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Experimental and numerical studies into the pontoon effect on vortex-induced motions of deep-draft semi-submersibles

Lookup NU author(s): Dr Longfei Xiao, Yibo Liang, 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.

Publication metadata

Author(s): Liu M, Xiao L, Liang Y, Tao L

Publication type: Article

Publication status: Published

Journal: Journal of Fluids and Structures

Year: 2017

Volume: 72

Pages: 59-79

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

Publisher: Elsevier


DOI: 10.1016/j.jfluidstructs.2017.04.007


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