Measurement of velocity profiles in transient single and multiphase flows using inductive flow tomography

Abstract This paper reports on the use of inductive flow tomography (IFT) to study the dynamic flow behaviour that occurs when a control valve on a pipeline is suddenly opened or 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 a control valve. The EMFM generated, sequentially, both 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 IFT image reconstruction algorithm was used to reconstruct the water velocity profile in the pipe cross-section at 2-second time intervals. Velocity profile reconstructions from the EMFM device, both in single phase and multiphase flow, show that when the valve is suddenly opened or 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. It is believed that these novel measurements of transient velocity profiles demonstrate hitherto unseen flow behaviour which may explain some of the damaging effects associated with the phenomenon of ‘water hammer’.