Breakup and Evaporation: Water Spraying

Water Spraying Considering Breakup and Evaporation, ANSYS Fluent Training

Description

This project simulates water spraying from a nozzle, capturing the full spectrum of spray behavior — droplet formation, breakup, evaporation, and wall film formation — by combining the Discrete Phase Model (DPM) with the Species Transport model in ANSYS Fluent.

The simulation models 2 mm diameter water droplets injected at 1.25 m/s, with evaporation triggered once droplets reach a temperature threshold of 282.5 K. Droplet breakup was captured using the Taylor Analogy Breakup (TAB) model, alongside stochastic collision and coalescence to represent droplet-to-droplet interaction throughout the spray.

Methodology

A dynamic-drag law was applied to account for non-spherical droplet shapes as they deform and break apart, while the Discrete Random Walk model captured turbulent dispersion effects on individual droplet trajectories. Surface interactions were modeled using Wall-Film DPM boundary conditions, allowing droplets reaching a surface to realistically stick, rebound, spread, or splash depending on local impact conditions.

Conclusion

The results reveal a droplet diameter distribution spanning from 0.002 mm to 7 mm, reflecting the combined effects of breakup and evaporation on droplet population over the course of the spray. Droplet behavior upon surface impact — sticking, rebounding, spreading, or splashing — was captured and analyzed in detail through the wall-film boundary conditions, with the full spray dynamics visualized through animations and contour plots.

Together, these results provide a comprehensive picture of how droplet breakup, evaporation, and surface interaction shape overall spray behavior — offering insight directly applicable to nozzle design optimization, spray cooling systems, fuel injection processes, and coating applications where accurate droplet-scale prediction is essential.