Ian, you are right to question some of the science behind it.
That does not mean that it is not better for the tank. It very well may be just not for the reason listed.
kaptken is correct that the surface is easier (read uses less energy) to get spinning than the middle due to friction (air water boundry is considered frictionless).
Coriolis Effect (or coriolis force as the effect is just the preception of the force) does not effect the flushing of toilets, draining of sinks, etc. The force is so small that the geometery of the bowl overrides it.
http://en.wikipedia.org/wiki/Coriolis_effect scroll down to the “Corrections to common misconceptions about the Coriolis effect” part.
[glow=red,2,300]WARNING[/glow] from here on I am geeking out and most people’s eyes will glaze over. >LOCO< (We need some sort of geek smiley cause crazy is close but yet so far away)
You asked for it, you got it … :GEEK:
It also only applies to a rotating frame of reference (i.e. the earth, turntable spinning, merry-go-round). Lets assume none of us have spinning tanks. You could set your frame of reference so instead of say the back left corner of the tank as you would using rectanguler cooridinates (x,y,z) at the center of the rotation (somewhere is the middle of the tank) but this will make what happens at the tank walls really complicated.
There is some confusion between speed and velocity (velocity is a vector and speed is not).
The angular velocity is the same no matter how close you are to the center of rotation but the velocity (in x,y,z) is different. If someone really wants to know the differential equations to convert one to the other I am sure I can get them to you but if you actually care you probably have access to a physics book of some sort that has them.
I am looking for a cool picture there is one in my one book of what happens to the flow in a rectangular tank when the flow in the center is rotating.
Anyway, all of that aside it may be better for the corals. Crashing the output of the powerheads into each other is not an effient use of energy. Some compromise of the two probably is.
[quote=“IanH, post:24, topic:1072”]
Either way I think the dual vortex wave maker idea would rock! I’ll maybe give it a shot.[/quote]
That just sounds cool. If it is how I am thinking it would rock.