A hybrid subgrid model for large-eddy simulation of compressible wall-bounded flows

0933377马赫该奖项是根据2009年《美国复苏和再投资法案》(第111-5号公法)资助的。PI计划开发一种新的混合壁面模拟策略，用于可压缩壁面边界流的大涡模拟(LES)，在正式开发模型后，将执行附加可压缩边界层的大涡模拟。该模型将通过直接数值模拟(DNS)和实验进行评估。与传统的混合方法不同，PI不会混合近壁RAN(雷诺平均的纳维斯托克斯)区域和远离墙壁的LES区域，相反，他求解直到墙壁的LES方程。他定义了一个新的误差，它是Germano恒定误差(LES误差)的加权和，以及将LES子网格应力的时间平均值与雷诺应力(RANS误差)联系起来的误差。该复合误差被最小化以获得模型系数。定义复合误差中的权重，以使其在LES误差较高的区域(靠近墙壁)中使误差向RANS分量倾斜。因此，该模型不会显式依赖于与墙的距离。LES正在迅速成为各种工程流程的首选方法。这项工作解决了LES的一个阻碍其被接受的关键限制--对附壁边界流的不准确预测。它认识到解决这个问题的流行方法的重要局限性，并计划构建一个适用于亚网格模型的混合模型，而不是本工作中考虑的那些模型。这项工作将由一名博士生和一名本科生完成。PI将参加由来自双城地区的高中生和来自全国各地的暑期实习生参与的外联计划。这项工作将成为PI教材的一部分，以及面向广大受众的演示文稿和文章。

0933377 MaheshThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The PI plans to develop a novel hybrid wall-modeling strategy for large-eddy simulation (LES) of compressible wall-bounded flows, After formally developing the model, hybrid LES of attached compressible boundary layers will be performed. The model will be evaluated against both direct numerical simulation (DNS) and experiment. Unlike conventional hybrid approaches, the PI does not blend near-wall RANS (Reynolds-averaged Navier-Stokes) regions with LES regions away from the wall, Instead, he solves the LES equations down to the wall. He defines a new error that is a weighted sum of the Germano identity error (LES error) and an error that relates the time-average of the LES subgrid stresses to the Reynolds stresses (RANS error). This composite error is minimized to obtain the model coefficient. The weight in the composite error is defined such that it skews the error toward the RANS component in regions where the LES error is high (near walls). As a result, the model does not explicitly depend on distance from the wall. LES is rapidly progressing towards becoming the method of choice for a wide range of engineering flows. This work addresses a key limitation of LES that is hindering its acceptance -- inaccurate predictions of attached wall-bounded flows. It recognizes important limitations in the prevalent approach towards this problem, and plans to construct a hybrid model applicable to subgrid models beyond those considered in this work. This work will be performed by one PhD student and one undergraduate student. The PI will participate in outreach programs involving high school students from the twin cities area, and summer interns drawn from across the country. This work will form part of the PI's teaching material, and presentations and articles intended for a broad audience.