Rw. Pitz et al., Unseeded molecular flow tagging in cold and hot flows using ozone and hydroxyl tagging velocimetry, MEAS SCI T, 11(9), 2000, pp. 1259-1271
Two complementary unseeded molecular Row tagging techniques for gas-flow ve
locity held measurement at low and high temperature are demonstrated. Ozone
tagging velocimetry (OTV) is applicable to low-temperature air Rows wherea
s hydroxyl tagging velocimetry (HTV) is amenable to use in high-temperature
reacting Rows containing water vapour. Tn OTV, a grid of ozone lines is cr
eated by photodissociation of O-2 by a narrowband 193 nm ArF excimer laser.
After a fixed time delay, the ozone grid is imaged with a narrowband KrF l
aser sheet that photodissociates the ozone and produces vibrationally excit
ed O-2 that is: subsequently made to fluoresce by the same KrF laser light
sheet via the O-2 transition B (3)Sigma(u)(-) (v' = 0, 2) <-- X (3)Sigma(g)
(-) (v = 6, 7). in HTV, a molecular grid of hydroxyl (OH) radicals is writt
en into a flame by single-photon photodissociation of vibrationally excited
H2O by a 193 nm ArF excimer laser. After displacement, the OH tag line pos
ition is revealed through fluorescence caused by OH A (2)Sigma(1) - X-2 Pi
(3 <-- 0) excitation using a 248 nm tunable KrF excimer laser. OTV and HTV
use the same lasers and can simultaneously measure velocities in low and hi
gh temperature regions. Instantaneous flow-tagging grids are measured in ai
r flows and a flame. The velocity field is extracted from OTV images in an
air jet using the image correlation velocimetry (ICV) method.