Showing papers in "Journal of Aircraft in 2018"
TL;DR: The single-aisle turbo-electric aircraft with an aft boundary layer propulsor aircraft concept is estimated to reduce fuel burn by 12% through a turboelectric propulsion system with an electrically powered propulsion system as discussed by the authors.
Abstract: The single-aisle turboelectric aircraft with an aft boundary layer propulsor aircraft concept is estimated to reduce fuel burn by 12% through a turboelectric propulsion system with an electrically ...
66 citations
TL;DR: Aircraft designs have considered higher-aspect-ratio wings to reduce induced drag for improved fuel efficiency, however, to remain compliant with airport gate requirements, folding wingtips are preferred.
Abstract: Recent aircraft designs have considered higher-aspect-ratio wings to reduce induced drag for improved fuel efficiency; however, to remain compliant with airport gate requirements, folding wingtips ...
45 citations
TL;DR: The variable-camber continuous trailing-edge flap as mentioned in this paper is a novel control surface technology designed to serve as an aeroelastic wing shaping control device, capable of minimizing drag throughout an air...
Abstract: The variable-camber continuous trailing-edge flap is a novel control surface technology designed to serve as an aeroelastic wing shaping control device. Capable of minimizing drag throughout an air...
40 citations
TL;DR: In this paper, an experimental analysis was performed of the unsteady aerodynamic loading caused by the impingement of a propeller slipstream on a downstream lifting surface, which results in vibrations that are transmitted to the fuselage and are perceived inside the cabin as structure-borne noise.
Abstract: An experimental analysis was performed of the unsteady aerodynamic loading caused by the impingement of a propeller slipstream on a downstream lifting surface. When installed on an aircraft, this unsteady loading results in vibrations that are transmitted to the fuselage and are perceived inside the cabin as structure-borne noise. A pylon-mounted tractor–propeller configuration was installed in a low-speed wind tunnel at Delft University of Technology. Surface-microphone and particle-image-velocimetry measurements were taken to quantify the pressure fluctuations on the pylon and visualize the impingement phenomena. It was confirmed that the propeller tip vortex is the dominant source of pressure fluctuations on the pylon. Along the path of the tip vortex on the pylon, a periodic pressure response occurs with strong harmonics. The amplitude of the pressure fluctuations increases with increasing thrust setting, whereas the unsteady lift coefficient displays a nonmonotonic dependency on the propeller thrust....
34 citations
TL;DR: In this paper, the FP7-NOVEMOR Project framework was used for the design, manufacturing, and wind tunnel test of a wing model equipped with a wing simulator.
Abstract: This paper describes the activities performed at Politecnico di Milano within the FP7–NOVEMOR Project framework for the design, manufacturing, and wind tunnel test of a wing model equipped with mor...
29 citations
TL;DR: In this article, the complex propulsive-airframe and cross-propulsor interactions on an overwing distributed propulsion system with boundary-layer ingestion were characterized in a wind tunnel environment.
Abstract: This study aims to characterize the complex propulsive-airframe and cross-propulsor interactions that occur on an overwing distributed propulsion system with boundary-layer ingestion. Wind tunnel e...
28 citations
TL;DR: The development of a wing–body–nacelle–pylon–horizontal-tail configuration for a common research model is presented, with the focus on the aerodynamic design of the wing.
Abstract: The development of a wing–body–nacelle–pylon–horizontal-tail configuration for a common research model is presented, with the focus on the aerodynamic design of the wing. A contemporary transonic s...
28 citations
TL;DR: A nonlinear modeling strategy is introduced to drive online optimization-based controllers for trajectory tracking and stabilization of very flexible aircraft.
Abstract: A nonlinear modeling strategy is introduced to drive online optimization-based controllers for trajectory tracking and stabilization of very flexible aircraft. This is achieved thanks to a compact ...
26 citations
TL;DR: In this article, a magnetorheological (MR) damper for the landing gear system of airplanes is presented, which is used for the first time in the history of the world.
Abstract: In this research, a new type of magnetorheological (MR) damper, applicable to the landing gear system of airplanes, is presented. As a first step, an oleo-pneumatic damper, which is used for the la...
26 citations
TL;DR: In this paper, a detailed model of the nose section of a 90-seat configuration green regional aircraft concept was built and a nose landing-gear test campaign was conducted to evaluate its performance.
Abstract: This paper presents experimental results from a nose landing-gear test campaign. A highly detailed model of the nose section of a 90-seat configuration green regional aircraft concept was built and...
25 citations
TL;DR: In this paper, the system-level capabilities and component-level sensitivities of hybrid-electric propulsion systems were analyzed by modeling a twin-engine general-aviation aircraft, and the flight-performance model was presented.
Abstract: The system-level capabilities and component-level sensitivities of hybrid-electric propulsion systems were analyzed by modeling a twin-engine general-aviation aircraft. The flight-performance model...
TL;DR: This work provides a method for maintenance cost estimation for a civil aircraft that evaluates maintenance costs at a subsystem level in order to quantify the effective impact of each part of the aircraft.
Abstract: The present work provides a method for maintenance cost estimation for a civil aircraft. The model evaluates maintenance costs at a subsystem level in order to quantify the effective impact of each...
TL;DR: Two crossflow transition prediction approaches, the local C1-based approach and the local helicity based approach, have been implemented into a Reynolds-stress-based transition transport model of t... as mentioned in this paper.
Abstract: Two crossflow transition prediction approaches, the local C1-based approach and the local helicity-based approach, have been implemented into a Reynolds-stress-based transition transport model of t...
TL;DR: Small geometric alterations of the aft portion of the fuselage using CDISC has been shown to marginally increase the benefit from boundary-layer ingestion further, resulting in an 8.7% reduction in power requirements for cruise, as well as a drag reduction of approximately twelve counts over the baseline geometry.
Abstract: The present paper examines potential propulsive and aerodynamic benefits of integrating a Boundary-Layer Ingestion (BLI) propulsion system into the Common Research Model (CRM) geometry and the NASA Tetrahedral Unstructured Software System (TetrUSS). The Numerical Propulsion System Simulation (NPSS) environment is used to generate engine conditions for Computational Fluid Dynamics (CFD) analyses. Improvements to the BLI geometry are made using the Constrained Direct Iterative Surface Curvature (CDISC) design method. Potential benefits of the BLI system relating to cruise propulsive power are quantified using a power balance method, and a comparison to the baseline case is made. Iterations of the BLI geometric design are shown, and improvements between subsequent BLI designs are presented. Simulations are conducted for a cruise flight condition of Mach 0.85 at an altitude of 38,500 feet, with Reynolds number of 40 million based on mean aerodynamic chord and an angle of attack of 2° for all geometries. Results indicate an 8% reduction in engine power requirements at cruise for the BLI configuration compared to the baseline geometry. Small geometric alterations of the aft portion of the fuselage using CDISC has been shown to marginally increase the benefit from boundary-layer ingestion further, resulting in an 8.7% reduction in power requirements for cruise, as well as a drag reduction of approximately twelve counts over the baseline geometry.
TL;DR: This study presents an aeroelastic wing shaping control concept for distributed propulsion aircraft that can be used to re-twist wing flexibility by leveraging wing flexibility.
Abstract: This study presents an aeroelastic wing shaping control concept for distributed propulsion aircraft. By leveraging wing flexibility, wing-mounted distributed propulsion can be used to re-twist wing shapes in-flight to improve aerodynamic efficiency. A multidisciplinary approach is used to develop an aero-propulsive-elastic model of a highly flexible wing distributed propulsion transport aircraft. The conceptual model is used to evaluate the aerodynamic benefit of the distributed propulsion aircraft. The initial conceptual analysis shows that an improvement in the aerodynamic efficiency quantity of lift-to-drag ratio L/D is possible with the proposed aeroelastic wing shaping control for distributed propulsion aircraft. Two concepts are studied: single-generator configuration and dual-generator configuration with four propulsors per wing. The baseline aircraft model is NASA Generic Transport Model. A fan performance analysis is developed for propulsion sizing. Cruise performance analysis is conducted to evaluate the potential improvement in the cruise range for the configurations under study. A flutter analysis is performed to address the potential flutter issue as the propulsors are placed toward the wing tip which would cause a reduction in the wing natural frequencies. Flight control considerations are addressed in the context of the engine-out requirement, yaw and roll controls, and yaw damping augmentation using differential thrust.
TL;DR: An investigation into an aerodynamic optimization benchmark case that exhibits multimodality is presented using a global optimization approach.
Abstract: An investigation into an aerodynamic optimization benchmark case that exhibits multimodality is presented using a global optimization approach. The recently suggested case 6 of the AIAA Aerodynamic...
TL;DR: In this article, a strategy for predicting high-lift aerodynamic flows is presented that employs laminar-turbulent transition modeling, based on amplification factor transport, coupled with a hybrid Reynolds-averag...
Abstract: A strategy for predicting high-lift aerodynamic flows is presented that employs laminar–turbulent transition modeling, based on amplification factor transport, coupled with a hybrid Reynolds-averag...
TL;DR: In this paper, a new breakup criterion is proposed for droplets subject to the flowfield generated by an incoming airfoil (that is, the criterion should be applied only to this type of aerodynamics).
Abstract: A new breakup criterion is proposed in this paper for droplets subject to the flowfield generated by an incoming airfoil (that is, the criterion should be applied only to this type of aerodynamics ...
TL;DR: An adaptive integral backstepping trajectory control is designed from the underactuated airship nonlinear dynamics model and the closed-loop trajectory control system is proven to be globally asymptotically stable.
Abstract: This paper deals with trajectory tracking control for an underactuated stratospheric airship in the presence of model uncertainties and external disturbances. An adaptive integral backstepping trajectory control is designed from the underactuated airship nonlinear dynamics model. The proposed controller has a two-level structure. A low-level controller based on nonlinear adaptive integral backstepping method stabilizes the attitude and velocity of the airship, whereas a high-level controller performs guidance and trajectory tracking task. Two underactuated cases of zero lateral control force and zero roll moment input are studied. Meanwhile a control allocation component based on active set with weight least square algorithm is put into the low-level controller, to find the optimal control surfaces and thrust inputs under constraints of actuator saturation. By using Lyapunov theory the closed-loop trajectory control system is proven to be globally asymptotically stable. Finally, simulation results show th...
TL;DR: This paper focuses on the use of an unsteady high-fidelity aerodynamic reduced-order model combined with successive transformations that allows for an economical way of using high- fidelity aerodynamics in the optimization process.
Abstract: Structural optimization with a flutter constraint for a vehicle designed to fly in the transonic regime is a particularly difficult task. In this speed range, the flutter boundary is very sensitive...
TL;DR: The paper presents an experimental study, conducted by the Israel Air Force, aimed at the assessment of several advanced flutter flight-test techniques that are designed to improve the efficiency of the aircraft’s flutter control system.
Abstract: The paper presents an experimental study, conducted by the Israel Air Force, aimed at the assessment of several advanced flutter flight-test techniques that are designed to improve the efficiency a...
TL;DR: This paper presents a multidisciplinary design optimization framework applied to the development of unmanned aerial vehicles with a focus on radar signature and sensor performance requirements with a aim to provide real-time information about the vehicle’s aerodynamic performance.
Abstract: This paper presents a multidisciplinary design optimization framework applied to the development of unmanned aerial vehicles with a focus on radar signature and sensor performance requirements whil ...
TL;DR: In this paper, the authors examined hexacopter performance in hover and forward flight with single rotor failure with a classical configuration (adjacent rotors spinning in opposite directions) and an alternate config...
Abstract: This study examines hexacopter performance in hover and forward flight with single rotor failure. A classical configuration (adjacent rotors spinning in opposite directions) and an alternate config...
TL;DR: In this paper, a vortex-based approach is employed to predict the downwash and outwash of a tandem rotor in ground effect and provide an understanding of its wake, and the aerodynamic loads of the blades are represen...
Abstract: A vortex-based approach is employed to predict the downwash and outwash of a tandem rotor in ground effect and provide an understanding of its wake. The aerodynamic loads of the blades are represen...
TL;DR: In this article, the authors presented a concept of a multicopter that can be reconfigured between a quadcopter, hexacopter, octocopter, and decacopter.
Abstract: This paper presents a concept of a multicopter that can be reconfigured between a quadcopter, hexacopter, octocopter, and decacopter. The controls for each of the configurations are identified, and for the configurations with control redundancy, the power optimal controls are presented. A dynamic simulation model is implemented and used to compare the various configurations. The maximum useful weights of the octocopter, hexacopter, and quadcopter were 76.5%, 53.1%, and 29.7% that of the decacopter, respectively. Over a range of useful weights, the decacopter required the least power when the useful weight was greater than around 23% of its maximum, due to lower induced and profile power requirements of the lighter-loaded, slower-spinning rotors. At lower useful weights, smaller configurations required less power due to their lower empty weight. Increasing the number of rotors increased the maximum hover endurance, cruise endurance, and maximum range. Maximum moments and accelerations produced by each airc...
TL;DR: The aerospace industry’s current trend towards novel or More Electric architectures results in some unique challenges for designers due to both the scarcity or absence of historical data and a pote...
Abstract: The aerospace industry’s current trend towards novel or More Electric architectures results in some unique challenges for designers due to both the scarcity or absence of historical data and a pote...
TL;DR: The objective of this paper is to understand roles of abdominal motion in the pitch stability of flapping flights of butterflies numerically, and a two-dimensional butterfly model has thoracic pitc...
Abstract: The objective of this paper is to understand roles of abdominal motion in the pitch stability of flapping flights of butterflies numerically, and a two-dimensional butterfly model has thoracic pitc...
TL;DR: Results from the Sixth AIAA Computational Fluid Dynamics Drag Prediction Workshop: Case 1 Code Verification are presented, which is for the turbulent flow over a two-dimensional NACA 0012 flow.
Abstract: Results from the Sixth AIAA CFD Drag Prediction Workshop (DPW-VI), Case 1 Code Verification are presented. This test case is for the turbulent flow over a 2D NACA 0012 airfoil using Reynolds-Averaged Navier-Stokes (RANS) turbulence models. A numerical benchmark solution is available for the standard Spalart-Allmaras (SA) turbulence model that can be used for code verification purposes, i.e., to verify that the numerical algorithms employed are consistent and that there are no programming mistakes in the software. For the Case 1 code verification study, there were 31 data submissions from 16 teams: 23 with the SA model (using various versions), 4 with the k-omega SST model (two variants), and one each with k-kl, k-epsilon, an explicit algebraic Reynolds stress model, and the lattice Boltzmann method (LBM) with very large eddy simulation (VLES). Various grid types were employed including structured, unstructured, Cartesian, and adapted grids. The benchmark numerical solution was deemed to be the correct solution for the 21 submissions with the standard SA model, the SA-noft2 variant (without the ft2 term), and the SA-neg variant (designed to avoid nonphysical transient states in discrete settings). While many of these 21 submissions did demonstrate first-order convergence on the finer meshes, others showed either nonconvergent solutions in terms of the aerodynamic forces and moments or converged to the wrong answer. Results for this case highlight the continuing need for rigorous code verification to be conducted as a prerequisite for design, model validation, and analysis studies.
TL;DR: In this paper, an algorithm that integrates Karhunen-Loeve expansion (KLE), nonlinear finite element method (NFEM), and a sampling technique to quantify the uncertainty is proposed to carry out random vibration a
Abstract: An algorithm that integrates Karhunen-Loeve expansion (KLE), nonlinear finite element method (NFEM), and a sampling technique to quantify the uncertainty is proposed to carry out random vibration a