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首页> 外文学位 >A 3-D Numerical Study of Flow, Coherent Structures, and Mechanisms Leading to Scour in a High Curvature 135° Channel Bend With and Without Submerged Groynes.
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A 3-D Numerical Study of Flow, Coherent Structures, and Mechanisms Leading to Scour in a High Curvature 135° Channel Bend With and Without Submerged Groynes.

机译：带有和不带有浸没式丁坝的高曲率135°通道弯曲中导致冲刷的流动，相干结构和机理的3-D数值研究。

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摘要

This thesis focused on investigating flow, coherent structures, and mechanisms leading to scour around a series of three submerged groynes in a high curvature (radius of curvature (R)/channel width (B)=1.5) channel bend using a Large Eddy Simulation Numerical (LES) model. Flow was investigated during both an initial and a later stage of scour. The results showed that the groynes appeared effective in keeping the main core of high streamwise velocity away from the outer bank wall in the region where they were installed, although high potential still existed for local scour around the groynes. During the initial stage of scour, horseshoe vortices (HVs) showed the greatest propensity to induce scour immediately upstream of the groyne tips. During the later stage of scour, the HV in front of the first upstream groyne (G1) induced very high mean pressure fluctuations on the outer bank wall. Scour was also of very great concern around the tip of G1 due to severe mean bed pressure fluctuations. Downstream of the groyne field, the presence of a counter-rotating outer bank cell was capable of endangering the stability of the outer bank.;The second focus of this thesis was to investigate flow in a 135° channel bend using both Reynolds Averaged Navier Stokes (RANS) and LES numerical models. The RANS study examined the effects of curvature ratio (R/B ), and aspect ratio (B/H, where H is the inlet flow depth), on secondary circulation strength, and bed shear stresses. The study revealed that a decrease in R/B was associated with an increase in secondary circulation strength and peak bed shear stress. A change in B/H also substantially affected cross stream circulation strength. The LES study was conducted in a 135° ( R/B = 1.5) bend flume with a fixed bed corresponding to near equilibrium scour conditions, and the results were compared to a similar high curvature 193° bend numerical study. Inner bank vortices and shear layers were present in both cases although their characteristics were substantially different. Distributions of boundary friction velocities, and turbulence were also quite different for each case.
机译：本文重点研究使用大涡模拟数值模拟高弯度（曲率半径（R）/通道宽度（B）= 1.5）通道弯曲时围绕一系列三个浸没式丁坝冲刷的流动，相干结构和机理。 （LES）模型。在冲刷的初期和后期都研究了流量。结果表明，尽管在堤坝周围仍存在局部冲刷的可​​能性，但堤坝似乎可以有效地使高流速的主岩心远离其安装区域的外堤壁。在冲刷的初始阶段，马蹄形涡流（HVs）表现出最大的倾向，可直接在防波堤尖端上游产生冲刷。在冲刷的后期，第一个上游防波堤（G1）前面的HV在外堤壁上引起很高的平均压力波动。由于严重的平均床压波动，冲刷在G1尖端附近也非常令人担忧。防波堤场的下游，存在一个反向旋转的外部堤岸单元，能够危害外部堤岸的稳定性。本论文的第二个重点是利用雷诺兹平均纳维耶斯托克斯曲线研究135°槽弯处的水流（RANS）和LES数值模型。 RANS研究检查了曲率比（R / B）和长宽比（B / H，其中H是入口流动深度）对二次循环强度和床层剪应力的影响。研究表明，R / B的下降与二次循环强度和峰值床切应力的增加有关。 B / H的变化也大大影响了横流循环强度。 LES研究是在135°（R / B = 1.5）弯曲水槽中进行的，固定水床与接近平衡的冲刷条件相对应，并将结果与​​类似的高曲率193°弯曲数值研究进行比较。两种情况下都存在内层涡流和剪切层，尽管它们的特征有很大不同。在每种情况下，边界摩擦速度和湍流的分布也有很大不同。

著录项

  • 作者

    Kashyap, Shalini.;

  • 作者单位

    University of Ottawa (Canada).;

  • 授予单位 University of Ottawa (Canada).;
  • 学科 Engineering Civil.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 320 p.
  • 总页数 320
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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