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An experimental and computational investigation of spray impingement on a flat surface is presented. Different angles of incidence are studied, namely 30, 45 and 60°C measured from the normal to the surface. Back-lit photographs of the wall spray taken at various times during the impingement period give a qualitative view of the secondary atomization process. A stochastic model based on the sampling of velocity and size distributions of secondary droplets is used to simulate the creation of incident droplet fragments created by the numerous splashing events occurring during the impingement period. Size characteristics of the secondary droplet cloud are computed at various points in the impingement region and these are compared against phase/Doppler particle analyser (P/DPA) measurements yielding reasonable agreement. The effect of surface roughness is incorporated into the model and is found to play a major role in affecting the splashing threshold and the sizes of splashing fragments. The secondary droplet distributions are virtually unchanged among the different angles of incidence. This behaviour is explained by considering the shift in the splashing droplet distribution as a function of incident angle.

The typical crown formation created by the impact of a single drop on a slightly wetted target surface is treated as a series of two surfaces of discontinuity from which the jump momentum and mass equations are developed along with the governing equation for crown radius. The crown radius equation is solved in conjunction with the governing equations of the flow emanating from drop/wall impact. This flow is modeled initially as a cylindrical region of prescribed height and velocity. Both viscid and inviscid situations are treated. For the inviscid case of a crown moving through a motionless film, analytical solutions are found for the evolution of film height and velocity. For the viscid situation, a numerical scheme based on the discretization of the governing equations along the characteristic directions is employed. The results are validated by comparing with experimental and computational results from the literature. The effects of target surface film height, velocity, and wall friction on the crown dynamics are investigated.