Control of Complex Turbulent Flow

复杂湍流控制

• 批准号: RGPIN-2021-04045
• 负责人: Tarokh, Ali
• 金额: $ 1.97万
• 依托单位: Lakehead University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=742315
• 关键词: Control; Complex; Turbulent; Flow

The ability to manipulate a flow field to change it to the desired form is one of the essential topics in fluid dynamics. Although employing flow control can be seen in different engineering devices, its impact is more significant in the aerodynamics, especially at the low Reynolds number flow regime. The flow pattern may dramatically be reformed by any disturbance in low speed flow and causes a sudden increase of drag and loss of lift and thrust. Therefore, in order to achieve better aerodynamic efficiency, suitable flow control techniques are required in low Reynolds number. Unsteady aerodynamics at a low Reynolds number is a common phenomenon observed in a variety of real-world engineering applications. Typical examples are wind turbines, flying drones, micro aerial vehicles (MAV), small unmanned aerial vehicles (UAV), a flying object operating at low-density atmosphere other than Earth's small-scale lifting surfaces such as insect and bird wings. The combination of small length scale and low velocities results in low Reynolds operating conditions where the viscous effect will cause the unsteady flow separation. The fundamental nature of low Reynolds aerodynamics has enormously rich flow physics, making it an exciting research topic. In this flow regime, the passive flow control cannot improve the aerodynamic performance when the flow changes dramatically. Therefore, active flow control is required to modify the flow pattern in the complex flow conditions. Among different active flow control methods, periodic actuation of the boundary layer has shown a better performance. Smart materials such as Macro Fiber Composites actuators can produce the periodic motion required for aerodynamic performance improvement. Improving science and technology in developing smart materials makes it possible to generate different shapes on the surface (surface morphing) to control the flow pattern. In this research program, the effects of the surface morphing in the form of a traveling wave on controlling the flow separation will be studied by inspiring from aquatic swimmers. The complex flow behavior near the wall region will be investigated. Different mechanisms of exchanging momentum across the boundary layer due to the traveling wave on the surface will be explored. Also, an analytical model will be developed that predicts the optimum surface motion in various working conditions. This model can be used later in the closed-loop control system to adjust the controller. This flow control will be tested numerically on a wind turbine blade to assess its performance to improve the unsteady aerodynamic loads. This program advances our current knowledge in the role of surface morphing on the flow dynamics, which transfers to the development of innovative techniques in developing a new method for controlling the fluid flow. It has significant and broad implications for engineering new tools and technologies from designing smart wind turbines to spy insects.

操纵流场使其改变为所需形式的能力是流体动力学的基本课题之一。虽然在不同的工程装置中都可以看到流动控制的应用，但它对空气动力学的影响更为显著，特别是在低雷诺数流动状态下。在低速流动中，任何扰动都可能使流态发生显著的改变，并引起阻力的突然增加以及升力和推力的损失。因此，为了获得更好的气动效率，需要在低雷诺数下采用合适的流动控制技术。低雷诺数下的非定常空气动力学是在各种实际工程应用中观察到的常见现象。典型的例子有风力涡轮机、无人机、微型飞行器（MAV）、小型无人机（无人机）、在低密度大气中运行的飞行物体，而不是地球上的小规模升力表面，例如昆虫和鸟类的翅膀。小长度尺度和低速度的组合导致低雷诺数操作条件，其中粘性效应将引起非定常流动分离。 低雷诺数空气动力学的基本性质具有极其丰富的流动物理，使其成为一个令人兴奋的研究课题。在这种流动状态下，当流动发生剧烈变化时，被动流动控制不能改善气动性能。因此，需要主动流动控制来改变复杂流动条件下的流动模式。在不同的主动流动控制方法中，边界层的周期性驱动表现出更好的性能。智能材料，如宏纤维复合材料致动器，可以产生空气动力学性能改善所需的周期性运动。在开发智能材料方面提高科学和技术，使得在表面上产生不同的形状（表面变形）以控制流动模式成为可能。在本研究计画中，将借由水中游泳者的启发，来研究以行进波形式的表面变形对控制流动分离的影响。将研究壁面区域附近的复杂流动行为。将探讨由于表面上的行波引起的跨边界层的动量交换的不同机制。此外，将开发一个分析模型，预测各种工作条件下的最佳表面运动。该模型可以在闭环控制系统中稍后使用以调整控制器。将在风力涡轮机叶片上对这种流量控制进行数值测试，以评估其改善非定常气动载荷的性能。 该计划推进了我们目前在表面变形对流体动力学的作用方面的知识，这些知识转移到开发控制流体流动的新方法的创新技术的发展上。它对设计新工具和技术具有重大而广泛的影响，从设计智能风力涡轮机到间谍昆虫。