On the use of notched collars on an axisymmetric jet

This paper reports an experimental study conducted on the use of circular, V- and A-notched collars with the expansion-ratio of 3 for a Re = 20,000 axisymmetric jet by using hot-wire anemometry. Results show that limited specific differences in the centerline velocity decay and turbulent intensity levels arise from the use of notched collars. The overall flow field of the collared-jets and their self-excitation mechanisms are also not significantly influenced by modifications to the axial distance distribution of the collars, at least for the notch configurations used in the present study. Observations gathered in the present study suggest that altering the collar cross-sectional geometry, length and expansion-ratio remains to be more effective control techniques for collared-jets.