Experimental investigation on streamlines in a 180º sharp bend

One of the most important concerns of hydraulics engineers is predicting erosion at the outer banks of rivers by studying the flow pattern along the bend. Not only are the streamlines in meanders non parallel curved lines, but they are also twisted. To study the streamlines flowing a sharp bend, a 180º sharp bend was constructed at Persian Gulf University in Iran. Three dimensional flow components at different locations of the bend were measured using Vectrino velocim. In this paper, streamlines were drawn and investigated in different longitudinal profiles, cross sections, and plans. The results indicated that the secondary flow strength and size of the vortex formed at the distance of the beginning to the bend apex would increase. The core of central vortex moved away from the inner bank towards central line of the channel by 22%, and to the water surface by 20%. On the contrary, the size of the secondary vortex increased by 15%. In addition, the average of the horizontal angle of the streamlines, vector and the locus of maximum velocity were determined at different levels in the present investigation.