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Partially averaged Navier-Stokes method for turbulence closures: Characterization of fluctuations and extension to wall bounded flows.

机译：湍流封闭的部分平均Navier-Stokes方法：脉动特征和对壁边界流的扩展。

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摘要

The work presented in this dissertation concerns continued development, validation and verification of the partially averaged Navier-Stokes (PANS) method -- a variable resolution closure model for turbulence. Linear eddy viscosity models (LEVM), which are popular because of their simplicity and affordability in terms of computational cost have fundamental deficiencies and cannot be trusted to accurately represent turbulence in realistic complex flows. The more high fidelity approaches such as large eddy simulations (LES) and direct numerical simulations (DNS) are out of realm of engineering applicability because of their high requirements in computing power. PANS, a variable resolution approach considered in this study, lies between LEVM and LES in terms of computational cost and is designed to prudently utilize the available computing power to improve accuracy.;This dissertation presents the various studies performed to characterize the PANS fluctuations and extend the model for use in various wall bounded flows. The road map towards our goal includes: (i) Comparing a-priori and a-posteriori eddy viscosity values to establish whether PANS is capable of producing the pre-specified level of reduction. (ii) Investigating the scaling of PANS fluctuations for different levels of prescribed resolution and establishing if the fluctuations abide by known turbulence scaling laws. (iii) Extending PANS to k-o formulation which is better suited for wall-bounded shear flows, and (iv) Modifying the present LEVM to yield reasonable behavior in the rapid distortion limit where the turbulence is elastic in nature which ultimately affects PANS performance.;Results reported in this dissertation illustrate that the PANS closure yields reliable and predictable reduction in the modeled viscosity. The accuracy of the simulations improve as the effective damping is reduced by lowering the specified viscosity providing credibility to the PANS method as a bridging model that performs as intended.
机译：本文提出的工作涉及部分平均Navier-Stokes（PANS）方法的持续开发，验证和验证-湍流的可变分辨率闭合模型。线性涡流粘度模型（LEVM）由于其简单性和在计算成本方面的可承受性而广受欢迎，具有根本缺陷，因此不能可靠地在现实的复杂流动中准确地表示湍流。诸如大涡模拟（LES）和直接数值模拟（DNS）之类的更高保真度的方法由于对计算能力的高要求而超出了工程学的适用范围。 PANS是本研究中考虑的一种可变分辨率方法，在计算成本方面介于LEVM和LES之间，旨在谨慎地利用可用的计算能力来提高准确性。本论文介绍了为表征PANS波动和扩展而进行的各种研究。用于各种壁面边界流的模型。实现我们目标的路线图包括：（i）比较先验和后验涡流粘度值，以确定PANS是否能够产生预先指定的降低水平。 （ii）研究不同级别的规定分辨率下PANS波动的缩放比例，并确定该波动是否遵守已知的湍流缩放定律。 （iii）将PANS扩展到更适合壁边界剪切流的ko公式，以及（iv）修改当前的LEVM，使其在快速变形极限中产生合理的行为，而湍流本质上是弹性的，最终会影响PANS的性能。这篇论文报道的结果表明，PANS封闭可以使模型粘度可靠且可预测地降低。通过降低指定的粘度来降低有效阻尼，从而提高了仿真的准确性，从而为PANS方法提供了可信的桥梁模型，从而达到了预期的效果。

著录项

  • 作者

    Lakshmipathy, Sunil.;

  • 作者单位

    Texas A&M University.;

  • 授予单位 Texas A&M University.;
  • 学科 Engineering Aerospace.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 145 p.
  • 总页数 145
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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