Alexandre P. Antunes

Studies in Aerodynamic Optimization Based on Genetic Algorithms

The present paper discusses some aspects associated with the use of genetic algorithms for performing aerodynamic optimization studies. The contributions of the work lie in the assessment of important building blocks of aerodynamic global optimization processes. These building blocks are those concerned with issues that have a considerable effect on the performance of the optimization process and on the characteristics of the obtained solution. The investigated contents encompass the effects of the geometrical parameterization, the influence of the adopted number of individuals on the optimization process, and the effects of the boundary-layer transition location on the final optimized shape. Both two- and three-dimensional aerodynamic optimization studies are performed to address the issues under consideration here.

Application of Active Camber Morphing Concept to a Regional Aircraft

The present work addresses the aerodynamic design of a Reference Aircraft (RA) and the assessment of the potential benefits that an active camber morphing can bring in terms of aircraft performances. The subject of the work is part of the FP7-NOVEMOR project (Novel Air Vehicle Configurations: From Fluttering Wings to Morphing Flight) which is one of the many projects from the European Framework Programme. The Reference Aircraft is representative of a typical regional jet capable to carry 113 PAX in a single economic class and provide operational flexibility to fly different missions at the transonic regime. The implementation of active camber concept is based on the use of classical control surfaces as well on conformable morphing control surfaces. Aiming at the optimal design of such as morphing devices, a dedicated procedure called PHORMA is introduced, for the definition of the optimal shape taking into account both aerodynamic and structural constraints. This papers briefly summarizes the tools developed and the first results obtained in terms of potential benefits such as fuel saving.

A Framework for Aerodynamic Optimization Based On Genetic Algorithms

work for 2-D and 3-D aerodynamic optimizations. The creation of the framework is an attempt to generate a design environment capable of coupling various tools from dierent levels of complexity and with diverse functionalities. The conceptual framework is developed to be inserted into daily activities of an aerodynamic CFD group. The framework is implemented for both Windows and Linux-running platforms, and it is augmented by a user-friendly graphical interface. Usage of the framework is illustrated in the paper by 2-D and 3-D aerodynamic optimization of a cruise configuration for dierent flight conditions. The aspects investigated include the influence of the number of individuals on the aerodynamic coecients, the eect of boundary layer transition location on the final optimized shape, and the benefits of the solver fidelity level as compared to the computational cost. Moreover, the use of a neural network is evaluated in order to analyze the benefits that this methodolgy can bring to the implemented framework in terms of computational cost.

Chimera Simulations of Supersonic Flows over a Complex Satellite Launcher Configuration

An effort is underway to develop a chimera e ow simulation code capableof handling the external aerodynamics of general launch vehicle cone gurations. Aerodynamic results are presented referring to inviscid, laminar, and turbulent viscous simulations of the e rst Brazilian satellite launch vehicle during its e rst-stage e ight. The e nite difference method is applied to the governing equations, written in conservation-law form for general body conforming curvilinear coordinates. The spatial discretization is accomplished with a central difference scheme in which artie cial dissipation terms, based on a scalar, nonisotropic model, are added to the numerical scheme to maintain stability. The time-marching process is accomplished with a e ve-stage, second-order accurate, Runge ‐ Kutta scheme. Studies of mesh ree nement are also presented as a part of the validation effort, with the objective of providing a certie ed e ow simulation capability for actual engineering work.

Active Camber Morphing Wings Based on Compliant Structures: an Aeroelastic Assessment

The paper summarizes the recent activities performed at Politenico di Milano in the framework of FP7NOVEMOR Project related to the application of morphing technologies and in particular to the variable camber concept. After a short reminder on the tools developed aiming at the design of variable camber morphing wings, the paper describes the main results obtained from the application of this morphing concept to a typical regional aircraft. Then, the preliminary results of the final aeroelastic assessment are reported. In particular the proposed multi–fidelity approach is briefly discussed together with the description of the tools and models adopted.

CHIMERA SIMULATIONS OF VISCOUS FLOWS OVER A COMPLEX SATELLITE LAUNCHER CONFIGURATION

This work is inserted in the effort to develop a Chimera flow simulation code capable of handling general launch vehicle configurations. The work presents aerodynamic results referring to laminar and turbulent viscous simulations over the first Brazilian satellite launch vehicle, VLS, during its first-stage flight. The finite difference method is applied to the governing equations written in conservation- law form for general body conforming curvilinear coordinates. The spatial discretization is accomplished with a central difference scheme in which artificial dissipation terms, based on a scalar, non-isotropic model, are added to the numerical scheme to maintain stability. The time march process is accomplished with a 5-stage, 2nd-order accurate, Runge-Kutta scheme. Studies of mesh refinement are also presented as a part of the validation effort which has the objective of providing a certified flow simulation capability for actual engineering work.

A Study of Transport Aircraft High-Lift Design Approaches

The high-lift design process is focused in obtaining the best aerodynamic shape and the optimized position for the high-lift devices. The main requirement for the design process is strongly connected with the need to achieve a maximum target lift coefficient for the landing and take-off maneuvers. In this context, the present work has the objective of presenting two numerical methodologies to predict the maximum lift coefficient, namely, the quasi-3D and the 3D approaches. The NLR7301 airfoil configuration has been chosen for the study, since it is a non-proprietary geometry. The numerical simulations are performed with the CFD++ and VSAERO commercial codes. The meshes are created with the ICEM mesh generator. The work also presents a sensitivity analysis of the aerodynamic parameters, such as the global 3-D lift coefficient or the section lift coefficient, with regard to changes in the numerical setup. In the present study, the results obtained by the two methodologies showed a certain level of discrepancy. A dispersion of about 6% in the prediction of the maximum C L was obtained by the quasi-3D analysis, while the 3D methodology presented a premature stall. I. Introduction he high-lift design process is focused in obtaining the best aerodynamic shape and the optimized position for the high-lift devices. The main requirement for the design process is strongly connected with the need to achieve a maximum target lift coefficient (C L) for the landing and take-off maneuvers. The definition of the target landing/take-off maximum C L depends on the mission to be carried out by the airplane. The design process must be effective in achieving the target C L due to the penalization that a bad design can cause on some macro variables related with the performance or the operation of the airplane. The subject of high-lift devices has always been an area of special interest to airplane designers. The accurate prediction of pressure distributions, boundary layer confluences, and detached flow regions over the multi-element high-lift wings plays a fundamental role in the design of high-lift devices. The complex physical phenomena involved in such flowfield are responsible for the difficulty associated with high-lift design. It is important to observe that currently most of the aerodynamic design is performed with the aid of CFD. Lately, the advance of CFD has produced an important change in the form in which aerodynamic analysis and design are performed in the aeronautical industry. CFD has reached such a level of importance that one cannot imagine an aerodynamic department without a CFD group. The constant development of CFD, as a tool capable of producing complex analyses, has been responsible for the spread of its use all over the world. Until a few years ago, aerodynamic design was driven by simplified analytical methods and empirical formulations, together with massive wind tunnel campaigns to validate the aerodynamic design. Today the fierce competition between the aeronautical manufacturing companies does not allow such a costly design procedure anymore. The current tendency encourages the use of wind tunnel tests just as a way to corroborate the aerodynamic design, previously performed with CFD. 1-2 The world aeronautical manufacturing companies are eager to reduce the inherently high cost associated with wind tunnel tests. In order to give an idea of the amount of money required for a wind tunnel campaign, the milled model costs might reach the order of hundreds of thousands of dollars. This cost intrinsically depends on whether the model is a full or a half model, and its geometric complexity. The cost of the test might start at a few hundreds of thousands of dollars and reach the mark of millions

Chapter 6 – Expected Performances

The present work addresses the aerodynamic design of a Reference Aircraft (RA) and the assessment of the potential benefits that an active camber morphing can bring in terms of aircraft performances. The RA is representative of a typical regional jet capable of carrying 113 PAX in a single economic class and providing the operational flexibility to fly different missions at the transonic regime. The implementation of the active camber concept is based on the use of classical control surfaces, as well as on conformable morphing control surfaces. Aiming at the optimal design of these morphing devices, a dedicated procedure is introduced for the definition of the optimal shape while taking into account both aerodynamic and structural constraints. This paper briefly summarizes the tools developed and the results obtained, including potential benefits such as fuel and weight saving.

Effect of two-dimensional surface irregularities on swept wing transition : Forward facing steps

An experimental investigation was carried out to examine the effect of two-dimensional Forward Facing Steps surface irregularities, on the laminar-to-turbulent boundary-layer transition on a 45° swept-wing. For the clean reference case, the numerical boundary-layer flow is calculated from pressure measurements, and a thorough linear stability analysis is performed for all variations of Reynolds number and angle of attack. Infrared thermography is employed to determine the transition-front location which is associated to an N-Factor, calculated from the linear stability analysis. The change in the amplification factor ∆N, caused by the addition of the surface irregularity, is analyzed. The reduction in the critical N-factor is observed to correlate with the estimated cross-flow instability vortex core height to step height ratio and the relative step height. The work presented in this paper is part of an ongoing research project to characterize the effect that surface irregularities have on boundary layer transition. The N-method offers an overview of the phenomena related to FFS, capable of guiding future investigations into the underlying flow mechanisms.