A multi-scale modelling approach for industrial multiphase flows

A new modelling approach for gas-liquid flows which involve a wide spectrum of typical length scales for the interfaces between the phases is presented. It aims on medium and large scale industrial applications and bases for that reason on the multi-fluid approach. In many flow situations dispersed and segregated morphologies of the phases occur not only simultaneously, but the flow is characterized by transitions between these morphologies. The recently developed GENTOP concept provided a modelling frame for such flow situations. Examples for application are bubble entrainment by jets impinging on a liquid pool, flashing flows, e.g. in the feed line of distillation columns, flows in column tray and many others. The inhomogeneous MUSIG approach is extended to include beside a number of bubble size classes also a continuous gas phase. Interfaces which are at least 4 times larger than the cell size of the numerical grid are resolved, while smaller structures are handled as dispersed phase as usual in Euler-Euler methods. The resolved interfaces are treated in a similar way as in the Algebraic Interfacial Area Density model (AIAD). Transitions between these different morphologies are considered as coalescence and breakup processes. In several demonstration cases the capabilities of the concept are shown.