title: Laser velocimetry with fluorescent dye-doped polystyrene microspheres.
abstract: Simultaneous Mie scattering and laser-induced fluorescence (LIF) signals are obtained from individual polystyrene latex microspheres dispersed in an air flow. Microspheres less than 1 μm mean diameter were doped with two organic fluorescent dyes, Rhodamine B (RhB) and dichlorofluorescein (DCF), intended either to provide improved particle-based flow velocimetry in the vicinity of surfaces or to provide scalar flow information (e.g., marking one of two fluid streams). Both dyes exhibit measureable fluorescence signals that are on the order of 10(-3) to 10(-4) times weaker than the simultaneously measured Mie signals. It is determined that at the conditions measured, 95.5% of RhB LIF signals and 32.2% of DCF signals provide valid laser-Doppler velocimetry measurements compared with the Mie scattering validation rate with 6.5 W of 532 nm excitation, while RhB excited with 1.0 W incident laser power still exhibits 95.4% valid velocimetry signals from the LIF channel. The results suggest that the method is applicable to wind tunnel measurements near walls where laser flare can be a limiting factor and monodisperse particles are essential.
authors.affiliation: Department of Aerospace and Ocean Engineering, Virginia Tech University, Blacksburg, Virginia 24061, USA. kelowe@vt.edu
authors.forename: K Todd
authors.initials: KT
authors.lastname: Lowe
authors.forename: Pietro
authors.initials: P
authors.lastname: Maisto
authors.forename: Gwibo
authors.initials: G
authors.lastname: Byun
authors.forename: Roger L
authors.initials: RL
authors.lastname: Simpson
authors.forename: Max
authors.initials: M
authors.lastname: Verkamp
authors.forename: Paul M
authors.initials: PM
authors.lastname: Danehy
authors.forename: Pacita I
authors.initials: PI
authors.lastname: Tiemsin
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Wohl