Computational Investigation of Internal Fluid-Structural Dynamics in Automotive Shock Absorbers

Automotive shock-absorbers performance is heavily influenced by complex internal dynamics involving flexible valves and damper oils, that cannot be fully described by analytical models and difficult to be experimentally characterized. Therefore, multi-physics simulations, describing the mutual interaction between fluids and solid structures, would greatly improve the design and optimization of dampers. A 2-way Fluid-Structure Interaction (FSI) computational setup, using open-source software, and tailored for a real monotube automotive damper geometry with shim-stack-valve, has been developed. Internal flow field and structural analysis are solved with OpenFOAM and CalculiX respectively, coupled with the preCICE library for partitioned multi-physics simulations. In order to describe the structural dynamics of the reference shim-stack, FEA has been performed in CalculiX, and the significant effect of sliding contact between the thin flexible shims is proven. However, since the implementation of this type of contact turned out to be source of coupling divergence in the FSI simulations, the valve assembly has been successfully modelled as an equivalent continuous structure, characterized by an equivalent stiffness. Results proved the reliability of the coupling setup, that allows the mapping of force and displacement to perform in a physical way, while guaranteeing an efficient coupling performance and maintaining both coupling and individual solver stability. The strong interactions between internal flow field and asymmetrical valve dynamics have been shown, at least for small deformations.