Open Access

Matthias Graf, Tobias Lankenau, Kathrin Ottink, Thomas Ebel

• After their assembly, dynamic seals operate in a highly deformed and, therefore, pre-tensioned configuration. The geometrically enforced elastic pre-stress is essential for the sealing effect, which minimises the fluid passing through the seal gap. When moving, a thin film of the fluid is transported through the seal gap to the opposite side of the seal. The mechanics of this fluid film can be described, for instance, using the Reynolds equation for thin-film flow. However, the Reynolds equation is limited to the thin gap and can hardly be applied outside; the “thin gap assumption” is avoided here. Additionally, the geometry penetration of the undeformed seal leads to a system that cannot be meshed at the start of a coupled fluid-structure simulation. We provide a method for solving this type of system using COMSOL Multiphysics. In the first step, solid body contact builds up the elastic pretension. In the following step, the solid body contact is incrementally replaced by fluid pressure induced by an increasing rod movement. The developed model is capable of describing the full loss of solid body contact. It can be applied to simulate local fluid backflow in the vicinity of the seal gap.