Proper Orthogonal Decomposition as a technique for identifying two-phase flow pattern based on electrical impedance tomography

Collecting of very large amount of data from experimental measurement is a common practice in almost every scientific domains. There is a great need to have specific techniques capable of extracting synthetic information, which is essential for understanding and modelling the specific phenomena. The Proper Orthogonal Decomposition (POD) is one of the most powerful data analysis methods for multivariate and nonlinear phenomena. Generally, POD is a procedure that takes a given collection of input experimental or numerical data and creates an orthogonal basis constituted by functions estimated as the solutions of an integral eigenvalue problem known as a Fredholm equation. This paper proposes a novel approach by utilising POD to identify flow structure in horizontal pipeline, specially, for slag, plug and wavy stratified air-water flow regimes, , in which POD technique extends the current evaluation procedure of electrical impedance tomography [31]. This capability is extended by the implementation of POD as an identifier for typical horizontal two phase flow regimes. Direct POD method introduced by Lumley and Snapshot POD method introduced by Sirovich are applied The POD snapshot matrices are reconstructed from electrical tomography measurement under specific flow conditions. It is expected that this study may provide new knowledge on two phase flow dynamics in a horizontal pipeline and useful information for further prediction of multiphase flow regime

Vertical annular flow pattern characterisation using proper orthogonal decomposition of Electrical Impedance Tomography

Annular flow is one of the most important multiphase flow regimes primarily because of its presence in extensive industrial applications,such as steam generators, evaporators, condensers and boiling water reactors. There is a great need to have specific techniques capable of extracting characteristics of annular flow pattern via experiment and/or modelling, which is essential to understand specific annular flow phenomena. The intention of developing a mathematical decomposition method for flow regime recognition comes from the fact that each regime is characterised by unique dynamic behaviour. The direct approach with Proper Orthogonal Decomposition (POD) was previously introduced by Lumley, which required a very large amount of relevant data from experimental multiphase and process conditions is necessary. The presented approach is to apply POD on a large amount of tomograms for identification of annular flow pattern in a gas-liquid two phase flow, which also provides a new method to extend the current evaluation procedure of Electrical Impedance Tomography (EIT) for imaging of air-water pipeline flows.The paper demonstrates the capability of the proposed method with a study on annular flow patterns in vertical pipeline