Abstract
This paper presents the acoustic analysis of the hot subsonic and supersonic jets aerodynamic simulations described in Part I. Acoustic predictions are performed using the flow-fields provided by the 3D unsteady Navier-Stokes computations, for both supersonic and subsonic hot jets. Two surface integral formulations are used: the Kirchhoff method and the Ffowcs Williams and Hawkings (FW-H) equation on a porous surface. Integrations are performed on conical control surfaces as much as possible enclosing the jet and its mixing layers. The influence of the formulation and of parameters, such as control surface location and extent, open or closed nature of the control surfaces, on acoustic far field predictions is first investigated. The results show that the chosen control surfaces are far enough from the jets for FW-H and Kirchhoff calculations starting from pressure but not well suited for Kirchhoff calculations starting from density, in the present cases of hot jets. Comparisons with direct CFD results in the near field confirm this analysis and validate FW-H and Kirchhoff (pressure) radiated noise predictions. The results also show that an open control surface at its upstream and downstream ends can be used in practice. Closed control surface benefits appear only for acoustic predictions at low angle from the jet axis. However such surfaces intersect the jet and are not compatible with Kirchhoff calculations. Far field predictions are then compared with experiments for both supersonic and subsonic jets. The sound directivity and the Strouhal number of the maximum level in the spectral density as a function of the angle of observation are rather well predicted. However, the maximum noise level is overestimated. A deeper analysis of these aeroacoustic predictions is in progress. An example of improvement of CFD/acoustic jet computations is presented.
Published Version
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