Influence of the velocity field on scalar transport in gaseous transverse jets
Influence of the velocity field on scalar transport in gaseous transverse jets
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速度场对气体横向射流标量输运的影响
DOI：
10.1017/jfm.2017.621
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发表时间：
2017
影响因子：
3.7
通讯作者：
A. Karagozian
中科院分区：
文献类型：
--
作者：
L. Gevorkyan;T. Shoji;Wen Yu Peng;A. Karagozian
在不同的射流与横流动量通量比J$(5、12和41)和密度比$S$(0.35和1.0)下，对横流中喷出的气体射流的动力学特性进行了研究。本文研究了异型喷嘴和直管喷射器，在改变其他流动参数的情况下，射流雷诺数固定为1900。利用丙酮平面激光诱导荧光(PLIF)成像和立体粒子图像测速仪(PIV)研究了标量场和速度/涡量场之间的关系，重点比较了基于PLIF的标量耗散率和局部应变率的提取以及基于PIV的射流上、下游剪切层的局部应变率。横流中射流的标量场和涡量场在低J$或$S$值的绝对不稳定上游射流剪切层的横跨条件下与较大美元J$的对流不稳定剪切层的条件、等密度条件(Megerian等人，《流体力学》，卷593,2007年，第93-129页；盖辛格等，Exp.)之间有显著的相似性。《流体》，第53卷，2012年，第783-801页)。对标量场和速度场进行适当的正交分解，发现上游剪切层和射流尾迹中的不稳定性增强，因为$J$降低了。同时的测量使PLIF提取的标量耗散率和应变率可以通过小火焰模型确定，并与PIV提取的应变率进行比较，每个应变率都在扩散层法线方向。在大多数流动条件下，喷流上游和下游剪切层中的这些指标在定性和定量上都有很好的一致性，与剪切层涡卷的位置有很好的一致性，尽管在某些情况下，基于PLIF和PIV的下游剪切层应变率数据之间的一致性较差。结果表明，这种差异可能是由扩散和分辨率效应以及三维和瞬变效应的影响造成的，而三维和瞬变效应在喷流背风侧可能更显着。然而，目前的结果揭示了有趣的动力学，并证明了应变场在增强扩散和输运现象中的重要性。
The present experiments explored the dynamical character of the gaseous jet injected flush into cross-flow for variable jet-to-cross-flow momentum flux ratios $J$ (5, 12 and 41) and density ratios $S$ (0.35 and 1.0). Contoured nozzle and straight pipe injectors were studied here, with the jet Reynolds number fixed at 1900 as other flow parameters were varied. Simultaneous acetone planar laser-induced fluorescence (PLIF) imaging and stereo particle image velocimetry (PIV) were used to study the relationships between scalar and velocity/vorticity fields, with a special focus on comparing PLIF-based extraction of scalar dissipation rates and local strain rates with PIV-based local strain rates in the upstream and downstream shear layers of the jet. There was remarkable similarity between the scalar and vorticity fields for the jet in cross-flow, spanning conditions for absolutely unstable upstream jet shear layers at low $J$ or $S$ values to conditions for convectively unstable shear layers for larger $J$ , equidensity conditions (Megerian et al., J. Fluid Mech., vol. 593, 2007, pp. 93–129; Getsinger et al., Exp. Fluids, vol. 53, 2012, pp. 783–801). Proper orthogonal decomposition applied to both scalar and velocity fields revealed strengthening instabilities in both the upstream shear layer and in the jet’s wake as $J$ was reduced. The simultaneous measurements allowed PLIF-extracted scalar dissipation rates and strain rates to be determined via a flamelet-like model and compared with PIV-extracted strain rates, each in the diffusion layer-normal direction. There was generally very good qualitative and quantitative agreement for these metrics in both the jet upstream and downstream shear layers for most flow conditions, with excellent correspondence to locations of shear layer vorticity roll up, although downstream shear layer strain rates in some cases showed lesser correspondence between PLIF- and PIV-based data. Such differences are shown to potentially result from diffusion and resolution effects as well as the influence of three-dimensional and transient effects which can be more significant in the lee side of the jet. Nevertheless, the present results reveal interesting dynamics and demonstrate the importance of strain fields in enhanced diffusion and transport phenomena.