Mixing and chemical reaction at high Schmidt number near turbulent/nonturbulent interface in planar liquid jet

T. Watanabe, T. Naito, Y. Sakai, K. Nagata, Y. Ito
Mixing and chemical reaction at high Schmidt number near turbulent/nonturbulent interface in planar liquid jet
Physics of Fluids 27 035114 2015

This article may be found at https://doi.org/10.1063/1.4915510.

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Abstract

This study investigates the mixing of reactive species at a high Schmidt number (Sc ≈ 600) near the turbulent/nonturbulent (T/NT) interface in a planar liquid jet with a chemical reaction A + B → R. Reactants A and B are supplied from the jet and ambient flows, respectively. An I-type hot-film probe and optical fiber probe are used for the simultaneous measurements of the streamwise velocity, mixture fraction, and concentrations of all reactive species and for detecting the T/NT interface. Statistics conditioned on the time elapsed after interface detection are analyzed. The conditional mean mixture fraction and concentrations change sharply near the interface. The widths of these changes are independent of the chemical species. The conditional statistics reveal the dependence of the chemical reaction on the interface orientation. The segregation intensity near the interface shows that the mixing state of the two reactants also depends on the interface orientation. However, the large reaction rate near the interface is related to the large concentration of reactant A rather than the mixing state, because reactant A supplied from the jet tends to be deficient near the interface. Near the interface where the reaction rate is large, the concentration of the chemical product is also large. The difference in the product concentration between the different interface orientations is larger for the infinitely fast reaction (as investigated by using the equilibrium limit) than the finite Damköhler number case, and the dependence of the chemical reaction on the interface orientation is expected to be significant for a fast chemical reaction.

日本語訳 (DeepL翻訳)

平面液体噴流の乱流・非乱流界面近傍における高シュミット数域での混合と化学反応

本研究では，化学反応 A + B → R を伴う平面液体噴流の乱流・非乱流界面付近の高シュミット数 (Sc ≈ 600) における反応種の混合を調査した．I 型ホットフィルムプローブと光ファイバープローブを用いて，流速，混合比率，全反応種の濃度を同時計測し，T/NT 界面の検出を行った．界面検出後の経過時間で条件付けした統計量を解析した。条件付き平均混合比率と濃度は界面近傍で急激に変化した。これらの変化の幅は化学種に依存しない。条件付き統計量から、化学反応の界面方向への依存性が明らかになった。界面近傍の分離度から、2つの反応物の混合状態も界面方位に依存することがわかった。しかし、界面付近で反応速度が大きいのは、混合状態よりも反応物Aの濃度が大きいことに関係しており、噴流から供給された反応物Aは界面付近で不足する傾向があるためである。反応速度が大きい界面付近では、化学生成物の濃度も大きくなる。界面方向の違いによる生成物濃度の差は、有限ダムケーラー数の場合よりも無限高速反応（平衡極限を用いて調べた）の方が大きく、速い化学反応では界面方向への依存性が大きいことが予想される。

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