"Database of Large Eddy Simulation for Complicated Turbulent Flows"

本项目的目的是利用最新的湍流模型和数值方法，采用高精度的大涡模拟(LES)，建立一个用于湍流研究的数据库。为了开发各种湍流大涡模拟的数值方法和亚网格尺度(SGS)模型，对最新提出的SGS模型提供了一些验证数据，a)有限差分和有限元格式中的动态SGS模型，b)Yoshizawa提出的非平衡SGS模型。根据这些结果，开发和改进了数值程序来分析七种物体的大涡模拟：1)有/无旋流的圆管流动，2)平面湍流射流，3)壁面冲击射流，4)带有立方湍流发生器的槽道流动，5)方形圆柱体周围的流动和6)具有热分层的房间内的通风。对每个目标进行物理或数值研究，对情况(1)的边界拟合坐标(BFC)网格对大涡模拟进行验证，对情况(2)的边界条件发展数值方法，对情况(3)、(4)和(5)的SGS模式进行验证，(4)和(5)情况(4)和(5)的对流项的迎风格式的影响估计。在所有情况下，将平均速度、湍流强度和类似物的分布作为统计量存储在LES数据库中。此外，还计算了与实验数据相比更详细的湍流能量平衡数据(例(3))和准周期湍流(例(5))的相平均值。为了分析这些流动的结构特征，计算机图形学和动画也提供了二维和三维可视化。

An aim of this project was to build a database for turbulent researches by using a large eddy simulation (LES) in a high accuracy approxmation with the latest turbulence models and numerical methods. The database was expected to include both the statistical variable data and the structural characteristics of turbulent flows.For developing the numerical methods and the subgrid scale (SGS) models for the large eddy simulation of various turbulent flows, some verification data were indicated for the latest proposed SGS models, a) a dynamic SGS model in the FDM and FEM formulation, b) a non-equilibrium SGS model proposed by Yoshizawa. According to these results, numerical programs were developed and improved to analyze the LES for seven objects ; 1) circular pipe flows with/with-out swirl, 2) a plane turbulent jet, 3) a wall impinging jet, 4) a channel flow with a cubic turbulent generator, 5) a flow around square cylinder and 6) a ventilation in the room with thermal stratified layr. Each object is researched with a physical or a numerical interest, a validation of LES by a boundary fitted coordinate (BFC) grid for case (1), development of numerical methods for boundary conditions for case (2), validations of SGS models for cases (3), (4) and (5), estimations of the affects by upwind schemes for convection terms for cases (4) and (5). For all cases, profiles of mean velocities, turbulent intensities and likes as statistical quantities are stored in the database of LES.Additionally, more detail data like a budget of turbulent energy compared with experimental data for the wall impinging jet (case (3)) and phase averaged quantities for the quasi-periodic turbulent flow (case (5)) were calculated. For analyzing the structural characteristics of these flows, two-and three-dimensional visualization were offered by the computer graphics and some by the animation, too.