On Characterizing Flow Resistance in a Tidal Reach

Abstract The tidal reaches are characterized by unsteady and non-uniform flow (UNF), which is significantly different from the commonly assumed steady uniform (SUF) in hydraulics. SUF shows invariant temporal spatial characteristics, thus acceleration absent a prismatic channel. However, for UNF, variation of velocity depth both scales causes loss energy, increases resistance. In order to clarify resistance its influencing factors reaches, this study investigates characteristics under UNF conditions. study, typical section Lower Yangtze River (LYR) – Kouanzhi Waterway (KW) was selected as area, where water surface along river course at tide levels, bathymetry multiple cross-sections, distribution cross-sectional were measured detail. Based on these field measurement data, contribution terms energy slope calculated evaluated, decomposing momentum equation. contributing include gradient, local acceleration, convective acceleration. results showed that have substantial impact during specific time periods, found be more significant than findings previous studies. show term except when close zero, throughout flood initial ebb periods. above research great significance investigation mechanisms numerical simulations rivers.