EFFECTS OF DISTANCE BETWEEN TWO T-SHAPED SPUR DIKES ON FLOW PATTERN IN A 90 DEGREE BEND USING NUMERICAL MODEL

Spur dike is a type of flow control structure. Certain changes occur in flow pattern due to installation of a dike (especially a T-shaped spur dike). This paper studied the effects of distance between two T-shaped spur dikes on flow pattern in a 90° bend. The first spur dike was installed in the middle of bend at the outer bank and the second one was installed separately at distances of 2.5, 3.5 and 5 times the spur dike length. For each distance between the dikes, a numerical analysis was performed. It was observed that near the bed, the flow moved toward inner bank but on the water surface it moved toward outer bank. By increasing the distance between the dikes, the dimensions of vortexes increased. Near the bed and on the water surface, three vortexes were formed: (1) at upstream of the first dike,(2) in the dikes field and (3) at downstream of the second dike. The dimensions, numbers and location of vortexes changed by changing the distance between spur dikes. At upstream of the second dike, three vortexes were formed: (1) a central vortex, (2) a vortex near the bed in front of the dike wing and (3) a vortex at outer bank.