含植物河流动力学实验研究—流速、摩阻流速及曼宁糙率系数垂线分布

Experimental studies of hydrodynamics in vegetated river flows —Vertical profiles of velocity, shear velocity and Manning roughness

根据实验室水生植物水槽中71个断面上的点流速及水深、流量和水生植物密度,分析了:1)流速垂线分布;2)相对摩阻流速的垂线分布;3)曼宁糙率系数的垂线分布规律及水生植物密度对它们的影响。结果表明:1)含植物河流中的流速垂线分布呈三区,从下至上分别为冠层区、过渡区和冠层以上区;2)相对摩阻流速垂线分布受水槽底边壁、植物和自由水面的影响,在三个区内各不相同;3)曼宁糙率系数的垂线分布呈倒"S"形。同时,本文归纳出含植物河流流速垂线分布经验公式,该公式可进一步运用到实际河流中。

Based on the laboratory experimental data of flow velocities for different water depths, discharges and aquatic vegetation densities, analysis are made for: 1) the vertical profiles of flow velocities; 2) the vertical profiles of the relative shear velocities; 3) the vertical profiles of the Manning roughness coefficients. Results show: 1) the vertical profiles of the flow velocities exhibit three zones, the within-canopy, the transitional and the above-canopy zones; 2) the relative shear velocities have different vertical trends in the three zones; 3) the vertical profile of the Manning roughness coefficients has the shape of a reverse 'S'. Furthermore, a new empirical formula for the vertical profiles of velocities is deduced.