径流、潮流耦合作用下大沽河河口悬沙输移扩散数值研究
发布时间：2018-08-14 20:31
【摘要】：河口海岸地区是人类开发海洋资源的前沿地带，与人类生产、生活息息相关。由于河口地区受到径流、潮流等因素的影响，其水沙动力特性非常复杂；对径流、潮流和悬沙等因素的行为特性进行深入分析和探索具有重要的理论研究意义和实践价值。 本文以大沽河口作为研究区域，通过观测数据搜集、整理与分析、数值计算等手段，探讨了大沽河口的径流、潮流耦合作用下的水动力以及泥沙输移扩散行为特性。分析结果发现： （1）当枯期5年一遇、洪水期5年一遇、洪水期50年一遇的洪峰分别作用时，径流量越大，径流影响的区域越大。非恒定径流对河口区域的最大影响范围一般发生在落急时刻附近，上述典型洪水径流影响范围分别为29.65km2、103.22km2、161.66km2，径流最小影响范围一般发生在涨急时刻附近，，影响区域分别为8.2km2、52.4km2、98.8km2。 （2）分析了径流对潮位和潮流速的影响。结果发现:河流近海段和口外海滨段潮位均有明显变化；距离河口越近，潮差变化越小；对低潮位的影响大于高潮位。径流量较大时，河口下游水体运动方向与径流方向基本一致；径流量的大小对河口下游潮流速和流向均会产生一定影响。 （3）恒定径流的悬沙浓度一定时，近海段水体中的悬沙浓度与径流量大致呈正比关系；洪水期50年一遇恒定径流条件下，48小时后悬沙浓度最高可达4.8kg/m3，分布在距离河口4~5倍河宽处；河口下游的冲刷范围与恒定径流作用时间有关，时间越长，海床冲刷范围越大。其中72小时后最大冲刷范围约103.6km2；径流量增加使得河流近口段范围增加，河口段范围下移，形成的淤积范围减小，淤积强度有所增加，且淤积位置逐渐远离河口。 非恒定来水来沙条件下，落急时刻悬沙浓度相对较大，最大可达3.0kg/m3；涨急时刻悬沙浓度相对较小，悬沙浓度变化主要集中在近口段，最大值约为1.5kg/m3。非恒定来水来沙条件下，河口附近均会形成东北-西南走向的冲淤带。跟其它潮流典型时刻相比，落急时刻的潮流速和水力挟沙力相对较大，冲淤范围也相对较大；具体来说：河流近口段的冲刷强度可达0.01m；距离河口4~7倍河宽处平均冲刷强度约为0.01m；距离河口2~4倍河宽处，均会形成淤积带，其平均淤积强度在0.02m以上，最大淤积强度可达0.06m。 研究结果可以为大沽河河口的防洪和岸滩保护等工作提供一定的参考依据。
[Abstract]:Estuarine and coastal areas are the frontier of human exploitation of marine resources, which are closely related to human production and life. Because estuarine area is influenced by runoff and tidal current, its hydro-sediment dynamic characteristics are very complicated, and it has important theoretical research significance and practical value to deeply analyze and explore the behavior characteristics of runoff, tidal current and suspended sediment. Taking the Dagu Estuary as the study area, the hydrodynamic and sediment transport and diffusion behaviors of the Dagu Estuary under the coupling of runoff and tidal current are discussed by means of observation data collection, collation and analysis, numerical calculation and so on. The results are as follows: (1) the larger the runoff is, the greater the runoff is when the Hong Feng of the dry period is once in 5 years, the flood period is once in 5 years and the flooding period is once in 50 years. The maximum influence range of unsteady runoff on estuarine region generally occurs near the precipitous moment. The above typical flood runoff impact range is 29.65km 2103.22km 2161.66km2, and the minimum runoff impact range usually occurs near the rising precipitous time. The effects of runoff on tidal level and tidal current velocity were analyzed. The influence areas were 8.2 km2 ~ (2) ~ (2) ~ 52.4 km ~ (2) ~ (2) ~ (2) ~ (-) ~ (98.8) km ~ (2) ~ (2) respectively. The results show that there are obvious changes in the tidal level in both the offshore section and the offshore section of the river, the closer the river is to the estuary, the smaller the variation of tidal range is, and the effect on the low tide level is greater than that on the high tide level. When the runoff is larger, the direction of water movement is basically the same as the direction of runoff, and the magnitude of runoff has a certain influence on the velocity and direction of tidal current. (3) when the concentration of suspended sediment in constant runoff is fixed, The suspended sediment concentration in the offshore water is approximately proportional to the runoff, and the maximum suspended sediment concentration can reach 4.8 kg / m ~ (3) after 48 hours under the condition of constant runoff in the flood period of 50 years, and is distributed at a distance of 4 times the river width from the estuary. The scour range of the lower reaches of the estuary is related to the action time of the constant runoff, the longer the time is, the larger the scouring range of the seabed is. After 72 hours, the maximum scour range is about 103.6 km ~ 2, and the runoff increases the range of the near mouth of the river, the range of the estuary moves down, the range of the formed silt decreases, the sediment intensity increases, and the deposition position is gradually far away from the estuary. Under the condition of unsteady water and sediment supply, the suspended sediment concentration is relatively large at the precipitous moment, the maximum is 3.0 kg / m ~ (3), and the suspended sediment concentration is relatively small in the rising moment, and the change of suspended sediment concentration is mainly concentrated in the near mouth, the maximum value is about 1.5 kg / m ~ (3). Under the condition of unsteady water and sediment, the erosion and siltation zone of northeast-southwest strike will be formed near the estuary. Compared with other typical tidal currents, the tidal current velocity, hydraulic sediment carrying capacity and scour and siltation range are relatively larger in the falling and precipitous period, specifically, the scour intensity of the near mouth of the river can reach 0.01 m. The average scour intensity is about 0.01m at the river width of 4 ~ 7 times from the estuary and 0.06m at the river width of 2 ~ 4 times of the estuary. The average siltation intensity is more than 0.02m and the maximum siltation intensity can reach 0.06m. The results can provide some references for flood control and beach protection in Dagu River estuary.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV148
[Abstract]:Estuarine and coastal areas are the frontier of human exploitation of marine resources, which are closely related to human production and life. Because estuarine area is influenced by runoff and tidal current, its hydro-sediment dynamic characteristics are very complicated, and it has important theoretical research significance and practical value to deeply analyze and explore the behavior characteristics of runoff, tidal current and suspended sediment. Taking the Dagu Estuary as the study area, the hydrodynamic and sediment transport and diffusion behaviors of the Dagu Estuary under the coupling of runoff and tidal current are discussed by means of observation data collection, collation and analysis, numerical calculation and so on. The results are as follows: (1) the larger the runoff is, the greater the runoff is when the Hong Feng of the dry period is once in 5 years, the flood period is once in 5 years and the flooding period is once in 50 years. The maximum influence range of unsteady runoff on estuarine region generally occurs near the precipitous moment. The above typical flood runoff impact range is 29.65km 2103.22km 2161.66km2, and the minimum runoff impact range usually occurs near the rising precipitous time. The effects of runoff on tidal level and tidal current velocity were analyzed. The influence areas were 8.2 km2 ~ (2) ~ (2) ~ 52.4 km ~ (2) ~ (2) ~ (2) ~ (-) ~ (98.8) km ~ (2) ~ (2) respectively. The results show that there are obvious changes in the tidal level in both the offshore section and the offshore section of the river, the closer the river is to the estuary, the smaller the variation of tidal range is, and the effect on the low tide level is greater than that on the high tide level. When the runoff is larger, the direction of water movement is basically the same as the direction of runoff, and the magnitude of runoff has a certain influence on the velocity and direction of tidal current. (3) when the concentration of suspended sediment in constant runoff is fixed, The suspended sediment concentration in the offshore water is approximately proportional to the runoff, and the maximum suspended sediment concentration can reach 4.8 kg / m ~ (3) after 48 hours under the condition of constant runoff in the flood period of 50 years, and is distributed at a distance of 4 times the river width from the estuary. The scour range of the lower reaches of the estuary is related to the action time of the constant runoff, the longer the time is, the larger the scouring range of the seabed is. After 72 hours, the maximum scour range is about 103.6 km ~ 2, and the runoff increases the range of the near mouth of the river, the range of the estuary moves down, the range of the formed silt decreases, the sediment intensity increases, and the deposition position is gradually far away from the estuary. Under the condition of unsteady water and sediment supply, the suspended sediment concentration is relatively large at the precipitous moment, the maximum is 3.0 kg / m ~ (3), and the suspended sediment concentration is relatively small in the rising moment, and the change of suspended sediment concentration is mainly concentrated in the near mouth, the maximum value is about 1.5 kg / m ~ (3). Under the condition of unsteady water and sediment, the erosion and siltation zone of northeast-southwest strike will be formed near the estuary. Compared with other typical tidal currents, the tidal current velocity, hydraulic sediment carrying capacity and scour and siltation range are relatively larger in the falling and precipitous period, specifically, the scour intensity of the near mouth of the river can reach 0.01 m. The average scour intensity is about 0.01m at the river width of 4 ~ 7 times from the estuary and 0.06m at the river width of 2 ~ 4 times of the estuary. The average siltation intensity is more than 0.02m and the maximum siltation intensity can reach 0.06m. The results can provide some references for flood control and beach protection in Dagu River estuary.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV148
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