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首页> 外文期刊>International Journal of Heat and Fluid Flow >Heat release effects on mixing scales of non-premixed turbulent wall-jets: A direct numerical simulation study
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Heat release effects on mixing scales of non-premixed turbulent wall-jets: A direct numerical simulation study

机译：放热对非预混湍壁射流混合尺度的影响：直接数值模拟研究

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摘要

The present study concerns the role of heat release effects on characteristics mixing scales of turbulence in reacting wall-jet flows. Direct numerical simulations of exothermic reacting turbulent wall-jets are performed and compared to the isothermal reacting case. An evaluation of the heat-release effects on the structure of turbulence is given by examining the mixture fraction surface characteristics, diagnosing vortices and exploring the dissipation rate of the fuel and passive scalar concentrations, and moreover by illustration of probability density functions of reacting species and scatter plots of the local temperature against the mixture fraction. Primarily, heat release effects delay the transition, enlarge the fluctuation intensities of density and pressure and also enhance the fluctuation level of the species concentrations. However, it has a damping effect on all velocity fluctuation intensities and the Reynolds shear stress. A key result is that the fine-scale structures of turbulence are damped, the surface wrinkling is diminished and the vortices become larger due to heat-release effects. Taking into account the varying density by using semi-local scaling improves the collapse of the turbulence statistics in the inner region, but does not eliminate heat release induced differences in the outer region. Examining the two-dimensional premultiplied spanwise spectra of the streamwise velocity fluctuations indicates a shifting in the positions of the outer peaks, associated with large energetic structures, toward the inner region.
机译：本研究涉及放热效应在反应壁面射流中湍流特征混合尺度上的作用。进行了放热反应湍流壁面射流的直接数值模拟，并将其与等温反应情况进行了比较。通过检查混合物部分的表面特性，诊断涡旋并探索燃料的消散率和被动标量浓度，并通过举例说明反应物种和反应物种的概率密度函数，对放热对湍流结构的影响进行了评估。局部温度对混合比例的散点图。首先，放热效应会延迟过渡，增大密度和压力的波动强度，并增加物种浓度的波动水平。但是，它对所有速度波动强度和雷诺剪切应力都有阻尼作用。关键结果是，由于热释放效应，湍流的细微尺度结构被阻尼，表面起皱减小，涡旋变大。通过使用半局部缩放考虑变化的密度可以改善内部区域中湍流统计的崩溃，但不能消除外部区域中由放热引起的差异。检查流向速度波动的二维预乘展展跨度谱表明，与大型高能结构相关的外峰位置朝着内部区域移动。

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