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首页> 外文期刊>International Journal of Heat and Mass Transfer >Influence of inlet vorticity and aspect ratio on axis-switching and mixing characteristics of heated rectangular jets
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Influence of inlet vorticity and aspect ratio on axis-switching and mixing characteristics of heated rectangular jets

机译：入口涡度和纵横比对加热矩形喷射轴切换和混合特性的影响

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To investigate interactive characteristics between the inlet condition and axis-switching phenomenon, heated rectangular jets are numerically investigated for seven aspect ratios (AR = 1.0 - 6.0) with three jet temperatures of 300, 500, and 1000 K. The corresponding Reynolds number is 11,400 - 21,000. To examine the relative importance of ω_θ and ω_x on axis-switching, seven inlets are obtained by an inflow generator. For the flows of nozzle part, various geometry-driven and turbulence-driven vortices are observed. It is shown that the rotational directions of turbulence-driven vortices have the rotational direction hindering the axis-switching flow. By using the crossover location of the jet half-widths and the mixing length, the axis-switching condition depending on AR and jet temperature is explained. The crossover location is changed to the ω_x-variation, which is approximately eight times as sensitive as the ω_θ -variation. Based on the results of AR and temperature changes, the strong influence on axis-switching flow and mixing is confirmed for the ω_x-change. Also, the heat transfer effect on mixing enhancement becomes strong for the weak axis-switching condition. As AR increases, the mixing performance decreases, but mixing enhancement of the axis-switching flow is confirmed for AR ≤ 4. Finally, to explain the ω_x-variation related to the axis-switching mechanism, the ω_x transport equations are analyzed by three terms of the Prandtl's first kind and the baroclinic torque. The roles of the vortex stretching and baroclinic torque terms are analyzed for the positive effect of the ω_x-variation on the axis-switching phenomenon.
机译：为了研究入口状况和轴切换现象之间的交互式特性，在数值上研究了加热的矩形喷射器，用于七个纵横比（Ar = 1.0-6.0），具有300,500和1000k的三个喷射温度。相应的雷诺数是11,400 - 21,000。为了检查ω_θ和ω_x在轴切换上的相对重要性，通过流入发生器获得七个入口。对于喷嘴部分的流动，观察到各种几何驱动和湍流驱动的涡流。结果表明，湍流驱动的涡流的旋转方向具有阻碍轴切换流的旋转方向。通过使用喷射半宽和混合长度的交叉位置，解释了根据AR和喷射温度的轴切换条件。交叉位置被改变为ω_x变化，其与ω_θ的大约敏感的八倍。基于AR和温度变化的结果，确认ω_x变化的对轴切换流和混合的强烈影响。而且，对于弱轴切换条件，对混合增强的传热效果变得强大。随着AR的增加，混合性能降低，但是为AR≤4确认了轴切换流的混合增强。最后，为了解释与轴切换机构相关的ω_x变化，通过三个术语分析ω_x传输方程Prandtl的第一种和曲金扭矩的概述。分析涡旋拉伸和曲金扭矩术语的作用，用于ω_x变化对轴切换现象的正效应。

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