Concentration transport calculations by an original C++ program with intermediate fidelity physics through user-defined buildings with an emphasis on release scenarios in radiological facilities
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The purpose of this dissertation was to develop the C⁺⁺ program Emergency Dose to calculate transport of radionuclides through indoor spaces using intermediate fidelity physics that provides improved spatial heterogeneity over well-mixed models such as MELCOR[trademark] and much lower computation times than CFD codes such as FLUENT[trademark]. Modified potential flow theory, which is an original formulation of potential flow theory with additions of turbulent jet and natural convection approximations, calculates spatially heterogeneous velocity fields that well-mixed models cannot predict. Other original contributions of MPFT are: 1) generation of high fidelity boundary conditions relative to well-mixed-CFD coupling methods (conflation), 2) broadening of potential flow applications to arbitrary indoor spaces previously restricted to specific applications such as exhaust hood studies, and 3) great reduction of computation time relative to CFD codes without total loss of heterogeneity. Additionally, the Lagrangian transport module, which is discussed in Sections 1.3 and 2.4, showcases an ensemble-based formulation thought to be original to interior studies. Velocity and concentration transport benchmarks against analogous formulations in COMSOL[trademark] produced favorable results with discrepancies resulting from the tetrahedral meshing used in COMSOL[trademark] outperforming the Cartesian method used by Emergency Dose. A performance comparison of the concentration transport modules against MELCOR[trademark] showed that Emergency Dose held advantages over the well-mixed model especially in scenarios with many interior partitions and varied source positions. A performance comparison of velocity module against FLUENT[trademark] showed that viscous drag provided the largest error between Emergency Dose and CFD velocity calculations, but that Emergency Dose’s turbulent jets well approximated the corresponding CFD jets. Overall, Emergency Dose was found to provide a viable intermediate solution method for concentration transport with relatively low computation times.