(Georgia Institute of Technology, 1995-01)
Stettner, Martin; Mavris, Dimitri N.; Schrage, Daniel P.
Progress in establishing an analysis package and design/optimization framework for preliminary design of a civil tiltrotor aircraft is reported. Updates to the sizing/performance program VASCOMP and Equivalent LAminated Plate Solution ELAPS are described. Correlation of this updated ELAPS (now including shear panels) and a state-space unsteady aerodynamic analysis, PWAKE, with reference results from the Automated STRuctural Optimization System, ASTROS, is shown. A generic UNIX-based, flexible executive system for multidisciplinary design/ optimization tasks is presented. The framework features a central data base, provisions for parallel analysis execution on different host computers connected to the same file server, local sensitivity calculation using finite differencing, global sensitivity calculation using the Global Sensitivity Equation (GSE), and a utility allowing different levels of user control. A simple sample case demonstrates proper framework operation and practical advantages in accuracy in the GSE approach versus global finite differencing.
(Georgia Institute of Technology, 1994-02)
Stettner, Martin; Schrage, Daniel P.; Peters, D. A. (David A.)
The Peters/He Finite State Wake Model is described in its application to fixed wing aerolasticity. Expressions for coupling this model with a wing, aerodynamically represented by a flat plate with a trailing edge flap, are developed, and fidelity issues are discussed. An application is presented where the wing/wake system is coupled to a proprotor model. The effects of unsteady wing aerodynamics on damping of this system are investigated. It is found that wake effects are small as a result of generally low damping levels in the system due to wing aerodynamic damping.
(Georgia Institute of Technology, 1993-04)
Stettner, Martin; Schrage, Daniel P.
An automated procedure for tiltrotor performance sensitivity calculation based on a V/STOL aircraft performance and sizing code, VASCOMP, is presented. The technique utilizes internal UNIX utilities and shell scripts, and will provide the option of changing the analysis code. Hence, VASCOMP is a testbed for future application of this approach on different analysis codes in an aeroservoelastic wing optimization process. Sensitivities are analyzed for different configurations deviating in single design variables from a EUROFAR-type baseline. A speed parameter and wing thickness to chord ratio are identified as major design drivers. It is concluded that, if only VASCOMP was to be used for optimization of the productivity index, PI, the resulting configuration would be prone to aeroelastic instability. Thus, inclusion of wing static load and aeroelastic stability constraints using more sophisticated tools is strongly recommended.
(Georgia Institute of Technology, 1992-09)
Stettner, Martin; Schrage, Daniel P.
The paper describes one way to approach the multidisciplinary task of optimizing a tiltrotor wing structure which is equipped with an active flutter suppression system. Objective function is a productivity index, as a measure for aircraft cost-effectiveness. Short digress is held on the characteristics of the tiltrotor's dynamic system and its aeroelastic behavior. Contributing analyses (CA's) for calculating aircraft performance, modeling the dynamic system, and designing an active flutter suppression control system are selected. Multilevel and non-hierarchic decomposition techniques are discussed. A file structure for handling data transfer between the CA's and the optimizer is presented. Preliminary results are shown which highlight some peculiarities of this optimization problem.