A novel virtual boundary-based surface tension model and its application to wetting and thermal capillary effect

A novel Virtual Boundary-based Surface Tension model for Lagrangian meshless particle methods is proposed in this paper. It circumvents curvature computation by directly representing surface tension as tension components acting on surface particles along virtual boundaries constructed from local particle distributions. The surface tension gradient has been taken into consideration. The model is extended to a Virtual Boundary Contact Angle formulation that naturally captures three-phase contact line dynamics. The performance of the models is verified through tests, including the free oscillation of a square droplet, the rising bubble problem, binary droplet collision, droplet wetting on a solid surface, non-isothermal liquid bridge, and droplet impacting on plate. Validation against benchmarks shows excellent agreement about the calculation results of surface tension and contact angle values. The model demonstrates strong robustness and applicability to multiphase and thermal capillary effect problems. The proposed approach combines computational simplicity with physical fidelity. It provides a robust framework for multiphase flow simulations involving surface tension and wetting phenomena.