Bio-inspired unsteady load control to enhance power output and fatigue life of wind and tidal turbines

该项目旨在为风力和潮汐涡轮机开发一种新的叶片概念，利用多孔叶片被动地减轻非定常负荷。它建立在对被动飞行控制的多孔性和灵活性优势的自然启发研究的基础上。风力和潮汐涡轮机上的非定常流体载荷会导致疲劳和功率波动，从而增加平准化能源成本（LCOE）。先前对被动变形叶片的研究表明，它们可以完全缓解负载波动。然而，对于弹性和可靠的叶片，灵活性可能仅限于后缘，从而限制了减缓效果。为了获得额外的载荷缓解，尾缘可以是多孔的，其孔隙度与变形被动控制。当尾缘被增加的流体载荷偏转时，尾缘顶部和底部表面的交错孔可能会对齐。这种低惯性、被动控制的后缘可以对高频波动做出反应，从而将主动、低内部控制面的功效与减少被动控制的维护相结合。此外，与现有的依赖结构耦合的被动控制方法不同，尾缘可以沿着整个叶片跨度进行定制，从而减轻根部的非定常负荷，减少流动分离和能量损失，并为下游涡轮机创造更清洁的尾迹——这对大型、紧凑的农场至关重要。该项目利用了最近结束的Leverhulme Trust （RPG-2015-255）关于蒲公英果实飞行的项目，该项目展示了如何通过孔隙度控制多孔表面上的涡流结构和力，从而可以稳定流浸入体后面的尾流，从而产生新的流结构，否则这些结构太不稳定而无法存在。事实上，这就是蒲公英果实在没有动力的情况下飞行数百公里所利用的机制。我们假设鸟类也利用了类似的原理，它们的翅膀既灵活又多孔，以减轻阵风的影响。世界领先的研究小组，如加州大学洛杉矶分校的Spedding，目前正在研究航空应用中多孔机翼的空气动力学。该项目将结合孔隙率和柔性叶片影响的最新研究成果，为风力和潮汐涡轮机开发一种新的叶片概念。

This project aims to develop a new blade concept for wind and tidal turbines using porous blades to passively mitigate unsteady loads. It builds on nature-inspired research on the advantages of porosity and flexibility for passive flight control.Unsteady fluid loads on wind and tidal turbines cause fatigue and power fluctuations, increasing the levelised cost of energy (LCOE). Previous work on passive morphing blades shows that they can completely mitigate load fluctuations. However, for resilience and reliable blade, flexibility may be restricted to the trailing edge, limiting mitigation efficacy. To gain additional load mitigation, the trailing edge can be porous, with its porosity controlled passively and in tandem with its deformation. Staggered holes in the top and bottom surfaces of the trailing edge may be brought into alignment as the trailing edge is deflected by increased fluid load. This low inertia, passively controlled trailing edge could react to high frequency fluctuations thereby combining the efficacy of active, low interia control surfaces with the reduced maintenance of passive control. Additionally, unlike existing passive control methods that rely on structural couplings, the trailing edge could be tailored along the full blade span, mitigating unsteady loads down to the root to reduce flow separation and energy losses and create a cleaner wake for downstream turbines - critical for large, compacted farms.This project capitalises on the recently concluded Leverhulme Trust (RPG-2015-255) project on the flight of the dandelion fruit, which demonstrated how the vortical flow structures and the forces on a porous surface can be controlled by porosity, making it possible to stabilise the wake behind a flow immersed body to generate new flow structures that would otherwise be too unstable to exist. This is, in fact, the mechanisms exploited by the dandelion fruit to fly, unpowered for hundreds of kilometres. We hypothesise that a similar principle is also exploited by birds, whose wings are both flexible and porous, to mitigate the effect of gusts. World-leading research groups, such as Spedding at UCLA, are currently investigating the aerodynamics of porous wings for aeronautical applications. This project will combine recent findings on the effects of porosity and flexible blades to develop a new blade concept for wind and tidal turbines.