流作用下泥沙悬浮释放污染物的数值分析

基于一维垂向模型(1DV模型),建立了波流共同作用下泥沙悬浮释放污染物的数学模型,模型通过验证可较好的描述床面附近紊动特性、水流结构、泥沙垂向分布及污染物解吸释放规律. 利用数学模型,通过设置不同的模拟情景,分析计算了波流共同作用下泥沙悬浮特征、污染物释放动态过程及时空分布特征. 研究表明: 波流共同作用下,吸附态污染物及总污染物垂向分布与悬浮泥沙分布一致,波浪底部边界层的周期性振荡限制了从底部悬扬的泥沙向上部水体的扩散,在近床面存在梯度较大的高浓度层,在悬浮释放的初期,溶解态污染物的垂向分布规律与吸附态污染物一致,达到平衡后,沿垂向均匀分布.水流流速和波浪强度对泥沙悬浮释放污染物有着不同程度的影响,水流对泥沙及污染物的垂向分布影响明显,波浪的影响主要体现在床面附近形成高浓度含沙层和污染物层.

Numerical analysis of sediment suspension and contaminant release under the action of waves and currents

A 1DV model (one-dimensional vertical model) is built in this paper to simulate sediment suspension and its effects on contaminant release under the combined action of waves and currents. The ability of the model to describe near bed turbulence characteristics, vertical current structure, suspended sediment transport and contaminant release is validated. The model is used to analyze the dynamic process and temporal/spatial characteristics of contaminant release from suspended sediment under the combined action of waves and currents in different scenarios. Numerical results suggest that vertical distribution of adsorbed contaminants and total contaminants are similar as that of suspended sediments, the periodic oscillation of the wave benthic boundary layer limit the diffusion of the suspended sediment from the bottom to the upper water body, a high concentration layer of sediment and adsorbed contaminants near bed with a steep gradient and small thickness would be formed under the combined action of waves and currents. Analysis results of the evolution of contaminants suggest that vertical distribution of the dissolved contaminants is consistent with adsorbed contaminants during the initial stage and then form a uniform vertical distribution when the contaminant release reached equilibrium. Simulations reveal that flow velocity and wave intensity have different degrees of effects on sediment suspension and contaminant release: water flow has significant impacts on vertical distribution of sediment and contaminant, while wave action plays an important role in the formation of high concentration layer of sediment and contaminant near bed.