Measurement of Velocity Profiles in Transient Single and Multiphase Flows Using Inductive Flow TomographyY
Michael O. Agolom 1*, Gary Lucas1 and Raymond O. Webilor1
1 School of Computing and Engineering, University of Huddersfield, Queensgate, HD1 3DH, United Kingdom
This paper studies the dynamic flow behaviour that occurs when a control valve on a pipeline is suddenly closed with the flow initially at steady state. Single phase (water) and two phase (oil-in-water) vertical flow conditions were investigated. An electromagnetic flow meter (EMFM) having a 16 electrode array was installed downstream of the control valve. The EMFM generated, sequentially, both a uniform and anti-Helmholtz magnetic fields and flow induced potentials proportional to the flow rates of water were measured at the electrode array. A novel image reconstruction algorithm was used to reconstruct the water velocity profile in the pipe cross-section at regular time intervals.
Velocity profile reconstructions from the EMFM device, both in single phase and multiphase flow, show that when the valve is suddenly closed the flow downstream of the valve oscillates - with the velocity profile successively changing between a very peaky profile with a much higher than expected velocity at the pipe centre to a velocity profile where the velocity at the pipe centre is much lower than expected. This oscillation occurs until steady state conditions are again reached. Similar behaviour is observed when the valve is suddenly opened. It is believed that these novel measurements of transient velocity profiles demonstrate hitherto unseen flow behaviour with implications for the safe design of equipment used in such transient flows.
Keywords: Transient flow, inductive flow tomography, image reconstruction, electromagnetic flow meter.
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