Tank Flow and Physics argument

[demeyer2]

A friend and I have had an on-going argument over the last week about powerheads and flow in the tank and was hoping you could shed some light on the argument. He has a Seio 620 in his 10 gallon which he points down to the bottom pane of glass at about a 15 degree angle, virtually straight up and down. I say that this reduces the flow because the flow bounces back and cancels some of the flow from the Seio in the first place and also I say that whenever flow hit's a pane of glass or large obstruction it loses velocity/energy and the GPH throughout the tank is weakened. He says that when it hits something it disperses (which is obviously does) but the entire tank is still getting 620 gph even though a lot of the flow from the Seio bounces back at the powerhead. He also uses a HOB skimmer as evidence when he says if 300 gph (MJ1200) is going into the skimmer then 300 gph has to be coming out of the skimmer even though all the baffles (obstructions) should slow it down by my theory.
I look forward to your insights and thanks for reading,
Dan

 

[trippyl]

in a way you are both right. It WILL lose velocity when it hits any resistance (a sort of head pressure). At the same time, it's correct to say that he is still getting 620 GPH, because that is the speed when it leaves the PH.

The skimmer on the other hand is doing 300 GPH minus the head pressure of going through the baffles. But since this head pressure is inside the skimmer, it ISNT fair to say that the skimmer is getting 300GPH - it's 300GPH minus head pressure

In the first case, what it boils down to is how well you are using that 620GPH of flow - in this case, not very well.

 

[mr pink floyd]

my best guess from my 10th grade brain would be to say that the jet of water from the pump would hit the glass, and expell energy onto it, but not all of it, the energy that is left would go elsewhere in the tank, so like a bullet hitting a vest, all the energy from the bullet is released into the vest, but if the bullet hit a piece of steel and were to richochet(sp?) some energy would be lost into the steel, but not all of it, so the energy would bounce and go out

so i would say you are right, 620 GPH is going out, but is being reduced

just the friction of water will slow the 620 gph, so say an inch from the pump output the flow wont be 620, it will be some tiny decimal

that is my understanding of it, not sure if im correct though

hope this helped,

~Mike

 

[demeyer2]

Thanks for the inputs, very appreciated and I agree with both of you. Anyone else want to chime in?

 

[Amphiprionocellaris]

He is getting a 620 GPH, because that's only a turnover rate for the pump. Pushing the flow into the bottom of the tank lowers velocity (ft./s.), but that doesn't really affect the turnover. It's also probably better to have it flowing into the bottom, because it 1) creates random turbulent flow with the current interactions and 2) Seios put out lots of laminar water flow for a 10 gallon tank.