带异形块体海堤越浪的数值模拟

该文在FLUENT软件平台上,发展了数值消波-造波技术,通过在动量方程里添加多孔介质源项,建立了带有多孔介质模型的二维数值波浪水槽。应用该数值波浪水槽,数值模拟了在斜坡堤坡面上铺设异形块体情况下的越浪过程,给出了越浪量。为了率定异形块体的等效惯性阻力系数,进行了典型工况的物理模型实验,给出了在斜坡堤坡面上不同位置处铺设一层异形块体情况下多孔介质模型的等效阻力系数。     

COMPARISON OF SCOURS IN FRONT OF VERTICAL BREAKWATERS DUE TO REGULAR AND IRREGULAR WAVES

1 .　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｓｃｏｕｒｓｏｆｓａｎｄｂｅｄｉｎｆｒｏｎｔｏｆｖｅｒｔｉｃａｌｂｒｅａｋｗａｔｅｒｓｕｎｄｅｒｔｈｅａｃｔｉｏｎｏｆｒｅｇｕｌａｒｓｔａｎｄ ｉｎｇｗａｖｅｓｗｅｒｅｉｎｖｅｓｔｉｇａｔｅｄａｎｄｓｏｍｅｇｏｏｄｒｅｓｕｌｔｓｗｅｒｅｏｂｔａｉｎｅｄ ,ｉｎｃｌｕｄｉｎｇｓｃｏｕｒｉｎｇｐａｔ ｔｅｒｎｓ ,ｓｃｏｕｒｉｎｇｍｅｃｈａｎｉｓｍｓ ,ｃｒｉｔｅｒｉａｆｏｒｄｉｓｔｉｎｇｕｉｓｈｉｎｇｓｃｏｕｒｉｎｇ ｐａｔｔｅｒｎｓ ,ｐｒｅｄｉｃｔｉｏｎｏｆｓｃｏｕｒｉ…     

3-D NUMERICAL SIMULATION OF CONVOY-GENERATED WAVES IN A RESTRICTED WATERWAY

We consider waves generated by the passing of convoys in a restricted waterway. The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy, such as the speed and the hull geometry. The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown. Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k model for turbulent processes. The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rh ne (CNR).     

2-D NUMERICAL SIMULATION OF RADIONUCLIDE TRANSPORT IN THE LOWER YANGTZE RIVER

The assessment of the radiological impact of the liquid discharges from nuclear power plants is a major issue for the environmental protection. In this study, a numerical model for the radionuclide transport in the aquatic environment is built, based on the hydrodynamic equations, including the complete set of Saint-Venant equations, the sediment transport equations, with consideration of several different particle sizes and the deposition and erosion of the suspended sediments, and the radionuclide transport equations. The exchanges of radionuclides between water, suspended matter and bed sediments are described in terms of kinetic transfer coefficients. The model is used to simulate the transport of the radionuclides discharged from a planned nuclear power plant project to be sited along the lower Yangtze River. From the model results, one may see the detailed temporal-spatial evolution of the radionuclide contamination in the solution, in the suspended matter and in the bed sediments. The model can be used as a basic tool for studying the environmental impacts of the liquid discharges from nuclear facilities on a river system.     

THEORETICAL ANALYSIS AND NUMERICAL SIMULATION OF TURBULENT FLOW AROUND SAND WAVES AND SAND BARS

Natural rivers usually possess sand waves and sand bars. In this article, the rapid distortion theory was used to study the turbulent flow over sand waves. The results show that the pre-existing shearing motion and upstream anisotropy of the turbulence flow would have significant effect on the turbulent structures, and hence the memory effect should be taken into consideration. Furthermore, the 2-D mathematical model was employed to simulate the unsteady flow around the Taiping Sand Bar in the lower reach of the Yangtze River and the time step effect on the unsteady flow simulation with the implicit scheme was discussed at the same time. The results show that the implicit scheme keeps effective until the time step reaches a certain number, and the calculated water levels and velocities are in agreement with the observed data.     

2-D NUMERICAL SIMULATION OF CRUSH BEDROCK RIVER

In this paper, the erosion-resisting coefficient was introduced to compute bed deformation in a crush bedrock river. In the case of crush bedrock, there has been no proper control equation to describe bed stability, which leads to difficulty in calculation of the bed deformation with conventional methods. The data from field survey were used to give the erosion-resisting capability with an appropriate coefficient. After the determination of longitudinal distribution expressed by polynomial regression and transversal distribution expressed by normal distribution function, the plane distribution of erosion-resisting coefficient in a crush bedrock river was obtained. With the computational results from a 2-D horizontal flow mathematical model, the erosion-resisting coefficient and controlling condition of local stability were employed to compute the values of bed deformation when riverbed is stable.The above method was applied in a case study, and the computational results of flow and bed deformations are in good agreement with physical model test data.     

NUMERICAL SIMULATION OF TURBULENT FLOW CHARACTERISTICS IN A CURVED PIPE WITH A BAFFLE

A numerical study on the characteristics of developing turbulent flow in a curved pipe with a baffle was carried out in body-fitted coordinates with the k-ε model turbulence. A curved duct of square cross-section was examined first, and the results agree very well with the experimental data. Then two kinds of pipes, a normal curved pipe and that with a baffle were studied. The computational results are presented and compared with each other to illustrate the changes of the flow after adding the baffle. The longitudinal velocity in the pipe with a baffle was characterized by outer velocity bigger than the inner one. The secondary flow was characterized by four-vortex structure with the intensity reduced, which results in the equability of the flow field of the cross-section compared with that without a baffle, and has much more significant meaning in engineering.