Partialy filled pipe

[colar]

I have a couple related questions regarding typical pipe flow in an open system.

1. In a pipe line, how can you predict if the pipe will be full or not? The flow calculations would seem to change radically based on the assumption that the pipe is filled vs. not filled.

2. Assume there is a long pipeline (6 miles or so), of constant diameter but with elevation changes. If there is a cross section of that pipe where the pipe is full, will it be full everywhere?

My original belief was that it should be, but then I realized that even though the volumetric flow is the same at any point, you could have a higher velocity coupled with a smaller area to produce the same flow.

The assumption is that as the pipe is rising in elevation, the pipe is fuller than it is on the downward side.

 

[sheiko]

I think this article may help you:

http://cat.inist.fr/?aModele=afficheN&cpsidt=2200737

"We don't believe things because they are true, things are true because we believe them."

 

[BigInch]

Calculate the hydraulic gradient at all points along the pipeline. Its the same as the fluid level, if the fluid was not contained in the pipe. If the pipe at some point is below the gradient, the pipe at that point is full. If the pipe is above the hydraulic gradient at any point, the pipe at that point is empty. If the hydraulic gradient falls inside the pipe at any point, the pipe is partially full.

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[katmar]

See thread469-257493 where there is a link to a good paper discussing exactly this problem.

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