The effects of turbulence and pressure gradients on vorticity transport in premixed bluff-body flames
The effects of turbulence and pressure gradients on vorticity transport in premixed bluff-body flames
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湍流和压力梯度对预混钝体火焰中涡度传递的影响
DOI：
10.1063/5.0031068
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发表时间：
2021
影响因子：
4.6
通讯作者：
K. Ahmed
中科院分区：
文献类型：
--
作者：
Cal J. Rising;A. Morales;Marissa K. Geikie;K. Ahmed
本文通过实验研究了紊流和压力梯度对预混合崖体火焰涡度输运的影响。采用变几何试验段对流场压力梯度进行了修正。在串联中，使用定制设计的湍流发生器来调节试验段的湍流强度。结合压力梯度和湍流裁剪的目的是改变涡量输运方程各项之间的平衡，并最终确定对火焰和流场整体行为的后续影响。采用高速粒子成像测速和CH*化学发光同时测量湍流反应流场。涡度动力学分析采用平均条件过滤流体元跟踪方法，计算流体元在火焰锋面演化过程中涡度输运方程的各个项。分析表明，压力梯度的增大使各涡量项的反应涡量增大。相反，总体涡度收支，或每个涡度项的相对贡献，对湍流效应更为敏感。在低湍流条件下，涡度由斜压转矩主导，与压力梯度无关。随着湍流强度的增加，斜压和膨胀的放热效应减弱，反应流场接近于非反应流场。涡量输运项的相对平衡不仅影响整个流场，而且影响火焰锋面的结构和演变。
The current study experimentally evaluates the effects of turbulence and pressure gradients on vorticity transport in premixed bluff-body flames. The flow field pressure gradient is modified using a variable-geometry test section. In tandem, a custom-designed turbulence generator is used to modulate the turbulence intensity in the test section. The objective of the combined pressure gradient and turbulence tailoring is to alter the balance between the individual terms of the vorticity transport equation and ultimately identify the subsequent impacts on the overall behavior of the flame and flow field. Simultaneous high-speed particle image velocimetry and CH* chemiluminescence are employed to measure the turbulent reacting flow field. The vorticity dynamics are analyzed using a mean, conditionally filtered, fluid element tracking method to calculate individual terms of the vorticity transport equation as fluid elements evolve across the flame front. The analysis shows that increasing the pressure gradient increases the reacting vorticity production for all vorticity terms. In contrast, the overall vorticity budget, or relative contribution of each vorticity term, is much more sensitive to turbulence effects. At low turbulence conditions, vorticity is dominated by baroclinic torque, regardless of the pressure gradient. As the turbulence intensity is increased, the exothermic effects of baroclinicity and dilatation are diminished, and the reacting flow field approaches that of a non-reacting turbulent flow. The relative balance of vorticity transport terms is shown to influence the overall flow field, as well as the structure and evolution of the flame front.
影响因子：
2.6
作者：
Chakraborty, Nilanjan
通讯作者：
Chakraborty, Nilanjan