Key points are not available for this paper at this time.
For about a decade it has been noticed from the measurements of many jets that the value of the preferred mode and the spreading rate vary within a range of about 100%. In the present paper it is suggested that extremely low-level spatially coherent disturbances in individual facilities change the initial conditions of a laminar shear layer. The various initial conditions are able to cause different downstream developments of the jet and result in the discrepancies reported in the literature.
Gutmark et al. (Sat,) studied this question.