Proceedings: The Second International Conference on Building Energy and Environment 2012 1055 Topic 11. Computer tools and experimental techniques for assessment of building energy and built environment Validation of Three Dimensional Fast Fluid Dynamics for Indoor Airflow Simulations Mingang Jin 1 , Wangda Zuo 2 , and Qingyan Chen 1* 1 School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA 2 Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA * Corresponding email: yanchen@purdue.edu Keywords: Fast fluid dynamics; Building airflow simulations; Boundary condition SUMMARY Real time simulations of airflow in buildings could provide better opportunities for designing and controlling indoor environment. Fast Fluid Dynamics (FFD) could be potentially used for real-time indoor airflow simulations. This study developed two-dimensional Fast Fluid Dynamics (2D FFD) into three-dimensional Fast Fluid Dynamics (3D FFD). The implementation of boundary condition at outlet was improved with local mass conservation method, and a near-wall treatment for Semi-Lagrangian scheme was applied to avoid having departure points located outside the boundary. This study tested 3D FFD with three cases of indoor airflows with increasing complexity. Compared with the high quality experimental data, the numerical results showed that 3D FFD could capture general airflow features and provide reliable and accurate simulations for airflows in buildings. The computing speed was about 15 times faster than CFD. INTRODUCTION Real time simulations of airflow in buildings could provide better opportunities in designing and controlling indoor environment. Although Computational Fluid Dynamics (CFD) has the potential to be used for the airflow simulations, CFD is too slow with the present computing power in most of the design firms (Zhai and Chen 2006; Chen 2009). On the other hand, multi-zone network models could significantly decrease the computing time so that real time or faster-than-real-time simulations are possible. But it might not be valid for large indoor spaces with stratified ventilation systems (Wang and Chen 2008), and it also uses only one node for a room that provides insufficient information of the micro environment. As an intermediate approach between computational fluid dynamics (CFD) and multi-zone model, fast fluid dynamics (FFD) can achieve informative airflow simulations with fast speed so that it has the potential to perform real-time indoor airflow simulations. Zuo and Chen (2009) developed a two-dimensional Fast Fluid Dynamics (2D FFD) for airflow simulations in buildings. Their results show that the computing speed was 50 times faster than CFD and real- time simulation of indoor airflow seems possible. Although the results were not as accurate as those of CFD, they were much better than those produced by the multi-zone model. However, flows in buildings are complex and always three dimensional (Zhai et al. 2007). In order to capture the characteristics of the three-dimensional airflows, it is necessary to extend