[A-AS04] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS04-P01] Evaluation of urban wind gusts for thermally-stratified turbulent boundary-layer flows using large-eddy simulation

*Guangdong DUAN¹、Tetsuya Takemi² (1.Dalian Maritime Univ.、2.Kyoto Univ.)

キーワード：Wind hazards, Thermal stratification, Large-eddy simulation, Urban flow

Global warming has intensified thermal-induced urban wind hazards, emphasising the need to understand the intricate coupling of urban topographical indices with wind gusts for improved adaptation to future wind hazards. Using large-eddy simulation (LES), we examine the gustiness factor for wind speed, fluctuations, and higher-order turbulence statistics across a wide range of boundary-layer stabilities: the bulk Richardson number, Rb~[-0.41, 0.82]. Ratios of the proposed gustiness statistics, G, over conventional time-averaged flow and turbulence statistics are maximised for z/H_ave < 1(where H_ave denotes the mean building height). The revealed strong linear scaling of G with the plan-area index (λ_p) for neutral stratification persists for stably- and unstably-stratified flows (R² ~ 0.8). By contrast, non-dimensionalised building height variability, σ_H/H_ave, and the proposed effective frontal-area index, λ_f* = λ_f H_ave/σ_H, are argued to be more appropriate as scaling parameters for G compared to their original forms, σ_H and λ_f. These results should provide further insights into the parameterisation of urban wind hazards for complex urban topographies. These results should provide further insights into the parameterisation of urban wind hazards for complex urban topographies.