###### Abstract  
The Eulerian Wall Film (EWF) model is a mathematical model employed to analyze the behavior of fluid films on a surface. The model has been widely adopted in various engineering applications due to its accuracy and efficiency. However, it is rarely applied in the aerospace field. The solution of the water-drop impact constitutes an indispensable prerequisite for the computation of ice accretion on the exterior of aircraft wings. In this study, we propose a novel approach for the estimation of water-drop impact on wing surfaces by integrating the Euler-Euler approach and EWF model. This approach is capable of furnishing a point of reference and a theoretical foundation for prospective water-drop impact experiments. Through comparison with pertinent experimental findings, the precision of the numerical simulation approach utilized in this paper is substantiated. Specifically, the research object is the NACA653-218 airfoil of the C-919 transport aircraft, for which the aerodynamic properties, water-drop collision, and liquid film flow characteristics during steady flight were simulated. multiphase flow; granular flow; EWF model; Euler-Euler approach; water-drop collision characteristics +
Footnote †: journal: Applied Sciences  
water-drop impact. The established model can predict the influencing factors of water-drop diffusion and surface subcooling. [PERSON] et al. [12] have devised a tridimensional framework that can be utilized to resolve non-structured meshes; the water-drop collection coefficient and heat transfer coefficient ascertained via this framework approximate those determined by the LEWICE icing software. The surface ice configurations computed for multiple sets of NACA0012 airfoils and cylinders closely resemble the experimental findings. [PERSON] et al. [13] have formulated a theoretical framework capable of forecasting the expansion of rime ice by analyzing the propagation properties of surface acoustic waves; empirical findings from their investigation demonstrate that the formation of ice can be accurately detected through transient modifications in sonic velocity and decay. [PERSON] et al. [14] constructed a tridimensional icing simulation, conducted an analysis of ridge and glaze ice formations on wing blades during low velocity conditions, and computed and juxtaposed the lift-drag ratio of a sleek airfoil against that of an iced airfoil. The EWF model can calculate the flow of the film when water drops splash and adhere to the wall surface by simplifying the fluid film [15]. When coupled with the Eulerian Multiphase Flow model, it can better reflect the collisions of gas on the wall and the flow of the film [15; 16]. [PERSON] et al. [15] studied the gas-liquid separation of supersonic separators using the Eulerian-Lagrange method coupled with the EWF model, considering the phase transition between the phases and the liquid film; they analyzed the sensitivity of the separation efficiency to the inlet pressure, non-uniform water-drop diameter, and inlet water-drop concentration, and explored the optimal inlet water-drop diameter and concentration to improve the separation efficiency of the separator. [PERSON] et al. [17] viewed cells as water drops and captured the liquid phase by using the EWF model to form a liquid film; in this way, they simulated cell attachment. [PERSON] et al. [18] simulated the re-entrainment of water drops in the defogger by coupling a discrete model with the EWF model; the efficiency of defogging and the flow characteristics of the fluid film on the baffle were analyzed in combination with experiments. During the numerical simulation of a cylindrical cyclone separator, [PERSON] et al. [19] applied the EWF model to simulate the flow behavior of the upper vortex liquid film. The EWF model was utilized to investigate falling film evaporation and convective heat transfer of a non-energetic safety cooling system, with the system's performance evaluated based on the model [20].