Hydrodynamic Simulation in Tidal Rivers Using Fourier Series

Abstract

One-dimensional (1D) hydrodynamic models based on the Saint-Venant equations (the SVN model) have been extensively used for flow simulation in tidal rivers. In rivers with significant tidal effects, the inconsistencies between actual flow characteristics and simplifying assumptions that the Saint-Venant equations are derived based on can introduce unignorable errors into the application of the SVN model. To reduce the errors contributed by the factors the SVN model can not completely account for, such as the tidal effect, an approach of incorporating a function into the calculated velocity by the SVN model was proposed in this study. Fourier series was employed to construct the function. By combining the proposed approach with the flow continuity equation, a 1D hydrodynamic model (the FSV model) was constructed to improve the performance of the SVN model in tidal rivers. The simulation results in the tidal reaches of the Qiantang River and the Changjiang River show that the FSV model performs better than the SVN model alone. It indicates that the proposed approach is reasonable and effective to reduce the errors due to the factors the SVN model can not completely considered in applications.