CFD simulation of reverse water-hammer induced by collapse of draft-tube cavity in a model pump-turbine during runaway process

28th IAHR symposium on Hydraulic Machinery and Systems

Zhang, Xiaoxi^1 ; Cheng, Yongguang^1 ; Xia, Linsheng^1 ; Yang, Jiandong^1

State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan

430072, China^1

关键词: Cavitation model;    Cavity development;    CFD simulations;    Coupling modeling;    Dynamic process;    Hydraulic transients;    Reverse water hammer;    Simulated heads;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/49/5/052017/pdf
DOI  :  10.1088/1755-1315/49/5/052017

来源: IOP

【 摘 要 】

This paper reports the preliminary progress in the CFD simulation of the reverse water-hammer induced by the collapse of a draft-tube cavity in a model pump-turbine during the runaway process. Firstly, the Fluent customized 1D-3D coupling model for hydraulic transients and the Schnerr & Sauer cavitation model for cavity development are introduced. Then, the methods are validated by simulating the benchmark reverse water-hammer in a long pipe caused by a valve instant closure. The simulated head history at the valve agrees well with the measured data in literature. After that, the more complicated reverse water-hammer in the draft-tube of a runaway model pump-turbine, which is installed in a model pumped-storage power plant, is simulated. The dynamic processes of a vapor cavity, from generation, expansion, shrink to collapse, are shown. After the cavity collapsed, a sudden increase of pressure can be evidently observed. The process is featured by a locally expending and collapsing vapor cavity that is around the runner cone, which is different from the conventional recognition of violent water- column separation. This work reveals the possibility for simulating the reverse water-hammer phenomenon in turbines by 3D CFD.