Patent ID: 8757081
Filing Date: 2014-06-24
Classification: B63B,Y10T

Abstract:
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.