Design Of Aircraft Configurations Research Articles

Including Blade Elasticity into Frequency-Domain Propeller Whirl Flutter Analysis

Whirl flutter as an aeroelastic instability can be a limiting factor in the design and certification of turboprop aircraft configurations, especially for the engine suspension. Whirl flutter prediction for these configurations is currently done in the frequency domain using rigid propeller aerodynamic derivatives. Blade flexibility is neglected in this process, although it is known to have an impact on whirl flutter predictions. This paper uses frequency-domain transfer matrices for the propeller hub loads identified from a time-domain multibody simulation model of an isolated turboprop propeller and included into a frequency-domain flutter analysis to study the impact of blade elasticity on propeller whirl flutter. Results demonstrate a significantly stabilizing effect of blade elasticity on propeller whirl flutter due to a reduction of the destabilizing pitch-yaw cross-coupling moment. The method demonstrated in this paper is applicable to arbitrary time-domain propeller models and compatible with standard frequency-domain flutter processes, allowing for increased fidelity in the flutter prediction process.

Aerodynamic Effects of a Wing Surface Heat Exchanger

One challenge for the design and analysis of hybrid electric aircraft configurations is an increased demand in the rejection of excess waste heat. A wing surface heat exchanger concept, which is explored as part of the IMOTHEP project, foresees transferring heat from the propulsive electrical components to the wing surface of the aircraft. Here, heat is mainly dissipated and transported by forced convection. The present study focuses on the analysis of the impact of heat rejection via the wing surface on the wing’s heat transfer and aerodynamic efficiency characteristics. For this purpose, RANS CFD studies of 2D airfoils and a 3D wing propeller geometry of a regional turboprop configuration in representative flight conditions (take off, cruise, and taxi in) are carried out. For each condition, the influence of defining parameters, such as altitude, freestream velocity, angle of attack, surface temperature, and propeller thrust is explored. It is shown that, when increasing the wing surface temperature compared against the freestream temperature, the aerodynamic efficiency of the wing deteriorates for all flight conditions. In reference cruise conditions for example, the lift-to-drag ratio decreases by 4%, while the average heat transfer coefficient is reduced by almost 20% when increasing the surface temperature by 300 K. Furthermore, the propeller slipstream enhances the wing’s heat transfer capacity significantly.

Downwash modelling for three-lifting-surface aircraft configuration design

This paper introduces a semi-empirical model to predict the downwash gradient at the horizontal tail of a three-lifting-surface aircraft. The superposition principle applied to well established formulations valid for two lifting surfaces is not a reasonable approach to calculate the downwash of a canard-wing-tail layout, and this paper demonstrates that such a basic technique leads to incorrect results. Therefore, an ad hoc prediction model is proposed that considers the combined nonlinear effects of canard and main wing inductions on tail downwash, being based on a full factorial design sweep of CFD simulations obtained by varying the main geometrical parameters of the three lifting surfaces. A suitable analytical formula for the downwash gradient is established through a process of data analysis and factor extraction. The presented model extends the validity of the available models for traditional two-lifting-surface designs by means of a correction factor. The engineering estimation method introduced here exhibits an acceptable accuracy, as well as relatively small prediction errors, and it is suitable for conceptual and preliminary studies of three-surface layouts. The value of this methodology is confirmed by the validation with the results of numerical and experimental investigations on a case study aircraft.

Computational Analysis of Liquid Hydrogen Storage Tanks for Aircraft Applications

During the last two decades, the use of hydrogen (H2) as fuel for aircraft applications has been drawing attention; more specifically, its storage in liquid state (LH2), which is performed in extreme cryogenic temperatures (-253 °C), is a matter of research. The motivation for this effort is enhanced by the predicted growth of the aviation sector; however, it is estimated that this growth could be sustainable only if the strategies and objectives set by global organizations for the elimination of greenhouse gas emissions during the next decades, such as the European Green Deal, are taken into consideration and, consequently, technologies such as hydrogen fuel are promoted. Regarding LH2 in aircraft, substantial effort is required to design, analyze and manufacture suitable tanks for efficient storage. Important tools in this process are computational methods provided by advanced engineering software (CAD/CAE). In the present work, a computational study with the finite element method is performed in order to parametrically analyze proper tanks, examining the effect of the LH2 level stored as well as the tank geometric configuration. In the process, the need for powerful numerical models is demonstrated, owing to the highly non-linear dependence on temperature of the involved materials. The present numerical models' efficiency could be further enhanced by integrating them as part of a total aircraft configuration design loop.

Integration of the athena vortex lattice aerodynamic analysis software into the multivariate design synthesis of a blended wing body aircraft

This paper describes the process of integrating the Athena Vortex Lattice aerodynamics solver into a conceptual design environment for the multivariate design synthesis and optimisation of a Blended Wing Body (BWB) Aircraft. The work is derived from a PhD study, by one of the authors, which developed a design methodology for the conceptual design synthesis, analysis and optimisation of a BWB aircraft. This research was driven by the desire to utilise proven aerodynamic solvers, written in legacy codes, in modern computational design environments in order to improve the accuracy and fidelity in the design of novel aircraft configurations. The Athena Vortex Lattice code is a legacy code written in the FORTRAN programming language and developed at the Massachusetts Institute of Technology by Mark Drela while the multivariate conceptual design synthesis and optimisation was implemented in JAVA object oriented programming tool. The result from this study is the successful integration of the AVL software into the JAVA programming environment for the multivariate design synthesis optimisation of the BWB without loss of accuracy. The successful integration of these codes permit a more accurate design synthesis, analysis and optimisation of the novel aircraft configuration in the absence of a tailor-made and realistic empirical aerodynamic analysis model for the BWB Aircraft. Additionally, this research enables the automation of the design process and the accomplishment of the multivariate optimisation.

Lifting Fan의 위치가 복합형 UAM의 공력특성에 미치는 영향

Recently, the development of UAM, which was named by NASA as an alternative to solve the traffic and environmental problems caused by the rapidly progressing urbanization. When designing UAM, the location of lift fans greatly affects the core technology of the eVTOL type, distributed electric propulsion technology and aerodynamic performance of the vehicle. In this paper, a hybrid UAM model was designed using OpenVSP, an open source aircraft configuration modeling program, and aerodynamic analysis was performed according to the lift fans position change by the vortex lattice method. As a result, it is confirmed that the flight parameters and trailing wakes are stable by fixing the lift fan with the state rotated 0° to the flow direction of the aircraft during cruise flight. Also, OpenVSP is a suitable tool to be used in aircraft configuration modeling and design.

Conceptual design and comparative study of strut-braced wing and twin-fuselage aircraft configurations with ultra-high aspect ratio wings

Sustainable and fuel-efficient next-generation air transportation demands a step change in aircraft performance. The ultra-high aspect ratio wings (UHARW) configuration is one key enabling strategy for improving aircraft aerodynamic efficiency and reducing fuel consumption and emissions. Unconventional aircraft configurations and advanced airframe technologies are required to address the large bending moment and shear stresses in the UHARW structure. This paper considers two promising unconventional configurations for adopting UHARW design, including strut-braced-wing (SBW) and twin-fuselage (TF), with advanced airframe technologies, i.e., active flow control, active load alleviation, and advanced airframe structures and materials. Three typical missions, including short-range (SR), medium-range (MR), and long-range (LR), are considered for aircraft design. A conceptual design and performance analysis framework for SBW and TF configurations is developed in this paper. According to the mission profile and top-level requirements proposed for each mission, an SBW and a TF configuration are designed, respectively. A comparative study is carried out to determine the best-in-class configuration of the corresponding mission to evaluate the potential of SBW and TF configurations for next-generation sustainable aviation applications. The results showed that the TF configuration has a better wing weight reduction effect than the SBW configuration, and the MR-TF and LR-TF aircraft have lower takeoff weight and fuel weight than those of the SBW aircraft for the same mission. However, due to the adjustment of the cabin dimensions for the SR-TF aircraft, the SBW configuration outperforms the TF configuration in this mission.

Automated System for Three-Dimensional Layout and its Application in the Problems of Prospective Civil Aircraft Configuration Design

Представлена технология компоновки фюзеляжа с помощью разработанной в ЦАГИ «Автоматизированной системы трёхмерной компоновки пассажирского самолета» (АВТОКОМ). Приведены примеры практического применения АВТОКОМ при формировании облика перспективных гражданских летательных аппаратов.

Investigation of Mission-Driven Inverse Aircraft Design Space Exploration with Machine Learning

The goal of this work was to investigate the feasibility of developing machine learning models for predicting the values of aircraft configuration design variables when provided with time series of mission-informed performance parameters. Regression artificial neural networks, along with their associated training data, have been generated and tested for aircraft design space exploration scenarios. The bounds of the data used to train the models were partially informed by the configuration characteristics of the Boeing 737 Next Generation family. The effects of varying neural network architecture, along with the application of different data filtering schemes, on the models’ predictive accuracy have been examined. The results obtained demonstrated that cascade-forward shallow neural networks not only exhibited excellent generalization across the design space for which the model was calibrated for, but also showcased versatility when tasked with predicting design variable values for a configuration layout relatively different from the ones used for training. Furthermore, these models had favorable metrics in computational wall-clock time required and number of epochs needed for training.

Twin-fuselage configuration for improving fuel efficiency of passenger aircraft

The requirements of increasing air traffic volume while enhancing its sustainability for the next generation of air transportation demand a step change in aircraft performance, for which the development and technology escalation of ultra-high aspect ratio wings configurations is one key enabling strategy. However, compared with conventional aircraft, the ultra-high aspect ratio wings structure bears higher loads, which poses challenges to aircraft configuration design and related technologies. This paper describes the twin-fuselage (TF) concept as one of the promising configurations adopting ultra-high aspect ratio wings. A methodology of conceptual design and analysis framework for TF transport aircraft is developed by improving and integrating several methods and tools. A medium-range TF transport aircraft is designed, and a sensitivity analysis is carried out to explore the design space, and multidisciplinary design optimization is used to optimize the configuration of the TF transport aircraft. The results show a significant advantage of TF configuration over the conventional cantilever configuration, which presents reductions of 29.33% and 33.60% in the fuel consumption and maximum takeoff weight, respectively.

GROUND BASED VARIABLE STABILITY FLIGHT SIMULATOR

This paper discusses the development of a ground based variable stability flight simulator. The simulator is designed to meet the pilot training requirements on flying qualities. Such a requirement arose from a premier Flight-Testing School of the Indian Air Force. The simulator also provides a platform for researchers and aerospace students to understand aircraft dynamics, conduct studies on aircraft configuration design, flight mechanics, guidance & control and to evaluate autonomous navigation algorithms. The aircraft model is built using open source data. The simulator is strengthened with optimization techniques to configure variable aircraft stability and control characteristics to fly and evaluate the various aspects of flying qualities. The methodology is evaluated through a series of engineer and pilot-in-the-loop simulations for varying aircraft stability conditions. The tasks chosen are the proven CAT A HUD tracking tasks. The simulator is also reconfigurable to host an augmented fighter aircraft that can be evaluated by the test pilot team for the functional integrity as a fly-through model.

Automatic modeling of aircraft external geometries for preliminary design workflows

This article introduces a high-fidelity geometry definition methodology enabling Multidisciplinary Design, Analysis and Optimization (MDAO) of aircraft configurations. All definitions and functional features have been implemented within the JPAD software, a Java-based computing library for aircraft designers, which provides a dedicated geometric modeling module called JPADCAD. The geometric module, that comes as an application programming interface (API) built on top of the OpenCASCADE Technology solid modeling kernel, is conceived for the automatic production of parametric aircraft CAD geometries. The tool allows the definition of input geometries for low-fidelity as well as high-fidelity aerodynamic analyses, hence proves to be a key factor in the entire MDAO process, particularly in conceptual or preliminary design analysis workflows. The main goal of such a geometric library remains ease of use and support for automation to minimize unnecessary or repetitive human effort.The backbone of the presented methodology is the parametric definition of a generic commercial transport aircraft configuration that translates into software data structures and functionalities of CAD surface modelers. These aspects are discussed in the first part of the article. The second part presents a use case example of the geometric modeling API, where an automated aerodynamic analysis workflow is used to construct a prediction model for canard-wing configurations.

Influence of Transonic Flutter on the Conceptual Design of Next-Generation Transport Aircraft

Transonic aeroelasticity is an important consideration in the conceptual design of next-generation aircraft configurations. This paper develops a low-order physics-based flutter model for swept high-aspect-ratio wings. The approach builds upon a previously developed flutter model that uses the flowfield’s lowest moments of vorticity and volume-source density perturbations as its states. The contribution of this paper is a new formulation of the model for swept high-aspect-ratio wings. The aerodynamic model is calibrated using offline two-dimensional unsteady transonic computational-fluid-dynamics simulations. Combining that aerodynamic model with a beam model results in a low-dimensional overall aeroelastic system. The low computational cost of the model permits its incorporation in a conceptual design tool for next-generation transport aircraft. The model’s capabilities are demonstrated by finding transonic flutter boundaries for different clamped-wing configurations and investigating the influence of transonic flutter on the planform design of next-generation transport aircraft.

Obtaining minimum-drag shapes through surrogate-based global optimization: An application to the aerodynamic shape design of the landing gear master cylinder

Nowadays, one of the priorities of the European Commission is to reduce the environmental impact of aviation through the advanced design of novel aircraft configurations. This is of utmost importance in order to decrease the environmental footprint of aviation and to reduce fuel consumption and make airlines more profitable. This implies that new methods and tools for aerodynamic shape optimization will have to be developed, allowing aircraft configurations that cannot be obtained with traditional strategies. This paper focuses on the application of enhanced methods in aerodynamic shape design optimization to enable advanced aircraft configurations. In particular, this work aims to demonstrate the feasibility of the proposed strategy to reach optimal configurations that are far away from its baseline geometry. For this purpose, evolutionary algorithms are combined with support vector machines and applied to the optimization of a baseline geometry for different flow conditions. In particular, the selected application is based on the shape optimization problem of the landing gear master cylinder. Results pointed out the feasibility of the mentioned strategy to enable novel configurations within an aerodynamic shape optimization process.

Performance based multidisciplinary design optimization of morphing aircraft

The aeronautical industry is currently facing contradictory aircraft design requirements. There is a need to increase speed and capacity while minimizing the environmental impact. Novel configurations and morphing solutions are being proposed to address these requirements. In order to achieve the optimal aircraft configuration or the best morphing solution for a given mission, it is necessary to explore Multidisciplinary Design Optimization (MDO) solutions during the conceptual design phase. To this end, a MDO framework is proposed for conceptual design and analysis of new aircraft configurations, including the capability to analyze and quantify the effect of morphing wing solutions on aircraft performance. To illustrate the versatility and capabilities of the MDO tool, the design of a morphing wingtip on a conventional aircraft for two different flight conditions is assessed based on a reference model transport aircraft. Also, the performance of a morphing bending and twist control applied to a reference joined-wing configuration to improve lateral-directional stability is quantified. The results obtained show a significant reduction in fuel consumption when introducing a wingtip, although an incremental and negligible reduction was verified when enabling the wingtip with morphing capabilities. A considerable increase in yaw authority was achieved for the joined-wing model with the bending-twist morphing wingtip, however this morphing concept was not able to reach the same roll authority as conventional ailerons.

Automatic Optimization of Wing–Body–Under-the-Wing-Mounted-Nacelle Configurations

A robust and accurate method for aerodynamic shape optimization, previously developed by the authors, is extended to automatic multipoint design of aircraft configurations with under-the-wing-mounted nacelle. The shape is optimized for minimum drag at fixed lift subject to numerous geometrical and aerodynamic constraints. The method is driven by genetic algorithms and full Navier–Stokes computations combined with reduced-order-models approach. A recently developed optimization software based on the proposed method is applied to the design of a wing combined with fuselage and under-the-wing-mounted nacelle in a close coupling installation. A multipoint multiconstrained optimization carried out in a fully automatic mode achieved significant drag reduction within and beyond industry-realistic design conditions. The results indicate the ability of the developed automatic techniques to provide industrial-strength solutions that are not easily found through a traditional process of intelligent trial and error.

The Research of Supersonic Aircraft Low Sonic Boom Configuration Design and Optimizations

High noise level of sonic boom is one of the most important reasons that the supersonic transport can’t be applied to civil aviation broadly. Sonic boom is a complicated problem relating to aircraft configuration design, aerodynamics, acoustics and so on. The traditional sonic boom minimization theory is an inverse design method with single object, which makes it difficult to be applied in multi-objective optimization, effectively. For the low sonic boom configuration optimization, the sonic boom noise level prediction method based on supersonic linear theory was developed. The sonic boom level of a basic configuration of supersonic business jet was computed and the cause of formation of sonic boom was analyzed, based on which the fuse and wing plane wais optimized to decrease the noise level of sonic boom. Compared with the basic configuration, the sonic boom level of optimized configuration decreased distinctively, with the overpressure decreasing 41% and the A-weighted noise level decreasing 7.55 decibel. The aerodynamic characteristics of optimized configuration were computed. Compared with the basic configuration, the drag decreased obviously at the cruise condition without moment change.

Inverse Design Approach for Low-Boom Supersonic Configurations

The shaped sonic boom theory is a valuable, efficient, computationally economical, and robust tool in preliminary design of low-boom aircraft configurations. Instead of introducing a new F-function parameterization, because it has been investigated already in the past, this paper adopts a more general formulation proposed in the literature and focuses on reducing the limitations of the inverse method in the design process. Three main contributions are proposed: 1) a revisited procedure based on optimization to solve the coefficients of the F function that enables to switch between different parameterizations, 2) a definition of the geometry corresponding to the equivalent area distribution combined with a fuselage tailoring process based on direct shape optimization, and 3) a strategy to introduce a generic acoustic metrics in the definition of an optimum F function. The proposed strategy enables the designer to evaluate the geometry of a low-boom configuration that corresponds to a desired F function in a complete inverse design approach. In this way, the usual limits of the inverse method are significantly alleviated by the present method.

Comprehensive aircraft configuration design tool for Integrated Product and Process Development

This paper describes an efficient aircraft geometry design tool which is necessary for design and analysis applications through Integrated Product and Process Development (IPPD). The design process decomposes aircraft geometry into several components to represent it accurately and realistically with a reduced number of shape control parameters. For this purpose, several configuration representation algorithms are thoroughly investigated and discussed. The proposed configuration generation algorithm employs the super ellipse equation with simple analytic distribution functions, Class function/Shape function Transformation (CST) and can represent and manipulate complex shapes accurately with a small number of control parameters. A model of aircraft geometry, represented in this approach, can be applied to conceptual and preliminary stages of aircraft design and development with realistic and accurate configuration data. A Parameter-based Comprehensive Aircraft Design (PCAD) tool which implements a geometry generation process for aircraft design and optimization using customization of commercial computer-aided design software (CATIA V5) and the Product Data Management (Enovia Smarteam). The proposed configuration design tool could be especially efficient when automation, flexibility and rapid changes of geometry are required in a short time and with low computational resources.

Effective Design of Highly Maneuverable Tailless Aircraft

The correct design of unusual aircraft configurations is critical to achieving proper closed-loop flight dynamics. This paper is a guide based on decades of design experience on how the proper incorporation of yaw control power effects (their magnitude and bandwidth) within the iterative conceptual design process is critical to a successful aircraft design from a dynamics standpoint. Also critical is the open-loop level of stability. Factors that must be accounted for in designing tailless aircraft are also covered. These include the use of high-fidelity simulations with higher-order actuator models, time delays, and frequently excluded second-order effects for effective vehicle modeling and simulation.