SOLITARY-LIKE WAVES IN BOUNDARY-LAYER FLOWS AND THEIR RANDOMIZATION

Essentially nonlinear motions generated in incompressible boundary lay ers by external agencies are considered. A pertinent mathematical mode l for the Blasius flow is furnished by the forced Benjamin-Davis-Acriv os integral-differential equation. A steady hump is chosen as a simple st source in order to trace the disturbance-pattern evolution as the r oughness height increases, provided that its length is kept fixed. Occ urence of bifurcation phenomena features this problem; the first publi cation gives rise, In particular, to a specific regime with nearly lim it-cycle-type oscillations in the immediate vicinity of the hump. Afte r the second bifurcation studied, the nearly periodic regime collapses into irregular pulsations with erratic sequences of amplitudes and ch aracteristic times. A brief discussion based on the forced Korteweg-de Vries equation lends credence to the view that the chaotically transi tional process can be triggered at an earlier stage of wave amplificat ion.