On the excess velocity of Taylor-droplets in square microchannels

Abstract

This thesis deals with the movement of Taylor-droplets in microscopic multiphase flows and reports a phenomenological model to improve the description of the instantaneous droplet velocity. The chosen approach can be seen as a holistic-hybrid between measurement methodology, high-speed image averaging and semi-analytic greybox modeling. For the first time, the influential parameters on the excess velocity are described for squared microchannels. Different valuable benefits arose on this journey beside the final model: A novel noninvasive and cost-efficient measurement device based on near-infrared photometry is developed and successfully tested, the flow-induced Taylor-droplet cap deformation is correlated to the Ca-number and genetic algorithms are successfully adapted for model adjustment. Model validation drives the development of a novel refractive index matching (RIM) approach. The phenomenology of the model is subsequently validated using carefully performed microPIV measurements.