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

Abstract

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 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.

Keywords

• bend flow characteristics
• circular end bridge piers
• span-to-diameter ratio
• bend circulation
• turbulent kinetic energy