Evaporation of nonspherical droplets on chemically patterned substrate considering gravity: A computational study

A liquid–solid interaction-based dynamic mesh model simulated evaporation of nonspherical droplets on a patterned substrate. The model includes contact angle hysteresis, ensuring droplets’ initial morphology follows minimum energy principles. The evaporation model was validated against experiments with both spherical and nonspherical droplets. Investigation of 70μL droplets under three gravity conditions revealed distinct morphological behavior: the sessile droplet exhibited increasing interfacial curvature radially, the pendant droplet showed decreasing curvature, and the microgravity droplet maintained nearly constant curvature. Droplet morphology affected flow and temperature distributions during the CCR mode at different substrate temperatures. The pendant droplet exhibited higher interfacial temperature difference and average velocity at Tw=298.15K, while the sessile droplet had the highest values at Tw=328.15K. Evaporative flux distribution differed, with the pendant droplet having higher flux near the top, and the sessile droplet near the contact line. Entering the CCA mode reduced morphology’s influence on evaporation, converging evaporative flux and rate among droplets. This study confirms that gravity enhanced droplet evaporation, and a proportional relationship exists between evaporation rate and the square root of the evaporative surface area for droplets in the same evaporation mode. •A dynamic mesh model was built to study the gravity effect on droplet evaporation.•Contact angle hysteresis arising from chemical patterns was included in the model.•Due to gravity, sessile droplet is flattened while pendant droplet is elongated.•Gravity effect on droplet flow, temperature and evaporation flux were studied.•Spherical microgravity droplets consistently exhibit the longest evaporation time.