Transient air-water flow patterns in the vent tube in hydropower tailrace system simulated by 1-D-3-D coupling method
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The vent tube is commonly used for the water hammer protection in the hydropower tailrace system. In transient processes, with air entering and exiting the vent tube, one sees complex hydraulic phenomena, which threaten the station’s safe operation. It is necessary to investigate the transient mechanisms in the tailrace system with vent tube. In this paper, a 3-D, two-phase numerical model of a vent tube on the connection of the tailrace tunnel and the diversion tunnel, is developed based on the FLUENT with the volume of fluid (VOF) algorithm to investigate the transient air-water flow patterns and the complex hydraulic phenomena in the vent tube of the tailrace system. A 1-D and 3-D unidirectional adjacent coupling (1-D-3-D-UAC) approach with a linear interpolation method is adopted to adjust the timesteps between the 1-D model and the 3-D model on the tunnel inlet and outlet boundaries through the user defined function (UDF), to transmit the data from the 1-D model to the 3-D model. The model is verified by comparing the results obtained by using the 1-D model alone and from the experiments in literature. The transient flow processes under the full load rejection consist of four stages: the water level dropping stage, the air entering stage, the air pocket collapsing stage, and the air exiting stage. Detailed hydraulic phenomena in the air pocket collapsing process are also discussed.
Key wordsVent tube tailrace tunnel two phase volume of fluid (VOF) 1-D-3-D coupling
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- Yu X., Zhang J. Investigation on hydraulic transients in tailrace tunnel with air inlet and release from the vent [J]. Journal of Hydraulic Engineering, 2016, 47(8): 1045–1053(in Chinese).Google Scholar
- Zhang W., Cai F., Zhou J. et al. Experimental investigation on air-water interaction in a hydropower station combining a diversion tunnel with a tailrace tunnel [J]. Water, 2017, 9(4): DOI: 10.33901w9040274.Google Scholar
- Zhang Z., Hua Y., Cheng H. Numerical simulation of free surface-pressurized flow in tailrace tunnel transformed from diversion tunnel [J]. Yellow River, 2015, 37(4): 105–108(in Chinese).Google Scholar
- Yang K., Guo Y., Fu H. et al. Modelling similarity laws for pipe water-filled transients [J], Journal of Hydraulic Engineering, 2012, 43(10): 1188–1193(in Chinese).Google Scholar
- Zhang J., Suo L. Study on tailrace surge chamber installation and hydraulic transients at pumped-storage plant [J]. Water Resources and Power, 2008, 26(3): 83–87.Google Scholar
- Liu M., Cai F., Zhang W. et al. The impact of air vent on free-surface-pressurized flow in tailrace tunnels [J]. China Rural Water and Hydropower, 2014, (2): 150–152, 156(in Chinese).Google Scholar
- Ljubijankic M., Nytsch-geusen C., Rädler J. et al. Numerical coupling of Modelica and CFD for building energy supply systems [C]. The 8th International Modelica Conference, Dresden, Germany, 2011, 286–294.Google Scholar
- ANSYS Inc. ANSYS FLUENT 14.5 theory guide [M]. Canonsburg, Pennsylvania, USA: ANSYS Inc., 2012.Google Scholar
- Muller K., Vasconcelos J. G. Large-scale testing of storm water geysers caused by the sudden release of air pockets–preliminary research findings [C]. World Environmental and Water Resources Congress, Sacramento, California, USA, 2016, 442–451.Google Scholar
- Muller K. Z., Wang J., Vasconcelos J. G. et al. Water displacement in shafts and geysering created by uncontrolled air pocket releases [J]. Journal of Hydraulic Engineering, ASCE, 2017, 143(10): DOI: 10.1061/(ASCE) HY.1943-7900.0001362.Google Scholar