HZDR baseline model strategy
The description of polydisperse bubbly flows via Eulerian-Eulerian CFD requires the use of a dozen closure models for the interfacial forces, the liquid turbulence and various bubble-bubble interactions. For each of those closures a multitude of empirical and semi-empirical models exist in the literature. In the multiphase community there is no consensus about the use of those models nor their inherent model constants. Different research groups choose different sets of models even on a case-to-case basis.
The vision of our baseline strategy is to establish a fixed set of baseline models with reliable predictive abilities for all types of bubbly flow in any geometry. The optimal closure models are mechanistic models based on local flow conditions producing convincing results for a large set of validation cases. The scheme below illustrates the strategy of the continuous development, analysis and testing of new models using the growing number of validation cases.
In order to pursue this strategy a workflow for the fully-automated analysis of OpenFOAM simulations is regularly applied to an extensive collection of well-established pipe flow and bubble column cases. The fast and efficient production of large amounts of results which are summarized in well-structured reports allows us to facilitate new tools for the post-processing of data. A fuzzy logic controller has been introduced in order to quantify the agreement of our simulations with the available validation data as illustrated in the following figure. Such systematic evaluation of new models aims to contribute to a more sustainable baseline model development in the future.
- Lucas, D.; Rzehak, R.; Krepper, E.; Ziegenhein, Th.; Liao, Y.; Kriebitzsch, S.; Apanasevich, P., A strategy for the qualification of multi-fluid approaches for nuclear reactor safety, Nuclear Engineering and Design 299 (2016), 2-11.
- Hänsch, S.; Evdokimov, I; Schlegel, F.; Lucas, D., A workflow for the sustainable development of closure models for bubbly flows, Chemical Engineering Science 244 (2021), 116807.