서강대학교

초록/요약

Numerical simulation is performed for the evaporation of a droplet impacted on a porous surface. The droplet interface is tracked by a level-set(LS) method, which is modified to include the effects of porosity and evaporation coupled to heat and mass transfer. The conservation equations of mass, momentum, energy and vapor fraction for the external fluid region are combined with the local volume averaged conservation equations for the porous region through the matching conditions of velocity, pressure, temperature and vapor fraction at the fluid-solid interface. The temperature and the vapor fraction at the liquid-gas interface and the evaporation mass flux are simultaneously determined from the coupled equations for the mass and energy balances at the interface and the thermodynamic relation. The computations demonstrate not only the evolution of the liquid-gas interface during the whole period of droplet penetration and evaporation in a porous medium, but also the associated flow, temperature and vapor fraction fields. The effects of velocity, contact angle, porosity, particle size and thermal properties on the droplet deformation and evaporation are investigated.