Investigation on wavy characteristics of shear-driven water film using the planar laser induced fluorescence method

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 were conducted over a wide range of air speed (Ua = 20.8–56.6 m/s), film Reynolds number (Ref = 26–128) to investigate the dynamics of ultrathin water film on an Aluminum substrate. The analyses of water film thickness and wavy characteristics were conducted through the planar laser-induced fluorescence method, in which the variations of transient characteristics of water film thickness with both the air speed and flow rate were analyzed. The statistics of water film thickness characteristics indicates that, the ratio of surface roughness of water film to its mean thickness is 0.4–0.8. The variation of the wave parameters of gas-liquid interface with both the air speed and the Reynolds number of the water film are also presented and analyzed in detail, including the main frequency of wave, interface wave height, surface wave velocity, interface wave curvature, and wave length parameters. This work is helpful to fundamentally understanding the wavy characteristics of shear-driven water film, as well as optimize the de-icing system for aircraft.