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#   Simplified models for slug flow in offshore processes   #
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All models are nonlinear state-space with ODE equations. Name of the folders represent the models.

1- Gas-Lift 3-state Model [3]
2- Pipeline-Riser 4-state Model [1]
3- Well-Pipeline-Riser 5-state Model
4- Well-Pipeline-Riser 6-state Model [2]

Files in different folders are similar. In every folder, you can find the following items.

**************** Files related to the models ********************

..._model0.m: Conaining equations of different models without time as input argument, this is for using in fsolve()

..._model.m: containing ..._model0.m, also time as a dummy input argument for using in ode15s()

..._parameters.m: Containing constant and parameters of models.

..._initialize.m: are used to find equilibrium states of the models to initialize the simulations from this point.

..._linmodl_num.m: are used to linearize the models and find linear state-space (A,B,C,D) using numerical differentiation.

..._linmod.m: are used to linearize the models and find linear state-space (A,B,C,D) using analytic differentiation.

.._sim.m: are used to simulate the models with your specified inputs and plot the simulation results.



*************** Files used for controllability Analysis ****************

controllability.m: Generates controllability data

gmsi.m: Generates stable part, minimum-phase part and minimum-phase-stable part of the 'G' transfer functions

gmsdij.m: Generates stable part, minimum-phase part and minimum-phase-stable part of the 'Gd' transfer the functions

gnsi.m: Generates stable part and anti-stable parts of transfer functions (similar to stabsep() function of Matlab)




************************** References ******************************
[1] Jahanshahi, E. and Skogestad, S. (2011). Simplified dynamical models for control of severe slugging in multiphase risers. In 18th IFAC World Congress, 1634–1639. Milan, Italy.

[2] Jahanshahi, E., Skogestad, S and Helgesen, A. H. (2012). Controllability analysis of severe slugging in well-pipeline-riser system, submitted to IFAC Workshop - Automatic Control in Offshore Oil and Gas Production, Trondheim

[3] Jahanshahi E., Skogestad S., Hansen H. (2012). Control structure design for stabilizing unstable gas-lift oil wells. IFAC International Symposium on Advanced Control of Chemical Processes, Singapore