Process mechanical engineering

Dr. Matej Tekavčič

Research programme: Nuclear engineering
Training topic: Modelling of heat and mass transfer in multiphase flows

Multiphase flows of gas and liquid can be found in a variety of industrial systems in process and chemical engineering, pharmaceuticals, resource extraction, and power generation, including nuclear reactors. Important properties, like pressure drop or heat transfer characteristics, are typically determined by interface topology between gas and liquid; even in simple configurations, such as pipe flow, several, often co-existing regimes can be observed, for example bubbly, slug and annular flow. To investigate and design such systems, simulations with computational fluid dynamics (CFD) represent an important complementary tool alongside experimental observation.

When flow and interfacial structures can be sufficiently resolved with the computational mesh, direct numerical simulations with interface tracking can provide detailed insights into flow phenomena and its mechanisms. Due to limited computational power, resolving all relevant physical scales is unfeasible for realistic, industrial scale applications. For these cases, the two-fluid model, a statistical approach based on phase averaging of the flow, is more appropriate, but requires additional modelling effort and validation. The two approaches, interface-resolving and statistical, can be combined into a hybrid model where additional specialised methods consider specific flow patterns and transitions, for example between continuous and dispersed interfacial structures. The aim is to reproduce multiple flow phenomena within a single, comprehensive computational tool.

PhD work will focus on advancement of such hybrid two-fluid models, specifically on the development of heat and mass transfer models that can adapt to the local interface morphology depending on the resolution of the computational mesh. The proposed approach should offer a good trade-off between accuracy and computational cost and is intended for practical simulations of industrial applications. Work will be performed in the scope of our international collaborative research to develop advanced simulation tools for multiphase flows using the open-source CFD library OpenFOAM.