Influence of Freestream Temperature on Ice Accretion Roughness 2019-01-1993
The influence of freestream static temperature on roughness temporal evolution and spatial variation was investigated in the Icing Research Tunnel (IRT) at NASA Glenn Research Center. A 53.34 cm (21-in.) NACA 0012 airfoil model and a 152.4 cm (60-in.) HAARP-II business jet airfoil model were exposed to Appendix C clouds for fixed exposure times and the resulting ice accumulation parameter. For the base conditions, the static temperature was varied to produce different stagnation point freezing fractions. The resulting ice shapes were then scanned using a ROMER Absolute Arm system and analyzed using the self-organizing map approach of McClain and Kreeger. The ice accretion prediction program LEWICE was further used to interrogate the ice accretion point clouds using the predicted surface variations of local collection efficiency. The resulting equivalent sand-grain roughness heights predicted using the correlation of Flack and Schultz are compared to the roughness correlation employed in LEWICE for roughness convection enhancement predictions. The results demonstrate the influence of the stagnation point freezing fraction on the maximum sand-grain roughness height. A new function is developed to predict the maximum sand-grain roughness height based on the stagnation point freezing fraction and accumulation time.
Stephen T. McClain, Mario Vargas, Jen-Ching Tsao, Andy Broeren
Baylor University, NASA Glenn Research Center, Ohio Aerospace Institute
International Conference on Icing of Aircraft, Engines, and Structures