The use of linearized-aerodynamics and vortex-flow methods in aircraft design /invited paper/

Abstract: The conceptual design parameters and design processes which are used to access the development of the generic stability and control method are identified and discussed in Sect. 4.4. Primarily, design related commonalties and peculiarities for the range of conventional and unconventional aircraft types are considered.

Abstract: The regime of validity of an aerodynamic mathematical model, applicable to describe the nonlinear aerodynamic reactions to a delta wing maneuvering at high angles of attack is investigated. An unsteady vortex-lattice method is used to compute the unsteady flowfields, and thus to evaluate the aerodynamic data required by the model, in terms of specified characteristic motions. Time-histories of the aerodynamic responses to complex motions are generated by means of the model and the evaluated aerodynamic data, and are compared with baseline aerodynamic responses obtained from direct vortex-lattice computations. The validity of the mathematical modeling approach for the maneuvering delta wing is demonstrated by the close agreement of the force and moment responses obtained from the two approaches.

Abstract: CONMIN is a FORTRAN program, in subroutine form, for the solution of linear or nonlinear constrained optimization problems. The basic optimization algorithm is the Method of Feasible Directions. The user must provide a main calling program and an external routine to evaluate the objective and constraint functions and to provide gradient information. If analytic gradients of the objective or constraint functions are not available, this information is calculated by finite difference. While the program is intended primarily for efficient solution of constrained problems, unconstrained function minimization problems may also be solved, and the conjugate direction method of Fletcher and Reeves is used for this purpose. This manual describes the use of CONMIN and defines all necessary parameters. Sufficient information is provided so that the program can be used without special knowledge of optimization techniques. Sample problems are included to help the user become familiar with CONMIN and to make the program operational.

Abstract: Polhamus Langley Research Center SUMMARY A concept for the calculation of the vortex lift of sharp-edge delta wings is pre­sented and compared with experimental data. The concept is based on an analogy between the vortex lift and the leading-edge suction associated with the potential flow about the leading edge. This concept, when combined with potential-flow theory modified to include the nonlinearities associated with the exact boundary condition and the loss of the

Abstract: Two procedures for calculating the lift distribution along the span are given in which a better account is taken of the distribution of circulation over te area than in the Prandtl lifting-line theory. The methods are also applicable to wing sweepback. Calculated results for the two methods were in agreement.

Abstract: : The report presents a complete discussion of a method for calculating potential flow about arbitrary lifting three-dimensional bodies without the approximations inherent in lifting-surface theories. The basic formulation of three-dimensional lifting flow is pursued at some length and some difficulties are pointed out. All aspects of the flow calculation method are discussed, and alternate procedures for various aspects of the calculation are compared and evaluated. Particular emphasis is placed on the handling of the bound vorticity and the application of the Kutta condition, and it is concluded that the approach used in the method of this report has certain advantages over alternate schemes used by other existing methods. A considerable number of calculated results for various configurations are presented to illustrate the power and scope of the method.