Accelerating fast fluid dynamics with a coarse-grid projection scheme

Fast fluid dynamics is an intermediate model that can provide fast and informative building airflow simulations. Although reasonably good simulation accuracy is important for fast fluid dynamics, computational efficiency is the primary concern, and it is necessary to further increase fast fluid dynamics speed. Because the most time-consuming part of fast fluid dynamics is solving the stiff pressure equation, this study proposed the application of a coarse-grid projection scheme, which solves the momentum equation on the fine grid level and the pressure equation on the coarse grid level. Therefore, appropriate approaches for mapping velocity and pressure information between different grid levels were investigated in this study. To evaluate the accuracy and computational efficiency of fast fluid dynamics with the coarse-grid projection scheme in simulating building airflows, this study tested it with building airflows of varying complexity. The results showed that the coarse-grid projection scheme would not have a negative impact on the accuracy of fast fluid dynamics in the simulation of building airflows, and it could significantly reduce the fluctuations that occur within the simulations. The coarse-grid projection scheme was able to accelerate fast fluid dynamics by approximately 1.5 times, and thus fast fluid dynamics with the coarse-grid projection scheme achieved a computing speed that was 30 to 50 times faster than computational fluid dynamics models.