Bahrami Mahdi


Effect of angel of attack on scour depth at rounded nosed rectangular piers with slot

Student Name

Mahdi Bahrami



Mohammad Reza Chamani
(Assist. Prof._Civil Engineering Department_Isfahan University of Technology)

Manouchehr Heidarpour
(Assist. Prof._Agriculture College_Isfahan University of Technology)









Scouring is an important reason of demolition of bridge piers. Recognition and forecasting scouring in the designs of bridge piers is very essential. There are different procedures to control the amount of scouring. Slotting the piers to prevent scouring is one of the proposed methods.

In this work, effects of slot at different angels of attack were studied. Experiments were carried out in Hydraulic Laboratory of Civil Engineering, Department of Isfahan University of Technology, Iran. Two rectangular pier models with length to width ratio of 2 were used. Width and height of slots were selected four and two times of diameters of piers, respectively. The study was confined to clear water and the slots were located at the bottom of the piers. The experiments established on the slotted pier with there different discharges (20, 35, 45 Lit/s) and under four different angels of attack. Then, piers (no slot) with the same condition of slotted pier were used. Altogether, 24 experiments were performed.

In the slotted pier, it had been seen that down flow interferences with the flow passing through slot. It is found that scouring depth is independent of the discharge. Changing the angel of attack from 0 to 5 degree and from 10 to 15 have more effects on scouring depth. At equilibrium time, the percent of depth reduction of scouring at angel of 0, 5, 10 and 15, is 4.8, 7.9, 10.3 and 14.5, percent, respectively. A long time experimental (10 days) is performed to record changes in the profile of channel-bed.