Scour patterns around of single plants and the flow kinematics around them

The bank and floodplain vegetation are not just one of the main resources of aquatic life, but also the reason for hydrolic smoothness. Plants which live in floodplain areas establish slope stability, help aquatic life with thier morphological and ecological services. With the growing importance of the environmental awereness, there are ongoing studies conducted to use the plants on the floodplain areas. However, the effect of vegetation on sediment transport along the river is not fully understood yet. Furthermore, how turbulance and scouring are affected by plants that are growing on slopes and in the island is still unknown as well. On this study same type of plants positioned in channel with different variations for observing the differences in flows, turbulence and scouring characteristics. Other than the plants the same observations are also made with rigid cylinder, cylinders which are ordered as a hexagonal formation and compared with plants. The experiments are done in 26 m long, 0.98m width and 0.85 depths flow channel. Solid matters placed at the bottom of the channel to create an artificial bed and plants and tubes used in the experiments positioned in this horizontal bed. The first plant used in three different ways: emerged vertical position, covered with stretch wrap (impermeable), leaned. While another same type plant is first submerged and then covered with stretch wrap. The reason of wrapping plants is to understand the role of plant's canopy's permeability in problem's hydrodynamic. On the other hand, three different current flows are selected in pre-experiments, were used for every type of plant configuration. All of the experiments are done in steady flow conditions. The velocity data is measured by two acoustic Doppler velocitymeters and the scour data is obtained by the laser scanner. During the analysis, scour patterns at the bed and velocity components near the bed, through streamline are investigated. From obtained scour patterns, center of gravity of scouring areas were calculated and scour and deposition amount of transverse, longitudinal and depth was calculated. Respectively, differences between flow around the plants and flow around other obstacles of structures were investigated. As a result of experiments, scour patterns around obstacles were found significantly different. Based on the idea of scour patterns are resultant in the steady flows around plants, regular structures around plants are interpreted. The most important difference between flow around cylinder and plant is downflow at the upstream of plant is much smaller then cylinder and correspondingly horseshoe vortices are much weaker. Another important difference is the subcanopy flow of the plant does not form at the cylinder condition. In addition, the size of the separation around plants are weaker then the ones around cylinder.