Using Computational Fluid Dynamics Tools to Calculate the Diffusion of Gas and Aerosol Emissions in Conditions of a Complex Terrain
ANSYS FLUENT tools were used as part of a standard turbulence (kε)-model to simulate the air flow around a number of typical obstructions (a 3D cube, a 3D hemisphere, and a 2D hill) which form a potential terrain in the NPP emission spread area and roughly correspond to the geometry of the buildings and structures within this area. For reproducibility, a non-uniform spatial grid is plotted in the computational region which condenses near the obstruction surface and the outer boundaries. The dimensions and the positions of the obstructions were chosen such that to ensure their best possible coincidence with the conditions of the published experiments. The result of modeling the velocity and direction of the air flow as the whole shows a good agreement with the data from the wind tunnel experiments in the areas in front of and over the obstruction, as well as in its aerodynamic shadow. Typical accelerated flow, vortex, and reverse flow areas are reproduced reliably. There are variances observed only in the local heavy turbulence regions in the obstruction’s aerodynamic shadow near the ground surface. All this indicates that it is possible to model in full scale the spread of the NPP emissions taking into account the features of the plant site terrain and the major onsite structures to determine more accurately the personnel and public exposure dose.
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