forces due due to pulsating flow in elbows or valves

[amadoc]

Hi
I'm looking for references or formulae to evaluate the forces on elbows, valves, etc, due to pulsating flow (i know the pressure pulsation)

thanks for your help

 

[jmw]

If you don't get any from a search here:

http://www.euronet.nl/users/e_wesker/et.html#1

or here:

http://www.xcalcs.com/

you might hope that a coriolis mass meter engineer will have some info to help.
Coriolis meters are mostly of thin wall bent tube construction. Under pressure, the tubes tend to want to straighten out and to stiffen. Pulsating pressure is a well known problem with such meters. I couldn't say if any data that might have would be relevant to what you are looking for though.

Just a suggestion. I am sure you will get better advise from some other members.

JMW

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[Cockroach]

This is an elementry computation, falling out directly from first law of thermodynamics, boundary control theory.

In particular, the force is F = m' (V2 - V1) for fluid mass flow m', outlet fluid velocity V2 and inlet fluid velocity V1. Since pressure is proportional to the square of velocity by the Bernoulli Equation, you can rearrange the equation in terms of pressure, the pulsating pressure proportional to P2 - P1, or dP. You will find the solution set to be nonlinear, try the iterative approach if velocities are poorly understood (i.e. implicit through pressure calculation). Of course you need to know fluid density to use Bernoulli, that's obvious.

...and now you know...

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[bvi]

well, if you know the pressure pulsation (e.g. +-100 psi), the calucaltion of the dynamic load on the changes in direction is straight forward. The pressure pulse times the inside area of the pipe gives you the dynamic load. The most conservative assumption for determining net load on any straight run of pipe would be to assume the maximum pressure pulse is on one end (e.g. +100 psi) and the minimum pulse is on the other (e.g. -100 psi). Note that this will be very conservative as it does not consider the dynamic effects (e.g. short duration of pulse and inertia of pipe) and the actual pressure differences on opposing ends of straight runs.

 

[amadoc]

thanks bvi