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Lookup NU author(s): Professor Hongjun Zhu, Dr Narakorn SrinilORCiD
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).
© 2021 Elsevier LtdVortex-induced vibrations and solid-structure impacts of a horizontal flexible pipeline in the vicinity of a bottom wall boundary are experimentally investigated in a water flume. A neutrally-buoyant submerged pipe, with a length-to-diameter ratio of about 87 and fixed end supports, is subject to a shear flow with an oblique angle of 30°. The initial gap-to-diameter ratio between the wall and the pipe is equal to 0.2. A non-intrusive measurement with high-speed cameras is employed to simultaneously capture the space–time varying in-line and cross-flow vibrations in the normal flow reduced velocity range of 3–15 with a maximum Reynolds number of about 2780. Experimental results highlight new pipe equilibrium profiles and modal response branches being significantly broadened due to the wall proximity. Two solid-pipe impact features are discussed, including single-segment and two-segment alternating impacts depending on the dominant oscillation mode of the flexible pipe. Both the response amplitude and frequency increase with the reduced velocity, resulting in a more frequent impact with a greater impact force. A temporal evolution from a single point contact to a segment contact is observed for the two-segment alternating impact. Nevertheless, the lengths of the two contact segments are different as a result of the asymmetric response profile. In all cases, the pipe transversely impacts the bottom wall introducing a perturbation transmission along the pipe, which leads to the multi-mode, multi-frequency and asynchronous in-line and cross-flow oscillations with a 1:1 and 2:1 resonance. Due to a momentum energy consumption, the pipe experiences a slow post-impact bouncing phenomenon, contributing to a longer temporal period of the fluid–pipe interaction with a wall impact.
Author(s): Zhu H, Zhao H, Srinil N
Publication type: Article
Publication status: Published
Journal: Journal of Fluids and Structures
Year: 2021
Volume: 106
Print publication date: 01/10/2021
Online publication date: 25/08/2021
Acceptance date: 06/08/2021
Date deposited: 27/08/2021
ISSN (print): 0889-9746
ISSN (electronic): 1095-8622
Publisher: Academic Press
URL: https://doi.org/10.1016/j.jfluidstructs.2021.103356
DOI: 10.1016/j.jfluidstructs.2021.103356
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