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 structuredynamics of a controlled jet and the far-field sound. This was achieved by exploring theflowfield and the far field of an axisymmetric Mach 0.9 jet with a Reynolds numberbased on jet diameter of approximately 7.6 x 105. The jet is controlled by eight localizedarc filament plasma actuators (LAFPA), which operate over a frequency range that spansthe jet column instability, the initial shear layer instability, and higher. Varying the phasebetween the eight actuators allows excitation of azimuthal modes (m) 0, 1, 2, and 3.The flowfield is investigated using flow visualization and particle imagevelocimetry (PIV). A Reynolds decomposition of the PIV results showed the importanceof 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 = 1and 3). A proper orthogonal decomposition (POD) of the PIV data was performed toextract information about how forcing affects the large-scale flow features. The firstPOD mode based on v′ shows the existence has large-scale flow features from forcingover a large range of StDF’s (0.09 to 1.08), while the first POD mode based on u′ only haslarge-scale flow features from forcing around the preferred StDF of 0.36.