Experiment: Lateral lift force of single bubbles
The shear-induced lift force, which strongly influences the spatial bubble distribution, is one of the most important non-drag forces. However, measuring the lift force of ellipsoidal bubbles in a shear field is a very challenging task. Recently, our group developed a special experimental design that allows creating a stable linear shear field in air-water systems. Together with an averaging procedure suitable to address irregular movements of bubbles with high Reynolds number, we were able to experimentally determine the lift coefficient of ellipsoidal bubbles. Furthermore, we could reveal how surfactants and even tiny amounts of impurities in tap water can alter the strength of the lift force.
Ongoing work: Wall effects on the lift force
With regard to the hydrodynamic rising behavior of gas bubbles, it is known that additional acting forces or a modification of acting forces such as the drag force or the lift force can occur near the wall. Previous studies have focused on spherical bubbles or on highly viscous systems. In our current work, we want to investigate such phenomena for ellipsoidal/deformable bubbles in low-viscosity systems, as in the previous experiments on the lift force. In particular, modifications of the shear-induced lift force due to wall effects will be investigated.
Ongoing work: Swarm effects on the lift force
A particular focus of our work is the investigation of swarm effects, which are caused by the interaction of bubbles and their surrounding flow field with other bubbles in the vicinity. By implementing and applying AI-based evaluation methods, experimental images with an increased number of bubbles can be evaluated automatically. We will use these methods to investigate the aforementioned phenomena with bubble swarms, since bubble swarms, in contrast to single bubbles, can be found in most practical cases.
Publications
- T. Ziegenhein, a. Tomiyama, D. Lucas
A new measuring concept to determine the lift force for distorted bubbles in low Morton number system: Results for air/water. Int. J. Multiphase Flow 108 (2018) 11-24 - H. Hessenkemper, T. Ziegenhein, R. Rzehak, D. Lucas, A. Tomiyama
Lift force coefficient of ellipsoidal single bubbles in water. Int. J. Multiphase Flow 138 (2021) 103587 - H. Hessenkemper, T. Ziegenhein, D. Lucas
Contamination effects on the lift force of ellipsoidal air bubbles rising in saline water solutions. Chem. Eng. J. 386 (2020) 121589 - H. Hessenkemper, T. Ziegenhein, D. Lucas, A. Tomiyama
Influence of surfactant contaminations on the lift force of ellipsoidal bubbles in water. Int. J. Multiphase Flow 145 (2021) 103833 - P. Shi, R. Rzehak, D. Lucas, J. Magnaudet
Hydrodynamic forces on a clean spherical bubble translating in a wall-bounded linear shear flow. Phys. Rev. Fluids 5 (2020) 073601