Particle Image Velocimetry in a Nonreacting and Reacting High-Speed Cavity

Cavity-based flameholding for chemically-reacting supersonic flows

“…OH-PLIF images obtained by Allen [1] in a cavity with rear wall fueling revealed fluctuations in the location and size of the reaction zone as fuel flow rates were reduced towards lean blowout. Several researchers [49,65,84,92,19] have reported marked unsteadiness in shear layer-stabilized flames even at conditions away from blowout for both upstream and direct fuel injection. High-speed (50 kHz) video records of flame luminosity obtained by Donohue [19] revealed random side-to-side fluctuations and propagation of the flame upstream of the cavity leading edge along the isolator floor and sidewalls at steady-state fueling conditions.…”

“…Increased flame unsteadiness has been observed near lean [1,31,34,47] and rich blowout [84]. Table 5 includes a list of a select number of studies in which unsteady flame behavior was documented and/or analyzed.…”

“…Pan et al [65] reported continuous movement of the combustor shock train during cavity combustion, indicating unsteady flame behavior. Tuttle et al [84] detected intermittent streamwise oscillations of shear layer-stabilized flames through examination of the statistical variance of the shear layer vorticity distribution obtained from TiO 2 -PIV. The degree of unsteadiness increased as rich blowout was approached.…”

“…This was attributed to a reduction in shear layer velocity gradients, hence turbulent stresses, resulting in attenuated shear layer entrainment and a diminished exchange rate between the recirculation zone and freestream. Tuttle et al [84] studied changes in the kinematic properties of a supersonic cavity flow due to combustion heat release. Velocity and vorticity distributions obtained via titanium dioxide particle image velocimetry TiO 2 -PIV revealed shear layer thickening and a corresponding decrease in shear layer velocity gradients with cavity combustion, a validation of Winterfeld's explanation for the increase in mean recirculation zone residence time in the reacting case.…”

Velocimetry Using Graphite Tracer Particles in a Scramjet Flowpath (Invited)

“…5 Optical diagnostics applied to scramjet flows have included planar laser-induced fluorescence (PLIF), 6 coherent antiStokes Raman spectroscopy (CARS), 7 tunable diode laser absorption spectroscopy (TDLAS), 8 tunable diode laser absorption tomography (TDLAT), 9 laser Doppler velocimetry (LDV), 10 hydroxyl-tagging velocimetry (HTV), 11 and particle image velocimetry (PIV). 1,[12][13][14][15][16] Of the velocimetry techniques, both PIV and LDV are dependent on proper seeding of the flowfield with tracer particles. 17 These particles must be sufficiently large to scatter enough light to enable photographic detection, yet small enough to faithfully track the flow.…”