Aerodynamic Simulation of Runback Ice Accretion

Abstract

This paper presents the results of recent investigations into the aerodynamics of simulated runback ice accretion on airfoils. Aerodynamic testing was performed on a full-scale, 72-in.-chord (1828.8-mm-chord), NACA 23012 airfoil model over a Reynolds number range of 4:7 10 6 to 16:0 10 6 and a Mach number range of 0.10 to 0.28. A highfidelity ice-casting simulation of a runback ice accretion was attached to the model leading edge. For Re 16:0 10 6 and M 0:20, the artificial ice shape decreased the maximum lift coefficient from 1.82 to 1.51 and decreased the stalling angle of attack from 18.1 to 15.0 deg. In general, the iced-airfoil performance was insensitive to Reynolds and Mach number changes over the range tested. Aerodynamic testing was also conducted on a quarter-scale NACA 23012 model [18 in. (457.2 mm) chord] at Re 1:8 10 6 and M 0:18, using low-fidelity geometrically scaled simulations of the full-scale casting. It was found that simple two-dimensional simulations of the upper-and lowersurface runback ridges provided the best representation of the full-scale, high-Reynolds-number, iced-airfoil aerodynamics. Higher-fidelity simulations of the runback ice accretion that included geometrically scaled threedimensional features resulted in larger performance degradations than those measured on the full-scale model. Based upon this research, a new subclassification of spanwise-ridge ice is proposed that distinguishes between short and tall ridges. This distinction is made in terms of the fundamental aerodynamic characteristics as described in this paper.

Validation of 3-D Ice Accretion Measurement Methodology for Experimental Aerodynamic Simulation

“…The resulting implication for aerodynamic simulation is that the artificial ice shapes must replicate much of the fine details of the runback ice accretion geometry. 31 Therefore, the good agreement in aerodynamic performance between the casting and RPM simulations shown in Fig. 17 implies that there was also good agreement in the geometry of these two simulations.…”

“…The stalling angle for the airfoil with the casting simulation was increased by approximately two degrees to 16.4 deg. This type of aerodynamic behavior with short spanwise ridge ice was documented in detail by Whalen et al [25][26][27][28] and Broeren et al [29][30][31] The spanwise-ridge geometry in this case acts to delay stall relative to the clean airfoil at this Reynolds number. However, at increased Reynolds number, the clean airfoil maximum lift coefficient and stall angle would both increase, while the iced-airfoil performance would be expected to remain approximately the same.…”

“…However, at increased Reynolds number, the clean airfoil maximum lift coefficient and stall angle would both increase, while the iced-airfoil performance would be expected to remain approximately the same. 31 For example, at Re = 16.0 × 10 6 and M = 0.20, the clean NACA 23012 has C l,max = 1.82 and α stall = 18.1 deg. 5,31 At this Reynolds number, the spanwise-ridge ice accretion would have a significant effect on the airfoil performance (as would the other ice accretion cases previously described).…”

“…31 For example, at Re = 16.0 × 10 6 and M = 0.20, the clean NACA 23012 has C l,max = 1.82 and α stall = 18.1 deg. 5,31 At this Reynolds number, the spanwise-ridge ice accretion would have a significant effect on the airfoil performance (as would the other ice accretion cases previously described).…”

Supercooled large droplet icing accretion and its unsteady aerodynamic characteristics on high-lift devices

“…At the same time, iced airfoil with smaller chord length usually leads to larger geometry variation, resulting in larger performance degradation. 14,15 This indicates high-lift devices are easier to emerge dangerous damages upon SLD conditions. Since different airfoils (NACA23012m and NLF0414) with the same ice shape 16 reflect totally different degradations of maximum lift coefficient and stall angle, the integration between ice accretion and aerodynamic effects cannot be neglected.…”