Effects of Jet–Flap Interaction on Flow and Acoustic Fields

Jet–flap interaction noise is brought about by the proximity of a turbofan engine to airframe surfaces and arises mainly during take-off and landing. This paper reports a numerical analysis of the flow and acoustic fields generated by an isothermal, subsonic, circular jet close to a simplified geometry of a wing and flap under the intrusive conditions of flap deflection angles of 7 ∘ , 15 ∘ , and 30 ∘ and Mach numbers of 0.5 and 0.7. The jet–flap interaction was seen to deflect the jet stream downwards and increase turbulence intensity levels. Regarding the far-field noise, amplifications with respect to the free-jet noise were verified over the entire frequency range, and noise shielding was predicted at high frequencies. The installation effects at low frequencies were found to be less dominant as the jet velocity was increased. Substantial amplifications were found for a flap angle of 30 ∘ in the high-frequency range, most likely caused by the changes in the jet quadrupole noise due the deformation of the jet flow. The far-field noise was also computed from the pressure field on the wing and flap surfaces, showing that the contributions of both the wing and the flap give rise to a dipole-like directivity pattern perpendicular to the surfaces, at low Strouhal. The noise associated with the flap was found to dominate over that of the wing for almost all polar angles.