Practical dispersion devices such as stirred vessels, packed columns and high shear mixers rely on energy supplied by a stirrer motor or pump to create the flow and deformation rates required for emulsification and solid-liquid dispersion processes. The deformation fields in these mixers exhibit large spatial and temporal variation so the dispersion capacity of the device depends on both its ability to focus energy and direct material through these high shear regions. Even in the absence of drops and particles, it is imperative to have a fundamental understanding of the velocity and deformation rate fields to aid in device selection and process design. These have been well studied both experimentally and numerically in stirred tank and static mixer geometries but less is known about high shear devices such as rotor-stator mixers and valve homogenizers. Rotor-stator devices present larger experimental and numerical challenges due to close tolerances and high rotor speeds. The highest deformation and energy dissipation rates occur in a narrow clearance region between the rotor and stator, exhibiting well-defined flow structures.
After an introduction referring to stirred vessels, the author will present several studies from his lab on rotor-stator geometries using both experimental (LDA, PIV) and simulation techniques (RANS, LES) to gain a better understanding of the velocity and deformation fields for turbulent water flow. When interpreting results, emphasis will be placed on how probing the underlying fluid dynamics informs analysis of dilute dispersion dynamics. Throughout the presentation, I will share memories from my friendship with Bob Brodkey and how he has influenced and supported my career and ability to reason physically as an educator, researcher and mentor. In addition to personal remembrances, Bob’s contributions to the North American Mixing Form (NAMF) will also be noted.
