Hydrodynamics and Heat Transfer in a Liquid Film Flowing Over a Spinning Disk With Specific Wall Topography

One of the most commonly used methods of liquid atomization is the rotary atomization, or spinning disk atomization. This technique makes use of centrifugal forces to create a thin liquid film spreading radially over a disk. The film flowing along the disk is mostly wavy. The waves have a negative influence on the drop size distribution in the atomization process. It is known that the waves on the falling films can be suppressed by using walls with longitudinal mini grooves. Due to the similarity of the physical mechanisms governing the wave development on falling films and on films flowing over spinning disks, we suggest using grooved disk surfaces for suppressing the waves in spinning disk atomizers. We develop a physico-mathematical model for description of the film dynamics on a spinning disk with wall topography. The model is based on the long-wave theory. It takes into account the hydrodynamic effects governed by liquid viscosity, centrifugal force, inertia and surface tension, as well as the heat transfer between the disk, the liquid, and the ambient gas. The wall surface topography induces a thermocapillary flow in the liquid film leading to heat transfer enhancement and influencing the hydrodynamics. We show that the disk surface topography significantly affects the film hydrodynamics.