Radial spreading of oil under and over broken ice: an experimental study

Abstract

The mechanism of oil spreading in the presence of solid ice covers had been investigated in several studies. There are good laboratory data and some field data available for the case of solid ice covers. There are, however, little data available on the subject of oil spreading in the presence of broken ice covers. The lack of data and the complexity of dealing with many different types of broken ice covers are the main reasons for the poor understanding of the oil spreading mechanism in broken ice covers. In this paper, a laboratory study is presented to investigate the behaviour of oil spreading when spilled under a broken ice cover. The experiments included different ice cover thicknesses, artificial and real ice, oils of different viscosities, and a variety of discharge and volume conditions.Laboratory observations indicate that the behaviour of oil spilled under a fragmented ice cover depends on the type of ice cover. While oil may penetrate completely through one type of cover, it may not penetrate at all in another type. In covers that allow the oil to penetrate through, initially oil spreads under the ice, with simultaneous migration through the ice cover. When the oil reaches the water surface, it starts to spread rapidly, outpacing the spreading underneath. The spreading of oil under the ice was dominated by the buoyancy and viscous forces, while oil spreading on the water surface near the top of the ice cover was dominated by interfacial and viscous forces. This paper advances the fundamental understanding of the mechanism. The data from this study can be used to develop future mathematical models on this subject. Key words: oil spreading, oil slicks, oil under ice, constant discharge, constant volume, brash ice.