外文翻译--使用cfd模型分析规模和粗糙度对反弧泄洪洞的影响(编辑修改稿)

外文翻译--使用cfd模型分析规模和粗糙度对反弧泄洪洞的影响(编辑修改稿)内容摘要：

it cannot be used for the final determination of the design, is valuable for obtaining a guide to correct details because putational cost is low relative to physical modeling. In the past few years, several researchers have attempted to solve the flow over spillway with a variety of mathematical models and putational methods. The main difficulty of the problem is the flow transition from subcritical to supercritical flow. In addition, the discharge is unknown and must be solved as part of the solution. This is especially critical when the velocity head upstream from the spillway is a significant part of the total upstream head. An early attempt of modeling spillway flow have used potential flow theory and mapping into the plex potential plane (Cassidy, 1965). A better convergence of Cassidy’s solution was obtained by Ikegawa and Washizu (1973), Betts (1979), and Li et al. (1989) using linear finite elements and the variation principle. They were able to produce answers for the free surface and crest pressures and found agreement with experimental data. Guo et al. (1998) expanded on the potential flow theory by applying the analytical functional boundary value theory with the substitution of variables to derive nonsingular boundary integral equations. This method was applied successfully to spillways with a free drop. Assy (2020) used a stream function to analyze the irrotational flow over spillway crests. The approach is based on the finite difference method with a new representation of Neumann’s problem on boundary points, and it gives positive results. The results are in agreement with those obtained by way of experiments. Unami et al. (1999) developed a numerical model using the finite element and finitevolume methods for the resolution of two dimensional free surface flow equations including air entrainment and applied it to the calculation of the flow in a spillway. The results prove that the model is valid as a primary analysis tool for the hydraulic design of 8 spillways. Song and Zhou (1999) developed a numerical model that may beapplied to analyze the 3D flow pattern of the tunnel or chute spillways, particularly the inlet geometry effect on flow condition. Olsen and Kjellesvig (1988) included viscous effects by numerically solving the Reynoldsaveraged NavierStokes (RANS) equations, using the standardequations to model turbulence. They showed excellent agreement for water surfaces and discharge coefficients. Recently, investigations of flow over ogeespillways were carried out using a mercially available putational fluid dynamics program, FLOW3D, which solves the RANS equations (Ho et al., 2020。 Kim, 2020。 Savage et al., 2020). They showed that there is reasonably good agreement between the physical and numerical models for both pressures and discharges. Especially, Kim (2020) investigated the scale effects of the physical model by using FLOW3D. The results of numerical simulation on the series of scale models showed different flow discharges. Discharge and velocity of larger scale models has shown larger value than the smaller scale models. Existing studies using CFD model mostly deal with the model’s applicability to discharge flowrate, water surfaces, and crest pressures on the spillway. In this study, flow characteristics such as flowrate, water surfaces, crest pressures on the spillway, and vertical distributions of velocity and pressure in consideration of model scale and surface roughness effects are investigated in detail by using mercial CFD model, FLOW3D, which is widely verified and used in the field of spillway flow analysis. The objective of this study is to investigate quantitatively the scale and roughness effects on the flow characteristics by anal。