Numerical Analysis of Airfoil and Cascade Flows by the Viscous/Inviscid Interactive Technique

Abstract

A viscous-inviscid interaction calculation is performed to study the steady, two-dimensional, incompressible/subsonic compressible, attached and separated flows for isolated airfoils and airfoil cascades. A full-potential code was coupled with a laminar/transition/turbulent finite difference code using the semi-inverse method. For the potential flow, the finite element method is employed and the circulation is considered as an unknown parameter. In order to handle the problem efficiently, an automatic grid generation technique is necessary. For the incompressible flow, the solution can be achieved without iteration. However, for the compressible flow, a “pseudotime integral” is used to find a steady-state solution. To understand the viscous effect, the boundary layer equations are solved by the implicit, finite difference method. For the turbulent flow, the algebraic eddy-viscosity formulation of Cebeci and Smith is used. The location of transition from laminar to turbulent flow is predicted or specified by empirical data correlations. The transitional region is taken into account by an empirical intermittency factor. With regard to separated flows, the FLARE approximation and inverse method are introduced. In order to evaluate the present solution procedure, the numerical results are compared to the theoretical and experimental data given in other papers and reports.