The two-phase flow of air/water has been investigated in two ‘complex’ geometries: a vertical pipe with contraction and a line/riser system with a bend. Pressure recordings and optical fiber measurements have been analysed using Auto-Regressive modeling. This type of modeling describes the data as a linear combination of previous data. It is discussed how the transition from one flow regime to an other is influenced by the flow obstructions. The Auto-Regressive modeling provides a quantitative measure of the similarity between two flow realisations. It is found that identification of flow regimes based on this measure coincides with visual observation. With the Auto-Regressive technique the width of the transition could also be quantified. Furthermore it is shown, that the upward bend stabilises the slug flow in the vertical part downstream of the bend: the transition towards churn flow is postponed.