Revisiting the modelling of droplets passing through a superhydrophobic orificeBerce, Jure (Avtor) Jereb, Samo (Avtor) Golobič, Iztok (Avtor) droplet separationsuperhydrophobic surfaceorificedroplet sizeforce balancelaser-texturingYoung-Laplace equationPrecise analytical modeling of droplet size passing through a superhydrophobic orifice is vital for various industrial and scientific applications. The very few published theoretical models rely on spherical droplet assumptions, which proved inaccurate for larger orifices due to gravity-induced droplet deformation. To address this limitation, an analytical model for quasi-static droplet size separation is presented, successfully integrating contact angle hysteresis and gravitational effects. The new model determines the critical separation diameter by analyzing the free-surface droplet profile governed by surface tension, internal liquid pressure, and hydrostatic forces across a toroidal orifice edge. Validation using existing experimental results demonstrated excellent model accuracy (R$^{2}$ = 0.9815, RMSE = 0.0566 mm) and a detailed description of droplet shape evolution. A comprehensive parametric study subsequently revealed that contact angle hysteresis and orifice height have minimal practical influence on the critical droplet volume. Conversely, varying liquid properties significantly affect the separation size. Specifically, the critical droplet volume is mainly governed by the ratio of liquid density to surface tension, which dictates the extent of gravitational deformation. This framework provides a robust theoretical tool for designing passive, gravity-driven separation devices across diverse working liquids.20262026-09-01 11:21:20Članek v reviji186416sl