Speaker
Description
Computational Fluid Dynamics becomes more and more important for industrial applications that involve multiphase flows. For such flows in medium and large scales the Euler-Euler approach is most frequently used and often the only feasible one. In many flow situations, the involved interfaces cover a wide range of scales leading to different coexisting morphologies. Established simulation methods differ for the individual interfacial scales. Large interfaces are represented in a resolved manner typically based on the one fluid approach, e.g. Volume of Fluid (VOF) or Level Set. Unresolved (dispersed) flows are modelled using the two- or multi-fluid approach. A simulation method that requires less knowledge about the flow in advance would be desirable and should allow describing both interfacial structures – resolved and unresolved – in a single computational domain.
The morphology adaptive multifield two-fluid model MultiMorph, which is developed at HZDR, is able to handle unresolved and resolved interfacial structures coexisting in the computational domain with a unified set of equations. An interfacial drag formulation for large interfacial structures is used to describe them in a VOF-like manner, while the usual closure models are applied for the unresolved phases. In addition, MultiMorph allows to simulate transitions between the morphologies. This concerns both physical transitions such as entrainment and detrainment as well as transitions resulting from a change in the size of the numerical mesh within the domain, if this changes the resolvability of a phase interface. This also includes the appropriate modelling of under-resolved interfaces and over-resolved bubbles or droplets.
Examples for the application include 3D simulations on bubble entrainment by a plunging jet, complex flow at a tray of a distillation column and drag reduction by bubble injection below a ship hull.
Meller, R., Schlegel, F., \& Lucas, D. (2021). Basic verification of a numerical framework applied to a morphology adaptive multifield two‐fluid model considering bubble motions. International Journal for Numerical Methods in Fluids, 93(3), 748-773. 10.1002/fld.4907.
Meller, R., Tekavčič, M., Krull, B., \& Schlegel, F. (2023). Momentum exchange modeling for coarsely resolved interfaces in a multifield two-fluid model. International Journal for Numerical Methods in Fluids, 95(9), 1521-1545. 10.1002/fld.5215.
Schlegel, F., Meller, R., Krull, B., Lehnigk, R., Tekavčič, M. (2023). OpenFOAM-Hybrid - A Morphology Adaptive Multifield Two-Fluid Model. Nuclear Science and Engineering, 197(10), 2620-2633. 10.1080/00295639.2022.2120316.
Schlegel et al. (2024). Multiphase Code Repository by HZDR for OpenFOAM Foundation Software (Version 12-s.1-hzdr.1), Rodare. http://doi.org/10.14278/rodare.3284
