Research On Model Test And Numerical Simulation Of Hydraulic Characteristics In Hydropower Construction Closure

China’s rapid development in hydropower projects has offered a wealth of engineering and theoretical experiences for closure of big rivers. In comparison with physical modeling experiment in river closure, numerical simulation technique has many advantages. Particularly, new ANSYS Workbench development platform provides the compatibility of many modules including fluid and flow field. Based on actual projects, this paper describes a hydropower engineering closure model experiment and then presents an ANSYS-based numerical simulation method for closure gap hydraulic characteristics.The closure model experiment is researched as per actual closure process in accordance with experimental procedures. This paper gives elaboration from model scaling, design, manufacture and calibration to experimental process design, preparation and condition-based results and then makes analysis on such results. It is found out that the difficulty in closure will get bigger with the increase in closure flow and get smaller with the increase in bypass flow and in downstream tailwater level. In the model experiment, the VDMS is implemented to monitor the flow field and surface velocity distribution; the closure controlling parameters are simulated, with a bypass-flow factor’s area integral method presented; statistical analysis is applied to research the relationship between diversion tunnel bypassing capability and the factors including closure gap width, closure flow volume, diversion tunnel entrance bypassing conditions, downstream station water-storage level, and the tunnel flow state.On the basis of the closure experiment, a numerical simulation method is provided for closure river flow and gap hydraulics parameters, and by using ANSYS, an analytical model is established for the water flow with free surface. In this paper, the APDL module is used to set up a geometric model; the ICEM CFD module is used to set up a flow field model; the CFX-Pre module is used to set flow field analytical type, define boundary conditions and to load initial conditions; the CFX-Solver Manager is used to make flow-field analytical calculation; and the CFD-Post module is used to make numerical simulation, detailing the simulation process for river flow field. The simulation post-processing module is capable of giving visual representation of hydraulics elements such as flow velocity and water depth. Around the inlet area, compared with the flow field of smooth walls, the water surface profile is in a lower position and the flow turbulence intensity is weaker.In the numerical simulation of the closure gap hydraulics parameters for hydropower construction, unsteady flow is discretized into steady flow to process. As per upstream and downstream flow parameters (volume, water level, velocity, etc.) in experimental condition I, hydraulics parameters are numerically simulated for the gaps of four different widths. Consequently, by invoking ANSYS Workbench’s post-processing module, isoface and polyline can be used to solve water-surface-profile elevation of stream segments through different-width gaps during the closure; the coordination between isoface and contour can well solve the velocity distribution and size within the scope of gaps; vertical-horizontal sections and horizontal profile cutting methods are adopted to pick up and observe the flow field within the gap scope; especially the isosurface is used to set velocity options, and horizontal plane is used in combination with isoline cloud chart to get different velocity value and observe the positions in the flow field, thereby intuitively representing the velocity distribution in the flow field. At last, by analyzing the influence of different berm widths on gap flow velocity and water surface change, it is found out that a wider dike can better improve the scour of the flow on the dike ends than a narrower dike, meanwhile bringing the increase in gap axis downstream velocity.In the comparison between physical modeling experiment and numerical simulation experiment on the river closure, this paper proves that it is feasible to utilize ANSYS Workbench for the numerical simulation of closure hydraulic characteristics, thus serving as a new idea for that of closure in hydropower construction.