Numerical Study of the Slot Width Effect on Flow Pattern Around a Bridge Pier

Using slot in bridge piers is one of the reduction methods of scour depth around them. In this study، the flow field around a cylindrical pier located in a smooth bed with and without slot was simulated using FLOW-3D software. The RNG k-ε turbulence model was used for closing the Navier-Stokes equations. The comparison of the numerical results and laboratory measurements for one bridge pier without slot showed that the model could predict velocity and shear stress parameters with reasonable accuracy. The influence of the slot width on the flow field around bridge pier was then investigated. The formed vortex at downstream of the pier became smaller by increasing slot width. In the largest slot case، this vortex was completely disappeared. Also، by increasing slot width، the value of the maximum velocity occurred adjacent the pier decreased، but its location was fairly constant. Finally، because of the lower reduction of the longitudinal velocity of the flow in the vicinity of the upstream face of the pier for the largest slot، shear stress pattern in this area was similar to that of the upstream area.