ID 20

Hydrodynamics of Multiple Droplet Train Impingement upon a Thin Liquid Film

 

Abstract:

Hydrodynamics of single, double and triple stream droplet trains impinging upon a thin liquid film has been investigated experimentally and numerically. A droplet generator with multi-hole orifice plates was used to produce monodispersed droplets to control droplet properties, such as droplet diameter, droplet velocity, droplet Weber number and stream spacing. Numerically, ANSYS-Fluent was employed to simulate the droplet impingement process using the Volume of Fluid approach coupled with the Level Set method (CLS-VOF). Structured 2D axisymmetric, 3D quarter, 3D half symmetric meshes were created for simulating droplet streams under spreading and splashing con-ditions for single, double and triple stream impingement cases. Dynamic mesh adaption was used to capture the propagation of the droplet-induced crown with time dependent spatial and temporal resolutions. A good agreement was reached between experimental and numerical data in terms of droplet-induced crown diameter, number of cusps and adjacent hump height. In single stream cas-es, the effect of Weber number on spreading to splashing transition has been characterized. In mul-tiple stream cases, the influence of horizontal droplet stream spacing on adjacent hump height and craters interaction have been characterized. Results reveal that the droplet Weber number plays a significant role in the morphology of droplet-induced crown and liquid film in single stream cases. In multiple stream cases, horizontal droplet stream spacing plays a crucial role in terms of hump formation and crater interactions. In summary, the experimental and numerical results to date show that droplet stream properties affect thin film hydrodynamics spatially and temporally.