Vortex-induced vibration (viv) suppression of riser arrays

Abstract

A system comprising an array of structures in a flowing fluid environment, the array comprising at least 3 structures; and vortex induced vibration suppression devices on at least 2 of the structures.

1 . A system comprising:
 an array of structures in a flowing fluid environment, the array comprising at least 3 structures; and   vortex induced vibration suppression devices on at least 2 of the structures,   wherein at least one of the structures comprise no vortex induced vibration suppression devices.   
     
     
         2 . The system of  claim 1 , wherein the array of structures are within a body of water. 
     
     
         3 . The system of  claim 2 , wherein the structures comprise first ends that are connected to a floating vessel, and second ends that project generally downward into the water. 
     
     
         4 . The system of  claim 1 , wherein the vortex induced vibration suppression devices are installed on from 20% to 80% of the structures. 
     
     
         5 . The system of  claim 1 , wherein the vortex induced vibration suppression devices are installed on from 30% to 60% of the structures. 
     
     
         6 . (canceled) 
     
     
         7 . The system of  claim 1 , wherein the array comprises at least one internal structure and a plurality of external structures that form a periphery about the internal structures, wherein the vortex induced vibration suppression devices are installed on from 40% to 65% of the external structures. 
     
     
         8 . The system of  claim 1 , wherein the flowing fluid environment comprises a predominant current direction, and wherein a structure in the array that first encounters the predominant current comprises at least one vortex induced vibration suppression device. 
     
     
         9 . The system of  claim 1 , wherein the vortex induced vibration suppression devices are selected from strakes and fairings. 
     
     
         10 . The system of  claim 1 , wherein the vortex induced vibration suppression devices comprise at least two different types of devices. 
     
     
         11 . The system of  claim 1 , wherein a first structure of the array of structures has a diameter at least 20% larger than a second structure of the array of structures. 
     
     
         12 . The system of  claim 1 , wherein the flowing fluid environment comprises a predominant current direction, and wherein a structure in the array that first encounters the predominant current comprises a diameter at least 15% smaller than another structure in the array. 
     
     
         13 . The system of  claim 1 , wherein the array comprises at least 6 structures. 
     
     
         14 . The system of  claim 1 , wherein the structures comprise a tubular, each tubular comprising an opening therethrough for transportation of a fluid. 
     
     
         15 . A method of suppressing the vortex induced vibration of an array of structures comprising:
 installing vortex induced vibration suppression devices on from 10% to 90% of the structures.   
     
     
         16 . The method of  claim 15 , further comprising connecting a plurality of the structures to each other. 
     
     
         17 . The method of  claim 15 , further comprising modifying a diameter of at least one of the structures, so that a first structure of the array of structures has a diameter at least 30% larger than a second structure of the array of structures. 
     
     
         18 . A system comprising:
 an array of structures in a flowing fluid environment, the array comprising at least 3 structures, wherein the structures are coupled to each other at a plurality of locations along a length of the structures; and   vortex induced vibration suppression devices on at least 2 of the structures, and wherein at least one of the structures comprise no vortex induced vibration suppression devices.   
     
     
         19 . The system of  claim 18 , wherein the vortex induced vibration suppression devices are installed on from 20% to 90% of the structures. 
     
     
         20 . The system of  claim 18 , wherein the vortex induced vibration suppression devices are installed on from 40% to 70% of the structures. 
     
     
         21 . The system of  claim 1 , wherein the at least 3 structures are risers. 
     
     
         22 . The system of  claim 21 , wherein the risers are arranged parallel to each other, and wherein vertically spaced spacers are provided along the risers to hold the risers in position relative to each other. 
     
     
         23 . A method of suppressing the vortex induced vibration of an array of structures comprising:
 installing vortex induced vibration suppression devices on at least 2 but not all of the structures.   
     
     
         24 . A process for liquefying natural gas, comprising:
 providing a system comprising a floating vessel on a body of water, and an array of structures, the array comprising at least 3 structures, wherein the structures comprise first ends that are connected to the floating vessel and second ends that project generally downward into the water, and vortex induced vibration suppression devices on at least 2 of the structures, wherein at least one of the structures comprise no vortex induced vibration suppression devices;   using the at least 3 structures as water intake risers for bringing water from the body of water to an FLNG plant on the floating vessel;   cooling and liquefying natural gas with the FLNG plant, wherein the water is input to heat exchangers of the FLNG plant in order to help liquefy the natural gas.   
     
     
         25 . A process for gasifying liquefied natural gas, comprising:
 providing a system comprising a floating vessel on a body of water, and an array of structures, the array comprising at least 3 structures, wherein the structures comprise first ends that are connected to the floating vessel and second ends that project generally downward into the water, and vortex induced vibration suppression devices on at least 2 of the structures, wherein at least one of the structures comprises no vortex induced vibration suppression devices;   using the at least 3 structures as water intake risers for bringing water from the body of water to an FLNG plant on the floating vessel;
 using the water in the FLNG plant to heat and gasify LNG.