OC7 phase I: CFD investigation of viscous forces on rectangular members of semisubmersibles
Date
Apr 10 2026
Reading time
2minutes
This paper presents results from a collaborative research effort within OC7 Phase I, focusing on viscous forces acting on the rectangular members of semisubmersible platforms. High‑fidelity computational fluid dynamics (CFD) simulations are used to examine how these forces are represented in engineering‑level hydrodynamic models.
The study combines two‑and‑a‑half‑dimensional (2.5D) CFD simulations of pontoon sections with full three‑dimensional (3D) simulations of complete platform geometries. Two semisubmersible designs are investigated: the VolturnUS‑S and the INO WINDMOOR. Forced oscillation simulations are performed across a range of Keulegan–Carpenter numbers to derive added mass and drag coefficients commonly applied in design tools. A key outcome is the comparison between coefficients obtained from 2.5D and 3D simulations. The results show a consistent variation of hydrodynamic coefficients along the pontoon legs, driven by three‑dimensional platform effects and free‑surface interactions.
These findings underline the limitations of uniform coefficient assumptions in simplified models. With its extensive simulation matrix and component‑level analysis, the work establishes a valuable database and proposes empirical formulas to support more accurate selection of hydrodynamic coefficients for semisubmersible platform modelling in engineering practice.