Sediment dynamics - Fluid and sediment bed interactions. What roles do fluid infiltration and grain shape play? - 3D numerical flume tank experiments

这一建议的灵感来自于控制沉积物水界面直接附近和沉积物床内部沉积物-流体相互作用的物理参数(例如，流速和颗粒形状)的量化方面的固有局限性。为了研究影响泥沙床侵蚀特性的过程，研究人员通常采用实验室水槽或现场调查的方法对泥沙床的输移特性进行经验测试。然而，在使用这些技术时，很难精确地量化在沉积体的直接附近和内部发生的过程，例如向沉积物床中的流体入渗率。因此，沉积床内部的物理过程需要进一步研究。这项研究的总体目标是通过三维数值模拟，识别和量化流体渗透和颗粒形状变化对沉积物床输运行为的作用，重点关注发生在沉积物床直接附近和内部的物理过程。假设：(1)在天然沉积物床中发现的颗粒形状影响着可渗透到沉积物床中的流量。(2)质地组成(圆形和非圆形)控制着进入沉积物床的流量，从而决定了侵蚀特性；(3)沉积物中的天然颗粒形状影响着沉积物床的侵蚀特性。采用光滑粒子数值流体动力学(SPH)方法，在三维数值水槽中对不同颗粒形状的均匀沙床在不同流速下进行了试验研究。物理特征，如流体流入和颗粒形状变化对输运特性的作用，将在直接附近和沉积物床内部以高分辨率测量。

This proposal was inspired by the inherent limitations in the quantification of the physical parameters (e.g., flow speed and grain shape) controlling sediment-fluid interactions in the direct vicinity of the sediment water interface and in the interior of a sediment bed. For investigation of the processes influencing the erosion characteristics of sediments beds, researchers commonly tested the transport behavior sediment beds empirically using laboratory flume tanks or in situ field investigations. However, a precise quantification of the processes occurring in the direct vicinity and in the interior of the sediment body, such as the fluid infiltration rates into the sediment bed, is difficult when using these techniques. Therefore, the physical processes in the interior of a sediment bed require further investigation. With a focus on the physical processes, occurring in the direct vicinity and in the interior of a sediment bed, the overall goal of this proposed research is to identify and quantify the role of fluid infiltration and grain shape variations on the transport behavior of sediments beds using 3D numerical simulations. It is hypothesized that: (1) the grain shapes found in natural sediment beds effect the amount of flow available to infiltrate into a sediment bed. (2) the textural bed composition (round versus non-round shapes) controls the inflow rates into a sediment bed and, hence, the erosion characteristics, and (3) natural grain shapes in sediment beds influence the erosion characteristics of sediment beds. By the use of the numerical Smooth Particle Hydrodynamics (SPH) method, uniform sediment beds composed of different grain shapes, will be tested in a 3D numerical flume tank under different current velocities. Physical features, such as the role of fluid inflow and grain shape variations on the transport characteristics will be measured at high resolution in the direct vicinity and in the interior of the sediment beds.