Aerodynamic optimization of subsonic flying wing configurations

AIAA-2002-2931 AERODYNAMIC OPTIMIZATION OF SUBSONIC FLYING WING CONFIGURATIONS
B. Mialon, T. Fol, C. Bonnaud ONERA, Applied Aerodynamics Department, F92320 Châtillon, France Airbus France, 316, Route de Bayonne, 3060, Toulouse Cedex 03, France Seditec, Groupe Aeroconseil, 3, rue Dieudonné Costes, BP75, 31703, Blagnac Cedex, France of this program has been carried out by Airbus France and ONERA,with two main objectives : - to assess the cruise aerodynamics performance of a viable flying wing, in order to prepare future experimental work ; - to get basic knowledge on the sensitivities to geometrical parameters, on the design process and on the existing tool relevance. The focus here is on high speed, clean wing aerodynamics design. The paper presents the initial optimization study carriedout on two configurations, in order to produce a viable design, valuable for wind tunnel testing. The engine installation is not considered in this paper, although in parallel with the clean wing optimization, the problematic of the engine integration on such a novel configuration has been investigated, in order to identify the major technical issues and to find out a range of appropriatesolutions. The first part of the paper is dedicated to the description of the optimization problem specifications while the second part focuses on the tool description. The third and fourth parts present the design process for the configurations at hand.

Abstract1
The paper presents some aerodynamic results of initial design studies carried out at ONERA and Airbus France, on flying wingconfigurations. A description of the analysis and the design process, using CFD tools, is given and some results regarding the effects of the planform are presented.

Introduction
Passenger and cargo air traffic is expected to grow about 5% a year over the next 20 to 30 years. The conventional jetliner configuration, with a cylindrical fuselage, a swept wing and empennage and engines mounted on pylons underthe wings, was developed nearly 50 years ago. Over the years, jetliners have grown considerably to meet market demand, to reach more than 550 passengers in a 3-class layout for the next generation. Designing such a large capacity aircraft brings up new technical challenges and the size limit for the “tube and plank” configuration is probably reached. In addition to the size limit, futureaircrafts will have to meet the demands of increased economic efficiency and reduced environmental impact. As a consequence, novel configurations for subsonic transport have been the subject of a renewal of interest in the last decade1,2,3,4. The flying wing, or blended wing body, seems to be one of the most promising concept regarding very high capacity aircrafts. However, no experience exist with suchunconventional configurations, which makes their design very challenging in a number of disciplines. The classical design methodologies do not apply and the high rate of integration of the shape makes even stronger the interdependency between aerodynamics, aeroelasticity, flight mechanics and structure. A program of fundamental research has been launched on these configurations within Airbus. Oneelement
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Specifications
Two planforms have been proposed by Airbus France (figure 1).

Second planform First planform

y

Pressurized area

Copyright © 2002 by ONERA. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

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Figure 1: Top view of the configurations studied

1 American Institute of Aeronautics and Astronautics

The firstconfiguration is composed of an inner body generated by rather thick airfoils (figure 2), appropriate for lodging passenger and/or freight, and of two wings mounted outboard. The maximum thickness is located near the centerline. The leading edge sweep angle is almost constant all along the span, while the trailing edge sweep angle is 0° in the inner and central areas, linked through a region with...