4种湍流模型对混流式水轮机压力脉动模拟的比较

Comparison of pressure oscillation characteristics in a Francis hydraulic turbine with four different turbulence models

采用RNGk-ε模型、Realizable k-ε模型、Transition SST模型和DES模型,在4种网格尺度下对模型混流式水轮机三维全流道非定常湍流进行模拟.在试验验证的基础上,分析各模型对水轮机压力脉动模拟的适应性,并进行网格无关性分析.分析结果表明:4种湍流模型都可以模拟出尾水管偏心涡带的形态,但尾水涡带在相位上不同,压力脉动的主频或振幅有差别;湍流模型与网格尺度不是单调线性关系,甚至相反;Transition SST模型比RNGk-ε模型、Realizable k-ε模型、DES模型对水轮机压力脉动模拟的适应性更好,在不同网格尺度下预测的压力脉动主频、振幅和试验结果更加吻合.

Three-dimensional unsteady turbulent flow in the entire flow passage of a model Francis hydraulic turbine is simulated using the RNG k-ε turbulence model, the Realizable k-; turbulence model, the transition SST turbulence model and the DES turbulence model and four different mesh systems are used for the Francis turbine model. Using experimental data, the mathematical model is verified. The adaptability of turbulence models and mesh independence for the simulation of pressure oscillation are analyzed. The computational results show that： （a） Four different turbulence models can simulate the distribution pattern of the vortex rope in the draft tube; the dominant frequency and the peak-to-peak amplitude of pres- sure oscillation are different because of the different phases of the vortex rope in the draft tube. （b） With the increase of the mesh number, the accuracy of the turbulence models vary in different way. （c） The transition SST turbulence model can predict the dominant frequency and peak-to-peak amplitude of pressure oscillation more accurately than RNG k-ε model, Realizable k-ε model and DES model with four different mesh systems.