Optimization Study On Hydraulic Characteristics And Shape Of Low Level Operating Tunnel Of Baleh Reservoir In Malaysia

The topography of the Baleh reservoir project in Malaysia is complex and many hydraulics problems arise.During the construction inflow period,the normal operation of the low-level operation cavern affects the whole project.The low-level operation cavern shape has an important influence on the flow pattern of the water in the cavern,and the change of flow pattern will cause the change of hydraulic parameters in the inflow cavern,so the low-level operation cavern shape needs to be studied and optimized.The study of the low-level operation hole is of great importance for the normal operation of the whole Baleh reservoir system.Based on the Baleh hydroelectric project in Malaysia,this paper uses a combination of model tests and numerical simulations to comprehensively analyze the flow patterns,flow velocities,water surface lines,pressures,etc.at different water levels and flows,The main parts of the research results and conclusions of the paper are as follows.(1)A comprehensive description of the theoretical basis of hydraulic structure flood relief cavern research and the current status of research in related fields at home and abroad,including the current research methods of hydraulic characteristics of inflow flood relief caverns,the latest research progress in eliminating cavitation damage in water relief buildings,and the experience that can be drawn from research in related fields at home and abroad.(2)The original low operating hole discharge capacity meets the design requirements,and the pressure at each pressure measurement point conforms to the pressure distribution law,but there is a negative pressure position,and the water cavitation number at the negative pressure position is less than 0.3,which is more likely to produce cavitation cavitation,and the body shape of the gradual change section and the gate chamber section is unreasonable.(3)Based on the analysis of the pivot layout overview and geological and topographical conditions of the Baleh hydroelectric project in Malaysia,the hydraulic model was constructed in conjunction with the preliminary design scheme,with the aim of judging whether the original design scheme could meet the hydraulic characteristics requirements.(4)Aiming at the turbulent flow pattern of open and full flow at the gate in the model test scheme of low level operation tunnel,based on the numerical simulation software Fluent module of Workbench,using RNG k-ε model and VOF method to track the free water surface,three-dimensional numerical simulation was conducted for different gate openings and water levels in the low level operation tunnel,and hydraulic parameters were calculated and analyzed.The results showed that the numerical simulation results were basically consistent with the physical model test results.In view of the adverse flow pattern in the transition section and the gate chamber section in the original scheme,the gate shape was modified.(5)The two-hole planar gate is modified into a single-hole curved gate,and the optimized scheme is numerically simulated,and the hydraulic parameters are analyzed and the results are obtained: the unfavorable flow pattern at the gate is significantly improved,the negative pressure area is reduced,and the possibility of cavitation phenomenon is reduced.This research topic provides a theoretical basis for the design of the reservoir low-level flood cavern of the Baleh hydroelectric project in Malaysia,which effectively ensures the normal construction of the hydroelectric project and the normal operation of the reservoir at a later stage.