Laser attenuation correction for planar nephelometry concentration measurements

Abstract

Planar imaging of optically dense media using laser diagnostics is subject to measurement errors due to the occurrence of laser attenuation. Laser attenuation effects are particularly significant in Planar Nephelometry, a technique which infers particle concentration from the intensity of light scattered from particles. The current study presents an iterative correction method for Planar Nephelometry concentration measurements to account for errors due to laser attenuation. This method minimizes the influence of laser attenuation by applying the corrections directly on instantaneous planar images of the medium investigated. As instantaneous images are used, the method is suitable for measurements of highly turbulent flows that require instantaneous planar information. The proposed correction method is validated experimentally using Planar Nephelometry concentration measurements. Experiments conducted used neutrally buoyant spherical particles suspended in water at various known concentrations. Results indicate that corrections can be used to improve the accuracy of concentration measurements from 65% to approximately 90%.