Predicting Wind Damage in a City During a Typhoon: A Meteorological Model/LES Approach

The frequency of intense typhoon landfalls is rising in many parts of the world, heightening the likelihood of urban areas facing high wind speeds, previously considered exceedingly rare.

This emphasizes the need to verify the wind safety of each city in such extreme weather conditions, considering their diverse geometries resulting from the unique developmental histories and ways of living.

To achieve this goal, this study utilizes the meteorological model/LES hybrid method to replicate wind characteristics of typhoons, including distinctive vertical profiles, fluctuations in wind speed and direction originating from the coherent structure, and non-stationarity. An inflow wind emulating the strong typhoon Hagibis (2019) approaching Tokyo was generated.

Subsequently, an LES calculation of an actual urban area with buildings and topography over a wide area of 6km*3km was performed using the numerical fluid dynamics solver CUBE specifically designed for large-scale parallel computing by RIKEN R-CCS on the supercomputer Fugaku. Furthermore, a detailed analysis of the urban space with a sub-meter resolution for the central area was carried out.

The study assessed the risk distribution in the city arising from peak wind speeds in the near-ground region, while also estimating the potential building damage caused by the pressure acting upon buildings in the target area. The quantitative risk potential was analyzed by considering the concept of ensemble analysis.