降雨和坡面流共同作用下的坡面薄层流水动力学特性

发布时间：2018-05-06 03:18

本文选题：模拟降雨 + 坡面薄层流　；参考：《北京林业大学学报》2017年08期

【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)m~3/(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]:In order to study the dynamic characteristics of thin layer flow of slope under the action of rainfall and slope flow, a steep slope fixed bed scour test and artificial simulated rainfall experiment were carried out at the National Positioning observation Station of Forest ecosystem in the three Gorges Reservoir area of Jinyun Mountain, Chongqing. The depth and velocity of the slope flow were calculated and studied under the influence of 4 kinds of roughness, 0. 009 ~ 0. 180 ~ 0. 250 ~ 0. 425 mm 路h ~ (-1) and 3 typical rainfall intensity and no rainfall. The average velocity, the correction coefficient of velocity, the flow state index were calculated and studied under different working conditions, and the average flow velocity, velocity correction coefficient and flow state index of the slope flow were calculated and studied under the conditions of 0. 486 脳 10 ~ (10) ~ (-3) 脳 10 ~ (-1) ~ (3) ~ 1 脳 10 ~ (6) 脳 10~(-3)m~3/(s ~ (-1). The characteristics of hydrodynamic parameters, such as flow state and slope flow resistance, show that the average velocity of flow increases by power function with the increase of single wide flow rate, and decreases with the increase of roughness. The correction coefficient of velocity is 0.04 ~ 0.37 for no rainfall, and 0.422 ~ 0.98 for rainfall. The range of flow state index of rainfall is 0.291 ~ 0.538. When no rainfall occurs, the flow state index decreases with the increase of roughness. When the rain intensity is 30 mm/h, the change degree is 18% -29% and 12%, respectively. When the rain intensity is 60 mm/h, the change degree is 12% -17% and -16%, respectively; when the rain intensity is 30 mm/h, the change degree is -17% and -16%, respectively. The flow state index shows a more obvious downward trend, its variation degree is -6% and -11 路3 respectively) the Reynolds number of flow is 500 ~ 2 000. Under all experimental conditions, the flow pattern belongs to the transitional zone of layer turbulence, the whole state of water flow tends to be jet state, and when there is no rain, The relationship between roughness and flow state is obvious, the smaller the value of water flow is, the closer the jet flow is, but when rainfall, the disturbance of rainfall is no longer correlated with the relationship between them. 4) the Darcy resistance coefficient of slope flow has a positive correlation with roughness. The calculation formula of slope flow resistance considering the influence of rain intensity is lower than the formula without rain intensity, the correlation coefficient is decreased by 0.01 and rainfall has no significant effect on the resistance coefficient.
【作者单位】：北京林业大学重庆缙云山三峡库区森林生态系统国家定位观测研究站北京林业大学北京市水土保持工程技术研究中心;
【基金】：国家自然科学基金项目(51309006) 北京林业大学“国家级大学生创新创业训练计划”(201610022016)
【分类号】：S157

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