RE: Part full line - water hammer estimation

From: <Al>
Date: Thu Jun 17 2004 - 11:59:00 EDT

JouKowsky's formula is very commonly used as a basis and is quite useful as a rough predictor. Ive found (as others ) reasonably reliable but it only tells you one thing which is banally obvious anyway.

There's no easy way to do this properly. I've been to a number of courses specifically covering this topic and not got a straight answer yet. The best and most straightforward is Surge by the Don Wood UNiv Kentucky and a good and useful book http://www.engineer.ca/ASMENorthern/surge.htm

As always it involves buying and using his software.

NExt best is PArmakian but involves a lot of math and work.

After that theres a lot of other books of limited usefulness

Al

-----Original Message-----
From: Steve McKenzie [mailto:mechproj@xtra.co.nz] Sent: Thursday, June 17, 2004 4:23 AM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Part full line - water hammer estimation

Gents + 1

I am looking at a water pipeline 2.8km long, flow rate 60l/s, ID 227mm.
The inlet is atmospheric from a tank. For the first 800m, the line drops 150m in elevation. For the remaining 2km, the line is near enough to horizontal, discharging into a pond. The friction loss under full pipe conditions will be about 30m (dirty). This means that the water will drop the first 120m (vertical) the line will run part full, with fairly high velocities. At the -120m point the line will become full with a fairly sharp head rise due to the sudden velocity rise forming a sort of hydraulic jump. I can take a rough stab at the part full velocity (using open channel flow theory) and I know the full pipe velocity. To get the surge rise, I thought I may be able to use Joukowsky's formula; delta H = a delta V /g; a is celerity. However, I think the result will be overly conservative,and would need to do a fair bit of work before being confident about the result. This is a fairly common operating condition, but I do not seem to have a clear estimation procedure for this.

Can anyone point me to a book or other reference?

Cheers

Steve

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