X-ray tomographic analysis of Taylor bubble shape in small channels (Taylor bubble benchmark)
The Taylor bubble flow is characterized by an intensified gas-liquid contact in the liquid film surrounding the Taylor bubbles and by an enhanced mixing in the liquid slugs downstream the Taylor bubbles.
In the framework of the German Research Foundation (DFG) funded Priority Programme DFG-SPP 1506 “Transport processes at Fluidic Interfaces” the “Taylor Flow” was defined as a benchmark for the validation of mathematical models and numerical methods.
At HZDR enhanced X-ray radioscopic and X-ray tomographic measurement techniques were further developed and qualified to disclose the three-dimensional shape of Taylor bubbles in small channels. Experiments at the synchrotron radiation source ANKA (KIT Karlsruhe) enabled exact measurements of the Taylor bubble shape in channels with different cross-sections. At an effective spatial resolution of 5.6 µm and at an exposure times of only 1/36,000 seconds with corresponding high frame rates, even smallest morphological details such as the interface curvature at bubble front and rear were resolved. Parametric experimental studies were conducted for different channel cross-sections (circular, square) and superficial velocities (Ub = 20-320 mm/s) in aqueous glycerol solutions (Ca = 0.01-0.16). The resulting data are provided for the validation of numerical flow simulation tools (“Interface Capturing and Tracking”-methods, “Sharp Interface and Diffuse Interface”-methods).
Further experimental studies were conducted utilizing an X-ray microfocus imaging device. Three-dimensional tomographic images of single Taylor bubbles immobilized at a fixed vertical position via countercurrent liquid flow in channels with hydraulic diameters of 6 mm were captured at an effective spatial resolution of 27 µm. Thereby, the characteristic Taylor bubble shape in square channels was disclosed for the first time, which was not accessible before using optical methods. Utilizing these results, an X-ray radioscopic measurement technique was qualified for the measurement and evaluation of the dynamic mass transfer of Taylor bubbles considering also the effect of surfactants.
- TU Darmstadt,
- RWTH Aachen,
- KIT Karlsruhe,
- TU Hamburg-Harburg,
- FAU Erlangen-Nürnberg,
- OvGU Magdeburg,
- TU Dresden,
- ANKA synchrotron radiation source - KIT Karlsruhe
Deutsche Forschungsgemeinschaft (DFG, HA3088/7–1)
- S. Boden, M. Haghnegahdar, U. Hampel (2017).
Measurement of Taylor bubble shape in square channel by microfocus X-ray computed tomography for investigation of mass transfer.
Flow Measurement and Instrumentation 53, 49-55.
- S. Boden, T. dos Santos Rolo, T. Baumbauch, U. Hampel (2014).
Synchrotron radiation microtomography of Taylor bubbles in capillary two-phase flow.
Experiments in Fluids 55, 1768.
- H. Marschall, S. Boden, C. Lehrenfeld, C.J. Falconi D., U. Hampel, A. Reusken, M. Wörner, D. Bothe (2014).
Validation of Interface Capturing and Tracking techniques with different surface tension treatments against a Taylor bubble benchmark problem.
Computers & Fluids 102, 336-352.
- S. Aland, S. Boden, A. Hahn, F. Klingbeil, M. Weismann, S. Weller ( 2013).
Quantitative comparision of Taylor flow simulations based on sharp-interface and diffuse-interface models.
International Journal for Numerical Methods in Fluids 73, 344-361.