Static Aeroelasticity Research Articles

High-fidelity fluid-structure interaction applied to static aeroelasticity in transonic flows

Transonic flows at high Reynolds numbers can lead to high dynamic pressures and, consequently, to aerostructural deflections of aircraft structures. This study aims to develop and validate a high-fidelity static aeroelastic analysis environment that is efficient and that can be used in an industrial setting. The aerodynamics is represented by numerical solutions of the Reynolds-averaged Navier-Stokes equations with appropriate turbulence closures. The load transfer process uses finite element shape functions in order to distribute the aerodynamic loads into the structural discretization. The structural analysis employs a modal basis approach, and a wingtip deflection convergence study is performed to find an adequate modal basis size. Radial basis functions are used for the fluid mesh displacement, and the influence of the support radius is evaluated to determine the optimal values relative to the wing mean aerodynamic chord. The capability is tested using the static aeroelastic benchmarks of the High Reynolds Aerostructural Dynamics Project (HIRENASD) and NASA's Common Research Model (CRM). The static aeroelastic results demonstrate robustness and consistency for the aerodynamic coefficients, pressure distributions, and structural deflection predictions at different normalized dynamic pressure values and grid refinement levels.

Effects of steady-state fluid-structure interactions on air-supported membrane structures subjected to wind actions

With the perspective of static aeroelasticity, steady-state influences of fluid-structure interaction (FSI) on wind loads and responses of rectangular-planed air-supported membrane structure (ASMS) are investigated in this study. Steady-state FSI simulations are performed by coupling Reynolds-averaged computational fluid dynamics solving wind loads and static finite element analysis solving structural deformations. The feasibility of these simulations is validated with wind tunnel tests concerning time-averaged results. In contrast to analysis without static aeroelasticity, significant variations in wind pressure distributions and amplifications on structural wind responses due to steady-state FSI effects are observed. Subsequently, influencing factors and mechanisms of steady-state FSI effects are analyzed. These time-averaged effects are more significant with the increasing magnitude of structural wind actions, lower internal pressures and less membrane tensile stiffness. Though unlikely to induce irreversible effects as shell structures, the buckling of ASMS can make steady-state FSI more pronounced because of the coupling between stronger flow separation and larger membrane deformations. Accompanied with steady-state FSI, such buckling effect usually contributes to varying locations of the structural maximum responses and noticeable increases in response amplification factors, which deserves attentions in practice. Practically, it is realizable to evaluate these steady-state FSI effects above with simulations because of the much lower computational cost and reliable accuracy.

Fast unsteady method for non-linear aeroelastic responses of flexible aircraft wings encountering wind gusts

Given the current context of changes in aeronautics to reduce emissions, it is also necessary to modernise the computation methods to anticipate future cases where disciplines which are now calculated separately (i.e. manoeuvers and gusts) should be computed at the same time including flexible effects and using a time-domain approach. In this work, a static aeroelasticity formulation is adapted to compute wind gust loads. This static method uses aerodynamic matrices to calculate an effective angle of attack (used to recover the local pressure coefficients) from a structural deformation. The approach has been to define this deformation including unsteady effects influence in order to use the same formulation as the static case. Three gust cases (two unsteady and one quasi-steady) have been tested in a rectangular wing, and the proposed method has been compared to the aeroelastic high-fidelity solution and to an uncorrected version of the Doublet Lattice Method (Nastran Solution 146). The proposed solution benefits from the use of the lookup tables to accurately estimate the peak lift coefficient value (maximum error of 6.7%) at least 2.5 times faster than the Doublet Lattice Method. Nevertheless, using a limited model with only two degrees of freedom prevents the proposed method from capturing complex dynamics coming from highly unsteady gust excitation or from aerodynamic instabilities.

Static aeroelasticity analysis of a rotor blade using a Gauss-Seidel fluid-structure interaction method

The present study introduces a Gauss-Seidel fluid-structure interaction (FSI) method including the flow solver, structural statics solver and a fast data transfer technique, for the research of structural deformation and flow field variation of rotor blades under the combined influence of steady aerodynamic and centrifugal forces. The FSI method is illustrated and validated by the static aeroelasticity analysis of a transonic compressor rotor blade, NASA Rotor 37. An improved local interpolation with data reduction (LIWDR) algorithm is introduced for fast data transfer on the fluid-solid interface of blade. The results of FSI calculation of NASA Rotor 37 show that when compared with the radial basis function (RBF) based interpolation algorithm, LIWDR meets the interpolation accuracy requirements, while the calculation cost can be greatly improved. The data transmission time is only about 1% of that of RBF. Moreover, the iteration step of steady flow computation within one single FSI has little impact on the converged aerodynamic and structural results. The aerodynamic load-caused deformation accounts for nearly 50% of the total. The effects of blade deformation on the variations of aerodynamic performance are given, demonstrating that when static aeroelasticity is taken into account, the choke mass flow rate increases and the peak adiabatic efficiency slightly decreases. The impact mechanisms on performance variations are presented in detail.

Static aeroelasticity of the propulsion system of ion propulsion unmanned aerial vehicles

“Ionic wind” generators are used as the main propulsion system in ion propulsion unmanned aerial vehicles (UAVs). Owing to the large size and poor stiffness of the electrode array in the propulsion system, the electrode array is prone to deformation under the flight load. In this work, the thrust characteristics and static aeroelastic properties of “ionic wind” propulsion systems were analyzed in detail. The simulation model for an “ionic wind” propulsion system was established by coupling a two-dimensional gas discharge model with a gas dynamics model. The influences of electrode voltage, spacing, size, and shape on the performance of the propulsion system were investigated. The fluid-solid interaction method was used to solve static aeroelastic characteristics under deformation. The aerodynamic and thrust performances of the elastic state and the rigid state were compared. It was found that the operating voltage, the distance between two electrodes, and the emitter radius had greater impacts on the thrust of the propulsion system. The propulsion system had a small contribution to the lift but a large contribution to the drag. In the elastic state, the lift coefficient accounted for 12.2%, and the drag coefficient accounted for 25.8%. Under the action of the downwash airflow from the wing, the propulsion system formed an upward moment around the center of mass, which contributed greatly to the pitching moment derivative of the whole aircraft. In the elastic state, the pitching moment derivative accounted for 29.7%. After elastic deformation, the thrust action point moved upward by 28.7 mm. Hence, the no lift pitching moment is reduced by 0.104 N·m, and the pitching moment coefficient is reduced by 0.014, causing a great impact on the longitudinal trimming of the whole aircraft.

Structure health inspection for aging transport aircraft

Purpose This study aims to present a diagnosis method to inspect the structure health for aging transport aircraft based on the postflight data in severe clear-air turbulence at transonic flight. The purpose of this method development is to assist certificate holder of aircraft maintenance factory as a complementary tool for the structural maintenance program to ensure that the transport aircraft fits airworthiness standards. Design/methodology/approach In this study, the numerical approach to analyze the characteristics of flight dynamic and static aeroelasticity for two four-jet transport aircraft will be presented. One of these two four-jet transport aircraft is an aging one. Another one is used to demonstrate the order of magnitude of the static aeroelastic behaviors. The nonlinear unsteady aerodynamic models are established through flight data mining and the fuzzy-logic modeling technique based on postflight data. The first and second derivatives of flight dynamic and static aeroelastic behaviors, respectively, are then estimated by using these aerodynamic models. Findings Although the highest dynamic pressure of aging aircraft is lower, the highest absolute value of static aeroelastic effects response to the wing of aging aircraft is about 3.05 times larger than normal one; the magnitude variations of angles of attack are similar for both aircrafts; the highest absolute value of the static aeroelastic effects response to the empennage of aging aircraft is about 29.67 times larger than normal one in severe clear-air turbulence. The stabilizer of aging aircraft has irregular deviations with obvious jackscrew assembly problems, as found in this study. Research limitations/implications A lack of the measurement data of vertical wind speed sensor on board to verify the estimated values of damping term is one of the research limitations of this study. This research involved potential problem monitoring of structure health for transport aircraft in different weights, different sizes and different service years. In the future research, one can consider more structural integrity issues for other types of aircraft. Practical implications It can be realized from this study that the structure of aging transport aircraft may have potential safety threat. Therefore, when the airline managed aging transport aircraft, it ought to be conducted comprehensive and in-depth inspections to reduce such safety risks and establish a complete set of safety early warning measures to deal with the potential problem of aircraft aging. Social implications It can be realized that the structure of aging transport aircraft has potential safety threat. The airline managed aging transport aircraft; it should conduct comprehensive and in-depth inspections to reduce safety risks and establish a complete set of safety early warning measures. Originality/value This method can be used to assist airlines to monitor aging transport aircraft as a complementary tool of structural maintenance program to improve aviation safety, operation and operational efficiency.

Fast Nonlinear Static Aeroelasticity Method for High-Aspect-Ratio Wings at Different Mach Regimes

A low-computational-cost method is proposed in this paper to predict steady-state nonlinear aeroelastic response for high-aspect-ratio wings. This fast nonlinear static aeroelasticity method relies on a simple but robust mathematical approach. The work presented in this paper evaluates the accuracy of a nonlinear aerodynamic method on a large range of Mach numbers for a geometry representative of a typical industrial high-aspect-ratio-wing aircraft. The robustness of the method relies on the accurate estimation of the local pressure field based on an aerodynamic database using a local incidence estimated with a vortex lattice method. The database can be filled with flight test, wind tunnel test, or high-fidelity numerical simulation. The structural deformation is provided by a coupled aeroelastic high-fidelity numerical simulation, and so this paper focuses mainly on the development and validation of the aerodynamic model. Then, the flexible coefficients of the wing are compared to the high-fidelity aeroelastic numerical simulations for a set of Mach numbers ranging from subsonic to transonic conditions. The results presented in this paper show that the present method is very accurate for low-Mach-number regimes (error is lower than 1% on lift), and it is also adapted to transonic flow regimes because the error on lift is lower than 5%. For high Mach numbers, the current solution commits larger errors on drag and pitching moment coefficients.

A Modification to the Enhanced Correction Factor Technique for the Subsonic Wing–Body Interference Model

In this work, the enhanced correction factor technique (ECFT) is modified for a subsonic wing–body interference model, which can consider the forces on both the lifting boxes and the body elements of an idealized airplane, termed the advanced ECFT method. A passenger aircraft model is chosen as the simulation model, and the longitudinal static aeroelasticity at the transonic situation for two-degree freedom, including the α (angle of attack) degree and ϕ (angle of horizontal tail) degree, is simulated in this paper. The corresponding CFD results are used to correct the aerodynamic influence coefficients (AIC) matrix, which is then simulated by MSC.NASTRAN. The pressure distribution results of different aircraft components received by the advanced ECFT method indicate that it is suitable for the subsonic wing–body interference model. Compared with the uncorrected linear method and the diagonal corrected method, it is generally more consistent with the CFD/CSD coupling method, not only for the lifting boxes, but also for the body elements. In addition, the aerodynamic derivative results also show good agreement with the flight test data, which solidly verifies the advance ECFT method.

On the Static Aeroelasticity Instability of an Inverted Cantilever Plate with a Crack Under Steady Axial Airflow

On the Static Aeroelasticity Instability of an Inverted Cantilever Plate with a Crack Under Steady Axial Airflow

Effects of Unbalanced Lamination Parameters on the Static Aeroelasticity of a High Aspect Ratio Wing

In this paper, in order to understand the influence of the unbalanced coefficient of composite laminates on the static aeroelasticity of high aspect wings, a series of numerical simulation calculations were carried out, and this work wants to provide some reference for the structural design of aircraft. Considering the influence of geometric nonlinearity, the unidirectional fluid-solid coupling calculation method based on loose coupling is used to control the change of unbalanced coefficient of laminates on the basis of layering angle, layering thickness, and layering region, so as to observe the changes caused to the wings. The relationship between the unbalanced coefficient and the constant thickness layup and the variable thickness layup with 0° and ±45° layup angles was studied, respectively. Then, the layup angle of 90° was added to study the influence of the unbalanced coefficient on the static aeroelasticity of the wing structure with the change of the layup angle and the different choice of layup region. The results show that the deformation is the smallest when the unbalanced coefficient is 0.5, and the deformation trend is evenly distributed along both sides when the unbalanced coefficient is 0.5. When the unbalanced coefficient is changed, adding the 90° layup angle can significantly reduce the overall deformation of the wing and show different sensitivity characteristics to different layup areas. The increase of the unbalanced coefficient makes the chordal displacement gradually change from linear distribution to nonlinear distribution along the spread direction, and the displacement will gradually decrease.

Assessment of flight dynamic and static aeroelastic behaviors for jet transport aircraft subjected to instantaneous high g-loads

PurposeThe purpose of this paper is to present a quick inspection method based on the post-flight data to examine static aeroelastic behavior for transport aircraft subjected to instantaneous high g-loads.Design/methodology/approachIn the present study, the numerical approach of static aeroelasticity and two verified cases will be presented. The non-linear unsteady aerodynamic models are established through flight data mining and the fuzzy-logic modeling of artificial intelligence techniques based on post-flight data. The first and second derivatives of flight dynamic and static aeroelastic behaviors, respectively, are then estimated by using these aerodynamic models.FindingsThe flight dynamic and static aeroelastic behaviors with instantaneous high g-load for the two transports will be analyzed and make a comparison study. The circumstance of turbulence encounter of the new twin-jet is much serious than that of four-jet transport aircraft, but the characteristic of stability and controllability for the new twin-jet is better than those of the four-jet transport aircraft; the new twin-jet transport is also shown to have very small aeroelastic effects. The static aeroelastic behaviors for the two different types can be assessed by using this method.Practical implicationsAs the present study uses the flight data stored in a quick access recorder, an intrusive structural inspection of the post-flight can be avoided. A tentative conclusion is to prove that this method can be adapted to examine the static aeroelastic effects for transport aircraft of different weights, different sizes and different service years in tracking static aeroelastic behavior of existing different types of aircraft. In future research, one can consider to have more issues of other types of aircraft with high composite structure weight.Originality/valueThis method can be used to assist airlines to monitor the variations of flight dynamic and static aeroelastic behaviors as a complementary tool for management to improve aviation safety, operation and operational efficiency.

Numerical analysis of geometrical nonlinear aeroelasticity with CFD/CSD method

Abstract A nonlinear static aeroelastic methodology based on the coupled CFD/CSD approach has been developed to study the geometrical nonlinear aeroelastic behaviors of high-aspect-ratio or multi-material flexible aerial vehicles under aerodynamic loads. The Reynolds-averaged Navier–Stokes solver combined with the three-dimensional finite-element nonlinear solver is used to perform the fluid-structure coupling simulation. The interpolation technique for data transfer between the aerodynamic and structural modules employs radial basis function algorithm as well as dynamic mesh deformation. A high-aspect-ratio structure with multi-material is modeled by the finite element method to investigate the effects of geometrical nonlinearity on the aeroelastic behavior. Numerical simulations of the linear and nonlinear static aeroelasticity were conducted at transonic regime with different angles of attack. By comparing the aeroelastic behaviors of linear and nonlinear structure, it shows that geometrical nonlinearity plays an important role for flexible high-aspect-ratio wings undergoing the large static aeroelastic deformation and should be taken into account in aeroelastic analysis for such structures.

Transonic Static Aeroelastic Numerical Analysis of Flexible Complex Configuration Wing

Diamond back wing is subjected to large deformation while gliding, which significantly changes characteristics of the lift as well as the static stability. For this reason, conventional rigid aircraft assumption cannot meet the requirements of the aerodynamic analysis of such aircrafts for accuracy. In this paper, based on CFD/CSD methods, the static aeroelasticity of a small diameter bomb with diamond back wing was studied. The results showed that static aeroelastic effects cause the slope of lift line to drop by 21% and the aerodynamic centre to move backwards by a 1.5% bomb body length, which will deviate the actual flight performance from the design point, thereby decreasing the cruise efficiency and the cruise range.

Static Aeroelasticity Using High Fidelity Aerodynamics in a Staggered Coupled and ROM Scheme

Current technology in evaluating the aeroelastic behavior of aerospace structures is based on the staggered coupling between structural and low fidelity linearized aerodynamic solvers, which has inherent limitations, although tried and trusted outside the transonic region. These limitations arise from the assumptions in the formulation of linearized aerodynamics and the lower fidelity in the description of the flowfield surrounding the structure. The validity of low fidelity aerodynamics also degrades fast with the deviation from a typical aerodynamic shape due to the inclusion of various control devices, gaps, or discontinuities. As innovative wings tend to become more flexible and also include a variety of morphing devices, it is expected that using low fidelity linearized aerodynamics in aeroelastic analysis will tend to induce higher levels of uncertainty in the results. An obvious solution to these issues is to use high fidelity aerodynamics. However, using high fidelity aerodynamics incurs a very high computational cost. Various formulations of reduced order models have shown promising results in reducing the computational cost. In the present work, the static aeroelastic behavior of three characteristic aeroelastic problems is obtained using both a full three-dimensional staggered coupled scheme and a time domain Volterra series based reduced order model (ROM). The reduced order model’s ability to remain valid for a wide range of dynamic pressures around a specific Mach number (and Reynolds number regime if viscous flow is considered) and the capability to modify structural parameters such as damping ratios and natural frequencies are highlighted.

Effect of ply angle on nonlinear static aeroelasticity of high-aspect-ratio composite wing

In order to reduce the weight and improve aerodynamic characteristics, the new aircraft generally adopts lightweight composite materials and high-aspect-ratio layout. Such the structural layout aircraft will produce large nonlinear aeroelastic deformation under the action of aerodynamic loads. Due to the anisotropy of the composite, the composite ply angle of wing skin has a great influence on the elastic deformation of the high-aspect-ratio wing. In order to study the influence of the ply angle on the nonlinear static aeroelastic wing deformation, based on CFD/CSD unidirectional fluid-solid coupling, the structural deformation and stress of high-aspect-ratio composite wing were numerically solved. The wing deformation along the lift direction was taken as the optimization target. The structure strength was taken as the constraint. The ply angle for the composite skin of the high-aspect-ratio composite wing was optimized by the Screening method. The optimization results show the nonlinear static aeroelastic deformation of the wing in the lift direction is reduced by 39.1 %. The maximum stress of the wing beam and rib is reduced by 39.0 %. The maximum Tsai-Wu failure factor of the wing skin is reduced by 47.1 %.

Influence of Spanwise Load Distribution on Blended-Wing–Body Performance at Transonic Speed

The influence of spanwise load distributions on the overall performance of a blended-wing–body (BWB) model at transonic speed is investigated to understand the tradeoffs between aerodynamic efficiency and wing structure weight. The overall performance improvement is measured by the net weight saving relative to the maximum takeoff weight (). A BWB model based on the reference shape of the Boeing second-generation BWB model is taken as the baseline model. Taking the elliptic and triangular spanwise loading as the two extreme distributions, models with varying spanwise loadings have been designed. High-fidelity Reynolds-averaged Navier–Stokes solutions coupled with an inverse design optimization code considering static aeroelasticity is used in the inverse design process. For the BWB models, shifting the spanwise load from the elliptic design toward the triangular design shows a significant reduction in wing root bending moment compared with the traditional civil transports, thus resulting in significant structural weight savings. A wing root bending moment relief of 19% is obtained for the averaged elliptic–triangular design relative to the elliptic design, whereas the loss in aerodynamic efficiency is only 4.4%. The combined effects result in a net weight saving between 0.63 and 1.86% of .

Numerical Simulation Calculation and Analysis of the Effect of Rocket and Duck Rudder on Its Aerodynamic Characteristics and Flexible Deformation

Based on inertia relief and CFD/CSD two-way coupling methods, the static aeroelasticity numerical simulation of a simply guided rocket with duck rudder actuator has been done, and the influence of duck rudder on aerodynamic characteristics and flexible deformation has been analyzed. Firstly, the lift, drag force and pitch moment coefficients, etc. had been calculated by using CFD method based on SST k-ω turbulence model, the error was less than 10 percent compared with the experimential data, and it verified the accuracy of fluid domain numerical method. Then, the two-way fluid-structure interaction simulation on the rocket and the contrastive analysis were done based on ANSYS Workbench multi-physics coupling simulation platform. The results show that duck rudder has a larger influence on rocket aerodynamic characteristics, by analysing the rocket aerodynamic coefficients under the conditions of without duck rudder, 0° rudder angle and 10° rudder angle, and it shows that the lift force and pitch moment coefficients change 5 to 30 percent with or without duck rudder and angle. Considering the influence of flexible deformation on aerodynamic coefficients, the flexible deformation has a more influence on the lift force and pitch moment coefficients, it reflects that the flexible deformation leads to the lift force coefficients smaller and pitch moment coefficients absolute value smaller, the maximum influence can reach to 5 to 10 percent. Meanwhile, the results show that the maximum deformation of rocket occurred in the middle of the rocket body, and the maximum equivalent stress occurred in the empennage of the rocket. Therefore, in the design of simply guided rockets, it’s very important to consider the influence of duck rudder on the aerodynamic characteristics and flexible deformation.

Aerodynamic and structural optimization of wind turbine blade with static aeroelastic effects

Abstract With the increasing size of wind turbine blade, the aeroelastic analysis becomes an essential step in the blade design process. The scope of this paper is to investigate the static aeroelastic effects between the fluid–structure interaction and improve the blade performances. First, the rigid and flexible blades are used to analyze the effects of static aeroelasticity on the blade aerodynamic and structural performances through a blade element momentum model coupled with 3D finite element analysis model. Based on this, a multi-objective aerodynamic and structural optimization method is proposed aiming at increasing the annual energy production and reducing blade mass, key parameters of the blade are employed as design variables, and various design requirements including strain, deflection, vibration and buckling limits are considered as constraints. Finally, a commercial 1.5 MW wind turbine blade is applied as a case study, and the optimization results show great improvements for the aerodynamic and structural performances of the blade.

Geometrically exact vortex lattice and panel methods in static aeroelasticity of very flexible wing

Geometrically exact vortex lattice method and panel method are presented in this paper to deal with aerodynamic load computation for geometrically nonlinear static aeroelastic problems. They are combined with geometrically nonlinear finite element method through surface spline interpolation in the loosely-coupled iteration. From the perspective of theoretical research, both vortex lattice method and panel method are based on the full potential equation and able to model the deflection and twist of the wing, while vortex lattice method is based on the thin airfoil theory, and panel method is suitable for thick wings. Although the potential flow equation is linear, the introduction of geometrically exact boundary conditions makes it significantly different from the linear aeroelastic analysis. The numerical results of a high aspect ratio wing are provided to declare the influence of large deformation on nonlinear static aeroelastic computation compared with linear analysis. Aeroelastic analyses based on geometrically exact vortex lattice method and panel method are also compared with the results of computational fluid dynamics/computational structural dynamics coupling method and the wind tunnel test data. The nonlinear static aeroelastic analysis agrees with the measurement even in considerably large deformation situations.

Static aeroelastic models with integrated stiffness-contributing shell structures built by additive manufacturing

The wind tunnel test of static aeroelastics is a basic method to study the static aeroelastic phenomena of aircraft and other similar structures. As the test objects, the static models need to meet similar requirements, such as geometric similarity and stiffness similarity. The traditional models adopt a spar-frame-skin hybrid structure. The multiple frame segments (skins) of the models are separated from each other, and it is difficult to ensure the geometrical similarity of the aerodynamic shapes of the models during the tests. The overall stiffness of the models with this structure is borne by the metal spars, which makes it difficult to design and manufacture the models. Replacing the segmented frame/skins in the hybrid structure, an integrated shell structure made of additive manufacturing technology (AM) that contributes partial stiffness is proposed in this paper. Based on the structure, a static aeroelastic model is designed in two phases: the similarity design and stiffness design. The stiffness design is formulated as a constrained single-objective optimization problem, and the gradient-based optimization algorithm is adopted to implement the optimization to obtained structural dimensions of the model in the hybrid structure. The errors of the stiffness design are checked and the contribution of integrated shell to the overall stiffness is discussed. A large-aspect-ratio aircraft is chosen as the prototype and a static aeroelastic model with the integrated resin shell is designed, calibrated, and tested in this paper. The results show that the static aeroelastic model with the proposed AM integrated shell is feasible and can be used to study the static aeroelastics reliably and efficiently.