Mixing of confined coaxial flows
Mixing of confined coaxial flows
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DOI：
10.1016/j.ijheatmasstransfer.2006.04.022
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发表时间：
2006-10-01
影响因子：
5.2
通讯作者：
Chorny, Andrei
中科院分区：
文献类型：
--
作者：
Zhdanov, Valery;Kornev, Nikolay;Chorny, Andrei
本文介绍了同轴射流混合器在两种混合状态下的混合过程的实验结果。在第一种混合模式中，在靠近混合器壁的喷嘴后面形成再循环区，而在第二种混合模式中，射流与共流混合而不形成再循环区。在两种情况下，研究了R-ed = 10 000时的混合过程。在喷嘴后0.1 < x/D < 9.1范围内，用单分量激光多普勒测速仪测量混合器截面的速度场，用激光图像荧光（LIF）法检测标量场。利用标量及其波动的瞬时分布计算了横向自相关函数、积分长度尺度和概率密度函数（PDF）。结果表明，标量场比速度场更快地获得齐次态。在第一个混合区，混合器横截面在距离x/D = 5.1处完成了准均匀的标量分布，而在第二个混合区，这种分布尚未实现。湍流统计矩和自相关函数的分析揭示了非定常涡旋结构对混合的巨大影响。当再循环区形成后，混合器壁面附近存在长周期反相振荡。(c) 2006 Elsevier Ltd.版权所有。
The paper presents experimental results on the mixing process in a coaxial jet mixer in two mixing regimes. In the first mixing regime, a recirculation zone develops just behind a nozzle near mixer walls, while in the second regime a jet is mixed with the co-flow without developing a recirculation zone. In the both regimes, the mixing process is studied at R-ed = 10 000. Behind the nozzle over the range 0.1 < x/D < 9.1, a velocity field in mixer cross-sections is measured by a one-component laser Doppler velocity meter and a scalar field is detected by the laser image fluorescence (LIF) method. A transverse autocorrelation function, integral length scales and probability density functions (PDF) are calculated using instantaneous distributions of a scalar and its fluctuations. It is shown that the scalar field acquires a homogeneous state faster than the velocity one. A quasi-uniform scalar distribution over the mixer cross-section is completed at the distance x/D = 5.1 in the first mixing regime, while this distribution has not been yet attained in the second. Analysis of the turbulent statistical moments and the autocorrelation function reveals how unsteady vortex structures exert a dramatic influence on the mixing. When the recirculation zone has developed, long-period antiphase oscillations exist near the mixer walls. (c) 2006 Elsevier Ltd. All rights reserved.