Extension of Surface Roughness Model for 2nd Generation Aircraft Icing Code

Abstract

Surface roughness should be taken into account when numerically predicting the aircraft icing shape since it affects the underlying physics of the frozen surface. However, empirical correlation equation based on experimental results has been widely used due to its simplicity and limitations of numerical methods for applying the physical model. To present the physical features of surface roughness, this paper proposes the extended roughness model implemented to the 2nd generation aircraft icing code based on the previously proposed analytical model. When applying the model, the analytical solution for the film thickness is derived based on modified governing equation. Then, through the force equilibrium equation, the maximum bead height and minimum film height are computed. Subsequently surface roughness and surface state are determined by comparing with the film thickness. For the verification of the model, the roughness height, heat convections and shapes were compared with numerical results with other roughness models and experimental results. The changes in roughness height and heat convection were evident, but the shape was not significantly different from the numerical correlation results. Specifically, the reason for the change in roughness and heat convection is discussed. Finally the qualitative discussion is made for the little change in shape, and the necessity of the model was presented compared with the result of empirical correlation.