黄河什四份子弯道冰期水流及冰塞特征研究

覆冰条件下,弯道水流固有的三维特性更为复杂,对河流弯道冰下水流特征及冰塞的研究有助于推进防凌减灾工作。依据2020年1月稳封期的原型观测数据,对黄河什四份子弯道冰下水流及冰塞特征进行了详细分析。结果表明,弯顶节点工程引起的回流是阻冰的重要条件,上游下潜的冰花因水动力不足及河势等因素影响发生堆积,冰塞在弯内形成并沿凹岸主槽逐渐向上游发展,同时,弯顶卡冰封河与下游较大的水流流速,促进了清沟的形成;入弯至弯顶区间,冰下水流流速垂线分布基本服从双对数分布规律;受凹岸冰塞及回流影响,纵向上,水流流速呈减小趋势,在弯顶附近开始恢复;径向上,河道主流被冰塞压迫并逐渐趋于凸岸,致使弯道主流易位,凸岸水流流速大于凹岸,清沟向凸岸偏移;弯道水流湍动能与雷诺应力主要在近底处存在较大的变幅,表明近底水流运动活跃,且二者大小与流速大小在径向与纵向分布上具有较好的一致性,受冰盖影响,水流湍动能沿水深近似呈"S"形分布,雷诺应力分布无明显规律。

Study on the characteristics of flow and ice jam in Shisifenzi bend in the Yellow River during the freeze-up period

The inherent three-dimensional characteristics of the flow under ice in curves are more complex. Based on the experiment data of January 2020 freeze up period, the characteristics of flow movement and the formation mechanism of ice jam in Shisifenzi bend of the Yellow River were analyzed in detail. The results show that backflow caused by the project at bend apex is an important factor of ice resistance. The frazil ice in the upper reaches of the river accumulated due to the lack of hydrodynamic force and the river regime. Ice jam formed within the bend and gradually develop upstream along the main channel of the concave bank,under the condition of the ice jamming and freeze-up in the bend apex and the high downstream velocity, the free flow area formed. The vertical distribution of the velocity is basically in line with the law of double logarithmic distribution. Influenced by the concave bank ice jam and the backflow area, on the streamwise, the flow velocity decreases and starts to recover near the bend apex, on the radial, the main stream is compressed by the ice jam and gradually tends to the convex bank, resulting in the translocation of the main stream in the bend. The flow velocity of the convex bank is greater than that of the concave bank, the free flow area is shifted towards the convex bank. The turbulent kinetic energy and Reynolds stress have a large amplitude mainly near the bottom, indicates that the flow near the bottom is active,the radial and longitudinal distributions of them are in good agreement with the velocity,and moreover, the turbulent kinetic energy is approximately distributed in an "S" shape along the water depth, while the Reynolds stress is irregular.