Numerical modeling of two-dimensional hydrodynamics in an artificial chute cutoff under different hydrologic conditions

Abstract

Chute cutoff represents a significant geomorphic event in the evolution of meandering rivers. Following the chute cutoff, channel adjustments occur rapidly. Therefore, investigating the interaction between the flow dynamics and channel morphology is relatively challenging. However, numerical simulations provide enhanced insights into the hydrodynamic characteristics of artificial chute cutoff. In the initial year of an artificial chute cutoff evolution in the Ningxia section of the Yellow River, we collected data on the channel topography and three-dimensional flow velocity. These measurements were utilized to calibrate the established two dimensional mathematical model and explore the impacts of different hydrological conditions on the hydrodynamics of the chute channel after the artificial cutoff. The simulation results revealed the complexity of the two-dimensional flow field within the artificial chute cutoff characterized by several regions of flow separation and recirculation zones, which was related to chute channel topography and boundary conditions. These recirculation zones varied with the inlet flow. Across the three discharges, most of the flow remained concentrated in the main channel. At higher discharges increasing the water levels, the floodplain became inundated, and a shear layer between the main channel and floodplain emerged. This study presented a detailed depiction of the flow structure within artificial chute cutoff under diverse river geomorphological and hydrological conditions. This research can bridge knowledge gaps regarding chute cutoffs in the upper reaches of the Yellow River, contributing to the improvement of conceptual models concerning chute cutoff phenomena.