Mixed-Phase Ice Crystal and Droplet Characterization and Thermometry

This effort proposes to design, build, and demonstrate a new instrument for icing research and flight safety capable of discriminating liquid water from ice while simultaneously measuring the diameter, velocity, and temperature of droplets or the velocity and size for ice crystals. From these individual particle characteristics the total liquid water content (LWC) and the total water content (TWC) of the flow may be found. This non-intrusive, laser-based, point measurement diagnostic will operate in an off-axis, backscatter configuration at a range of working distances appropriate to characterize laboratory-scale experiments, icing tunnel flows, free jet test facilities, or flight conditions at altitude. The proposed instrument will apply phase-Doppler interferometry, polarization ratio phase discrimination, droplet rainbow thermometry, and cross-polarization imaging to each particle measured. This will provide joint measures of liquid/solid phase, velocity, diameter or particle size, and droplet temperature. Furthermore, there is redundancy built into the measurements. For instance, the droplet diameter can be measured both by phase-Doppler interferometry and by rainbow thermometry and all four measurement techniques can discriminate solid ice from liquid droplets. While no single instrument can measure all possible cloud droplets, the proposed instrument can be configured to measure droplets from as small as 3 um to larger than 3 mm in diameter.