X-ray based particle tracking velocimetry?a measurement technique for multi-phase flows and flows without optical access

Abstract

Information regarding the flow in multi-phase systems, such as bubble columns, is necessary for the design of improved devices, as well as for the validation of computer models. Common optical methods are limited in bubble columns with a large void fraction. The reason that this should be is the difference in the refraction indices of liquid and gaseous phases, which leads to reflection and refraction of light. In addition, in flows without optical access, optical methods cannot be used. The method proposed by these authors in their previous paper regarding X-ray based particle tracking velocimetry (PTV)–called XPTV–resolves these problems. It allows us to measure the velocity three-dimensionally, non-invasive, and in devices without optical access. In bubble columns, X-rays are neither reflected nor refracted at the phase boundaries and the flow is penetrated in straight lines. Therefore, it works independently from the void fraction. This has been proved to be a reliable and useful measurement technique, circumventing the limitations of optical methods. This paper reports the latest improvements in the algorithms designed to track and reconstruct particles, a feature which is explained here in detail. The improved algorithms are applied to measure the hydrodynamic parameters in a bubble column under two different flow conditions.