基于CFD降尺度的大气边界层复杂地形风场精细数值模拟

For the assessment of wind energy, atmospheric environmental impact and meteorological disaster risk,it is important to understand the characteristics of wind field near the surface layer. For a long time, many scholars study the wind field on the complex terrain by different observation and theoretical methods. CFD (Computational Fluid Dynamics) method has rich physical model and fine mesh generation technology. In this project, it will be coupled with mesoscale model to downscaling simulate the fine wind field structure of complex terrain. The CFD model named FLUENT will be used to simulate complex terrain flow, and turbulence, intermittent structure, vortex generation and distribution. The high-precision digital elevation data and aerodynamic roughness will be imported. The wall stress is set. And the high-precision grid will be established. The dynamic boundary and initial conditions will be provieded by mesoscale model results. The LES model is adopted. The temperature stratification model is introduced. We will statistically analyse the fine structure and compare it with the experimental observations.We will use wavelet signal decomposition and reconstruction technique and multi-scale analysis to extract the gust coherent structure, and use the quadrant analysis to study the eject and sweep of gust structure. It will provid the basis for the establishment of the complex terrain boundary layer theory.

了解近地层风场特征，对于风能评估、大气环境影响评价以及气象灾害风险评估等有着重要意义，长期以来许多学者通过不同方法对复杂地形风场特征进行了大量的观测和理论研究，本项目利用CFD(Computational Fluid Dynamics)方法丰富的物理模型和精细网格生成技术，与中尺度模式耦合，降尺度计算复杂地形的精细风场结构。在CFD模式FLUENT中导入高精度的地形高程数据和空气动力学粗糙度，结合壁面应力的设置，建立高精度网格，以中尺度模式计算结果提供动态边界和初始条件，采用LES模式，引入温度层结的物理模型模拟复杂地形的湍流脉动、间歇结构、涡旋的产生和输送等小尺度的精细结构，并对其进行统计分析，将统计结果与实验观测进行对比。还将在数值模拟的基础上，采用子波信号分解重构和多尺度分析技术提取阵风的相干结构，并通过象限分析法分析阵风结构的上抛、下扫运动过程，为建立复杂地形边界层理论提供依据。

了解近地层风场特征，对于风能评估、大气环境影响评价以及气象灾害风险评估等有着重要意义，本项目利用CFD与中尺度模式耦合，降尺度计算复杂地形的精细风场结构。在CFD模式FLUENT中导入高精度的地形高程数据，建立高精度网格，以中尺度模式计算结果提供动态边界和初始条件，模拟复杂地形的湍流脉动、间歇结构、涡旋的产生和输送等小尺度的精细结构，并对其进行统计分析，将统计结果与实验观测进行对比，分析阵风相干结构的物理图像和产生条件，有助于风能预报中对风场中阵风等相干结构进行预报，提高风能预报的准确性。