Abstract
The effects of rigid vegetation on the turbulence characteristics were experimentally studied in the interior water flume. An ADV was used to determine the three dimensional turbulent velocities in clear water flow without vegetation, sediment-laden flow without vegetation, sediment-laden flow with submerged vegetation and sediment-laden flow with non-submerged vegetation. By experimental and theoretical analysis, the effects of rigid vegetation on the distribution of averaged velocities, turbulence intensities and Reynolds stress were summarized. In sediment-laden flow with submerged vegetation, the averaged stream wise velocities above the top of vegetation fit well with the log distribution low. The three-dimensional turbulence intensities increase from the bottom until they reach the maximum at the top of the vegetation. The method to calculate the shear velocity with the maximum of the Reynolds stress is recommended. In sediment-laden flow with non-submerged vegetation, the turbulence problems cannot be explained by theory of bed shear flow. The average velocities, turbulence intensities and Reynolds stress approximate uniformly distributed along vertical direction.
Highlights
In the beaches and shallow water regions of many rivers or lakes, all kinds of vegetation such as canopy trees, small trees, shrubs, herbaceous wildflowers and grasses are universal and objective
It can be seen that the velocities in the near bottom region deviate from the log distribution law, but the velocities in the main flow region fit well with the formula (3) ( κ = 0.3 and A = 5.4 ). 2) Turbulence intensities In open channel flow, the highest turbulence intensity appears at the near bottom region and here is the source of turbulence vortexes
The method to calculate the shear velocity by the maximum of the Reynolds stress is recommended
Summary
In the beaches and shallow water regions of many rivers or lakes, all kinds of vegetation such as canopy trees, small trees, shrubs, herbaceous wildflowers and grasses are universal and objective. When water flows through vegetation, the microcosmic flow structures present intense three-dimensional motion characteristics and are greatly different from that in boundary-layer flow. In this fields, foreign researches and developments are earlier. Kouwen [1], Gourlay [2], Ei-Hakim [3], Corollo [4] and Järvelä [5] experimentally studied the effects of flexible and rigid vegetation on the distribution of the stream wise flow velocities. The effects of rigid vegetation on the turbulence characteristics were analyzed
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