Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Experiments of Flow-Induced Vibration on Models in Regimes of Low Reynolds Numbers: PART 1 - Circular-Columns Arrangements
Submission Author:
André Fujarra , SC
Co-Authors:
Monique Ellen Bruner, Karen Soares, Gabriel de Paula Dittrich, André Fujarra
Presenter: André Fujarra
doi://10.26678/ABCM.COBEM2023.COB2023-1952
Abstract
Flow-induced vibration (FIV) is a phenomenon that arises from the interaction between fluid flow and flexible or elastically supported structures, with consequences that must already be considered in the initial stages of the design of engineering systems affected by it. The FIV comes from the synchronization between the vortex-shedding frequency and one of the natural frequencies of the system. From this synchronization, self-excited and self-controlled oscillations occur with amplitude close to the characteristic dimension of the system, which can be an isolated cylinder or arrangements of them. Exactly in this sense, the present work aims to experimentally investigate the VIE phenomenon on ultra-reduced models in the Circulating Water Channel (CWC) of the UFSC-Joinville, with a view to screening arrangements for floaters of Floating Offshore Wind Turbines (FOWT), considering that the promising cases can be furthermost investigated via CFD at full-scale Reynolds numbers, but also considering that, by themselves, the experimental results herein obtained already serve as validation for numerical simulation models in the same Reynolds number range. The ultra-reduced models of this Part 1 are arrangements of three or four circular columns, equidistant from each other of S = 2D, 3D and 4D (where D is the diameter of the column), and tested according to the headings at 0, 45, 90 and 180 degrees, depending on the arrangement. All the arrangements tested had an aspect ratio T /D = 2 (where T is the column draft) and a reduced mass m* ≈ 1.83. Incident flows are characterized by low Reynolds numbers between 598 and 1318, equivalent to seven different flow velocities that essentially maintain the phenomenology of VIE, as is known. Inline and cross-flow displacements are recorded from a Motion Capture System (MCS) to determine the dimensionless amplitudes and frequencies of VIE using statistical and uncertainty analyses, as well as the Fast Fourier Transform (FFT). Comparisons with results found in the literature, but at higher Reynolds numbers, reinforce that the arrangements with smaller spacing show smaller oscillation amplitudes and that the heading angle does not appreciably influence the results for the arrangements with the highest column distance. Therefore, it can be stated that CWC experiments with low Reynolds numbers definitely serve as a faster and cheaper methodology for screening arrangements such as those of FOWT – the original contribution of this work.
Keywords
Flow-induced Vibrations, Low Reynolds Numbers, Circular-Columns Arrangements, Circulating Water Channel (CWC), Ultrareduced Models, Two Degees of Freedom
