风吹雪中雪粒破碎机制的离散元法研究

风吹雪作为重塑积雪时空分布的关键物理过程之一，深刻影响着全球的气候系统、生态演化、水文循环和其他自然过程。风吹雪中雪粒的破碎效应是其区别于一般两相流运动的重要特征之一，对于认识和刻画风吹雪的发展过程和输运特征至关重要，而现有模型几乎均未考虑这一机制。本项目拟对风吹雪中雪粒的破碎机制展开研究，由于雪粒的力学性质对温度和粒径的强烈依赖性，且雪粒的碰撞破坏模式与碰撞方位直接相关，本项目首先基于雪粒的力学特性构建雪粒的温度和粒径依赖本构关系，进而二次开发能够表征雪粒力学特性的离散单元接触模型；接着针对雪粒这种易碎材料设计一种非接触式冲击实验平台，开展雪粒的碰撞破碎实验并验证离散单元模型的有效性；最后，基于各种工况下雪粒碰撞过程的离散单元仿真，揭示雪粒碰撞破碎的微观机理和破碎特征，并进一步探索其对风吹雪运动的影响规律。本研究结果可为变参数材料的破坏模式和机理分析提供指导。

As one of the key physical process that reshapes the temporal and spatial distribution of snow cover, drifting snow profoundly affects the global climate system, ecosystem evolution, hydrology cycle and other natural processes. The fracture mechanism of snow particles is an important feature that distinguishes the drifting snow from common two-phase flow movement, which is also critical for the description of development sprocess and transportation features of drifting snow. However, current models mostly neglect this mechanism. This research will perform a study of the fracture mechanism in drifting snow. Due to the strongly dependences of the mechanical properties of ice on the temperature and particle size, and the failure mode of snow particles is directly related to the collision bearing. Firstly, we will construct the temperature and particle size dependent constitutive relation of snow particle based on its mechanical properties, and further secondary develops the discrete element contact model that can characterize the mechanical properties of snow particle exactly. Then, we will design a non-contact impacting experimental platform for snow particle considering its friable feature, with which we can perform the impact and fracture tests and compare the experimental data with the simulation results to validate the discrete element model. Finally, based on the discrete element simulations of the impact and fracture processes of snow particles under various conditions, we will further reveal the micro fracture mechanism and fracture features of snow particles, and further explores its effect on drifting snow movement. The results can provide guidance for the failure mode and mechanism analysis of variable parameter materials.