有无植物条件下明渠水流紊动特性对比

在可变坡水槽中,模拟了带枝杈植物对明渠水流的干扰作用,借助超声多普勒流速仪(ADV)测量了不同水深下垂线不同测点的瞬时流速,计算了各测点的三维时均流速、脉动强度及雷诺应力等紊动参数,通过与无植物干扰的明渠均匀流紊动特性进行对比,分析植物对水流紊动参数的影响规律。试验结果表明:在有植物明渠水流中,时均流速呈三区分布特征;脉动强度及雷诺应力均在植物顶部附近出现最大值;脉动强度明显增大,在3个方向上趋于接近;可以用植物顶部以上的雷诺应力分布推求摩阻流速。

Comparison of turbulence characteristics of water flow in open channels with and without vegetations

The interferences of vegetations with forks in water flow in open channels were simulated in a flume with variable slopes.The instantaneous flow velocity at different observation points of different water depths was measured with ADV,and the turbulence parameters,including the 3D mean velocity, the turbulence intensity,and the Reynolds stress,at different observation points were calculated.The comparison of the calculated results with the turbulence characteristics of uniform flow without vegetations shows that,with vegetations in water flow,the distribution of mean velocity could be divided into 3 regions,the maximum turbulence intensity and Reynolds stress occur near the top of vegetations,and the turbulence intensity is greatly increased in 3 directions with almost the same value.It is also concluded that the friction velocity can be obtained by the Reynolds stress distribution above the vegetations.