title: Laser-induced fluorescence technique for velocity field measurements in subsonic gas flows.
abstract: A nonintrusive optical technique is reported for multiple-point velocity measurements in subsonic flows. The technique is based on the detection of fluorescence from a Doppler-shifted absorption line of seeded iodine molecules excited at a laser frequency fixed in the wing of the line. Counterpropagating laser sheets are used to illuminate the flow, in the present case a nitrogen round jet, thereby eliminating the need for an unshifted reference signal. The fluorescence is detected simultaneously at 10,000 points in a plane of the flow using a 100 x 100 element photodiode-array camera. The velocity at each point is computed from four successive camera frames, each recorded with a different beam direction. The measured mean velocities between 5 and 50 m/sec agree well with data from the literature.
authors.forename: B
authors.initials: B
authors.lastname: Hiller
authors.forename: J C
authors.initials: JC
authors.lastname: McDaniel
authors.forename: E C
authors.initials: EC
authors.lastname: Rea
authors.forename: R K
authors.initials: RK
authors.lastname: Hanson