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Technical Paper

Validation of Ice Roughness Analysis Based on 3D-Scanning and Self-Organizing Maps

2019-06-10
2019-01-1992
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.
Technical Paper

Extension of a 2D Algorithm for Catch Efficiency Calculation to Three Dimensions

2019-06-10
2019-01-2013
Accurate calculation of the catch efficiency β is of paramount importance for any ice accretion calculation since β is the most important factor in determining the mass of ice accretion. A new scheme has been proposed recently in [1] for accurately calculating β on a discretized two-dimensional geometry based on the results of a Lagrangian droplet trajectory integrator (start and impact conditions). This paper proposes an extension to the algorithm in Ref. [1], which is applicable to three-dimensional surfaces with arbitrary surface discretization. The 3D algorithm maintains the positive attributes of the original 2D algorithm, namely mass conservation of the impinging water, capability to deal with overlapping impingement regions and with crossing trajectories, computational efficiency of the algorithm, and low number of trajectories required to reach good accuracy in catch efficiency.
Technical Paper

Aerodynamic Assessment of Complex 3D Ice Shape Replications

2019-06-10
2019-01-1936
This work introduces an approach allowing the detailed replication of ice shapes generated in icing wind tunnels, with a special focus on complex and strongly varying ice structures, e.g., ice feathers or residual ice stemming from incomplete removal of accreted ice by ice protection systems. 3D-scans are used as an input for the manufacturing process of the ice shape replica. The manufacturing approach itself is based on additive techniques using semi-flexible materials. In contrast to existing replication techniques, this approach allows also clean areas between ice-covered surface locations. In the present paper, a quality assessment based on the comparison of the lift coefficients of real and corresponding artificial ice shapes is presented.
Technical Paper

A Refined In-Flight Icing Model and its Numerical Implementation

2019-06-10
2019-01-1937
A refined in-flight icing model is proposed whose primary focus lies on an improved prediction of the runback dynamics. The most significant capabilities/properties of the model are: Incorporation of surface tension and wetting effects in the runback model Fully transient treatment of the ice accretion/depletion process and the runback flow Treatment of unsteady heat transfer in the runback layer, the accreted ice layer and the underlying substrate as well as phase transitions solid/liquid in the ice layer Strict mass- and enthalpy-conservative growth/depletion of the ice layer (this is achieved by a specially designed mesh deformation algorithm) An essential part of the paper is devoted to the treatment of surface tension and wetting effects: These effects result from disjoining pressure contributions to the pressure terms in the runback continuity equation, i.e., these effects are inherent properties of the simulated runback dynamics.
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