Investigation on the VIM Mitigation of the HVS Semisubmersible

Kyoung, Johyun; Kim, Jang Whan; Jang, Hyunchul; Lambrakos, Kostas F.; O’Sullivan, Jim

doi:10.1115/omae2015-41188

Cited by 9 publications

(2 citation statements)

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“…The lower part of each column has been wrapped by a blister, which redistributes displacement of pontoons and the base of the columns. Due to this arrangement, the heave motion and VIM may be suppressed (Kyoung et al, 2015). Because of the blisters attached to the columns, the coherence of vortex shedding can be broken (Xu, 2011).…”

Section: Heave and Vim Suppressed Semi-submersiblementioning

confidence: 99%

Multi-objective optimization of semi-submersible platforms using particle swam optimization algorithm based on surrogate model

et al. 2019

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An Innovative Semi-submersible platform Optimization Program (ISOP) has been developed to solve the multiobjective optimization problem for semi-submersible platforms (SEMI). Three types of SEMIs, including semisubmersible floating production unit (SEMI FPU), heave and vortex induced motion (VIM) suppressed semisubmersible (HVS) and semi-submersible floating drilling unit (SEMI FDU) are selected for case studies. The hydrodynamic performances of three types of semi-submersible platforms are analyzed by using panel method and Morison's equation. In order to improve the computing efficiency, the hydrodynamic performances for different hull forms during optimization process are estimated by the surrogate models, which are built by artificial neural network prediction method and Inverse Multi-Quadric (IMQ) radial basis function (RBF). The accuracy of surrogate models is ensured by performing leave-one-out cross validation (LOOCV). The most probable maximum (MPM) heave motion and total weight, representing the safety and economy, respectively, are chosen as the two objectives for optimization. The transverse metacentric height, the MPM surge motion, and the most probable minimum (MPMin) airgap are selected as constraints. Based on surrogate models, multi-objective particle swarm optimization (MOPSO) is employed to search for the Pareto-optimal solutions. A Computational Fluid Dynamics (CFD) tool is adopted to validate the proposed model for the prediction of the motion responses. By comparing the obtained Pareto-optimal solutions with the initial design using simple panel method plus Morison's equation, it is confirmed that the MPM heave motions for SEMI FPU, HVS and SEMI FDU can be suppressed by up to 12.68%, 11.92%, and 14.96%, respectively, and the total weights can be reduced by up to 12.16%, 13.00%, and 24.91%, respectively. Through the detailed analyses of optimization results, the most efficient design strategies for semi-submersible platforms are discussed and proposed.

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Section: Heave and Vim Suppressed Semi-submersiblementioning

confidence: 99%

Multi-objective optimization of semi-submersible platforms using particle swam optimization algorithm based on surrogate model

et al. 2019

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“…Other designs could possibly be appendages or changes in the geometry of the columns, for example by adding volume in the middle of each column, thereby breaking up the coherence of vortexes shedding along the length of the column. An example of this is the 'Heave and VIM Suppressed' (HVS) semi-submersible proposed by Kyoung et al (2015), adding volume at the bottom of the column to break up the coherence of vortex shedding along the column.…”

Section: Vorticitymentioning

confidence: 99%

Full-scale CFD investigations of helical strakes as a means of reducing the vortex induced forces on a semi-submersible

2017

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This version is available at https://strathprints.strath.ac.uk/60458/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output.1 | P a g e ABSTRACTAs the search for oil in the Gulf of Mexico (GoM) moves into deeper waters, floating platforms such as semi-submersibles are in increasing demand. As semi-submersibles increase in size, the effect of vortex-induced motions (VIMs) becomes a significant problem in their design. VIMs stem from transverse forces caused by the current affecting the platform, with vortexes moving downstream on either side of the structure. The loop/eddy current phenomenon in the GoM leads to a constant current being present in the area, with speeds of up to 1.8 m/s. The accurate prediction of the vertical and transverse motions of semi-submersibles is crucial for the design of the riser systems. It is therefore beneficial to investigate the hydrodynamic forces acting on the geometry, and means of reducing these forces. A common method of reducing transverse forces is the addition of column appendages, such as helical strakes. In this paper, full-scale computational fluid dynamic analyses are carried out to examine the transverse forces caused by this vortex shedding using realistic current velocities in the GoM. Helical strakes are attached to the geometry to break up the coherence of the vortex shedding and the performance of these strakes is investigated numerically.

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Experimental studies of the unsteady hydrodynamic loads on a tension-leg platform at high Reynolds numbers

Zhang

You

2019

Journal of Fluids and Structures

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Investigation on the VIM Mitigation of the HVS Semisubmersible

Cited by 9 publications

References 2 publications

Multi-objective optimization of semi-submersible platforms using particle swam optimization algorithm based on surrogate model

Multi-objective optimization of semi-submersible platforms using particle swam optimization algorithm based on surrogate model

Full-scale CFD investigations of helical strakes as a means of reducing the vortex induced forces on a semi-submersible

Experimental studies of the unsteady hydrodynamic loads on a tension-leg platform at high Reynolds numbers

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