Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

In foam fractionation, to enhance the product yield, the seperation process can be intensified by the successive contraction and expansion of the aqeous foam. Performing optical bubble size measurements in combination with conductivity-based measurements of the surfactant concentration, Li et al. found that contracting the foam flow in a vertical column does neither affect the liquid flux nor the surfactant concentration, whereas a sudden expansion decreases the liquid flux. To gain comprehensive insights into the liquid fraction distribution and the velocity field of the foam while flowing through contracting or expanding geometries, we combined optical flow measurements, X-ray transmission imaging as well as X-ray particle tracking velocimetry (X-PTV) in a nozzle flow experiment as shown in Figure 1. This conference contribution presents the imaging techniques and reports experimental findings at different foam flow conditions. In the case of a diverging nozzle, we gradually increased the superficial gas velocity while keeping the bubble size constant, thus observing the transition from the expected plug flow to a detached flow including recirculation zones. In future experiments, the flow configuration investigated here will serve as a benchmark: performing parallel measurements with X-PTV, we aim to validate the approach of magnetic particle tracking (MPT) using planar Hall effect sensors.