Abstract:
With the help of the «Vortex&Wave Tracker» program, joint computation of the impeller of a turbojet engine fan with several variations of input devices were carried out. The computation used different approaches to turbulence description from RANS to zonal IDDES. To identify the features of the generation and transformation of acoustic disturbances a comparison of the computation results with a cylindrical channel and model input disturbances in the URANS and LES representations was used. The comparison confirmed a qualitative change in the transformation of acoustic disturbances with the vortex-resolving approach to turbulence description. Vortex-resolving calculations of the supersonic air intake system with a make-up window at takeoff — the fan impeller showed that in all considered variants, the flow inhomogeneity in front of the impeller is unacceptably high. The noise of the system differs from the noise of the impeller in a short nacelle in structure, pattern and level. It is a combination of the noise of the fan, which has lost its tonal structure when interacting with turbulence in the channel, and the noise of poorly streamlined air intake walls. The calculation showed that when the grating was added to the window, it became a source of its own tonal noise, capable of increasing the total level in the far field to 5dB.
Keywords:aeroacoustics, interaction of acoustic disturbances with turbulence, supersonic air intake, vortex-resolving calculation, computation of the impeller in a nonuniform flow, transformation of acoustic disturbances.
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