相干气流结构对粗颗粒起始风蚀起动的作用
The role of coherent airflow structures on the incipient aeolian entrainment of coarse particles
AI总结：
本文提出基于能量守恒的微观力学模型，结合风洞实验揭示了相干气流扫掠事件对砾石颗粒起始运动的驱动作用，并提出了适用于滚动完全起动的基于功的准则。
摘要：
本文从理论和实验角度研究了能够使砾石大小颗粒发生运动的相干气流结构的作用。具体而言，提出了一种基于能量守恒的微观力学模型，用于描述大颗粒从摇摆（不完全起动）到起始滚动（完全起动）的起始运动。在近阈值气流条件下的空气动力学粗糙床面上进行了风洞实验。分别使用热线风速仪和激光位移传感器同步测量了测试颗粒上风向的气流速度和颗粒位移信号，从而将相干气流结构（通过象限分析提取）与颗粒运动联系起来。研究表明，砾石大小颗粒的起始运动（摇摆和滚动）可能源于具有足够能量的扫掠事件，其对应的空气动力学阻力超过了局部微地形阻力。然而，滚动模式下的完全起动应满足所提出的基于功的准则。此外，使用适当的概率框架，所提出的准则可能适用于描述风到颗粒土壤表面的能量传递过程，涵盖从砾石的蠕移输运到巨型波纹的“机械筛分”，以及轻质人为碎片（如塑料）的输运。
英文摘要：
The role of coherent airflow structures capable of setting gravel-size particles in motion is studied theoretically and experimentally. Specifically, a micromechanical model based on energy conservation is proposed to describe the incipient motion of large particles ranging from rocking (incomplete entrainment) to incipient rolling (full entrainment). Wind tunnel experiments were conducted on an aerodynamically rough bed surface under near-threshold airflow conditions. Synchronous signals of airflow velocities upwind of the test particles and particle displacement are measured using a hot film anemometer and a laser distance sensor, respectively, from which coherent airflow structures (extracted via quadrant analysis) and particle movements are interlinked. It is suggested that the incipient motion of gravel-size particles (rocking and rolling) may result from sufficiently energetic sweep events corresponding to aerodynamic drag forces in excess of the local micro-topography resistance. However, full entrainment in rolling mode should satisfy the presented work-based criterion. Furthermore, using an appropriate probabilistic frame, the proposed criterion may be suitable for describing processes of energy transfer from the wind to the granular soil surface, ranging from the creep transport of gravels to the "mechanical sieving" of mega-ripples, as well as the transport of light anthropogenic debris (such as plastics).
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