Further numerical studies on passive suppression of flow-induced vibrations

Abstract

Flow-induced vibrations (FIV) are commonly found in several technological applications and concern the existence of self-excited oscillations that may impact the structural lifespan. Hence, it is of interest the development of studies focusing on solutions that mitigate these vibrations. Among the suppression techniques, focus is placed on the passive one. Passive suppression does not need energy input and is achieved by coupling a sub-structure to the main system. Particularly, this research focuses on a special kind of suppressors characterized by an essentially non-linear dynamics, known as rotative non-linear vibration absorbers (NVA). Herein, a rotative NVA is composed of a bar with a tip-mass coupled to the main structure by means of a linear dashpot. The bar can be either rigid (RNVA) or elastic in the axial direction (ERNVA). Two FIV phenomena are focused, namely vortex-induced vibration (VIV) of rigid and elastically mounted cylinders and vibrations due to the internal flow in a pipe discharging fluid. For both these FIV phenomena, numerical studies will be carried out, aiming at identifying the influence of the NVA parameters on its efficiency. Provided the VIV mitigation has already been investigated in a previous regular project sponsored by FAPESP, passive suppression of this phenomenon will be investigated considering only the ERNVA device. For this phenomenon, the fluid loads will be calculated using wake-oscillator models. On the other hand, only the RNVA will be considered as a passive suppressor for vibrations induced by the internal flow in a pipe discharging fluid. The equations of motion will be derived using extended the Hamilton's principle. At the end of the project, it will be obtained numerical simulators for the addressed problems as well as graphics and tables showing the efficiency of the devices as functions of their control parameters. As shown in the literature review, this proposal presents novelties with respect to the state-of-art. (AU)