Contribution to the modelling of the ice accretion process: ice density variation with the impacted surface angle

Abstract

Icing measurements were carried out in natural winter clouds with an instrumented wind tunnel set up at the summit of Puy de Dome (1 500 m a.s.l.). The microphysical data (liquid water content, droplet spectra) were obtained by using the particle measuring system PMS ASSP 100. The ice density was measured on a rotating cylinder and the ice deposit of the cross-section was photographed on a fixed cylinder. The density measurements ranged from 300 to 900 kg m–3 during the experioment and are in agreement with Macklin’s results (1962). The profile of the ice deposit is comparedto the profile predicted by the model of Lozowski and others (19791, which considers a fixed density.We propose to improve this model by talking into account the variation of ice density with the angle of impact on the cylinder. This calculation is based on Macklin’s results and on the determination of the local impact speed by using the result of Langrature, air speed, liquid wter content, and, especially, the droplet distribution. The improvement is not sufficiemuir and Blodgett (1960). The variation o fice density with the angle depends on various parameters: pressure, tempen to explain some observed profiles; this may be attributed to the fact that the model is not time-dependent.