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arXiv 2104.09187physics.flu-dynphysics.comp-ph
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CFD驱动的代数方程组-应力模型的符号识别

CFD-driven Symbolic Identification of Algebraic Reynolds-Stress Models

I. Ben Hassan SaÏdi, M. Schmelzer, P. Cinnella, F. Grasso

摘要:

基于[1]中的冻结训练SpaRTA算法,提出了一种CFD驱动的确定性符号识别算法,用于从高保真数据中学习显式代数应力模型(EARSM)。雷诺应力张量和生产的基线线性涡粘性模型(LEVM)的传输湍流量的修正表示为从候选函数库中选择的张量多项式的函数。CFD驱动的训练包括解决黑盒优化问题,其中通过运行RANS模拟来评估候选EARSM模型的适应度。与冻结训练方法不同,所提出的方法并不限于高保真数据的全字段可用的数据集。然而,高维昂贵的黑盒函数优化问题的解决方案是必需的。然后采取几个步骤来减少相关的计算负担。首先,使用敏感性分析来识别最有影响力的术语并降低搜索空间的维度。之后,约束优化使用响应面(CORS)算法,它近似的黑箱成本函数使用响应面构造从有限数量的CFD解决方案,是用来找到最佳的模型参数。用不同的训练数据集对三种变截面通道二维湍流分离流进行了模型发现和交叉验证,以显示该方法的灵活性。发现的模型,然后应用到一个看不见的2D分离流与更高的雷诺数和不同的几何形状的预测。新情况下的预测不仅比基线LEVM更准确,而且是一个多用途的EARSM模型来自纯物理参数。

英文摘要:

A CFD-driven deterministic symbolic identification algorithm for learning explicit algebraic Reynolds-stress models (EARSM) from high-fidelity data is developed building on the frozen-training SpaRTA algorithm of [1]. Corrections for the Reynolds stress tensor and the production of transported turbulent quantities of a baseline linear eddy viscosity model (LEVM) are expressed as functions of tensor polynomials selected from a library of candidate functions. The CFD-driven training consists in solving a blackbox optimization problem in which the fitness of candidate EARSM models is evaluated by running RANS simulations. Unlike the frozen-training approach, the proposed methodology is not restricted to data sets for which full fields of high-fidelity data are available. However, the solution of a high-dimensional expensive blackbox function optimization problem is required. Several steps are then undertaken to reduce the associated computational burden. First, a sensitivity analysis is used to identify the most influential terms and to reduce the dimensionality of the search space. Afterwards, the Constrained Optimization using Response Surface (CORS) algorithm, which approximates the black-box cost function using a response surface constructed from a limited number of CFD solves, is used to find the optimal model parameters. Model discovery and cross-validation is performed for three configurations of 2D turbulent separated flows in channels of variable section using different sets of training data to show the flexibility of the method. The discovered models are then applied to the prediction of an unseen 2D separated flow with higher Reynolds number and different geometry. The predictions for the new case are shown to be not only more accurate than the baseline LEVM, but also of a multi-purpose EARSM model derived from purely physical arguments.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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