Excitation of acoustic modes in a chamber by vortex shedding

Large solid propellant rocket motors are conveniently assembled with segmented grains. The interfaces of the grains are coated with inert, slow-burning material. As the propellant burns radially during a firing, the inert material is exposed in the form of annular rings oriented normal to the axis of the chamber. The flow through a ring will produce periodic shedding of vortices over a broad range of conditions.