Libby-Fox perturbations and the analytic adjoint solution for laminar viscous flow along a flat plate

The properties of the solution to the adjoint two-dimensional boundary layer equations on a flat plate are investigated from the viewpoint of Libby-Fox theory that describes the algebraic perturbations to the Blasius boundary layer. The adjoint solution is obtained from the Green’s function of the perturbation equation as a sum over the infinite perturbation modes of the Blasius solution. The analysis of the solution allows us to obtain constraints on the eigenvalues and eigenfunctions. The extension of the analysis to the case with non-zero pressure gradient, corresponding to the Falkner-Skan solution, is also briefly discussed.