复杂地形强风特性数值模拟的数理模型的研究

Wind characteristics over complex topography is very important for wind resistant design of wind sensitive structures like long span bridges and high rise buildings. The turbulent flow over complex topography involves complicated flow phenomena such as spatial development, stable or unstable separation and reattachment according to the hill slope, and downstream recovery of the turbulent boundary layer, thus any disturbance that may influence the behavior of the separated shear layer and its interaction with the ground would change the global and local turbulent structure and then influence the wind characteristics around complex topography. With the increased concern over the wind loading problems in hilly terrains, there is an urgent demand to predict the gusty wind over complex topography numerically. This proposal aims to establish a sophisticate numerical model to predict the characteristics of the gusty wind over complex topography, which carries out unsteady simulation of the three-dimensional incompressible flow by Large-eddy simulation, in conjunction with a meso-scale meteorological model. Several key issues to determine the accuracy of numerical model including the numerical procedure, turbulence models for Large-eddy simulation, roughness effect and its modeling and the method to combine the CFD model with metrological model will be studied in detail. Particularly, high order accuracy difference schemes will be adopted to discretize the governing equations of fluids in generalized coordinate system; The Smagorinsky type eddy-viscosity model and non-Smagorinsky type scale similarity model will be utilized to model the subgrid-scale turbulence. Immersed boundary method will be studied to model the effects of roughness elements on the surface of topography. The combination of Large-eddy simulation with meso-scale model is a big challenge of this proposal. Meanwhile, wind tunnel tests and/or field measurements will be conducted to study the wind characteristics over isolated two-dimensional and three dimensional hill models and real topographies, as well as providing wind tunnel and field data to validate the numerical model. Validation will be performed not only on the wind statistics but also instantaneous turbulence structures of the flow. This proposal satisfies the necessities to improve the science and technology related to the wind resistant design of wind sensitive structures and has obvious significance for both fundamental and applications to wind engineering field.

强风特性是决定大跨桥梁和高层建筑等风敏感结构风致响应的关键因素之一，对在复杂地形区域建设的风敏感结构进行可靠的抗风设计的前提是准确地预测该建设场地的平均和脉动风特性。本项目的研究目标是建立以计算流体力学模型为主导、结合中尺度气象模型，以模拟复杂地形强风特性为目的、适应抗风设计需要的高精度数理模型。该高精度数理模型支持基于有限差分法、采用大涡湍流模拟的3维大规模非定常计算。本项目在明确坡度、湍流度和地表粗糙度等要素在决定山区强风场特性中的物理作用的同时，通过研究基于曲线坐标和差分法的高精度数值模拟方法、湍流模型、气象模型与大涡模型的融合以及地表粗糙度的模拟方法等关键科学问题来建立复杂地形强风特性模拟的数理模型，并通过对孤立山峰和复杂地形的风洞试验和现场实测来验证该数理模型的精度和可靠性。本项目针对我国土木工程建设的迫切需要，具有重大的理论价值和工程应用前景。

强风特性是决定大跨桥梁和高层建筑等风敏感结构风致响应的关键因素之一，对在复杂地形建设的风敏感结构进行可靠的抗风设计的前提是准确地预测该建设场地的平均和脉动风特性。本项目的主要研究内容是建立以计算流体力学模型为主导、结合中尺度气象模型，以模拟复杂地形强风特性为目的、适应抗风设计需要的高精度数理模型。本项目的重要结果包括以下三个方面的内容：1）明确了山坡坡度、湍流度和地表粗糙度等要素在决定山区强风特性中的物理作用，指出了建立模拟复杂地形强风特性的数理模型时必须考虑模拟这些要素的作用；2）通过循环再流入的技术手段在微分求积方法的框架下实现了具有保持性的流入脉动风的模拟；通过浸入边界方法实现了地面粗糙度的模拟；建立了基于有限差分法、采用大涡湍流模拟的3 维非定常高精度数值模拟方法计算并应用于实际复杂地形；3）在气象模型的大框架下实现了气象模型和大涡湍流模型的融合。但研究结果表明，这种融合并不能满足结构抗风研究的需要。今后的研究中需要尝试在计算风工程的大框架下实现气象模型和大涡湍流模型的融合。本项目针对我国土木工程建设的迫切需要，具有重大的理论价值和工程应用前景。. 在执行课题的4年期间在本行业最高水准的国际学术杂志上发表了标注本课题的SCI论文6篇。参加国际会议并发表标注本课题的学术论文3次以上。培养博士生1名和硕士生1名。