An experimental investigation into model-scale installed jet–pylon–wing noise

Abstract

A model-scale experimental investigation of an installed jet–pylon–wing configuration was conducted at the University of Southampton, with the scope to study the effect a pylon has on noise generation and to clarify its impact on the fluctuating wall-pressure load. The set-up consisted of two single-stream nozzles, a baseline axisymmetric annular nozzle and a partially blocked annular pylon nozzle. The nozzles were tested first isolated and then installed next to a NACA4415 aerofoil ‘wing’ at a single nozzle–wing position. The jet Mach number was varied between $0.5 \leq M_{{j}} \leq 0.8$ and measurements were performed both under static and in-flight ambient flow conditions up to ${M_{{f}} = 0.2}$ . The jet flow-field qualification was carried out using a single-velocity-component hot-wire anemometer probe. The pressure field on the wing surface was investigated using two miniature wall-pressure transducers that were flush-mounted in the streamwise and spanwise directions within the pressure side of the wing. A linear ‘flyover’ microphone array was used to record the noise radiated to the far field. The unsteady pressure data were analysed in both time and frequency domains using multi-variate statistics, highlighting a far-field noise reduction provided by the presence of the pylon only in the installed case. Furthermore, the wake field generated behind the pylon is seen to significantly modify the wall-pressure fluctuations, particularly at streamwise locations close to the pylon trailing edge.

On the Wall Pressure Fluctuations induced by a Supersonic Jet over the Wing pressure side

“…5 (a) and (b), the variation of the NPR slightly influences the OASPL magnitude without having any particular effect on its axial trend. The trends agree with the literature [6,11] showing a quick OASPL increase with the x/D that we ascribe to the starting of jet flow grazing over the wing. We observed different OASPL trends between the two jet-wing radial distances, which we related to both the higher flow development over the surface and the elevated wing intrusiveness at H/D=0.6.…”

“…Also, in this case, the NPR does not influence OASPL trends due to its slight variation. However, different OASPL trends are observed between the two wing radial positions due to a more pronounced jet plume distortion with the wing at H/D=0.6, which enlarges in y-direction the lower jet shear layer [11]. In both cases, the OASPL decay has been observed towards higher y/D due to the less jet wing grazing that reduces the dominating of the hydrodynamic field over the pressure transducers.…”

“…Relevant are the works of [10] and [11] which for the first time carried out an experimental analysis on the wall pressure fluctuations induced by a jet flow on scaled jet wing configurations, including also a wind-tunnel generated flight stream.…”

“…This work is a follow up of the previous illustrated analyses and presents for the first time an experimental study of the jet induced wall pressure fluctuations over a wing generated by NACA4415 profile, chosen according to [11]. The jet exhausting flow has been provided using a convergent-divergent nozzle by varying its pressure ratio between NPR=2.2 up to NPR=2.6.…”

“…Measurements were performed by varying the nozzle pressure ratio from NPR=2.2 up to NPR=2.6 by step of 0.1, allowing us to explore different flow conditions: design, under-expanded, and over-expanded. A 3D printed NACA4415 [11] wing profile, having a 60 mm chord and a 150 mm span, was installed at two different radial locations from the jet centreline, specifically, H/D=0.6 and H/D=0.75, where H is the vertical distance measured from the wing trailing and D is the nozzle exhaust diameter. The wing has been made using polylactic acid (PLA) with the printer of the laboratory G.Guj, fig.…”