Abstract
The scour depth at bridge piers depends on a large number of variables. This study aims at revisiting the influence of rectangular piers' shape on local scouring. The scour around circular and rectangular bridge piers with length to width (L/D) of 1, 3, 4.5, 6, 7.5, and 9 was experimentally and numerically investigated at shallow water conditions (water depth to pier width (h/D) ratio varied from 1.4 to 2.32). Fifty-two experimental runs were carried out with a mobile bed made of non-ripples uniform sand with a median sediment grain size (d50) of 0.6 mm. The results show that L/D would influence the dimensionless scour depth (ys/D). The rectangular pier with L/D of 4.5 had the maximum ys/D and at L/D of 7.5 and 9 the ys/D was highly reduced. The Flow 3D model was used to verify the effect of downflow, shear stress, streamwise velocity and turbulence (energy and intensity) on the ys/D. The numerical results emphasized that the maximum scour would occur in terms of downflow and shear stress at L/D of 4.5. A new empirical equation (R2 = 0.904 and RMSE = 0.238) for predicting the maximum ys/D at rectangular piers was obtained. Compared with the similar formulas in the literature for predicting ys/D, accurate predictions at the rectangular pier with L/D of 1–9 were registered in this study.
•Numerical models around bridge piers investigated using the powerful Flow 3D (v. 11.2) mathematical model tool.•The experiments were conducted in order to determine the maximum scour depth (ys/D) at different pier configurations (circular, square and rectangular with length to width ratio (L/D) of 3, 4.5, 6, 7.5, 9).•The results compared with the experimental data.•The maximum ys/D was found at the location where high downflow, streamwise velocity and shear stress occurred. A new correlation to predict the ys/D with rectangular bridge piers was developed.