Great points, I appreciate the input.
That's a fascinating design. I can see the appeal in some cases. I think for what we want to see in the tank, however, its not for us. But the points you mention are valid across both baffle types, and has gotten me thinking.
You are absolutely correct, that i was thinking about flow incorrectly. Or, more accurately, starting in the wrong place to emulate it. Volume will have to be considered for sizing pumps, but you are 100% correct in that I need to start with velocity, and then i will be able to figure volume based on the size. Good call.
So in this case...lets just say, for simplicity sake, that we are figuring moving the entire water column of the tank dimensions, ignoring the substrate, decorations, baffle area of the race track, etc. So a 1" water column, front to back, top to bottom is about 3 gallons. So if I wanted to move 1-2" per sec, then that would be 3-6 gal per sec, or 10,800 - 21,600 gph. That's a lot. lol. Thankfully the area won't actually be that big. Additionally, constricting the flow with larger rocks in certain parts will create a smaller area, so therefore a faster current, so I think that's the ticket. So with that in mind, i was thinking 2 pumps, with a max of 4000 gph each at max setting, but would use a lower setting 90% of the time. Does this math work out?
I really am leaning towards the racetrack type, after putting MS Paint to work again this afternoon. The plumbing and equipment to do an external recirc system have proven to be extensive. And a lot of drilling. below is what i mean.
Again in green is a double layer of egg crate on both sides to smooth the flow out. Then from both the top and side views you can see there would be 9 holes drilled, and 3 pumps in use. Knowing that there would be a differential in output of three vertically stacked openings, I already want to rethink that design so the output of one pump is split laterally rather than vertically, but you get the idea. Either way, I'm not sure I'm in favor of this approach. It would have the safety aspect, since its a closed system. But its a big gamble to drill all those holes, and then if it doesn't work how i hoped, I'm stuck with 18 holes.
Does anybody have any other design ideas to get a nice, linear flow going? This much volume is certainly a challenge.