弹性空腔可压缩流动的剪切层不稳定性及振荡机理研究

The compressible flow over a cavity produces complex flow phenomena, which always involve intense aerodynamic load with several resonant frequencies. The load in such kind of flow can bring about structural damage to an aircraft, and its combat effectiveness may be severely affected. Characteristics of the compressible flow and structural vibration during interaction between a high-speed flow and elastic cavities with thin walls will be investigated through wind-tunnel experiments and theoretical analysis. Flow visualization, measurements of pressure fluctuation and vibration, analysis on spectrum and instability are conducted to obtain time-average and dynamic features of the interaction. Results provide access to study on instability of vortical perturbations and evolution of wave patterns, which can be used to reveal elastic boundaries’ effects on the feedback of vortical perturbations and the Kelvin-Helmholtz instability in a cavity flow. Based on similarity principal of aerodynamics and vibrations, we will investigate the interaction between elastic cavity walls and aerodynamic load. The present work is expected to shed light on coupling of unsteady flow, vibration and noise in a high-speed aircraft, as well as structural design and oscillations control of internal weapon bays.

高速空腔诱导的可压缩流动结构十分复杂，流场中经常形成高强度且多频率分量的动载荷激励，不仅加速了空腔薄壁结构的疲劳破坏，还可能引发结构共振，严重危及飞行器系统结构安全和作战效能提高。.本申请拟针对弹性空腔可压缩流动的剪切层不稳定性及振荡机理开展研究，以典型薄壁结构空腔为研究对象，通过风洞流场显示、非定常流动/振动特性测量、频谱分析和不稳定性分析等多种研究手段，获取弹性空腔可压缩流动时均/动态特性以及腔体结构振动特性，分析流场中涡扰动增长特性和波系演化规律，揭示弹性边界对扰动反馈回路和剪切层Kelvin-Helmholtz不稳定性的影响机制，阐明弹性空腔非定常气动激励对腔体结构振动的作用规律，研究空腔可压缩流动与结构振动相互作用机理，为探索飞行器非定常流动/振动/噪声耦合机理等前沿基础问题和解决内埋武器系统振动与噪声控制等工程实际问题提供技术储备。

空腔流场中经常存在高强度且多频率分量噪声，引起空腔噪声载荷与结构振动之间的耦合效应，甚至引发结构共振，危及飞行器系统结构安全和作战效能提高。本项目通过风洞实验和理论分析，以弹性空腔为研究对象，模拟了空腔流致噪声与结构振动相互作用问题。基于相似原理，构建了弹性空腔多物理场特性风洞试验模拟方法，搭建了适用于空腔多物理场特性研究的综合测试平台。采用流场显示、非定常流动/振动特性测量、频谱分析等研究手段，开展弹性空腔高速风洞试验，获取了弹性空腔可压缩流动时均/动态特性以及腔体结构振动特性；开展空腔多场数据天地相关性分析并发展了数据修正方法，建立了多物理场动态数据综合处理方法；分析了弹性空腔流动、振动和噪声特性，以及流场中涡扰动增长特性和波系演化规律，揭示弹性边界对空腔扰动增长的影响机制，阐明弹性边界约束下空腔扰动增长回路与结构振动相互作用原理。结果显示，在弹性空腔声振耦合问题中，当振动强度较弱时，结构振动对空腔噪声影响较小，随着振动强度提高，空腔噪声载荷受到影响增强。在噪声载荷主频位置，空腔结构振动谱出现峰值并且噪声/振动相关性达到最强；空腔结构振动还与其固有属性密切相关，振动主要以低阶模态为主。项目通过高速风洞实验积累了大量数据，为我国空腔类布局的飞行器部件气动/结构/噪声多目标优化设计提供了理论指导和数据依据。