Design and Testing of a Blended Wing Body Aeroelastic Wind-Tunnel Model

Abstract

Introduction E LASTIC wind tunnel models are frequently used to validate performanceand aeroelasticbehaviorof full size aircraft structures, for example, see Sensburg et al.,1 Schneider et al.2 and Baker et al. The model usually represents a full-size structure in an aeroelastically scaled sense. Techniques based on numerical optimization are sometimes used to achieve representativemodel behavior. For example, French and Eastep4 present an approach for matching both static and dynamic aeroelasticproperties.Once manufactured, the stiffness properties of the model are usually Ž xed, but the mass distributionmay be modiŽ ed by addingmasses at various locations. Modular elastic models, for which the stiffness andmass properties can be changed,are also being developedand are used for multipurpose investigations, for example, see Amiryants and Ishmuratov.5 Both the manufacturingand the experimental testing of aeroelastic wind-tunnel models can be very complicated due to the complexity of the models and the equipment required for aeroelastic measurements.This study focuseson an experimentalapproach that allows for short design and testing cycles using limited resources. Hence, experimental data for validation purposes can be delivered at a very early phase of a new project. The aim is to use a relatively simplemodular aeroelasticmodel in combinationwithmore sophisticated,yet easy to use, experimentalequipmentfor data acquisition. For validationof aeroelasticanalysis, access to experimentaldata in terms of both aerodynamic loads and aeroelastic deformations is normally required. Whereas load measurements are routinely performed using various types of wind-tunnel balances, the concern of deformationmeasurements is usually more involved. In the present study,an opticaltechniquebasedonmultiple-cameraphotogrammetry is used in combinationwith passive re ecting markers attached to the model. One signiŽ cant advantage with passive-type markers is that no cabling inside the model is required, hence, further simplifying the model manufacturing and testing. Experiments usingmultiple-cameraphotogrammetryandpassivemarkershavealso been conducted at NASA, as reported by Burner and Liu. The particular wind tunnel model considered in this paper is designed for low-speed aeroelastic investigations of a Blended Wing Body (BWB) transport aircraft. The BWB type of nonconventional subsonic transport concept has been the objective for several studies concerning potential beneŽ ts compared to more conventional aircraft. An overview of the BWB concept and promising results are presented by Roman et al. and Liebeck et al. One important issue with the study of the BWB concept is that tools for analysis of conventional aircraft have been developed for decades, although the developmentof the BWB provides new challenges.This implies that veriŽ cation of numerical results, by using, for example, wind-tunnelmodels, becomes very important.