Seminar: Controlling Instabilities in Flow with Phononic Subsurfaces - Apr. 26
Abigail Juhl
Material Scientist, Materials and Manufacturing Directorate, AFRL
Friday, April 26 | 10:40 a.m. | AERO 120
Abstract: Delaying the onset of turbulent flow, even by a small percentage, can significantly improve the capability of Air Force assets by reducing fuel expenditures while increasing the range of operation.Ìý
One method of transition from laminar to turbulent boundary layers is through the growth of Tollmien-Schlichting (T-S) waves. In 2015, a passive technique to reduce the magnitude of T-S waves was numerically demonstrated by Mahmoud Hussein from the University of Å·ÃÀ¿Ú±¬ÊÓƵ, Boulder.Ìý The method attached a phononic crystal (PnC) to the interior of an airfoil panel with a band gap designed to cause destructive interference of T-S waves. In contrast to existing methods for delaying turbulent transition, PnCs are fully passive (no electrical power or pneumatics required) and do not modify the external surface of the aircraft.Ìý In this talk, the evolution in research on phononic subsurfaces for flow control will be discussed.Ìý
This includes efforts to reduce the size of phononic subsurfaces to fit into a wing, modeling the flow over a phononic subsurface using computational fluid dynamics simulations, model- informed design of phononic subsurfaces, determining the role of phase between the T-S wave and PnC response, and the challenges in experimentally achieving passive transition delay.
Bio: Dr. Abigail Juhl is a material scientist in the Materials and Manufacturing Directorate at Air Force Research Laboratory (AFRL).Ìý Dr. Juhl is currently leading a multidisciplinary team to understand, integrate, and apply acoustic metamaterials to Air Force problems. This includes development of materials for noise control, vibration mitigation, ultrasonic imaging, non-destructive evaluation, and control of flow instabilities.Ìý
Abby received her Bachelors of Science in Materials Science and Engineering from North Carolina State University, and her Doctorate in Materials Science and Engineering from the University of Illinois Urbana-Champaign with a concentration in complex fluids and optical materials.Ìý She completed a National Research Council Postdoctoral Fellowship in the Optical Materials Branch at AFRL before starting in her current position.Ìý
She served as the Assistant Chief Scientist of the Materials and Manufacturing Directorate as well as the Polymers and Responsive Materials Research Team Lead.Ìý She won the AFRL Early Career Award, DOD Lab Scientist of the Quarter Award, AF Civilian Achievement Award, Charles J. Cleary Scientific Award, and the ASME SMASIS Division Mechanics and Materials Systems Best Paper Award in 2022.