Theoretical study on identifying occurrence mechanisms of rare wind events within urban canopy layer

2020 Fiscal Year Final Research Report

• Project/Area Number: 17KK0117
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• 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): 2018 – 2020
• Keywords: 境界層 / 都市キャノピー / 運動量フラックス / 乱流構造 / 輸送係数

Outline of Final Research Achievements

In this study, we clarify the fundamental factors determining low frequency but high-risk wind gust phenomena occurring within an urban boundary layer. Based on the base theme for this study, we had opportunities to work with two international researchers dealing with turbulent phenomena within atmospheric boundary layers. In commonwealth Scientific Industrial Research Organisation, we theoretically derived an integral equation explaining the momentum budget mechanics which help understand the key reason of gust events within an urban boundary layer. In National Center for Atmospheric Research, we thoroughly reviewed previous transfer model and our results to summarize the relationship between the transfer coefficient of momentum and scalar quantities and considering length scale. We concluded that our study contributes for establishing the models for gust predictions and transfer coefficients.

Free Research Field

環境工学

Academic Significance and Societal Importance of the Research Achievements

本課題は，都市乱流境界層を対象として，都市域における低頻度高リスク環境の発生機構の解明および都市乱流境界層における統計量普遍則の追求を試みたものである．応用的かつ実学的な研究が先行する日本のアカデミアに対して，本課題による国際共同研究を実施したことによって，先行研究として進んでいる植生キャノピーの知見や屋外実験における物質輸送係数推定の結果から，理論的論考よるモデリングに資する基礎的知見を得ることができた．特に人々や建物などか関連する建築環境の分野のよう応用研究が重要視されつつある分野に対して，流体力学的な基礎的知見を導入できたことの分野に対する波及効果は極めて大きなものであると考えている．