An experimental investigation on wind-driven rivulet/film flows over a NACA0012 airfoil by using digital image projection technique

Aircraft icing is a serious threat to aviation safety. Icing accretion process usually interacts with surface water run back flow under glaze icing condition. In the present study, an experimental investigation was conducted to characterize the surface wind-driven water film/rivulet flows over a NACA 0012 airfoil in order to elucidate the underlying physics of the transient surface water transport behavior pertinent to aircraft icing phenomena. The experimental study was conducted in an icing research wind tunnel available at Aerospace Engineering Depratment of Iowa State University. A novel digital image projection (DIP) measurement system was developed and applied to achieve quatitative measurements of the thickness distributions of the surface water film/rivulent flow at different test conditions. The measurement results reveal clearly that, after impinged on the leading edge of the NACA0012 airfoil, the micro-sized water droplets would coalece to form a thin water film in the region near the leading edge of the airfoil. Water rivulets were found to be generated as the water film flow runs backs. The width and the spacing of the water rivulets were found to decrease monotonically with the increasing wind speed.