3-D Measurements of Optically Opaque Multiphase Flows Using Limited Angle X-ray Tomography*

Measurement of 3-D multiphase flow using optical methods poses a significant challenge due to their opacity. Application of radiation-based methods such as X-ray tomography is challenging, mainly for high-speed multiphase flows. In addition, geometrical constraints such as placement of the X-ray source and detectors to obtain a complete set of projections makes the application of the method hard. In this study, we present a limited angle X-ray tomography system that can measure optically opaque multiphase flows. The configuration consists of an almost semi-circular stationary high speed detector array located concentrically around a pipe. The X-ray source position is varied between 0-140 degrees, around the pipe, by deflecting an electron beam onto a tungsten target. A state-of-the-art statistical algorithm capable of reconstructing limited-angle projection data with reduced artifacts is used to produce cross-sectional images of flows. The system is validated using a static and moving phantom of known material distribution. Finally, measurements of instantaneous material fraction for a rising cap bubble in glycerin is presented.