Numerical Investigation of Flow-Induced Noise Generation at the Nozzle End of Jet Engines.

Sound generation downstream the nozzle end of a subsonic laminar jet has been investigated using two-dimensional direct numerical simulations (DNS). The nozzle end is modeled by a finite flat plate with Mach numbers of MaI = 0.8 above and MaII = 0.2 below the splitter plate. Behind the nozzle end, a combination of a wake and mixing layer develops. Due to the high amplification rates, disturbances saturate before a pure mixing layer occurs. Non-linear generation mechanisms produce higher harmonic disturbances in the upper boundary layer, resulting in an only quasi periodic solution. The main acoustic sources correspond to the positions of vortex pairing. Broadband noise is emitted instead of tonal noise, known from the pure mixing layer without a splitter plate [4]. [ABSTRACT FROM AUTHOR]