Geometric Model for a Parametric Study of the Blended�Wing�Body Airplane �

A parametric model is presented for the blended� wing�body airplane � one concept being proposed for the next generation of large subsonic trans� ports. The model is de�ned in terms of a small set of parameters which facilitates analysis and optimization during the conceptual design process. The model is generated from a preliminary CAD geometry. From this geometry � airfoil cross sections are cut at selected locations and �tted with analytic curves. The airfoils are then used as boundaries for surfaces de�ned as the solution of partial di�erential equations. Both the airfoil curves and the surfaces are generated with free parameters selected to give a good representation of the original geometry. The original surface is compared with the parametric model � and solutions of the Euler equations for compressible �ow are computed for both geometries. The parametric model is a good approximation of the CAD model and the computed solutions are qualitatively similar. An optimal NURBS approxi� mation is constructed and can be used by a CAD model for further re�nement or modi�cation of the original geometry. � This paper is declared a work of the U. S. Government and is not subjected to copyright protection in the United States