Dynamic Characteristics of Irregular Ice Floes Based on Polyhedral Discrete Element Method

In polar regions, floating ice exhibits distinct characteristics across a range of spatial scales. It is well recognized that the irregular geometry of these ice formations markedly influences their dynamic behavior. This study introduces a polyhedral Discrete Element Method (DEM) tailored for polar ice, incorporating the Gilbert-Johnson-Keerthi (GJK) and Expanding Polytope Algorithm (EPA) for contact detection. This approach facilitates the simulation of the drift and collision processes of floating ice, effectively capturing its freezing and fragmentation. Subsequently, the stability and reli ability of this model are validated by uniaxial compression on level ice fields, focusing specifically on the influence of compression strength on deformation resistance. Additionally, clusters of ice floes nav igating through narrow channels are simulated. These studies have qualitatively assessed the effects of Floe Size Distribution (FSD), initial concentration, and circularity on their flow dynamics. The higher power-law exponent values in the FSD, increased circularity, and decreased concentration are each as sociated with accelerated flow in ice floe fields. The simulation results distinctly demonstrate the con siderable impact of sea ice geometry on the movement of clusters, offering valuable insights into the complexities of polar ice dynamics.

Performance of a novel vertical-flow settler: a comparative study

By increasing particle concentration and G value （root-mean-square velocity gradient） to enhance flocculation, a novel vertical-flow settler was designed to increase sedimentation effectiveness, and to simultaneously improve operational stabilization. Due to the gradual decrease in upward flow-rate of raw water, a floes blanket would form and suspend in the middle section of the settler, not at the bottom as in a conventional clarifier. Enough large floes, resulted from flocculation or fltration, would continuously settle out of the floes blanket, and simultaneously, the floes in raw water or those forming above the blanket would ceaselessly enter the floes blanket. As a result, the floes concentration in the blanket could keep a dynamic balance. The hydrodynamic shear in the blanket was improved by flow separation, which was induced by the abrupt change in flow channel. Due to the floes blanket and improved hydrodynamic shear, flocculation would be enhanced, which was helpful for removing fine particles in raw water. A comparative study showed that the novel vertical-flow settler had a much better performance in the removal of the particles in raw water than a conventional one, when they treated kaolin suspensions of different concentrations （500, 100 and 50 mg/L, respectively） coagulated by polyaluminum chloride（PAC1） at the up-flow rates of 1 and 2 mm/s, respectively.

Thermohaline structure inhomogeneity associated with polynia at the northern margin of Emery Ice-shelf

Based on the hydrographic data in austral summer during the 22nd Antarctic Expedition of China(2005/2006),some features can be found about the northern margin of Emery ice shelf as follows.The heat content in the surface layer(0-50 m) at the eastern end and the western end of the ice-shelf margin is much higher than that at the middle.The upper mixing-layer depth and the seasonal thermocline depth at the middle of the ice-shelf northern margin are much shallower than those at the both ends.However there is much less difference between the middle and the ends in the bottom layer.The remote sensing photos show that the inhomogeneity in the surface-layer water is closely related to the spatial distribution of the floes and polynia in the area.

Experimental Investigation on Breakup of Ice Floe on Waves

Experimental investigation of ice flee breakup on waves by use of non-refrigerated breakable materials has been carried out. The incident wave heights for breakup of ice flee with different lengths, and the influence of rigidity on reflection and transmission coefficients are discussed. The experimental results show that the ratio of the ice noe length, L-i, to the wavelength, L, is one of the significant factor affecting the minimum wave height to cause fracture of ice flee, and another key factor is the ratio of the ice flee thickness, h(i) and L-i.

A CFD study on the hydrodynamic response of a small-scale ice floe induced by a passing ship

A Reynolds averaged Navier-Stokes(RANS)computational fluid dynamics(CFD)model is built to investigate the hydrodynamic response of a circular ice floe under the influence of a passing ship in calm waters.The ship,mirroring the KRISO Container Ship’s hull design,progresses near an ice floe whose diameter is 30%of the ship’s length and its thickness is 3 m.The ship advances at a constant speed,which is handled by using the overset mesh technique.This study focuses on the ice floe’s motions and the hydrodynamic forces induced by three speeds and three transverse distances of the passing ship.Findings reveal that ship-generated wakes notably influence the ice floe’s motions,with a greater influence on sway than surge.Additionally,the ship’s speed and proximity distinctly affect the ice floe’s motions.