The Department of Mechanical, Materials, and Aerospace Engineering presents its spring 2025 seminar series featuring Sean Kearney, Professor of Aerospace Engineering at the University of Illinois Urbana-Champaign. Kearney will present “CARS Diagnostics for Aerospace Sciences.” This seminar is open to the public and will take place on Wednesday, February 5, 2025, from 12:45–1:45 p.m. in room 104 of the Rettaliata Engineering Center.

Abstract

Coherent anti-Stokes Raman scattering (CARS) has a four-decade history of application in challenging reacting and high-speed flow environments for thermometry, multi-species detection, and pressure measurements. Since the mid-2000s, the method has evolved with advancements in laser sources, including ultrashort-pulse femtosecond lasers and high-speed pulse-burst systems. In this talk, we discuss three recent examples of CARS application to aerospace sciences, each with a different laser architecture. A generalized description of the working principles of the CARS technique and it’s sensitivity to temperature and gas composition is provided. Recent Nd:YAG/dye-laser based temperature/species measurements in ablation and nonequilibrium boundary layers in the University of Illinois Plasmatron X facility are presented. These measurements illustrate the CARS method’s performance at extreme temperatures as high as 5500 K, with an ability to determine species-specific nonequilibrium vibrational and rotational temperatures. Ultrashort-pulse one-dimensional CARS line imaging for compressible flows is introduced, and application for simultaneous temperature, pressure, and molecular-tagging velocimetry is demonstrated in an underexpanded air jet. The talk concludes with a summary of high-speed, 100-kHz CARS and molecular-tagging velocimetry with the pulse-burst laser for characterization of the Sandia free-piston shock tunnel.

Biography

Sean Kearney is a Professor of Aerospace Engineering at the University of Illinois Urbana-Champaign, and currently holds a joint appointment with Sandia National Laboratories, where he has been a Technical Staff Member for 24 years. He has applied laser-based diagnostics to a wide variety of national-security problems in combustion, fluid mechanics, and heat transfer, and has helped pioneer the use of ultrashort-pulse and burst-mode laser sources for reacting flow diagnostics. His most recent research foci have been development of pulse-burst laser diagnostics for impulsively driven experiments and CARS applications at the interface between dissociated air and ablating heat-shield materials for hypersonic flight. He holds MS and Ph.D. degrees in Mechanical Engineering from the University of Illinois Urbana-Champaign and a Bachelor of Science degree in Mechanical Engineering from Clarkson University. Dr. Kearney is an Associate Fellow of AIAA, where he recently served as Chair of AIAA’s Aerodynamic Measurement Technology technical committee.