FLEET Velocimetry at 100 kHz in Hypersonic Flows

Abstract

Femtosecond Laser Electronic Excitation and Tagging (FLEET) is an unseeded molecular tagging technique that has been demonstrated for hypersonic flow velocimetry in large scale facilities, typically operating at a 1 kHz repetition rate. This work presents a demonstration of FLEETat 100 kHz, enabling continuous measurement of high-speed flows with enhanced temporal resolution. Two-dimensional velocimetry was performed using a commercially available femtosecond laser system and a subsonic nitrogen flow at atmospheric pressure. The system was then deployed in a hypersonic wind tunnel at Texas A&M University. Mach 6 freestream velocity measurements as well as measurements within a turbulent boundary layer were obtained, showcasing the feasibility of high-frequency FLEET for measuring high-speed flows.