Theoretical Research On Static Spreading Of Droplet Impact On Horizontal Surface

The mutual mechanisms between the droplet and the wall when the droplet impacts on the horizontal surface are widely used in the the fields of industrial manufacturing, agriculture and medical, for examples, falling film evaporation of sea water desalination, ink-jet printing, coating and spray cooling. The results of droplets impact on the solid surface are effected by many factors, such as the droplets’physical properties, wall’s roughness, the impact velocities, the impact contact angles, the interaction between the droplets and the wall and so on. The droplet spreading shapes and the flow processes can be ordinary described by the dimensionless quantity (We、 Re、 Ca). Making effective researches about the relationships between the droplets’ spreading shapes and the initial parameters, the droplet-wall’ s interaction can be better to predict the process of droplets impact on solid surface. It has remarkable guidance significance to the practical application.The paper has established the semi-ellipsoidal droplet and the semi-spherical droplet models by analyzing the force balance of the internal differential elements when the droplet maintains equilibrium on the horizontal surface. By the force balance equations between the droplets’surface tension and the internal pressure, and the geometrical relationship from the semi-ellipsoidal droplet and the semi-spherical droplet, the author deduces theoretical relationships between the static spreading radii and the droplet’s density, the volume, the surface tension coefficient and the contact angle. The static spreading parameters solved by the theoretical equations are compared with those from the experimental data. It turned out that the established models can be described accurately the static force balance of the droplets. And the theoretical results also agree well with those from the VOF methods in fluent software.The paper analyzes the influence of the droplet’s density, the volume, the surface tension coefficient, the contact angle on the static spreading radius by studying the theoretical expressions of the static spreading radius obtained above. It turns out that the influence rules of the semi-ellipsoidal droplet and the semi-spherical droplet models are the same. It presents that the static spreading radius increases when the density or the volume increases, decreases when surface tension coefficient or the contact angle increases. And it has nothing to do with velocities.