Research and technology 1994
Selected research and technology activities at Ames Research Center are summarized. These activities exemplify the Center's varied and productive research efforts for 1994.
Bousman, William G.↗
Engineering topics
Gallman, John W.
Publications and source records attributed to Gallman, John W..
Structural optimization for joined-wing synthesis
The differences between fully stressed and minimum-weight joined-wing structures are identified, and these differences are quantified in terms of weight, stress, and direct operating cost. A numerical optimization method and a fully stressed design method are used to design joined-wing structures. Both methods determine the sizes of 204 structural members, satisfying 1020 stress constraints and five buckling constraints. Monotonic splines are shown to be a very effective way of linking spanwise distributions of material to a few design variables. Both linear and nonlinear analyses are employed to formulate the buckling constraints. With a constraint on buckling, the fully stressed design is shown to be very similar to the minimum-weight structure. It is suggested that a fully stressed design method based on nonlinear analysis is adequate for an aircraft optimization study.
Gallman, John W.↗
Design synthesis and optimization of joined-wing transports
A computer program for aircraft synthesis using a numerical optimizer was developed to study the application of the joined-wing configuration to transport aircraft. The structural design algorithm included the effects of secondary bending moments to investigate the possibility of tail buckling and to design joined wings resistant to buckling. The structural weight computed using this method was combined with a statistically-based method to obtain realistic estimates of total lifting surface weight and aircraft empty weight. A variety of 'optimum' joined-wing and conventional aircraft designs were compared on the basis of direct operating cost, gross weight, and cruise drag. The most promising joined-wing designs were found to have a joint location at about 70 percent of the wing semispan. The optimum joined-wing transport is shown to save 1.7 percent in direct operating cost and 11 percent in drag for a 2000 nautical mile transport mission.
Gallman, John W.↗
Preliminary design optimization of joined-wing aircraft
The joined wing is an innovative aircraft configuration that has a its tail connected to the wing forming a diamond shape in both top and plan view. This geometric arrangement utilizes the tail for both pitch control and as a structural support for the wing. Several researchers have studied this configuration and predicted significant reductions in trimmed drag or structural weight when compared with a conventional T-tail configuration. Kroo et al. compared the cruise drag of joined wings with conventional designs of the same lifting-surface area and structural weight. This study showed an 11 percent reduction in cruise drag for the lifting system of a joined wing. Although this reduction in cruise drag is significant, a complete design study is needed before any economic savings can be claimed for a joined-wing transport. Mission constraints, such as runway length, could increase the wing area and eliminate potential drag savings. Since other design codes do not accurately represent the interaction between structures and aerodynamics for joined wings, we developed a new design code for this study. The aerodynamic and structural analyses in this study are significantly more sophisticated than those used in most conventional design codes. This sophistication was needed to predict the aerodynamic interference between the wing and tail and the stresses in the truss-like structure. This paper describes these analysis methods, discusses some problems encountered when applying the numerical optimizer NPSOL, and compares optimum joined wings with conventional aircraft on the basis of cruise drag, lifting surface weight, and direct operating cost (DOC).
Gallman, John W.↗
Computational transonic flutter boundary tracking procedure
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Gallman, John W.↗