Experimental verification of small-scale universality in turbulent mixing of high Schmidt number scalar

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03851
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Okayama University of Science (2023); Nagoya University (2021-2022)
• Principal Investigator: Iwano Koji 岡山理科大学, 工学部, 准教授 (20750285)
• Co-Investigator(Kenkyū-buntansha): 酒井 康彦 公益財団法人名古屋産業科学研究所, 研究部, 上席研究員 (20162274) ; 伊藤 靖仁 名古屋大学, 工学研究科, 教授 (40346078)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 乱流物質混合 / 高シュミット数 / LIF濃度計測 / 微小スケール普遍性 / 乱流モデル

Outline of Final Research Achievements

In this study, we investigated the small-scale characteristics of concentration fluctuations of a high Schmidt number (approximately 3500) substance in turbulent jet and grid turbulence fields using a fiber-optic concentration measurement probe capable of measuring fluorescence dye concentration fluctuations in the liquid phase with extremely high spatial and temporal resolution. As a result, it was found that in both flow fields, when the initial Reynolds number is low, the gradient of the concentration fluctuation spectrum in the viscous-convective range deviates significantly from the value of -1 predicted by turbulent statistical theory. On the other hand, the spectral shape in the viscous-diffusive range was found to be nearly consistent across all experiments, regardless of Reynolds number or flow field, confirming its universality.

Free Research Field

流体工学

Academic Significance and Societal Importance of the Research Achievements

乱流中で高シュミット数物質が混合されると，微小スケールには流れ場によらない普遍的な濃度揺らぎの構造が存在すると乱流統計理論により予測されている．しかし，その予測の正しさはまだ十分に確認されていない．本研究では，世界で初めて微小スケールの濃度揺らぎを実験的に測定し，乱流の状態が物質濃度場の混合状態にどのように影響を与えるかを明らかにした．この成果は，乱流統計理論の改良や，現実の化学反応装置の設計などに用いられるCFDモデルの精度向上に大きく寄与するものである．