Inverse solution existence and uniqueness issues are discussed for supersonic and hypersonic three-dimensional inverse procedures that use space-marching techniques. By using extreme body-slope angle, a simple method to estimate the limiting domain of inverse solution existence is proposed and applied to several example test cases with and without angle of attack. The method provides useful information about possible target pressure distributions and inverse solution existence without performing any inverse calculations. By investigating the relations between the surface pressure and the body geometry, a general explanation for inverse solution uniqueness has been described. Sample calculations to support this explanation are presented
The use of Iteratively Reweighted Least Squares (IRLS) for detecting design points where structural optimizations give poor designs is demonstrated. Since most optimization error is one sided with poor results producing an overweight objective value, a nonsymmetrical version of IRLS (NIRLS) that takes into account the asymmetry in optimization errors is also developed. Optimization studies with various sets of convergence criteria on wing bending material weight of a high speed civil transport are used to demonstrate these techniques. First, inspection of poor designs by a visualization technique that plots objective function and constraint boundaries on planes including the suspected points, indicated that poor results were due to incomplete convergence of the optimization procedure rather than due to local minima. Results obtained with several hundred design points indicated that IRLS techniques can find most of the points with large optimization errors, but that NIRLS techniques are much more reliable in this task. Finally, the paper shows that the choice of convergence settings and parameters can have large effects on optimization errors. In particular, tighter * Graduate Research Assistant, Department of Aerospace and Ocean Engineering, Student Member AIAA. † Graduate Research Assistant, Department of Aerospace Engineering, Mechanics and Engineering Science, University of Florida, Gainesville, FL, Student Member AIAA. ‡ Professor, Department of Aerospace and Ocean Engineering, Associate Fellow AIAA. § Distinguished Professor, Department of Aerospace Engineering, Mechanics and Engineering Science, University of Florida, Gainesville, FL, Fellow AIAA. ¶ Professor, Departments of Computer Science and Mathematics. ** Professor and Department Head, Department of Aerospace and Ocean Engineering, Associate Fellow AIAA. Copyright 2000 by Hongman Kim. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. criteria for some parameters may actually increase optimization error.
Nineteen white-tailed deer (Odocoileus virginianus) from 5 counties in Alabama were examined for infection with Toxoplasma gondii. Twenty-gram samples of heart tissue were bioassayed in mice, serum was examined for T. gondii antibodies using the direct agglutination test, and sections of heart muscle were examined histologically for tissue cysts. Toxoplasma gondii was isolated from 4 of 19 (21%) white-tailed deer hearts. Antibody titers of greater than or equal to 1:50 were found in sera from 7 of 16 (44%) white-tailed deer. Histological examinations of tissue sections from white-tailed deer hearts were negative for T. gondii.
Multidisciplinary Design Optimization (MDO) has been used to investigate the use of anew concept for a transonic transport, the strut-braced wing. The incorporation of a strutinto more traditional transonic transport concepts required the application of computationaldesign techniques that had been developed at Virginia Tech over the previous decade.Formalized MDO methods were required to reveal the benefits of the tightly coupledinteraction between the wing structural weight and the aerodynamic performance. Toperform this study, a suite of approximate analysis tools was assembled into a complete,conceptual-level MDO code. A typical mission of the Boeing 777-200IGW was chosen as thedesign mission profile. Several single-strut configurations were optimized for minimumtakeoff gross weight, with the best single-strut configuration showing a nearly20% reductionin takeoff gross weight, a 29% reduction in fuel weight, a 28% increase in the lift-to-dragratio, and a 41% increase in seat-miles per gallon relative to a comparable cantileverconfiguration. The use of aeroelastic tailoring in the design illustrated ways to obtain furtherbenefits. The paper synthesizes the results of the five-year effort, and concludes with adiscussion of the effects various constraints have on the design, and lessons learned oncomputational design during the project.
Accurate drag estimation is critical in making computational design studies. Drag may be estimated thousands of times during a multidisciplinary design optimization, and computational fluid dynamics is not yet possible in these studies. The current model has been developed as part of an air-vehicle conceptual-design multidisciplinary design optimization framework. Its use for subsonic and transonic aircraft configurations is presented and validated. We present our parametric geometry definition, followed by the drag model description. The drag model includes induced, friction, wave, and interference drag. The model is compared with subsonic and transonic isolated wings, and a wing/body configuration used previously in drag prediction workshops. The agreement between the predictions of the drag model and test data is good, but lessens at high lift coefficients and high transonic Mach numbers. In some cases the accuracy of this drag estimation method exceeds much more elaborate analyses.
This paper describes the multidisciplinary design optimization (MDO) of a transonic strutbraced wing aircraft. The optimization considers aeroelastic deformations of the wing and passive load alleviation. The calculations reveal that the strut twist moment provides substantial load alleviation and significant reductions in structural wing weight. To benefit from the potential of appl ying passive load alleviation during preliminary aircraft design, a flexible wing sizing module has been linked to the MDO design tool to optimize the design of three different strut-braced wing aircraft configurations featuring fuselage mounted engines, underwing mounted engines, and wingtip mounted engines.
This computational aerodynamics textbook is written at the undergraduate level, based on years of teaching focused on developing the engineering skills required to become an intelligent user of aerodynamic codes. This is done by taking advantage of CA codes that are now available and doing projects to learn the basic numerical and aerodynamic concepts required. This book includes a number of unique features to make studying computational aerodynamics more enjoyable. These include:The computer programs used in the book's projects are all open source and accessible to students and practicing engineers alike on the book's website, www.cambridge.org/aerodynamics. The site includes access to images, movies, programs, and moreThe computational aerodynamics concepts are given relevance by CA Concept Boxes integrated into the chapters to provide realistic asides to the conceptsReaders can see fluids in motion with the Flow Visualization Boxes carefully integrated into the text.
