Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Multiregime closure models for the two-fluid model often focus on continuous-dispersed and large-scale interface flow morphologies (Cerne, Petelin and Tiselj, 2021), (Hänsch et al., 2012), (Mathur et al., 2019).
Thin liquid films at solid walls, e.g. in annular flow or film condensation, so far have not been considered in a multi-regime two-fluid (MTF) model.
Rather, thin liquid films are currently treated as large-scale interfaces.
The film interface thus has to be resolved, which is conflicting with the two-fluid model approach and increases computational cost.
For the interface resolving volume-of-fluid method, coupling to a liquid film (LF) model was previously proposed to treat subgrid size liquid films (Kakimpa, Morvan and Hibberd, 2016).
Here, we adapt this approach to the framework of the MTF model.
A film thickness transport equation and film momentum equation are solved in a shell region of the two-fluid model volume domain.
Mass- and momentum transfer between both models is included depending on a critical film volume fraction in the first cell at the wall.
Thus a hybrid representation of liquid films depending on the local film thickness is obtained in the proposed LF-MTF model.
The implementation in the CFD solver STAR-CCM+ is outlined and a basic verification case is presented.
Validation results of LF-MTF model simulations against X-ray microtomographic data of horizontal annular flow (Porombka et al., 2021) show qualitative agreement and outline paths for further model improvement.
Finally, simulation results of droplet separators demonstrate the applicability of the LF-MTF model to industrial CFD.