Size distribution and shape properties of brash ice in icebreaking channel of level ice

With the expansion of global shipping into polar and icy regions, icebreaking escorts are essential for ensuring efficient cold-region port and waterway operations, and ice resistance evaluation is critical for optimizing escort strategies. However, the existing studies mainly rely on the properties of natural large-size ice floes to create static geometric models of regular-shaped ice, and the brash ice properties are lacking in icebreaking channels after the initial icebreaking of level ice. This oversight neglects variations in ice properties and the dynamic effects of icebreaking speed, and effect the accuracy of brash ice resistance prediction. To address this gap, this study examines the size distribution and shape properties of brash ice in icebreaking channels after initial icebreaking of level ice, based on full scale ship tests in Bohai Bay. Using airborne photography and image segmentation, we analyzed ice characteristics and distribution patterns. Results show that the size distribution of brash ice follows a power-law distribution, with a unimodal probability density function that fits well to a Weibull function. The average size closely matches the Weibull fitting mean. Shape analysis indicates that brash ice roundness exhibits scale invariance relative to caliper diameter. Kendall's Tau correlation analysis and regression analyses identify that there is a significant negative exponential relationship between brash ice size and icebreaking speed, and the ship speed has an impact on level ice fragmentation significantly. This study presents an analytical method for the geometric parameters of brash ice in icebreaking channels and proposes the size distribution and shape property patterns, which can be used for ice resistance prediction and optimization of icebreaking strategies.