What are dynamics for sudden water flow stoppage?

[mrelet]

I test swimming pool drains-- sort of. I block the drain with a foam pad after establishing constant flow gpm. I take data and the pressure/time trace shows an initial sharp drop and then an oscillatory form on top of a decay back towards the pressure of the water head of the tank. Longer suction pipe lengths have longer periods.

Does anyone know if this can be modelled as a mass-spring damper system where the mass is the incompressible flow and the spring and damper properties are mainly in the foam?

 

[BigInch]

The only thing it has to do with the foam is how fast you can put it in front of the drain and block the flow.

If you do that very slowly, you will see that the initial pressure change will be much less than what you are observing now and there will be much less oscillation.

It can be modeled approximately considering the initial velocity of the water in the pipe and the time it takes to stop the flow.

If you are interested in modeling this more accurately, see my web page "blog" - subject Surge / Water hammer

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com