報告書番号

V08027

タイトル（和文）

都市キャニオン内の流れと拡散に関する屋外および風洞実験

タイトル（英文）

Field and wind tunnel experiments about flow and dispersion within an urban canyon

概要 （図表や脚注は「報告書全文」に掲載しております）

屋外都市スケールモデルの建物キャニオン内に複数台の高応答性の濃度計および超音波風速温度計を設置し，地表付近から放出されたトレーサガス濃度と風速を同時に計測する屋外実験を行った。また，キャニオン内の瞬時の流れ場をより詳細に検討するため，屋外実験と同様の建物配列を再現した風洞実験を行った。その結果，屋外および風洞実験のいずれにおいても時間平均されたキャニオン内の流れには単一の循環渦が形成されており，キャニオン内の濃度は風下断面に比べて風上断面で高い値を示すことが明らかとなった。キャニオン内の平均濃度は上空の平均風速の増加にともない減少するほか，上空の気流乱れによっても変化し，キャニオン上空の平均風速に加え，気流乱れを考慮することによりキャニオン内の濃度を精度良く予測することができる

概要 （英文）

Field experiments of air flow and pollution dispersion within an urban canyon in the comprehensive outdoor scale model (COSMO) were conducted to investigate the effect of the mean and turbulent flow above the canyon on pollutant dispersion inside the canyon. Tracer gas concentration was measured using fast-response photo ionization detectors at several points on three vertical cross sections of the canyon. Three-dimensional wind velocity components were also simultaneously measured using ultrasonic anemometers within and above the same canyon. To examine the instantaneous flow field within the canyon, a wind tunnel experiment was also conducted, and wind velocities were measured by particle image velocimetry (PIV). Both in the field and the wind tunnel experiments, a stable vortex-type flow was observed in the canyon. The tracer gas from the line source on the ground was carried to the leeward side of the upstream building by the circulation of the vortex and the concentration on the leeward side was much higher than that on the windward side of the downwind building. Pollutant concentrations within the canyon were successfully estimated by considering the external turbulence in addition to the mean wind velocity.

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