Droplet Oscillations: Fundamentals, Applications and Methods

Droplet oscillations are seen in many systems and applications such as filtrations, cleaning, and condensation. The droplet oscillations is a complex process especially when the droplet is in contact with a surface such as above applications. The droplet may oscillate as a result of interactions with an airflow present in the system, and/or when the solid surface vibrates. There are many fundamental questions in this area needs to be addressed to allow understanding of the basics of the phenomenon, such as:

• The effect of vibrations on coalescence of droplets in a multi-droplet system, e.g. condensation.
• The effect of droplet oscillations on the flow structure around a droplet and drag force when a shearing airflow exists.
• The effect of droplet vibrations on droplet mobility for surfaces of different wettability with or without and airflow.
• The effect of surface vibrations, amplitude, frequency and direction of vibrations (e.g. normal or in-plane to the droplet) on the above questions 

For various applications the droplet oscillations can be exploited to enhance the process or should be avoided for to improve the performance. 

For instance:

• For condensers, to improve its efficiency one should promote drop-wise condensation mode. Droplet oscillations can be exploited in this case to promote condensate coalescence leading to larger droplets that can be removed by gravity or a shearing airflow.
• For water harvesting applications from air, droplet oscillations can prematurely release droplets from the mesh and reduce collection efficiency
• Droplet movement in fuel cells to increase efficiency and avoid flooding
• Control droplet movement to reduce corrosion by avoiding wet surfaces
• Remove droplets by oscillations in Lidar / camera systems for autonomous driving
• In cleaning, filtration applications to control deposition of particles
• And many more