splashes

Splashes refer to the rapid displacement and fragmentation of a liquid that occurs when a drop or jet collides with a surface or another body. The collision can create a transient liquid sheet or crown that may thicken, entrain air, and break apart into droplets. Splashes appear in everyday events such as raindrops hitting a puddle, as well as in industrial processes like inkjet printing, spray cooling, and agricultural spraying.

Mechanism and dynamics are driven by a competition between inertia, surface tension, and viscosity. When inertial forces exceed the restoring force of surface tension, the liquid sheet or rim can become unstable, forming ligaments that break into droplets. On a solid surface, a crown or splash cone may develop; in a liquid bath, a jet and complex interfacial flows can occur. Factors influencing splashes include drop size, impact velocity, liquid density and viscosity, surface tension, ambient air pressure, and surface properties such as roughness and wettability.

The phenomenon is often analyzed with dimensionless numbers that summarize the relevant forces. The Weber number (We = ρV^2L/σ) compares inertia to capillarity, the Reynolds number (Re = ρVL/μ) compares inertia to viscosity, and the Ohnesorge number (Oh = μ/√(ρσL)) incorporates all three. Critical conditions for splashing depend on the specific liquid and surface, and can be altered by external factors like air pressure and contamination.

Applications and implications vary by context. Splashes are exploited in inkjet printing and spray deposition, while uncontrolled splashing can lead to contamination, waste, or safety hazards. Techniques to suppress splashing include increasing viscosity, altering surface tension, modifying ambient pressure, and using textured or absorbent surfaces.