U-Shaped Fairing With Parallel Fins for VIV Reduction

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Solution Overview

Problem

Existing fairings for reducing vortex-induced vibration (VIV) in offshore oil and gas production risers are complex, costly, prone to corrosion, and can cause galloping motions, while also increasing drag and requiring labor-intensive installation methods.

Innovation Solution

A U-shaped fairing with parallel fins and a bearing pad system that secures to a cylindrical element, constructed from non-metallic materials, allowing for easy installation and rotation to align with fluid currents, reducing VIV and drag without galloping, and featuring a collar system for secure attachment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional fairings are used to reduce VIV, then vortex-induced vibration is reduced, but drag increases and galloping motions occur

Engineering Contradiction:

ImproveVIV reductionVSAvoiddrag

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The fairing is divided into a leading section and a trailing section that can rotate independently relative to each other. This segmentation allows the leading section to maintain optimal orientation for VIV reduction while the trailing section can rotate to minimize drag and prevent galloping motions, resolving the contradiction between VIV reduction and drag minimization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fairing incorporates rotational freedom between the leading and trailing sections, transforming a static structure into a dynamic one. The trailing section can rotate in response to flow conditions, enabling the fairing to adapt its configuration to reduce drag and prevent galloping while the leading section maintains VIV reduction effectiveness.

Inventive Principle:

Principle #15Dynamics

2Strength

If metal fairings are used for structural strength, then strength is improved, but corrosion resistance deteriorates

Engineering Contradiction:

Improvestructural strengthVSAvoidcorrosion resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The fairing is constructed from composite materials that combine the structural strength traditionally provided by metals with the corrosion resistance of non-metallic materials. This allows the fairing to maintain adequate structural strength while being inherently resistant to corrosion in offshore environments, eliminating the need for metal components that would require corrosion protection.

Inventive Principle:

Principle #40Composite materials

3Reliability

If complex fairing designs are used for effective VIV reduction, then VIV reduction is improved, but device complexity increases

Engineering Contradiction:

ImproveVIV reduction effectivenessVSAvoidfairing structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The fairing is divided into two main sections (leading and trailing) connected by a simple rotational joint, avoiding the need for complex mechanical systems. This segmentation provides effective VIV reduction through the leading section while the simple rotational connection minimizes overall device complexity compared to more elaborate fairing designs.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fairing uses passive rotational dynamics rather than active control systems. The trailing section rotates freely in response to hydrodynamic forces, eliminating the need for motors, sensors, or control mechanisms that would increase device complexity, while still achieving effective VIV reduction and drag minimization.

Inventive Principle:

Principle #15Dynamics

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 fairing significantly reduces VIV by over 90% and minimizes drag, while preventing galloping and corrosion, with a lightweight design that simplifies installation and maintenance.

Implementation Method 1

the parallel fins being positioned so as to reduce vortex-induced vibration

Methodology Applied

Scientific EffectVortex shedding: Kármán Vortex Street

Implementation Method 2

Methodology Applied

Scientific EffectFriction reduction: Lubrication

Data Source

PatentUS7337742B1Twin fin fairing

Publication Date: 2008.03.04 SEAHORSE EQUIP

AI summary

A fairing for the reduction of vortex-induced vibration and the minimization of drag about a substantially cylindrical element immersed in a fluid medium. The fairing also eliminates the galloping phenomenon typically associated with a teardrop-shaped fairing. The fairing having a U-shaped cylindrical shell with opposing edges defining a longitudinal gap and parallel fins extending outwardly from the opposing edges of the shell, the parallel fins being positioned so as to reduce vortex-induced vibration, minimize drag and to eliminate the galloping phenomenon on the cylindrical element. Preferably, the length to diameter ratio of the fins is 1.5 to 2.50.