摘要
泵站前池中存在复杂的水沙两相流结构,开机组合方式对水流流态与悬移质泥沙运动规律的影响尚不明确。针对该问题,该研究采用Mixture多相流理论和Realizable k-ε紊流模型,模拟不同开机组合条件下的泵站前池水沙运动,分析前池内各个漩涡流区域特征及其形成机理,预测泥沙淤积范围,同时利用多普勒流速剖面仪(acoustic doppler current profilers)等仪器对前池内流速与泥沙淤积进行测量,验证数值模拟结果。在此基础上,分析了典型正向前池泵站5组不同开机组合下的两相流流态,结果表明:前池内漩涡区域致使悬移质泥沙向正向前池边壁区域运移,漩涡流速下沉加速悬移质泥沙沉降;已经形成的泥沙淤积体对泵口流态影响存在明显空间异质性,中间区域水泵受影响程度低于两侧水泵,开机组合工况优化大幅减小了水流偏流角度(比原工况减少了3.35°),提高了前池流速均匀度(提高了了5.84个百分点),降低了前池内泥沙含量(减少了58.60%)。研究成果可为抑制漩涡区域与泥沙淤积对正向泵站前池的危害和泵站优化运行提供理论支撑。
Water-sediment flow patterns can greatly contribute to the operational efficiency and safety of the pumping station.Among them,the vortex flow patterns have frequently caused sediment deposition in the forebay of forward pumping stations in a sediment-laden river.The forebay of the pumping station is also characterized by a complex two-phase flow structure with water and sediment.It is still lacking in the impact of pump start-up combinations on the flow pattern and suspended sediment movement.In this study,the mixture multiphase flow and the Realizable k-εturbulence model were utilized from an engineering perspective.Grid evaluation criteria were selected as the hydraulic loss of water sediment flowing through the forebay and the operational efficiency of the pump.The inlet of the diversion channel was set as a mixed velocity inflow boundary,while the pump outlet was designated as a free outflow boundary.Solid boundaries were treated using the wall function.The free boundary of the water surface was handled with the assumption of a free-sliding rigid cover.A mathematical model was then established for the forebay of the pump station.The flow and sediment movement were simulated under different start-up combinations.The characteristics and formation mechanisms of each vortex region were analyzed to predict the sediment deposition in the forebay.An optimal start-up combination was proposed to alter the flow field structure.The hydrodynamic dredging was achieved for the large sediment deposits within the forebay.The velocity and sediment deposition within the forebay were measured using the Acoustic Doppler Current Profilers velocity profiler.These measurements were also used to validate the numerical simulation.The results show that a"plane sudden expansion vortex"was formed in the water-sediment two-phase flow from the diversion channel to the inlet of the forebay,due to the separation of the boundary layer.The vortex depth was about 90%of the water depth.A"near bottom three-dimensional vortex"in the intake pond was formed,influenced by the sudden increase of local water depth and the plane vortex.The vortex depth was about 93%of the water depth.The suspended sediment migrated to both sides of the forebay wall under the action of the vortex,where the"fan-shape"sediment deposition was observed.The total sediment deposition accounted for about 60%of the total volume of the forebay.At the same time,the sediment content at the bottom of the intake pond was 8 to 9 times higher than that of the diversion canal.While the sediment content in the middle area was basically the same as that of the diversion canal.A total of five start-up combinations were proposed,including imported full open type,imported half-open type,intermediate focusing type start-up pump,two side decentralized type start-up pump,and fully open type pump.The comprehensive comparison showed that the flow pattern was significantly improved in the forebay after 91 days of operation of the pump station.Specifically,the flow velocity uniformity at the pump port of intermediate focusing type case 5 increased by 5.84 percentage pointss,whereas,the drift angle,the area of high sediment concentration area,and the sediment deposition decreased by 3.35°,75%,and 58.60%,respectively.The findings can provide theoretical support to mitigate the harmful effects of vortex areas and sediment deposition in the forebay,thereby optimizing the operation of the pumping station.In addition,future research should consider optimizing and improving many more factors,including the separated forebay,in order to further optimize the sediment deposition and operation efficiency in the forebay of the pump station.
作者
王海东
许栋
冉启华
袁赛瑜
唐洪武
WANG Haidong;XU Dong;RAN Qihua;YUAN Saiyu;TANG Hongwu(Key Laboratory of Hydrologic-Cycle and Hydrodynamic-System of Ministry of Water Resources,Hohai University,Nanjing 210098,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2024年第19期52-61,共10页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家重点研发计划项目(2022YFC3200032)
国家自然科学基金项目(52179076,U2340221)。
关键词
泵站
两相流
正向前池
开机组合
流速均匀度
偏流角
pumping station
two-phase flow
forward forebay
start-up combinations
uniformity of flow velocity
deviation angle
作者简介
王海东,博士,助理研究员,研究方向为泵站工程多相流。Email:wanghaidong@hhu.edu.cn;通信作者:许栋,博士,教授,博士生导师,研究方向为水力学及河流动力学。Email:xudong@hhu.edu.cn。
