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Purpose -The purpose of this paper is to experimentally and numerically investigate the interference characteristics between two ski-jump jets on the flip bucket in a large dam spillway when two floodgates are running. Design/methodology/approach -The volume of fluid (VOF) method together with the Realizable k-ε turbulence model were used to predict the flow in two ski-jump jets and the free surface motion in a large dam spillway. The movements of the two gates were simulated using a dynamic mesh controlled by a User Defined Function (UDF). The simulations were run using the prototype dam as the field test to minimize errors due to scale effects. The simulation results are compared with field test observations. Findings -The transient flow calculations, accurately predict the two gate discharges compared to field data with the predicted ski-jump jet interference flow pattern similar to the observed shapes. The transient simulations indicate that the main reason for the deflected nappe is the larger opening difference between the two gates as the buttress side gate closes. When both gates are running, the two ski-jump jets interfere in the flip bucket and raise the jet nappe to near the buttress to form a secondary flow on this jet nappe surface. As the gate continues to close, the nappe surface continues to rise and the surface secondary flow become stronger, which deflects the nappe over the side buttress. Originality/value -A dynamic mesh is used to simulate the transient flow behavior of two prototype running gates. The transient flow simulation clarifies the hydraulics mechanism for how the two ski-jump jets interfere and deflect the nappe.

Purpose -Hydraulic instabilities are one of the most important reasons causing vibrations and fatigues in hydraulic turbines. The present paper aims to find the relationship between pressure pulsations and fatigues of key parts of a Kaplan turbine. Design/methodology/approach -3D unsteady numerical simulations were preformed for a number of operating conditions at high heads for a prototype Kaplan turbine, with the numerical results verified by online monitoring data. The contact method and the weak fluid-structure interaction method were used to calculate the stresses in the multi-body mechanism of the Kaplan turbine runner body based on the unsteady flow simulation result. Findings -The results show that vortices in the vaneless space between the guide vanes and blades cause large pressure pulsations and vibrations for high heads with small guide vane openings. The dynamic stresses in the runner body parts are small for high heads with large guide vane openings, but are large for high heads with small guide vane openings. Originality/value -A comprehensive numerical method including computational fluid dynamics analyses, finite element analyses and the contact method for multi-body dynamics has been used to identity the sources of unit vibrations and key part failures. EC 30,3 448 1. Introduction Kaplan turbines are very efficient over a range of operating conditions since the runner blades are movable and the guide vanes can be turned to any angle to match the blade angle. With increases in unit capacities and runner diameters in recent years, units have experienced stability problems such as hydraulic vibrations and cracks in the large hydraulic turbines. The energy transfer in a turbine is accompanied by pressure pulsations caused by vortices, cavitation and other complex flow phenomena in the flow field, which can result in excessive vibrations, leading to structural fatigue failures. Most research in the literature has focused on pressure pulsations in the flow path. For example, Wang et al. (2002) studied the pressure pulsations caused by rotor-stator interactions in the Three Gorges hydraulic turbines. Guedes et al. (2002) simulated unsteady rotor-stator interactions in a pump-turbine with the unsteady computation results validated by LDV and PIV measurements. Muntean et al. (2004) analyzed the flow in the spiral casing and distributor of a Kaplan turbine to obtain information on channel vortices at different operating conditions. Gehrer et al. (2006) used numerical flow simulations to optimize Kaplan turbine runner. Liu et al. (2009a, b) predicted the pressure pulsations in the entire flow passage of a model Kaplan turbine using 3D turbulent unsteady flow simulations with the predicted pressure pulsations at different points along the flow passage agreeing well with test data in terms of their frequencies and amplitudes. Motycak et al. (2010) studied runner-draft tube interactions of low head Kaplan turbines by numerical simulations and model tests. Petit et al. (2010) compared simulation results with e...

The operating states of hydroelectric generating units vary widely as the operating condition change. The details of the operating characteristics and the operating region partitioning method are discussed for two types of large Francis turbines in the Wanjiazhai Hydropower Plant and two same type large Kaplan turbines in the Shuikou Hydropower Plant. For the Wanjiazhai Hydropower units, the most critical factor affecting the operating stability is the hydraulic pressure fluctuations caused by the vortex rope in the draft tube. For Shuikou Hydropower units, the dynamic stresses as in the piston rod and the blade and the hydraulic thrust on the runner induced by the pressure fluctuations in the flow passage should be used to partition the operating regions. Analyzing the distribution cloud of operating characteristic factors which affects the operating stability in the hill-chart for each individual unit, the forbidden, stable and transient operating regions can be obtained. hydroturbine, operating regions, hydraulic pressure fluctuations, dynamic stresses Citation: Wang Z W, Qin L, Zeng J D, et al. Hydroturbine operating region partitioning based on analyses of unsteady flow field and dynamic response. Sci