نوع مقاله : مقاله کامل علمی پژوهشی
عنوان مقاله [English]
This study experimentally measures the 3D flow field around the 90 degree bend as well as the bend with the T-shaped spur dike at 75-degree section. The experiments were carried out in a channel with a mild curvature. The three-dimensional Acoustic Doppler Velocimeter (ADV) was used for measuring the flow field. The three-dimensional time-averaged velocity in the 90-degree bend without spur dike and the bend with spur dike was measured. In addition in the bend with spur dike two cases of rigid bed and the bed with scour hole were compared. The longitudinal and lateral flow pattern were compared. The effects of spur dike on flow pattern were examined. In addition, the vortices and reverse flows in the up and down stream of the spur dike as well as the changes in the secondary flow are addressed in this study. The results showed that reverse flows in downstream and upstream of spur dike with rigid or equilibrium bed were formed. Flows formed in downstream were in the greater distance from outer bank than upstream. Also, the start of reverse flow of spur dike with rigid bed was noticeable within a downstream distance of 8 times spur dike length and in spur dike with equilibrium bed of 3 times spur dike length.