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

气泡的动态相互作用和蜂群中的团簇形成对反应泡塔内的混合有重要影响。这是由于气泡尺寸局部尺度上的水动力不稳定性（尾迹不稳定性、气泡-气泡相互作用、形状变化和升力变化）。在气泡柱中，气泡引起的湍流占主导地位，这些过程是混合的驱动力。相关的传质影响的相应相关性尚不存在。为了研究这些过程，使用了一个大型旋转气泡柱（dn500，高度5m）和脉冲气体分离器，在羽流上升期间（n10 -50气泡簇），在这样一个簇的共同运动框架中观察到局部动力学。本研究的目的是通过3D-PIV/LIF联合测量技术同时检测同一子体积内的体积流量和浓度场，并对簇进行时间跟踪。该实验技术还适用于在所谓的周期盒中提供高分辨率DNS / LES模拟流泡簇（N < 50）的边界条件。因此，可以与SPP中的各个工作组进行直接的定量比较。根据结果，可以推导出考虑到局部集群动态的合适的运输模型。为了研究气泡群中螺旋不稳定性的影响，还在绕垂直轴旋转背景运动的影响下对气泡群进行了实验。

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.