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Thermal lattice Boltzmann simulations of variable Prandtl number turbulent flow.

机译：可变Prandtl数湍流的热晶格Boltzmann模拟。

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摘要

With the advent of massively parallel processor machines, thermal lattice Boltzmann equation (TLBE) techniques offer an attractive way of handling turbulence simulations. TLBE is new form of DNS (direct numerical simulation method)--with the important advantages of being ideal for multi-parallel processors as well as being able to handle complicated geometries. Since there are many kinetic models that will reproduce the macroscopic nonlinear (compressible) transport equations, TLBE chooses that subset which can be readily solved on a discrete spatial lattice. The lattice geometry must be so chosen that the discrete phase representation of TLBE will not taint the rotational symmetric continuum equations. For 2D compressible flows, linear stability analyses described in this work indicates that the hexagonal lattice is optimum.; In nearly all lattice Boltzmann literature, the linearized Boltzmann collision operator has been taken to be the simple single-time Krook relaxation collision operator. This scalar collision operator is sufficient to recover the nonlinear transport equations under Chapmann-Enskog expansions. However, all previous LBE have suffered from the problem of density dependent transport coefficients. Even though this poses no problem for incompressible flows, it is critical and must be handled for compressible fluid simulations. The other deficiency of conventional TLBE scheme with single relaxation operator is that it only allows for fixed Prandtl number flow simulations.; In this work, to simulate flows with arbitrary Prandtl number, a matrix collision operator is introduced. With the inclusion of additional free parameter in the off-diagonal components, the scheme is now extended to a multi-relaxation process. This allows generalizations on relaxation parameters to produce density independent transport coefficients. Explicit solutions of TLBE are presented for 2D free decaying turbulence.
机译：随着大规模并行处理器机器的问世，热晶格玻尔兹曼方程（TLBE）技术提供了一种有吸引力的处理湍流模拟的方法。 TLBE是DNS（直接数值模拟方法）的一种新形式-其重要优点是非常适合多并行处理器，并且能够处理复杂的几何图形。由于有许多动力学模型可以再现宏观非线性（可压缩）传输方程，因此TLBE选择可以在离散空间晶格上轻松求解的子集。必须选择晶格几何形状，以使TLBE的离散相位表示不会污染旋转对称连续方程。对于二维可压缩流，本文描述的线性稳定性分析表明六边形晶格是最佳的。在几乎所有的格子Boltzmann文献中，线性化的Boltzmann碰撞算子都被视为简单的单次Krook弛豫碰撞算子。该标量碰撞算子足以恢复Chapmann-Enskog展开下的非线性输运方程。然而，所有先前的LBE都遭受了密度依赖的传输系数的问题。即使这对于不可压缩的流动没有问题，它也很关键，必须在可压缩流体模拟中加以处理。具有单个松弛算子的常规TLBE方案的另一个不足是，它仅允许进行固定的Prandtl数流模拟。在这项工作中，为了模拟具有任意Prandtl数的流，引入了一个矩阵碰撞算子。通过在非对角线组件中包含其他自由参数，该方案现已扩展到多松弛过程。这允许对松弛参数进行概括以产生密度无关的传输系数。提出了针对二维自由衰减湍流的TLBE显式解。

著录项

  • 作者

    Soe, Min.;

  • 作者单位

    The College of William and Mary.;

  • 授予单位 The College of William and Mary.;
  • 学科 Physics Fluid and Plasma.
  • 学位 Ph.D.
  • 年度 1997
  • 页码 99 p.
  • 总页数 99
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 等离子体物理学;
  • 关键词

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