The effect of slot on bed topography around the bank attached triangular vane in 90 degree bend

Although the spur dikes have appropriate performance to protect rivers bank, these structures are not immune from the local scour around their tips. Recent researches have shown that the bank attached triangular vanes has less scour depth at their tips toward the spur dikes because of their geometrical shape. One of the methods of flow pattern improvement around the structures is creating slot in structure to reduce maximum scour depth around the structures tips. In order to achieve the purposes of present study a rectangular slot (with opening percent equal to 10 percent of the effective surface vane and the location of the slot is parallel to the chord) has been created in the bank attached triangular vane. Then the effect of slot on bed topography was analyzed at different angles and hydraulic conditions (0.287, 0.304 and 0.322). Results showed that the average reduction of maximum scour depth by means of slot at the angles of 23, 30, 40 and 60 degrees have been 70, 20, 17 and 54 percent, respectively. Also the created slot in the vane caused the maximum scour depth to form away from the outer bank. By increasing the Froude number, the maximum scour depth has increased at sample-slotted vanes.