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首页> 外文期刊>Journal of Fluid Science and Technology >Direct numerical simulation of a turbulent mixing layer with a transversely oscillated inflow
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Direct numerical simulation of a turbulent mixing layer with a transversely oscillated inflow

机译：具有横向振荡流入的湍流混合层的直接数值模拟

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Direct numerical simulation of a turbulent mixing layer with a transversely oscillated inflow is performed. The inlet flow is generated by two driver parts of turbulent boundary layers. The Reynolds number based on the freestream velocity on the low speed side, U_(L) , the 99% boundary layer thickness of the inflow, δ , and the kinematic viscosity, v , is set to be Re = 3000. In order to compare the results with the experimental study of Naka et al. [Naka, Tsuboi, Kametani, Fukagata, and Obi, J. Fluid Sci. Technol., Vol. 5, pp. 156-168 (2010)], the angular frequency of the oscillation was set to be Ω_(c) = 0:83 and 3.85 (referred to as Case A and Case B, respectively). From the three-dimensional visualization, large-scale spanwise vortical structures are clearly observed in the controlled cases. The momentum thickness and the vorticity thickness indicate that the mixing is enhanced in Case A, while it is temporarily suspended in Case B. In both cases, the Reynolds normal stresses are increased in the region right downstream of the forcing point due to the periodic forcing. Furthermore, in Case B, the Reynolds shear stress (RSS), -u ′v ′, is suppressed in the region downstream of the forcing point. The spatial development of the turbulent energy thickness, δ_(k) , and the Reynolds shear stress thickness, δ_(rss) , show that the Reynolds shear stress in Case B is decreased by the control despite the increase of the turbulent kinetic energy. From the spectral analysis, large-scale spanwise structures are found to be caused by the periodic forcing, while the spectra of the spanwise velocity fluctuations are nearly unchanged. Co-spectra of the Reynolds stresses show that the present forcings generally enhance the long wavelength component. In Case B, however, the long wavelength component of the Reynolds shear stress is not increased in the downstream region.
机译：对具有横向振荡流入的湍流混合层进行直接数值模拟。入口流由湍流边界层的两个驱动器部分产生。基于低速侧的自由流速度 U_（L），流入的99％边界层厚度δ和运动粘度 v的雷诺数设置为为了使结果与Naka等人的实验研究比较，Re ＝ 3000。 [Naka，Tsuboi，Kametani，Fukagata和Obi，J。Fluid Sci。技术，卷。 [第5卷，第156-168页（2010）]，将振荡的角频率设置为Ω_（c）＝ 0：83和3.85（分别称为情况A和情况B）。从三维可视化，在受控情况下可以清楚地观察到大规模的翼展旋涡结构。动量厚度和涡旋厚度表明，在情况A中混合增强，而在情况B中暂时中止。在这两种情况下，由于周期性的强迫作用，在强迫点正下游的区域雷诺法向应力增加了。此外，在情况B中，在施力点的下游区域中，雷诺剪切应力（RSS）-i u'i v'被抑制。湍流能量厚度δ_（k）和雷诺剪切应力厚度δ_（rss）的空间发展表明，尽管B的增加，但案例B的雷诺剪切应力却通过控制减小了。湍动能。通过频谱分析，发现大规模的翼展结构是由周期性强迫引起的，而翼展速度波动的谱几乎不变。雷诺应力的共谱表明，当前的强迫通常会增强长波分量。但是，在情况B中，雷诺剪切应力的长波分量在下游区域没有增加。

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