Simulating the Freezing of Supercooled Water Droplets Impacting a Cooled Substrate

Abstract

To study ice adhesion at the droplet scale, a strategy is presented to simulate the impact and solidification of a supercooled water droplet on a cooled substrate. Upon impact, nucleation is assumed to occur instantaneously, and properties of the droplet are chosen to account for the nucleation process. Simulations are performed in ANSYS Fluent using a coupled volume-of-fluid and level-set method to capture the air-water interface, and an enthalpyporosity method is used to capture the liquid-solid interface. Calibration of a simulation parameter A mush is performed in order to match experimental data for different ideal surface types and surface temperatures. The simulation strategy successfully predicts the overall droplet response for several droplet impact conditions. Nomenclaturewidth on the surface, m d = signed distance to level-set interface f liquid = any physical property of the liquid material f mixture = any physical property of the liquid-solid mixture f solid = any physical property of the solid material k = thermal conductivity, W∕m · K L = specific latent heat of phase change, J∕kg L mixture = specific latent heat of phase change of the ice-water mixture, J∕kĝ n = normal unit vector for level-set interfacê n wall = unit vector normal to wall Oh = Ohnesorge number R = area ratio of droplet on surface Re = Reynolds number r = droplet radius, m r max = maximum droplet radius on surface, m r mixture = droplet radius of ice-water mixture, m St = Stefan number St mixture = Stefan number of the ice-water mixture T freezing = freezing temperature,°C T supercooled = supercooling temperature,°Ct wall = unit vector tangential to wall V 0 = droplet impact velocity, m∕s v = fluid velocity vector, m∕s We = Weber number α = volume fraction α p = volume fraction of primary phase α s = volume fraction of secondary phase β = liquid fraction ΔH = specific latent heat in a computational cell, J∕kg ΔT = degree of supercooling, deg θ = contact angle, deg θ wall = contact angle assigned to wall, deg κ = curvature of level-set interface μ= droplet viscosity, kg∕m · s ρ = density, kg∕m 3 ρ liquid = density of the liquid material, kg∕m 3 ρ p = density of the primary phase, kg∕m 3 ρ s = density of the secondary phase, kg∕m 3 ρ solid = density of the solid material, kg∕m 3 σ = surface tension coefficient, N∕m ϕ = liquid mass fraction φ = level-set function

Photothermal trap utilizing solar illumination for ice mitigation

“…2A, the supercooled droplet suddenly becomes opaque within ~40 ms (see the left snapshot and movie S1). A fraction of the liquid freezes, forming a slushy mixture of ice crystals and liquid at 0°C ( 30 , 31 ). Hereafter, the remaining liquid isothermally freezes at a lower rate (in tens of seconds).…”

Advances in the development of superhydrophobic and icephobic surfaces

“…Other studies investigated the effect of different surface hierarchical structures on the adhesion and rebound of impacting supercooled droplets (Mishchenko et al 2010 ; Zhang et al 2018d ). Moreover, few researchers developed Volume of fluid (VOF) numerical models to simulate he impingement and freezing of supercooled droplets on superhydrophobic surfaces (Zhang et al 2020b ; Tembely et al 2018 ; Shinan et al 2019 ; Blake et al 2015 ).…”

Impact Dynamics and Freezing Behavior of Surfactant-Laden Droplets on Non-Wettable Coatings at Subzero Temperatures

“…In the past decade, icephobic coatings have found broad applications in high-tech industrial fields, including powerlines, wind turbines, aircrafts, and heat exchangers . The focus of studies in this field can be divided into several main categories, including surface chemistry and morphology of icephobic coatings, − ice nucleation and adhesion of sessile droplets, , droplet impact, − and fabrication of superhydrophobic coatings as a passive method for anti-icing. − …”