This merge requests adds three benchmarks for testing the mass advection scheme in the FSLBM:
- ZalesakDisk: 2D, slotted disk in constant rotating velocity field (https://dx.doi.org/10.1016/0021-9991(79)90051-2; https://dx.doi.org/10.1016/j.camwa.2009.08.064)
- SingleVortex: 3D, sphere that deforms in periodically changing velocity field (master's thesis from V. Haag: https://www10.cs.fau.de/publications/theses/2017/Haag_MT_2017.pdf)
- Deformation field: 3D, sphere that deforms in periodically changing velocity field with higher deformation than in the SingleVortex benchmark (master's thesis from V. Haag: https://www10.cs.fau.de/publications/theses/2017/Haag_MT_2017.pdf)
We evaluate the relative geometrical error compared to the initial shape of the slotted disk/spheres. These benchmarks are commonly used for codes implementing the volume-of-fluid scheme for mass advection. Note that the fluid dynamics simulation is deactivated in these benchmarks. A constant flow field is imposed in each time step.
Additionally, this merge request adds a new model for distributing excessive mass and renames some of the existing models.
The new model is called EvenlyNewInterfaceFallbackLiquid and distributes the excess mass evenly to newly created neighboring interface cells, if available. If there are no neighboring newly created interface cells, excessive mass is distributed evenly to older neighboring interface cells. If there are no neighboring interface cells, the excess mass is distributed evenly to liquid cells. However, the PDFs in these liquid cells is not modified, but the mass is stored in an additional field. In the subsequent timesteps, each liquid cell then distributes its excess mass to neighboring cells following the same sequence as described. Excessive mass in liquid cells will eventually be absorbed by an interface cell. The distribution of excess mass to liquid cells is inspired by the approach from M. Lehmann (https://doi.org/10.15495/EPub_UBT_00005400, p. 47). Note that any excessive mass stored in liquid cells, that is, in the excess mass field, does not participate in the flow simulation. Therefore, although the overall mass of the system is guaranteed to be conserved, mass conservation may be violated temporarily.