Determining the adverse aerodynamic effects due to ice accretion often relies on dry-air wind-tunnel testing of artificial, or simulated, ice shapes. Recent developments in iceaccretion documentation methods have yielded a laser-scanning capability that can measure highly three-dimensional features of ice accreted in icing wind tunnels. The objective of this paper was to evaluate the aerodynamic accuracy of ice-accretion simulations generated from laser-scan data. Ice-accretion tests were conducted in the NASA Icing Research Tunnel using an 18-inch chord, 2-D straight wing with NACA 23012 airfoil section. For six iceaccretion cases, a 3-D laser scan was performed to document the ice geometry prior to the molding process. Aerodynamic performance testing was conducted at the University of Illinois low-speed wind tunnel at a Reynolds number of 1.8×10 6 and a Mach number of 0.18 with an 18-inch chord NACA 23012 airfoil model that was designed to accommodate the artificial ice shapes. The ice-accretion molds were used to fabricate one set of artificial ice shapes from polyurethane castings. The laser-scan data were used to fabricate another set of artificial ice shapes using rapid prototype manufacturing such as stereolithography. The iced-airfoil results with both sets of artificial ice shapes were compared to evaluate the aerodynamic simulation accuracy of the laser-scan data. For four of the six ice-accretion cases, there was excellent agreement in the iced-airfoil aerodynamic performance between the casting and laser-scan based simulations. For example, typical differences in iced-airfoil maximum lift coefficient were less than 3% with corresponding differences in stall angle of approximately one degree or less. The aerodynamic simulation accuracy reported in this paper has demonstrated the combined accuracy of the laser-scan and rapid-prototype manufacturing approach to simulating ice accretion for a NACA 23012 airfoil. For several of the ice-accretion cases tested, the aerodynamics is known to depend upon the small, threedimensional features of the ice. These data show that the laser-scan and rapid-prototype manufacturing approach is capable of replicating these ice features within the reported accuracies of the laser-scan measurement and rapid-prototyping method; thus providing a new capability for high-fidelity ice-accretion documentation and artificial ice-shape fabrication for icing research.casting = drag coefficient for the three-dimensional casting C d,rpm = drag coefficient for the RPM simulation ΔC d,rms = root-mean-square percent difference in drag coefficient between the RPM simulation and the threedimensional casting simulation over a given angle of attack range C l = lift coefficient C l,max = maximum lift coefficient, coincident with stalling angle C m = quarter-chord pitching moment C p = pressure coefficient k = ice roughness height or ice thickness LWC = Liquid Water Content M = freestream Mach number N = number of angles of attack Re = freestream Reynolds number based on chord α = angle of atta...
This paper discusses the use of several experimental techniques to investigate the performance and flowfield of a swept wing with leading-edge ice at low Reynolds numbers. Force balance measurements were made over a range of angles of attack and Reynolds numbers. Surface oil visualization and pressure sensitive paint were used to investigate the flow over the surface of the wing, while five-hole probe wake surveys were used to investigate the wake. The flowfield of the iced swept wing was dominated by a leading-edge vortex that formed at low angles of attack due to separation from the tip of the ice shape, while for the clean wing a vortex did not form until higher angles of attack. The effect of Reynolds number on the performance and flowfield was also investigated.
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