exit flow under water/in open air

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marine_engineer
Posts: 1
Joined: Tue Feb 07, 2012 4:09 pm

exit flow under water/in open air

Post by marine_engineer »

Hi,
I'm investigating the difference between the outflow (of a drainage system) a meter under the waterline (in the sea) or just above the waterline in the open air. I'm having trouble to define the problems that will (not?) occur with the situation where the pipe (DN250) has an exit flow under water.
Which problems do I have to consider?
Some data of the system:
draining 27m^3 of water through DN250
1- either vertical pipe with an outflow perpendicular on the sea level, but 1m under water. This 1m is filled with sea water, so there will be an initial contact/clash and possible air inclusion here.
2- or a partly vertical pipe+long almost horizontal pipe (5x longer total pipe length than situation 1) and an horizontal exit into open air.

If I try to define it now and try to simulate it, I ignore any of the possible disadvantages of situation 1, and I take height from the piping till the sea level, and just take the meter under water into consideration by calculating with an extra meter total length of piping. Then the second situation will take longer to empty due to the longer total length of the piping, and an extra k-value for a 90degree bend in the system.
Is this correct, or will the under water exit flow show problems I didn't consider?

Thanks in advance
PipeFlowCalcs
Posts: 57
Joined: Sat Sep 17, 2011 8:50 am

Re: exit flow under water/in open air

Post by PipeFlowCalcs »

You will also have the pressure of 1m water on the pipe exit in vertical pipe. It is about 1/10 atm pressure or 10132.5 Pa, that the flow of water will have to over come and flow will because of that be lower.
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expressfire
Posts: 7
Joined: Wed Feb 08, 2012 3:13 am

Re: exit flow under water/in open air

Post by expressfire »

It is a great work that you investigate the difference between the outflow (of a drainage system).
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