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The hydrodynamic details of droplet-droplet and droplet-liquid film interactions on solid surfaces are believed to have a significant role in spray impingement phenomena, yet details of this interaction have not been clearly identified. The interaction among the droplets during impact affects their residence time on the surface, spreading, and droplet and liquid film stability. After impact, droplet interactions affect droplet collisions, coalescence and liquid splashing, This interaction affects secondary atomization and the droplet dispersion characteristics of the impingement process. In this study, details of droplet-droplet and droplet-liquid film interactions in solid surface impingement have been visualized using high speed photography. The effects of these interactions on secondary atomization and droplet dispersion have been quantified.

Gas-side temperature profile measurement in engines may provide valuable information regarding surface heat transfer as well as information on other fluid characteristics such as boundary layer thickness. Due to the typical cyclic variation of fluid variables in engines, profile measurement must be accomplished essentially instantaneously. This paper describes the use of speckle interferometry for acquiring such data. The advantages and disadvantages of the method will be briefly described with respect to current spectroscopic and other interferometric techniques. The method has been applied to measure temperature profiles normal to the cylinder head in a motored two-cycle engine. The resulting temperature profiles for a variety of crank angles are presented. Estimates of thermal boundary layer thickness and surface heat transfer are also presented.