Theoretical and experimental study of ice accretion due to freezing rain on an inclined cylinder

摘要

This paper reports on an investigation of ice formation on a cylinder exposed to freezing rain. Freezing rain icing is characterized by supercooled raindrop impingement, with vertical and horizontal velocity components, water flow over the surface driven by aerodynamic and gravity forces, and freezing or shedding of the surface water. In the first part of the paper, a novel, three-dimensional analytical model of ice growth on a cylinder is derived and the results are discussed. This is followed by a discussion of experimental tests in the NRC Altitude Icing Wind Tunnel. The experiments were constrained to horizontal drop impingement, and we encountered difficulties delivering large drops at low speed to the test section. Hence, the experiments were used primarily to validate the NRC morphogenetic ice accretion model. The morphogenetic model is a discrete element, random walk model that emulates the motion and freezing of individual fluid elements on the accretion surface. After validating the numerical methodology against the wind tunnel experiments, the model was used to simulate ice formation under more realistic and general geometrical configurations and environmental conditions.