Interferometric laser imaging for droplet sizing method for long range measurements

Abstract

A recent appendix in the aircraft regulations comprises testing supercooled large droplets impinging on its surfaces. For those tests, the size and distributions of droplets need to be characterized in icing wind tunnels. In this paper, the applicability of implementation of the “Interferometric Laser Imaging for Droplet Sizing” technique inside a wind tunnel with a 3 m × 2 m open elliptical test section has been discussed. Experiments have been conducted in the laboratory for the discussion at object distance of 1.6 m and 2.29 m and droplets diameters between 360 µm and 850 µm. All the streams were previously characterized by means of the shadowgraph imaging technique. A novel approach of the Interferometric Laser Imaging for Droplet Sizing technique where droplets are not fully defocused to avoid excessive overlapping is presented. Two new image processing approaches provide in general good results as compared to previous methods.