Naomi said:But what I don't understand Mike is your suggestion that similar leakage
rates through the gates would result in a higher current flow due to
the lower gate.
In the normal course of events, a boatman leaving the lock will not
deliberately close the exit gate. He should lower all the paddles
(sluices) but leave the gate open.
So the starting points are either:
1) Top gate open, lock full, bottom gate closed, or
2) Bottom gate open, lock empty, top gate closed.
If the top gate is open, and the lock full, and the bottom gate is
closed, then water will leak through the bottom gate at various points
- but mainly near to the bottom of the gates, where the pressure is
greater. There will be no single point of leakage.
The leaks will be about 70-75 feet downstream of the top gates. The
rate of leakage will be fairly slight. This will not be enough to
cause a significant current at the top of the lock. Although it is not
quite accurate, imagine the bottom gates attempting to "suck" the top
gate closed. Not likely.
The water is leaving the lock chamber from some distance below the
surface. There is a similarity here to what happens at the shallow end
of your bath when the plug is not quite in place. The water level goes
down without any significant lateral movement.
(Can I just clarify for the other readers that I have not studied Naomi
in the bath, and this is a purely hypothetical example.)
However, if the top gate is closed, lock empty, bottom gate open, then
all the leakage through the top gate is focussed into the lock chamber.
The water tends to cascade down into the chamber because although the
leaks are some way down the body of the top gate, they are typically
above the level of the water in the lock chamber.
The flow is directed along the lock chamber which is a constant width
and depth, then over a small sill (at the foot of the bottom gates).
This flow of water is in a consistent direction, and there is a slight
Venturi effect which tends to draw the bottom gate out of its resting
place. Once the bottom gate is slightly into the current, the current
then "blows" the gate shut.
--
Mikefule
"The world is Hell, and men are on the one hand the tormented souls, and
on the other the devils in it."
Arthur "Cheery" Schopenhauer
------------------------------------------------------------------------
Mikefule's Profile: http://www.unicyclist.com/profile/879
View this thread: http://www.unicyclist.com/thread/51977
