8 Pages

Turbulent hydrodynamics through cross-sections at upstream, interior and downstream of sparse vegetation patch in open channel flow

WithDebasish Pal, Soumen Maji, Prashanth Reddy Hanmaiahgari, Minh Duc Bui, Peter Rutschmann

Jute cultivation is a major crop in India and Bangladesh. Jute plantations belong to the emergent vegetation family and the vegetation density of the jute plantations is usually very sparse. No comprehensive experimental investigation has been carried out so far to compare turbulent hydrodynamics in the lateral direction at the interior and exterior of a sparse and emergent vegetation patch. The proposed study investigates important turbulent features at different cross-sections located in upstream, interior and downstream of sparsely vegetated open channel flow. The emergent vegetation patch is made by seventy uniform rigid acrylic cylindrical rods together with regular spacing between them. A Nortek ADV Vectrinoplus has been used to measure three-dimensional instantaneous velocity components. It is found that the time-averaged streamwise velocity components are decreasing in interior of the vegetation along the streamwise direction. The time-averaged velocity vectors inside the vegetation patch are directed towards the nearest sidewall. The components of time-averaged vertical velocity are negative throughout the cross-section at upstream of the vegetation patch, however absolute magnitudes are decreasing in interior and downstream of the vegetation patch. The values of turbulent kinetic energy are decreasing inside the vegetation patch and interestingly peak values are found far from the channel bed in interior and downstream cross-sections through the vegetation.