Ahmad Jafari - Ph.D. Candidate, Water Sciences Engineering Faculty, Shahid Chamran University, Ahvaz
Mehdi Ghomeshi - Professor, Water Sciences Engineering Faculty, Shahid Chamran University, Ahvaz
Mahmood Bina - Associate Prof., Water Sciences Engineering Faculty, Shahid Chamran University, Ahvaz
Seyed Mahmood Kashefipour - Associate Prof., Water Sciences Engineering Faculty, Shahid Chamran University, Ahvaz

In many conditions in rivers the vertical cylinders are in the bed of the river that flow passes through them. These vertical cylinders like piers of bridge or vegetation on the floodplain of rivers. In the paper attention is focused on the transverse waves generated in a river or an open channel where the flow passes through a cluster of rigid vertical cylinders. In this study a rectangular flume with 72cm in width and 6m in length and 60cm in height was used. The rigid and vertical cylinders with variation sizes were attached to the bed of the flume with different densities and configuration arrangements. A comprehensive set (760 in total) of experiments were conducted in the flume. The waves were produced from the periodic forces created by the vortex shedding from the cylinders. In some of the experiments (119 Exp.) the flow on the obstructions was submerged but still the waves were produced as this phenomenon for the first time is reported in this paper and the oscillations was obviously seen in the flume. The discharge of flow was varied from 2.2 l/s to 25 l/s. The height of the outlet control weir was changed from the highest to the lowest levels, with ten modes of oscillation occurring across the laboratory flume for each sequence. The results provided an explanation for different wave formations that might occur due to vortex shedding when the flowing fluid is water was experimentally investigated and free and submerged flow was on the obstructions. Finally a new formulation was obtained from dimensional analysis, to estimate the amplitude of the transverse wave generated by vortex shedding in rivers or open channels in free or submerged flow.

physical modelling, transverse wave, submerged flow, river