Waterbowls: Reducing Impacting Droplet Interactions by Momentum Redirection

Area of Science:

• Surface Science
• Fluid Dynamics
• Heat Transfer

Background:

• Superhydrophobic surfaces minimize mass/energy transport from impacting droplets by promoting bouncing.
• Reducing droplet contact time is a focus, but large contact area limits overall transport reduction.
• Conformal spreading of droplets on surfaces dictates contact area, hindering further transport minimization.

Purpose of the Study:

• To design superhydrophobic surfaces that reduce droplet contact area by redirecting lamella momentum.
• To investigate the impact of surface discontinuities on droplet behavior and momentum transfer.
• To quantify the reduction in heat transfer achieved by these novel surfaces.

Main Methods:

• Designing superhydrophobic surfaces with in-plane discontinuities.
• Analyzing droplet-surface interactions and momentum redirection.
• Measuring heat transfer reduction between impacting droplets and a surface.

Main Results:

• Surfaces were designed to eject the spreading lamella into 3D shapes, dramatically reducing contact area.
• A 2-fold reduction in heat transfer was demonstrated for cold rain impacting a warm surface.
• Vertical momentum accumulation led to out-of-plane ejection of the lamella.

Conclusions:

• Novel superhydrophobic surface design significantly reduces droplet contact area by redirecting momentum.
• This approach offers a 2-fold improvement in heat transfer reduction compared to conventional methods.
• Applications include preventing icing, reducing salt deposition, and inhibiting water film formation.