Experimental Study of Full-Scale Iced Airfoil Aerodynamic Performance Using Sub-Scale Simulations

Abstract

Determining the aerodynamic effects of ice accretion on aircraft surfaces is an important step in aircraft design and certification. The goal of this work was to develop a complete sub-scale wind tunnel simulation methodology based on knowledge of the detailed iced-airfoil flowfield that allows the accurate measurement of aerodynamic penalties associated with the accretion of ice on an airfoil and to validate this methodology using full-scale iced-airfoil performance data obtained at near-flight Reynolds numbers. In earlier work, several classifications of ice shape were developed based on key aerodynamic features in the iced-airfoil flowfield: ice roughness, streamwise ice, horn ice, and tall and short spanwise-ridge ice. Castings of each of these classifications were acquired on a full-scale NACA 23012 airfoil model and the aerodynamic performance of each was measured at a Reynolds number of 12.0 x 10 6 and a Mach number = 0.20. In the current study, sub-scale simple-geometry and 2-D smooth simulations of each of these castings were constructed based on knowledge of iced-airfoil flowfields. The effects of each simulation on the aerodynamic performance of an 18-inch chord NACA 23012 airfoil model was measured in the University of Illinois 3 x 4 ft. wind tunnel at a Reynolds number of 1.8 x 10 6 and a Mach number of 0.18 and compared with that measured for the corresponding full-scale casting at high Reynolds number. Geometrically-scaled simulations of the horn-ice and tall spanwise-ridge ice castings modeled C l,max to within 2% and C d,min to within 15%. Good qualitative agreement in the C p distributions suggests that important geometric features such as horn and ridge height, surface location, and angle with respect to the airfoil chordline were appropriately modeled. Geometrically-scaled simulations of the ice roughness, streamwise ice, and short-ridge ice tended to have conservative C l,max and C d . The aerodynamic performance of simulations of these types of accretion was found to be sensitive to roughness height and concentration. Scaled roughness heights smaller than those ii found on the casting were necessary to improve simulation accuracy, resulting in C l,max and C d,min within 3% and 5% of the casting, respectively.iii

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

“…The aerodynamic simulation of streamwise ice was investigated in detail by Broeren et al 5 and Busch et al 14,20,23 This type of aerodynamic matching requires accurate reproduction of certain characteristics of the roughness and feather features of the ice accretion. The reproduction of the gross ice shape is actually less American Institute of Aeronautics and Astronautics important for streamwise ice where the main ice accretion tends to be an extension of the airfoil leading edge.…”

Effect of Ice Shape Fidelity on Swept Wing Aerodynamic Performance

“…Low-Reynolds number testing (Re = 1.8 × 10 6 ) on a subscale NACA 23012 airfoil model was then used to evaluate the effect of ice accretion fidelity on measured aerodynamic performance. 7,8,9 While the cast shapes tested in the F1 tunnel provided the relatively complete three-dimensional roughness profile and spanwise variation of the ice shapes, at the time digital scanning and rapid prototyping methods were not sufficiently developed to be used in that test program to capture the three-dimensional ice accretions. Thus, no high-fidelity ice shapes for the subscale model were tested at low-Reynolds numbers.…”

“…Thus, no high-fidelity ice shapes for the subscale model were tested at low-Reynolds numbers. Busch 7 tested three levels of low-fidelity shapes. These included simple geometric shapes, two-dimensional extrusions based on a measured ice cross section, and shapes that included simple representations of the observed spanwise variation in the measured ice accretion.…”

The Impact of Ice Formation on Wind Turbine Performance and Aerodynamics

“…3.2. The use of the relative velocity as an input parameter in the 2D ice accretion code approximates the enhanced accretion of ice due to the effects of rotation [16]. The NREL S809 profile was simulated for all eight locations.…”