On the utilisation of vorticity and strain dynamics for improved analysis of stirred processes

The present work is aimed at the development of methodologies suitable for the characterisation and quantification of the strain dynamics occurring in vortical structures in stirred vessels. Due to the complexity of mixing reactor design, a fundamental flow, such as that associated with a vortex ring, has been selected to develop a procedure to gain improved understanding of mixing mechanisms by assessing the competitive actions of the strain rate tensor, S, and vorticity vector, omega. This flow exhibits similarities with the trailing vortex structure around impeller blades and is employed as a paradigm to develop analytical approaches, which are then applied to the vortex structure produced around a Rushton impeller. The identification of stretching and compression regions of strain and the quantification of the relevant terms is discussed in the context of drop dispersion and with reference to previously reported observations. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.