Research On Droplet’s Spreading And Oscillating On Surface

People often come into contact with the phenomena of droplet colliding on the surface. For example:Raindrop colliding with aircraft and other transportation, the spray evaporating of sea water desalination, the spray hitting the wall of internal combustion engine, the interaction between the droplet and turbine blades et al. Droplet hitting the wall and its oscillation process are an important research topic in the field of two-phase flow.Hydrophilicity is an important feature of the solid wall. The microstructure and chemical composition of the wall are the main determinant. Firstly, The paper uses the VOF (volume of fluid) model to simulate the droplet colliding and spreading out on a rough wall in two-dimensional space. The surface is a concave and convex shape with a high degree rule. The dynamic shapes and the maximum spreading radius of droplet are simulated to analysis the effect of geometric parameters of surface microstructure and the intrinsic contact angle on the hydrophilic and hydrophobic surface.Secondly, the paper simulates the droplet colliding and spreading out on the dry and wet rough wall which the geometric parameters are fixed. The droplet impacts on the two groups of wall at different speeds. The flowing pattern, spreading radius and spreading rate of droplet are simulated to analysis the effect of the impact velocity and microdroplets in the wet rough wall on the droplet spreading in the early stages of the spreading, middle and late.Finally, the droplet on the flat surface is simplified to a semi-ellipsoidal and semi-spherical shape. And the paper establishes the droplet oscillating mathematical model in consideration of the inertial force, interfacial tension, internal pressure and wall friction. This mode gives the mathematical relationship between the radius of the droplet and the droplet volume, spreading rate, kinematic viscosity, density, surface tension coefficient and contact angle. Comparing the theoretical models’calculated datum with the experimental datum, both have a good agreement, and it illustrates the feasibility of the theoretical models. And on this basis, the paper further analyzes the effect of the droplet size, kinematic viscosity, spreading velocity, density, contact angle and surface tension coefficient on the droplet’s oscillation.