Modelling of moving parts in CFD is quite difficult and often requires specialised techniques to be used. Example techniques are mesh morphing, the overset mesh technique and dynamic meshing. For this particular case, the dynamic meshing technique was chosen. During the entire simulation, it needed to be made sure that the mesh remains of sufficient quality to assure simulation quality and convergence.
The modelling of multiple fluids can be done in several ways. Several fluid phases can be solved simultaneously with either a fixed boundary between them (VOF method) or a mixed approach. Another possibility is to track (massless) particles. The latter technique was used in this case, mainly because of its convergence speed and clear visualisation of the solution.ir. Christopher Lynch, Simulation Engineer at Code Product Solutions