Novel hybrid LES-RANS schemes for simulating physically and geometrically complex turbulent flows

用于模拟物理和几何复杂湍流的新型混合 LES-RANS 方案

• 批准号: EP/H01070X/1
• 负责人: Michael Leschziner
• 金额: $ 38.85万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FH01070X%2F1
• 关键词: Novel; hybrid; LES; RANS; schemes

Large Eddy Simulation (LES) is gradually replacing traditional Reynolds-averaged-Navier-Stokes (RANS) modelling as the method of choice for predicting complex turbulent flows in research as well as industrial practice. This is especially so when unsteady phenomena are to be resolved (vibrations, acoustics, thermal striping, pressure peaks). However, the exploitation of LES for predicting practical wall-confined flows, particularly those involving separation from curved surfaces, is seriously inhibited by practically untenable resource requirements at high Reynolds numbers. Hybrid LES-RANS schemes, employing some form of RANS-like solution in the near-wall region, are generally regarded as a compromise strategy circumventing the resource obstacle. Existing schemes are based on the use of RANS models that operate in unsteady mode, as they are subjected to high amplitude, high-frequency fluctuations imposed on the layer by the outer LES solution. These models thus operate far outside their intended range of applicability. Moreover, in most approaches, the small-scale motions not resolved explicitly by the LES are represented by an ill-defined blend of subgrid-scale and RANS turbulence models - i.e. there is no clear dividing line between the LES and RANS components. Not surprisingly, such models display a whole range of disconcerting defects.This submission proposes a collaboration between two groups who have been at the forefront of developing RANS-LES schemes in the UK. Indeed, the two groups are the only UK academic partners who have participated in the four-year EU FP6 project DESider, specifically devoted to RANS-LES modelling for industrial applications, and in the follow-up 22-partner FP7 project ATAAC (Advanced Turbulence Simulation for Aerodynamic Application Challenges). Electricite de France (EDF) will support the programme to the level of one man-year of PDRA.The proposed project aims specifically at LES-RANS hybrids that distinguish carefully between the LES and RANS elements, each applied subject to appropriate, well-established constrains and coupled rationally. The project involves two major strands: (i) the development of a novel zonal (two-layer) scheme, which entails the solution of steady, parabolized RANS equations, subject to on-the-fly time-averaged constraints derived from the LES solution, and the use of an anisotropy-resolving turbulence model over a thin near-wall layer superimposed onto the LES domain; (ii) the integration and validation of (i), as well as an extended version of a newly-developed RANS-LES hybrid (Uribe et al [2007]), which shares some basic concepts with proposed model under (i), into a state-of-the-art numerical framework (Saturne), which is promoted by EPSRC's CCP12 as a general prediction tool for computing turbulent flows in very complex geometries on HPCx and HECTOR. A key characteristic of Uribe et al's model is that it respects the need to separate the RANS-derived Reynolds stresses from the inherently unsteady LES, and to desensitize the resolved perturbations and the subgrids-scale stresses from the RANS model. To that extent, the model is based on the same philosophy underpinning the zonal scheme to be developed, although the two models differ radically in respect of their design.

大涡模拟（LES）正逐渐取代传统的雷诺平均纳维尔-斯托克斯（RANS）模型，成为研究和工业实践中预测复杂湍流流动的首选方法。当需要解决不稳定现象（振动、声学、热条纹、压力峰值）时，情况尤其如此。然而，开发LES预测实际的壁面约束流，特别是那些涉及分离曲面，严重抑制了实际上站不住脚的资源要求在高雷诺数。混合LES-RANS格式在近壁区域采用某种形式的RANS解，通常被认为是一种绕过资源障碍的折衷策略。现有的计划是基于使用RANS模型，在非定常模式下运行，因为它们受到高振幅，高频波动施加在层上的外部LES解决方案。因此，这些模式的运作远远超出了其预期的适用范围。此外，在大多数方法中，LES未明确解决的小尺度运动由亚网格尺度和RANS湍流模型的不明确混合表示-即LES和RANS分量之间没有明确的分界线。毫不奇怪，这样的模型显示出一系列令人不安的缺陷。这份提交文件提出了两个小组谁一直在英国发展RANS LES计划的最前沿之间的合作。事实上，这两个小组是唯一参与为期四年的欧盟FP 6项目DESider的英国学术合作伙伴，专门致力于工业应用的RANS-LES建模，以及后续的22个合作伙伴FP 7项目ATAAC（空气动力学应用挑战的高级湍流模拟）。法国电力公司（EDF）将支持该计划的一个人-年的PDRA的水平。拟议的项目的具体目标是LES-RANS混合，仔细区分LES和RANS元素，每个应用受到适当的，完善的约束和合理的耦合。该项目包括两个主要方面：（i）开发一个新的区域性（两层）方案，该方案需要求解稳定的抛物化RANS方程，受到来自LES解的动态时间平均约束，并在叠加到LES域上的薄近壁层上使用各向异性分辨湍流模型;（ii）（i）的集成和验证，以及新开发的RANS-LES混合的扩展版本（Uribe等人[2007]），它与（i）项下提出的模型共享一些基本概念，将其纳入最先进的数值框架（Saturne），EPSRC的CCP 12将其作为一种通用的预测工具，用于在HPCx和HECTOR上计算非常复杂几何形状的湍流。Uribe等人的模型的一个关键特征是，它尊重将RANS导出的雷诺应力与固有的非定常LES分离的需要，并降低RANS模型的解析扰动和亚网格尺度应力的敏感性。在这方面，这一模式是基于支持将制定的分区计划的相同理念，尽管这两种模式在设计方面有着根本的不同。

项目成果

Investigation of second-moment-closure defects in separated boundary layer by reference to highly-resolved LES data, Proc. , Ottawa, Canada.

参考高分辨率 LES 数据研究分离边界层中的二阶矩闭合缺陷，Proc。

• 发表时间: 2011
• 期刊: Turbulence and Shear Flow Phenomena 7
• 作者: Y. Bentaleb

The structure of a three-dimensional boundary layer subjected to streamwise-varying spanwise-homogeneous pressure gradient

流向变翼展均匀压力梯度下三维边界层结构

• DOI: 10.1016/j.ijheatfluidflow.2013.05.010
• 发表时间: 2013
• 期刊: International Journal of Heat and Fluid Flow
• 影响因子: 2.6
• 作者: Bentaleb Y

Large-eddy simulation of turbulent boundary layer separation from a rounded step

• DOI: 10.1080/14685248.2011.637923
• 发表时间: 2012-01-01
• 期刊: JOURNAL OF TURBULENCE
• 影响因子: 1.9
• 作者: Bentaleb, Yacine;Lardeau, Sylvain;Leschziner, Michael A.
• 通讯作者: Leschziner, Michael A.