side accomplished a nice u-shaped flow in my tank. I made this change long ago after the discussion here.

In this video, I drop some small, sinking pellets into the tanks. You can see then move left->right, bounce off the right side and down and right->left.

It doesn't really show up well in this phone video, but I tried to follow some of the particles along the bottom of the tank back towards the intake side.

Not the double-U that a lily pipe can make, but better than a front-to-back arrangement.

 
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