University of Tabriz Water and Soil Science 2008-5133 29 1 2019 03 21 Performance of the Roughness Elements Distances to Reduce Scour and Their Impact on Vertical Velocity Profiles around Bridge Abutment Performance of the Roughness Elements Distances to Reduce Scour and Their Impact on Vertical Velocity Profiles around Bridge Abutment 53 67 8869 FA H Shahsavari M.Sc. Department of Water Engineering, Agricultural College, Isfahan University of Technology, Isfahan, Iran M Heidarpour Prof. Department of Water Engineering, Agricultural College, Isfahan University of Technology, Isfahan, Iran E Landi Instructor Water Engineering Department, Agricultural College, Isfahan University of Technology, Isfahan, Iran A Rahiminia M.Sc. Department of Water Engineering, Agricultural College, Isfahan University of Technology, Isfahan, Iran Journal Article 2019 06 01 Among the issues related to bridges distraction, a flood which causes scouring has been known as the main reason of bridges destruction. Therefore, finding an effective solution is vital for decreasing scouring depth. In this study, the effects of local roughness elements with different distance were investigated for a semicircular abutment under clear water scouring condition. Results showed that existence of roughness reduced the scouring process and reduced the final scour depth by 47%. There was a significant relationship between roughnesses function and the distance between them. So that the existence of an optimal value for the distance between the roughnesses increased the roughness function and decreased the scouring process. In addition, the study of vertical velocity profiles revealed that existence of positive vertical velocity in the hole located at upstream of the abutment and also negative velocities at higher depths were the indicator of downflows. As a result, these downflows lead to the formation of powerful vortexes inside the scouring hole and in front of the abutment. Comparison of the flow profile around the roughened abutment with the control abutment showed that velocity of downflow is significantly reduced for abutment with roughness. Moreover, the depth of scouring hole was reduced at behind of the abutment, due to the impact of roughness on vertical velocity profiles at downstream of abutment. So that, the velocity reduction of the vertical flow in the front and behind of the roughened abutment was to 0.13 U and 0.4 U (U approaching flow velocity), respectively. Among the issues related to bridges distraction, a flood which causes scouring has been known as the main reason of bridges destruction. Therefore, finding an effective solution is vital for decreasing scouring depth. In this study, the effects of local roughness elements with different distance were investigated for a semicircular abutment under clear water scouring condition. Results showed that existence of roughness reduced the scouring process and reduced the final scour depth by 47%. There was a significant relationship between roughnesses function and the distance between them. So that the existence of an optimal value for the distance between the roughnesses increased the roughness function and decreased the scouring process. In addition, the study of vertical velocity profiles revealed that existence of positive vertical velocity in the hole located at upstream of the abutment and also negative velocities at higher depths were the indicator of downflows. As a result, these downflows lead to the formation of powerful vortexes inside the scouring hole and in front of the abutment. Comparison of the flow profile around the roughened abutment with the control abutment showed that velocity of downflow is significantly reduced for abutment with roughness. Moreover, the depth of scouring hole was reduced at behind of the abutment, due to the impact of roughness on vertical velocity profiles at downstream of abutment. So that, the velocity reduction of the vertical flow in the front and behind of the roughened abutment was to 0.13 U and 0.4 U (U approaching flow velocity), respectively. https://water-soil.tabrizu.ac.ir/article_8869_b30a86e430e925763c8b9c049c3ea01f.pdf