柔性层状材料在复杂流动中的颤振机理研究

Unstable of aerodynamics and structural failure often occurs that when the flexible thin plate is applied in vehicle due to flutter. The reason is the mechanism of dominated restoring force in flutter of the flexible thin plate is still vague. This project will focus on these works: (1) Design and build a high-velocity soap film equipment. Study the unsteady flapping mode of flexible thin plate immersed in complex flow field by using flow visualization technique. Effect of mass ratio. Reynold number, tensile/bending rigidity et al. on the flutter boundary will be studied experimentally. (2) Propose several theoretical assumptions based on the experimental results. The control equation of the flexible thin plate can be formed by modal coordinate methods or finite element methods. Study the loading of anisotropic force in complex flow field. Establish the theory model of flutter of a flexible thin plate. (3) Base on the experimental research and theoretical study, represent the forming of dominated restoring force as well as competition between restoring force and aerodynamic force when the flexible plate experiences flutter. Reveal the flutter mechanism and energy transfer pattern of the flexible thin plate. Basically, this research is beneficial to development of flutter theory for flexible thin plate. And it will provide a basis for application and design of flexible thin plate in several fields, especially in novel flight vehicle and flexible damage element.

柔性层状材料应用于飞行器中时运动轨迹难以预测，易出现颤振导致的气动性能不稳定和结构破坏等现象，原因在于颤振时起主导作用的恢复力的形成机制尚不清楚。本项目拟针对此问题开展以下研究：（1）设计高速薄膜水洞试验装置，通过流场可视化试验研究柔性层状材料在复杂流场中的颤振规律，并进一步研究流固质量比、雷诺数、材料弯曲刚度等参数对其颤振边界的影响；（2）基于试验研究结果提出合理的假设，采用模态坐标法/有限元法构造柔性层状材料的控制方程，研究复杂流场中各向异性力的加载方法，建立柔性层状材料颤振的理论模型；（3）结合试验与理论研究，讨论柔性层状材料发生颤振时起主导作用的恢复力的形成机理及其与气动力的耦合作用原理，揭示柔性层状材料在复杂流动中的颤振机理和能量转移规律。本项目的研究成果将有利于发展柔性层状材料在复杂流动中的颤振理论，为柔性层状材料在新型飞行器和柔性毁伤元等方面的应用与设计提供科学依据。

柔性层状材料应用于飞行器中时运动轨迹难以预测，易出现颤振导致的气动性能不稳定和结构破坏等现象，本项目针对柔性层状材料在复杂流场中的颤振问题开展了试验、仿真及理论研究：（1）研制了高速薄膜竖直水洞试验装置，开展了柔性丝线的颤振试验研究，分析了临界速度的迟滞性，获得了丝线的弯曲刚度、长度、直径、流场的速度等因素对摆动频率及振幅的影响，对预测频率的理论模型进行了修正，修正后的模型与试验结果吻合较好；（2）基于IB-LBM方法建立了柔性材料在流场中运动的流固耦合模型和算法，研究了边界效应对颤振频率及振幅的影响，与刚性材料不同的是随着边界距离的减小，柔性材料的颤振频率变化不明显，振幅逐渐减小；（3）基于Argentina理论对颤振频率公式进行了修正，提出了预测颤振边界的理论模型，对柔性材料的临界速度和临界长度进行了预测与分析。通过本项目的研究，进一步发展了柔性层状材料在复杂流动中的颤振理论，并研制了高速薄膜水洞试验装置，建立了有效的试验测试方法，后续可为柔性层状材料的试验研究和应用设计提供科学依据。