Study of the effect of flap angle on the dual-stream hot jet-flap noise

The experimental investigation of jet-flap-interaction (JFI) noise on dual-stream hot jets due to flap angles is conducted in the full anechoic chamber of Fluid and Acoustic Engineering Laboratory in Beihang University. A detailed analysis of the experimental data of jet-flap noise and a semi-empirical prediction method is given. The experimental measurements demonstrate that the flap angle has a great effect on the generation of the tonal noise and the broadband noise component is insensitive to the flap angle. The noise reflection by the flap surfaces at high frequency isn't observed due to the strong refraction effect in dual-stream hot jet. The non-harmonic jet impingement tonal noises are analysed and found the tonal frequency are in agreement with feedback prediction formula. The jet-flap noise is modelled by a two-source model. The first source is jet alone noise and predicted by improved Stone model, comparison of predicted spectra with experimental data shows the high accuracy of the improved Stone model. The second source is caused by the flap trailing edge scattering mechanism. A semi-empirical model for the flap trailing edge scattering mechanism is given.