Abstract: Flexible wall vibration is coupled with unsteady transonic flow in a ramjet engine intake with large local wall flexibility at its diffuser，and affects total engine performance. The aero-elastic problem between transonic flow and local wall vibration in a diffuser was studied based on a fluid structure interaction method. Impact of flexible wall damping on diffuser fluid-structure vibration was analyzed. It is shown that fluid-structure vibration of the diffuser induced by self-sustained normal shock oscillation can be limited or suppressed through modifying flexible wall damping. Nondimensional vibration amplitude is 0.37 at the center of the flexible wall without structural damping. It is reduced to 0.22 for model with a stiffness proportional damping coefficient of 1×10-5. Flexible wall vibration vanishes with an increased damping coefficient of 4×10-5，and the transonic diffuser stays at a static balance status.

Key words: Diffuser；Transonic flow；Flexible wall；Fluid-structure vibration

摘要： 冲压发动机进气道扩压段局部结构弹性较大时，壁板振动与跨声速非定常流动相互耦合，影响进气道整体性能。基于流固耦合方法，研究了扩压器内跨声速流动与局部弹性壁板的耦合作用，分析了结构阻尼对扩压器流固耦合振动特性的影响规律。结果表明，通过调整弹性壁板阻尼可以削弱和抑制正激波自激振荡引起的扩压器壁板流固耦合振动。无阻尼弹性壁板中点无量纲振动幅值为0.37。给定刚度等效阻尼系数1×10-5时振幅下降至0.22；增加阻尼系数至4×10-5时，扩压器壁板流固耦合振动消失，进入静平衡状态。

关键词: 扩压器；跨声速流动；弹性壁板；流固耦合振动