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[noodle0117]

So lets say I have a giant 3X3 tower that's completely hollow in the center and 50 z-levels high
XXX
XOX
XXX

Let's say that it's filled to the brim with water.
And lets assume that one of my dwarves was foolish enough to remove a wall section at the bottom of the tower.
So what happens?

1. does the water gush out at incredible speeds blasting the dwarf backwards with the same force as a hammer blow?
2. does the water flow quickly but not exactly at an explosive rate?
3. does the water flow slowly as if it were just a mass of jello(aka same way as magma)?

or how does it flow out?
does water flow speed depend on pressure?
if it does, then will it be possible to creat a giant water cannon that can be used to blast goblins against walls?

[Sphalerite]

Water will flow out with significant force, pushing creatures caught in it.  This will not damage the creatures, even if the flow forces them against a wall, but can be used to push them off a narrow ledge into a deep pit, or force them through fortifications into an inescapable trap.

It is also possible to do this with magma.  It's trickier since magma flow more slowly, but has the added bonus of setting the target on fire.  My current fortress's defense is based around a narrow steel bridge over a deep pit with a large magma reservoir which can be dumped to blast invaders into the pit.

[Grimlocke]

Removing a corner of the wall will only result in a very disappointing trickle due to the diagonal passage the water will make. Removing an orthogonal one should have the water flow out at a pretty fair speed though it would hardly qualify as explosive.

Though if the goal is just to make a watercannon you should probabaly use a reservoir with a line of pumps at the bottom. That should result in a pretty eplosive effect. Makes for some fun traps when combines with bridges spanning some form of grizzly demise, but beware of the reservoirs size as it can quickly fps-murder you once you pump its content out into open terain.

[godisdead132]

iv been thinking about this exactly for a while in 40d someone (cant recall who) built a 10x10 or so 40 z-level tower with a row of floodgates at the bottom all linked to a lever with a 1 z pit 3 squares away from the floodgates he stationed 5-6 dwarves there and opened it it threw some of them into the wall of the pit about 20 squares away hard enough to kill them so id say if its the same fluid physics as 40d still #1 is the most likely wont kill him/her though just throw them very fast but like they say falling never hurt anybody stopings the problem

[noodle0117]

So a room with 20 pumps all simultaneously trying to pump water through a small exit will work better?

[Terisuke]

So a room with 20 pumps all simultaneously trying to pump water through a small exit will work better?

What I'd do is have a situation like this:



XXXXXX~~~X
____%%~~~X
XXXXXX~~~X
XXXXXXXXXX


Side view, and assume the reservoir continues upwards for a long ways.

Make the exit narrow, and put about 5-6 pumps going out of the reservoir.

Your pressure should be astounding.

[leftycook]

Not sure how helpful this will be, but for science I dug into the bottom of a cavern lake to see how fast it would flood my mining shaft. The frame after i removed the wall section, my fifteen stories of roughly 3x3 rooms beneath the floor I connected to the lake were full of 7/7 water. I could be wrong though, I did it when  I was new to dwarf fortress, back at the start of 0.31

[Jordrake]

I don't really know much about Dwarven Physics, but this seems like it could be helpful for my idea to launch filled coffins at enemies.

[thijser]

pressure based movement and pump based movement don't move object/annimals.

[Man In Zero G]

pressure based movement and pump based movement don't move object/annimals.

That's not quite true. When irrigating the room that was soon to be farms with two pumps, all of the rough gems in the room were pushed up against the far wall. Some of the stones were pushed along too, but not as far. And this was just pumping enough to cover the floor with 1/1 water, mind you.
Very likely whether or not something is pushed by water is all due to object density.

[Grimlocke]

Creatures and objects move by flowing liquids, weight does factor into this. I recall making a bridge next to a canyon which had a mild trickle of water flowing over. It only pushed off cats in dogs, and the occasional unlucky child, so the actual flow rate is also a factor (stronger flows did push away dwarves).

What Thijser may have been confused with is the fact that 7/7 water never pushes anything, only changing heights of water do. Flooding a previously dry room with water does push the objects in it around, but dropping socks in a river just leaves the socks right there. Hence using liquids as a conveyor 'belt' could in theory work, but you would have to make some sort of wave-bath out of it. Not sure how one could go about doing that though.

[Niveras]

So a room with 20 pumps all simultaneously trying to pump water through a small exit will work better?

What I'd do is have a situation like this:



XXXXXX~~~X
____%%~~~X
XXXXXX~~~X
XXXXXXXXXX


Side view, and assume the reservoir continues upwards for a long ways.

Make the exit narrow, and put about 5-6 pumps going out of the reservoir.

Your pressure should be astounding.

I don't think that'll have the effect you intend. Pumps reset pressure to their level, so even though you had a row of 5 pumps pushing out water, it wouldn't have the "weight" of the entire tower behind the pressure - the tower would just as act as the reserve.

[Sensei]

I don't think it even works on that level. For example, pumps cannot push water up a chute, no matter how hard you try (at least in 40d).

[INSANEcyborg]

Check out this Hydrodynamics Education thread that explains about how water works.  Also, in the middle of that thread I posted some pictures of my own version. 

First, a tile of water on top of another tile of water will be pressurized, and when given the chance, will move like its been pushed though a pump.  So unless you have a pump for each tile of water, you'll have more pressure without them.   Magma on the other hand won't be pressurized, so you'll need a lot of pumps.

Second, water won't move in a stream or spray like in real life, It will just expand from the hole you made.  If there's enough water, it'll even loop around and get the backside of the tower.  Look at those pictures I posted in the Hydrodynamics Education thread to see what I mean.

[slink]

I don't really know much about Dwarven Physics, but this seems like it could be helpful for my idea to launch filled coffins at enemies.

I don't think you can launch filled coffins, the reason being that only built coffins get filled and when you unbuild them the contents fall out.  A built coffin won't move.