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In the scope of development or certification processes for the flight under known icing conditions, aircraft have to be tested in icing wind tunnels under relevant conditions. The documentation of these tests has to be performed at a high level of detail. The generated data is used to prove the functionality of the systems, to develop new systems and for scientific purposes, for example the development or validation of numerical tools for ice accretion simulation. One way of documenting the resulting ice geometry is the application of an optical 3D scanning or reconstruction method. This work investigates and reviews optical methods for three-dimensional reconstructions of objects and the application of these methods in ice accretion documentation with respect to their potential of time resolved measurement. Laboratory tests are performed for time-of flight reconstruction of ice geometries and the application of optical photogrammetry with and without multi-light approach.

When studying ice accretion processes experimentally it is desirable to document the generated ice shapes as accurately as possible. The obtained set of data can then be used for aerodynamic studies, the improvement of icing test facilities, the development of design criteria, the validation of ice accretion simulation tools as well as other applications. In the past, various ice shape documentation methods have been established including photography, cross-sectional tracing, molding and casting as well as 3D-scanning. This work introduces a new ice shape documentation technique based on active 3D-scanning in combination with fluorescent dyes and an optimized set of optical filters. The new approach allows recording the time-resolved three dimensional growth of an arbitrary ice shape. Based on this concept a so-called 4D-scanning system is developed, which allows a detailed evaluation of icing experiments and hence a better understanding of the ice accretion process itself.

3D-scanning is an established method for the documentation of wing ice accretion. The generated 3D-data can be used to determine specific parameters of interest, like the local ice-thickness, or the surface ice roughness. The surface roughness has significant impact on the heat transfer, and therefore on the icing process itself. Insights into the effects of surface roughness on the ice accretion and the correlated aerodynamical effects contribute to the improvement of icing codes. In this paper, the surface roughness of various test specimens is determined by performing a self-organizing maps (SOM) approach for roughness point cloud analysis on data generated with a 3D-scanner. A validation of the SOM method is achieved by means of focus variation microscopy and a mathematical proof of the utilized SOM algorithm. Different scanning systems from several manufacturers are used to determine the surface of different sandpapers.