【摘要】 空腔自激振荡现象广泛存在于航空航天领域,剧烈的压力振荡会造成空腔内部零部件的结构疲劳和破坏,因此研究空腔噪声的控制方法具有重大意义。提出一种可变形状空腔,在空腔内部安装一种曲柄滑块机构从而调整底面和后壁面的倾斜角度。通过直接数值模拟法对马赫数为0.5、低雷诺数下的可变形状空腔流动进行数值仿真。结果表明随着后壁面倾斜角度的增大,监测点处的模态声压级、总声压级均逐渐减小,表明空腔内部流场流动更加平稳,压力振荡明显减弱。此外,通过动态模态分解(DMD)方法对不同后壁面倾斜角度的可变形状空腔进行动态模态分析。研究发现所有的DMD模态均为收敛模态,且随着后壁面倾斜角度的增大,流动越趋于稳定极限环状态;主模态频率所对应的DMD模态结构不同,主要表现为正、负向大尺度结构的位置不同且随着倾斜角度的增大,结构尺度逐渐减小。更多还原

【Abstract】 Cavity self-excited oscillation exists widely in aerospace field, andsevere pressure oscillations cause structural fatigue and damage of components inside a cavity, so it is of great significance to study the control method of cavity noise.Here,a morphing cavity was proposed, inside it a crank-slider mechanism was installed to adjust inclination angle of its bottom surface and back wall one. The flow in a morphing cavity with Mach 0.5 and low Reynolds number was simulated with the direct numerical simulation.Results showed that with increase in inclination angle of back wall surface, the modal sound pressure level and the total sound pressure level at the monitored point gradually decrease, so the flow field in the cavity is more stable and the pressure oscillation is obviously weakened; the dynamic mode decomposition(DMD) method was used to do the dynamic modal analysis of morphing cavities with different inclination angles of back wall surface, all dynamic modes show to be convergent ones, the flow tends to a stable limit cycle state with increase in inclination angle of back wall surface; dynamic mode structures corresponding to the main modal frequency are different, they show different positions of large-scale structures with positive and negative directions, with increase in inclination angle, structures’ scales gradually decrease.更多还原