PRESSURE BOUNDARY CONDITIONS IN MULTI-ZONE AND CFD PROGRAM COUPLING
Zhiqiang (John) Zhai, Yang Gao, Qingyan (Yan) Chen
Multi-zone and CFD airflow models are two important tools for the study of indoor environmental quality. The coupling of these two programs can provide a complementary and thus more accurate prediction of airflow in buildings with an acceptable computing cost. This paper reports the process to couple a multi-zone and a CFD program through pressure boundary conditions at room openings. The study developed a new algorithm to handle pressure boundary conditions in CFD. The algorithm allows the specification of a static or total pressure condition for a particular opening in CFD. It can automatically determine whether the pressure should be treated as total pressure (inflow) or static pressure (outflow) based on whether the airflow enters or leaves the space. To achieve a stable solution during the iterative calculation, special numerical relaxation methods have been used in the implementation of pressure boundary conditions. The validation and application studies show that the pressure boundary treatments and the coupling algorithm are sound.
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