Dual modality tomography for the monitoring of constituent volumes in multi-component flows.

This thesis describes an investigation into the use of dual modality tomography to monitor multi-component flows. The concept of combining two modalities for this purpose evolved from a desire by the Water Research Council to determine volume flow rates of the major components of sewage. No single sensing method is capable of detecting all suspended solids in sewage flows therefore a decision was taken to combine the technologies of electrical resistance and optical tomography to produce a single measurement system. Sensors for both were positioned around the periphery of a static, circular phantom to allow comparisons between dual and single modalities. Modelling was carried out to determine the behaviour of the electrical impedance and optical tomography technologies in a three dimensional situation, where a variety of flow components exist. This provided a greater understanding of the problems involved in combining these technologies and an appreciation of the potential benefits. The remainder of the work can be divided into three areas. Firstly, hardware was constructed to make voltage measurements for both modalities. Secondly, software was written to perform data acquisition, data manipulation and image reconstruction using a simple back projection algorithm developed for this purpose. Finally, an integration of the individual hardware and software components was performed to produce a dual modality system on which tests were carried out to determine the resulting benefits over single modality alternatives.