Dynamics and Destabilisation of Helical Vortices

螺旋涡旋的动力学和失稳

• 批准号: 469304061
• 负责人: Dr.-Ing. Thorsten Lutz
• 金额: --
• 依托单位: Institut für Aerodynamik und Gasdynamik (IAG)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/469304061?language=en
• 关键词: Dynamics; Destabilisation; Helical; Vortices

Wind turbine wake effects can significantly reduce the global power production of wind parks. In order to achieve a quicker recovery of the wake velocity deficit, exciting the wake in order to induce earlier wake breakdown has been proposed as an attractive possibility to reduce these effects. For the efficient development of such wake control techniques, understanding instabilities and their driving parameters is necessary. The UBeRT Project aims to investigate the fundamental physics of helical wake breakdown. This shall be achieved by establishing a unique and novel experimental and numerical testbed for investigating instabilities. Response to wake excitation measures shall be explored using three turbine models: i) An experimental turbine (UBeRT), ii) a kinematically scaled numerical twin of the UBeRT (NumBeRT), that shall operate in air instead of water, and, iii) a generic full-scale 15 MW turbine numerical model (IEA 15MW). The UBeRT rotor shall be operated in the large towing tank at VWS (TU Berlin) in order to achieve higher Reynolds number than in a conventional wind tunnel. Simulations of the numerical twin NumBeRT shall serve to evaluate transferability of the experimental results in the air. Simulations of the IEA 15MW wind turbine shall provide information about possible scaling effects and address the effects of broadband inflow turbulence on wake stability. Fundamental investigation of modal and frequency content of helical wakes under excitation of long- and short-wave instabilities is required to understand the fundamental physics of helical wake breakdown. Long-wave instabilities shall be introduced numerically and experimentally via a periodic variation of the relative inflow velocity. Short-wave instabilities shall be introduced experimentally via a secondary vortex emerging from the blade tip section, which through interaction with the tip vortex shall give raise to a short-wave instability. Numerically, it shall be introduced via an added vorticity at the blade tip which shall create an elliptic instability in the vortex core. The proposed project aims further at identifying unstable modes excited through turbulent inflow and which interaction mechanisms occur between inflow turbulence and the helical vortex. Modal analysis of the wake development shall reveal the perturbation scales that lead to the quickest instability growth. Highly-resolved velocity fields of the wake development and breakdown downstream of the UBeRT rotor will be collected by means of stereo Particle Image Velocimetry. High-fidelity scale-resolving simulations of the NumBeRT rotor and the IEA15MW turbine will be performed with the flow solver FLOWer. Both data sets will be publicly available for code comparisons and validation of lower order wake models while complementing existing turbine databases, which do not explicitly focus on wake breakdown phenomena.

风力涡轮机尾流效应会显着降低风电场的全球发电量。为了实现尾流速度缺陷的更快恢复，激发尾流以引起较早的尾流崩溃已被提议作为减少这些影响的一种有吸引力的可能性。为了有效开发此类尾流控制技术，了解不稳定性及其驱动参数是必要的。 UBeRT 项目旨在研究螺旋尾流击穿的基础物理原理。这应通过建立一个独特且新颖的实验和数值测试平台来研究不稳定性来实现。应使用三种涡轮机模型来探索对尾流激励措施的响应：i）实验涡轮机（UBeRT），ii）UBeRT（NumBeRT）的运动学比例数值双胞胎，应在空气中而不是水中运行，以及，iii）a通用全尺寸 15 MW 涡轮机数值模型 (IEA 15MW)。 UBeRT 转子应在 VWS（柏林工业大学）的大型拖曳水箱中运行，以获得比传统风洞更高的雷诺数。数值孪生 NumBeRT 的模拟应用于评估实验结果在空气中的可转移性。 IEA 15MW 风力涡轮机的模拟应提供有关可能的缩放效应的信息，并解决宽带流入湍流对尾流稳定性的影响。需要对长波和短波不稳定性激励下螺旋尾流的模态和频率内容进行基础研究，以了解螺旋尾流击穿的基本物理原理。长波不稳定性应通过相对流入速度的周期性变化以数值和实验方式引入。短波不稳定性应通过从叶片尖端部分出现的次级涡流通过实验引入，该次级涡流通过与尖端涡流的相互作用将引起短波不稳定性。从数字上讲，它应通过在叶片尖端处增加涡度来引入，这将在涡核中产生椭圆不稳定性。该项目旨在进一步确定通过湍流流入激发的不稳定模式以及流入湍流和螺旋涡之间发生的相互作用机制。尾流发展的模态分析应揭示导致最快不稳定性增长的扰动尺度。 UBeRT 转子下游的尾流发展和分解的高分辨率速度场将通过立体粒子图像测速技术进行收集。 NumBeRT 转子和 IEA15MW 涡轮机的高保真尺度解析模拟将使用流量求解器 FLOWer 进行。这两个数据集将公开用于低阶尾流模型的代码比较和验证，同时补充现有的涡轮机数据库，这些数据库没有明确关注尾流故障现象。