Imaging Fluid Mixing

Reflecting on the history of Process Analytical Technology (PAT) development, the techniques of imaging and point measurement have always progressed in conjunction. Considering the important role of point measurement and visualization based on multiple points in the characterization of mixing processes, as well as in the evaluation of imaging results, a few conventional point measurement techniques are described briefly in this chapter, including the Pitot tube, conductivity cell, hot-wire anemometry and Laser Doppler anemometry. The chapter describes non-invasive imaging techniques, including photographic imaging, digital particle image velocimetry and process tomography. Applications of process tomography in mixing processes are outlined, including magnetic resonance imaging, positron emission particle tracking imaging and electrical process tomography, mainly in the guise of electrical impedance tomography. Point measurement techniques are still playing a significant role in the monitoring of fluid mixing processes, evaluation and calibration of computational fluid dynamic modelling (CFD) or imaging results.