基于CFD/CSD的大柔性机翼静气动弹性研究

Numerical Research on Static Aeroelasticity of Highly Flexible Wing Based on CFD/CSD Coupling

摘要:

高空长航时无人机采用轻质大展弦比机翼，机翼具有相当大的柔性，结构受载前后几何构型呈现明显的差异，在 CFD/CSD 法建模分析时存在网格生成难度大、网格数量难以控制的问题。针对该问题，提出一种基于非结构化网格的 CFD/CSD 松耦合方法，在 CFD 建模时，采用非结构化四面体 CFD 网格，生成网格容易且数量少；在 CSD 方面，通过求解静力学方程，仅需几个耦合步就可得到稳定平衡状态，计算效率有了本质提高。结果表明：耦合使用的非结构化 CFD 网格经详细 CFD 网格验证，在机翼失速前具有较高的精度；在小迎角下，同传统面元法引入翼型修正后得到气动力系数和弹性修正系数相符，随着迎角的增大，该方法可考虑大变形引起的几何非线性、曲面气动力及考虑一定的流动分离，计算效率高，具有较高的工程应用价值。

Abstract:

High altitude long-endurance UAV uses lightweight wings, which are highly flexible. The wings are significantly different in shape before and after being loaded. It is difficult to generate the meshes and to control the meshes’ quantity. To solve these problems, this paper adopts the unstructured CFD meshes and couples the static mechanics solving program. Just in a few coupling steps, the analysis converged to the stable equilibrium state. The CFD’s meshes used in coupling have high fidelity under the wing’s stall angle, which is verified by fine meshes. When the angle of attack is small, the CFD/CSD coupling results agree with traditional panel method when taking airfoil into account. When the angle of attack increases, the CFD/CSD coupling method can simulate a certain degree of separation. What’s more, this method can count geometric nonlinearity and aerodynamic forces of curved surface. In addition, the CFD/CSD coupling method is efficient and worth promoting.