Models for thermal boundary layer in level ice growth and brash ice consolidation

Abstract

It is important to understand the properties and parameters of ice growth models, to enable reliable assessment of the impact ice may have on facilities or to ship navigation. To improve the understanding of the different models, the theoretical formulations for ice growth are investigated and calculated results compared with laboratory and full-scale measurement data. The paper describes the ice growth models for level sea ice and how these are applied in brash ice consolidation modelling. In particular, analysis is made to account for modelling of snow cover in level ice growth models, and subsequently also salinity, porosity and the atmospheric boundary including wind effect in brash ice models. The paper presents an overview of laboratory tests and results for both level ice and brash ice. Also models for level ice growth for the case of snow cover are derived and compared with thetest results. Specifically, inclusion of snow thickness in the growth model presents some practical difficulties, as the thickness of snow cover is often not known a priori, and comparison between calculated level ice thickness and measurements suggests that a good assumption in predictive models is to assume the snow cover thickness to be proportional to level ice thickness. Further, it was observed that the wind influences much the heat transfer to atmosphere, which is not zero at the zero wind speed, a value for the heat transfer coefficient to atmosphere is derived based on laboratory tests. The findings from these analyses provide an improved understanding of the ice growth and consolidation process which can be incorporated into modelling techniques for marine design and operations.