Droplets impact against the random rough surface with a liquid film

Aero-engine fouling will affect the economy and safety of aircraft, and online washing is the main method to solve the problem of aero-engine fouling. Online washing is considered to be the removal of fouling particles by the impingement of droplets on a flowing liquid film. Here, we simulate a flowing liquid film of droplets impinging on a randomly rough surface to predict the removal of fouling particles. We considered the situation that the horizontal flow velocity of the liquid film is between 5 and 20 m/s and the thickness of the liquid film is 5–20 μm. An analysis of the droplet impact velocity field, radial velocity, and extension length shows that the vortex strength, radial velocity, and extension length all increase with increasing liquid film flow velocity, while increasing liquid film thickness inhibits the growth. Moreover, we constructed a fouling particle detachment model to evaluate the effects of different liquid film flow velocities and film thicknesses on particle removal. A particle removal plot shows the dominance of liquid film flow velocity stations. This study not only reveals the removal process of fouling particles on random rough surfaces but also provides insight into the optimization of spray cleaning process parameters.