Acoustic Measurements of High-Speed Jets from Rectangular Nozzle with Thrust Vectoring

Abstract

Laboratory experiments were conducted to characterize the noise produced by jets from a rectangular nozzle with thrust-vectoring capability. Such exhaust jets are present on state-of-the-art fighter aircraft designed for supermaneuverability. This scaled nozzle research was facilitated by the design of a model with rectangular exit geometry and thrust-vectoring attachments, thus simulating one configuration of such aircraft. A supersonic, helium―air mixture jet issued from this nozzle, and acoustic measurements were made with four microphones arranged in a circular arc in the far-field region. Schlieren photographs were recorded to establish the major features of the jet flow. Significant among the results was the fact that the addition of thrust-vectoring attachments set to 0 deg deflection, on an otherwise clean rectangular nozzle, decreases the intensity of sound radiated on each axis plane to below that of a round nozzle jet. Furthermore, deflection of the flow in the minor axis plane by virtue of these nozzle attachments induces an approximately corresponding deflection of the acoustic field without significant additional noise components in the peak emission direction. The frequency spectra as well as overall sound pressure levels of microphone measurements with the rectangular nozzle jet at several observation positions and thrust-vectoring configurations are presented and summarized in the results of this paper.