Monsoon Wind Fields in Subtropical High-Density Cities: Lidar Measurements, Clustering Analysis, and Cfd Inflow Boundary Condition

Abstract

Reliable wind profile assessment and modeling are essential for urban wind engineering applications and the  environment, particularly in skyscraper-dominated city centers. This study is based on five months of continuous observations obtained by a high-spatial-resolution LiDAR system deployed in the urban center of Zhuhai City, Guangdong Province. A systematic analysis was conducted on the characteristics of the average wind speed profile in urban centers during the monsoon season. Theoretical models and numerical simulation techniques were employed to analyze the data. First, the K-means clustering method was employed to categorize wind speed profiles during the monsoon period. The elbow rule and principal component analysis were then used to determine the optimal number of clusters, K = 3. The typical wind speed profiles were subsequently divided into patterns A, B, and C. The model fitting effect of various wind speed profiles was then evaluated, and the influence mechanism of atmospheric stability and urban terrain characteristics on the profile shape was revealed. Subsequently, a novel mathematical model of inflow boundary conditions suitable for tropical and subtropical monsoon climates was derived by combining the standard k-ε turbulence model. This model incorporates the complete expression of inflow boundary conditions considering the scale effect. The efficacy of the novel inflow boundary conditions in simulating the equilibrium atmospheric boundary layer(ABL) with self-sustaining properties was validated through a numerical wind tunnel simulation method that incorporated on-site measured data. This novel boundary condition model provides a valuable reference point for research endeavors concerning boundary layer flow in monsoon climates.

Keywords: LiDAR field measurement, wind speed profile, cluster analysis, equilibrium atmospheric boundary layer, inflow boundary conditions