Local Bubble Dynamics in Two-Phase Flows

For the development of environmentally sustainable processes e.g. in chemical engineering or biotechnology detailed knowledge of hydrodynamics and mass transfer is essential. A calculation of the exact design layout of reactors and processes required for multiphase flows has been impossible to achieve because of the complex transient coupling between the continuous and dispersed phases. Due to the lack of exact models to describe local and transient phenomena the calculation of hydrodynamics and mass transfer is over-simplified by using time- and space-averaged data, thus neglecting important facts. Recently developed measurement techniques allow the investigation of these local effects in multiphase flows and indicate that e.g. the behavior and slip velocity of fluid particles in a particle swarm differ from the behavior of single particles and depend on particle hold-up and flow conditions of the continuous phase. Measurements in two-phase flows in co-current and counter-current flow have shown that generally used models for homogeneous flow are dissatisfying.