Liquid film may form on a wall as a consequence of sticking, splashing or spreading impingement. Wall film dynamics is influenced by the impinging sprays, the wall conditions, and the gas flow near the wall. The impinging spray affects the film through mass, tangential momentum, and energy addition. The wall affects the film through the no-slip boundary condition and heat transfer. The gas flow affects the film dynamics through tangential shear stresses and the mass and energy exchange between the film and the gas.

The wall film model by O’Rourke and Amsden [[63] , [64] ] is employed in Ansys Forte. This model uses a particle numerical method to represent the wall film. In the particle method, each spray particle is tracked as a spherical particle while it moves on the wall surface. In calculating the mass and energy exchange between the wall film and the ambient gas through vaporization, the wall film particles within the same computational cell are converted to a thin film based on the total volume of the liquid and the boundary surface area associated with the corresponding cell.