Deep flow vs. shallow flow

[waldomas]

I have recently redirected the flow from my "eyeball" returns in my pool so they are aimed lower and deeper towards the bottom.
At first they appeared to be moving less water and I thought, perhaps because of added pressure from above slowing the flow?... But upon closer examination, ther were alot of "boiling areas" on the surface that were quite far from the return! I had similar fx with the previous positions, but not that far away.

Is it possible that surface tension, or even air can reduce flow rates thru water? If all other things are equal (no wind, same pumps performing equally, area, obstructions, positions, etc.), would deeper flow patterns produce stronger flow? Is the surface inhibiting flow or is deeper flow just self perpetuating? Did I say that correctly?

Someone just tell me to go to bed.:spin2:

 

[*reefermadness*]

I would think that the deep flow allows a larger portion of the total body of water to get moving. Like you said, self perpetuating.

 

[waldomas]

Would that mean that flow eminating from the center (from top to bottom) produces more total flow than from lower or higher? That makes it seam like center would be ideal, having upper and lower limits that are farther away.

 

[palmer373]

hmm then in a 55 would it be better to have my powerheads towards the bottom or up top? sorry to go a lil OT i was just curious about the same thing.

 

[waldomas]

Without upper and lower limits, the flow would create more of an eductor or penductor type of flow, or a chain type reaction so to speak?

Or is it more similar to a gyre type flow, more momentum?
Or is that the same thing?

 

[*reefermadness*]

That is what I was thinking, the gyre type. Moving the entire water column to optimize performance out of the system.

 

[waldomas]

Gyres can flow in multiple directions. Left - right, top - bottom, and their opposites.
If we assume the surface were to hold back the flow, than horizontal flow patterns should be more efficient.

I guess a penductor, like a gyre, would require less work to reach an equal or greater level of flow, once it got going. I guess its the same principal?
Or result anyway.

 

[seafd]

the flow through an outlet will be pretty much the same no matter where it is. Unless the length of the tubing changes significantly or the size of the outlet changes. What the flow does once it exits the outlet is changing at different points in the tank. If you aim an outlet at the surface then you are basically shooting a jet at a wall so you may see a lot of movement along the wall but not so much throughout the tank. If you point the flow into the center of the tank then a typical jet can form and will move a broader portion of the water.

 

[bronkanus]

Ive always kept my powerheads and returns about midway in the tank with a slight upward tilt and had really good flow throughout unlike when I started I would point them at the top figuring that surface flow equaled whole tank flow

 

[Thales]

I have recently redirected the flow from my "eyeball" returns in my pool so they are aimed lower and deeper towards the bottom.
At first they appeared to be moving less water and I thought, perhaps because of added pressure from above slowing the flow?... But upon closer examination, ther were alot of "boiling areas" on the surface that were quite far from the return! I had similar fx with the previous positions, but not that far away.

Is it possible that surface tension, or even air can reduce flow rates thru water? If all other things are equal (no wind, same pumps performing equally, area, obstructions, positions, etc.), would deeper flow patterns produce stronger flow? Is the surface inhibiting flow or is deeper flow just self perpetuating? Did I say that correctly?

Someone just tell me to go to bed.:spin2:

How do you know how much water was being moved before? The 'boiling' spots would be at the bottom when the jets were pointe up wouldn't they?

Generally there is less drag at the surface of the water because air is less dense than water, so you get more momentum if the water is returning at the surface.

 

[waldomas]

When I aimed my returns downward, the boiling areas were a greater distance from the return than any noticable moving water at the surface when the returns pointed upward.
It seems to me that a penductor type of effect was occurring which caused the disturbance to be farther reaching or greater.
If not because of the penductor effect (or chain reaction so to speak) amplifying the amt. of water moved, perhaps its just a lack of influence deminishing any self perpetuation.

I think thats what I'm trying to say.