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风成浪作用下近底水流流动特性及底泥运动规律研究
Study on the Flow Characteristics on the Boundary Layer and the Sediment Movement Under the Wind Waves
【作者】 马利军；
【导师】 胡旭跃；
【作者基本信息】 长沙理工大学 ， 港口、海岸及近海工程， 2011， 硕士
【摘要】 风浪作用是影响湖区沉积物再悬浮的主要动力因素之一,沉积物再悬浮、输移扩散、沉积,容易造成湖区港口、航道的淤积;改变水体光照度,引起水体二次污染,触发水生生物环境变化等系列反应,对湖区生态系统产生重要影响。采用波浪水槽模拟实测东洞庭湖风浪,对风浪作用下洞庭湖底浮泥再悬浮的水动力学机理进行研究,探求风浪近底水流流动特性,分析浮泥起动扩散过程,给出相应的起动判别条件。研究对于分析洞庭湖区水沙要素时空变换,湖底形态演变预测及环境保护、湖泊整治等均有一定的理论意义和工程参考价值。研究发现,风浪近底水流层内瞬时垂向流速与纵向流速间存在相位差,且相位差随距底距离增加而逐渐加大,与微幅波理论的结果不同;在近底水流层外此相位差恒定为π/2,与微幅波理论一致;采用微幅波理论计算所得有效波最大近底流速与实测最大底流速较为接近,表明可以用微幅波理论近似计算风浪最大近底流速;对比实验观测情况和窦国仁理论计算泥沙起动流速,发现用瞬时最大近底流速描述泥沙起动状况并不合适,需要采用长时间有效流速来代替。经分析,用风浪平均波波要素按微幅波理论计算所得流速值来描述底泥响应情况,与实验观察现象一致,也与窦国仁公式计算值较为接近,实际中可以用此方法来判别泥沙起动情况;悬移质垂线含沙量符合指数分布形式,自床面向上逐渐增大;水体底部存在高浓度含沙层,其上限可由悬沙浓度分布曲线的转折点来定义;结合实验观测数据,建立了高浓度含沙层厚度与各波要素之间的关系,用来计算高浓度层厚度;在已知床面悬沙浓度后,水体悬移质含沙量垂线分布可由高浓度含沙层划分为两部分计算。
【Abstract】 Impact of wind wave induced lake is the main driver of sediment resuspension factor. Sediment resuspension, transport and diffusion, and deposition, likely to cause lake ,port, waterway silting, and even change the illumination of water, causing water biological response to environmental changes , on the lake and ecosystem an important impact .Study found that storm water flow near the end of the instantaneous vertical velocity and vertical velocity between the phase difference and phase difference with increasing distance from the end of the gradual increase, with the result of slightly different wave theory, in the outer layer of water near the bottom of this difference Constant is, same with a slight wave theory; slight wave with significant wave calculated with the measured maximum velocity near the end of the maximum flow rate is closer to the bottom, indicating that a slight wave theory can approximate the maximum near-bottom wave velocity; comparative experimental observation in And Dou theoretical incipient velocity of sediment found near the end with the instantaneous maximum flow rate silt condition described is not appropriate, we need a long time to replace the effective flow rate. After analysis, the average storm wave elements with a slight wave at the flow rate value calculated to describe the response of sediment, was consistent with the experimental concept of investigation, but also with the calculated values closer Dou, in practice this method can be used to determine soil Sha start situation; suspended load sediment vertical exponential distribution form. High concentration of sand at the bottom of the ceiling with suspended sediment concentration profile may be the turning point to define and participate in imitation of the existing formula for calculating the boundary layer thickness of the establishment of high concentrations of sediment thickness and the relationship between the elements of each wave in order to calculate High concentration layer thickness. Known bed suspended sediment concentration, water vertical distribution of suspended sediment concentration of the highest concentrations can be divided to two parts sand with calculated.