A comparative study on the difference of CFD simulations based on a simplified geometry and a more refined BIM based geometry

A strategy of the combination of Computational Fluid Dynamics (CFD) and Building Information Model (BIM) technology was proposed to evaluate the wind environment around a building with complex façades for green building assessment. The Science and Education Building located at the Emerald Lake Campus of the Hefei University of Technology in China was selected as a case study. Two modeling methods, refined modeling by BIM software (BIM model) and traditional simplified modeling by computer aided design software (simplified model, referred to as SM model), were considered. The differences between the CFD results from the two geometry models were carefully examined. Three typical outdoor activity areas were selected to study the wind velocity difference, including the central channel, roof garden, and overhead corridor. The pressure difference between the CFD simulation results of the BIM model and the SM model at the exterior windows of the high-rise building was compared and analyzed. The results show that when a narrow channel is formed between two buildings, the wind velocity of the BIM model at the channel will be significantly lower than that of the SM model. The large “wall-type” components of the building roof will enhance the vortex area. The average pressure difference is greater than 0.5 Pa at the external window of building façades, accounting for up to 39.6%. The maximum pressure difference is as high as 10.13 Pa. The wind velocity difference is as high as 2.65 m/s at the central channel, 4 m/s at the roof garden, and 3.69 m/s at the overhead corridor. These differences will significantly affect the evaluation of the outdoor wind environment in green building assessment.