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1 – 10 of 999Farid Shahmiri and Fariborz Saghafi
The purpose of this paper is to examine the cross‐coupled responses of a coupled rotor‐fuselage flight dynamic simulation model, including a finite‐state inflow aerodynamics and a…
Abstract
Purpose
The purpose of this paper is to examine the cross‐coupled responses of a coupled rotor‐fuselage flight dynamic simulation model, including a finite‐state inflow aerodynamics and a coupled flap‐lag and torsion flexible blade structure.
Design/methodology/approach
The methodology is laid out based on model development for an articulated main rotor, using the theories of aeroelastisity, finite element and finite‐state inflow formulation. The finite‐state inflow formulation is based on a 3D unsteady Euler‐based concepts presented in the time domain. The most advantages of the model are the capability of modeling dynamic wake effects, tip losses and skewed wake aerodynamics. This is, in fact, a special type of the inflow model relating inflow states, to circulatory blade loadings through a set of first‐order differential equations. A non‐iterative solution of the differential equations has practically altered the model into a simple and direct formulation appending properly to the rest of the helicopter mathematical model. A non‐linear distribution of the induced velocity over the rotor disc is finally obtained by the use of both Legendre polynomials and higher‐harmonic functions. Ultimately, validations of the theoretical results show that the on‐axis response, direct reaction to the pilot input, has a good accuracy both quantitatively and qualitatively against flight test data, and the off‐axis response, cross‐coupled or indirect reaction to the pilot input are improved by this approach of modeling.
Findings
Improvements in dynamic prediction of both trim control settings and dynamic cross‐coupled responses of helicopter to pilot inputs are observed.
Research limitations/implications
Further work is required for investigation of the augmented finite state inflow model, including the wake rotation correction factors to describe helicopter maneuvering flight characteristics.
Practical implications
The results of this work support the future researches on design and development of advanced flight control system, incorporating a high bandwidth with low‐phase delay to control inputs and also high levels of dynamic stability within minimal controls cross coupling.
Originality/value
This paper provides detailed characteristics on the mathematical integration problems associated with the advanced helicopter flight dynamics research.
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Shuya Li, Zhengqi Gu, Taiming Huang, Zhen Chen and Jun Liu
The purpose of this paper is to develop a two-way coupling approach for investigating the aerodynamic stability of vehicles under the combined effect of crosswind and road…
Abstract
Purpose
The purpose of this paper is to develop a two-way coupling approach for investigating the aerodynamic stability of vehicles under the combined effect of crosswind and road adhesion.
Design/methodology/approach
The author develops a new two-way coupling approach, which couples large eddy simulation with multi-body dynamics (MBD), to investigate the crosswind stability on three different adhesion roads: ideal road, dry road and wet road. The comparison of the results obtained using the traditional one-way coupling approach and the new two-way coupling approach is also done to assess the necessity to use the proposed coupling technique on low adhesion roads, and the combined effect of crosswind and road adhesion on vehicle stability is analyzed.
Findings
The results suggest that the lower the road adhesion is, the larger deviation a vehicle generates, the more necessary to conduct the two-way coupling simulation. The combined effect of the crosswind and road adhesion can decrease a vehicle’s lateral motion on a high adhesion road after the disappearing of the crosswind. But on a low adhesion road, the vehicle tends to be unstable for its large head wind angle. The vehicle stability in crosswind on a low adhesion road needs more attention, and the investigation should consider the coupling of aerodynamics and vehicle dynamics and the combined effect of crosswind and road adhesion.
Originality/value
Developing a new two-way coupling approach which can capture the complex vehicle structures and the road adhesion with MBD model and the completed fluid filed structure with CFD model. The present study might be the first study considering the coupling of crosswind and low adhesion road. The proposed two-way coupling approach will be useful for researchers who study vehicle crosswind stability.
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Javad Masrour, Seyed Hossein Sadati and Morteza Shahravi
This study aims to simulate gust effects on the aeroelastic behavior of a flexible aircraft. The dynamic response of the system for different discreet gust excitations is obtained…
Abstract
Purpose
This study aims to simulate gust effects on the aeroelastic behavior of a flexible aircraft. The dynamic response of the system for different discreet gust excitations is obtained using numerical simulations.
Design/methodology/approach
Coupled dynamics, including rigid and flexible body coordinates, are considered for modeling the dynamic behavior of the aircraft. Wing is considered flexible and other parts are considered rigid. Wing is modeled with nonlinear Euler Bernoulli beam. Moreover, unsteady aerodynamics based on the Wagner function are used for aerodynamic loading, and the results are compared with those of quasi-steady aerodynamics.
Findings
Von Kármán continuous gust is applied to this aircraft. In addition, the discrete “1- cosine” gust with different gust lengths is applied to the aircraft, and the maximum and minimum accelerations are computed. It is shown that the nonlinear modeling of the system represents the actual behavior and causes limit cycle oscillation phenomena.
Originality/value
This methodology can yield a relatively simple dynamic model for high aspect ratio aircrafts to provide insights into the vehicles’ dynamics, which can be available early in the design cycle.
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The purpose of this paper is to demonstrate new design concepts for 24 classes of laminate, which have been derived as part of an ongoing study on the development of a unified…
Abstract
Purpose
The purpose of this paper is to demonstrate new design concepts for 24 classes of laminate, which have been derived as part of an ongoing study on the development of a unified approach to the characterization of coupled laminates. The paper presents a description of each class of coupled laminate.
Design/methodology/approach
The paper gives an overview of the desired performance and requirements of a smart leading edge device, its aerodynamic design for the wind tunnel tests and the structural pre‐design and sizing of the full‐scale leading edge section which will be tested in the wind tunnel.
Findings
Coupled laminates have potential applications in the design of aero‐elastic compliant rotor blades or aircraft wing structures, by introducing tailored extension‐twist and/or shear‐extension coupling at the laminate level; or in the design of thermally activated morphing structures, by exploiting more complex coupling behaviour.
Practical implications
These laminates contain standard cross‐ply and/or angle‐ply combinations, although double angle‐ply laminates are also considered, and correspond to any standard fibre/matrix system with a constant ply thickness throughout.
Originality/value
The vast majority of the laminate described possess coupling behaviour not previously identified in the literature.
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Jing Zhang, Wenwen Kang and Lingyu Yang
Boundary layer ingestion (BLI) is one of the probable noteworthy features of distributed propulsion configuration (DPC). Because of BLI, strong coupling effects are generated…
Abstract
Purpose
Boundary layer ingestion (BLI) is one of the probable noteworthy features of distributed propulsion configuration (DPC). Because of BLI, strong coupling effects are generated between the aerodynamics and propulsion system of aircraft, leading to the specific lift and drag aerodynamic characteristics. This paper aims to propose a model-based comprehensive analysis method to investigate this unique aerodynamic.
Design/methodology/approach
To investigate this unique aerodynamics, a model-based comprehensive analysis method is proposed. This method uses a detailed mathematical model of the distributed propulsion system to provide the essential boundary conditions and guarantee the accuracy of calculation results. Then a synthetic three-dimensional computational model is developed to analyze the effects of BLI on the lift and drag aerodynamic characteristics.
Findings
Subsequently, detailed computational analyses are conducted at different flight states, and the regularities under various flight altitudes and velocities are revealed. Computational results demonstrate that BLI can improve the lift to drag ratio evidently and enable a great performance potentiality.
Practical implications
The general analysis method and useful regularities have reference value to DPC aircraft and other similar aircrafts.
Originality/value
This paper proposed a DPS model-based comprehensive analysis method of BLI benefit on aerodynamics for DPC aircraft, and the unique aerodynamics of this new configuration under various flight altitudes and velocities was revealed.
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Jesús Matesanz-García, Tommaso Piovesan and David G. MacManus
Novel aircraft propulsion configurations require a greater integration of the propulsive system with the airframe. As a consequence of the closer integration of the propulsive…
Abstract
Purpose
Novel aircraft propulsion configurations require a greater integration of the propulsive system with the airframe. As a consequence of the closer integration of the propulsive system, higher levels of flow distortion at the fan face are expected. This distortion will propagate through the fan and penalize the system performance. This will also modify the exhaust design requirements. This paper aims to propose a methodology for the aerodynamic optimization of the exhaust for novel embedded propulsive systems. To model the distortion transfer, a low order throughflow fan model is included.
Design/methodology/approach
As the case study a 2D axisymmetric aft-mounted annular boundary layer ingestion (BLI) propulsor is used. An automated computational fluid dynamics approach is applied with a parametric definition of the design space. A throughflow body force model for the fan is implemented and validated for 2D axisymmetric and 3D flows. A multi-objective optimization based on evolutionary algorithms is used for the exhaust design.
Findings
By the application of the optimization methodology, a maximum benefit of approximately 0.32% of the total aircraft required thrust was observed by the application of compact exhaust designs. Furthermore, for the embedded system, it is observed that the design of the compact exhaust and the nacelle afterbody have a considerable impact on the aerodynamic performance.
Originality/value
This paper presents a novel approach for the exhaust design of embedded propulsive systems in novel aircraft configurations. To the best of the authors’ knowledge, this is the first detailed optimization of the exhaust system on an annular aft-mounted BLI propulsor.
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This research aims to present an aero-propulsive interaction model applied to conceptual aircraft design with distributed electric propulsion (DeP). The developed model includes a…
Abstract
Purpose
This research aims to present an aero-propulsive interaction model applied to conceptual aircraft design with distributed electric propulsion (DeP). The developed model includes a series of electric ducted fans integrated into the wing upper trailing edge, taking into account the effect of boundary layer ingestion (BLI). The developed model aims to estimate the aerodynamic performance of the wing with DeP using an accurate low-order computational model, which can be easily used in the overall aircraft design's optimization process.
Design/methodology/approach
First, the ducted fan aerodynamic performance is investigated using a low-order computational model over a range of angle of attack required for conventional flight based on ducted fan design code program and analytical models. Subsequently, the aero-propulsive coupling with the wing is introduced. The DeP location chordwise is placed at the wing's trailing edge to have the full benefits of the BLI. After that, the propulsion integration process is introduced. The nacelle design's primary function is to minimize the losses due to distortion. Finally, the aerodynamic forces of the overall configuration are estimated based on Athena Vortex Lattice program and the developed ducted fan model.
Findings
The ducted fan model is validated with experimental measurements from the literature. Subsequently, the overall model, the wing with DeP, is validated with experimental measurements and computational fluid dynamics, both from the literature. The results reveal that the currently developed model successfully estimates the aerodynamic performance of DeP located at the wing trailing edge.
Originality/value
The developed model's value is to capture the aero-propulsive coupling accurately and fast enough to execute multiple times in the overall aircraft design's optimization loop without increasing runtime substantially.
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Yang Dang‐guo, Sun Yan, Zhang Zheng‐yu, Wang Chao and Zhu Wei‐jun
The purpose of this paper is to present a novel method to design and manufacture rapid prototyping (RP) lightweight photopolymer‐resin models for wind‐tunnel tests. This method…
Abstract
Purpose
The purpose of this paper is to present a novel method to design and manufacture rapid prototyping (RP) lightweight photopolymer‐resin models for wind‐tunnel tests. This method can ensure the structural configuration similarity considering model deformation under aerodynamic loads.
Design/methodology/approach
Photopolymer‐resin based on RP technique was used to fabricate DLR‐F4 models. Testing in a subsonic and transonic wind tunnel was carried out and the test results were compared to analyze performance predictions.
Findings
RP photopolymer‐resin wind‐tunnel models fabricated by the design methods yielded satisfactory aerodynamic performance. The methods can decrease the model's weight and prevent resonance occurrence among the models, wind‐tunnel, and support system, shorten the processing period, and lead to decrease in manufacturing period and cost.
Research limitations/implications
Stiffness shortage of the thin components, such as wing tip, often leads to deformation occurrence under aerodynamic loads in transonic wind‐tunnel tests, which has significant influence on aerodynamic characteristics of the test models. Therefore, model deformation should be taken into account in the design process.
Originality/value
This design and manufacture method, aerodynamic and structural combination design and structural optimization, can obtain RP lightweight photopolymer‐resin wind‐tunnel models for satisfactory aerodynamic performance, which makes RP techniques more practical for manufacturing transonic wind‐tunnel test models, considering deformation induced by aerodynamic forces such as lift force. The methods also present an inexpensive way to test and evaluate preliminary aircraft designs, in both academia and industry.
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Giovanni Droandi and Giuseppe Gibertini
The purpose of this paper is to present the aerodynamic blade design of a tiltwing aircraft with a multi-objective optimization procedure. The aerodynamic design of tiltrotor…
Abstract
Purpose
The purpose of this paper is to present the aerodynamic blade design of a tiltwing aircraft with a multi-objective optimization procedure. The aerodynamic design of tiltrotor blades is a very challenging task in the project of this type of aircraft.
Design/methodology/approach
Tiltrotor blades have to give good performance both in helicopter and aeroplane modes. According to the design parameters (the chords, the twists and the airfoils along the blade), as the optimization objectives are different from one operating condition to another, the blade is the result of a multi-objective constrained optimization based on a controlled elitist genetic algorithm founded on the NSGA-II algorithm. The optimization process uses a BEMT solver to compute rotor performance. To avoid negative effects due to compressibility losses in aeroplane mode, the blade shape has been refined following the normal Mach number criterion.
Findings
It has been found that the optimized rotor blade gives good performance both in terms of figure of merit and propulsive efficiency if compared with experimental data of existing rotor (ERICA tiltrotor) and propeller (NACA high-speed propeller).
Practical implications
The optimization procedure described in this paper for the design of tiltrotor blades can be efficiently used for the aerodynamic design of helicopter rotors and aircraft propellers of all typology.
Originality/value
In this work, advanced methodologies have been used for the aerodynamics design of a proprotor optimized for an aircraft which belongs to the innovative typology of high-performance tiltwing tiltrotor aircraft.
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Promio Charles F., Raja Samikkannu, Niranjan K. Sura and Shanwaz Mulla
Ground vibration testing (GVT) results can be used as system parameters for predicting flutter, which is essential for aeroelastic clearance. This paper aims to compute GVT-based…
Abstract
Purpose
Ground vibration testing (GVT) results can be used as system parameters for predicting flutter, which is essential for aeroelastic clearance. This paper aims to compute GVT-based flutter in time domain, using unsteady air loads by matrix polynomial approximations.
Design/methodology/approach
The experimental parameters, namely, frequencies and mode shapes are interpolated to build an equivalent finite element model. The unsteady aerodynamic forces extracted from MSC NASTRAN are approximated using matrix polynomial approximations. The system matrices are condensed to the required shaker location points to build an aeroelastic reduced order state space model in SIMULINK.
Findings
The computed aerodynamic forces are successfully reduced to few input locations (optimal) for flutter simulation on unknown structural system (where stiffness and mass are not known) through a case study. It is demonstrated that GVT data and the computed unsteady aerodynamic forces of a system are adequate to represent its aeroelastic behaviour.
Practical implications
Airforce of every nation continuously upgrades its fleet with advanced weapon systems (stores), which demands aeroelastic flutter clearance. As the original equipment manufacturers does not provide the design data (stiffness and mass) to its customers, a new methodology to build an aeroelastic system of unknown aircraft is devised.
Originality/value
A hybrid approach is proposed, involving GVT data to build an aeroelastic state space system, using rationally approximated air loads (matrix polynomial approximations) computed on a virtual FE model for ground flutter simulation.
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