Blended Wing Body Aircraft Research Articles

Effect of geometric variations on the wing rock of blended wing-body aircraft

Blended wing-body configurations are anticipated to dominate future transport and military aerospace designs. The departure of the conventional tube-wing configuration has opened several areas of investigation. These designs are susceptible to lateral instability during landing, takeoff, and maneuvering flight despite having improved aerodynamics because of their tailless nature. One of these instabilities, Wing-Rock, poses significant performance and operational difficulties and can potentially cause crashes. Though experimental and numerical studies of the aerodynamics and stability of blended wing-body configurations have been conducted, wing-rock characteristics still need to be identified in the literature. This research aims to investigate these characteristics at low subsonic speeds with varying outboard sweep and geometric twist angles. The study includes a numerical approach based on the rigid body free-vibration method in single roll degree of motion, which uses three-dimensional unsteady Reynolds’ Average Navier Stokes equations, and an analytical approach based on the multiple time scale method, which captures the crucial aspect of the wing rock system. The findings show that the geometrical parameters significantly impact the wing rock characteristics, which are unique to such novel tailless designs.

Flyover auralization of a blended wing body aircraft considering atmospheric turbulence effects

In the ARTEM project a novel blended wing body (BWB) long-range aircraft was designed and optimized for low-noise operation. Virtual flyovers of different BWB vehicle variants were synthesized and auralized in the AuraLab using a loudspeaker array. Prior to auralizing the novel aircraft, the applied methods were hierarchically validated by comparison with field recordings of existing jet aircraft, assessing acoustical indices, time-frequency features, perceived plausibility, and induced noise annoyance. To achieve convincing syntheses, the focus was on developing new auralization models for a realistic representation of atmospheric turbulence effects. The syntheses of the BWB obtained with the successfully validated methods were then used in psychoacoustic laboratory experiments for perception-based evaluation regarding (minimized) noise annoyance. The evaluation revealed that, while the BWB may initially be perceived as somewhat more unfamiliar, it is substantially less annoying than current tube-and-wing long-range aircraft of similar range and mission for take-offs as well as for landings.

Research on stability for blended-wing-body aircraft

The primary goal of this research is to research the stability properties of a blended-wing-body (BWB) aircraft. This section examines the assessment and selection of aircraft design parameters, planform design, and reflex wing and conducts a complete aircraft stability analysis. A BWB aircraft conceptual design has been completed and the design. To attain static stability, it was examined and refined. The BWB aircraft's study was performed at three distinct values. The analytical findings were used to calculate the angle-of-attack (AOA) and the stall AOA. We determined the estimated initial departure angle of attack and departure region by assessing the results of the trials and a set of stability criteria.

Numerical Study of Skipping Motion of Blended-Wing–Body Aircraft Ditching on Calm/Wavy Water

The blended-wing–body (BWB) is hoped to be the main configuration of next-generation transport aircraft. However, its large flat belly may cause a violent skipping motion during the ditching on water. In this paper, the skipping motions of a BWB aircraft ditching on calm and wavy water are numerically investigated. The finite volume method with the volume-of-fluid approach is employed to solve the unsteady Reynolds-averaged Navier–Stokes equations. A coupled method between global moving mesh and overset mesh is proposed to avoid a large background domain and improve the prediction accuracy of the free surface, and its accuracy is well validated by predicting the motions of a skipping stone, the hydrodynamic load and pressure on a flat plate in high-speed ditching, and the fifth-order Stokes wave in a dynamic wave tank. At the beginning of every surfing stage, the flat belly of BWB aircraft impacts heavily on the water surface at a smaller pitch angle and larger speed, resulting in the local vertical overload peak, which is much larger than the peak in the porpoising motion. The wavy water surface intensifies the heave and pitch motions and increases the risk of the cockpit diving into the water.

Conceptual Design of Layered Distributed Propulsion System to Improve Power-Saving Benefit of Boundary-Layer Ingestion

DPS (distributed propulsion system) utilizing BLI (boundary-layer ingestion) has shown great potential for reducing the power consumption of sustainable AAM (advanced air mobility), such as BWB (blended-wing body) aircraft. However, the ingesting boundary layer makes it easier for flow separation to occur within the S-shaped duct, and the consequent distortion due to flow separation can dramatically reduce the aerodynamic performance of the fan, which offsets the power-saving benefit of BLI. By analyzing the source of power saving and power loss of BLI, this paper presents the LDPS (layered distributed propulsion system) concept, in which the freestream flow and boundary-layer flow are ingested separately to improve the power-saving benefit of BLI. In order to preliminarily verify the feasibility of LDPS, an existing DPS is modified. The design parameters and the system performances of LDPS are studied using a 1D engine model. The results show that there is an optimal ratio of the FPR (fan pressure ratio) for the FSE (freestream engine) to the BLE (boundary-layer engine) that maximizes the PSC (power-saving coefficient) of LDPS. This optimal ratio of FPR for the two fans can be obtained when the exit velocities of FSE and BLE are the same. Under the optimal ratio of FPR for the two fans, the PSC of LDPS is improved by 5.83% compared to conventional DPS.

Mission-Driven Inverse Design of Blended Wing Body Aircraft with Machine Learning

The intent of this work was to investigate the feasibility of developing machine learning models for calculating values of airplane configuration design variables when provided time-series, mission-informed performance data. Shallow artificial neural networks were developed, trained, and tested using data pertaining to the blended wing body (BWB) class of aerospace vehicles. Configuration design parameters were varied using a Latin-hypercube sampling scheme. These data were used by a parametric-based BWB configuration generator to create unique BWBs. Performance for each configuration was obtained via a performance estimation tool. Training and testing of neural networks was conducted using a K-fold cross-validation scheme. A random forest approach was used to determine the values of predicted configuration design variables when evaluating neural network accuracy across a blended wing body vehicle survey. The results demonstrated the viability of leveraging neural networks in mission-dependent, inverse design of blended wing bodies. In particular, feed-forward, shallow neural network architectures yielded significantly better predictive accuracy than cascade-forward architectures. Furthermore, for both architectures, increasing the number of neurons in the hidden layer increased the prediction accuracy of configuration design variables by at least 80%.

Perception-based noise assessment of a future blended wing body aircraft concept using synthesized flyovers in an acoustic VR environment—The ARTEM study

New aircraft concepts are currently being developed with the goal of less emissions of CO2 and noise. Remarkable noise reductions in long-range aircraft can only be expected from disruptive vehicle designs, new propulsion systems and specific low-noise technologies. In this paper, one such future vehicle design, a blended wing body (BWB) long-range aircraft, is described and studied with respect to sound levels on the ground, sound characteristics and noise annoyance. Virtual flyovers of different vehicle variants were synthesized and auralized in an acoustic VR environment, and investigated through psychoacoustic laboratory experiments. The applied methodology was successfully hierarchically validated by comparison with measurements of existing jet aircraft, assessing acoustical indices, time-frequency features, perceived plausibility, and induced noise annoyance. The perception-based evaluation of the BWB revealed that, while the BWB aircraft may initially be perceived as somewhat more unfamiliar, they are substantially less annoying than current tube-and-wing long-range aircraft of similar range and mission for take-offs as well as for landings. For the best BWB variant, noise annoyance was reduced by 4.3 units for departures and by 3.5 units for approaches on the 11-point scale. The main reason for these findings seems to be the acoustic shielding by the body of the extended fuselage, which was found to be an important factor in reducing sound levels in the order of 10–20 dB, and accordingly also to strongly reduce loudness. Additional low noise technologies and geared turbofan engines with a high bypass ratio further contributed to the reduction of noise annoyance of the BWB. A large part of the BWBs benefit could be explained by its lower sound levels, but additional benefits were found. The observed reduction in noise annoyance was found to be larger than what can be explained with conventional noise metrics. This benefit is probably due to more favorable sound characteristics compared to today's reference aircraft, such as less variation in time and less audible tones. The current study thus suggests that the studied BWB vehicle concept may substantially reduce noise annoyance on humans.

Engine Sonic Load Prediction of Blended Wing Body Aircraft

The sonic load of the engine is the input for cabin noise design and acoustic fatigue verification in civil aircraft. Based on the engine static noise database, an engineering prediction method for blended wing body aircraft engine sonic load in flight is developed. In the process of sonic load prediction, the sound source position correction, geometric diffusion, flight effect and airframe scattering effect of engine component noise are considered. The flight effect and air-frame scattering effect of engine component level noise are simulated and analyzed. The overall sound pressure level distribution and sound load spectrum at typical positions of blended wing body aircraft engine are given. The results show that fan inlet noise is the most important component of the engine sonic load on the BWB aircraft surface, and the maximum value of engine sonic load on the upper surface of blended wing body aircraft is 134 dB, which is higher than that of conventional wing crane aircraft.

Design Investigation of Potential Long-Range Hydrogen Combustion Blended Wing Body Aircraft with Future Technologies

Present work investigates the potential of a long-range commercial blended wing body configuration powered by hydrogen combustion engines with future airframe and propulsion technologies. Future technologies include advanced materials, load alleviation techniques, boundary layer ingestion, and ultra-high bypass ratio engines. The hydrogen combustion configuration was compared to the configuration powered by kerosene with respect to geometric properties, performance characteristics, energy demand, equivalent CO2 emissions, and Direct Operating Costs. In addition, technology sensitivity studies were performed to assess the potential influence of each technology on the configuration. A multi-fidelity sizing methodology using low- and mid-fidelity methods for rapid configuration sizing was created to assess the configuration and perform robust analyses and multi-disciplinary optimizations. To assess potential uncertainties of the fidelity of aerodynamic analysis tools, high-fidelity aerodynamic analysis and optimization framework MACH-Aero was used for additional verification. Comparison of hydrogen and kerosene blended wing body aircraft showed a potential reduction of equivalent CO2 emission by 15% and 81% for blue and green hydrogen compared to the kerosene blended wing body and by 44% and 88% with respect to a conventional B777-300ER aircraft. Advancements in future technologies also significantly affect the geometric layout of aircraft. Boundary layer ingestion and ultra-high bypass ratio engines demonstrated the highest potential for fuel reduction, although both technologies conflict with each other. However, operating costs of hydrogen aircraft could establish a significant problem if pessimistic and base hydrogen price scenarios are achieved for blue and green hydrogen respectively. Finally, configurational problems featured by classical blended wing body aircraft are magnified for the hydrogen case due to the significant volume requirements to store hydrogen fuel.

Identification of Lateral-Directional Aerodynamic Parameters for Aircraft Based on a Wind Tunnel Virtual Flight Test

In the early stages of aircraft design, a scaled model of the aircraft is installed in a wind tunnel for dynamic semi-free flight to approximate real flight, and the test data are then used to identify the aerodynamic parameters. However, the absence of the translational motion of the test model makes its flight dynamics different from those in free flight, and the effect of this difference on parameter identification needs to be investigated. To solve this problem, a 3-DOF wind tunnel virtual flight test device is built to fix the test model on a rotating mechanism, and the model is free to rotate in three axes through the deflection of the control surfaces. The flight dynamics equations for the wind tunnel virtual flight test are established and expressed as a decoupled form of the free flight force and the influence of the test support frame force on the model’s motions through linearization. The differences between wind tunnel virtual flight and free flight are analysed to develop a model for the identification of aerodynamic parameters. The selection of the lateral-directional excitation signal and the design method of its parameters are established based on the requirements for the identifiability of the aerodynamic derivatives, and a step-by-step method for the identification of aerodynamic force and moment derivatives is established. The aerodynamic parameter identification results of a blended wing body aircraft show that the identification method proposed in this paper can obtain results with high accuracy, and the response of the modified motion model is consistent with that of the free flight motion model.

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.

Flyover noise evaluation of low-noise technologies applied to a blended wing body aircraft

In the frame of the European research project ARTEM (Aircraft noise Reduction Technologies and related Environmental iMpact), new aircraft architectures and alternative propulsion systems, e.g. Blended Wing Body (BWB) and geared turbofan engine concept, are investigated, as well as innovative noise reduction technologies such as metamaterials and low noise high-lift device systems. A noise impact assessment has been performed on a long-haul BWB concept developed by Roma Tre University, using the System Noise Prediction Tools of ONERA (CARMEN) and DLR (PANAM). First, shielding effects on the main noise sources are discussed, through installation effects hemi-spheres at chosen frequencies around the aircraft. Based on the shielding assessment, detailed take-off and landing procedures are simulated for several aircraft configurations. Two motorisations of the BWB are evaluated (BPR 8 and BPR 12), provided by RWTH Aachen. Finally, the most promising low noise technologies developed in the frame of ARTEM are applied, and their impact on noise levels on the ground is discussed. It can be demonstrated how the specific aircraft configuration, the engine type and the additional low-noise technology result in a significant overall noise reduction. A joint conference paper presents flyover auralisations based on these noise emission calculations.

A Fast Aerodynamic Model for Aircraft Multidisciplinary Design and Optimization Process

A multidisciplinary design analysis and optimization process is developed at ONERA for the design of tube and wing and blended wing–body aircraft configurations. This process is composed of different disciplinary modules (geometry, propulsion, aerodynamics, structure, handling qualities and flight mission), and the overall process considers different fidelity levels for these modules at each step of the design process. This article describes the low-fidelity aerodynamic module used during the preliminary design optimization process. Analytical formulations retained for lift and drag components are presented in the first part. Then, the performances estimated by the aerodynamic module on some reference configurations are compared with both numerical and experimental data, showing a quite good agreement for both tube and wing and blended wing–body configurations not only for global performance but also for individual drag components.

Surrogate Model Development for Optimized Blended-Wing-Body Aerodynamics

In the conceptual design phase of conventional-configuration aircraft, calibrated low-fidelity methods provide sufficiently accurate estimates of aerodynamic coefficients. It has been observed, however, that for blended-wing–body aircraft, important flow effects are not captured adequately with low-fidelity aerodynamic tools. Consequently, high-fidelity methods become necessary to study blended-wing–body aerodynamics. Since repeated function calls are needed in an optimization loop, high-fidelity analysis is prohibitively expensive in the conceptual design phase, where several optimization scenarios are considered. In this paper, the integration of high-fidelity data for blended-wing–body aircraft for a mission calculation module is presented. A surrogate model based on Gaussian processes (GPs) with acceptably low prediction error is sought as an alternative to Reynolds-averaged Navier–Stokes computational fluid dynamics. Three adaptations are considered: sparse GPs, mixtures of GP approximators, and need-based filtering for GP. The results provide benchmark values for this case and show that the combination of subsonic and transonic behaviors in the training set is problematic and that, for the considered datasets, sparse GP models suffer from oversmoothing, while mixtures of GP models suffer from overfitting. From the error levels, it is observed that a GP with an infinitely differentiable squared exponential kernel based on reduced data pertinent to mission analysis is the most effective option.

Design Methods for Variable-Stiffness Super-Ellipsoidal Pressure Vessels Under Thermomechanical Loading

Pressure vessels are widely used in a broad range of applications in many industries, including possible use for hydrogen storage. Additionally, pressure vessels comprise non-circular-cross-section fuselages such as in blended-wing–body aircraft. Failure performance, weight, and packing efficiency are important factors that should be considered when designing pressure vessels. Often, lightweight pressure vessels maximize their volume for a given available space volume and withstand substantial internal pressure. Bend-free super ellipsoids of revolution, enabled by stiffness tailoring via variable-angle tow placement of composite plies, present an appealing solution that makes them possible candidates for future composite pressure vessels. To date, the bend-free design methodology for super ellipsoids of revolution has only been developed under uniform internal pressure loading. However, in reality, pressure vessels can also be subjected to thermal loads during service. Therefore, this study develops an initial bend-free design methodology for super ellipsoids of revolution that are subjected to both uniform internal pressure and thermal loads.

Numerical Analysis of Porpoising Stability Limit of a Blended-Wing–Body Aircraft During Ditching

The ditching processes of a blended-wing–body (BWB) aircraft under different initial speeds and pitch angles are simulated by numerically solving the unsteady Reynolds-averaged Navier–Stokes equations and the realizable turbulence model using the finite volume method. The volume-of-fluid model is adopted to capture the water–air interface. The six-degree-of-freedom model is employed to couple fluid dynamics and aircraft rigid-body kinematics. The global moving mesh is used to deal with the relative motion between the aircraft and the water. It is found that the plane composed of initial speed and pitch angle can be divided into two regions by a stability limit line, that is, the porpoising motion region (the aircraft takes coupled oscillatory motion between heaving and pitching) with large initial speeds and pitch angles and the stable motion region with low initial speeds and pitch angles. When the initial speed is large, the aircraft’s pitch-up moment peak and heaving amplitude are enhanced. Hence the aircraft carries out the porpoising motion. For the large initial pitch angle, the water entry depth of the aircraft increases and the waterline moves forward, which produces a more significant pitch-up moment peak and overload peak. As a result, the aircraft conducts the porpoising motion. The porpoising stability of the BWB configuration is obviously worse than the conventional and flying wing configurations. When the BWB aircraft ditches on water, the pilots should reduce the initial speed and pitch angle as much as possible to avoid the dangerous porpoising motion.

Shape Optimization with a Flattening-Based Morphing Method

In shape optimization problems, generating variously shaped designs is an important task. In this study, a new design method called the flattening-based morphing method, which can create various designs efficiently based on baseline objects, is proposed. In the flattening-based method, anchor points are defined for each baseline object to set correspondence among the baseline objects, and each baseline object is mapped to 2D parametric space in a way that places all corresponding anchor points of the baseline objects at the same location. Then, remeshing is carried out to make the baseline objects’ mesh topologically identical in the parametric space. After these remeshed baseline objects are parameterized back to the physical space, the morphed object is created by computing the positions of its vertices as a weighted sum of the baseline meshes’ vertices. When the flattening-based morphing method is applied to find the optimal shape of a blended-wing body aircraft using an artificial neural network (ANN), the aerodynamic performance enhanced optimal model with an appropriate loading capacity is successfully achieved using three baseline models. The simulation results of the baseline models and optimization results are also provided in the current study.

Energy-Based Aerodynamic Analysis on the Blended-Wing-Body Aircraft with Boundary Layer Ingestion

This study is aimed at evaluating the energy saving benefit and its limitation of the boundary layer ingestion (BLI) applied to a transonic blended-wing-body (BWB) aircraft. The power balance method is adopted in the aerodynamic performance analysis of the aircraft. We further improve the one-dimensional analysis framework by adding the pressure volumetric work term in the power balance equation for the application in compressible flow with shock wave regions. A determining expression for the power-saving coefficient (PSC) of the BLI effect is also deduced, which is related to a BLI fraction, the airframe dissipation component ratios, and the specific thrust of the propulsor. This expression provides a way for the preliminary evaluation and comparison of BLI benefits applied in different aircraft configurations. The flow quantities of three different configurations are obtained by 3D Reynolds-averaged Navier–Stokes (RANS) numerical simulations for the calculation of aerodynamic dissipation components. The grid refinement and domain size study shows that the calculated force coefficients and total dissipation coefficient have a good convergence characteristic with the mesh refinement and are insensitive to the variation in domain size. The evaluated PSC of the BWB aircraft with a BLI propulsor is 5% using the previously developed determining expression. The maximum of PSC is 18.8%. The following comparison of dissipation components for the power-on and power-off cases shows that the benefit of BLI is slightly underestimated by the determining expression of PSC. The reason is that the variation in the boundary layer velocity profile at the trailing edge of the center body part is neglected, which is due to the installation of the propulsor. Furthermore, when the BLI propulsor is applied to a BWB aircraft, the variation in trailing edge vortex dissipation and volumetric pressure work term should be studied in detail.

Recent developments of blended wing body aircraft: experimental, numerical and theoretical approaches

Recent developments of blended wing body aircraft: experimental, numerical and theoretical approaches

Using axiomatic design approach in preliminary design of a blended wing body aircraft

PurposeThis study aims to present a method for improving the preliminary design process of an aircraft.Design/methodology/approachThe approach of this paper is using Axiomatic Design (AD) principles in the aircraft preliminary design process. The aircraft design process consists of modules and disciplines, which are loosely coupled that can disrupt designers’ ability. Consequently, designers should define suitable functional requirements (FRs) and design parameters for products to avoid or limit coupling between them. As modular architecture is commonly defined as having a one-to-one mapping from the function domain to the physical domain, the independence axiom in AD could support the modularity of the design process. Therefore, these features guide us to use AD principles at the first steps of the aircraft design process.FindingsReduction coupling between different FRs and consequently less repetitive activities and design iteration in the design process by using AD principles are the finding of this paper.Practical implicationsThis concept could be used for the design process of every complex product.Originality/valueLooking at the preliminary design of a Blended Wing Body unmanned aerial vehicle with respect to the AD is a new technique to achieve a modular design process.