A research program has been implemented to develop and validate the use of a commercial 3-D laser scanning system to record ice accretion geometry in the NASA Icing Research Tunnel. A main component of the program was the geometric assessment of the 3-D laser scanning system on a 2-D (straight wing) and a 3-D (swept wing) airfoil geometries. This exercise consisted of comparison of scanned ice accretion to castings of the same ice accretion. The scan data were also used to create rapid prototype artificial ice shapes that were scanned and compared to the original ice accretion.The results from geometric comparisons on the straight wing showed that the ice shape models generated through the scan/rapid prototype process compared reasonably well with the cast shapes. Similar results were obtained with the geometric comparisons on the swept wing. It was difficult to precisely compare the scans of the cast shapes to the original ice accretion scans because the cast shapes appear to have shrunk during the mold/casting process by as much as 0.10-inch. However the comparison of the local ice-shape features were possible and produced better results. The rapid prototype manufacturing process was shown to reproduce the original ice accretion scan normally within 0.01-inch. NomenclatureCAD = Computer aided design CT = Computed tomography IRT = Icing Research Tunnel LWC = Liquid water content MVD = Median volumetric diameter RPM = Rapid prototype manufacturing SLA = Stereolithography T 0 = Total air temperature t = Icing spray time V = Tunnel airspeed α = Angle of attack Λ = Wing sweep angle *

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Ice accretion codes depend on models of roughness parameters to account for the enhanced heat transfer during the ice accretion process. While mitigating supercooled large droplet (SLD or Appendix O) icing is a significant concern for manufacturers seeking future vehicle certification due to the pending regulation, historical ice roughness studies have been performed using Appendix C icing clouds which exhibit mean volumetric diameters (MVD) much smaller than SLD clouds. Further, the historical studies of roughness focused on extracting parametric representations of ice roughness using multiple images of roughness elements. In this study, the ice roughness developed on a 21-in. NACA 0012 at 0 angle of attack exposed to short duration SLD icing events was measured in the Icing Research Tunnel at the NASA Glenn Research Center. The MVD's used in the study ranged from 100 µm to 200 µm, in a 67 m/s flow, with liquid water contents of either 0.6 gm/m 3 or 0.75 gm/m 3 . The ice surfaces were measured using a Romer Absolute Arm laser scanning system. The roughness associated with each surface point cloud was measured using the two-dimensional self-organizing map approach developed by McClain and Kreeger (2013) resulting in statistical descriptions of the ice roughness. Nomenclature Ac = accumulation parameter AOA = angle of attack b = codebook vectors h(i,j) = neighborhood function of i to j codebook vectors j = codebook vector index LWC = liquid water content [gm/m 3 ] M = number of codebook vectors MVD = median volumetric diameter [µm] N = airfoil or mean ice shape surface normal coordinate direction R 2 = coefficient of determination (regression) R d = high-dimensional data space RMH = roughness maximum height R q = the root-mean-square or "standard deviation" roughness height r a = leading edge radius of curvature SOM = Self-Organizing Map 2 S = airfoil or mean ice shape surface tangential coordinate direction SEE = Standard error of the estimate for regression x = element of data set  = local direction angle of manifold through a codebook vector β = manifold  = direction angle of surface point relative to manifold direction through winning codebook vector  = scaling parameter governing neighborhood size  = learning rate

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