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著降低风电场的全球发电量。为了实现更快地恢复尾流速度不足，激励尾流以诱导更早的尾流击穿已被提出作为减少这些影响的有吸引力的可能性。为了有效地开发这种尾流控制技术，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本物理。这将通过建立一个独特的和新颖的实验和数值试验平台来实现，以调查不稳定性。应使用三种涡轮机模型探索尾流激励措施的响应：i）实验涡轮机（UBeRT），ii）UBeRT的运动学比例数值孪生模型（NumBeRT），其应在空气中而不是水中运行，以及iii）通用全尺寸15 MW涡轮机数值模型（IEA 15 MW）。UBeRT转子应在VWS（柏林工业大学）的大型拖曳水池中运行，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传递性。IEA 15 MW风力涡轮机的模拟应提供有关可能的缩放效应的信息，并说明宽带流入湍流对尾流稳定性的影响。为了了解螺旋尾迹破裂的基本物理过程，需要对长、短波不稳定性激励下螺旋尾迹的模态和频率成分进行基本研究。长波不稳定性应通过相对流入速度的周期性变化进行数值和实验。短波不稳定性应通过实验通过叶尖部分出现的二次涡流引入，二次涡流通过与叶尖涡流的相互作用应引起短波不稳定性。从数值上讲，它应通过叶尖处的附加涡量引入，这将在涡核中产生椭圆不稳定性。拟议项目的进一步目标是识别通过湍流流入激发的不稳定模式以及流入湍流和螺旋涡流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增长的扰动尺度。将通过立体粒子图像测速仪收集UBeRT转子下游尾迹发展和故障的高分辨率速度场。NumBeRT转子和IEA 15 MW涡轮机的高保真度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代码比较和低阶尾流模型的验证，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击穿现象。