AI 中文总结
本研究通过颗粒解析直接数值模拟，改变Shields数实现床面形态转变，揭示了可侵蚀床面湍流的非单调调制规律，明确了床面形态演化与湍流调制的直接关联。
AI 中文摘要
可侵蚀床面颗粒流中的湍流调制机制仍是一个未解决的问题。本研究采用颗粒解析直接数值模拟，通过改变Shields数实现了纵向到横向床面形态的转变，揭示了近壁湍流的非单调调制规律。在低Shields数下，流向泥沙脊产生形态诱导条纹，在预乘能谱中形成一个明显的次峰，该峰值超过了传统近壁湍流峰值并增大了湍动能。随着Shields数增大，跃移运动加剧并破坏这些结构，导致流向的次峰消失、展向的次峰减弱，从而抑制湍流。对床面的本征正交分解显示，模态贡献从单一主导模态向高阶模态重新分布，纵向特征作为残余保留下来，直接将床面形态演化与湍流调制关联起来。
英文摘要
The mechanism of turbulence modulation in particle-laden flow over erodible beds remains an open question. Using particle-resolved direct numerical simulations, this study realises a longitudinal-to-transverse bedform transition by varying the Shields number, revealing non-monotonic modulation of near-wall turbulence. At low Shields numbers, streamwise sediment ridges generate form-induced streaks that produce a distinct secondary peak in the premultiplied energy spectra, exceeding the conventional near-wall turbulent peak and enhancing the turbulent kinetic energy. As the Shields number increases, saltation intensifies and disrupts these structures, causing the secondary peak to vanish in the streamwise direction and weaken in the spanwise direction, thereby suppressing turbulence. Proper orthogonal decomposition of the bed surface reveals a redistribution of modal contribution from a single dominant mode to higher-order modes, with longitudinal features persisting as remnants, directly linking bedform evolution to turbulence modulation.
Comments10 pages, 6 figures
