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<p>One limitation in existing air chamber models is the assumption that the water surface rises and falls uniformly. However, the water surface actually exhibits nonlinear non-uniform oscillations that can be classified into two distinct modes: transverse surge oscillations (TSOs) and longitudinal surge oscillations (LSOs). To address this issue, a novel mathematical model of the pipe-shaped air chamber (PSAC) was proposed to enable the simultaneous simulation of TSOs and LSOs. By incorporating the engineering layout and mechanical characteristics of a real hydropower plant, the nonlinear dynamic performance of LSOs and their propagation characteristics are examined in detail. Furthermore, the effects of LSOs on extreme water levels within the PSAC and pressure variations at the spiral case inlet were analyzed under scenarios of load increase and load rejection, respectively. The results indicate that when LSOs are considered, the surge oscillations within the PSAC exhibit additional peak-shaped fluctuations, compared with the conditions wherein LSOs are neglected. As a result, the maximum inlet pressure at the spiral case increases and the minimum pressure decreases. Furthermore, the PSAC experiences higher maximum and lower minimum surges, with the surge extremum difference potentially reaching 1.04&#xa0;m. That means neglecting the impact of LSOs on hydraulic transients may lead to an insufficient minimum water depth in the PSAC and thereby pose significant risks to operational safety.</p>

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Nonlinear dynamic analysis of the longitudinal surge oscillations in hydraulic transients of a hydropower system featuring a pipe-shaped air chamber

  • 期刊论文

  • 发表日期：

    2025年7月12日

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  • Weixin Qiu,
  • Jian Zhang,
  • Chao Hu,
  • Xiaodong Yu,
  • Sheng Chen,
  • Yi Liu

摘要

One limitation in existing air chamber models is the assumption that the water surface rises and falls uniformly. However, the water surface actually exhibits nonlinear non-uniform oscillations that can be classified into two distinct modes: transverse surge oscillations (TSOs) and longitudinal surge oscillations (LSOs). To address this issue, a novel mathematical model of the pipe-shaped air chamber (PSAC) was proposed to enable the simultaneous simulation of TSOs and LSOs. By incorporating the engineering layout and mechanical characteristics of a real hydropower plant, the nonlinear dynamic performance of LSOs and their propagation characteristics are examined in detail. Furthermore, the effects of LSOs on extreme water levels within the PSAC and pressure variations at the spiral case inlet were analyzed under scenarios of load increase and load rejection, respectively. The results indicate that when LSOs are considered, the surge oscillations within the PSAC exhibit additional peak-shaped fluctuations, compared with the conditions wherein LSOs are neglected. As a result, the maximum inlet pressure at the spiral case increases and the minimum pressure decreases. Furthermore, the PSAC experiences higher maximum and lower minimum surges, with the surge extremum difference potentially reaching 1.04 m. That means neglecting the impact of LSOs on hydraulic transients may lead to an insufficient minimum water depth in the PSAC and thereby pose significant risks to operational safety.