An SPH-based mass transfer model for simulating hydraulic characteristics and mass transfer process of dammed rivers

Abstract

Aerated flow characterized by complex mass transfer processes with multiple hydraulic properties is a common enviro-hydraulics phenomenon, which have a variety of profound effects on aquatic ecosystems and the environment. Accurate prediction of the mass transfer process between air and water is crucial to manage the water ecosystem. In this research, an improved two-phase mass transfer smoothed particle hydrodynamics (ITMT-SPH) model is developed with considering the inherent hydrodynamic equations and transport equations to investigate multiple key factors that have ecological implications such as DO (dissolved oxygen) concentration and TDG (total dissolved gas) level. The established model can eliminate the effects of phase separation and non-physical voids for conventional SPH models, which performs better than conventional grid-based methods in terms of prediction accuracy of hydraulic calculation. In addition, to improve the prediction accuracy of mass transfer calculation, experimental and observed field data from a physical model and a practical project are used to calibrate the source parameter of transport equations. Then, a physical model of Songta Hydropower Station (1:80) is established to simulate DO concentration. At the same time, the practical project of Tongjiezi Hydropower Station is used to explore dynamics of TDG level. Simulation results show that ITMT-SPH can simulate ecological indicators of the aerated flow well. The maximum relative error of DO deficit recovery rate between simulation and experiment is 7.8% downstream of dam of Songta physical model. The predicted result of TDG level downstream of Second Dam is 130–148% for Tongjiezi Project, which is close to the monitoring result (138%). This work provides an important theoretical and technical support for the application of ITMT-SPH model to accurately simulate ecological indicators in the ecosystem management.