Hydrodynamics and Sound Generation of Low Speed Planar Jet

Abstract

Hydrodynamics and sound radiation of a low speed planar jet with Re=3000 have been studied by large eddy simulation combined with Lighthill’s acoustic analogy. Jets evolving from both well-developed (parabolic) and undeveloped (top-hat) mean velocity profiles have been simulated. The results showed the following: (i) initial domination of a symmetrical mode for jets evolving from top-hat profiles and prevailing of an antisymmetrical mode resulting in a sinuous distortion of the potential core for jets evolving from parabolic profiles, and (ii) shape of a mean velocity profile has some effect on mean flow characteristics; however, the major differences were observed in the development of the fluctuations. Velocity fluctuations were significantly higher for jets evolving from a parabolic profile in the region beyond the end of the potential core before the flow reached a self-preserving state. To calculate the basic sound radiation, the sources in Lighthill’s equation were treated either as compact in all directions or as noncompact in the spanwise direction. The spanwise length of the computational domain was found to have a little effect on the results obtained with compact in all directions solution provided that spanwise length exceeds the correlation length. Results showed that the majority of sound was generated by the region beyond the end of the potential core.