Experimental investigation of vortex breakdown in a coaxial swirling jet with a density difference
Experimental investigation of vortex breakdown in a coaxial swirling jet with a density difference
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DOI：
10.1016/j.ces.2012.05.027
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发表时间：
2012-10
影响因子：
4.7
通讯作者：
A. Adzlan;H. Gotoda
中科院分区：
文献类型：
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作者：
A. Adzlan;H. Gotoda
在这项工作中，我们实验研究了稳定的涡破裂的行为发生在同轴旋转射流与密度差，突出的影响外射流的驻点高度。随着外射流总流速的增加，流动发散程度减小，导致驻点高度增加。这是由于沿射流中心线的平均轴向速度沿着显著增加，粒子图像测速仪（PIV）清楚地显示了这一点。基于同轴射流的简化Navier-Stokes方程，通过考虑流动中动量平衡的估计，提出了一个方程来物理解释具有密度差的同轴旋转射流发生涡破裂时驻点的高度。即使密度差对驻点高度的影响被所提出的方程高估，实验观察到的外射流雷诺数的增加与理论模型预测的趋势在定性上相当吻合。
In this work we experimentally investigate the behavior of stable vortex breakdown taking place in a coaxial swirling jet with a density difference, highlighting the effect of the outer jet on the height of the stagnation point. With increasing bulk flow velocity of the outer jet, the degree of flow divergence decreases, resulting in an increase in the height of the stagnation point. This is due to a significant increase in the mean axial velocity along the centerline of the jet, which is clearly shown by particle image velocimetry (PIV). We proposed an equation to physically explain the height of the stagnation point in a coaxial swirling jet with a density difference undergoing vortex breakdown, by considering an estimate of the momentum balance in the flow, based on a simplified Navier–Stokes equation for coaxial jets with coannular flow. Even though the effect of the density difference on the height of the stagnation point is overestimated by the proposed equation, the increase with respect to the Reynolds number of the outer jet observed experimentally is in reasonably good qualitative agreement with the trend predicted by the theoretical model.