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Shahzad Munir,Muhammad Israr Siddiqui,Morgan Heikal,Abdul Rashid Abdul Aziz,Guillaume de Sercey 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.11
The Proper orthogonal decomposition (POD) method has seen increasingly used in the last two decades and has a lot of applicationsfor the comparison of experimental and numerically simulated data. The POD technique is often used to extract information about coherentstructures dominating the flow. The two-dimensional and two-component instantaneous velocity fields of both liquid and gas phasesof a slug flow were obtained by Particle image velocimetry (PIV) combined with Laser induced fluorescence (LIF). POD was applied tothe velocity fields of both phases separately to identify the coherent flow structures. We focused on POD eigenmodes and their correspondingenergy contents of both liquid and gas phases. The sum of first few eigenmodes that contain maximum turbulent kinetic energyof the flow represents the coherent structures. In the case of liquid phase the first eigenmode contained 42% of the total energy, while inthe gas phase the decaying energy distribution was flat. The POD results showed that the coefficient of mode 1 for the liquid phase oscillatedbetween positive and negative values and had the highest amplitude. For the visualization of coherent motion different linear combinationsof eigenmodes for liquid and gas phases were used. The phenomena of turbulent bursting events associated with Q2 events(low momentum fluid moving away from the wall) and Q4 events (high momentum flow moving towards the wall) were also discussedto assess its contribution in turbulence production.