Lingwood, R.J. (1997) On the application of the Briggs' and steepest-descent methods to a boundary-layer flow. Studies in Applied Mathematics, 98 (3). pp. 213-254. ISSN 1467-9590
Full text not available from this repository.Abstract
The evolution of wave packets generated by impulsive disturbances of the rotating-disk boundary-layer flow is studied. It is shown, by comparison with Briggs' method, that there are certain difficulties associated with the steepest-descent time-asymptotic method of evaluating the impulse response. The rotating-disk boundary layer provides examples of saddle points through which the steepest-descent path can and cannot be made to pass. It is shown that it is critically important to establish, from the topography of the phase function, whether the steepest-descent path passes through particular saddle points. If this procedure is not carried out, calculations of the wave-packet evolution can be majorly flawed and incorrect conclusions can be drawn about the stability of the flow, i.e., whether it is convectively or absolutely unstable.