Flow Analysis around Submerged vegetation.

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Thokchom Devi, Bimlesh Kumar

Friday 3 july 2015

8:45 - 9:00h at Mississippi (level 1)

Themes: (T) Sediment management and morphodynamics, (ST) Sediment transport mechanisms and modelling

Parallel session: 14B. Sediment - River

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The present study highlights the flow characteristics around submerged vegetation. Laboratory experiments were conducted in a 17.24 m long glass-sided tilting flume. Acoustic Doppler Velocimeter (ADV) was used for velocity measurements. Vegetation was simulated by flexible rubber cylinders of 10 mm diameter and 8 cm height above the sand bed. Vegetation was arranged in a uniform pattern in a 5 m long test section. Experiments for two different vegetation spacing, 15 cm and 10 cm, were conducted. Different velocity profiles were plotted for different measuring positions around vegetation along a section. Results have shown that velocity is reduced in front of the vegetation as compared to other measuring positions. But the velocity gradient is more due to more shear stress. The maximum Reynolds stress for all the locations is found near the top of the vegetation because of the drag imposed by the vegetation stems irrespective of the vegetation spacing. Quadrant analysis was carried out for explaining the different events of bursting phenomenon at each location. It is shown that stress contribution is mainly from ejection and sweep events as compared to other events.