Single-image attenuation corrections to facilitate instantaneous planar imaging of densely seeded particle-laden flows

Abstract

Planar Nephelometry is a laser-based technique developed to determine instantaneous local number densities of particles (or droplets) in a suspension or flow. Planar Nephelometry infers particle number density by the Mie-Lorenz scattering of laser light from the particle surface. A major advantage of Planar Nephelometry is that is does not need to resolve individual particles and therefore it is possible to have a large image viewing area. However, if the local number density of particles is sufficiently high, the laser light experiences significant attenuation which needs to be corrected to ensure accurate concentration measurements. Laser attenuation experiments were conducted using a tank with neutral density spherical particles suspended in water. Results for particles at various homogeneous concentrations were obtained. Attenuation of light by the suspended particles was determined using the scattering of light from a polymer strip at the down-beam location of the tank. The current paper presents the application of the Planar Nephelometry technique and post-processing methodology corrections required when using a single camera to obtain instantaneous planar particle concentrations.