桥梁气动力数值模拟中湍流理论、湍流模型的应用基础研究

Turbulence theory is fundamental to the numerical turbulence models involved in Computational fluid dynamics (CFD). The CFD method would, based on the trend of rapid development in the field of computer science, enter progressively into all sorts of bridge aerodynamic issues of high Reynolds numbers and complex flow properties. However, to date, the function of CFD simulation is still auxiliary, and cannot replace the wind tunnel experiments and hence incapable of playing an independent role in the bridge aerodynamic design. This situation is mainly due to lack of systematic investigations of the typical turbulence numerical models in regard to their applicability, accuracy, and rational usages when they are applied to sorts of bridge aerodynamic issues. In the current application, four types of bridge aerodynamic issues are proposed, including mean wind loads, vortex-induced aerodynamic loads, self-excited aerodynamic loads, buffeting loads and aerodynamic interference. Around these four types of issue and by means of turbulence theory, wind tunnel experiments, DNS and LES-NWR simulations, etc., investigations of turbulence models developed in CFD are planned around their applicability, accuracy of simulation, and rational usages. The research planned in this application could contribute in the future to the formation of a reference guide on the usages of turbulence models in the bridge “numerical wind tunnel”.

湍流理论是计算流体动力学（CFD）中湍流数值模型的基础。从计算机运算速度快速发展的趋势来看，CFD方法有能力逐步进入高雷诺数的、复杂的各类桥梁风工程气动问题的研究。另一方面，目前CFD的实际作用仍然是辅助性的，还不能替代风洞试验对桥梁抗风设计起到独立的指导作用。其主要原因是，围绕各类湍流数值模型的适用范围、模拟精度、合理使用方法等方面，对桥梁的各类典型气动力问题缺少系统的研究。本项目拟将桥梁计算风工程分成平均风荷载、涡激气动力、自激气动力、抖振力及气动干扰共四类典型问题，在此基础上采用湍流理论定性研究、风洞试验、DNS模拟、LES-NWR模拟等手段对CFD中各类常用的湍流数值模型的适用范围、模拟精度以及合理使用方法进行研究。本项目的研究有助于推动将来桥梁“数值风洞”中湍流数值模型参考指南的形成。

桥梁抗风性能主要涉及到二维钝体结构的气动力性能，通常采用风洞试验来确定。计算流体动力学模拟目前仍然是辅助工具，主要原因是湍流问题的处理。在CFD理论中，关于湍流模型存在许多分支，每一理论有其独自特点与适用范围，因此围绕典型桥梁断面与气动力问题展开湍流模型的研究是有应用价值的。本项目针对大跨度桥常用的扁平箱形断面、双主梁断面、中央开槽断面以及类平板断面的自激气动力、涡激力等方面展开研究，指出了各类湍流模型在应用到这些方面时的优缺点，为今后采用CFD数值风洞代替物理风洞时提供参考。从气动力相位变化特性方面研究了桥梁断面在气流中能量吸收或耗散的机制，指出决定气弹现象的本质并非流态，而是相位差。提出了多阶段阶跃函数描述的非线性气动力理论，建立了大跨度桥梁非线性后颤振数值分析的理论与方法。