Modeling Film Stripping
In Simcenter STAR-CCM+, you can model fluid being removed from a film due to wave stripping across the surface, or edge stripping on sharp corners.
Waves generate instabilities on the surface, and these instabilities form droplets which are stripped off the film. These droplets are entrained in the bulk fluid flow. Similarly, droplets are also stripped from the film when the fluid film flows over a sharp edge.
You can model film stripping in Eulerian Multiphase (EMP), Lagrangian Multiphase, Mixture Multiphase (MMP), and Dispersed Multiphase (DMP) simulations. A particular fluid film phase can have only one edge stripping phase interaction and one wave stripping phase interaction.
Both wave stripping and edge stripping are supported for Implicit Unsteady simulations and for most Steady simulations. The exception for Steady simulations is that wave stripping to a Eulerian phase in a Eulerian Multiphase (EMP) simulation is not supported. When modeling film stripping to a Lagrangian phase, wave stripping and edge stripping are also supported for PISO Unsteady simulations.
Film Stripping in Lagrangian Multiphase Simulations
Droplets that enter the bulk flow are tracked using the Lagrangian Multiphase model in Simcenter STAR-CCM+.
Setting up a film stripping simulation includes the same basic technique of setting up a fluid film shell region. Lagrangian features are added with the selection of Lagrangian Multiphase in the continuum, activating wave and/or edge stripping, and using film stripping injectors.
It is possible for droplets to form on the surface of a fluid film, and to be immediately forced back into the film on the subsequent time step.
Film Stripping in Mixture Multiphase (MMP) Simulations
For Mixture Multiphase (MMP) simulations, the Film-MMP Phase Topology model supports both wave stripping and edge stripping from the fluid film into the dispersed MMP phase. Both single-component and multi-component liquid phases are supported.
Film Stripping in Dispersed Multiphase (DMP) Simulations
The Dispersed Multiphase model can be used as a lightweight replacement for Lagrangian particles in simulations where the Lagrangian Multiphase model is too computationally expensive due to the large number of particles. Wave and edge stripping transfers droplets from the fluid film phase into the dispersed phase of a Dispersed Multiphase simulation. Using Dispersed Multiphase particles for icing and soiling simulations is significantly quicker than using Lagrangian particles.
In contrast to the Lagrangian Multiphase model, the Stripping model does not compute the size of the stripped droplets that are added to the dispersed phase: all of the droplets produced have the same user-defined diameter. The fact that the droplet diameter remains constant influences associated models that depend on the droplet diameter, such as drag force. Each stripping model contributes to one dispersed phase only. However, it is possible to set up different stripping models, each of which contributes to a different dispersed phase.
Only single-component fluid film is supported, as Dispersed Multiphase uses a single-component dispersed phase.
Film Stripping in Eulerian Multiphase (EMP) Simulations
For Eulerian Multiphase simulations, the Film-EMP Phase Topology model supports both wave stripping and edge stripping from the fluid film into the liquid Eulerian phase. Only single-component liquid phases are supported.