Validation of 3-D ice accretion documentation and replication method including pressure-sensitive paint

Accurate representation of ice accretions is important to the study and understanding of aircraft icing. For research and certification purposes, replicas of ice accretions generated from icing wind tunnels are fabricated to perform aerodynamic tests in dry-air wind tunnels. The currently employed replication method consists of creating molds from original ice accretions and producing castings from the molds for wind tunnel testing. While this method reproduces the geometric features and aerodynamic effects of the original ice accretions well in the replicated ice shapes, it has several limitations. This method cannot scale the ice shapes to sizes other than the original and does not produce a digital record of the ice shape. Both of these capabilities are desirable in iced-aerodynamics research. To address these needs, NASA developed a methodology to obtain a digital record of ice accretions through the implementation of a laser scanner system. The resulting scan can be used in conjunction with rapid-prototype methods to generate ice shapes for wind tunnel testing. This work is a validation of the 3-D ice accretion measurement methodology where the ice shapes generated by both the currently-used and newly-developed methods from the same initial ice accretion are compared using force balance-derived aerodynamic performance, surface and wake pressures, and pressure-sensitive paint (PSP) data. The 3-D features of the tested ice shapes necessitated the use of a technique capable of obtaining high resolution data. The PSP technique allowed pressure coefficient data to be obtained over a larger area and at a greater resolution than is possible by only using the surface pressure tap method. The results discussed show the capability of the PSP technique, as implemented in the 3ft by 4ft subsonic wind tunnel at the University of Illinois, to resolve aerodynamic differences between ice shapes made from both the current and newly developed ice accretion replication methods. The same trends were observed in the PSP data as were found in the aerodynamic performance and pressure tap data, and the newly developed 3-D ice accretion measurement methodology produced ice shapes which aerodynamically agreed well with ice shapes generated from the mold and casting method