Urban green space landscape patterns and thermal environment investigations based on computational fluid dynamics

The temperature and velocity fields of five common forms for urban green space patterns in the vertical and horizontal directions have been simulated by computational fluid dynamics (CFD) and remote sensing (RS), in order to study the influence and extent of green space patterns on an urban thermal environment. Based on Thematic Mapper remote sensing images (resolution 30 m) of Taiyuan (111 degree 30' to 113 degree 09'E, 37 degree 27' to 38 degree 25'N) acquired on September 16, 2008, numerical models of plant cover were used within a traditional CFD framework. A typical mathematical model of green space distribution patterns was established. CFD model parameters were modified to improve the accuracy of the simulation using RS technology related to the parameters and results. The results show that the shrub layer has a greater influence than the tree layer in the flow field for the vertical structure of a green space. In order to form good local circulation within the green space, importance is attached to the choice and configuration of the shrub layer. Nevertheless, the cooling effect for the tree layer is more apparent. For appropriate rates of change of green space, the following results can be obtained. A wedge-shaped pattern of green space had the most significant cooling effect in the city, followed by radial and banded patterns. The cooling effect of a green space point pattern was insignificant on the surrounding environment. However, local vorticity in its velocity field was obvious, showing that a green space point pattern had a significant cooling effect within a small area and therefore could be used to improve local microclimates. The cooling effect of a ring-shaped pattern was the weakest. We conclude that it is possible to use CFD numerical simulation technology in the study of urban thermal environments, and additionally, remote sensing technology can be used to modify the parameters needed for CFD. CFD has the advantages of saving time, effort and monetary expense. Also, the complementary application of CFD and remote sensing to thermal environment studies will make the results more accurate and complete. Based on the study results, some corresponding proposals for urban green space planning and construction are posed.