Stepped cascades, chutes and spillways have been in use for more than three millennia. With the introduction of new construction materials and techniques, the staircase chute design has regained some interest within t...Stepped cascades, chutes and spillways have been in use for more than three millennia. With the introduction of new construction materials and techniques, the staircase chute design has regained some interest within the last forty years. The stepped invert increases significantly the energy dissipation occurring above the steep chute and reduces the size of the required downstream stilling structure. The application of stepped chutes further encompasses in-stream re-aeration and water treatment plant cascades, to enhance the air-water transfer of atmospheric gases and of volatile organic components. However, the engineering design of stepped spillways is not simple because of the hydrodynamic challenges, with several markedly different flow regimes, some complicated two-phase air-water fluid dynamics and massive rate of energy dissipation above the stepped chute. Simply, the technical challenges in the hydraulic design of stepped spillways are massive. This review paper examines the hydraulic characteristics of stepped chute flows and develops a reflection on nearly three decades of active hydraulic research, including recent field measurements during major flood events. The author aims to share his passion for the complicated hydraulic engineering, as well as some advice for engineering professionals and researchers.展开更多
持续的周期性小扰动会引发电力系统强迫振荡,通过切除扰动原则可以使振荡迅速衰减。为了能够找到扰动源的具体位置,使振荡快速平息,对共振稳态时线性化系统能量转换特性进行了分析,结合实际电网扰动源自动定位存在的一些问题,对能量函...持续的周期性小扰动会引发电力系统强迫振荡,通过切除扰动原则可以使振荡迅速衰减。为了能够找到扰动源的具体位置,使振荡快速平息,对共振稳态时线性化系统能量转换特性进行了分析,结合实际电网扰动源自动定位存在的一些问题,对能量函数法进行了改进,提出了利用耗散功率进行扰动源识别的新方法。基于该方法,对4机2区系统、某实际大电网仿真模型以及广域测量系统(wide area measure system,WAMS)实测数据进行了仿真分析,结果表明利用耗散功率能够快速准确地确定强迫功率振荡扰动源的位置,说明了利用耗散功率进行扰动源识别方法的可行性以及对实际电网的适用性。展开更多
文摘Stepped cascades, chutes and spillways have been in use for more than three millennia. With the introduction of new construction materials and techniques, the staircase chute design has regained some interest within the last forty years. The stepped invert increases significantly the energy dissipation occurring above the steep chute and reduces the size of the required downstream stilling structure. The application of stepped chutes further encompasses in-stream re-aeration and water treatment plant cascades, to enhance the air-water transfer of atmospheric gases and of volatile organic components. However, the engineering design of stepped spillways is not simple because of the hydrodynamic challenges, with several markedly different flow regimes, some complicated two-phase air-water fluid dynamics and massive rate of energy dissipation above the stepped chute. Simply, the technical challenges in the hydraulic design of stepped spillways are massive. This review paper examines the hydraulic characteristics of stepped chute flows and develops a reflection on nearly three decades of active hydraulic research, including recent field measurements during major flood events. The author aims to share his passion for the complicated hydraulic engineering, as well as some advice for engineering professionals and researchers.
文摘持续的周期性小扰动会引发电力系统强迫振荡,通过切除扰动原则可以使振荡迅速衰减。为了能够找到扰动源的具体位置,使振荡快速平息,对共振稳态时线性化系统能量转换特性进行了分析,结合实际电网扰动源自动定位存在的一些问题,对能量函数法进行了改进,提出了利用耗散功率进行扰动源识别的新方法。基于该方法,对4机2区系统、某实际大电网仿真模型以及广域测量系统(wide area measure system,WAMS)实测数据进行了仿真分析,结果表明利用耗散功率能够快速准确地确定强迫功率振荡扰动源的位置,说明了利用耗散功率进行扰动源识别方法的可行性以及对实际电网的适用性。
