Identification of the dynamic properties of a fluid inerter

To control vibrations in structures, the mitigation effect of well-known passive control devices such as Tuned Mass Dampers can be used. Since the effectiveness of these devices strongly depends on their mass, the so-called inerter can be exploited to fictitiously increase their mass, allowing a mass amplification effect without any physical addition. The present study aims to identify the dynamic properties of a fluid inerter, consisting of a hydraulic cylinder connected by an external pipe filled with fluid. A test campaign is conducted to reveal the actual behavior of this device, focusing on the effects of its nonlinearities. Specifically, the following nonlinear effects are revealed: energy dissipation due to friction of the piston and pressure drops due to the viscosity of the fluid in the external pipe and at the inlet and outlet. An accurate mechanical model of the device is determined and its efficiency demonstrated by means of comparative numerical studies. The nonlinear layout provides more realistic response predictions than a common linear model and can be implemented in several structural control device configurations.