Experimental Investigation on Velocity and Shear Stress Distributions in a 90-Degree Bend With and Without Series of Groynes

Groynes are effective and economical structures for river bank protection along bends. The flow analysis around the constructed groynes along the outer bank is complicated. This is mainly due to the effects of groynes on the flow pattern and secondary currents and also interaction effects between the groynes. In the present paper، the effects of series of groynes along a 90-degree mild bend on the flow variables such as mean flow distribution، secondary currents and shear stresses have been investigated. The experiments were carried out in a bend flume with 0. 7 m width and 0. 8 m height. The R/B ratio for the channel bend was 4 and depth of flow was 0. 14 m. The non-submerged Groynes were used in 3 lengths: 15%، 20% and 25% of the channel width. Also the groyne spacing was 3 times greater than its length. The analysis of data showed that the presence of groynes caused uniformity in the velocity distribution at upstream and the high velocity zone moved toward the center of the channel and inner wall. Groynes also reduced strength of the secondary currents. Due to existance of groynes relative shear stress was increased and by increasing of groynes lengths it was increased but lengths of groynes didn’t have significant effect on the location of relative maximum shear stresses and it happend at sections of 70 to 80 degrees of bend in all conditions.