| 杨铁笙,赵明.黏性细颗粒泥沙絮凝发育时空过程的数值模拟[J].水利学报,2015,46(11):1312-1320 |
| 黏性细颗粒泥沙絮凝发育时空过程的数值模拟 |
| Temporal and spatial variations of the flocculation process of fine cohesive sediments:a numerical simulation |
| 投稿时间：2014-11-24 |
| DOI：10.13243/j.cnki.slxb.20141418 |
| 中文关键词: 絮凝 Smoluchowski方程 数值模拟 时空变化 分形 |
| 英文关键词: flocculation processes Smoluchowski equation numerical simulation temporal and spatial variation fractal dimension |
| 基金项目:国家自然科学基金项目(51179087) |
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| 摘要点击次数: 1778 |
| 全文下载次数: 39 |
| 中文摘要: |
| 以Smoluchowski方程为基础,用数值模拟方法研究黏性细颗粒泥沙絮凝-沉降的时空过程。模拟设定泥沙最小基本颗粒粒径5μm,絮团分形维数1.78,模拟高度1.75 m,模拟总时长300 min,初始条件为各级泥沙颗粒-絮团浓度各向均匀分布,入口、出口无泥沙通量。模拟给出泥沙质量浓度、絮团平均粒径、絮团粒径分布等参数的时空变化过程。模拟发现:各个高度上泥沙质量浓度随时间变化的曲线均呈平缓衰减、快速下降与趋零三个阶段,其形状相似;位置越低,曲线的显现时间越滞后。絮团质量加权平均粒径随时间变化过程存在升涨-高峰-衰落三个阶段。碰撞效率系数越大,峰值越高;位置越低,峰现时间越滞后。本文还以泥沙质量浓度随时间变化为例,比较了数值模拟与絮凝试验的测量结果,二者基本一致。 |
| 英文摘要: |
| This paper presents a numerical study on the flocculation and sedimentation process of fine cohesive sediment particles based on the Smoluchowski equation and its extended model. The simulated minimum size of sediment particles is 5.0μm, the floc fractal dimension is 1.78, and the height and diameter of the simulated sedimentation measuring cylinder are 1.75m and 0.14m, respectively. The simulated sedimentation time is 300 min. Initial conditions for this simulation include a uniform distribution of sediment particles and flocs in all directions, and zero sediment flux at the inlet and outlet of the simulated space. Temporal and spatial variations of some key parameters were simulated, including sediment concentration, average size of flocs,and size distribution of flocs. The impact of collision efficiency coefficient on simulated flocculation processes was also investigated. Simulation results show that sediment concentration at any height all decreased monotonically, and the concentration-time curve has three stages, namely, gentle glide, steep drop, and diminishing to zero. For flocs the competition between aggregation growth and sedimentation resulted in an average floc size variation curve which is very similar to an"error function",with its peak indicating the balance point of the two competitive processes. Simulated sediment concentrations at the depth of 1.0m agrees well with measured data. This study also discussed future prospects regarding the application of the Smoluchowski equation on sediment flocculation processes, and revealed some aspects which require further investigation. |
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