Semi-submersible floating structure for vortex-induced motion performance

摘要

The disclosure provides a semi-submersible offshore platform with columns having an enlarged base on the bottom of each column with pontoons coupled between the columns. The enlarged column base can be at least as high as a height of the pontoon and on at least embodiment can be about 50% of the draft of the platform. The enlarged base can change a current flow shape around the base and columns for lower VIM. An outside corner of the base can be trimmed at an angle. Alternatively, the lower portions of the columns can be extended horizontally outward to form an effectively enlarged base having similar characteristics. In some embodiments, the pontoon volume can be reduced inversely proportional to the base enlargement to have comparable total buoyancy.

主权项

1. A semi-submersible floating offshore structure with improved vortex-induced motion (VIM), comprising:
a plurality of columns coupled to a deck and spaced apart from each other, the columns having a column height measured from a bottom of the columns to the deck, the columns being subject to lock-in based on factors of velocity of fluid currents, natural period of the floating structure in calm water without current, and diameter or width of column; at least two column bases coupled to at least two columns, the column bases having a base height; and at least two pontoons coupled to at least one of the column bases, the columns, or a combination thereof, the pontoons having a pontoon height; wherein the semi-submersible floating offshore structure is coupled to a plurality of catenary mooring lines and has a draft height for floating in water, and at least one of the column bases has a base height of 20% to 60% of the draft height so that the column base is underwater when the semi-submersible offshore structure is floating in the water and has an extension width that is at least 10% of a width of a column coupled to the at least one column base, wherein at least one column base is configured to break a coherence in vortex shedding around the offshore structure by creating interfering vortex currents around at least one of the columns to reduce VIM caused by the lock-in.