Numerical simulation of single rising bubbles influenced by soluble surfactant in the spherical and ellipsoidal regime
In a recently published work the institute for Mathematical Modeling and Analysis successfully introduced a new numerical model to approximate very thin boundary layers at fluid interfaces. This allowed us to investigate physical phenomena on realistic time and length scales. In another recent work the model was applied to investigate the influence of surface active agents (so-called surfactants) on the hydrodynamics of rising bubbles. For the first time a quantitative comparison with experimental data could be achieved.
Now we would like to extend the studies of  to a wider range of bubble sizes. One important effect of surfactants is that they introduce or change path instability (how the bubble rises). Such behavior is important for applications like froth flotation or bubble column reactors. This investigation will help to get a more complete overview of possible changes in the bubble motion. In general bubbles in the spherical and ellipsoidal regime may rise on a rectilinear, helical, or zig-zag path. The following scenarios will be investigated:
- rectilinear (clean) → rectilinear (contaminated)
- rectilinear (clean) → helical / zig-zag (contaminated)
- helical / zig-zag (clean) → helical / zig-zag (contaminated)
The obtained results are of general interest, so that they are likely to lead to a publication in an international scientific journal.
- The first step will be to obtain a basic overview of the physical phenomena based on selected literature (mainly [1,2]).
- The second step will be to create case set-ups using an enhanced version of the bubbleInterTrackfoam solver contained in the OpenFOAM library.
- Evaluation and visualization of the simulation results as done in  is a major step to understand the observed phenomena and to build simplified models. In particular the lift and drag forces acting on the interface are of interest.
The topic is suitable for students of mechanical engineering, physics, mathematics, computational engineering or any related course. The thesis work can be started as of now (23.02.2018). A period of 4-6 month should be available to successfully complete the project.
The student will learn about: Computational fluid dynamics, bubble physics, OpenFOAM, ParaView, Linux, high performance clusters
 A. Weiner, D. Bothe: Advanced subgrid-scale modeling for convection dominated species transport at fluid interfaces with application to mass transfer from rising bubbles. Journal of Computational Physics 347, 261-289 (2017)
 C. Pesci, A. Weiner, H. Marschall, D. Bothe: Computational analysis of single rising bubbles influenced by soluble surfactant. https://arxiv.org/abs/1712.05224