A parametric experimental study of jet-flap interaction noise for a realistic small-scale swept wing model

Abstract

An experimental study of jet-flap interaction (JFI) noise has been carried out for a realistic small-scale model of the swept wing with an installed dual-stream nozzle. The effect of flap deflection angle on JFI noise has been a major objective of the investigation. It has been found that the flap deflection angle exerts a significant effect on JFI noise in the midfrequency range, so that JFI noise is basically a linear function (in dB) of the flap angle, while for high frequencies JFI noise seems to be independent of flap deflection angle. This linear dependence of noise on flap angle is in agreement with theoretical predictions. The effects of other parameters, such as the velocities of core flow, bypass flow, and coflow have also been studied. It has been shown that core flow velocity does not noticeably influence JFI noise, whereas bypass flow and coflow velocities have a strong effect on noise in the highfrequency and low-frequency ranges, respectively.

Noise Amplification Effects due to Jet-Surface Interaction

“…The noise levels for the isolated jet are given by the black solid curve, and they are seen to agree well with the U 8 j law for turbulent mixing noise in the sideline direction [31]. The overall installed jet, given by the red curve, approximates more the U 6 j curve, whereas the integration of the surface pressure fluctuations (blue curve) has a trend closer to U 5 j , which is consistent with the predictions of Ffowcs-Williams and Hall for trailing-edge scattering [7]. The behavior of the overall installed jet is likely related to the increased significance of the quadrupole terms for higher velocities, changing the overall slope of the curve.…”

“…This results in an interaction between the jet and a nearby airframe surface, generating an additional source known as jet-installation noise (JIN) [2]. The JIN is especially significant during take-off and approach flight conditions, when the deployed high-lift systems are positioned close to the jet plume [3], with significant noise increase at low and mid-frequencies [4,5]. Therefore, the characteristics of the phenomena behind engine installation effects, such as the relationship between the near-field properties of the jet and the far-field noise, must be fully understood so that appropriate noise reduction solutions can be developed, and posteriorly applied on aircraft.…”

On Investigating the Hydrodynamic Field for Jets with and without Installation Effects

“…Several noise reduction technologies have been developed to mitigate the jet installation noise effects [1][2][3][4][5][6][7][8][9][10][11][12]. From these investigations, it is known that the installation affects jet noise by both modifying the jet turbulence and leading to hydrodynamic wave scattering by the trailing edge of the wing flap.…”

Jet-installation noise and near-field characteristics of jet–surface interaction

“…The progressive increase of bypass ratio results in a closer coupling between engine and lifting surfaces; as engines become larger, their distance from the wing needs to be reduced in order to ensure minimum ground clearance. Thus, the interaction between the hydrodynamic near field of the jet and the nearby lifting surface results in an additional noise source at the trailing edge of the latter, thus causing noise amplification at low and mid-frequencies (jet-installation effects) (Mengle et al 2006;Belyaev et al 2015). Jet-installation noise (JIN) is stronger during take-off and approach since high-lift devices are typically deployed and positioned closer to the jet plume (Brown & Ahuja 1984).…”