A Semi‐Analytical Model for Predicting the Depth‐Averaged Maximum Longitudinal Velocity in Fully Ice‐Covered Confluences

At river confluences, the complex hydrodynamics result in significant alterations to flow structures, and the maximum velocity zone serves as one of the primary drivers of pollutant transport and riverbed erosion. This study investigates maximum longitudinal velocity formation in fully ice-covered confluences, statistically validating the substitution of depth-averaged maximum longitudinal velocity at the widest recirculation section for depth-averaged maximum longitudinal velocity. In this study, a semi-analytical model is developed to address transitional shear layer modes: (a) wake mode employing dual control volumes, and (b) mixing layer mode treating converging flow as a single control volume. The momentum equation incorporating secondary flow effects predicts maximum depth-averaged velocities, verified against 3D simulations and experimental data with mean errors below 0.42%. Results confirm both models accurately predict velocities within their respective flow regimes, providing the first mechanistic framework for ice-covered confluence hydrodynamics.