Investigation on the Effects of Distance-to-Diameter Ratio of piers on the Hydraulic Characteristics in a 90° Open Channel Bend

• Published in: Journal of Applied Science and Engineering Vol. 29; no. 2; pp. 393 - 400
• Main Authors: Xi Shi, Tingting Song, Hui Chen, Hu Tao, Yuanshun Huo
• Format: Journal Article
• Language: English
• Published: Tamkang University Press 2026
• Subjects: bend circulation; bend flow characteristics; circular end bridge piers; span-to-diameter ratio; turbulent kinetic energy
• ISSN: 2708-9967; 2708-9975
• DOI: 10.6180/jase.202602_29(2).0014

To investigate the influence of pier spacing on the flow structure in curved channels, a three-dimensional 90° bend model was established. The simulation employed the PISO algorithm coupled with the RNGk − ε turbulence model, along with the Volume of Fluid (VOF) method for free-surface tracking. The flow characteristics under different spacing-to-diameter ratios (s/d = 2, 3, 5) were analyzed. The results indicate that: (1) Along the flow direction, the longitudinal velocity (V^∗_u ) decreases while the transverse velocity (V^∗_v ) increases, and they are complementary to each other. At the convex and concave banks: V^∗_us/d=2 > V^∗_us/d=3 > V^∗_us/d=5, V^∗_vs/d=2 < V^∗_vs/d=3 < V^∗_vs/d=5. (2) Active circulation structures exist in low-velocity areas where flow velocity interacts with circulation patterns. As s/d increases, water flow superposition weakens leading to gradual separation and formation of complete vortex structures. This reduction in water flow turbulence and vortex formation helps mitigate erosion effects on bridge piers. (3) With increasing spacing-to-diameter ratio,Ks/d=5 > Ks/d=3 > Ks/d=2, is observed on both sides of convex and concave regions but opposite along the central axis. Relative turbulent kinetic energy exhibits an inverted "W" shape along the water depth direction on both sides of convex and concave regions while displaying an inverted " S " shape along the central axis.