Séminaire exceptionnel IUSTI – 13 juil. 2018 – 11h salle 250
Femtosecond Laser Electronic Excitation Tagging (FLEET) for Free Stream and Boundary Layer Measurements in Subsonic, Supersonic and Hypersonic Air and Nitrogen
Richard Miles – Texas A&M Univ., ÉU
Femtosecond Laser Electronic Excitation Tagging (FLEET) is a new non-intrusive optical diagnostic method which provides direct measurement of velocity and other transport properties in unseeded air and nitrogen flows. Only a single laser and a single time gated camera are required. A one kilo Hertz pulse repetition rate laser with ~1 millijoule, 100 femtosecond pulses is used to create long lived fluorescent tracer lines and patterns of nitrogen molecules that are imaged with a time-gated intensified camera. Quantitative velocity and turbulent structure measurements are obtained by imaging the displacement of the tagged lines and patterns. The potential to create these patterns at kilohertz rates and follow their real time motion as they evolve at imaging rates up to mega Hertz brings a new capability for high speed fluid dynamic measurements. Examples of boundary layer and free stream measurements will be provided for subsonic, supersonic, and hypersonics flows including recent free stream and boundary layer measurements in the 2 meter diameter AEDC Tunnel 9 at up to Mach 14.