Simultaneous high-speed planar imaging of mixture fraction and velocity using a burst-mode laser
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Simultaneous high-speed quantitative imaging of mixture fraction and velocity is demonstrated using the fourth- and second-harmonic outputs, respectively, of a burst-mode Nd:YAG laser. A tenfold increase in the record length and 16-fold increase in per-pulse energy are achieved compared with previous measurements of mixture fraction using burst-mode and continuously pulsed diode-pumped solid-state lasers, respectively. The high output energy is used for quantitative, high-speed mixture-fraction imaging with acetone planar laser-induced fluorescence, which also enables simultaneous particle-based velocimetry without interference from particle scattering. A semiquantitative model is used to determine the limitations on fourth-harmonic output energy due to the effects of transient absorption and thermal phase mismatch over a range of repetition rates. Data are presented for mixing within a turbulent jet (Reynolds number of 15,000) and are validated by comparisons with known turbulent mixing laws and previously published data.
KeywordsMixture Fraction Transient Absorption High Repetition Rate Phase Mismatch DPSS Laser
Funding was provided, in part, by the Air Force Office of Scientific Research (Dr. Chiping Li, Program Manager) and the Air Force Research Laboratory under contract No. FA8650-12-C-2200. The authors also thank D. Diaz, M. Johnson, and A. Barrow of Iowa State University. J. Miller is currently a National Research Council Research Associate at the Air Force Research Laboratory, Aerospace Systems Directorate. This manuscript has been approved for public release (88ABW-2013-1521).