Scour geometry at long skewed bridge piers under shallow water flows

Experiments were conducted to investigate the geometry of the scour hole and sediment ridge at long skewed bridge piers under shallow water flows. The study aimed to investigate the influence of long pier orientations on cohesionless bed sediment under uniform flows occurring in shallow water regions such as rivers and estuaries. Experiments were conducted on long rectangular skewed piers with the pier Reynolds number (Re_p) within the range 2·2 × 10⁴ ≤ Re_p ≤ 2·1 × 10⁵. The observations showed that the geometric dimensions of the equilibrium scour hole and sediment ridge length increased steadily with the angle of attack (α). The experimental evidence also revealed that Re_p had a parabolic relationship with the equilibrium dimensionless scour hole width (W_s/B_α) and the equilibrium dimensionless sediment ridge length (L_r/B_α) at long skewed piers. The dimensionless expressions were compared with the most accurate relationship found in the literature, as applied to the compiled database. The mean error was reduced from 44·66% to 10·74%. The results also demonstrated that the scouring volume (V_s) was much higher than the sediment ridge volumes (V_d) as the skewness of a long pier increased.