Acoustic modes of self-excited oscillations in struts

The acoustic modes of self-excited oscillations are investigated numerically for two-dimensional generic struts. In profiles with short chord lengths, hydrodynamic instability is responsible for wake bifurcation and for generation of narrow band tones. However, it is found, another mechanism is the major factor for periodic oscillations in long profiles. Two points of wall contour develops an acoustic feedback between each other. These points are the inflection point and the trailing edge point. Consequently, limits of two different modes of periodic oscillations are outlined.Moreover, it is determined that acoustic radiation has dipole character which agrees well with the theory of sound radiation for acoustically compact surfaces.