Seminar: Stability and Transition on Flight Vehicles

The ability to accurately predict and control the transition process from laminar to turbulent flow will provide significant advances in air-vehicle design, with applications ranging from high-altitude long-endurance unmanned aerial vehicles, to energy-efficient transports, to hypersonic systems. The development, validation, and introduction of physics-based approaches for stability and transition prediction will lead to smaller and more manageable uncertainties in the design of vehicles. Moreover, control may be applied for two different reasons. First there is the desire to delay transition, which contributes to aerodynamic heating load reduction and range and/or endurance. A second desire is to encourage transition for enhanced mixing or separation delay, such as over control surfaces and the inlet of a scramjet engine. The most effective strategy for control is to capitalize on the flow physics, identify the relevant instability mechanisms and what affects them, and modulate the most unstable disturbances as they are just beginning to grow. Our team has successfully applied linear and nonlinear parabolized stability equation and global methods to these problems, and also considered the effects of 2-D surface excrescences and formulated a physics-based correlation for forward-facing steps in 3-D boundary layers. Through mechanism identification, verification, and validation activities, several lessons have been learned in applying stability formulations.

About the Speaker

Helen L. Reed, Ph.D., P.E. holds the titles of Regents Professor, Presidential Professor for Teaching Excellence, and Holder of the Edward "Pete" Aldridge '60 Professorship within the Department of Aerospace Engineering at Texas A&M University. She joined Texas A&M in 2004, served as Department Head (2004-08), and founded and directs both the AggieSat Lab Small Satellite Program and the Computational Stability and Transition Laboratory. She is also Co-Founder, member of the Board of Directors, and Chief Technology Officer for Chandah Space Technologies, a start-up company specializing in small-satellite systems. She has 40 years of experience in boundary-layer receptivity, stability, transition, and flow control for both 2-D and 3-D flowfields over the whole speed range from low subsonic to hypersonic, and 24 years of experience in micro- and nano- satellite design and operations and student programs. She received her PhD in Engineering Mechanics from Virginia Tech and has held prior appointments at NASA Langley Research Center, Stanford University, Sandia National Laboratories, Arizona State University, and Tohoku University in Sendai Japan. She is a Fellow of the American Institute of Aeronautics & Astronautics (AIAA), American Physical Society, and American Society of Mechanical Engineers (ASME). She received the 2016 Kate Gleason Award from ASME, and the 2007 J. Leland "Lee" Atwood Award from the American Society for Engineering Education and AIAA. She was also inducted into the College of Engineering Academy of Engineering Excellence and “Committee of 100”, and the inaugural class of the Academy of Aerospace and Ocean Engineering at Virginia Tech. Presently she is the Chair of the AIAA Transition Discussion Group, a member of the NATO AVT ET 136 Technical Team: “Hypersonic Boundary Layer Transition Prediction”, and a member of the National Academies’ Intelligence Science and Technology Experts Group.

Hosted by Professor Datta Gaitonde