Abstract Local transport of the flow momentum and scalar admixture in the near-field of turbulent swirling jets (Re = 5,000) has been investigated by using a combination of the particle image velocimetry and planar laser-induced fluorescence methods. Advection and turbulent and molecular diffusions are evaluated based on the measured distributions of the mean velocity and concentration and the Reynolds stresses and fluxes. As has been quantified from the data, the flow swirl intensifies the entrainment of the surrounding fluid and promotes mass and momentum exchange in the outer mixing layer. A superimposed swirl results in the appearance of a wake/recirculation region at the jet axis and, consequently, the formation of an inner shear layer. In contrast to the scalar admixture, the momentum exchange in the inner shear layer is found to be strongly intensified by the swirl. For the jet with the highest considered swirl rate, a substantial portion of the surrounding fluid is found to enter the unsteady central recirculation zone, where it mixes with the jet that is issued from the nozzle. The contribution of the coherent velocity fluctuations, which are induced by large-scale vortex structures, to the turbulent transport has been evaluated based on triple decomposition, which was based on proper orthogonal decomposition analysis of the velocity data sets. For the considered domain of the jet with the highest swirl rate and vortex breakdown, the contributions of detected helical vortex structures, inducing pressing vortex core, to the radial fluxes of the flow momentum and the scalar admixture are found to locally exceed 65% and 80%, respectively.

中文翻译：

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涡旋湍流射流近场中的质量和动量传输。旋流率的影响

摘要 结合粒子图像测速法和平面激光诱导荧光方法，研究了湍流涡旋射流 (Re = 5,000) 近场中流动动量和标量混合物的局部传输。基于平均速度和浓度的测量分布以及雷诺应力和通量来评估平流和湍流以及分子扩散。正如从数据中量化的那样，流动漩涡加强了周围流体的夹带，并促进了外混合层中的质量和动量交换。叠加涡流导致在射流轴出现尾流/再循环区域，从而形成内部剪切层。与标量混合相比，发现内部剪切层中的动量交换被漩涡强烈加强。对于考虑到的最高涡流率的射流，发现大部分周围流体进入不稳定的中心再循环区，在那里它与从喷嘴发出的射流混合。由大尺度涡结构引起的相干速度波动对湍流输运的贡献已基于三重分解进行评估，三重分解基于速度数据集的适当正交分解分析。对于具有最高涡流率和涡流击穿的射流所考虑的域，检测到的螺旋涡流结构的贡献，诱导压涡核，