含能流动结构在风成输运沉积物与塑料碎屑中的作用
The role of energetic flow structures on the aeolian transport of sediment and plastic debris
AI总结：
本研究将能量准则从明渠流拓展到低活动性风成输运，通过风洞实验关联含能流动事件与颗粒摇晃、滚动起动，揭示两者具有不同能量阈值，并提出基于事件的理论框架，为模拟粗颗粒间歇蠕移输运和风成床面形态提供新方法。
摘要：
近年来，在概念上描述粗颗粒起动动力学方面已取得显著进展，并已在明渠流中通过实验进行了探索。本研究旨在将能量准则推广到低活动性风成固体输运（包括天然沉积物和塑料等人为碎屑），涵盖从不完全起动（摇晃）到完全起动（滚动）的过程。实现方法是将颗粒运动与含能流动事件联系起来，这些事件被定义为能够对颗粒做功并使其运动的流动结构。研究假设此类事件应向颗粒传递足够的能量，且超过某一阈值。通过风洞实验和激光距离传感器（LDS）捕捉置于粗糙床面上的单个目标颗粒的动力学，验证了该概念的有效性。测量以高时空分辨率获取，并与目标颗粒上风向适当距离处的瞬时风速同步采集，风速由热膜风速计测量。这使得流动事件能够与摇晃和滚动起动关联起来。此外，研究表明摇晃和滚动可能具有不同的能量阈值。对能量传递效率的估计（以阻力系数归一化）跨越一个数量级（摇晃约为0.001至0.0048，初始滚动最高约为0.01）。所提出的基于事件的理论框架是表征风传递给地表能量的一种新方法，并可能对模拟粗颗粒间歇蠕移输运及相关风成床面形态具有潜在意义。
英文摘要：
Recently, significant progress has been made in conceptually describing the dynamic aspects of coarse particle entrainment, which has been explored experimentally for open channel flows. The aim of this study is to extend the application of energy criterion to the low mobility aeolian transport of solids (including both natural sediment and anthropogenic debris such as plastics), ranging from incomplete (rocking) to full (rolling) entrainments. This is achieved by linking particle movements to energetic flow events, which are defined as flow structures with the ability to work on particles, setting them into motion. It is hypothesized that such events should impart sufficient energy to the particles, above a certain threshold value. The concept's validity is demonstrated experimentally, using a wind tunnel and laser distance sensor (LDS) to capture the dynamics of an individual target particle, exposed on a rough bed surface. Measurements are acquired at a high spatiotemporal resolution, and synchronously with the instantaneous air velocity at an appropriate distance upwind of the target particle, using a hot film anemometer. This enables the association of flow events with rocking and rolling entrainments. Furthermore, it is shown that rocking and rolling may have distinct energy thresholds. Estimates of the energy transfer efficiency, normalized by the drag coefficient, range over an order of magnitude (from about 0.001 to 0.0048 for rocking, up to about 0.01, for incipient rolling). The proposed event-based theoretical framework is a novel approach to characterizing the energy imparted from the wind to the soil surface and could have potential implications for modelling intermittent creep transport of coarse particles and related aeolian bedforms.
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