稳定床面风沙起动的碰撞耗散机制：CFD-DEM耦合模拟与非均匀粒径响应

Collisional Dissipation Mechanism of Aeolian Sand Entrainment over Stable Beds: CFD-DEM Coupled Simulation and Non-Uniform Particle Size Response

摘要: 风沙起动是风蚀与沙尘输送的核心环节，其细观机制尚不明确。文章基于CFD-DEM双向耦合框架，建立可解析颗粒离散运动、相间动量交换及湍流调制作用的数值模型，系统研究稳定床面单颗粒起动与非均匀床面的粒径选择性起动行为。研究发现，稳定床面单颗粒起动并非传统认知的碰撞溅射主导，而是流体动量累积与碰撞耗散相互竞争的动力学过程；碰撞在此主要扮演耗散角色，颗粒成功起动需跨越由碰撞累积决定的临界能量门槛。非均匀床面模拟进一步揭示粒径对起动概率的非单调调控：细颗粒因深陷孔隙、高频碰撞耗散，起动概率反低于中等颗粒；粗颗粒呈现为碰撞驱动、流体辅助的模式；中等颗粒体现由接触主导向流体主导的过渡。

Abstract: Wind-blown sand initiation is the core link of wind erosion and dust transport, yet its mesoscopic mechanism remains unclear. Based on the CFD-DEM two-way coupling framework, this study establishes a numerical model capable of resolving discrete particle motion, interphase momentum exchange, and turbulence modulation, systematically investigating single-particle initiation on stable bed surfaces and size-selective initiation behaviors on non-uniform beds. The study finds that single-particle initiation on stable beds is not dominated by collisional splashing as traditionally believed, but rather a dynamic process involving competition between fluid momentum accumulation and collisional dissipation; collisions here primarily play a dissipative role, and successful particle initiation requires crossing a critical energy threshold determined by cumulative collisions. Non-uniform bed simulations further reveal the non-monotonic regulation of particle size on initiation probability: fine particles exhibit lower initiation probability than medium-sized particles due to deep pore embedding and high-frequency collisional dissipation; coarse particles demonstrate a collision-driven, fluid-assisted mode; while medium-sized particles represent a transition from contact-dominated to fluid-dominated regimes.