Numerical simulation and analysis of abrupt pollutants diffusion in Qiantang estuary

In order to study the diffusion and transport characteristics of abrupt pollutants in a macrotidal river and to propose appropriate measures to respond to minimize the impact of pollutants on water quality,Navier-Stokes equations for an incompressible fluid in orthogonal curvilinear co-ordinates under the Boussinnesq assumption were used to numerically simulate the diffusion and transport of abrupt pollutants in Qiantang estuary,and the pollutant dispersion under different runoff were obtained by changing the upper reaches of the boundary is conditions.Results indicate that once Qiantang estuary is contaminated,the pollutants diffuse to downstream under the influence in the run-off,and by the effect of flood current the pollutants also impact the upstream water quality.The pollutant concentration at each contaminated point changes in the opposite way to the corresponding water level fluctuation in each tidal cycle.Increasing the upstream flow can accelerate the pollutants diffusion,it is conducive to reduce the pollutants' impact on water quality at upstream and downstream,and it also favours eliminating the pollutants quickly and achieving water quality safety.