Experimental Study of Water Film Dynamics Under Wind Shear and Gravity

Abstract

Aircraft icing poses a serious threat to flight safety. Unfrozen impinging water on the surface of the aircraft will run back under the effect of high-speed airflow, altering liquid distribution and heat transfer characteristics. In this paper, a series of experiments are conducted over a wide range of wind speeds (), film Reynolds numbers (), and inclined angles (, , ) to investigate the dynamics of thin water film on an aluminum substrate. The superficial morphology of the water film is investigated by a high-speed camera, and the instantaneous film thicknesses are measured by a laser focus displacement meter based on a confocal chromatic technique. The interface shape is found to consist of an underlying thin film and multiple scaled fluctuations; therefore, the results are divided into two parts for analysis: the mean film thickness and the root-mean-square thickness. A relationship between the mean film thickness and the wind speed, the film Reynolds number, the inclined angle is proposed. After nondimensionalized processing based on the triangular relationship, the averaged film thickness data agree with the previous model of an error within 25%. New correlations to calculate the interfacial shear stress and superficial roughness are suggested within the experimental range.