Rafael Castro-Triguero, Enrique Garcia-Macias, Erick Saavedra Flores, M.I. Friswell and Rafael Gallego
The purpose of this paper is to capture the actual structural behavior of the longest timber footbridge in Spain by means of a multi-scale model updating approach in conjunction…
Abstract
Purpose
The purpose of this paper is to capture the actual structural behavior of the longest timber footbridge in Spain by means of a multi-scale model updating approach in conjunction with ambient vibration tests.
Design/methodology/approach
In a first stage, a numerical pre-test analysis of the full bridge is performed, using standard beam-type finite elements with isotropic material properties. This approach offers a first structural model in which optimal sensor placement (OSP) methodologies are applied to improve the system identification process. In particular, the effective independence (EFI) method is used to determine the optimal locations of a set of sensors. Ambient vibration tests are conducted to determine experimentally the modal characteristics of the structure. The identified modal parameters are compared with those values obtained from this preliminary model. To improve the accuracy of the numerical predictions, the material response is modeled by means of a homogenization-based multi-scale computational approach. In a second stage, the structure is modeled by means of three-dimensional solid elements with the above material definition, capturing realistically the full orthotropic mechanical properties of wood. A genetic algorithm (GA) technique is adopted to calibrate the micromechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally.
Findings
An overall good agreement is found between the results of the updated numerical simulations and the corresponding experimental measurements. The longitudinal and transverse Young's moduli, sliding and rolling shear moduli, density and natural frequencies are computed by the present approach. The obtained results reveal the potential predictive capabilities of the present GA/multi-scale/experimental approach to capture accurately the actual behavior of complex materials and structures.
Originality/value
The uniqueness and importance of this structure leads to an intensive study of its structural behavior. Ambient vibration tests are carried out under environmental excitation. Extraction of modal parameters is obtained from output-only experimental data. The EFI methodology is applied for the OSP on a large-scale structure. Information coming from several length scales, from sub-micrometer dimensions to macroscopic scales, is included in the material definition. The strong differences found between the stiffness along the longitudinal and transverse directions of wood lumbers are incorporated in the structural model. A multi-scale model updating approach is carried out by means of a GA technique to calibrate the micromechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally.
Details
Keywords
Many analysis and design problems in engineering and science involve uncertainty to varying degrees. This paper is concerned with the structural vibration problem involving…
Abstract
Purpose
Many analysis and design problems in engineering and science involve uncertainty to varying degrees. This paper is concerned with the structural vibration problem involving uncertain material or geometric parameters, specified as fuzzy parameters. The requirement is to propagate the parameter uncertainty to the eigenvalues of the structure, specified as fuzzy eigenvalues. However, the usual approach is to transform the fuzzy problem into several interval eigenvalue problems by using the α-cuts method. Solving the interval problem as a generalized interval eigenvalue problem in interval mathematics will produce conservative bounds on the eigenvalues. The purpose of this paper is to investigate strategies to efficiently solve the fuzzy eigenvalue problem.
Design/methodology/approach
Based on the fundamental perturbation principle and vertex theory, an efficient perturbation method is proposed, that gives the exact extrema of the first-order deviation of the structural eigenvalue. The fuzzy eigenvalue approach has also been improved by reusing the interval analysis results from previous α-cuts.
Findings
The proposed method was demonstrated on a simple cantilever beam with a pinned support, and produced very accurate fuzzy eigenvalues. The approach was also demonstrated on the model of a highway bridge with a large number of degrees of freedom.
Originality/value
This proposed Vertex-Perturbation method is more efficient than the standard perturbation method, and more general than interval arithmetic methods requiring the non-negative decomposition of the mass and stiffness matrices. The new increment method produces highly accurate solutions, even when the membership function for the fuzzy eigenvalues is complex.
Details
Keywords
Emre Ozbek, Selcuk Ekici and Tahir Hikmet Karakoç
The current research conducts a comprehensive review on FishBAC (fishbone active camber morphing wing surfaces) for researchers and scientists and sheds light on challenges and…
Abstract
Purpose
The current research conducts a comprehensive review on FishBAC (fishbone active camber morphing wing surfaces) for researchers and scientists and sheds light on challenges and opportunities of FishBAC development.
Design/methodology/approach
This is a review article and this study reviews previous research on FishBAC.
Findings
The current FishBAC applications could be upgraded into more efficient designs in materials, design and mechanisms with more perspectives involved. Then, this promising branch of morphing surface design could be integrated with rotor blades, unmanned aerial vehicle wings, general aviation aircraft surfaces and so on.
Research limitations/implications
This is a review article.
Practical implications
The contributions of the study are summarized as follows: to provide an overview of FishBAC research; to compare various approaches and trends in FishBAC designs; to address the research gap in the roadmap for FishBAC design; and to discuss the challenges and opportunities of FishBAC development.
Originality/value
To the best of the authors’ knowledge, this is the first review on a promising morphing method and an alternative for conventional flaps and ailerons.
Details
Keywords
Damage of a structure affects its stiffness properties and induces a shift in the free frequency spectrum. In the paper, an additional parameter is introduced, such as…
Abstract
Damage of a structure affects its stiffness properties and induces a shift in the free frequency spectrum. In the paper, an additional parameter is introduced, such as concentrated elastic or rigid support and mass. The evolution of natural frequencies is analyzed for varying parameter values with respect to damage location. This frequency variation is used in assessing the location and magnitude of damage by introducing the damage indices or by solving the identification problem requiring the minimization of the parameter dependent distance functional. The first part of the paper is concerned with the sensitivity analysis of damage indices with respect to support or mass location. The second part deals with the identification problem for which the specific examples are treated.
Details
Keywords
Jacques Abou Khalil, César Jiménez Navarro, Rami El Jeaid, Abderahmane Marouf, Rajaa El Akoury, Yannick Hoarau, Jean-François Rouchon and Marianna Braza
This study aims to investigate the morphing concepts able to manipulate the dynamics of the downstream unsteadiness in the separated shear layers and, in the wake, be able to…
Abstract
Purpose
This study aims to investigate the morphing concepts able to manipulate the dynamics of the downstream unsteadiness in the separated shear layers and, in the wake, be able to modify the upstream shock–boundary layer interaction (SBLI) around an A320 morphing prototype to control these instabilities, with emphasis to the attenuation or even suppression of the transonic buffet. The modification of the aerodynamic performances according to a large parametric study carried out at Reynolds number of 4.5 × 106, Mach number of 0.78 and various angles of attack in the range of (0, 2.4)° according to two morphing concepts (travelling waves and trailing edge vibration) are discussed, and the final benefits in aerodynamic performance increase are evaluated.
Design/methodology/approach
This article examines through high fidelity (Hi-Fi) numerical simulation the effects of the trailing edge (TE) actuation and of travelling waves along a specific area of the suction side starting from practically the most downstream position of the shock wave motion according to the buffet and extending up to nearly the TE. The present paper studies through spectral analysis the coherent structures development in the near wake and the comparison of the aerodynamic forces to the non-actuated case. Thus, the physical mechanisms of the morphing leading to the increase of the lift-to-drag ratio and the drag and noise sources reduction are identified.
Findings
This study investigates the influence of shear-layer and near-wake vortices on the SBLI around an A320 aerofoil and attenuation of the related instabilities thanks to novel morphing: travelling waves generated along the suction side and trailing-edge vibration. A drag reduction of 14% and a lift-to-drag increase in the order of 8% are obtained. The morphing has shown a lift increase in the range of (1.8, 2.5)% for angle of attack of 1.8° and 2.4°, where a significant lift increase of 7.7% is obtained for the angle of incidence of 0° with a drag reduction of 3.66% yielding an aerodynamic efficiency of 11.8%.
Originality/value
This paper presents results of morphing A320 aerofoil, with a chord of 70cm and subjected to two actuation kinds, original in the state of the art at M = 0.78 and Re = 4.5 million. These Hi-Fi simulations are rather rare; a majority of existing ones concern smaller dimensions. This study showed for the first time a modified buffet mode, displaying periodic high-lift “plateaus” interspersed by shorter lift-decrease intervals. Through trailing-edge vibration, this pattern is modified towards a sinusoidal-like buffet, with a considerable amplitude decrease. Lock-in of buffet frequency to the actuation is obtained, leading to this amplitude reduction and a drastic aerodynamic performance increase.
Details
Keywords
Chawki Abdessemed, Yufeng Yao, Abdessalem Bouferrouk and Pritesh Narayan
The purpose of this paper is to use dynamic meshing to perform CFD analyses of a NACA 0012 airfoil fitted with a morphing trailing edge (TE) flap when it undergoes static and…
Abstract
Purpose
The purpose of this paper is to use dynamic meshing to perform CFD analyses of a NACA 0012 airfoil fitted with a morphing trailing edge (TE) flap when it undergoes static and time-dependent morphing. The steady CFD predictions of the original and morphing airfoils are validated against published data. The study also investigates an airfoil with a hinged TE flap for aerodynamic performance comparison. The study further extends to an unsteady CFD analysis of a dynamically morphing TE flap for proof-of-concept and also to realise its potential for future applications.
Design/methodology/approach
An existing parametrization method was modified and implemented in a user-defined function (UDF) to perform dynamic meshing which is essential for morphing airfoil unsteady simulations. The results from the deformed mesh were verified to ensure the validity of the adopted mesh deformation method. ANSYS Fluent software was used to perform steady and unsteady analysis and the results were compared with computational predictions.
Findings
Steady computational results are in good agreement with those from OpenFOAM for a non-morphing airfoil and for a morphed airfoil with a maximum TE deflection equal to 5 per cent of the chord. The results obtained by ANSYS Fluent show that an average of 6.5 per cent increase in lift-to-drag ratio is achieved, compared with a hinged flap airfoil with the same TE deflection. By using dynamic meshing, unsteady transient simulations reveal that the local flow field is influenced by the morphing motion.
Originality/value
An airfoil parametrisation method was modified to introduce time-dependent morphing and used to drive dynamic meshing through an in-house-developed UDF. The morphed airfoil’s superior aerodynamic performance was demonstrated in comparison with traditional hinged TE flap. A methodology was developed to perform unsteady transient analysis of a morphing airfoil at high angles of attack beyond stall and to compare with published data. Unsteady predictions have shown signs of rich flow features, paving the way for further research into the effects of a dynamic flap on the flow physics.
Details
Keywords
Abstract
Purpose
This paper seeks to present a new solution algorithm for updating of finite element models in structural dynamics. A random search method is applied to improving the correlation between the numerical simulation and the measured experimental data.
Design/methodology/approach
Dynamic finite element model updating may be considered as an optimization process. It is solved using modified accelerated random search (MARS) algorithm. The effectiveness of the approach is first tested on benchmark problems. Next, several objective function formulations for dynamic model updating in modal and frequency domains are investigated for numerically simulated vibrating beam. Finally, the algorithm is applied to a real beam‐like structure using measured modal data.
Findings
The MARS algorithm is able to provide very good results in a reduced time even for hard optimization problems. It behaves very well also for the FE dynamic model updating, highly coupled problems. The efficient updating criterion has been proposed and the approach has been validated experimentally.
Research limitations/implications
The method is supposed to be time consuming for large size or complicated objective function problems but the choice of optimization parameters can accelerate the convergence.
Practical implications
The MARS algorithm can be applied to model updating in civil and mechanical engineering.
Originality/value
This paper is the first to apply the MARS algorithm to the problem of FE model updating in dynamics and enables one to obtain very good results. Efficient criteria for model updating have been proposed.
Details
Keywords
Daochun Li, Shijun Guo, Tariq Osman Aburass, Daqing Yang and Jinwu Xiang
The purpose of this study is to develop an active controller of both leading-edge (LE) and trailing-edge (TE) control surfaces for an unmanned air vehicle (UAV) with a composite…
Abstract
Purpose
The purpose of this study is to develop an active controller of both leading-edge (LE) and trailing-edge (TE) control surfaces for an unmanned air vehicle (UAV) with a composite morphing wing.
Design/methodology/approach
Instead of conventional hinged control surfaces, both LE and TE seamless control surfaces were integrated with the wing. Based on the longitudinal state space equation, the root locus plot of the morphing wing aircraft, with a stability augmented system, was constructed. Using the pole placement, the feedback gain matrix for an active control was obtained.
Findings
The aerodynamic benefits of a morphing wing section are compared with a wing of a rigid control surface. However, the 3D morphing wing with a large sweptback angle produces a washout negative aeroelastic effect, which causes a significant reduction of the control effectiveness. The results show that the stability augmentation system can significantly improve the longitudinal controllability of an aircraft with a morphing wing.
Practical implications
This study is necessary to analyse the effect of a morphing wing on an UAV and perform a comparison with the rigid model.
Originality/value
The control surfaces assignment plan for trim, pitch and roll control was obtained. An active control algorism for the morphing wing was created to satisfy the required stability and control effectiveness by operating the LE and TE control surfaces according to flight conditions. The aeroelastic effect of control derivatives on the morphing aircraft was considered.
Details
Keywords
Witold Artur Klimczyk and Zdobyslaw Jan Goraj
The purpose of this paper is to present a method for analysis and optimization of morphing wing. Moreover, a numerical advantage of morphing airfoil wing, typically assessed in…
Abstract
Purpose
The purpose of this paper is to present a method for analysis and optimization of morphing wing. Moreover, a numerical advantage of morphing airfoil wing, typically assessed in simplified two-dimensional analysis is found using higher fidelity methods.
Design/methodology/approach
Because of multi-point nature of morphing wing optimization, an approach for optimization by analysis is presented. Starting from naïve parametrization, multi-fidelity aerodynamic data are used to construct response surface model. From the model, many significant information are extracted related to parameters effect on objective; hence, design sensitivity and, ultimately, optimal solution can be found.
Findings
The method was tested on benchmark problem, with some easy-to-predict results. All of them were confirmed, along with additional information on morphing trailing edge wings. It was found that wing with morphing trailing edge has around 10 per cent lower drag for the same lift requirement when compared to conventional design.
Practical implications
It is demonstrated that providing a smooth surface on wing gives substantial improvement in multi-purpose aircrafts. Details on how this is achieved are described. The metodology and results presented in current paper can be used in further development of morphing wing.
Originality/value
Most of literature describing morphing airfoil design, optimization or calculations, performs only 2D analysis. Furthermore, the comparison is often based on low-fidelity aerodynamic models. This paper uses 3D, multi-fidelity aerodynamic models. The results confirm that this approach reveals information unavailable with simplified models.
Details
Keywords
G.S. Aglietti, S.J.I. Walker and A. Kiley
The purpose of this paper is to assess the suitability of various methods for the reduction of a large finite element model (FEM) of satellites to produce models to be used for…
Abstract
Purpose
The purpose of this paper is to assess the suitability of various methods for the reduction of a large finite element model (FEM) of satellites to produce models to be used for correlation of the FEM with test results. The robustness of the cross‐orthogonality checks (COC) for the correlation process carried out utilizing the reduced model is investigated, showing its dependence on the number of mode shapes used in the reduction process. Finally the paper investigates the improvement in the robustness of the COC that can be achieved utilizing optimality criteria for the selection of the degrees of freedom (DOF) used for the correlation process.
Design/methodology/approach
A Monte Carlo approach has been used to simulate inaccuracies in the mode shapes (analysis and experimental) of a satellite FEM that are compared during the COC. The sensitivity of the COC to the parameters utilized during the reduction process, i.e. mode shapes and DOFs, is then assessed for different levels of inaccuracy in the mode shapes.
Findings
The System Equivalent Expansion Reduction Process (SEREP) has been identified as a particularly suitable method, with the advantage that a SEREP reduced model has the same eigenvalues and eigenvector of the whole system therefore automatically meeting the criteria on the quality of the reduced model. The inclusion of a high number of mode shapes in the reduction process makes the check very sensitive to minor experimental or modelling inaccuracies. Finally it was shown that utilizing optimality criteria in the selection of the DOFs to carry out the correlation can significantly improve the probability of meeting the COC criteria.
Research limitations/implications
This work is based on the FEM of the satellite Aeolus, and therefore the numerical values obtained in this study are specific for this application. However, this model represents a typical satellite FEM and therefore the trends identified in this work are expected to be generally valid for this type of structure.
Practical implications
The correlation of satellite FEM with test results involves a substantial effort, and it is crucial to avoid failures of the COC due to numerical issues rather than real model inaccuracies. This work shows also how an inappropriate choice of reduction parameters can lead to failure of the COC in cases when there are only very minor differences (e.g. due to minor amount of noise in the results) between analytical and test results. Vice versa, the work also shows how the robustness of the reduced model can be improved.
Originality/value
The paper shows how the robustness of the correlation process for a satellite FEM carried out utilising a SEREP reduced model needed to be investigated, to demonstrate the suitability of this method to reduce large FEM of satellites.