This deliverable provides the results from the measurements and calibration activities performed in the RTA Icing Wind Tunnel (IWT) for Freezing Rain (FZRA) cloud conditions and a summary of the measurements at CIRA-IWT, showing a potential capability for FZRA cloud generation.
A full assessment of the FZRA capabilities for RTA-IWT has been presented in this report. The guidelines on the procedures to be followed for the cloud characterizations have been defined in deliverable D6.1-2, “Proposal of Calibration Instruments and Procedures for FZDZ and FZRA”. Three separate test campaigns, starting in August 2019 and ending in June 2021, were conducted at RTA, whose SLD capabilities were already available at the start of the project, limited to PSD/MVD calibration for the FZDZ. During the project period, a better assessment of the LWC and a review of the PSD/MVD envelope for both FZDZ and FZRA were performed using selected instrumentation from Deliverable D6.1-2 to achieve a better accuracy of the LWC characterization. In addition, a refinement of the PSD/MVD, cloud uniformity, and droplet temperature measurements were performed and are presented in this report outlining the RTA-IWT calibration for freezing rain with an MVD greater than 40 μm.
After the upgrade with a new spray nozzle, followed by the commissioning of the spray bar system in January-February 2022, the measurements in the CIRA-IWT were planned to a single slot from April 2022 to early June 2022. The calibration began with the cloud uniformity check and extended to LWC and PSD/MVD measurements for one of the three spray bar configurations. The time available was only allowed to characterize cloud conditions at the sea level for FZDZ higher and lower than 40 μm, with few conditions for checking different pressure altitudes and spray bar configurations. FZRA conditions were not addressed during the available measurement slot, where the instrument configuration was focused only on FZDZ clouds, although some cloud conditions showed potential FZRA features in their spectra.
