In this paper for the case of Falkner-Skan flow, we investigate indentation
s which call provoke boundary layer separation, without deeply modifying th
e base flow. Using the asymptotic method of matched expansions, we show tha
t these perturbations lead to double or triple deck structures depending on
the size of the indentation. (C) 2001 Academie des sciences/Editions scien
tifiques et medicales Elsevier SAS.