论文标题
Lagrangian大型涡流模拟通过物理知情的机器学习
Lagrangian Large Eddy Simulations via Physics Informed Machine Learning
论文作者
论文摘要
高雷诺在Navier-Stokes(NS)方程中充分描述了均质的各向同性湍流,众所周知,这些方程很难在数值上求解。工程师主要有兴趣描述降低的分辨率范围的湍流,它设计了启发式方法,称为大型涡流模拟(LES)。 LE是用时间不断发展的欧拉速度场来描述的,该速度场是在空间网格上定义的,其平均间隔对应者是分辨率量表的。这个经典的欧拉尔(Eulerian Les)取决于对亚网格尺度对解决量表的影响的假设。 在这里,我们采用了另一种方法,并设计了通过拉格朗日颗粒随流动的拉格朗日颗粒而设计的。我们的Lagrangian LES(因此L-LE)是通过将弱压缩的平滑粒子流体动力学制定的方程来描述的,并通过扩展的参数和功能自由来通过从NS方程的直接数值模拟对Lagrangian数据进行机器学习训练来解决。 L-LES模型通过结合基于物理学的参数和物理启发的神经网络来描述鳞片范围内湍流的演变,包括物理信息的参数化和功能形式。亚网格量表的贡献是通过物理约束分别建模的,以说明未解决的量表的影响。我们在可区分的编程框架下建立了最终的模型,以促进有效的培训。我们试验了不同类型的损失功能,包括对Lagrangian颗粒统计的物理信息的损失功能。我们表明,我们的Lagrangian LES模型能够在一系列湍流的马赫数上复制Eulerian和独特的Lagrangian湍流结构和统计。
High Reynolds Homogeneous Isotropic Turbulence is fully described within the Navier-Stokes (NS) equations, which are notoriously difficult to solve numerically. Engineers, interested primarily in describing turbulence at a reduced range of resolved scales, have designed heuristics, known as Large Eddy Simulation (LES). LES is described in terms of the temporally evolving Eulerian velocity field defined over a spatial grid with the mean-spacing correspondent to the resolved scale. This classic Eulerian LES depends on assumptions about effects of sub-grid scales on the resolved scales. Here, we take an alternative approach and design novel LES heuristics stated in terms of Lagrangian particles moving with the flow. Our Lagrangian LES, thus L-LES, is described by equations generalizing the weakly compressible Smoothed Particle Hydrodynamics formulation with extended parametric and functional freedom, which is then resolved via Machine Learning training on Lagrangian data from Direct Numerical Simulations of the NS equations. The L-LES model includes physics-informed parameterization and functional form, by combining physics-based parameters and physics-inspired Neural Networks to describe the evolution of turbulence within the resolved range of scales. The sub-grid scale contributions are modeled separately with physical constraints to account for the effects from un-resolved scales. We build the resulting model under the Differentiable Programming framework to facilitate efficient training. We experiment with loss functions of different types, including physics-informed ones accounting for statistics of Lagrangian particles. We show that our Lagrangian LES model is capable of reproducing Eulerian and unique Lagrangian turbulence structures and statistics over a range of turbulent Mach numbers.