It this week’s blog post we will keep looking into the news of the latest Simcenter Star-CCM+ version (2020.2). This time we will specifically look at the news related to Eulerian multiphase models. A lot of the updates will cover improvements to fluid film.
But initially we have a general improvement in terms of multiphase setup. The change reduces the risk of user error and reduces the setup time. You simply choose a phase and suitable partner phases are listed. When a pair is chosen the appropriate interaction is generated. The terminology is now updated to be more consistent.
Fluid Film – Explicit mapped contact interface
The Explicit Mapped Contact Interface is now compatible with Fluid Film. This opens multi-timescale CHT workflows with Fluid Film on the wall that forms the interface between the fluid and solid continua. This reduces the time taken to solution for cases where the flow and film need to be solved with a small timestep size, but the transient solution in the solid covers many 10s of minutes or even hours of real time.
The Explicit Mapped Contact Interface also allows FE solid energy to work alongside Fluid Film, which is typically preferred to the FV equivalent for CHT simulations.
Improvements to transition of Hybrid VOF-Film
The transition between Fluid Film and VOF at resolved hybrid VOF-film interfaces has been improved with the addition of an option to equalize the velocity between the Film and the VOF phases at transition. This leads to improved accuracy and a reduction of spurious effects around the transition location.
This option particularly benefits cases where a zonal approach is taken rather than using the default 0.5 volume fraction to transition between Film and VOF. In these cases, the Film layer may be thick compared to the first cell height at transition which can cause disturbances on the VOF side due to the large volume being transitioned. Equalizing the velocity either side of transition reduces these disturbances.
Mixture multiphase impingement into Fluid Film
MMP phases can now impinge into a Fluid Film, allowing MMP to be used for applications where there a thin fluid film forms on surfaces such as in annular flows. This allows MMP to be used for such applications instead of the more expensive EMP.
This enhancement also brings MMP into the hybrid multiphase family so that it is not only possible to use MMP alongside Fluid Film phases with impingement from MMP into Film, but also to use MMP with Lagrangian phases with stripping from the Film. This allows a strategy of using MMP phases for fine sprays and mists with LMP used for the larger droplets shed from the Film.
The example on the right shows such a case with a fine spray of MMP droplets impinging on a rotating gear wheel to form a Fluid Film. The Film thickness then builds up to the point where droplets are stripped from the edges of the gear teeth into LMP droplets.
Solidification and Melting with Liquid-Solid-Gas Multi-Component Fluid Film
The Fluid Film melting and solidification model has been improved and made more consistent with the modelling approach used elsewhere in Simcenter STAR-CCM+ by switching to use multi-component Liquid-Solid-Gas to represent the liquid and solid components of the film rather than the previous approach of using the model specific ‘Relative Solid Volume Fraction’. The old approach is maintained for backward compatibility.
The example shows an airfoil icing simulation at glaze ice conditions with liquid water being deposited around the stagnation point running back and freezing. This is then used in combination with morphing and solid removal to model the ice build-up.
I hope this has been useful to you as a Simcenter STAR-CCM+ user. Do not hesitate to contact me at firstname.lastname@example.org or at email@example.com if you have any questions. Tune in again next week for the continuation of what version Simcenter STAR-CCM+ 2020.2 has to offer, we will then look at the Lagrangian multiphase updates.
How to set up a CHT simulation using simulation operations
Simcenter Star CCM+- Volupe software
Release of Simcenter STAR-CCM+ 2020.2 part 4
How to run a basic simulation in Simcenter FloEFD
Simcenter STAR-CCM+ version 2020.3 news – part 4