Mohsen Solimani babarsad - Department of water sciences,Water Science and Environmental Research Center, Shoushtar branch, Islamic Azad University, Shoushtar, Iran.
Amin Hojatkhah - Water Science and Environmental Research Center, Shoushtar branch, Islamic Azad University, Shoushtar, Iran.
Abbas Safaei - Water Science and Environmental Research Center, Shoushtar branch, Islamic Azad University, Shoushtar, Iran.
Roozbeh Aghamajidi - Assistant Professor civil department, Islamic Azad University, Sepidan branch, Sepidan, Iran.

Bridge pier local scouring is a crucial factor in bridge destruction. Studies from different researchers have presented solutions to control this phenomenon. These solutions are divided into two parts, namely, direct and indirect protection. In the direct method, the bed is armoured against scouring whereas in the indirect methods the flow pattern around the pier is changed with geometric parameters. This study defined an element called the deflector structure (flow diverter) to divert the bed’s flow streamline in front of the pier. Experimental scenarios were defined by stabilizing the flow conditions with ۰.۷۰, ۰.۸۳, and ۰.۹۷ relative velocities ( ) and ۱۵-, ۳۰-, and ۴۵-degree wedge deflector structure angles with flow direction for two piers with square and circular cross-sections. The results showed that the dimensionless scour depth parameter ( ) close to the particle movement threshold ( ) was reduced by ۷۰ to ۷۵%, respectively relative to the control model for square and circle cross-section. Changing the angle from ۴۵ to ۳۰ and ۱۵ degrees reduces the local pier scouring and increases the deflector structure’s effectiveness.  

Bridge pier, Deflector, flow diverter, Local scour, Movement threshold