THE DENSITY AND STRUCTURE OF ICE ACCRETION PREDICTED BY A RANDOM-WALKMODEL

A random-walk, ballistic-type model is used to simulate the ice accret ion process due to impinging supercooled droplets. The model is applic able over a wide range of growth conditions including, in the limit, g rowth where the droplets freeze virtually as spheres (dry growth), and growth where the droplets spread into and across the ice surface losi ng their identity (wet growth). The structure and density of the ice a re determined by the probabilities governing droplet motion and freezi ng during their random walk along the ice deposit. A relationship betw een the Macklin parameter, commonly used to relate atmospheric conditi ons to ice density, and the probabilities of droplet motion has been e stablished. The ice density and accretion structure predicted by the r andom-walk model agree qualitatively with experimental observations at the stagnation line on a fixed circular cylinder. The model also pred icts finger-like ice structures for small values of droplet momentum, also in keeping with observations.