Tones from a choked axisymmetric jet. I. Cell structure, eddy velocity and source locations

The cell structure of a choked axisymmetric jet was examined using schlieren photography over the pressure range in which acoustic tones are emitted. Several small discontinuities were noted and one range of abnormal development. Two methods for measurement of eddy velocity are given — one by noting their locations at known instants, the other by analysing the time averaged optical response to the interaction between the oppositely directed eddy and wave trains. It is shown that the tones are emitted from the 4th, 5th, 6th and 7th cell ends.