CFD modeling as a tool for assessing outdoor thermal comfort conditions in urban settings in hot arid climates

Computational Fluid Dynamics (CFD) is increasingly being used as a tool for the analysis of outdoor and indoor air flow and thermal conditions. With over half of the world's population living in cities, rapid population growth and dense urban development has increasingly led to the phenomenon of urban heat islands, which in turn contribute to the deteriorating air quality and thermal discomfort in outdoor urban public spaces. In hot arid countries, changes in the characteristics of the urban microclimate are observed due to dense urbanization, high-rise buildings, and industrialization of the building processes and materials, leading to a reduction in thermal comfort in outdoor and indoor spaces. This research highlights the potential of adopting Computational Fluid Dynamics (CFD) as a simulation technique to investigate the complex fluid flow patterns in urban thermal environments, and investigates methods intended to prolong thermal comfort in public places. It discusses the advantages and limitations of CFD tools and the procedural guidelines for conducting CFD simulation. This paper also gives examples of case studies of CFD assessment for indoor and outdoor urban environments, and the practical use of RANS solver in comparison with LES, DES, and DNS models. Finally the paper highlights a case study of a CFD simulation using a RANS turbulence model of an urban street in the hot arid city of Madinah, Saudi Arabia.