Selective VIV Suppression for Riser Arrays to Reduce Equipment Cost
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Solution Overview
Problem
Existing systems fail to effectively reduce vortex-induced vibration (VIV) and drag on multiple structures in flowing fluid environments, particularly in marine settings, often requiring costly and complex installation and maintenance of VIV suppression devices on all structures.
Innovation Solution
A system where only a subset of tubular structures in an array or bundle are equipped with VIV suppression devices, such as strakes or fairings, strategically positioned to maximize frequency dissociation and reduce overall vibration, while others without devices are used for water intake or other functions, optimizing cost and installation complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VIV suppression devices are installed on all tubular structures, then vibration suppression effectiveness is improved, but equipment cost and installation complexity increase
Solution Approach 1:
The patent divides the array of tubular structures into multiple groups based on their exposure to ocean currents. VIV suppression devices are selectively installed only on structures in high-exposure groups rather than uniformly on all structures, segmenting the protection strategy to reduce overall complexity while maintaining effectiveness where most needed.
Solution Approach 2:
The patent applies different levels of VIV suppression based on local conditions of each tubular structure. Structures facing predominant ocean currents receive suppression devices, while those in sheltered positions do not, creating a non-uniform distribution that optimizes the balance between vibration suppression and installation complexity.
2Reliability
If VIV suppression devices are installed on all tubular structures, then vibration suppression effectiveness is improved, but equipment cost increases
Solution Approach 1:
The patent segments the tubular structure array into groups based on current exposure, installing suppression devices only on a subset of structures in high-exposure groups. This selective segmentation reduces the total quantity of suppression devices required, directly lowering equipment costs while maintaining adequate protection.
Solution Approach 2:
The patent implements partial action by installing VIV suppression devices on only some of the tubular structures rather than all of them. Specifically, devices are installed on structures in groups that face predominant ocean currents, accepting that structures in other groups will have less suppression, thereby reducing overall equipment cost.
3Force
If longer fairings are used, then drag resistance is improved, but structural stability deteriorates due to instabilities
Solution Approach 1:
The patent applies partial action by installing fairings on only a subset of tubular structures rather than all structures. This allows the use of longer fairings with better drag resistance on selected structures without requiring that all structures use long fairings, thereby reducing the overall stability issues while maintaining adequate drag resistance where most critical.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces VIV and drag on tubular structures with fewer suppression devices, lowering equipment costs and simplifying installation and maintenance, while maintaining effective vibration suppression, especially on structures facing predominant ocean currents.
Implementation Method 1
Whenever a bluff body, such as a cylinder, experiences a current in a flowing fluid environment, it is possible for the body to experience vortex-induced vibration (VIV). When fluid flows past the structure, vortices may be alternately shed from each side of the structure.
Implementation Method 2
Devices used to reduce vibrations caused by vortex shedding from sub-sea structures may operate by modifying the boundary layer of the flow around the structure to prevent the correlation of vortex shedding along the length of the structure.
Implementation Method 3
The second type of stress may be caused by drag forces, which push the structure in the direction of the current due to the structure's resistance to fluid flow.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3F
AI summary
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.