Computation of subsonic viscous and transonic viscous-inviscid unsteady flow

A new viscous-inviscid interaction scheme is introduced, which implicitly couples the unsteady Euler and the boundary-layer equations. The adequacy of an integral formulation of the viscous flow equations for use in unsteady flows is shown in comparison with experimental results and finite-difference computations, and an explanation is worked out which traces back the unsteady response of the mean and turbulence field due to the external unsteadiness to a quasi-steady behaviour. The interaction computations of transonic airfoil flows by means of the Euler-boundary-layer technique are compared with the steady and unsteady experimental data sets for the RAE 2822 and the NLR 7301 supercritical airfoils, respectively.