| The long-distance water transfer project is an important strategic infrastructure to alleviate water shortage and optimize water resource allocation in China.However,longdistance channels in high-latitude areas face various ice conditions such as shore ice,drift ice,and ice sheets during winter water transfer,which limits the channel’s winter water transfer capacity and is highly likely to generate ice blockages and dams,posing a threat to the safe operation of the project.In order to alleviate channel ice conditions and improve winter water delivery capacity,this paper proposes a method of introducing reservoir bottom temperature water to increase channel water temperature.Objective to explore the generation and dissipation of channel ice conditions and their spatiotemporal evolution under the inflow of external heat sources,and to construct a coordinated regulation scheme for channel water temperature and water level.This article takes the Middle Path Project of the South-North Water Diversion Project as the research object.Based on the analysis of the winter ice conditions of the project from 2011 to 2023,the three-dimensional simulation of the water temperature mixing characteristics at the intersection of the reservoir’s warm water inlet channel is first carried out,providing a reference for the internal boundary setting of the one-dimensional model;Secondly,a onedimensional simulation model for winter water transport in channels with external heat sources is established,and the mitigation effect of heat source influx on channel ice conditions under extreme cold wave meteorological conditions,different reservoir inflow ratios,and water transport flow rates is explored;Finally,a water temperature water level collaborative control algorithm was designed for the channel with heat sources converging.Research results indicate that:(1)The size of the intersection angle of the channel has a certain impact on the characteristics of the mixing temperature of hydraulic water downstream of the intersection.Considering the smoothness of water flow downstream of the intersection and the effect of temperature increase in the main channel,it is recommended to choose a 60 ° intersection angle in practical engineering applications;The detailed heat method proposed in this article has a higher accuracy in calculating the boundary of the reservoir inlet channel than the flow average method.Compared with the 3D simulation results,the maximum relative errors of water temperature are 0.66% and 8.31%,respectively;The simulation value of downstream water temperature at the inlet point is highly consistent with the prototype observation data,with a maximum error value of 0.15 ℃ and a relative error of 11.7%.The model simulation results are credible.(2)The idea of introducing warm water from reservoirs to increase the water temperature of the main channels and alleviate ice conditions is feasible.When the reservoir inflow temperature is the same,the increase in water temperature is directly proportional to the mixed water flow rate and reservoir inflow ratio.The maximum increase in water temperature downstream of the inlet point is 0.50-2.15 ℃,and the maximum ice cover thickness decreases by 2-7cm;However,the spatial range of the increase in water temperature in the main channel caused by the inflow of warm water from the reservoir is limited,and the effect of the increase in water temperature within a range of 30 km from the reservoir inlet point is more significant;(3)The target threshold range of water temperature will affect the effectiveness of water temperature control.From the perspective of water temperature control effect and channel water level fluctuation,the incremental PI water temperature control algorithm is adopted,and the control effect is better when the target threshold range is 0.5-2.0 ℃.At this time,there will be no ice cover generated during the simulation period,and compared to the constant flow conditions of the reservoir,it can save about 20% of the flow water of the reservoir.The main innovation points of this paper are:(1)Revealing the law of water temperature mixing at different channel intersection angles;(2)The detailed heat method is used to treat the boundary of the reservoir inlet channel,and a one-dimensional ice hydraulics simulation model with external heat sources flowing into the long-distance channel is established;(3)Designing a collaborative control algorithm for channel water temperature and level under the condition of heat source inflow.The idea of using warm water from the diversion reservoir to alleviate ice conditions in the canal proposed in this article can reduce the risk of engineering ice disasters,improve winter water delivery capacity,and is of great significance for ensuring the safe operation of the project in winter and improving the economic benefits of the project.At the same time,the research results of this paper can provide technical solutions and data support for the project management department,and have reference value for the winter operation practice of long-distance water transmission channels in northern areas,with significant social benefits. |
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