Congratulations to Leon Knüpfer for his successful PhD defense

On 23 May 2025, Dipl.-Ing Leon Knüpfer successfully defended his dissertation entitled "Experimental Investigation of Bubble Sizes and Liquid Fraction in Rising Foam Columns".

Bubble size and liquid fraction significantly impact the performance of rising foam columns, commonly used in foam-based separation processes such as foam fractionation and flotation. Due to the opaque nature of foams, analyzing their internal structure remains challenging. This thesis presents improved experimental methods for characterizing bubble sizes and liquid fractions in model foam columns. Neutron radiography enables spatially resolved liquid fraction measurements, while invasive sampling and neural-network-based image segmentation are used to assess local bubble volume and facet size. Experiments are conducted in lab-scale columns with stable, non-coalescing foams. Liquid fraction profiles are measured in a 20 mm column and compared to theoretical models, accounting for structural ordering effects. Bubble size distributions across the column radius are investigated in a 53 mm setup, including studies with bidisperse foams. Finally, results from surface imaging and invasive sampling are compared in a 100 mm column, offering insights into the relationship between facet area and true bubble size.