ON THE RELEVANCE OF NONLINEAR INTERACTIONS TO SOUNDRADIATION FROM SUBSONIC JETS

摘要

Direct numerical simulations of the Navier-Stokes equations are carried out to investigatethe role of non-linear interactions between instability waves in sound radiation from a sub-sonic jet. A model problem of a temporally developing jet was solved with the main goal tofind out whether the 'difference' wave number mode resulting from the interaction betweentwo primary instability waves dominates the acoustic field. The current problem formula-tion makes it possible to isolate the sound generated by instability waves from other soundsources such as turbulence. The results obtained demonstrate that interaction between twoinstability waves with wave numbers α1 and α2 and azimuthal wave numbers n1 and n2 leadsto the generation of the mode with wave number α2 ? α1 and azimuthal wave number n2 ? n1that efficiently radiates sound into a far-field. This supports previous results obtained fromLST (linear stability theory) and PSE (parabolized stability equations) and paves the wayfor the more costly simulations of spatially developing jets.