Could anybody guide me how to go about stress analysis of a plug flow line. As far as I know, Plug flow is similar to slug flow, but the gas bubbles are normally smaller in size. Is it correct to treat plug flow lines similar to slug flow lines for stress analysis purpose?
Regards,

To describet this special phänomen (fluid and structure dynamic)is very complex and the results deviate in the most case to much from the realistic answer from the pipe.
My hint for you :
Look the answer at the pipe, if the phämonen is present.
-- Where are the displacement high (some bends)
-- Measure the Amplitude from the motion und the
frequency
-- Start a harmonic analysis with the measured
displacement and frequency
-- The stress result check with fatique Analysis
-- Normaly this kind stress amplitude must be
lower as the fatique strength

Dear Mr Ohliger,
Thanks for the reply. But, how to find the pipe phenomenon (frequency, amplitude, etc)? I think, you meant on-site data for an operating line. In my case, it is a new line to be designed for installation.
My doubt is whether plug flow lines can be treated as slug flow lines and carry out stress analysis accordingly.
Regards,

Ok i understand.
On principle you have 2 possibilitys :

First : Dyn.calculation in design status
The difficulty is to estimate the dyn load,their location and their frequency for this phenomenon.
I think you can only take inaccurate assumption and varyation them.
On principle estimate the eigen frequencys from your pipe system.
Is the lowest eigen frequency ca. >3 - 5 Hz , then i think do have not a big dyn. problem.
If yore have lower eigen frequencys, then ellimated them with more supports.
But calculated the thermal stress !

2. Me hint from my last contribution

Recards,
Ernst Ohliger