The work aims at assessing a good methodological approach for lubrification system simulation having three Gerotor pump. It will study a case that has the movement of the mesh (Overset Mesh), with a mul-tiphase fluid. Moreover, it has been studied the possible fluid-dynamics problem inside the pumps, like phenomenon of cavitation.
The activity has been developed at “R&D CFD SRL” in Modena, with the collaboration of a prestigious local automotive company. The models were built using CFD software STARCCM+ ver.2019.2, licensed by Sie-mens.
The Overset Mesh technique consists of a system of grids, spatially superimposed on each other, which completely cover the fluid domain. During the calculation of the equations within the domain, the infor-mation around each individual grid must be transported to the adjacent grids through an interpolation process. In the case in question, the issue of moving the mesh within the region concerning the Gerotor pump will be addressed. A peculiarity of the case is that, unlike standard cases, the background mesh moves at a different speed than the Overset grid (instead of remaining fixed). The major advantage of using this technique is undoubtedly being able to simulate moving objects (and them meshes). On the contrary, there are some disadvantages such as the errors introduced by the interpolation process at the Overset Mesh interface and the additional computational cost. Unlike in open domains, in closed domains (like in this case) we have the introduction of an error relating to the conservation of mass. To this last error is also added the criticality of the presence of the model to simulate a multiphase fluid.
As a first approach, only the central pump was considered, with the Inlet and Outlet regions derived from extrusions (not considering therefore the inlet and outlet ducts). After defining a definitive mesh for the rotating regions, physics was added, initially including a single-phase fluid to interface with experimental data; subsequently we moved on to the multi-phase approach, considering the fraction volume directly from the tests provided by the company. The models used for simulation of multiphase case are the “VOF” (volume of fluid) and the “Eulerian Multiphase”. It has seen how, in the case treated in the thesis, the Eulerian model is more suitable to solve the problem.
Finally, the complete and simulated case was taken up, the entire system, consisting of the three pumps, the respective inlet ducts and the outlet duct in common with each other, to have a case as faithful as possible to the experimental tests.