Three-Dimensional Effects on Wave Forces on Horizontal Members of a Semisubmersible

概要

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It is known that wave-induced forces on horizontal cylinders are significantly decreased due to a circulating flow generated around the cylinder at low Keulegan-Carpenter numbers. An estimation method of wave forces on a two-dimensional horizontal circular cylinder using a simple vortex shedding model has been proposed by the authors. For estimating the wave forces on horizontal members of offshore structures like lowerhulls of a semisubmersible, however, it is necessary to clarify three-dimensional effects, such as the end effect or the juncture flow effect.In this paper, the end effect and the effect of columns on wave forces on a lowerhull submerged in regular waves with its axis parallel to the wave crests were experimentally investigated. A two-dimensional lowerhull cylinder and finite-length lowerhull models with and without columns are used in force measurements, velocity measurements and flow visualizations. The results of the experiments showed that the wave force reduction decreases in the case of the finite-length lowerhull model with columns due to the disappearance of the circulating flow at the end and the junctions with columns. The results also demonstrated that the vertical wave forces on the finite-length lowerhull model with columns are asymmetric because of the flow accelerated between the columns.
社団法人日本船舶海洋工学会の論文