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By choosing a PVC slice to simulate flexible vegetation,we carried out ex-periments in an open channel with submerged flexible vegetation.A 3D acoustic Doppler velocimeter(micro ADV) was used to measure local flow velocities and Reynolds stress.The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different.In a region above the vegetation,Reynolds stress distribution is linear,and the measured velocity profile is a classical logarithmic one.Based on the concept of new-riverbed,the river compression parameter representing the impact of vegetation on river is given,and a new assumption of mixing length expression is made.The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation,and is useful in applications.
By choosing a PVC slice to simulate flexible vegetation, we carried out ex-periments in an open channel with submerged flexible vegetation. A 3D acoustic Doppler velocimeter (micro ADV) was used to measure local flow velocities and Reynolds stress. The results show that hydraulic characteristics in non-vegetation and vegetation layers are totally different. In a region above the vegetation, Reynolds stress distribution is linear, and the measured velocity profile is a classical logarithmic one. Based on the concept of new-riverbed, the river compression parameter the impact of vegetation on river is given, and a new assumption of mixing length expression is made. The formula for time-averaged velocity derived from the expression requires less parameters and simple calculation, and is useful in applications.