Student practical training / Bachelor theses / Master theses

For the CFD modelling of bubbly flows at the component-scale the two-fluid methodology has proven to be the most effective approach. For the various interfacial forces, turbulence sources and bubble-bubble interactions a multitude of partly empirical closure models exist in the literature, each validated with the data from a particular experiment conducted for a specific flow configuration. For many years the HZDR strategy is to establish a fixed set of closure models that reflects local flow phenomena and offers generality and predictability [1]. The current set of baseline models was established via the CFD analysis of numerous validation cases.
The set of baseline models should now be applied to new TOPFLOW data for bubbly flows, which were recently generated at the HZDR [2]. For the polydisperse flow in a constricted vertical pipe quantities such as gas holdup distributions, liquid velocities and bubble sizes were measured. The goal of the project is to reproduce these new cases with the CFD-software OpenFOAM. A main challenge will be the generation of a suitable computational mesh for the pipe geometry with a ring-shaped and a baffle-shaped obstacle. The obstacles constrict the flow locally creating turbulent wake regions that cause interesting bubble-bubble interactions. The polydisperse CFD analysis of the case will allow the detailed analysis of the bubble coalescence and breakup processes and the evaluation of the models that aim to describe them.

References:

[1] R. Rzehak et al., "Unified modeling of bubbly flows in pipes, bubble columns, and airlift columns," Chem. Eng. Sci. 157, pp. 147-158, 2017.
[2] M. Neumann-Kipping et al., "Investigations on bubbly two-phase flow in a constricted vertical pipe," Int. J. Multiph. Flow 130, 2020.

Main tasks:

• Creating a suitable geometry and mesh of the constricted pipe
• Establishing a corresponding polydisperse case setup in OpenFOAM
• Comparison of computed results with measured TOPFLOW data
• Parameter variation of the established setup (via various liquid and gas superficial velocities, different obstacle shapes)
• Report and presentation of results

• Experience using CFD software, preferably OpenFOAM
• Excellent written and verbal communication skills in English
• Team player with a strong interest in multiphase flows

Duration: 6 months