Wind Turbine Blade Vortex Shedding Control via Asymmetric Flaps
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Solution Overview
Problem
Wind turbine rotor blades experience edgewise vibrations due to vortex shedding when not rotating, which can lead to structural failure or reduced lifetime, especially when the frequency of vortex shedding matches the blade's eigen frequencies.
Innovation Solution
The implementation of movable devices along the span of the rotor blade, such as trailing edge flaps or Gurney flaps, which are configured to have different standstill positions when the turbine is not rotating, altering the aerodynamic surface and varying the frequency of vortex shedding to reduce the risk of synchronous shedding and associated vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If movable devices are configured with different standstill positions along the blade span, then vortex shedding frequency synchronization is reduced and edgewise vibrations are minimized, but device complexity and control requirements increase
Solution Approach 1:
The patent applies local quality by configuring movable devices (such as flaps or tabs) at different standstill positions along the span of the rotor blade. Each movable device is positioned differently relative to the blade body when the blade is stationary, creating local variations in the aerodynamic surface that disrupt synchronous vortex shedding across the blade span. This localized differentiation prevents uniform vortex formation and reduces resonant vibrations.
Solution Approach 2:
The patent employs asymmetry by intentionally creating asymmetric configurations of movable devices along the blade span. The standstill positions are deliberately set to be non-uniform and asymmetric relative to the blade body, which breaks the symmetry that would otherwise allow synchronous vortex shedding to occur across the entire blade. This asymmetric arrangement ensures that vortices shed at different frequencies and phases along the span.
2Reliability
If movable devices alter the aerodynamic surface to vary vortex shedding frequency, then edgewise vibrations are reduced, but manufacturing and positioning precision requirements increase
Solution Approach 1:
The patent applies parameter changes by varying the standstill position parameter of movable devices along the blade span. Instead of using identical positions, the configuration specifies different positional parameters (distances, angles, or deflection values) for each movable device. This parameter variation changes the local aerodynamic characteristics and vortex shedding frequencies, preventing synchronization across the blade while managing manufacturing tolerances through deliberate design specifications.
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 configuration reduces the likelihood of vortex shedding frequencies matching the blade's eigen frequencies, thereby minimizing edgewise vibrations and extending the blade's lifespan by distributing the shedding frequency along the blade span.
Implementation Method 1
When such a bluff body is subjected to the oncoming wind flow, the flow may separate from the blade giving rise to periodic vortex shedding form either side of the blade
Implementation Method 2
the flow may separate from the blade giving rise to periodic vortex shedding
Data Source
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Figure 3
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AI summary
A method of reducing fluid flow induced forces produced by vortex shedding upon a wind turbine rotor blade having a blade body, the method comprising: providing a plurality of movable devices connected to the blade body and spaced along the span of the rotor blade for modifying the aerodynamic surface or shape of the rotor blade; configuring at least two of the plurality of movable devices such that their position relative to the blade body when the rotor blade is not rotating, is at a standstill position; wherein the standstill positions of the at least two of the plurality of movable devices relative to the blade body are different.