Lookup NU author(s): Dr Longfei Xiao,
Professor Longbin Tao
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).
The vortex-induced motion (VIM) is a critical issue in mooring and riser system design for column-type deepwater platforms. As regards to deep-draft semi-submersibles (DDS), even though VIM is mainly excited by vortex shedding around columns, the large-volume pontoons beneath the columns are also responsible for the wake interference, implying a non-negligible influence on VIM behavior. An experimental study and three-dimensional numerical simulations were performed to analyze the pontoon effect on the VIM of two semi-submersibles and a four-column structure without pontoons. The numerical results using Detached Eddy Simulation (DES) are in good agreement with the experimental measurements obtained from the towing model tests. The present investigations indicate that the resonant phenomenon is observed for all configurations. However, the presence of pontoons delays the onset of VIM to a higher reduced velocity in the cases of the four-pontoon DDS. Additionally, the four-column structure with no pontoons shows the most significant transverse responses and yaw motions at both 0°- and 45°-incidences owing to the largest fluctuating lift forces induced by the well-established wake. The dominant frequency of the drag force for the DDS with two pontoons matches that of the lift force at a 45°-incidence, leading to an increase in the in-line response.
Author(s): Liu M, Xiao L, Liang Y, Tao L
Publication type: Article
Publication status: Published
Journal: Journal of Fluids and Structures
Print publication date: 01/07/2017
Online publication date: 08/05/2017
Acceptance date: 24/04/2017
Date deposited: 09/05/2017
ISSN (print): 0889-9746
ISSN (electronic): 1095-8622
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