Effect of noise level and prior parameters on the velocity field reconstructions in electromagnetic flow tomography
Ossi Lehtikangas and Marko Vauhkonen
Department of Applied Physics, University of Eastern Finland, P.O.Box 1627, FI-70211, Kuopio, Finland
Electromagnetic flow meters can be used for measuring flow velocity in the process industry. The flow meters can measure the mean flow velocity of conductive liquids and slurries. A drawback of this approach is that the velocity field cannot be determined. Information about velocity fields is important for characterizing multiphase flows such as oil-in-water flows in the oil industry. Moreover, asymmetric flows are also encountered near valves, in pipe elbows and T-junctions. Recently, electromagnetic flow tomography (EMFT) has been proposed for measuring velocity fields using several coils and a set of electrodes attached to the surface of the pipe. The velocity field reconstruction method utilizes a finite element based computational forward model and a Bayesian framework for inverse problems. In the approach, a prior probability model for the velocity field is written describing flow. In this work, the effect of noise level and parameters of the prior model on the velocity field reconstructions in EMFT are tested using numerical simulations. The results show that the velocity field reconstruction method produces feasible estimates even with high level of measurement noise. In addition, it is shown that the parameters of the prior model can be chosen based on the flow pipe diameter, and expected minimum and maximum velocity values around the mean flow.
Keywords Electromagnetic flow tomography, Velocity field reconstruction, Inverse problems, Finite element method
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