Title: Preliminary experimental investigation on the interaction of a subaqueous dune like granular structure with a turbulent open channel flow Show Chinese title

Title: 水下沙丘状颗粒结构与湍流明渠流的初步实验研究

Abstract: We study the interaction of a subaqueous dune like granular structure with a turbulent open channel flow experimentally using optical diagnostics in the Shields and Froude parameter space ($0.05{\leq}{\theta}{\leq}0.32$, $0.1{\leq}Fr{\leq}0.4$). Interactions between the turbulent flow and the granular structure give rise to transient erosion-deposition dynamics leading to various types of particle transport. The subaqueous structures in the channel bed evolves due to shear-stress-induced erosion, gravity-driven deposition, and subsequent particle transport. We study the centroid motion and the granular structure shape evolution. At lower end of our ${\theta}-Fr$ parameter space, we observe no erosion and the structure remains at rest. We show that the critical Shields number (${\theta}_{cr}$) is of the order of $0.1$ beyond which erosion starts to occur. At intermediate values of ${\theta}$ and $Fr$ we observe slow erosion, resulting in a rigid body motion of the granular structure without significant shape deformation. Higher values of ${\theta}$ and $Fr$ causes vortex formation at the upstream of the dune resulting in stronger erosion, rapid shape deformation and relatively higher translation velocity of the centroid. Show Chinese abstract

Abstract: 我们通过光学诊断方法在Shields和Froude参数空间（$0.05{\leq}{\theta}{\leq}0.32$，$0.1{\leq}Fr{\leq}0.4$）中实验研究了水下沙丘状颗粒结构与湍流明渠流的相互作用。湍流与颗粒结构之间的相互作用导致瞬时侵蚀-沉积动力学，从而引发各种类型的颗粒输运。由于剪切应力引起的侵蚀、重力驱动的沉积以及随后的颗粒输运，渠道床中的水下结构发生变化。我们研究了质心运动和颗粒结构形状的演变。在我们${\theta}-Fr$参数空间的较低端，我们观察到没有侵蚀，结构保持静止。我们表明临界Shields数（${\theta}_{cr}$）约为$0.1$，超过该值后开始发生侵蚀。在${\theta}$和$Fr$的中间值处，我们观察到缓慢的侵蚀，导致颗粒结构发生刚体运动而没有显著的形状变形。 ${\theta}$和$Fr$的较高值会在沙丘上游形成涡旋，导致更强的侵蚀、快速的形状变形以及质心相对较高的迁移速度。