高雷诺数高速喷射中的远场辐射噪声机理

The present research examines the relationship between the large-scale structure dynamics of a controlled jet and the far-field sound. This was achieved by exploring the flowfield and the far field of an axisymmetric Mach 0.9 jet with a Reynolds number based on jet diameter of approximately 7.6 x 105. The jet is controlled by eight localized arc filament plasma actuators (LAFPA), which operate over a frequency range that spans the jet column instability, the initial shear layer instability, and higher. Varying the phase between the eight actuators allows excitation of azimuthal modes (m) 0, 1, 2, and 3. The flowfield is investigated using flow visualization and particle image velocimetry (PIV). A Reynolds decomposition of the PIV results showed the importance of the streamwise velocity fluctuations for the symmetric azimuthal modes (m = 0 and 2), and the cross-stream velocity fluctuations for the asymmetric azimuthal modes (m = 1 and 3). A proper orthogonal decomposition (POD) of the PIV data was performed to extract information about how forcing affects the large-scale flow features. The first POD mode based on v shows the existence has large-scale flow features from forcing over a large range of StDFs (0.09 to 1.08), while the first POD mode based on u only has large-scale flow features from forcing around the preferred StDF of 0.36. 德国LaVision PIV/PLIF粒子成像测速场仪 HighSpeedStar PIV相机 用于粒子成像测速(PIV)的荧光示踪粒子