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<p>Under outflow conditions, water flows from the inlet/outlet to the reservoir, and the inlet/outlet experiences complex separated flow, which affects flow efficiency. In this study, proper orthogonal decomposition (POD) methods are used to identify the main characteristics of the multi-scale motions and reveal the impact of these flow structures on the separated flow within the inlet/outlet. Flow separation first appears at the upper right corner of the inlet/outlet, then extends to cover the top of the inlet/outlet, leading to reduced flow efficiency. Shear layers are present above and below the core flow, with significant fluctuating momentum exchange. The separated flow is dominated by large-scale motions, with two main features observed. On the one hand, there is a large-scale streak structure at a frequency of the Strouhal number, <i>Sr</i> = 0.044, causing the core flow to oscillate back and forth along the streamwise direction, accompanied by oscillations within the separation zone. On the other hand, large-scale streak structures at frequencies <i>Sr</i> = 0.116–0.335 induce lateral oscillations in the core flow, which manifest as up-down and left-right movements. Small-scale motions significantly influence the turbulence characteristics of the separated flow. Vortical structures exist above and below the core flow, where their growth, merging, and breakup result in high turbulence intensity, increasing the head loss in the inlet/outlet. Studying the complex separated flow within the inlet/outlet contributes to optimizing the design of inlet/outlet in pumped storage power stations.</p>

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Study of multi-scale turbulence structures in lateral inlet/outlet of pumped storage power stations

  • 期刊论文

  • 发表日期：

    2026年7月31日

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  • Gang-gui Guo,
  • Ya-kun Liu,
  • Ze Cao,
  • Di Zhang,
  • Yang-yu Deng

摘要

Under outflow conditions, water flows from the inlet/outlet to the reservoir, and the inlet/outlet experiences complex separated flow, which affects flow efficiency. In this study, proper orthogonal decomposition (POD) methods are used to identify the main characteristics of the multi-scale motions and reveal the impact of these flow structures on the separated flow within the inlet/outlet. Flow separation first appears at the upper right corner of the inlet/outlet, then extends to cover the top of the inlet/outlet, leading to reduced flow efficiency. Shear layers are present above and below the core flow, with significant fluctuating momentum exchange. The separated flow is dominated by large-scale motions, with two main features observed. On the one hand, there is a large-scale streak structure at a frequency of the Strouhal number, Sr = 0.044, causing the core flow to oscillate back and forth along the streamwise direction, accompanied by oscillations within the separation zone. On the other hand, large-scale streak structures at frequencies Sr = 0.116–0.335 induce lateral oscillations in the core flow, which manifest as up-down and left-right movements. Small-scale motions significantly influence the turbulence characteristics of the separated flow. Vortical structures exist above and below the core flow, where their growth, merging, and breakup result in high turbulence intensity, increasing the head loss in the inlet/outlet. Studying the complex separated flow within the inlet/outlet contributes to optimizing the design of inlet/outlet in pumped storage power stations.