I needed to propose a mechanism to store water and keep water flow at the same level with 100% passive equipment.
Here's what I came up with. If you turn a water reservoir upside down and put in another one, with its end under water, the water doesn't run down, because air can't get inside, and water column is held by low air pressure.
Now, if I add a small hole in the bottom reservoir, h will be low, hence water velocity will be low too.
Flow rate will be the same until the upper reservoir empties, and water level starts decreasing.
Am I right? How is this mechanism called? It seems similar but different to medical drip chamber, but can't google out any confirmaiton, nobody discusses its physics.
ADDED Tested this in real life with plastic and washing liquid bottles. Indeed, the flow rate was gradually decreasing, but the device did keep water from bursting out. The upper bottle just gradually kept letting bubbles of air in.