Abstract An experimental study was performed to investigate the effects of nozzle spacing between twin rectangular jets on the non-linear momentum interference and spatial evolution of large-scale flow structures. Five test cases of different spacing ratios (S/de = 1.8, 2.8, 3.7, 5.5 and 7.3) were examined. Two-point correlation, joint probability density function and swirling strength were used to characterize the large-scale structures. Turbulent/non-turbulent interface along the inner and outer shear layers were investigated. The results showed that due to the interactions in the merging region, the spatial correlation of streamwise velocity fluctuations was considerably lower along the inner shear layer than along the outer shear layer. As a result of the mixing process, the swirling strength of retrograde vortices generated along the inner shear layer was also lower than that of the prograde vortices. Along the symmetry line, longitudinal and transverse integral length scales increased linearly as the downstream distance from the jets increases. For the longitudinal length scale, the slope of the linear region was independent of the spacing ratio, while for the transverse length scale, the slope increases as the spacing ratio increases. For cases of S/de

中文翻译：

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双矩形射流大尺度相干结构及动量干涉研究

摘要 通过实验研究了双矩形射流喷嘴间距对大尺度流动结构非线性动量干涉和空间演化的影响。检查了五个不同间距比（S/de = 1.8、2.8、3.7、5.5 和 7.3）的测试案例。使用两点相关、联合概率密度函数和旋流强度来表征大尺度结构。研究了沿内部和外部剪切层的湍流/非湍流界面。结果表明，由于合并区域的相互作用，沿内剪切层的流向速度波动的空间相关性明显低于沿外剪切层。由于混合过程，沿内剪切层产生的逆行涡旋强度也低于顺行涡旋。沿着对称线，纵向和横向积分长度尺度随着下游距离射流的增加而线性增加。对于纵向长度尺度，线性区域的坡度与间距比无关，而对于横向长度尺度，坡度随着间距比的增加而增加。对于 S/de 的情况 斜率随着间距比的增加而增加。对于 S/de 的情况 斜率随着间距比的增加而增加。对于 S/de 的情况