Anisotropic velocity distributions are normally experienced in unsteady multiphase flows, which are important for the analysis of the internal structure and dynamics of flows. The measurement and visualisation of velocity distribution from such multiphase flow systems is hardly achieved due to the opaque nature of the high concentration of solid or air in the flows. This paper describes a dual-plane Electrical Impedance Tomography (EIT) system for measuring the local air volume fraction and axial velocity distribution in both horizontal and vertical air-water flows. A 3-D velocity implementation was developed based on the ‘best-correlated pixels' method. Applying the 3-D velocity implementation to tomographic data sets obtained from an air-water swirling flow, axial, angular and radial velocity profiles were successfully extracted. The experimental results obtained from horizontal, vertical and swirling flows are reported.

Keywords: Opaque flows, velocity distribution, electrical impedance tomography.