Total Temperature Measurements using a Rearward Facing Probe in Supercooled Liquid Droplet and Ice Crystal Clouds

This paper presents an analysis of local total temperature and humidity experimental measurement taken in atmospheric ice cloud flows. The measurements were obtained in a series of tests in NASA's Propulsion Systems Laboratory. The probe used in the tests is referred to as the Rearward Facing Probe which was designed to mitigate the contamination effects of ice accretion and ingestion into the probe. The data provided important insights in the interaction of the ice cloud and the atmospheric flow. For the majority of the test runs, small temperature drops in the range of 0.6 to 2.8 C and up to 1.5 g/kg of water vapor rise were found as a result of the interaction. Under certain very low temperature or high TWC conditions, the interaction with the cloud produced a warming of the airflow. A thermal model based on evaporative and convective heat transfer mechanisms between the spray droplets and the airflow showed good agreement with the experimental data. Detailed analyses of the response of the probe under various flow, thermodynamic, and cloud conditions, are provided in the paper.