边界条件对植被化矩形复式河槽流速及床面切应力的影响

在水深平均动量方程中加入了植被引起的拖曳力,给出了垂线平均流速及床面切应力的2维解析解.根据滩地植被化矩形复式河槽的断面形态特点,建立了滩槽交界面的切应力平衡方程进而提出了2种边界条件.比较这2种边界条件后发现它们的计算结果在水深较大时几乎相同,而水深较小时在剪切区内有一定差别,考虑了主槽边壁切应力影响的边界条件可以给出更好的计算成果.运用8组不同的矩形复式河槽试验资料对该边界条件的应用情况进行验证,结果发现,在各个区域选取合适的二次流系数比忽略二次流能更好地模拟流速及床面切应力分布,在各组矩形复式河槽工况中,考虑二次流可以得到较好的计算成果.

Effection of Boundary Conditions to Depth-averaged Velocity and Bed Shear Stress in Vegetated Rectangular Compound Channels

The drag force of vegetation was introduced in the depth-averaged momentum equation and the analytical solutions of depth-averaged velocity and bed shear stress were presented. Based on the feature of cross-section of vegetated rectangular compound channels, the force balance equation was built at the interface between main channel and floodplain and then two boundary conditions were carried out. The predicted results of these two boundary conditions were compared and it was noticeable that their results were almost the same at a high relative flow height while some differences were in the shear layer at a low one. The continuity condition which was considered the wall shear stress in main channel provided better predictions. Finally, eight groups of experimental data were applied to verify the predicted ability of the better boundary condition. The results showed that optimal secondary flow coefficients in each domain led much better lateral distributions of depth-averaged velocity and bed shear stress, especially in main channels. Good predicted results can be obtained by chosen appropriate secondary flow coefficients in each case.