A study of the relation between ice accretion shape and ice under freezing rain conditions

摘要

The influence of atmospheric conditions (specifically total precipitation, precipitation rate and total heat flux) on the freezing rain ice accretion forming on a non-rotating cylinder is studied using an analytical model based on a simple form of the equations for conservation of mass and heat balance. In keeping with the freezing rain application, we have assumed vertical incidence of precipitation (no wind) and no dripping from the accretion (hence light to moderate precipitation rates with relatively low air temperatures). The initial ice accretion shape and its centre of mass are examined as a function of the dimensionless ratio of the precipitation flux to the total heat flux lost from the ice surface. An increase in this ratio leads to a downward displacement of the accretion centre of mass. We complement this analysis with numerical simulations using an improved, two-dimensional version of the Szilder-Lozowski morphogenetic model that predicts the evolution of the accretion shape. The freezing probability, which is the critical model parameter, is expressed as a function of location and atmospheric conditions for an accretion shape evolving with time. Using the morphogenetic model, we examine the influence of atmospheric conditions on the accretion shape and ice load. In particular, we identify the range of atmospheric conditions that tends to maximize or minimize the ice load for a given amount of precipitation.