The stability of a two-dimensional laminar jet

This paper deals with the stability of a two-dimensional laminar jet against the infinitesimal antisymmetric disturbance. The curve of the neutral stability in the (α, R) -plane (α, the wave-number; R, Reynolds number) is calculated using two different methods for the different parts of the curve; the solution is developed in powers of (α R) −1 for obtaining the upper branch of the curve and in powers of α R for the lower branch. The asymptotic behaviour of these branches is that for branch I, 2, \;\; c 23 for R ; and for branch II, R 112^-1|2, \; c 1 20 ² for α → 0. Some discussion is given on the validity of the basic assumption of the stability theory in relation to the numerical result obtained here.