Guida, Antonio (2010)
Ph.D. thesis, University of Birmingham.
Mechanically agitated vessels are widely used for various mixing operations within a wide range of industries including the chemical, pharmaceutical, food and petroleum industries. They are used for liquid blending, solid-liquid mixing, gas dispersion in liquids, heat/mass transfer enhancement and chemical reaction. Mixing is intrinsically a Lagrangian process and, whilst Eulerian data are essential, Lagrangian information is necessary for its complete description. Possible approaches of generating Lagrangian data can, in principle, employ numerical simulations or experimental techniques based on Lagrangian tracking to provide the trajectories of fluid elements or solid particles. In this work a set of tools are developed for the analysis and theoretical validation of Lagrangian single and multi-phase flow data obtained from tracer trajectories in mechanically agitated vessels. Whilst theoretical procedures developed here exploit a large range of mathematical and statistical concepts with Shannon entropy being an example, the computational data analysis often involved handling and sequential processing of multidimensional matrices containing several millions of data points. Computational codes were developed for performing Lagrangian statistical data analysis, Lagrangian-Eulerian data conversion, Shannon entropy analysis, multi-phase mixing studies and detailed Eulerian multi-plane investigations. The implementation and power of these tools are demonstrated by analysing a wide range of measurements acquired using the technique of positron emission particle tracking (PEPT) during the mixing of Newtonian and non-Newtonian fluids, as well as the mixing of highly concentrated solid-liquid systems. These multi-phase suspensions included monodisperse, binary and polydisperse solid-liquid suspensions. Experimental measurements obtained in these systems are unique and valuable in their own right as, for the first time, it has been possible to determine the full 3D velocity and concentration fields of liquid and solid phases within opaque dense slurries of this type containing up to 40 wt% solids.
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