Experimental Study of 3-D Flow Pattern around T-shaped Submerged and Deflecting Spur Dike in 90 Degree Bend with Equilibrium Bed

Document Type : Research Article


1 M.Sc., Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran, Iran

2 Assistant Professor, Department of Civil Engineering, Persian Gulf University, Bushehr, Iran

3 Professor of Hydraulics, Water Engineering Research Inst., Tarbiat Modares University, Tehran, Iran


A study was carried out on the flow pattern around T-shaped submerged and deflecting spur dike located in 45 degree of 90 degree bend. Experiments were carried out in gentle bend with radius to width ratio of 4. To measure 3-D velocity and bed topography, Vectrino+ and point gage devices were used, respectively. First scour experiment was done and bed topography along overall bend was measured and after bed stabilization 3-D velocity was measured. Results indicated the presence of a secondary main clockwise flow and another secondary flow with opposite direction near the outer bank and surface water in first cross section (completely formed in cross section of 25o) and end bend (after end of spur dike influence on flow pattern). Presence of spur dike and change of bed topography leads to the change in secondary flow pattern in the cross section around spur dike. Observations indicated the presence of a separation interface in upstream spur dike and 0.3 depth flow level. In this separation interface two counterclockwise vortices were observed. These vortices are the main scour agent through creation of pressure fluctuations at the upstream wing edge of spur dike. Besides, a counterclockwise vortex with length as long as 2.5 times length of spur dike was observed downstream of spur dike. Analysis of results relevant to scour and flow pattern in cross and longitudinal sections, and different plans are among other points introduced in this paper.    


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