反应性射流中湍流/非湍流界面附近标量输运特性
Scalar Transport Characteristics Near the Turbulent/Non-Turbulent Interface in a Reactive Jet Flow
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摘要: 湍流/非湍流界面(turbulent/non-turbulent interface, T/NTI)层分隔开湍流区和非湍流区, 研究T/NTI有利于加深对湍流区和非湍流区之间传质的理解。通过开展射流和环境流间发生二级非平衡基元反应(A+B→R)流场的数值模拟, 研究了该流场中各组分在T/NTI附近的化学反应和标量输运特性。研究结果表明: 反应性射流流场中对流项在湍流区域的标量输运中占主导地位。射流的上游处化学反应较为剧烈且随着流向逐渐减弱, 在T/NTI层内及其附近均存在显著的化学反应, 而下游T/NTI层附近的化学反应主要发生在远离T/NTI层的湍流核心区。在T/NTI层附近, 反应物A和生成物R的输运机制呈现类似但相反的趋势。在无旋边界附近, 反应物A和生成物R的输运主要由扩散和对流作用共同影响, 但其浓度几乎不随时间发生变化。在T/NTI层内, 反应物B的输运主要由对流作用影响, T/NTI附近的流动阻碍化学反应后所余较少的反应物B向无旋边界输运。Abstract: Turbulent/non-turbulent interface (T/NTI) layer separates the turbulent and non-turbulent regions. The study of T/NTI is helpful to deepen the understanding of mass transfer between turbulent and non-turbulent regions. In this paper, the chemical reaction and scalar transport characteristics of each component in the flow field near T/NTI were studied by numerical simulation of the two-stage non-equilibrium elementary reaction (A+B→R) flow field between the jet and the environmental flow. The results show that the convection term in the reactive jet flow field dominates the influence of scalar transport in the turbulent region. At the upstream region of the jet, the chemical reaction is more intense and gradually weakens along the flow direction. There are significant chemical reactions within and near the T/NTI layer. The chemical reactions near the downstream T/NTI layer mainly occur in the turbulent core region far away from the T/NTI layer. Near the T/NTI layer, the transport mechanism of reactant A and resultant R shows a similar but opposite trend. Near the irrotational boundary of the T/NTI layer, the transport of reactant A and resultant R is mainly affected by diffusion and convection, but their concentrations hardly change with time. The transport of reactant B in the T/NTI layer is mainly affected by convection. The remaining reactant B after the chemical reaction is blocked by the flow near T/NTI to transport to the irrotational boundary.