Index of /skoge/publications/2000/havre_slugpaper

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K. Havre, K.O. Stornes and H. Stray. 
"Taming slug flow in pipelines".
Abb Review 4/2000. pp. 55-63.

Some "historical" comments written by S. Skogestad (June 2011).

This is to my best knowledge the first paper that describes use of feedback for stabilizing (severe) slugging, 
at least in a form where the authors actually understand that control is stabilizing a desired 
flow regime which is "naturally" unstable. Note also that the bottom pressure is used. 

The work was inspired by work Kjetil Havre had been involved with at ABB on stabilizing control for gas lift systems, 
and further based on simulations done by Kjetil Havre using Olga. 
Sigurd Skogestad contributed to understanding that control had the role of stabilizing a "naturally" unstable flow regime.
Kjetil and I discussed these issues for hours over the phone in the period 1999-2000 (while Kjetil was at ABB). 

I remember some of the early work Kjetil did in this area, which went back to his time at IFE, around 1997-98. 
He was also here working on the slug problem, and the idea made by IFE was to make a detailed model of the system and 
then use some kind of feedforward correction to avoid or at least reduce the slugging. I remember I was very sceptical
about this approach, because it is well known from control theory that feedforward control cannot change the dynamics
of a system; for this feedback is required. 

The work originally had limited support within ABB, so Kjetil had to most of the contacts with BP by himself for the actual implementation.
Also, the approach of using control to stabilize a flow regime was met by disbelief within the multuphase flow community, both in ABB and later in for example Statoil and at the universities.  

Original acknowledgement in paper (later deleted):
"The first author [Kjetil Havre] is grateful to Prof. Sigurd Skogestad at NTNU for his eagerness to 
understand stabilisation of unstable chemical and now fluid flow processes. 
Finally, I would like to thank him for his contributions in reviewing this paper."

Explanation:
Sigurd Skogestad was originally proposed by Kjetil Havre to be on the author list for this paper, 
but I (Sigurd) thought it was more proper to be in the Acknowledgement. 
However, in the final version also the acknowledgement was removed, probably because of ABB policy. 
The enclosed early version of the paper from March 2000 shows one iteration of the writing of the paper 
where I (Sigurd) faxed Kjetil my comments.

FURTHER COMMENT: By searching the literature I later found a paper by Pål Hedne and Harald Linga, who did experements on anti-slug control on the SINTEf rig at TIller in Trondheim back in the 1980's. This is probably the first anti-slug control experiment. (See separate folder which includes the paper and an email from pål from 2000). 
Fun fact: It happens that I was the neighbor with Pål Hedne in Balders vei in 1987-88, which was probably when he was making these experiments.