11:45 AM - 12:00 PM
[AAS03-11] Exploring Fundamental Turbulent Scales over the Tokyo Bay area under extreme and calm weather scenarios using a computational fluid dynamics model
★Invited Papers
Keywords:LES, Urban atmosphere, small-scale turbulence, extreme weather
In urban environments, turbulent scales ranging from small-scale turbulent activities near the surface to mesoscale atmospheric circulation patterns exert substantial influence over energy transfer and dissipation within the atmosphere. This leads to distinctive energy cascades over urban regions. For weather predictions, it is crucial to provide detailed local forecasts of wind patterns. Current weather prediction models often rely on assumptions based on mean flow characteristics to estimate local wind conditions. A Large Eddy Simulation (LES) can improve these predictions by providing detailed information on the range of length scales, velocity scales, and time scales present in the urban flow field. Our study aims to model complex urban geometry's impact on the urban flow field by utilizing CUBE LES in an Immersed Boundary Method (IBM) approach. We investigated LES simulations under extreme and calm wind scenarios over the Tokyo Bay area building atmosphere at 5 m resolution. We dissected turbulent kinetic energy (TKE) into different spatial and temporal scales within urban contexts and investigated scales and locations over urban areas where turbulent energy transfer and dissipation mechanisms predominate. Small-scale regions with larger Raynold’s stress were found to correspond to effective turbulent energy transport. Further, a 3D TKE budget analysis was used to identify regions for turbulent and dispersive shear productions that are involved in turbulent and dispersive transport. Specifically, we could tag TKE scales over the Tokyo Bay urban region where turbulent transport plays a role in scale interactions, which could enhance our capacity for severe weather prediction in urban environments.