The Role of Droplet Modeling in a Five-Field Model of Ice Accretion

The impingement and ice accretion of droplets on wing surfaces presents a serious challenge to aircraft safety and efficiency. We have developed an Eulerian multiphase model of icing. Five fields are transported including compressible air, water-vapor, droplets, film and ice. An immersed boundary method is employed to accommodate ice accretion. In this talk we will focus on droplet dynamics and heat and mass transfer modeling. Specifically, we have incorporated models for film deposition due to impaction and turbulent diffusion mechanisms, splashing, bouncing and re-entrainment, droplet heat transfer and attendant mass transfer evaporation, condensation, and freezing. We present predictions of collection efficiency on different airfoils to validate the numerous interfacial mass and dynamics models involved in the deposition process. It is found that for airfoil ice-shape modeling at relevant atmospheric conditions, it is critical to incorporate accurate modeling of the impaction, diffusion and splash/bounce elements of deposition processes, whereas re-entrainment is not as dynamically important. Also, the roles of droplet initial conditions (liquid, partially frozen, ice) and size distributions are explored in the context of their impact on ice shape.