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Academic Express | A computationally affordable and reasonably accurate approach for annual outdoor thermal comfort assessment on an hourly basis

Recently, a team led by Associate Professor Dayi Lai from the School of Design at Shanghai Jiao Tong University, in collaboration with Professor Liu Wei from the Tianjin Key Laboratory of Indoor Air Quality Control at Tianjin University, published an academic paper titled "A computably affordable and reasonably accurate approach for annual outdoor thermal comfort assessment on an hourly basis" in Energy and Buildings (IF=6.8, JCR Q1). This paper proposes a year-round hourly simulation method for outdoor thermal comfort based on Fast Fluid Dynamics (FFD), Proper Orthogonal Decomposition (POD) and Reynolds Number Independence (Re-independence). The method is validated and demonstrated using a high-density residential area as an example.

Abstract

The thermal environment and thermal comfort of an outdoor space have large spatial and temporal variations. To provide an overall picture, outdoor thermal comfort (OTC) should be analyzed on a yearly basic with high temporal-spatial resolution. The difficulty of annual OTC evaluation lies in the huge computational cost of wind simulations. Therefore, our study proposed a method to accelerate wind simulations through the use of Fast Fluid Dynamics (FFD), Proper Orthogonal Decomposition (POD) and Reynolds Number Independence (Re-independence). A case study of an actual urban building complex was employed to validate our study by comparing the integrated index Universal Thermal Climate Index (UTCI) results by our method with those by fully-resolved simulations. The average difference of UTCI was just 0.06 ℃, indicating that the accuracy of our method is guaranteed. Besides, it only took 8 hours to complete the OTC assessment of this site with an area of 125,600 m2. The framework proposed in this study can be used to reveal the complete picture of OTC with affordable computational cost and reasonable accuracy.

Keywords: Outdoor thermal comfort; Fast fluid dynamics; Proper orthogonal decomposition; Reynolds number independence; Computational fluid dynamics

Framework for annual outdoor thermal comfort evaluation

​Ratio of hours of different comfort categories in different seasons