长距离明渠系统反向输水冰情模拟

针对长距离明渠-闸门-泵站系统冬季反向输水可能出现的冰问题,以南水北调来水调入密云水库调蓄工程为研究对象,升级开发了调水工程冬季输水冰情数值模拟平台。根据实测气象资料和设计资料,对冰情数学模型中的相关参数进行了率定和检验。在此基础上,研究了冰期明渠反向安全输水的水力约束条件,通过模拟调蓄工程典型气温年工况下畅流期、冰盖形成期、稳封期、消融期等冰情演变过程,分析了反向输水的输水能力和冰情特性,并与正向冰期输水能力进行了对比。计算表明,通过控制抽水流量使各渠段泵吸水口拦冰(拦污)设施、倒虹吸或闸门位置处断面佛汝德数满足快速成冰的约束条件,可以保证反向输水;典型年气温下沿程冰厚略小于正向输水工况,且形成冰盖时最大水位波动为0.35 m;从冰封起始的12月中旬提前1~2周启动冬季输水运行工况较为适宜。研究成果可供决策管理部门在冰期制定北京多水源联合调度方案时参考。

Simulation of ice processes during reverse transfer of long distance open channels

Taking the Jingmi diversion canal storage project as a research object for the possible ice problems during the reverse transfer in winter, a numerical ice-water modeling system considering the inner boundaries such as gates and pumps has been established and upgraded. According to the meteorological observation data and design conditions in winter-spring period, the related parameters of ice models are calibrated. As a case study,the proposed system has been applied to the project to analyze the ice characteristics such as the hydraulic control conditions and water conveyance during ice cover forming, development and melting stages. The results show that the safe regulation of reverse transfer can be guaranteed by controlling the Fr number in front of the ice boom. The ice thickness along the canals under reverse transfer is smaller than that under forward conditions. The maximum water-level fluctuation during the ice forming stage is only 0.35 m. Besides, the starting time that 1-2 weeks in advance of the middle of December each year for winter diversion condition is proposed. The conclusions can provide reference for the planning of joint operation model of multiple water sources during winter.