School of Engineering and Materials Science Research

Jet Noise

Collaborators: E.J. Avital, C.J. Lawn, R.E. Musafir, J. Cater, A. Ahmad and J. Punekar

Aircraft noise pollution continues to affect the development of aviation. Although good progress has been made in reducing aircraft noise and particularly jet noise, the latter continues to be a significant noise generator. Here we look briefly at several projects that have taken place in Queen Mary:
Low Speed Jets:
Flow simulations using local and national computing facilities were carried out to simulate the development of various circular, elliptic and planar jets, see for example Figure 1. New numerical algorithms have been developed to couple the acoustic analogy approach with the flow solver achieving good accuracy and pointing to the effect of enhanced mixing on low speed jet noise (e.g. Avital et al., Aero J., 2008, Alonso & Avital, Int J. Aeroacoust. 2009)
High Subsonic Jets: Following an earlier computational study of high subsonic jets (e.g. Jiang et al, JSV, AIAA J., 2004) attention has been shifted towards developing and assessing rapid prediction methods based on the acoustic analogy approach and ray acoustics. This effort is mostly carried out in UFRJ Brazil by Prof. Musafir.
High Speed Jets: The Queen Mary acoustic chamber initiated by Dr. Cater (see Figure 2) has been used by Mr. Ahmad to study low supersonic jet in collaboration with Prof. Lawn. Success has been recorded in reducing various high speed jet noise components by a few dBs using enhanced mixing and swirl. These noise components include mixing, screech and shock associated broadband. The emitted high sound level can lead to non-linear propagation, causing crackle-like features. For this purpose a new weakly non-linear sound propagation equation has been developed, avoiding the numerical instability associated with the Westervelt equation (Avital et al, J. Comp Acou, 2012)