正态曲面丁坝附近三维水流及局部冲刷

发布时间：2019-01-07 20:41

【摘要】：丁坝是一种普通的水工结构,被广泛的应用于河岸防护与河口治理工程中。它可以改变河道水流结构,冲深河床,同时也能削弱近岸水流从而使堤岸不受冲刷。但由于丁坝周围流动呈强三维紊流特征,相应坝头局部床面不可避免地会产生冲刷坑,严重时将导致丁坝水毁。本文提出了一种新型的丁坝结构,即正态曲面丁坝,旨在保证河岸防护效果的前提下,以构造的整体流线型曲面来改善丁坝附近水流结构,进而减少坝头局部冲刷。采用Matlab与Pro/E混合建模的方法,构建了可模拟曲面丁坝附近水流及局部冲刷的三维模型。通过数值模拟的方法对梯形丁坝和曲面丁坝附近三维水流进行了研究,得到了两种丁坝周围的流场、湍动能、河床切应力与涡量强度分布。曲面丁坝因其流线型的正态曲面设计,能较好地改善坝体附近的水流结构,中截面上最大流速相对梯形丁坝减小了12%,大流速区域减小了近80%,湍动能和湍动能耗散率分别为梯形丁坝的1/5和2/3。而曲面丁坝近底面处涡量强度为13S-1,仅为梯形丁坝的60%。在Fluent下自编UDF程序对梯形丁坝和曲面丁坝附近局部冲刷进行动网格模拟,并用Flow-3d的sediment scour模块进行了相应数值模拟,得到了两种丁坝结构下局部冲刷坑最大深度。发现在相同流量条件下,最大冲深在曲面丁坝附近比在梯形丁坝附近减少了约20%,且冲刷坑范围也有减小。结果表明,曲面丁坝新型的结构设计,能够平顺水流,并在一定程度上避免了水体直冲床面,因而对减少局部冲刷有着非常明显的效果,对河岸防护和河口治理具有重要的应用价值。根据梯形丁坝和曲面丁坝周围局部冲刷的数模结果,对冲刷完成之后两种丁坝附近的紊流状态作了分析。冲刷坑形成后,坝体周围水流主要存在四种流动状态。冲刷坑内水流受床面和丁坝的阻挡,会形成大小不一的三维漩涡和环流,因此冲刷坑内将产生比较大的湍动能与涡量强度,相比之下曲面丁坝较梯形丁坝情形下的湍动能与涡量强度要小。
[Abstract]:Spur dike is a kind of common hydraulic structure, which is widely used in river bank protection and estuary regulation. It can change the structure of river flow, wash deep river bed, but also weaken the nearshore flow, so that the embankment can not be scoured. However, due to the strong three-dimensional turbulent characteristics of the flow around the spur dike, the local bed surface of the corresponding dam head will inevitably produce scour pits, which will lead to the water destruction of the spur dike if serious. In this paper, a new type of spur dike structure, the normal curved spur dike, is proposed, which aims at improving the flow structure near the spur dike with the integral streamlined curved surface on the premise of ensuring the riverbank protection effect, and then reducing the local scour of the dam head. Using the method of mixed modeling of Matlab and Pro/E, a 3D model for simulating the flow and local scour around the spur dike is constructed. The three-dimensional flow around trapezoidal spur dike and curved spur dike is studied by numerical simulation. The distributions of flow field, turbulent kinetic energy, river bed shear stress and vorticity intensity around the two kinds of spur dikes are obtained. Due to its streamlined normal surface design, curved spur dike can improve the flow structure near the dam body, and the maximum velocity of flow in the middle section decreases by 12 parts relative to the trapezoidal spur dike, and the area of large velocity decreases by nearly 80%. The dissipation rates of turbulent kinetic energy and turbulent kinetic energy are 1 / 5 and 2 / 3 of trapezoidal groin, respectively. The vorticity intensity near the bottom of curved spur dike is 13S-1, which is only 60 times that of trapezoidal spur dike. The local scour around trapezoidal spur dike and curved spur dike is simulated by UDF program under Fluent. The corresponding numerical simulation is carried out with sediment scour module of Flow-3d, and the maximum depth of local scour pit under two kinds of spur structures is obtained. It is found that under the same flow rate, the maximum impact depth near the curved spur dike is about 20% less than that near the trapezoidal spur dike, and the scour pit area is also reduced. The results show that the new structure design of curved spur dike can smooth the flow of water, and to some extent avoid the surface of the water body directly punching, so it has a very obvious effect on reducing local scour. It has important application value for river bank protection and estuary regulation. Based on the numerical model results of local scour around trapezoidal spur dike and curved spur dike, the turbulent state near the two groins after scouring is analyzed. After the formation of the scour pit, there are mainly four flow states around the dam body. The flow of water in the scour pit will be blocked by the bed surface and the spur bar, which will form three-dimensional whirlpools and circulations of different sizes. Therefore, there will be relatively large turbulent kinetic energy and vorticity intensity in the scour pit. In contrast, the turbulent kinetic energy and vorticity intensity of curved spur are smaller than those of trapezoidal spur.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TV863;TV135

【相似文献】