基于唯象模型的部分植被河道流动分析

Analysis of partially vegetated channel flows based on phenomenological model

对局部有挺水植被明渠均匀流,采用分区模型,合理计入区间界面的表观切应力,建立动力平衡方程,推导出各区的断面平均纵向流速公式.基于唯象模型得出了植被区和非植被区交界面上的表观切应力,该应力是由界面上引起动量交换且占主导地位的漩涡产生的.用动量差表征表观切应力,其动量交换系数与占主导地位的漩涡半径和断面水力半径之比的1/3次方成正比.最后将计算结果与实测值进行比较,两者符合良好,表明本文模型可有效用于局部有挺水植被明渠均匀流的水流计算.

A uniform flow in a partially vegetated channel was considered.The flow was divided into two sub-regions along the transverse direction,the vegetated region and the non-vegetated region.And the apparent shear stress in the interface was considered reasonably.The dynamic equilibrium equations were expressed and solved to deduce the average longitudinal velocity.The main novelty was that the apparent shear stress in the interface of vegetated region and the non-vegetated region was obtained based on the theories of phenomenological model.It means apparent shear stress was caused by the dominant vortex there,which brings about momentum exchange.The apparent shear stress was characterized by the difference of momentum,and the coefficient of momentum exchange was proportional to 1/3 of the ratio of the radius of the dominant vortex and the hydraulic radius of the cross section.Finally,comparisons between the computed results and the measured data show that our method does well in predicting the average stream-wise velocity in rectangular channels with partially vegetation.