NACA翼型跨声速俯仰流动的直接数值模拟
Direct Numerical Simulation of Transonic Flows Induced Pitching of NACA Airfoil
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中文总结 AI 辅助
通过DNS研究NACA0012翼型跨声速俯仰流动，发现约化速度影响气动载荷与耦合频率，U*=2时流动主导，U*=8时结构主导。
中文摘要 AI 辅助
直接数值模拟（DNS）研究了与单自由度结构动力学耦合的NACA0012翼型上的跨声速流动。针对攻角（{\alpha}）为8°、约化速度（U*）从2到8变化、约化质量（m*）为5.0、雷诺数（Re_\infty）为3×10^6以及马赫数（M_\infty）为0.8的情况进行了分析。空气中的声速计算为a = sqrt({\gamma}RT_\infty)。注意到，随着约化速度的增加，气动载荷和力矩的幅值也随之增大。对固定翼条件下的力矩系数（C_M）进行了快速傅里叶变换（FFT），以提取无量纲主频率，即斯特劳哈尔数（St），以及翼型的耦合振荡频率（Stc）。在{\alpha}=8°的静止情况下，FFT分析得出St=1.3161。高频分量的存在表明与激波-边界层相互作用相关的不稳定性开始出现。对于攻角（AoA）为8°且约化速度U*=2.0和8.0的情况，计算得到的耦合振荡频率（Stc）值分别为0.0762和0.1716。相应的自然气动弹性频率（Stn）取为1/U*，得到值0.5和0.125。观察到，对于U*=2，耦合频率（Stc）与激波抖振频率的次谐波一致，表明动力学以流动为主导。相比之下，对于U*=8，Stc与自然俯仰频率一致，表明结构模态的影响占主导。通过检查压力波动等值线来分析声辐射的特性。分别采用涡量和纹影可视化来识别涡结构的性质、激波的强度及其空间位置。
英文摘要
A Direct Numerical Simulation (DNS) investigates transonic flow over a NACA0012 airfoil coupled with single-DOF structural dynamics. Analysis is performed for angle of attack (α) 8° with varying reduced velocity (U*) from 2 to 8, reduced mass (m*) 5.0, Reynolds number (Re_\infty) of 3 \times 10^6, and Mach number (M_\infty) 0.8. The speed of sound in air is calculated as a = sqrt(γRT_\infty). It is noted that the magnitude of the aerodynamic loads and moments increased with higher reduced velocity. The Fast Fourier Transform (FFT) of the moment coefficient (C_M) in the fixed-airfoil condition is carried out to extract the non-dimensional dominant frequency, referred to as the Strouhal number (St), along with the coupled oscillation frequency of the airfoil (Stc). The FFT analysis for the stationary case at α = 8° yields a value of St = 1.3161. The presence of high-frequency components indicates the onset of instability associated with shock-boundary layer interaction. The computed values of the coupled oscillation frequency (Stc ) are 0.0762 and 0.1716 for the cases with angle of attack (AoA) 8° and reduced velocities U* = 2.0 and 8.0, respectively. The corresponding natural aeroelastic frequencies (Stn) are taken as 1/U*, yielding values of 0.5 and 0.125. It is observed that for U* = 2, the coupled frequency (Stc) aligns with the subharmonic of shock-buffet frequency, indicating flow-dominated dynamics. In contrast, for U* = 8, Stc coincides with the natural pitching frequency, indicating a dominant influence of the structural mode. Pressure fluctuation contours are examined to analyze the characteristics of acoustic radiation. Vorticity and schlieren visualizations are employed to identify the nature of vortex structures, the strength of the shock, and its spatial location, respectively.
发表机构
- Department of Mechanical Engineering, IIT(ISM) Dhanbad（印度理工学院（ISM）达纳巴德机械工程系）
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