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    蒋利斌, 张会兰, 杨坪坪, 刘文剑. 降雨和坡面流共同作用下的坡面薄层流水动力学特性[J]. 北京林业大学学报, 2017, 39(8): 77-86. DOI: 10.13332/j.1000-1522.20170126
    引用本文: 蒋利斌, 张会兰, 杨坪坪, 刘文剑. 降雨和坡面流共同作用下的坡面薄层流水动力学特性[J]. 北京林业大学学报, 2017, 39(8): 77-86. DOI: 10.13332/j.1000-1522.20170126
    JIANG Li-bin, ZHANG Hui-lan, YANG Ping-ping, LIU Wen-jian. Hydrodynamics of overland flow under combined effects of precipitation and slope discharge[J]. Journal of Beijing Forestry University, 2017, 39(8): 77-86. DOI: 10.13332/j.1000-1522.20170126
    Citation: JIANG Li-bin, ZHANG Hui-lan, YANG Ping-ping, LIU Wen-jian. Hydrodynamics of overland flow under combined effects of precipitation and slope discharge[J]. Journal of Beijing Forestry University, 2017, 39(8): 77-86. DOI: 10.13332/j.1000-1522.20170126

    降雨和坡面流共同作用下的坡面薄层流水动力学特性

    Hydrodynamics of overland flow under combined effects of precipitation and slope discharge

    • 摘要: 为研究降雨和坡面流共同作用下的坡面薄层流水动力学特性,在重庆缙云山三峡库区森林生态系统国家定位观测研究站开展陡坡定床冲刷及人工模拟降雨试验,实测5种流量(0.486×10-3~1.736×10-3 m3/(s·m))和3个典型降雨强度及无降雨条件下(0、30、60、100 mm/h),受4种不同粗糙度影响(0.009、0.180、0.250、0.425 mm)下的坡面流的水深和流速,计算并研究不同工况下的平均流速、流速修正系数、流态指数、流态及坡面流阻力等水动力参数特征,结果表明:1)水流的平均流速随着单宽流量的增大呈幂函数增加,随粗糙度的增加而减小,无降雨时的流速修正系数为0.04~0.37,降雨时为0.42~0.98,降雨对坡面流起到扰动作用。2)流态指数范围为0.291~0.538,无降雨时,流态指数随着粗糙度的增加而明显减小,其减小程度分别为21%、28%和39%;中小雨强时,流态指数无明显规律,雨强为30 mm/h时,变化程度分别为18%、-29%和12%,雨强为60 mm/h时,变化程度分别为12%、-17%和-16%;大雨强时,流态指数呈现出较为明显下降的趋势,其变化程度分别为-6%、1%和-11%。3)水流雷诺数为500~2 000,所有实验工况下水流流型均属于层紊流过渡区;水流流态整体趋于急流状态;无雨时,粗糙度与流态关系明显,其值越小水流越趋近急流,而降雨时,由于降雨的扰动作用二者不再具有相关关系。4)坡面流达西阻力系数与粗糙度呈正相关关系,与单宽流量呈负相关关系,考虑雨强影响的坡面流阻力计算公式与剔除雨强的公式相比,相关系数下降0.01%,降雨对阻力系数无显著影响。

       

      Abstract: To better understand the role of precipitation and slope discharge on hydrodynamic characteristics of overland flow, the simulated rainfall experiments were carried out at a steep slope (slope gradient was 20°) flume in Jinyun Forest Ecological Station, Chongqing of southwestern China. Velocity v and flow depth h were measured under different conditions of 5 unit discharges q (ranged from 0.486×10-3 to 1.736×10-3 m3/(s·m)), 4 typical rainfall intensities P (0, 30, 60, 100 mm/h) and 4 different surface roughness ks(0.009, 0.180, 0.250, 0.425 mm). Furtherly, the hydraulic parameters, i.e., the mean velocity u, the velocity correction factor, flow-state indicator m, flow regime and overland flow resistance coefficient f were calculated. The results showed that: 1) mean velocity increased with increasing q in power function and v decreased with the increase of ks. The velocity correction factor ranged from 0.04 to 0.37 in rainfall condition while ranged from 0.42 to 0.98 without rainfall. The overland flow was disturbed by rainfall. 2) The flow-state indicator ranged from 0.291 to 0.538. Without rainfall, flow-state indicator was mainly affected by roughness which was negatively correlated with m. The reduction rate was 21%, 28% and 39%, respectively. With medium-low rain intensity, no obvious variation pattern existed. When the rain intensity was 30 mm/h, the variation rate was 18%, -29% and 12%, respectively. When the rain intensity was 60 mm/h, the variation rate was 12%, -17% and -16%. With high rain intensity, the flow-state indicator significantly decreased with increasing roughness. The reduction rate was -6%, 1% and -11%, respectively. 3) The Re ranged from 500 to 2 000, therefore the flow regime of overland flow was mainly transition flow. In most cases, flow pattern was supercritical flow. Without rainfall, the roughness was obviously related with the flow regime, that the overland flow tended to be supercritical with smaller roughness value, but this trend was not detecte with rainfall because of its disturbance effect. 4) Darcy resistance coefficient was positively related to ks, while negatively correlated with unit discharge. Comparing the calculation formula of resistance coefficient with rainfall intensity to condition of without rainfall intensity, the correlation coefficient declined by 0.01%, showing that rainfall had no significant influence on resistance coefficient.

       

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