Advances in Frazil Ice Evolution Mechanisms and Numerical Modelling in Rivers and Channels in Cold Regions

Frazil ice comprises millimeter-sized ice crystal particles or flocculations in water, and its generation and evolution primarily occur during the initial stage of the river ice process. Meanwhile, ice damage caused by frazil ice is common, so it is crucial to determine its generation and evolution mechanisms to develop a full understanding of the river ice processes, the prediction of ice development, and ice damage prevention. The recent developments in frazil ice research and modeling are summarized in this article. From the perspectives of field measurements and laboratory experiments, the techniques and methods for observing frazil ice are reviewed, including the flow generation, temperature control, and observation techniques necessary for laboratory observations of frazil ice, as well as the challenging observation techniques used for field measurements. Frazil ice's evolution mechanisms (nucleation, thermal growth, secondary nucleation, collisional fragmentation, and flocculation) are affected by water temperature processes. Work on the movement and distribution of frazil ice is also presented. A review of the current numerical models used to assess frazil ice evolution is conducted. Moreover, the open issues and potential future research topics are suggested.