Hydrodynamic Characteristics of Flow in a Strongly Curved Channel with Gravel Beds

This study experimentally and numerically investigated the hydrodynamic characteristics of a 180° curved open channel over rough bed under condition constant downstream water depth. Three different sizes particles (the small, middle big cases based upon grain size diameter D50) were selected for flume tests. Three-dimensional instantaneous velocities obtained by acoustic Doppler velocimeter (ADV) used to analyze characteristics. Additionally, Renormalization-Group (RNG) turbulence model was employed numerical simulations. Experimental results show that strengthens increases turbulent kinetic energy along channels. The power spectra longitudinal velocity fluctuation satisfy classic Kolmogorov ?5/3 law in inertial subrange, existence shortens subrange causes flow reach viscous dissipation range advance. contributions sweeps ejections are more important than those outward inward interactions case. Flow-3D adopted simulate patterns on two settings with same surface roughness (skin drag) but shapes (form drag): one is covered thick bottom sediment layers part case) as experimental condition, other uniform entire (called case_flat only simulations). Numerical simulations reveal secondary confined near-bed area intensity improved both cases, possibly causing serious erosion channel. In addition, sediments case), i.e., larger form drag, can enhance strength near regions, enlarge transverse flow, delay shifting core region maximum towards concave bank.