SIMULTANEOUS MEASUREMENTS OF DROP SIZE AND VELOCITY IN LARGE-SCALE SPRINKLER FLOWS USING LASER-INDUCED FLUORESCENCE AND MIE SCATTERING

摘要

This paper reports an experimental technique that is developed for instantaneous planar measurements of drop size and velocity for dilute sprays in general and sprinkler sprays in particular. This particle tracking technique relies on photographic measurements of fluorescence and Mie scattering from water drops to determine their size and velocity. Measurements were made in a plane that passes through the vertical axis of symmetry of a specially designed axis-symmetric sprinkler. Drop sizes down to 0.2 mm, within the 250 mm x 350 mm viewing area, were measured from the digitized photographs. Drop velocities were determined from the same double-exposed photographs and the directional ambiguity was resolved by color differentiation of fluorescence vs. scattering. Dye selection and its concentration were determined by testing the fluorescence output of water tracer dyes. Collection optics and laser power was varied to optimize the color differentiation and maximize the resolution for drop size measurements.