Transport characteristics of reactive scalar fields in a planar jet under the influence of reversible elementary reactions

doi:10.11949/0438-1157.20250536

Abstract

Abstract:

Quasi-direct numerical simulations (Q-DNS) were performed using the OpenFOAM platform to investigate planar jets involving isothermal reversible elementary reactions (A+BC). A Lagrange coordinate system was established at the turbulent/non-turbulent interface (T/NTI) to analyze the production, transport, and consumption processes of the chemical species near the interface under four working conditions characterized by different ratios of the reverse-to-forward reaction rate constants (n=0, 0.1, 1, 10). As n increases, chemical reactions near the T/NTI gradually approach equilibrium. At n=10, the contribution of chemical reaction source terms to the unsteady terms of reactants A and B becomes negligible, whereas the positive correlation between the unsteady term of product C and chemical reaction source terms significantly enhances with increasing n. At the irrotational boundary of T/NTI, the diffusive fluxes of components A and C surpass their fluxes by relative motions, whereas the diffusive flux of component B constitutes a smaller proportion of the total flux. The ratio of the diffusion flux to the relative motion flux of each component decreases to varying degrees with increasing n.

Key words: planar jet, reversible elementary reaction, quasi-direct numerical simulation, scalar transport, turbulent/non-turbulent interface, Lagrange coordinate system

摘要：

基于OpenFOAM平台对含有等温可逆基元反应（A+BC）的平面射流进行准直接数值模拟（quasi-direct numerical simulation，Q-DNS）。通过在湍流/非湍流界面（turbulent/non-turbulent interface，T/NTI）上建立拉格朗日坐标系，探究了逆向与正向反应速率常数比值n=0、0.1、1、10的四种工况下各组分在界面附近的产生、输运和消耗过程。随着n的增大，T/NTI附近的化学反应逐渐接近平衡态。当n=10时，化学反应源项对反应物A、B非稳态项的贡献可以忽略。产物C非稳态项与化学反应源项之间的正相关性随着n的增大而显著增强。在T/NTI的无旋边界上，组分A、C的扩散通量高于相对运动通量，组分B的扩散通量在总通量中占比较小，各组分扩散通量与相对运动通量的比例随着n的增大存在不同程度的降低。

关键词: 平面射流, 可逆基元反应, 准直接数值模拟, 标量输运, 湍流/非湍流界面, 拉格朗日坐标系

CLC Number:

O 358

Yifan PEI, Yuanliang XIE, Yi ZHOU, Xuelu XIONG. Transport characteristics of reactive scalar fields in a planar jet under the influence of reversible elementary reactions[J]. CIESC Journal, 2025, 76(12): 6314-6327.

裴依凡, 谢远亮, 周毅, 熊雪露. 可逆基元反应影响下平面射流中反应性标量场输运特性[J]. 化工学报, 2025, 76(12): 6314-6327.

Figures/Tables 21

Fig.1 Schematic diagram of the flow field and coordinate system

Table 1 Numerical parameters and node configuration of the reactive planar jet

$n$	$R e d$	$S c$	$U A / U J$	$Γ A 0 / Γ B 0$	$D a$	$L x / d$	$L y / d$	$L z / d$	$N x$	$N y$	$N z$
0	2000	0.71	0.1	2	1	30	23	8	701	659	120
0.1	2000	0.71	0.1	2	1	30	23	8	701	659	120
1	2000	0.71	0.1	2	1	30	23	8	701	659	120
10	2000	0.71	0.1	2	1	30	23	8	701	659	120

Table 1 Numerical parameters and node configuration of the reactive planar jet

$n$	$R e d$	$S c$	$U A / U J$	$Γ A 0 / Γ B 0$	$D a$	$L x / d$	$L y / d$	$L z / d$	$N x$	$N y$	$N z$
0	2000	0.71	0.1	2	1	30	23	8	701	659	120
0.1	2000	0.71	0.1	2	1	30	23	8	701	659	120
1	2000	0.71	0.1	2	1	30	23	8	701	659	120
10	2000	0.71	0.1	2	1	30	23	8	701	659	120

Fig.2 Wall-normal distributions of dimensionless mean streamwise velocity and its fluctuations

Fig.3 Characteristics of mean mixture fraction distribution

Fig.4 Dependence curve of turbulent region volume fraction on the interface detection threshold

Fig.5 Schematic diagram of the local coordinate system

Fig.6 Conditional statistics of vorticity ω near T/NTI at

Fig.7 Conditional statistics of dimensionless species concentrations near T/NTI at x/d=25

Fig.8 Gradient evolution of conditionally averaged species concentration along local coordinates near T/NTI at x/d=25

Fig.9 Probability density function (pdf) of the irrotational boundary motion velocity detected at x/d=25

Fig.10 Schematic diagram of the relationship between absolute and Lagrange coordinate systems

Fig.11 Conditional mean values of all terms in the species A concentration transport equation under Lagrange coordinates at x/d=25

Fig.12 Conditional mean values of all terms in the species B concentration transport equation under Lagrange coordinates at x/d=25

Fig.13 Conditional mean values of all terms in the species C concentration transport equation under Lagrange coordinates at x/d=25

Fig.14 Statistics of conditionally averaged correlation coefficients among terms in the scalar transport equation for species C under Lagrange coordinates at x/d=25

Fig.15 Mean relative transport flux of species across the irrotational boundary at x/d=25

Fig.16 Probability density distribution of θα detected at the interface (x/d=25)

Fig.17 Normalized mean species diffusion flux through the irrotational boundary at x/d=25

Fig.18 Ratio of mean diffusive flux to absolute mean relative transport flux of species across the irrotational boundary at

Fig.19 Schematic diagram of scalar concentration correlation calculation between two points

Fig.20 Evolution of the correlation coefficient of species A concentration in different areas near the interface

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