B Water surface behavior under pressure change

[Bjott]

Hi togehter,

this may be an easy one for most, but I'm really struggling with imagining the process.
Suppose we have a compressed air vessel that is half filled with water. The pressure in the vessel drops from 10 bar to atmospheric pressure within a few seconds. How does the water surface behave? Is there any movement due to the pressure difference? Or does the water only move due to the flow of the escaping air. Or is there no movement at all?

Thank you very much!

 

[Baluncore]

Welcome to PF.

I assume the reduction in pressure is due to loss of air only, not water.
Water is not really compressible, so the water volume will not change due to the change in pressure. The position of the surface should not change. The surface may be disturbed with ripples temporarily, caused by the dynamic escape of the air from an asymmetric orifice.

 

[Dale]

It also may change due to changing strain in the pressure vessel itself. The pressure vessel will get smaller so the water will rise.

(Note, at this level you probably cannot consider the water to be completely incompressible either)

 

[Dullard]

If the temperature happens to be above 100C (and below 160C), the water will start to boil.

 

[Arjan82]

If the water has stayed in this vessel with the high pressure air for a long period of time, then gas will dissolve in the water (at least, more than in atmospheric conditions). When the pressure is released the gas will escape again leading to small bubbles (also, already existing bubbles underwater will grow). Otherwise, not much movement as already pointed out.