Segmented Flow Modification Device for VIV Suppression
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Solution Overview
Problem
Cylindrical structures such as marine risers and pipelines experience vortex-induced vibration (VIV) and increased drag when immersed in fluid media, leading to reduced operating life due to fatigue, and existing flow modification devices are either impractical for handling or time-consuming to deploy.
Innovation Solution
A flow modification device with an elongate body featuring raised body portions, such as curved or trapezoidal ridges, that are offset or rotated along its length to reduce VIV and drag, and can be easily connected and secured to cylindrical elements using a clamping mechanism or straps, allowing for efficient deployment and reduced vibration amplitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If helical strakes are used to reduce VIV, then vibration severity is reduced to very small levels, but the device becomes large and impractical to handle
Solution Approach 1:
The flow modification device is divided into multiple discrete raised body portions (ridges or strakes) spaced along the elongate body, rather than using a continuous large-scale helical structure. This segmentation allows the device to maintain VIV reduction effectiveness while being divided into smaller, more manageable sections that are easier to handle and deploy on marine risers.
Solution Approach 2:
Instead of applying a uniform large-scale helical strake structure along the entire length, the invention uses localized raised body portions with specific geometric characteristics (height, spacing, cross-sectional shape) that are optimized for VIV suppression. These localized features modify the flow characteristics at critical points without requiring a large overall device structure.
2Reliability
If rigid fairings are used to suppress VIV, then flow separation is delayed and VIV is reduced, but the clamping process becomes time consuming
Solution Approach 1:
The flow modification device incorporates flexible or semi-flexible materials and a modular design that allows it to adapt to the cylindrical surface without requiring time-consuming rigid clamping operations. The device can be quickly secured using simpler attachment methods while maintaining its VIV suppression functionality through its dynamic ability to conform to the riser surface.
Solution Approach 2:
The device is designed to be pre-assembled or pre-configured in a compact form that facilitates rapid deployment. The raised body portions are arranged in a predetermined pattern that maintains effectiveness while allowing for quick installation without extensive on-site assembly or clamping operations.
3Reliability
If the raised body portions are continuous along the entire length, then VIV reduction is maintained, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The continuous flow modification effect is achieved through multiple discrete raised body portions rather than a single continuous structure. These segmented features are spaced at appropriate intervals along the elongate body, maintaining VIV reduction effectiveness while significantly simplifying manufacturing processes and allowing for modular production and assembly.
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
The device effectively suppresses VIV and drag on cylindrical elements by altering vortex formation, resulting in lower vibration amplitudes and drag coefficients, and is designed for easy handling and rapid deployment, enhancing operational efficiency and reducing fatigue.
Implementation Method 1
cylindrical structures such as marine risers, umbilicals, cables, and pipelines will generally be subject to vortex-induced vibration excitation when immersed in a flowing fluid medium
Implementation Method 2
Rigid fairings aim to suppress VIV by streamlining and delaying separation of the flow about the cylindrical structure
Data Source
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AI summary
A flow modification device connectable to a generally cylindrical element adapted for immersion in a fluid medium, the device comprising an elongate body having a length and a generally circular cross-section; a plurality of raised body portions disposed about and extending along the length of the elongate body, the raised body portions being arranged generally parallel to a longitudinal axis of the body and having a height between 2% and 10% of a diameter of the body; and an aperture extending through the length of the elongate body, the aperture being adapted to receive the generally cylindrical element such that the flow modification device is arranged about the cylindrical element. The plurality of raised body portions are adapted to reduce vortex- induced vibration and/or drag on the cylindrical element when the device is connected to the cylindrical element and the connected device and cylindrical element are immersed in the fluid medium and there is relative movement between the connected device and cylindrical element and the fluid medium.