黄河头道拐段冰输移及堆积过程数值模拟

头道拐河段因其特殊的河道形态及地理位置而成为黄河内蒙古段最易形成冰坝的河段，研究该河段河冰输移及堆积过程是理解内蒙古段河冰过程及卡冰结坝作用机理的关键。本文基于耦合的二维有限元水动力学模型和DPM(Discrete Parcel Method)河冰动力学模型，模拟了黄河头道拐河段2020—2021年冬季封河过程并进行了验证，讨论了不同水力条件、上游流凌密集度及河道形态对封河过程的影响。结果表明：相比于官牛犋弯道，河道弯曲率大、束窄程度高的什四份子弯道更易形成卡冰，且流量越小，卡冰作用越明显，冰盖向上游发展速度越快。河道流凌密集度小于0.4时，各种流量下研究河段未发生卡冰；流凌密集度增大至0.4,表面流冰首先在弯曲率系数较大的什四份子弯道处形成卡冰，随着流凌密集度和流量的进一步增大，下潜并输移到下游的流凌也会在官牛犋弯道形成卡冰，因此，头道拐河段形成卡冰的流凌密集度临界条件为0.4。应用冰水耦合二维动力学模型可以很好地模拟天然河道河冰输移、堆积过程中河道的水力特性、冰厚增长及封河形态，揭示了影响河冰过程的相关因素及作用机理，为黄河内蒙古段防凌减灾工作提供技术支撑。

Numerical simulation of ice transport and accumulation process in Toudaoguai reach of the Yellow River

Because of its unique channel morphology and geographic location, the Toudaoguai river reach is the most vulnerable to ice dam formation in the Inner Mongolia section of the Yellow River.Study on the river ice transport and accumulation process in this reach is the key to understanding the river ice process and the mechanism of ice damming formation in the Inner Mongolia section.The winter freeze-up process of the Toudaoguai reach from 2020 to 2021 was simulated and validated based on the coupled two-dimensional finite element hydrodynamic model and DPM river ice dynamics model.The influencing factors of the freeze-up process have been discussed, like hydraulic conditions, ice concentration, and channel morphology.Results show that compared with the Guanniuju bend, the Shisifenzi bend, which has a large bend rate and a high degree of narrowing, is more likely to form ice jamming, and the smaller the flow rate, the more obvious the ice jams effect is, and the faster the ice cover develops upstream.When the ice concentration is less than 0.4, no ice jam occurs in the study section under various flow rates;when the ice concentration increases to 0.4, the surface ice first forms ice jam at the bend of the Shisifenzi where the bending rate coefficient is large, and with the further increase of ice concentration and flow rate, the ice run that dives and moves downstream also forms ice jam at the bend of the Guanniuju bend, therefore, the ice concentration that forms ice jam in the Toudaoguai section of the river.The ice water coupled two-dimensional dynamics model can simulate the hydraulic characteristics, ice thickness growth and river closure pattern of the natural river during the process of ice transport and accumulation, revealing the relevant factors and mechanisms affecting the river ice process, and providing technical support for the prevention and mitigation of the Yellow River Inner Mongolia.