Collaborative Research: Controlling Flow Separation via Traveling Wave Actuators

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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.