Equivalent ice thickness in ship ice transit simulations: overview of existing definitions and proposition of an improved one

ABSTRACT Several definitions of equivalent ice thickness for simplification of complex ice cover are found in the literature. However, their systematic analysis is currently absent. Therefore, this paper reviews different definitions and validates them against a high-fidelity ice transit simulator, determining the most accurate one, with an average error of 16% for one analysed ship, and 10.5% for the other. Furthermore, capability of equivalent ice thickness to predict ship besetting in ice is tested, accurately predicting this event in 88% of the cases. Moreover, sensitivity analysis to the parameters not included in the traditional definitions is conducted, and it is found that only the thickness of ridge consolidated layer has significant impact. Finally, traditional concept based on equivalent ice volume is extended, and a concept of equivalent-performance ice thickness is developed, outperforming the traditional approach by reducing the average error to 4.6% for one ship, and to 3.2% for the other.