CAREER: Control of Vortex Breakdown in High-Reynolds Number Rotor Flows with Secondary Vortex Structures

该项目旨在研究和减少叶片尖端涡流对基于转子的系统的负面影响，如风力涡轮机、用于能源生产或飞机推进的燃气轮机，以及旋翼飞行器。目前，由于不能控制或扩散叶片尖端涡流的高能含量，这些系统的性能不佳。该项目的一个主要方面是在佛罗里达国际大学一个独特的大风飓风模拟器设施中进行大规模实验，该设施能够使流动相似并将结果实际应用于全尺寸旋翼系统。这样的教育培训对于增加实验热流体工程师的人才库至关重要，这些工程师可以继续提高能源系统的效率，造福社会。拟议的大规模实验将检验新理论，并利用合成射流和弦向壁面振荡产生的二次涡结构来创造高雷诺数叶片尖涡破裂的新知识。其理论意义是一个半经验模型，它描述了发生涡旋破裂所必需的二次涡(如长度/时间尺度、涡度)的特征，以及它对湍流动能的影响，这被认为是诱导叶片结构振动的原因。流动将使用立体粒子图像测速技术进行测量，并使用适当的正交分解(POD)以及从一组二维测量平面进行三维流动重建进行分析。这些方法对于大区域高雷诺数流动是独一无二的。它们将被用于揭示叶片尖端涡能含量/POD模式，以及推进实验涡动力学领域，特别是在高雷诺数情况下。

This project seeks to study and reduce the negative impact of blade tip vortices on rotor-based systems such as wind turbines, gas turbines for energy production or aircraft propulsion, and rotorcraft. Currently these systems suffer from underperformance due to an inability to control or diffuse the high-energy content of the blade tip vortex. A major aspect of the project is the large-scale experiments in a unique high-wind hurricane simulator facility at Florida International University that enables flow-similitude and realistic application of the results to full-scale rotor-based systems. Such educational training is vital to increase the pool of experimental thermal-fluids engineers that can continue to improve the efficiency of energy systems for the benefit of society. The proposed large-scale experiments will test new theories and create new knowledge of high- Reynolds number blade tip vortex breakdown using secondary vortex structures created by synthetic jets and chord-wise wall oscillations. The intellectual significance is a semi-empirical model that describes the characteristics of secondary vortices (e.g. length/ time scales, vorticity) necessary for vortex breakdown to occur, as well as its impact on turbulent kinetic energy, which is believed to induce blade structural vibration. The flow will be measured using stereoscopic particle image velocimetry techniques and analyzed using proper orthogonal decomposition (POD) as well as three-dimensional flow reconstruction from an array of two-dimensional measurement planes. These methods are unique for large-domain high Reynolds number flows. They will be used to shed light on blade tip vortex energy content/ POD modes, as well as to advance the field of experimental vortex dynamics particularly at high Reynolds numbers.