Vibration in pipelines

This is a complex issue, I've recently been involoved with this problem with a flexible pipe, which has a corrugated steel lining, that was conveying gas. After a certain velocity the pipe begins to hum, as the gas flow boundary layer become unstable.

This is not a problem for the flexible pipe but can cause the rigid pipe work, to which it is connected, to fatigue and crack.

Several attempts have been made to model this effect numerically, using CFD packages, but however these were not able to recreate the magnitude of the pressure wave that has been seen in real life.

An emperical approach, based on a number of observations has shown that pipe vibration may depend on the relationship between the Strouhal number, based on the distance between pipe corrugations, and the pipes first radial eigenmode as expressed by Blevins.

No firm answer as yet, but this is what we are looking at in the case of our flexible pipe structures

Thanks for that, I have, however, seen rules where for a given density x velocity squared value a maxium flow rate is given. Is this an in house rule of thumb or a more established corelation?

Daniel

I'm sorry that is not one I've come accross before. The one that I have seen simplifies down to being a relationship between the geometry of the pipe (height of undulations, pitch length of undulations and bore) and the velocity. As I said this is particularly for corugated pipe, which I do not know how relevant this is to you design case.

No worries, I am simulating a pipeline and just wanted to add feature that allowed the user to set the maximum flow of the pipeline before vibration begins. Apparently it is a problem for them. They just gave me a graph with a pv2 curve for P vs flow rate. I thought it looked to simplistic. I supposed it is something they developed themselves. Many Thanks Mark

Daniel