Combined volumetric PIV-LIF measurements of the correlation between bubble cluster dyxnamics and mixing in a co-moving frame of a stable/unstable bubble plume
Dynamic interaction of bubbles and cluster formation in swarms have a significant influence on the mixing in reactive bubble columns. These are due to hydrodynamic instabilities on the local scale of the bubble size (wake instabilities , bubble-bubble interaction , change in shape and change of lift forces). In bubble columns where bubble- induced turbulence is dominant these processes are the driving force for mixing. Corresponding correlations of the associated impact on the mass transfer do not exist yet. To investigate these processes a large rotating bubble column (DN 500 , Height 5m) is used with a pulsed gas sparger, where the local dynamics in such a cluster are observed in the co-moving frame during the rise of the plume (cluster of N 10-50 bubbles). The aim of this study is to detect the volumetric flow and concentration field simultaneous within the same sub-volume with temporal tracking of the cluster via combined 3D-PIV/LIF measurement technique. The experimental technique is also adapted to provide boundary conditions as used in high-resolution DNS / LES simulations of flow bubble clusters ( N < 50 ) in a so-called periodic box. Thus a direct quantitative comparison is possible with various working groups in the SPP. Based on the results a suitable transport model is to be derived , which takes into account the local cluster dynamics. The experiments on the bubble swarms are carried out also under the influence of a rotating background motion around the vertical axis in order to investigate the effect of helical instabilities in the swarm.
TU Bergakademie Freiberg
Institute of Mechanics and Fluid Dynamics