Numerical modelling of mixed-sediment consolidation
Numerical modelling of mixed-sediment consolidation
复制标题
DOI：
10.1007/s10236-015-0818-x
复制
发表时间：
2015-04-01
期刊：
影响因子：
2.3
通讯作者：
Bassoullet, Philippe
中科院分区：
文献类型：
--
作者：
Grasso, Florent;Le Hir, Pierre;Bassoullet, Philippe
以粘性和非粘性泥沙混合物为特征的河口环境中的泥沙输运模型，必须考虑固结造成的可蚀性的时间变化。一般来说，通过沉降柱试验验证，泥浆固结模拟效果较好；然而，数值模型仍难以准确模拟大范围初始条件下混合沉积物的沉积和固结过程。这在一定程度上是由于当离析现象不明显时，很难确定砂在阻碍沉降状态下的作用。基于大量的泥沙混合物沉降实验，本研究的目的是通过关注分离过程来改进混合泥沙固结的数值模拟。我们使用了分形理论下的本构关系，并结合了一种基于相对泥浆浓度的新分离公式。使用为每次测试校准的特定参数集（不同的初始泥沙浓度和含沙量），该模型在模拟泥沙高度演变和浓度垂直剖面方面取得了出色的预测能力。它强调了模型的能力，以适当地模拟分离发生的泥砂混合物的特点是广泛的初始条件。然而，标定参数变化显著，分形数在2.64 ~ 2.77之间。这项研究调查了使用一组共同参数的相关性，这通常是三维泥沙输运建模所必需的。模拟不太准确，但在操作方法中仍然令人满意。最后，提出了天然河口环境的具体公式，通过三维输沙模型正确模拟了泥沙混合物的沉积-固结过程。
Sediment transport modelling in estuarine environments, characterised by cohesive and non-cohesive sediment mixtures, has to consider a time variation of erodibility due to consolidation. Generally, validated by settling column experiments, mud consolidation is now fairly well simulated; however, numerical models still have difficulty to simulate accurately the sedimentation and consolidation of mixed sediments for a wide range of initial conditions. This is partly due to the difficulty to formulate the contribution of sand in the hindered settling regime when segregation does not clearly occur. Based on extensive settling experiments with mud-sand mixtures, the objective of this study was to improve the numerical modelling of mixed-sediment consolidation by focusing on segregation processes. We used constitutive relationships following the fractal theory associated with a new segregation formulation based on the relative mud concentration. Using specific sets of parameters calibrated for each test-with different initial sediment concentration and sand content-the model achieved excellent prediction skills for simulating sediment height evolutions and concentration vertical profiles. It highlighted the model capacity to simulate properly the segregation occurrence for mud-sand mixtures characterised by a wide range of initial conditions. Nevertheless, calibration parameters varied significantly, as the fractal number ranged from 2.64 to 2.77. This study investigated the relevance of using a common set of parameters, which is generally required for 3D sediment transport modelling. Simulations were less accurate but remained satisfactory in an operational approach. Finally, a specific formulation for natural estuarine environments was proposed, simulating correctly the sedimentation-consolidation processes of mud-sand mixtures through 3D sediment transport modelling.