title: Hydroxyl tagging velocimetry in a supersonic flow over a cavity.
abstract: Hydroxyl tagging velocimetry (HTV) measurements of velocity were made in a Mach 2 (M 2) flow with a wall cavity. In the HTV method, ArF excimer laser (193 nm) beams pass through a humid gas and dissociate H2O into H + OH to form a tagging grid of OH molecules. In this study, a 7 x 7 grid of hydroxyl (OH) molecules is tracked by planar laser-induced fluorescence. The grid motion over a fixed time delay yields about 50 velocity vectors of the two-dimensional flow in the plane of the laser sheets. Velocity precision is limited by the error in finding the crossing location of the OH lines written by the excimer tag laser. With a signal-to-noise ratio of about 10 for the OH lines, the determination of the crossing location is expected to be accurate within +/- 0.1 pixels. Velocity precision within the freestream, where the turbulence is low, is consistent with this error. Instantaneous, single-shot measurements of two-dimensional flow patterns were made in the nonreacting M 2 flow with a wall cavity under low- and high-pressure conditions. The single-shot profiles were analyzed to yield mean and rms velocity profiles in the M 2 nonreacting flow.
authors.affiliation: Department of Mechanical Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA. robert.w.pitz@vanderbilt.edu
authors.forename: Robert W
authors.initials: RW
authors.lastname: Pitz
authors.forename: Michael D
authors.initials: MD
authors.lastname: Lahr
authors.forename: Zachary W
authors.initials: ZW
authors.lastname: Douglas
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Wehrmeyer
authors.forename: Shengteng
authors.initials: S
authors.lastname: Hu
authors.forename: Campbell D
authors.initials: CD
authors.lastname: Carter
authors.forename: Kuang-Yu
authors.initials: KY
authors.lastname: Hsu
authors.forename: Chee
authors.initials: C
authors.lastname: Lum
authors.forename: Manoochehr M
authors.initials: MM
authors.lastname: Koochesfahani