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为探明降雨条件下沙黄土坡面水流水动力学特性,以流体力学和泥沙运动力学理论为依据,通过5个坡度和5个雨强组合条件下室内模拟降雨试验,系统研究了坡面水流水力参数的变化规律。结果表明,降雨条件下坡面薄层水流雷诺数均小于580,处于层流失稳区;水流流型随雨强和坡度的变化而发生转捩,当坡度较缓、雨强较小时,床面形态处于低能态区和过渡区,床面出现沙纹现象,水流宏观上呈缓流,反之,坡度较陡、雨强较大时,床面由沙纹和沙垄向动平床过渡,宏观上多呈急流;并根据薄层水流阻力组成特点,推导出沙黄土坡面薄层水流阻力计算公式。验证结果表明,该式误差较小,可为坡面侵蚀预报模型的构建提供参考。
In order to find out the hydrodynamic characteristics of the water flow on sandy loess slope under rainfall, based on the theory of fluid mechanics and sediment transport mechanics, the indoor simulated rainfall experiment with 5 slopes and 5 combinations of rainfall intensity was conducted to study the effects of slope water flow Variation of hydraulic parameters. The results show that the Reynolds number of the laminar flow on the slope is less than 580 in the condition of rainfall, which is in the laminar flow instability zone. The flow pattern changes with the change of rainfall intensity and gradient. When the slope is gentle and the rainfall intensity is small, The morphology is in the low-energy state and the transitional area. The bed appears sand-grain phenomenon, and the water flow is slow-flow macroscopically. On the contrary, the slope is steeper and the rainfall intensity is larger, According to the compositional characteristics of flow resistance in thin layer, a formula to calculate the flow resistance of thin layer on the loess slope is derived. The verification results show that the error of this formula is small, which can provide reference for the construction of slope erosion prediction model.