Scales and structures in bubbly flows. Experimental analysis of the flow in bubble columns and in bubbling fluidized beds

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Abstract

In this project a detailed experimental analysis was performed of the dynamic flow field in bubbly flows, with the purpose of determining local hydrodynamics and scale effects. Measurements were done in gas-liquid systems (air-water bubble columns) and in gas-solid systems (air-sand bubbing fluidized beds) of different size. Amongst others with the help of lasers and glass fibres the behaviour was studied of single bubbles, bubble swarms and the continuous phase. These techniques were combined with advanced signal processing such as correlation analysis. A striking new phenomenon was the anisotropy or orientation dependence of experimental results. A detailed experimental study into the applicability of laser Doppler anemometry (LDA) in bubble columns showed that virtually only the liquid phase is recorded with LDA. The measurements show a pronouncedly turbulent flow field, but it is striking that this complex view can be characterized by a small number of fixed parameters. These parameters can also be used quite well for describing several physical phenomena and for scaling up these reactors.