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 2 - Square-Columns Arrangements
Submission Author:
André Fujarra , SC
Co-Authors:
Adriana Wallbach, Karen Soares, Gabriel de Paula Dittrich, André Fujarra
Presenter: Adriana Wallbach
doi://10.26678/ABCM.COBEM2023.COB2023-1953
Abstract
In addition to circular columns, semi-submersible platforms and FOWT also feature columns with square sections. This geometry is easily modularized during construction, making it an attractive choice from a constructive point of view. Regarding the phenomenon of FIV, square-section columns exhibit different behaviors at different angles of attack of the flow. Therefore, to seek a better solution for column arrangements, square-section geometries should also be considered, not just circular ones. Due to the large number of conditions to be considered for each column arrangement, a second part of this work was conducted to provide a more complete and accurate analysis. The complementary objective was to analyze the phenomenon of FIV through experiments with ultra-reduced models in arrangements composed of three or four cylinders of square cross section. Again, the distances S between the cylinders were determined by the width D of their square cross section, with ratios of S/D = 2, 3 and 4. For comparisons, the same aspect ratio T /D = 2 (where T is the column draft) and a reduced mass m∗ ≈ 1.83 were also considered here. In terms of incident flow directions, angles of attack of 0, 90 and 180 degrees were tested for three-column arrangements and 0 and 45 degrees for the four-column arrangements. The experiments were carried out at the same seven different reduced velocities, ranging from 4.34 to 9.56. Inline and cross-flow displacements were captured through an MCS, to determine dimensionless amplitudes and frequencies. Data were processed and analyzed through computational routines in Octave, using techniques of statistics and uncertainty, as well as Fourier analysis. Comparative analyzes with equivalent results found in experimental studies with higher Reynolds numbers and numerical studies validated this work, and therefore it was concluded that CWC experiments with low Reynolds numbers are an effective, economical, and faster approach to evaluate semi-submersible floater arrangements for FOWT, reconfirming the original contribution in Part 1 of this work.
Keywords
Flow-induced Vibrations, Low Reynolds Numbers, Square-Columns Arrangements, Circulating Water Channel (CWC), Ultrareduced Models, two degrees of freedom
