Prediction and evaluation of high-risk low-probability phenomena in an urban canopy space

2020 Fiscal Year Final Research Report

• Project/Area Number: 17H04946
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Architectural environment/Equipment
• Research Institution: Kyushu University
• Principal Investigator: Ikegaya Naoki 九州大学, 総合理工学研究院, 准教授 (70628213)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: 都市キャノピー / 近赤外分光法 / 屋外実験 / 低頻度高リスク事象

Outline of Final Research Achievements

In this study, we developed a new dynamic flux system to measure and estimate evaporation flux. Secondly, the field measurements were conducted to evaluate turbulent velocity fields within urban canopy layer in a field measurement site. Lastly, we conduced both numerical and experimental studies to build datasets to evaluate rare but high-risk events indoor and outdoor areas. By developing the system of the evaporation flux using infra-red spectroscopy, we successfully determined the mass transfer coefficient from a surface behind a building obstacles. This system help determining the transfer coefficient. In addition, we also proposed evaluating methods of rate but high-risk event within an urban area using both wind-tunnel experiment and field measurement fo the turbulent flow fields within urban areas. The proposed method enables to determine the rate wind speed magnitude and frequency based on the probability density distribution.

Free Research Field

環境工学

Academic Significance and Societal Importance of the Research Achievements

非接触フラックスシステムの開発において，従来の方法では困難であった非接触計測を可能にしたことによって，今後の物質輸送係数取得実験の発展に資する新しいシステムを提案し，構築することができた．近赤外分光法を風洞実験に導入した例はこれまでになく，関連分野に新しい計測手法を導入することに成功した波及効果の大きな成果である．また，風洞実験や数値流体解析による瞬間風速のデータベースから得られた風速場の確率性状の分析によって，室内外を問わず，瞬間的に発生する強風や弱風を評価する上で重要となる風速の確率分布に関する知見を取得した．