Numerical simulation of fluid flow inside a valve for an automotive shock absorber

The considered shock absorber system is mainly controlled by valves that employ circular discs. It has an oil passage controlled by two ways, regarding to velocity. For low velocities, the oil passes through small bleeds on the discs. As the velocity gets higher, the pressure induced by the flow warps the disc and then increases the oil passage area. In order to improve the shock absorber design and get a better understanding of the fluid flow, Magneti Marelli COFAP and ESSS engineers have developed a computational model for low velocity condition, evaluating dispersion of forces at the discs and comparing the results against experimental data, measured at Magneti Marelli COFAP facilities. Simulation of the steady-state flow has been performed using ANSYS CFX. For the low velocity condition, three configurations have been simulated, where the oil passage area has been the parameter to be varied. The force has been obtained by pressure integration. The final results have been satisfactory, considering the imprecision and the tolerances generally accepted in a laboratory test environment.