Simulation of marine thermal discharges using dynamically coupled near and far field models

Xiaoli Chen, Qiang Zhang, Yijun Zhao, Li Zeng, Haiwen Zhang

Thursday 2 july 2015

13:00 - 13:03h at Asia (level 0)

Themes: (T) Hydro-environment, (ST) Impacts of pollutants on the water environment, Poster pitches

Parallel session: Poster pitches: 11G. Environment - Impact

Thermal water discharged from power plants may cause pollution on the receiving water body. For the environmental risk management it’s very important to assess the impact of the heated water from the outfalls with a wide range of ambient conditions In order to accurately predict the dispersion of the thermal discharges, it is important that the assessment models can simulate the hydrodynamic characteristics both the near field and the far field. Since the dispersion process in near and far field has large disparity of time and length scales, it is difficult and time consuming for a single model to catch the mixing features from the near field to the far field at the same time. The alternative approach to use coupled near field and far field models have been explored in several studied. However, the coupling methods still need more effective verification for practical use In this paper, the CORMIX near field model and the Delft3D far field model is coupled to model the dispersion of thermal discharges from a planned nuclear power plant into sea. The Delft3D-Flow model is used to predict the ambient currents and temperature, which provide input parameters for the near field model Cormix. Then Cormix is used to predict the mixing process caused by the initial jets and buoyancy in the near field. The DESA method is used to corporate the near field results into the far field model. The simulated vertical distribution of temperate in certain points around the outfall is compared to a scaled physical model of the thermal discharge area. The simulated results show good agreement with the physical model. The results show the mixing induced by the buoyant jet in the near field is well modeled. The cleaning area of the heated pattern is also compared to the physical model result and shows more close to the physical model than the result by the Delft3D alone. This work indicates the coupling method is powerful to improve the accuracy of the far field CFD model and hopeful in practical application to the thermal impact assessment.