Análise crítica de um modelo fenomenológico de vibrações induzidas por vórtices via análise de sensibilidade global e quantificação de incertezas

Abstract

The phenomenon of vortex-induced vibrations (VIV) is investigated in the present Dissertation. These vibrations are the result of the intricate fluid-structure interaction between the body and its external flow, being undesirable in the offshore industry. Therefore, phenomenological models continue to be developed and popularised to the prediction of VIV, allowing its low computational time to be explored via global sensitivity analysis (GSA) and uncertainty analysis, which could result in the model enhancement, allowing it to provide valuable information about the phenomenon. The GSA of a semi-empirical model with its sensitivity indices estimated by the Monte Carlo method was able to identify four input parameters (C L0, CDO, Ay and Ey) distinguishingly important to the outputs variability. Thus, the investigation and calibration of these parameters could improve the model capability. From the four highlighted input factors, Ay and Ey present a combined role which was verified to increase the model’s ability to simulate the lock-in interval, perhaps the critical imprecision of the original model. Meanwhile, CDO sensitivity patterns from the GSA results indicate that a more realistic approach for the parameter could be beneficial. In fact, according to the literature review, CDO is related to the cross-flow oscillation amplitudes. In this study, the approach to this dependence was followed by proposing a discontinuous function for CDO. It is possible to conclude that the analysed model with the proposed CL0, CDO, Ay and Ey is able to represent more accurately the tendencies, vibration frequencies, the lock-in and both inline and cross-flow oscillation amplitudes. Moreover, the study of different configurations and dynamic properties demonstrated that the methodology could be conducted similarly to a variety of systems and conditions.