Quantitative NO{sub 2} molecular tagging velocimetry at 500 kHz frame rate

NO{sub 2} molecular tagging velocimetry (MTV) is demonstrated at repetition rates as high as 500 kHz in a laboratory scale Mach 5 wind tunnel. A pulse burst laser and a home built optical parametric oscillator system were used to simultaneously generate the required 355 and 226 nm wavelengths for NO{sub 2} photodissociation (tagging) and NO planar laser induced fluorescence imaging (interrogation), respectively. NO{sub 2} MTV images were obtained both in front and behind the characteristic bow shock from a 5 mm diameter cylinder. From Gaussian curve fitting, an average free stream flow velocity of 719 m/s was obtained. Absolute statistical precision in velocity of {approx}11.5 m/s was determined, corresponding to relative precision of 1.6%-5%, depending upon the region of the flow probed.