论文标题
湍流的晶格涡流模拟
Lattice eddy simulation of turbulent flows
论文作者
论文摘要
Kolmogorov(1941)的自相似性理论意味着小规模涡流的普遍性,并且对大型涡流模拟的通用子网格量表模型抱有希望。事实是典型的子网格量表模型的经验系数在游离湍流中从0.1到0.2不等,逐渐湿至零接近墙壁。这项工作开发了一种晶格涡模拟方法(LAES),其中唯一的经验系数是恒定的(CS = 0.08)。 LAES假设流体特性存储在典型的CFD网格的节点中,将节点视为晶格,并在一个特定的晶格上进行分析。具体来说,Laes表达了该晶格上的域衍生物,并具有附近晶格的影响。 i旁边的晶格(命名为i+)与i相撞,对i产生了对流效果。 I+旁边的晶格(称为i ++)对i+产生对流效果,并间接影响i。影响实际上是湍流的扩散。 LAE的派生的控制方程看起来像Navier-Stokes方程,并用Smagorinsky子网格量表模型(Smagorinsky 1963)与各向同性细胞的网格级别减少到过滤的Naiver-Stokes方程。 LAE在RE = 180、395和590上的湍流通道流的准确预测非常粗糙,并且具有恒定CS的LAE和动态LES模型(Germano etal。1991)的表现。因此,这项工作为Kolmogorov的自相似性理论提供了有力的证据。
Kolmogorov's (1941) theory of self-similarity implies the universality of small-scale eddies, and holds promise for a universal sub-grid scale model for large eddy simulation. The fact is the empirical coefficient of a typical sub-grid scale model varies from 0.1 to 0.2 in free turbulence and damps gradually to zero approaching the walls. This work has developed a Lattice Eddy Simulation method (LAES), in which the sole empirical coefficient is constant (Cs=0.08). LAES assumes the fluid properties are stored in the nodes of a typical CFD mesh, treats the nodes as lattices and makes analysis on one specific lattice, i. To be specific, LAES express the domain derivative on that lattice with the influence of nearby lattices. The lattices right next to i, which is named as i+, "collide" with i, imposing convective effects on i. The lattices right next to i+, which is named as i++, impose convective effects on i+ and indirectly influence i. The influence is actually turbulent diffusion. The derived governing equations of LAES look like the Navier-Stokes equations and reduce to filtered Naiver-Stokes equations with the Smagorinsky sub-grid scale model (Smagorinsky 1963) on meshes with isotropic cells. LAES yields accurate predictions of turbulent channel flows at Re=180, 395, and 590 on very coarse meshes and LAES with a constant Cs perform as well as the dynamic LES model (Germano et al. 1991) does. Thus, this work has provided strong evidence for Kolmogorov's theory of self-similarity.