| Summary: | 碩士 === 逢甲大學 === 水利工程與資源保育學系 === 101 === Socio-economic development in Taiwan has resulted in concentrated land development and utilization and population. In particular, the low-lying areas surrounding the rivers in Western Taiwan present increased land development and utilization. However, extreme climate changes have resulted in increasingly heavy rainfalls. The operating efficiencies of pumping stations are directly influenced by the boundary condition scales of pumping wells. Because of regional differences, the forms of pumping units, that is, the structural materials of water inlet and outlet openings and placement conditions, vary. Because of significant variations of the water levels that these pumps operate in, the operating efficiencies and manipulation conditions of pumping stations are extremely difficult to master. Therefore, understanding and controlling the influence mechanism of pumping well boundary scales on flow fields is beneficial for enhancing the operating efficiencies of pumping stations. The most essential factors influencing the operation efficiencies of pumping stations are the boundary conditions of pumping wells: width, vacant height, submergence depth, and distance between the posterior walls of the pumping wells. Numerical simulations and tests were conducted to explore the influences the pumping well conditions have on the operation functions of pumping stations as well as operating efficiencies.
Using the rectangular posterior wall form, physical models were employed to test and investigate vacant height, submergence depth, and bell diameter, and to evaluate flow stability in pumping wells. Furthermore, the flow velocity distribution, surface vortices, rotation angles, and speed-weighted average angles were used for measurement. Under these boundary conditions, the optimal efficiency was achieved. Subsequently, ANSYS CFX 13.0, which is a computation fluid dynamics software program, was used as the development tool for model construction under steady-state and incompressible flow conditions. The boundaries for the water body were set as free-slip, whereas the remaining boundary conditions were set as no-slip. A homogeneous model was employed and the equations were set asκ-Epsilon equations. Continuity equations, the momentum equation, and standardκ-ε models were used as the control equations.
The results were used to evaluate the flow stability of the simulated pumping wells and the extent to which the operating efficiencies of the pumping stations were influenced. Vorticity maps, flow-line charts, and the physical model test were compared. The results showed that the optimal boundary conditions for the rectangular posterior wall form were a vacant height of C = 0.9 D, a submergence depth of hs = 1.7 D, and a bell diameter of D = 19 cm. The optimal boundary conditions comprised a vacant height of C = 0.9 D, a submergence depth of hs = 1.7 D, and a bell diameter of D = 19 cm. Under these boundary conditions, the optimal efficiency was achieved. Subsequently, the posterior wall form was changed into the double volute form, which was compared with the rectangular posterior wall form. The results showed that the optimal boundary condition for the double-volute posterior wall form was Dc = 20 cm. These optimal boundary conditions can serve as references for future onsite pumping well construction projects.
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