坡面流水动力学特性研究

Study on Hydro-dynamic Properties of Overland Flow

采用变坡水槽研究了坡面流水动力学参数 (流态、流速、水深及阻力系数 )随流量和坡度的变化规律。结果表明 ,坡面流流态与水深密切相关 ,当水流深度小于 0 .316 cm时 ,坡面流呈过渡流 ,水深大于 0 .316 cm时呈紊流流态 ;当坡度为 5～ 2 5°、单宽流量为 0 .6 2 5～ 12 .5× 10 - 3m3/(s· m)时 ,坡面流平均流速和平均水深主要受流量控制 ,坡度的影响并不显著 ,可用简单的线性函数来模拟平均流速、水深与流量和坡度间的关系 (r2分别为 0 .89,0 .78) ;当流量小于 0 .0 0 2 m3/s时 ,坡度对阻力系数的影响较为显著 ,当流量大于 0 .0 0 2 m3/s时 ,阻力系数基本受流量控制 ,随着流量增大 ,阻力系数呈幂函数形式下降。这说明坡面流的水动力学特性与明渠水流存在较大差异 ,在坡面水蚀机理分析、土壤侵蚀物理模型的构造过程中应予以充分考虑。

The relationship for hydro dynamic parameters (flow regime, flow velocity, depth and friction factor) as a function of flow discharge and slope gradient was simulated by means of flume experiments. The results demonstrate that when flow depth is less than 0.316 cm, the flow is transitional flow. The flow change to turbulent when flow depth is large than 0.316cm. The flow velocity and depth are mainly controlled by flow discharge, simple linear function can be used for mean velocity and flow depth predicting. Slope gradient has no significant impact on both flow velocity and depth and has influence on friction factor at low flow discharge. However, as discharge increasing, the friction factor will be controlled by discharge again. All these results reveal that there is larger difference exiting in hydrodynamic properties between overland flow and open channel flow, and should be full considered in water erosion mechanism analyzing and model building.