三峡和葛洲坝两坝间河道本征波特征分析

Study of eigenwave based on an analytical model in impoundment reach between Three Gorges dam and Gezhouba dam

三峡和葛洲坝之间河道的水动力在两坝泄流量昼夜不均的影响下存在显著的周期性波动特征,其中两坝间的高频本征波动会显著影响反调节策略。文中构建了一维河道水动力学解析模型,并采用实测资料对解析模型进行校验。研究结果表明:枯季时段三峡和葛洲坝的泄流量以及两坝间黄陵庙和南津关站点的水位均存在显著的日波动特征;两坝间河道还存在高频的水位和流量波动过程,其波动频率正好是河道重力波本征频率,即本征波动;该本征波的流量振幅在河道中央达到最大(230 m3/s),两端最小(0);水位振幅在河道两端最大(0.02 m),中央最小(0),即表现出显著的驻波特性;该本征波由上下游坝体泄流量波动共同驱动,其波幅与两坝泄流量波动比值和葛洲坝泄流量的滞后时间相关,当葛洲坝泄流量滞后相位趋近于0或2π时,本征波振幅加强,反之当此滞后相位趋近于π时,本征波振幅减弱。根据研究结果建议,葛洲坝的反调节策略中,其泄流量与三峡泄流量的滞后时间应与重力波在两坝间河道的传导时间一致,即约0.6 h。

Diurnal and higher frequency oscillation of water level and discharge exist in the impoundment reach between Three Gorges Dam(TGD) and Gezhouba Dam(GZD), which exerts significant influence on the counter-regulation of GZD. To study the hydrodynamics of an impoundment reach between two dams, a 1-D analytical model is developed. The model results agreed well with the observation data. Both observation and model results indicate that the water level at both sites of HLM and NJG in the reach between two dams vary diurnally. In addition, the eigenwave is examined, which the wave period is the eigenperiod of the impounded river. The amplitude of eigenwave discharge is largest in the central river(up to 230 m3/s) and lowest in the two ends, while that of water level is highest in the two ends(up to 0.02 m) and lowest in the central river, i.e.,significant standing wave. The eigenwave is induced from both up-and downstream dams, and the amplitude of eigenwave is a function of ratio of incident wave between down-and upstream ends and phase lag of downstream discharge. The amplitude could be strengthen when the value of phase lag closes to 0 or 2π, while that could be wakened when the value of present research, it is suggested that the lag time of GZD discharge should correspond to the travelling time of a gravity wave between two dams during the process of counter-regulation.