- 著者
- Tetsuya Takemi Toshiya Yoshida Shota Yamasaki Kentaro Hase
- 出版者
- Meteorological Society of Japan
- 雑誌
- SOLA (ISSN:13496476)
- 巻号頁・発行日
- vol.15, pp.22-27, 2019 (Released:2019-02-06)
- 参考文献数
- 27
- 被引用文献数
- 25
An intense tropical cyclone, Typhoon Jebi (2018), landed the central part of Japan and caused severe damages. Quantitative assessment of strong winds in urban districts under typhoon conditions is important to understand the underlying risks. As a preliminary study, we investigate the influences of densely built urban environments on the occurrence of wind gusts in an urban district of Osaka City during Typhoon Jebi by merging mesoscale meteorological and building-resolving large-eddy simulations (LES). With the successful reproduction of the track and intensity of the typhoon in meteorological simulations, the simulated winds at the boundary-layer top of the LES model are used to quantitatively estimate the wind gusts in the urban district. The maximum wind gust in the analysis area of Osaka was estimated as 60-70 m s−1, which is comparable to the wind speed at the height of about 300 m.
- 著者
- Toshiya Yoshida Tetsuya Takemi
- 出版者
- Meteorological Society of Japan
- 雑誌
- SOLA (ISSN:13496476)
- 巻号頁・発行日
- vol.14, pp.174-178, 2018 (Released:2018-11-18)
- 参考文献数
- 17
- 被引用文献数
- 9
Effects of obstacle-height variability on mixing length and dispersive stress are investigated by conducting large-eddy simulations of airflows over arrays of roughness obstacles with variable height. We evaluate differences among three simulations of flows over obstacles with no, moderate, and high obstacle-height variability. Within the canopies, effective mixing length shows one local maximum and minimum in the simulation with no obstacle-height variability but two maxima and minima in the simulations with obstacle-height variability. The number of the local maxima and minima corresponds to that of the shear layers seen at the heights of obstacle tops. Enhanced dispersive stress appears within the canopy between the heights of the lower- and higher-obstacle tops in the simulations with obstacle-height variability. Particularly in the simulations with high obstacle-height variability, the magnitude of dispersive stress becomes comparable to that of the Reynolds stress at the height of the lower-obstacle top. These results suggest that actual urban areas with high building-height variability should significantly affect properties of mixing length and dispersive stress.