Biorthogonal eigenfunction system in the triple-deck limit

The solutions of receptivity problems for a periodic-in-time actuator placed on the wall in a two-dimensional boundary layer and for a two-dimensional hump are discussed within the scope of the biorthogonal eigenfunction expansion technique in the limit of high Reynolds number when the triple-deck scaling is imposed. It is shown that the solutions obtained with the help of the biorthogonal eigenfunction system are equivalent to the solutions derived within the scope of the triple-deck theory.