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激波位置对黏弹壁板热气动弹性稳定性的影响分析

EFFECTS OF SHOCK LOCATION ON AEROTHERMOELASTIC STABILITY OF VISCOELASTIC PANEL

  • 摘要: 新型复合材料被广泛应用于超声速飞行器壁板结构设计中, 这些材料一般都是具有黏弹性质的材料. 针对任意激波冲击位置下黏弹壁板的热气动弹性稳定性问题, 建立了基于当地活塞流理论的分析模型, 并用数值仿真方法来验证其正确性. 根据Kelvin-Voigt黏弹阻尼模型和von Kármán大变形理论, 建立黏弹壁板的热气动弹性方程, 其中激波前后区域的气动力模型采用当地一阶活塞流理论, 并且假设黏弹壁板受热后温度均匀分布. 采用李雅普诺夫间接法来判断非线性颤振系统的稳定性, 并利用Routh-Hurwitz判据推导出系统发生气动弹性失稳的边界条件, 分别研究了弱激波和强激波冲击下的激波位置对黏弹壁板热气动弹性稳定性的影响. 采用龙格−库塔法对非线性颤振方程直接数值积分求解, 得到黏弹壁板非线性颤振响应的时间历程, 与半解析分析结果进行对比. 研究结果表明, 激波冲击位置可显著改变黏弹壁板的热气动弹性稳定性边界. 当固定的激波位置沿着顺流方向从二维黏弹壁板的一端向另一端变化时, 壁板的临界颤振动压呈现出非线性且非单调的依赖关系. 具体表现为: 在上游区间单调递减, 在中间区间大幅单调递增, 在下游区间则呈现波动状态, 且该波动幅度随激波强度的增加而增大. 最危险的激波固定位置大约在 x_i/l = 0.17 位置处, 且该位置会随着黏弹结构阻尼和激波强度的增加而向上游方向偏移.

     

    Abstract: In recent years, new composite materials have been widely used in the structural design of supersonic vehicle panels, and these new materials generally have viscoelastic properties. Focusing on the aeroelastic stability of a heated viscoelastic panel in shock-dominated flows with an arbitrary shock impingement location condition, a systematic theoretical analysis model is established. According to the Kelvin-Voigt type viscoelastic damping model and von Kármán large deflection theory, the aerothermoelastic equations are established with thermal effect based on quasi-steady thermal stress theory. Local first-order piston theory is employed in the region before and after shock waves. The Lyapunov indirect method is employed to analyze the stability of the nonlinear aeroelastic system, and then aeroelastic stability boundaries can be obtained by using Routh-Hurwitz criterion. Based on the theoretical analysis model, the effects of shock location on the aerothermoelastic stability of the viscoelastic panel are studied. To verify the correctness of theoretical results, nonlinear flutter equations are solved by the fourth-order Runge-Kutta numerical integration method to obtain the time history of panel response. The results show that the shock impingement location has a significant effect on the aerothermoelastic stability of the viscoelastic panel. As the shock wave impact point moves from one endpoint of the panel to another endpoint, the critical flutter dynamic pressure of the viscoelastic panel exhibits nonlinear and nonmonotonic variations. With the moving of the shock wave in the direction of flow, the critical flutter dynamic pressure of the viscoelastic panel exhibits different variations when the oblique shock wave impacts at different locations on the panel. Specifically, near the endpoint of the panel in the upstream region, the critical flutter dynamic pressure continuously decreases; in the mid-area of the panel, the critical flutter dynamic pressure increases monotonically and significantly; near the endpoint of the panel in the downstream region, the critical flutter dynamic pressure fluctuates, and the fluctuation increases with the increase of shock wave strength. The most dangerous position for an oblique shock wave impinging on the viscoelastic panel is approximately at the location x_i/l = 0.17 , which will move upstream of the panel as the viscoelastic damping and the strength of the shock wave increase.

     

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