Collaborative Research: Controlling Flow Separation via Traveling Wave Actuators

机翼或风扇叶片上的气流分离通常会导致升力、推力或功率的显著损失，阻力增加，燃油消耗增加等。因此，应该通过设计或控制来防止这些表面上的流动分离。在这个项目中，为了控制流动分离，地面附近的流动通过一种新的轻质、节能的执行器来触发不稳定，产生行波。该项目的主要目标是测试这种驱动比其他方式更有效的假设，并通过了解控制执行器与流量相互作用的关键参数来优化执行器的性能。这个项目将制作一系列教育视频，并通过我们各机构的成熟项目吸引不同群体的本科生参与。该提议的主要假设是行波致动器比其他产生驻波的致动器性能更好，因为：1)行波也注入动量（产生推力），2)除了频率之外，初步结果表明，另外一个参数（波长）也可以调节来影响流动分离。数值和实验方法将用于流动的一个典型的翼型（NACA0018）。具有运动边界的大涡模拟将为行波作动器的初始设计提供可能的行波，并阐明流动再附着的机理。风洞实验将通过行波致动器与驻波致动器的比较，为验证模拟和验证假设提供数据。团队吗?我们在通过压电致动器和风洞实验产生行波以及具有移动边界和流固耦合的LES方面的协同能力使我们能够独特地应对这一挑战并完成本提案提出的任务。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Flow separation over a wing or fan blade leads typically to a significant loss of lift, thrust, or power, an increase in drag, an increase in fuel consumption, etc. Consequently, flow separation over these surfaces should be prevented with design or controlled. To control flow separation in this project, the flow near the surface is energized through triggering instabilities by a new lightweight, energy-efficient actuator that generates traveling waves. The main goal of this project is to test the hypothesis that this actuation is more efficient than other means and to optimize the performance of this actuator by gaining an understanding of the key parameters that govern the interaction of the actuator with the flow. This project will create a series of educational videos and the engagement of a diverse group of undergraduate students through well-established programs at our institutions. The main hypothesis of this proposal is that traveling wave actuators perform better than other actuators that create standing waves because: 1) traveling waves also inject momentum (generate thrust), and 2) apart from frequency, an additional parameter (wavelength) can also be tuned to affect flow separation as demonstrated by the preliminary results. Numerical and experimental approaches will be used for flow on a typical airfoil (NACA0018). Large-eddy simulations (LES) with moving boundaries will provide possible traveling waves for the initial design of traveling wave actuators and elucidate the mechanisms of flow reattachment. The experiments in the wind tunnel will provide the data to validate the simulations and confirm the hypothesis by comparing the traveling against standing wave actuators. The team?s synergistic capabilities in generating traveling wave via piezoelectric actuators and the wind tunnel experiments as well as LES with moving boundaries and fluid-structure interaction uniquely position us to tackle this challenge and accomplish the tasks put forward in this proposal.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.