Spectral computation of triple-deck flows

The Fourier transform method is applied to the problem of computing viscous flows involving boundary-layer separation, based on the triple-deck model of viscous-inviscid flow interaction. As used here, the method is pseudo-spectral in that the nonlinear inertia terms are evaluated in physical variables, although the main computations are made in spectral variables. The Fast-Fourier-Transform algorithm is used to expedite the iterated transformations. The method is much faster than conventional finite-difference methods; typically only ten or twenty iterations suffice for convergence to four or five digits of accuracy. Furthermore, no artificial stabilization schemes are necessary to treat the reversed flows occurring in separated regions. Results are presented for both incompressible and supersonic flows, and are shown to compare well with previous finite-difference results.