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首页> 外文学位 >Numerical Study of Laminar Free-Shear-Layer Stability in Wall Proximity and in the Presence of Cross-Stream Thermodynamic Property Gradients.
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Numerical Study of Laminar Free-Shear-Layer Stability in Wall Proximity and in the Presence of Cross-Stream Thermodynamic Property Gradients.

机译：壁附近和存在横流热力学特性梯度时层流自由剪切层稳定性的数值研究。

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摘要

This thesis investigates the stability characteristics of laminar planar shear layers, including the effect of proximity of the shear layer to a nearby wall and the effect of cross-stream property gradients for fluids in the thermodynamic supercritical state. The results of a series of numerical studies are presented for the stability characteristics of a shear layer in close proximity of a no-slip wall. The shear layer is formed by the merging of two boundary-layer flows separated by a thin splitter plate. The Reynolds number at the splitter-plate trailing-edge, the velocity ratio of the high- and low-speed streams, and the proximity of the shear layer to the no-slip wall are systematically varied to investigate the effects of these parameters on the development of the shear layer. Sensitivity to wall-proximity is clearly observed and an explanation is given based on the interaction with the wall of the shed vortices that form in the unstable free shear layer. Numerical simulations results are presented on the stability characteristics of free shear layers in supercritical fluids with cross-stream property gradients. The results are compared to the stability of free shear layers of subcritical single-phase fluids with matching Reynolds number and velocity ratio. In the case with supercritical working fluid, the free shear layer deformed by the Kelvin Helmholtz instability mode is observed to produce body forces that create an effective Richardson number sufficiently high to sustain the Holmboe instability mechanism. This Holmboe instability produces thin Holmboe vortices that co-exist with the Kelvin-Helmholtz vortices. Three dimensional instability that follows these instability modes is observed to have a reduced dominant spanwise wavelength when the working fluid is at a supercritical state with cross-stream property gradients.
机译：本文研究了层状平面剪切层的稳定性特征，包括剪切层靠近附近壁的影响以及热力学超临界状态下流体的横流特性梯度的影响。提出了一系列数值研究的结果，这些结果针对的是紧邻防滑墙的剪切层的稳定性特征。剪切层是由两个边界层流合并而成的，这两个边界层流由一块薄的分隔板分隔开。系统地改变了分流板后缘的雷诺数，高速流和低速流的速度比以及剪切层与防滑壁的接近度，以研究这些参数对管道的影响。剪切层的发展。可以清楚地观察到对壁的敏感性，并基于与在不稳定的自由剪切层中形成的旋涡的壁之间的相互作用给出了解释。数值模拟结果给出了具有横流特性梯度的超临界流体中自由剪切层的稳定性特征。将结果与具有雷诺数和速度比匹配的亚临界单相流体的自由剪切层的稳定性进行了比较。在超临界工作流体的情况下，观察到由开尔文·亥姆霍兹（Kelvin Helmholtz）不稳定性模式变形的自由剪切层会产生体力，该力产生足够高的有效理查森数以维持Holmboe不稳定性机制。这种Holmboe不稳定性会产生与Kelvin-Helmholtz涡流共存的细Holmboe涡流。当工作流体处于具有跨流特性梯度的超临界状态时，遵循这些不稳定性模式的三维不稳定性被观察到具有减小的主展向波长。

著录项

  • 作者

    John, Aneesh.;

  • 作者单位

    Carleton University (Canada).;

  • 授予单位 Carleton University (Canada).;
  • 学科 Engineering Aerospace.
  • 学位 M.A.Sc.
  • 年度 2012
  • 页码 155 p.
  • 总页数 155
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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