Forward motion effects on jet noise, panel vibration, and radiation

A model of the interaction of sound from a spreading subsonic jet with a four-panel assembly is studied numerically in two dimensions. The effect of forward motion of the jet is allowed for by considering a uniform flowfield superimposed on a mean jet exit profile. The jet is initially excited by a pulselike source inserted into the flow field. The pulse triggers instabilities associated with the inviscid instability of the jet shear layer. These instabilities generate sound, which in turn serves to excite the panels. The far-field acoustic radiation, the panel response, and the sound radiated from the panels are all computed and compared with computations with a static jet. The results demonstrate that for a jet in forward motion there is a reduction in sound in downstream directions and an increase in sound in upstream directions, in agreement with experiments. Furthermore, the panel response and radiation for a jet in forward motion exhibit a downstream attenuation as compared with the static case.