Aircraft Drag Prediction and Reduction. Addendum 1

Aircraft Drag Prediction and Reduction. Addendum 1
Author:
Publisher:
Total Pages: 34
Release: 1986
Genre:
ISBN:
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The accurate prediction of aircraft aerodynamic drag is a generally recognized and respected problem. So is the accurate measurement of drag in the wind tunnel that, eventually, forms the basis for full scale drag prediction. In the past 15 years Computational Fluid Dynamics (CFD) has emerged as an additional and complementary tool for aerodynamic design and analysis. The purpose of this lecture is to review and comment on its role as a drag prediction and analysis tool. The aerodynamic design process of aircraft is characterized by a sequence of design and analysis cycles. In each cycle a (further) reduction of drag will, generally, be one, but not the only objective. Identification of the source of an unacceptably or undesirably high drag level or drag variation with lift or Mach number is a prerequisite for a successful drag reduction program. Identification of drag sources may follow different approaches. The classical or phenomenological one is based on the availability of overall force (wind tunnel) data only, in combination with simple, semi-empirical theory. CFD, as we shall see later, offers possibilities for a more physically/analytically oriented approach in which the various contributions to drag are distinguished by the underlying physical mechanisms rather than by the observed aerodynamic force variation phenomena. It will also be demonstrated that, in spite of its current shortcomings, CFD is a powerful tool for drag diagnostics. The final part of the lecture contains a discussion on computational drag minimization.

Aircraft Design

Aircraft Design
Author: Ajoy Kumar Kundu
Publisher: Cambridge University Press
Total Pages: 649
Release: 2010-04-12
Genre: Technology & Engineering
ISBN: 1139487450
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Aircraft Design explores fixed winged aircraft design at the conceptual phase of a project. Designing an aircraft is a complex multifaceted process embracing many technical challenges in a multidisciplinary environment. By definition, the topic requires intelligent use of aerodynamic knowledge to configure aircraft geometry suited specifically to the customer's demands. It involves estimating aircraft weight and drag and computing the available thrust from the engine. The methodology shown here includes formal sizing of the aircraft, engine matching, and substantiating performance to comply with the customer's demands and government regulatory standards. Associated topics include safety issues, environmental issues, material choice, structural layout, understanding flight deck, avionics, and systems (for both civilian and military aircraft). Cost estimation and manufacturing considerations are also discussed. The chapters are arranged to optimize understanding of industrial approaches to aircraft design methodology. Example exercises from the author's industrial experience dealing with a typical aircraft design are included.

A CFD

A CFD
Author:
Publisher:
Total Pages: 37
Release: 1998
Genre:
ISBN:
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With advanced subsonic transports and military aircraft operating in the transonic regime, it is becoming important to determine the effects of the coupling between aerodynamic loads and elastic forces. Since aeroelastic effects can significantly impact the design of these aircraft, there is a strong need in the aerospace industry to predict these interactions computationally. Such an analysis in the transonic regime requires high fidelity computational fluid dynamics (CFD) analysis tools, due to the nonlinear behavior of the aerodynamics in the transonic regime and also high fidelity computational structural dynamics (CSD) analysis tools. Also, there is a need to be able to use a wide variety of CFD and CSD methods to predict aeroelastic effects. Since source codes are not always available, it is necessary to couple the CFD and CSD codes without alteration of the source codes. In this study, an aeroelastic coupling procedure is developed to determine the static aeroelastic response of aircraft wings using any CFD and CSD code with little code integration. The aeroelastic coupling procedure is demonstrated on an F/A-18 Stabilator using NASTD (an in-house McDonnell Douglas CFD code) and NASTRAN. In addition, the Aeroelastic Research Wing (ARW-2) is used for demonstration of the aeroelastic coupling procedure by using ENSAERO (NASA Ames Research Center CFD code) and a finite element wing-box code. The results obtained from the present study are compared with those available from an experimental study conducted at NASA Langley Research Center and a study conducted at NASA Ames Research Center using ENSAERO and modal superposition. The results compare well with experimental data.

Uncertainty Quantification in Computational Fluid Dynamics and Aircraft Engines

Uncertainty Quantification in Computational Fluid Dynamics and Aircraft Engines
Author: Francesco Montomoli
Publisher:
Total Pages:
Release: 2015
Genre:
ISBN: 9783319146829
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This book introduces novel design techniques developed to increase the safety of aircraft engines. The authors demonstrate how the application of uncertainty methods can overcome problems in the accurate prediction of engine lift, caused by manufacturing error. This in turn ameliorates the difficulty of achieving required safety margins imposed by limits in current design and manufacturing methods. This text shows that even state-of-the-art computational fluid dynamics (CFD) are not able to predict the same performance measured in experiments; CFD methods assume idealised geometries but ideal geometries do not exist, cannot be manufactured and their performance differs from real-world ones. By applying geometrical variations of a few microns, the agreement with experiments improves dramatically, but unfortunately the manufacturing errors in engines or in experiments are unknown. In order to overcome this limitation, uncertainty quantification considers the probability density functions of manufacturing errors. It is then possible to predict the overall variation of the jet engine performance using stochastic techniques. Uncertainty Quantification in Computational Fluid Dynamics and Aircraft Engines demonstrates that some geometries are not affected by manufacturing errors, meaning that it is possible to design safer engines. Instead of trying to improve the manufacturing accuracy, uncertainty quantification when applied to CFD is able to indicate an improved design direction. This book will be of interest to gas turbine manufacturers and designers as well as CFD practitioners, specialists and researchers. Graduate and final year undergraduate students may also find it of use.