ON EFFECTS OF INCREASING AMPLITUDE IN A BOUNDARY-LAYER SPOT

The boundary-layer spots involved here come from large-time theory and related computations on the Euler equations to cover the majority of the global properties of the spot disturbances, which are nonlinear, t hree-dimensional, and transitional rather than turbulent. The amplitud e levels investigated are higher than those examined in detail previou sly and produce a new near-wall momentum contribution in the mean flow , initially close to the wing-tips of the spot. This enables the ampli tude levels in the analysis to be raised successively, a process which gradually causes the wing-tip region to spread inwards. The process i s accompanied by subtle increases in the induced phase variations. Amo ng other things the work finds the details of how nonlinear effects gr ow from the wing-tips to eventually alter the entire trailing edge, an d then the centre of the spot, in a strongly nonlinear fashion. Compar isons with earlier suggestions and with experiments are described at t he end.