起落架开舱构型自激振荡预测公式改进与分析

Improved formula for prediction of self-sustained oscillation frequencies of bay-opening cabin with landing gear

起落架开舱构型的流动模态产生自激振荡,造成舒适性和安全性问题;深入研究该流动模态和自激振荡机理是解决这一问题的关键。本文采用延迟脱体涡模拟(DDES)对起落架开舱构型的流动特性和气动特性进行了分析。结合Rossiter公式与涡声耦合闭环反馈机制,提出了一种适用于起落架舱的自激振荡频率预测公式的修正方法,能够将舱体前后壁面不等高、前缘弧面整流以及起落架的影响考虑在内;并且通过功率谱主频比对验证了修正公式的有效性。此外,引入动力学模态分解(DMD)方法分析自激振荡机理;分析结果显示,随着模态数增大,壁面压强响应逐步从舱体后缘向前缘发展。

The flow pattern of the bay-opening landing gear configuration produces self-sustained oscillations,causing comfort and safety issues.A deep research on the flow pattern and resonance mechanism is the key to solve the issues.In this paper,Delayed Detached Eddy Simulation(DDES)is used to analyze the flow characteristics and aerodynamic characteristics of the typical bay-opening landing gear configuration.Combining the Rossiter formula and the vortex-acoustic coupling closed-loop feedback mechanism,a method is proposed to modify the formula for self-excited oscillation frequency prediction for the landing gear cabin.The method can take into account the influence of the unequal height of the front and rear walls of the cabin,the arc fairing and the landing gear.The improved formula is verified by power spectrum dominant frequency comparison.Besides,Dynamic Mode Decomposition(DMD)is introduced to analyze the mechanism of self-sustained oscillation.Analysis results show that with the increase of the number of modes,wall pressure fluctuation develops from the trailing edge to the leading edge in the cabin.