Abstract
An axisymmetric numerical simulation approach to the hole-tone feedback problem is presented. It is based on the discrete vortex method and an 'acoustic analogy' representation of flow noise sources. The shear layer of the jet is represented by 'free' discrete vortex rings, and the jet nozzle and end plate by bound vortex rings. This model is capable of predicting the sound-generating unsteady jet flow with good accuracy. In the acoustic model, a monopole source term alone is capable of predicting the correct frequency spectrum, and the correct sound pressure level of the dominating frequency component (the hole tone) in the acoustic near field. The last part of the paper presents several case studies on suppression of the hole tone by forced acoustic excitation of the shear layer near the nozzle exit.
