Geometrical assumptions regarding viscous fluid dampers

Abstract

The specific innovative device presented in this paperwork is a hydraulic system operating with viscous fluid that provides damping for shocks and vibrations. A basic viscous fluid device is constructed on the principle of linear hydraulic motor (cylinder with a plunger), but the device presented here has a certain number of orifices made inside the piston head. This allows the fluid circulation during the forced displacement of the piston within the cylinder body, without the need of any external hydraulic connection. Therefore it may be considered to be a passive system that will run without any other attached devices, on a passive principle. Typically, this particular device is used for bridges or viaducts endowment, as connection point between structural elements (base pier and path-way) ensuring in this way a safe anchoring and displacements limitation for the superstructure, especially when unexpected dynamic actions occur. The viscous fluid device operation achieves an energy dissipation role, because it opposes to the relative motion between structural frames, where it was positioned. Due to the viscosity properties of the working fluid, the piston
movement is strongly attenuated and the energy received from the environment is partially consumed by the internal viscous friction, then it is transmitted back to the external environment, as heat energy. The value of the diameter of crossing orifices made in the piston head is important for an adequate operation of the viscous fluid device. Therefore, in this paperwork are presented the CFD analysis results obtained for a virtual model of a hydraulic device, when the orifices diameter is changed.