全动床复式河槽水流阻力特性的试验研究

Experimental Study on flow Resistance in Compound Channels with Totally Mobile Bed

当水流漫滩后,由于滩槽间存在着强烈的动量交换,复式河槽在过流能力、泥沙输移、流速分布等许多方面不同于单一河道。通过水槽试验,探讨了清水作用下,由非均匀沙构筑而成的全动床复式河槽完全粗化后的水流阻力变化特性,包括水流能量损失、曼宁系数、谢才系数与达西-韦斯巴赫阻力系数等沿程变化。试验结果表明,对于清水作用下的全动床河道很难获得均匀流。断面平均流速沿程变化,单位重量水体经过单位长度而损失的能量将沿程改变。对于该类河道,在给定的水流条件下,阻力系数不再保持为常数,而是沿程变化的。这些特性表明全动床复式水槽水流阻力远比定床的复杂,要准确预测该类河道的过流能力及泥沙输移能力远比定床的困难。

Understanding flow resistance in a compound channel with totally mobile bed is important for determining the stage-discharge curve and supporting the management of fluvial processes. The paper experimentally studies the characteristics of flow resistance for overbank flows in a compound channel with totally mobile bed composed of nonuniforme sediment, including the variation of energy loss and resistance coefficients along the channel after armoring is completed. The experimental results show that it is difficult to obtain uniform flow in this type channel. By analyzing the experimental data, it is found that water surface slope is largely different from energy slope for this type of channel. For this type of channel, under the given condition, the resistance coefficients don＇t keep constant, while they vary along the channel. The characteristics show that flow resistance in compound channels with totally mobile bed is more complex than that in compound channels with rigid bed. As a resistance, it is more difficult to predict conveyance capacity and sediment transport capacity in compound channels with totally mobile bed than in ones with rigid bed.