#LIQUID MEASUREMENTS FULL#

For example, air is entrained into the water body of an open channel flow if turbulent motion significantly distorts the free-surface 6, 7, 8, leading to entrainment of large air pockets that subsequently break up into bubbles of smaller diameters 1 (0.1 ≲ d ≲ 100 mm). Accurate velocity measurements in gas–liquid flows are essential to properly evaluate gas–liquid interaction 6 and therefore lay the foundation for an improved modeling of gas–liquid flows. Mass and energy transport processes across a gas–liquid interface are dominated by shear and turbulence 5. Some examples include rapids in mountain streams, breaking waves 1, nuclear reactors 2, process engineering plants 3 and violent flows in water conveyance infrastructures 4. Gas–liquid flows play an important role in mass, momentum and energy transfer. The correction method increases the accuracy of bubble velocity estimations, thereby enabling a deeper understanding of fundamental gas-liquid flow processes.

#LIQUID MEASUREMENTS FULL#

We show that the velocity bias is strong in laboratory scale investigations and therefore may affect the extrapolation of results to full scale. The proposed methodology allows to assess the bubble–probe interaction bias for various types of gas-liquid flows and to recover the undisturbed real bubble velocity. To overcome this velocity bias, a correction method is formulated based on a force balance on the bubble. Using different state-of-the-art instruments and analysis algorithms, we show that bubble–probe interactions lead to an underestimation of the real bubble velocity due to surface tension. Such two-phase flows are commonly investigated using phase-detection intrusive probes, yielding velocities that are considered to be directly representative of bubble velocities. Gas–liquid flows occur in many natural environments such as breaking waves, river rapids and human-made systems, including nuclear reactors and water treatment or conveyance infrastructure.

Liquid measurements