The ultrafast aircraft thermometer is an airborne device designed for measuring temperature in clouds with centimeter spatial resolution. Its sensor consists of 5mm long and 2.5μm thick thermo-resistive wire protected against impact of cloud droplets by a shield in the form of a suitably shaped rod, placed upstream. However the disturbances of airflow around this rod result in noise in the temperature record. Suction applied through slits located on both sides of the rod reduces the noise generated by vortices shed from the rod and lowers the probability of droplet-wire collisions. Our recent theoretical analysis and numerical simulations led to optimization of this device and additionally clarified the role of the sampling method in processing of the analogue output of the thermometer. In this paper we try to deepen our understanding of the nature of the noise as well as to improve calculations of the corrections connected with the dynamic heating. For this purpose we have done extensive three-dimensional numerical simulations of the airflow around the protective rod and the sensing wire, which permitted precise computation of dynamic heating and showed how applying the suction removes the thermal boundary layer from the rod and damps the sources of the noise.

Date Published: 13 October 2005
PDF: 10 pages
Proc. SPIE 5981, Optics in Atmospheric Propagation and Adaptive Systems VIII, 598102 (13 October 2005); doi: 10.1117/12.627038

Published in SPIE Proceedings Vol. 5981:
Optics in Atmospheric Propagation and Adaptive Systems VIII
Karin Stein; Anton Kohnle, Editor(s)