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Numerical Study of Turbulent Channel Flows Perturbed by Spanwise Topographic Heterogeneity: Inner-Outer Interactions Within Low- and High-Momentum Pathways

机译:跨向地形异质性扰动湍流通道的数值研究:低动量和高动量通路内外相互作用

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摘要

This work presents a study on secondary flows, driven and sustained due to topographical variations in the domain. The effects of these secondary flows on inner-outer interactions are then analyzed. This type of interaction between the large-scale structures residing in the logarithmic region and the small-scale structures in the near-wall region have been under extensive study recently. And efforts are being made to develop a predictive model for the dynamics of near-wall structures based on the measurements at a certain certain distance from the wall. Such a model has immense practical implication for large-eddy simulations. Existing work on amplitude modulation has been focused on smooth-wall flow, however recently roughness-induced changes on amplitude and frequency modulation are being studied which provides a better understanding of the interaction in real conditions. Here a similar study is presented using wavelet analysis to examine how spanwise heterogeneity affects the spectral density and correlation profiles, which provides a basis for the understanding of amplitude and frequency modulation. The topography under consideration are two Gaussian mounds placed 2H apart, where H is the flow depth, which induce a domain-scale secondary motion in the flow. The counter-rotating vortices are flanked on either side of the topography such that prominent upwelling and downwelling occurs above the low and high roughness respectively. Two cases with the maximum height of the topography as h/H = 0.05 and 0.1 are considered, and the results are compared with a homogeneous roughness case (h/H = 0). A change in the inclination angle of coherent structures is observed within downwelling region of the flow, however, it does not diminish inner-outer interactions. The extent to which secondary flows disrupts the distribution of spectral density across constituent wavelengths throughout the depth of the domain are also quantified. It is observed that the outer peak associated with the large-scale motions is preserved within the upwelling zone, but vanishes in the downwelling zone. Single- and two- point correlation profiles for low-, intermediate- and high-resolution are compared which validates the resolution independence. An important observation indicates that the selection of reference location while computing the two-point correlation profiles is quintessential. It is also revealed that the strength of modulation is not determined by the wavelength at which the spectral energy resides, but by a mere presence of energy above the separation scale.
机译:这项工作提出了对次流的研究,该次流是由域中地形变化引起的。然后分析这些次要流动对内外相互作用的影响。对数区域中的大型结构与近壁区域中的小型结构之间的这种相互作用最近已得到广泛研究。并且正在基于距墙一定距离的测量结果来开发用于近墙结构动力学的预测模型。这样的模型对大涡模拟具有巨大的实际意义。现有的调幅工作已经集中在光滑壁流上,但是最近正在研究粗糙度引起的调幅和调频变化,这可以更好地理解实际条件下的相互作用。在这里,使用小波分析提出了类似的研究,以检查跨度异质性如何影响频谱密度和相关曲线,这为理解幅度和频率调制提供了基础。所考虑的地形是两个高斯土丘,相隔2H,其中H是水流深度,它们在水流中引起域尺度的二次运动。反向旋转的涡旋在形貌的两侧,使得分别在低粗糙度和高粗糙度之上发生明显的上升和下降。考虑了两个具有最大地形高度h / H = 0.05和0.1的情况,并将结果与​​均匀粗糙度情况(h / H = 0)进行了比较。在流体的下流区域内观察到相干结构的倾斜角的变化,但是,这并没有减少内外相互作用。还量化了次级流动在整个域深度上破坏组成波长上的光谱密度分布的程度。可以观察到,与大规模运动相关的外峰保留在上升流区内,但在下降流区内消失。比较了低分辨率,中分辨率和高分辨率的单点和两点相关配置文件,从而验证了分辨率的独立性。一个重要的观察表明,在计算两点相关轮廓时参考位置的选择是典型的。还揭示出调制强度不是由光谱能量所处的波长决定的,而是由分离尺度以上的能量的存在决定的。

著录项

  • 作者

    Awasthi, Ankit.;

  • 作者单位

    The University of Texas at Dallas.;

  • 授予单位 The University of Texas at Dallas.;
  • 学科 Mechanical engineering.
  • 学位 Ph.D.
  • 年度 2018
  • 页码 73 p.
  • 总页数 73
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 康复医学;
  • 关键词

  • 入库时间 2022-08-17 11:40:04

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