# NASA Technical Reports Server (NTRS) 19790011864: Application of direct-inverse techniques to airfoil analysis and design

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The direct-inverse technique was developed into a numerical method, called TRANDES, that is suitable for the analysis and design of subsonic and transonic airfoils and for the evaluation of design concepts. A general description of the method is given and its application to a design analysis type of problem is demonstrated. A usage of the method fo

Autor: NASA Technical Reports Server (NTRS)

Fuente: https://archive.org/

## Introducción

_ N79-20035 5 APPLICATION OF DIP_CT-INVERSE TO AIRFOIL TECHNIQUES ANALYSIS AND DESIGN* Leland A.
Carlson Bruce M.
Rocholl** Texas A&M University SUMMARY During the past few years, the dlrect-inverse technique has been developed into a numerical method, called TRANDES, that is suitable for the analysis and design of subsonic and transonic airfoils and for the evaluation of design concepts. This paper provides a general description of the method, demonstrates its application to a deslgn-analysis type of problem, and finally, discusses a new usage of the method for the low speed high lift case. INTRODUCTION The basic concept of the present method (refs.
1-4) is to have a technique which can be used in either the direct (analysis) mode in which the airfoil shape is prescribed and the flowfield and surface pressures are determined, or in the direct-inverse (design) mode in which an initial nose shape is given along with the pressure distribution on the remainder of the airfoil. In the latter case, the flowfield and actual airfoil shape are computed. The resultant computer program, called TRANDES, (ref.
5), has several unique features. In order to achieve accuracy, the method utilizes the full inviscid potential flow equation; and in order to remain simple, it solves the problem in a stretched Cartesian grid system that maps the infinite physical plane to a rectangular computational box.
Further, to avoid at supersonic points difficulties associated with nonaligument of the coordinates and the flowfield, a rotated finite difference scheme is used in the solution; and the resulting transformed finite difference equations are solved iteratlvely by column relaxation sweeping from upstream to downstream. Finally, the method does include the effects of weak viscous interaction. The basic idea in the design case is to treat the airfoil determined by the inverse method as the displacement surface and to subtract from it a displacement thickness determined by a Nash-Mac...