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Gotowa bibliografia na temat „Aerodynamic loads”

Autor: Grafiati

Data publikacji: 4 czerwca 2021

Data aktualizacji: 4 marca 2023

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Artykuły w czasopismach na temat "Aerodynamic loads"

Tomasz Lusiak, Andrej Novak, Martin Bugaj i Radovan Madlenak. "Assessment of Impact of Aerodynamic Loads on the Stability and Control of the Gyrocopter Model". Communications - Scientific letters of the University of Zilina 22, nr 4 (1.10.2020): 63–69. http://dx.doi.org/10.26552/com.c.2020.4.63-69.

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Aerodynamic modelling currently relates to development of mathematical models to describe the aerodynamic forces and moments acting on the aircraft. It is a challenging part of aerodynamics that defines a comprehensive approach to using traditional methods and modern techniques to obtain relevant data. The most complicated task for the aerodynamics and flight dynamics is definition, computation and quantification of the aerodynamic description of an object. This paper presents how to determine the aerodynamic load on a gyrocopter and defines the effect on its stability and control. The first step to solution is to develop simpler approximate aerodynamic model - a model that can be used in analysis of aerodynamic load and can represent the aerodynamic properties of the gyrocopter with an acceptable degree of accuracy. Control and stability are very important parts of aircraft characteristics and therefore those characteristics were analyzed in simulation. Finally, the aerodynamic data outputs are assessed in terms of impact of aerodynamic loads on stability and control of the gyrocopter model.

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Enciu, K., i A. Rosen. "Aerodynamic modelling of fin stabilised underslung loads". Aeronautical Journal 119, nr 1219 (wrzesień 2015): 1073–103. http://dx.doi.org/10.1017/s0001924000011143.

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AbstractBox-like slung loads exhibit periodic yaw response instabilities, while carried externally by a helicopter. When coupled with the slung load longitudinal and lateral pendulum motions, these instabilities result in significant pendulum oscillations of the load. High amplitude oscillations lead in many cases to the limiting of a load’s flight envelope. Using wind tunnel and flight tests, rear mounted fins were previously demonstrated as efficient means for stabilisation of a problematic load. However, the lack of a proper analytical model of the stabilised load’s aerodynamic characteristics, led to a trial and error development process, without an appropriate physical understanding of the stabilisation problem. The present paper describes a method for the aerodynamic modeling of fins stabilised slung loads based on a limited number of simple static wind-tunnel tests. The resulting database is incorporated in a dynamical slung load simulation that shows good agreement with dynamic wind-tunnel tests. The applicability of the proposed method is demonstrated, by the calculation of stabilised loads aerodynamic databases for interim fin inclination angles not covered by tests.

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Perez-Becker, Sebastian, Francesco Papi, Joseph Saverin, David Marten, Alessandro Bianchini i Christian Oliver Paschereit. "Is the Blade Element Momentum theory overestimating wind turbine loads? – An aeroelastic comparison between OpenFAST's AeroDyn and QBlade's Lifting-Line Free Vortex Wake method". Wind Energy Science 5, nr 2 (15.06.2020): 721–43. http://dx.doi.org/10.5194/wes-5-721-2020.

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Abstract. Load calculations play a key role in determining the design loads of different wind turbine components. To obtain the aerodynamic loads for these calculations, the industry relies heavily on the Blade Element Momentum (BEM) theory. BEM methods use several engineering correction models to capture the aerodynamic phenomena present in Design Load Cases (DLCs) with turbulent wind. Because of this, BEM methods can overestimate aerodynamic loads under challenging conditions when compared to higher-order aerodynamic methods – such as the Lifting-Line Free Vortex Wake (LLFVW) method – leading to unnecessarily high design loads and component costs. In this paper, we give a quantitative answer to the question of load overestimation of a particular BEM implementation by comparing the results of aeroelastic load calculations done with the BEM-based OpenFAST code and the QBlade code, which uses a particular implementation of the LLFVW method. We compare extreme and fatigue load predictions from both codes using sixty-six 10 min load simulations of the Danish Technical University (DTU) 10 MW Reference Wind Turbine according to the IEC 61400-1 power production DLC group. Results from both codes show differences in fatigue and extreme load estimations for the considered sensors of the turbine. LLFVW simulations predict 9 % lower lifetime damage equivalent loads (DELs) for the out-of-plane blade root and the tower base fore–aft bending moments compared to BEM simulations. The results also show that lifetime DELs for the yaw-bearing tilt and yaw moments are 3 % and 4 % lower when calculated with the LLFVW code. An ultimate state analysis shows that extreme loads of the blade root out-of-plane bending moment predicted by the LLFVW simulations are 3 % lower than the moments predicted by BEM simulations. For the maximum tower base fore–aft bending moment, the LLFVW simulations predict an increase of 2 %. Further analysis reveals that there are two main contributors to these load differences. The first is the different way both codes treat the effect of the nonuniform wind field on the local blade aerodynamics. The second is the higher average aerodynamic torque in the LLFVW simulations. It influences the transition between operating modes of the controller and changes the aeroelastic behavior of the turbine, thus affecting the loads.

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Zhang, Xuyao, Congxin Yang i Shoutu Li. "Influence of the Heights of Low-Level Jets on Power and Aerodynamic Loads of a Horizontal Axis Wind Turbine Rotor". Atmosphere 10, nr 3 (11.03.2019): 132. http://dx.doi.org/10.3390/atmos10030132.

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The influence of the heights of low-level jets (LLJs) on the rotor power and aerodynamic loads of a horizontal axis wind turbine were investigated using the fatigue, aerodynamics, structures, and turbulence code. The LLJ and shear inflow wind fields were generated using an existing wind speed spectral model. We found that the rotor power predicted by the average wind speed of the hub height is higher than the actual power in relatively weak and shallow LLJ inflow conditions, especially when the LLJ height is located inside the rotor-swept area. In terms of aerodynamic loads, when the LLJ height is located inside the rotor-swept area, the root mean square (RMS) rotor thrust coefficient and torque coefficient increase, while the RMS rotor unbalanced aerodynamic load coefficients, including lateral force, longitudinal force, tilt moment, and yaw moment, decreased. This means that the presence of both positive and negative wind shear in the rotor-swept area not only increases the rotor power but also reduces the unbalanced aerodynamic loads, which is beneficial to the operation of wind turbine. Power spectrum analysis shows no obvious difference in the power spectrum characteristics of the rotor torque and thrust in LLJ inflow conditions with different heights.

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Xiang, Xiao Jun, i Yu Qian. "Numerical Simulation of Unsteady Aerodynamic Loads over an Aircraft". Advanced Materials Research 908 (marzec 2014): 264–68. http://dx.doi.org/10.4028/www.scientific.net/amr.908.264.

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The unsteady aerodynamic loads are the basic of the aeroelastic. This paper focuses on the computation of the unsteady aerodynamic loads for forced periodic motions under different Mach numbers. The flow is modeled using the Euler equations and an unsteady time-domain solver is used for the computation of aerodynamic loads for forced periodic motions. The Euler equations are discretized on curvilinear multi-block body conforming girds using a cell-centred finite volume method. The implicit dual-time method proposed by Jameson is used for time-accurate calculations. Rigid body motions were treated by moving the mesh rigidly in response to the applied sinusoidal motion. For an aircraft model, a validation of the unsteady aerodynamics loads is first considered. Furthermore, a study for understanding the influence of different Mach number was conducted. A reverse of the trend of hysteretic loops can be observed with the increasing of the Mach number.

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Anil, Mary, i Deepa Varkey. "Recent Progress in Aerodynamics for Aeroelastic Analysis". International Journal for Research in Applied Science and Engineering Technology 10, nr 6 (30.06.2022): 2890–93. http://dx.doi.org/10.22214/ijraset.2022.44475.

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Abstract: Aerodynamics has gained considerable popularity in the aerospace industry. Based on the characteristics of a structure, aerodynamic behavior varies from structure to structure. A reliable aeroelastic analysis requires accurate capture of aerodynamic forces. To produce accurate aerodynamic loads, it is necessary to develop an appropriate aerodynamic model. A review of various approaches to aerodynamic modeling for aeroelastic analysis of diverse wing configurations is presented in this paper. The study covers a wide range of finite element software platforms used in the aeroelastic analysis in various flow regimes.

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Li, Yun Feng. "Loads Calculation of Pitch Bearing of Wind Turbine". Advanced Materials Research 148-149 (październik 2010): 479–84. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.479.

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Loads calculation process for pitch bearing of wind turbine was presented. The aerodynamic of the rotor was analyzed by using momentum theory and blade element theory firstly; then the aerodynamic loads, the gravitational loads and the centrifugal loads of the pitch bearing were calculated along each axis of the bearing coordinate system; thirdly, all the loads of each direction of the pitch bearing load were composed into three loads, they are radial, axial and tilting moment loads. A calculation example was given at last.

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He, Pan, i Jian Xia. "Study on the Influence of Low-Level Jet on the Aerodynamic Characteristics of Horizontal Axis Wind Turbine Rotor Based on the Aerodynamics–Controller Interaction Method". Energies 15, nr 8 (7.04.2022): 2709. http://dx.doi.org/10.3390/en15082709.

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Accurate prediction of the aerodynamic characteristics of wind rotors subjected to various wind profiles is of considerable importance in the aerodynamics and structural design of wind turbines. As a very complex atmospheric phenomenon, the impact of a low-level jet (LLJ) on the aerodynamic characteristics of wind rotors is becoming more and more significant with the increase in wind turbine height. Additionally, during calculating the aerodynamic characteristics of the wind rotor, the known wind speed, rotor speed, and blade-pitch angle are generally required. However, when the wind profile is in the LLJ condition, it is difficult to determine the blade-pitch angle and rotor speed. Therefore, in this paper, the blade-element-momentum (BEM) method is exploited by considering the coupling with the generator-torque controller and blade-pitch controller. In order to solve the problem of the unknown rotor speed and blade-pitch angle under the LLJ condition, a C++ code is developed. Then, the influence of the LLJ on the aerodynamic characteristics of the wind rotor is exclusively examined. The research results show that the calculation method can precisely evaluate the rotor speed, blade-pitch angle, and aerodynamic characteristics of the wind rotor. The influence of the LLJ on the aerodynamic loads of the wind rotor is greater than that of the wind shear. When the LLJ is placed inside the rotor swept area, the aerodynamic loads of the blade exhibit two local maximums and local minimums with the variation of the azimuth angle in a rotation period. The closer the LLJ height is to the hub height, the greater the average aerodynamic loads of the wind rotor are, and the smaller the amplitude of aerodynamic loads of the blade is relative to the average value. When the LLJ height is positioned outside the rotor swept area, the change law of the aerodynamic loads of the blade would be similar to that of the wind subjected to a very strong wind shear inflow. This study provides a crucial reference for a more rational assessment of the aerodynamic characteristics of wind turbines under the action of complex wind profiles, as well as revealing the influence of the LLJ on the aerodynamic characteristics of wind turbines.

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Liu, Jun, Zhengqi Gu, Taiming Huang, Shuya Li, Ledian Zheng i Kai Sun. "Coupled analysis of the unsteady aerodynamics and multi-body dynamics of a small car overtaking a coach". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, nr 14 (22.02.2019): 3684–99. http://dx.doi.org/10.1177/0954407019831559.

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The severe additional aerodynamic loads that are generated on a small car when overtaking a coach have an adverse effect on the car handling stability and its safety. In this article, a two-way coupling of the unsteady aerodynamics and multi-body dynamics is performed in order to study the mutual interactions of a car in an overtaking maneuver with a coach. The unsteady aerodynamic interactions are obtained by using SST (Menter) K-Omega Detached Eddy Simulation and overset mesh technology. The aerodynamics couple the multi-body dynamics, taking into account the effects of the transverse spacing and the cross winds. To validate the necessity of the two-way coupling method, a one-way coupling of the aerodynamics to the vehicle motion is also conducted. Finally, by comparing the aerodynamic loads and the dynamic response of the overtaking car in different overtaking maneuvers between one- and two-way coupling, the results show that it should be considered with two-way coupling analyses of the car while overtaking a coach, particularly under the severe conditions of a lower transverse spacing or the crosswinds.

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Zeng, Xiaohui, Han Wu, Jiang Lai i Hongzhi Sheng. "Hunting stability of high-speed railway vehicles on a curved track considering the effects of steady aerodynamic loads". Journal of Vibration and Control 22, nr 20 (9.08.2016): 4159–75. http://dx.doi.org/10.1177/1077546315571986.

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Aerodynamic loads may have effects on the hunting stability, and the factor of curved track makes it more complicated. Therefore, considering the steady aerodynamic loads generated by crosswind and airflow in the opposite advancing direction of train, the hunting stability of high-speed railway vehicle on a curved track is studied in this paper. The changes of gravitational restoring force and creep coefficients which are caused by aerodynamic loads are considered, and the change of equilibrium position due to aerodynamic loads, centrifugal force and the factor of curved track is also in consideration. A mathematical model of a high-speed railway vehicle during curve negotiation with aerodynamic loads is set up. A program based on the model is written and verified. Using this program, the linear critical speed considering the effects of aerodynamic loads is determined by the eigenvalue analysis. This paper investigates the critical speeds in three aerodynamic conditions. Considering the aerodynamic loads, the dependence of critical speed on curve radius and super-elevation is analyzed, and the impact of aerodynamic loads on instability mode is analyzed as well. In addition, this paper obtains the dominant factors affecting critical speed and the variation tendency of critical speed with primary longitudinal stiffness by orthogonal experiments. The results show that the critical speed decreases or increases while the wind is blowing to outer rail or inner rail respectively. The aerodynamic loads produce obvious effects on the instability mode. The variation tendency of critical speed dependence on curve radius in the conditions with aerodynamic loads keeps consistent with the case without aerodynamic loads. It is seen from the orthogonal experiments that, aerodynamic loads and curve radius are the dominant factors affecting linear critical speed of vehicle on a curved track, and the linear critical speed decreases with the increasing of primary longitudinal stiffness.

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Rozprawy doktorskie na temat "Aerodynamic loads"

Heathcote, Daniel. "Aerodynamic loads control using mini-tabs". Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760920.

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Aircraft encounter increased aerodynamic loads when exposed to gusts, turbulence andmanoeuvres. Currently, these loads are mitigated through the use of ailerons and spoilers to reduce lift, in turn reducing the loads passed to the aircraft structure. However, these actuators are limited in their frequency response and cannot control loads produced by higher frequency events. Therefore, an actuator which can mitigate high frequency oscillatory loads is required, with a deployment reduced frequency, k of up to 1. One such promising load control actuator is the minitab, consisting of a small span-wise strips, similar to the Gurney flap, deployed normal to the airfoil upper surface. Key to the actuator’s high frequency response is its low inertia, meaning that a small energy input can achieve a significant effect. To investigate the efficacy of the minitab on load alleviation a series of steady state, periodic and transient measurements were conducted at a Reynolds number of 6.6 x 105. These experiments aimed to fully evaluate the effect of chordwise location, mini-tab height and angle of attack on steady state load control. The dynamic response was categorised, in terms of magnitude, phase and time delay by the periodic and transient measurements. Mini-tabs of height h/c = 0.02 and 0.04 were employed in a steady state configurationacross a range of chordwise locations to investigate the effects of mini-tab height and chordwise position. Overall, the mini-tab was found to have a lift reducing effect which increased with height. It was found that the effect of the chordwise location was highly dependent on the angle of attack. Placement close to the trailing edge induced a large effect at α = 0°, creating an effective change in camber comparable to conventional Gurney flap use. Peak suction over the lower surface increased resulting in a reduction of ΔCL = -0.48. Approaching stall, effectiveness decreased as the mini-tab became immersed in the separated flow. Placement at xf/c = 0.60 produced an almost constant lift reduction between α = 0° and 5° of ΔCL ≈ -0.60, with a gradual reduction to stall. A mini-tab positioned close to the leading edge (xf/c = 0.08) was found to separate the flow effectively at low incidences but with no noticeable change in lift observed. It was found that the flow separation produced by the mini-tab effectively eliminated the suction peak on the upper surface. However, placement close to the leading edge has increasing effectiveness towards stall, as the shear layer induced by the separation was displaced further from airfoil surface. Peak lift reduction at stall was found to be ΔCL ≈ -0.67. The optimum chordwise location for peak lift reduction is dependent on the airfoil angle of attack: the position of the mini-tab for maximum lift reduction moves towards the leading edge as the angle of attack increases. The second stage utilised a deployable mini-tab up to reduced frequencies, k = 0.79, placedat xf/c = 0.85, to assess the mini-tab’s frequency response. The force measurements indicate that the mini-tab has a decreasing effect on lift reduction with increasing actuation frequency. This trend is comparable to Theodorsen’s function, based on the change in circulation. For α = 0°, the normalised peak-to-peak lift reduction decreased from 1 for steady state deployment to around 0.6 at k = 0.79. In addition, a phase lag exists between the mini-tab deployment and the aerodynamic response which increased with actuation reduced frequency, k. However, the measured phase lag is substantially larger than Theodorsen’s prediction. Increasing the angle of attack, α reduced the mini-tab’s effect on lift while increasing the phase angle when comparing equal k values. Particle Image Velocimetry measurements indicate that the delay and reduction in effectiveness of periodic deployment is due to the presence and growth of the separated region behind the mini-tab. Overall, the mini-tab was found to be an effective, dynamic lift reduction device with the separated region behind the mini-tab key to the amplitude and phase delay of lift response. Finally, the aerodynamic response of the mini-tab was investigated during a transientdeployment. The delay in aerodynamic response to mini-tab actuation was consistent with literature. The normalised deployment period, τdeploy did not provide a significant alteration in the aerodynamic response for deployment periods below τdeploy = 3, with the aerodynamic response reaching the steady state value around τ = 6-8. The aerodynamic response of the mini-tab was approximated using a simple, 1st order system response to a ramp-step input of gradient 1/τdeploy, indicating that the aerodynamic response of the mini-tab is further delayed for higher angles of attack, due to the presence of separated flow in the vicinity of the mini-tab. PIV measurements were utilised to analyse the effect of transient mini-tab deployment, indicating a delay in the development of the separation region created by the mini-tab, producing a corresponding delay in aerodynamic response. In addition, outward deployment was found to have a slower aerodynamic response than inward deployment, as the flow was found to take to detach slower than to reattach.

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Mackman, Thomas James. "Surrogate model construction for steady aerodynamic loads". Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633231.

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An efficient method for predicting steady aerodynamic loads with respect to varying geometric and flow parameters is to use a surrogate model to interpolate or approximate a finite set of Computational Fluid Dynamics (CFD) simulations. Further improvements to the strategy for constructing the surrogate have the potential to provide more accurate predicted values or to reduce the number of simulations required to achieve a model of sufficient quality. This work was originally motivated by the task of providing data for calculating structural loads for civil passenger aircraft, but is directly relevant for closely related applications such as providing aerodynamic data for flight mechanics analysis, and quantification of race-car aerodynamic performance. The objective at the outset was to develop aspects toward an improved surrogate modelling strategy for predicting aerodynamic data that enables a reduction in the overall simulation budget. To this end, the fundamental topics of adaptive sampling, model parameter tuning, and practical implementation for aerodynamic data have been investigated, with the goal of developing novel methods in each of these areas, and analysing their operation. Details of an adaptive sampling method based on a combination of curvature-adaptive and space-filling components are presented, including recovery of expected behaviour for analytic functions, formulation of the space-filling component, simultaneous addition of update points; and how best to optimise the criterion efficiently for multidimensional problems. An advanced strategy for choosing locally varying interpolation parameters is then presented, which works by optimising a single value to scale a prescribed local distribution of parameters, subject to constraints on the properties of the interpolation matrix. Following this, the use of various physics-based responses to drive the sampling algorithm and techniques for mitigating noise are investigated for application to aerodynamic data.

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Spagnolo, Stefano. "Unsteady aerodynamic loads on aircraft landing gear". Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/397089/.

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The aim of the current work is to improve the accuracy and efficiency of aerodynamic load predictions on landing gear in flight conditions, as part of the UK TSB ALGAAP (Advanced Landing Gear Aero-loads and Aero-noise Prediction) project. To this purpose, both experiments and simulations are performed on simplified landing-gear components. The new geometry presented in this work is a configuration composed of two simplified wheels in tandem. Experimental and numerical results from a single-wheel geometry are used as a baseline for comparison. The models are tested in the University of Southampton wind-tunnel complex, where forces, surface pressures and velocity fields are measured to gain a better understanding of both mean and unsteady flow features. Also, a vibration test is employed for the first time in a wind tunnel to validate the unsteady load measurements. The results of the experiments are presented in this thesis, showing the wake structure of the flow past the tandem wheels and the configurations that provide minimum values of mean drag and unsteady fluctuations. On the same single-wheel and tandem-wheel geometries, advanced numerical simulations such as Delayed Detached-Eddy Simulations (DDES) with the Spalart-Allmaras equation are used to predict the flow. The methodology is based on the use of techniques to improve the efficiency of the process, thus unstructured grids with a semi-structured boundarylayer mesh are employed to achieve the desired results. The results of the simulations are compared with the experiments, showing the importance of modifying the standard turbulence model in order to consider the laminar-turbulent transition for improved accuracy. Proper Orthogonal Decomposition (POD) is also employed to analyse the data of both experiments and simulation, in order to obtain a better insight of the flow features. Finally, additional simulations are performed on a simplified four-wheel landing gear to understand the effects of additional components, such as axles and bogie beam. The results show the high importance of the axles on the flow past the wheels and the effect of the modifications of the turbulence model on the full landing gear.

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Kirchmayr, Sara. "Comparison of Aerodynamic Methods for the Computation of Control Surface Loads". Thesis, KTH, Flygdynamik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185022.

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This paper presents loads computations for the generic UCAV configuration F19, originally devised by the German Aerospace Center (DLR). Different aerodynamic methods are investigated and their effect on concentrated structural loads is assessed. Design manoeuvres are defined based on the manoeuvre authority. Inertia loads are considered for a preliminary mass breakdown provided by DLR. The loads analysis process is performed both with the DLR and the Airbus Defence and Space (AD&S) aerodynamic data sets. Finally, total loads are generated and the effect of the different underlying aerodynamic methods analysed.

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Spjutare, Christian. "Aerodynamic Loads on External Stores - Saab 39 Gripen : Evaluation of CFD methods for estimating loads on external stores". Thesis, Linköping University, Applied Thermodynamics and Fluid Mechanics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54127.

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External stores mounted on aircraft generate loads which need to be estimated before first takeoff. These loads can be measured in a wind tunnel but since the possible store configurations are basically endless, testing them all is neither economically feasible nor time efficient. Thus, scaling based on geometrical similarity is used. This can, however, be a crude method. Stores with similar geometrical properties can still behave in different ways due to aerodynamic interference caused by adjacent surfaces.

To improve the scaling performance, this work focuses on investigating two CFD codes, ADAPDT and Edge. The CFD simulations are used to derive the difference in aerodynamic coefficients, or the Δ-effect, between a reference store and the new untested store. The Δ-effect is then applied to an existing wind tunnel measurement of the reference store, yielding an estimation of the aerodynamic properties for the new store.

The results show that ADAPDT, using a coarse geometry representation, has large difficulties predicting the new store properties, even for a very simple store configuration on the aircraft. Therefore it is not suited to use as a scaling tool in its present condition. Edge on the other hand uses a more precise geometry representation and proves to deliver good estimations of the new store load behavior. Results are well balanced and mainly conservative. Some further work is needed to verify the performance but Edge is the recommended tool for scaling.

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McColl, Chance C. "A matched-harmonic confluence approach to rotor loads prediction with comprehensive application to flight test". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45837.

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Future management of helicopter fleets will be more heavily based on individual component damage tracking and less on legacy usage monitoring (flight parameter-based) methods. This enhances health assessment capabilities by taking into account the actual loads on a component-by-component basis. However, accurate loads prediction in rotating frame components remains a challenge. Even with advanced computational fluid dynamics (CFD) techniques, prediction of the unsteady aerodynamic loads acting on the rotor blades is computationally intensive and problematic in terms of accurate loads prediction across the entire flight regime of the helicopter. High-speed flight can potentially introduce both shock and near-stall effects within a given rotor rotation. Low-speed flight can include blade-vortex interaction effects, wherein flow from a given blade (vorticity loading from tip vortices) impinges upon the preceding blade, causing unsteady aerodynamic loading that is difficult to quantity and predict numerically. Vehicle maneuvering can produce significantly higher blade pitching moments than steady flight. All of these regimes combine to represent the loading history of the rotor system. Therefore, accurate loads prediction methods, in terms of matching peak-to-peak, magnitude, phase, as well as vibratory/harmonic content, are required that capture all flight regimes for all critical structural components. This research focuses on the development of a loads prediction method, known as the Load Confluence Algorithm (LCA), and its application to the analysis of a large set of flight test data from the NASA/US Army UH-60A Airloads Program. The LCA combines measured response at a prescribed set of locations with a numerical model of the rotor system. For a given flight condition (steady flight, maneuvers, etc.) the numerical simulation's predicted loads distribution is iteratively incremented (by harmonic) until convergence with measured loads is reached at the prescribed locations (control points). Predicted loads response at non-instrumented locations is shown to be improved as well, thus enhancing fatigue lifing methods for these components. The procedure specifically investigates the harmonic content of the applied loads and the improved prediction of the harmonic components. The impact of the enhanced accuracy on loads predictions on component structural fatigue is illustrated by way of an example. Results show that, for a limited sensor set (two 3-axis sensors per blade), blade loads are accurately predicted across a full range of flight regimes. Hub loads are best modeled using the pushrod as the control point. Results also show that load magnitude has a tremendous influence on damage, with a 25% over-estimation of vibratory load resulting in a damage factor of nearly 3. This research highlights the importance of accurate loads prediction for a rotorcraft life tracking program. Small inaccuracies in loads lead to dramatic errors in damage assessment.

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Mansor, Shuhaimi. "Estimation of bluff body transient aerodynamic loads using an oscillating model rig". Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/13208.

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A method for the estimation of transient aerodynamic data from dynamic wind tunnel tests has been developed and employed in the study of the unsteady response of simple automotive type bodies. The experimental setup consists of the test model mounted to the oscillating model facility such that it is constrained to oscillate with a single degree of freedom of pure yawing motion. The yaw position is recorded from a potentiometer and the time response provides the primary measurement. Analysis of the wind-off and wind-on response allows the transient aerodynamic loads to be estimated. The frequency of oscillation, (synonymous with the frequency of disturbing wind input) is modified by altering the mechanical stiffness of the facility. The effects of Reynolds number and oscillation frequency are considered and the model is shown to exhibit damped, self-sustained and self-excited behaviour. The transient results are compared with a quasi-steady prediction based on conventional tunnel balance data and presented in the form of aerodynamic magnification factor. The facility and analysis techniques employed are presented and the results of a parametric study of model rear slant angle and of the influence of C-pillar strakes is reported. The results are strongly dependent on shape but for almost all rear slant angles tested the results show that the transient response exceeds that predicted from steady state data. The level of unsteadiness is also significantly influenced by the rear slant angles. The addition of C-pillar strakes is shown to stabilise the flow with even small strakes yielding responses below that of steady state. From the simulation results the self-sustained oscillation is shown to occur when the aerodynamic damping cancels the mechanical damping. The unsteadiness in the oscillation can be simulated by adding band-limited white noise with an intensity close to that of the turbulence intensity found in the wake. From vehicle crosswind simulation results the aerodynamic yaw moment derivative and its magnification factor are shown to be the important parameters influencing the crosswind sensitivity and path deviation.

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Fischer, Tim [Verfasser]. "Mitigation of Aerodynamic and Hydrodynamic Induced Loads of Offshore Wind Turbines / Tim Fischer". Aachen : Shaker, 2012. http://d-nb.info/1052408753/34.

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Berdon, Randall. "Flow structures and aerodynamic loads of a rolling wing in a free stream". Thesis, University of Iowa, 2019. https://ir.uiowa.edu/etd/6705.

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The leading-edge vortex (LEV) is a structure found in unsteady aerodynamics that can alter the forces induced on wings and other rotating structures. This thesis presents an experimental study on LEV development on low aspect-ratio wing rolling in a uniform flow at high angles of attack. The flow structure dynamics of rotating wings in the presence of a free stream are not well understood due to the limited studies under these conditions. In this study, a broad parameter space with varying advance ratio and wing radius of gyration are analyzed using dye-visualizations. In most cases, either a conical LEV structure developed on the inboard part of the wing and persisted to a significant roll angle, as well as the arch structure. Plenoptic PIV was used to validate observations in flow visualizations as well as identify finer structures. A binary classification criterion was defined based on the formation and persistence of the inboard conical LEV structure. This criterion identified the LEV as either conical ,non-conical or transitional. Previous studies inspired the proposal of a ”rotation parameter” ,ΠRot, that was a based on a non-dimensional velocity gradient. A value of ΠRot = 0.17 was found to separate conical and non-conical LEV parameter, suggesting the fundamental importance of this parameter to LEV dynamics. Furthermore, the forces were analyzed to understand the impact of the flow structure on the forces. The conical LEVs had a transient peak followed by irregular udulations while the non-conical LEVs produced high frequency oscillations. In both cases, the force could be understood based on the time-evolution of the LEVs. Passive bleeding was considered within this study to perturb the flow. Four passive bleed configurations were experimented with at different hole locations and sizes. It was found that a hole applied near the wing root with a large diameter perturbed the flow and transformed the structure from conical to non-conical classifications. This provides a platform to further understand the flow mechanisms that govern LEV formation and evolution by drastically changing flow structures and maintaining the same geometric and kinematic parameters. Additional studies were done analyzing the changes on the forces on the wing. The lift on the passive bleeding did not seem to be affected however, the thrust was decreased to nearly 0.

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Marpu, Ritu Priyanka. "Physics based prediction of aeromechanical loads for the UH-60A rotor". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47661.

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Helicopters in forward flight experience complex aerodynamic phenomena to various degrees. In low speed level flight, the vortex wake remains close to the rotor disk and interacts with the rotor blades to give rise to blade vortex interaction phenomena. In high speed flight, compressibility effects dominate leading to the formation of shocks. If the required thrust is high, the combination of high collective pitch and cyclic pitch variations give rise to three-dimensional dynamic stall phenomena. Maneuvers further exacerbate the unsteady airloads and affect rotor and hub design. The strength and durability of the rotor blades and hub components is dependent on accurate estimates of peak-to-peak structural loads. Accurate knowledge of control loads is important for sizing the expensive swash-plate components and assuring long fatigue life. Over the last two decades, computational tools have been developed for modeling rotorcraft aeromechanics. In spite of this progress, loads prediction in unsteady maneuvers which is critical for peak design loads continues to be a challenging task. The primary goal of this research effort is to investigate important physical phenomena that cause severe loads on the rotor in steady flight and in extreme maneuvers. The present work utilizes a hybrid Navier-Stokes/free-wake CFD methodology coupled to a finite element based multi-body dynamics analysis to systematically study steady level and maneuvering flight conditions. Computational results are presented for the UH-60A rotor for a parametric sweep of speed and thrust conditions and correlated with test data at the NFAC Wind Tunnel. Good agreement with test data has been achieved using the current methodology for trim settings and integrated hub loads, torque, and power. Two severe diving turn maneuvers for the UH-60A recorded in the NASA/Army Airloads Flight Tests Database have also been investigated. These maneuvers are characterized by high load factors and high speed flight. The helicopter experiences significant vibration during these maneuvers. Mean and peak-to-peak structural loads and extensive stall phenomena including an advancing side stall phenomena have been captured by the present analyses.

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Książki na temat "Aerodynamic loads"

Development, North Atlantic Treaty Organization Advisory Group for Aerospace Research and. Aircraft dynamic loads due to flow separation. Neuilly sur Seine, France: AGARD, 1990.

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North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development. Aircraft dynamic loads due to flow separation. Neuilly-sur-Seine: AGARD, 1990.

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Dillenius, Marnix F. E. Improvements to the missile aerodynamic prediction code DEMON3. Hampton, Va: Langley Research Center, 1992.

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Winebarger, Roger M. Loads and motions of an F-106B flying through thunderstorms. Washington, D.C: National Aeronautics and Space Administration, Scientific and Technical Information Branch, 1986.

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L, Peterson Randall, i Ames Research Center, red. Full-scale hingeless rotor performance and loads. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1995.

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L, Peterson Randall, i Ames Research Center, red. Full-scale hingeless rotor performance and loads. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1995.

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L, Peterson Randall, i Ames Research Center, red. Full-scale hingeless rotor performance and loads. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1995.

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Baumann, Peter Helmut. Messung von aerodynamisch bedingten Modellverformungen im Windkanal mittels Moire-Interferometrie. Koln, Germany: DLR, 1994.

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North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development. Aircraft loads due to turbulence and their impact on design and certification. Neuilly sur Seine, France: AGARD, 1994.

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North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development. Aircraft loads due to turbulence and their impact on design and certification. Neuilly sur Seine, France: AGARD, 1994.

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Części książek na temat "Aerodynamic loads"

Karimirad, Madjid. "Aerodynamic and Hydrodynamic Loads". W Offshore Energy Structures, 187–221. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-12175-8_9.

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Rutschmann, Sabrina, Klaus Ehrenfried i Andreas Dillmann. "Aerodynamic Loads Induced by Passing Trains on Track Side Objects". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 343–51. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-03158-3_35.

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Ginevsky, A. S., i A. I. Zhelannikov. "Aerodynamic Loads on Aircraft Encountering Vortex Wakes of Other Aircraft". W Foundations of Engineering Mechanics, 129–48. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-01760-5_8.

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Zhang, Hui. "Aerodynamic Loads Analysis for a Maneuvering Aircraft in Transonic Flow". W Lecture Notes in Electrical Engineering, 176–200. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-3305-7_15.

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Gan, Edward Chern Jinn, i Salim Mohamed Salim. "Numerical Simulation of the Aerodynamic Loads on Trees During Storms". W Transactions on Engineering Technologies, 187–99. Dordrecht: Springer Netherlands, 2015. http://dx.doi.org/10.1007/978-94-017-9804-4_13.

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Maceri, Franco, i Giuseppe Vairo. "Modelling and Simulation of Long-Span Bridges under Aerodynamic Loads". W Novel Approaches in Civil Engineering, 359–81. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-45287-4_32.

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Piana, G., A. Manuello, R. Malvano i A. Carpinteri. "Natural Frequencies of Long-Span Suspension Bridges Subjected to Aerodynamic Loads". W Dynamics of Civil Structures, Volume 4, 419–31. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-04546-7_45.

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Schulz, Volker, Roland Stoffel i Heinz Zorn. "Structural Optimization of 3D Wings Under Aerodynamic Loads: Topology and Shell". W Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 223–35. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-72020-3_14.

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Poryvaev, Ilya, Aleksandr Semenov i Marat Safiullin. "Aerodynamic Research of Wind and Snow Loads on the Cylinder Tank Roofs". W Design, Fabrication and Economy of Metal Structures, 537–44. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-36691-8_81.

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Sarı, Sarih, Ali Dogrul i Seyfettin Bayraktar. "The Aerodynamic Wind Loads of a Naval Surface Combatant in Model Scale". W Lecture Notes in Networks and Systems, 68–76. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-05230-9_7.

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Streszczenia konferencji na temat "Aerodynamic loads"

Da Ronch, Andrea, Kenneth J. Badcock, Alex Khrabrov, M. Ghoreyshi i R. Cummings. "Modeling of Unsteady Aerodynamic Loads". W AIAA Atmospheric Flight Mechanics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-6524.

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Aly, Aly Mousaad, i Girma Bitsuamlak. "Aerodynamic Loads on Solar Panels". W Structures Congress 2013. Reston, VA: American Society of Civil Engineers, 2013. http://dx.doi.org/10.1061/9780784412848.137.

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Duda, Benjamin M., Andreas Deurig, Francisco Flores Alvarenga i Gregory M. Laskowski. "Landing Gear Retraction Under Aerodynamic Loads". W AIAA AVIATION 2022 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2022. http://dx.doi.org/10.2514/6.2022-3527.

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Karkehabadi, Reza, i Ray Rhew. "Investigating and Analyzing Applied Loads Higher than Limit Loads". W 24th AIAA Aerodynamic Measurement Technology and Ground Testing Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2004. http://dx.doi.org/10.2514/6.2004-2197.

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BEHR, VANCE. "Measurements of individual parachute loads in a clustered parachute system". W 10th Aerodynamic Decelerator Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1989. http://dx.doi.org/10.2514/6.1989-923.

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LAWRENCE, J., J. OLER i D. ADAMSON. "An experimental investigation of the aerodynamic loads on cambered plates". W 10th Aerodynamic Decelerator Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1989. http://dx.doi.org/10.2514/6.1989-935.

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Ray, Eric. "Reconstruction of Orion EDU Parachute Inflation Loads". W AIAA Aerodynamic Decelerator Systems (ADS) Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-1260.

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Iwanski, Kenneth, i Robert Nelson. "Forebody Aerodynamic Loads Due to Rotary Motion". W 20th AIAA Applied Aerodynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2002. http://dx.doi.org/10.2514/6.2002-3261.

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Liu, Tianshu, D. Barrows, A. Burner i R. Rhew. "Aerodynamic loads based on optical deformation measurements". W 39th Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2001. http://dx.doi.org/10.2514/6.2001-560.

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SHINODA, PATRICK, i CHARLES SMITH. "SEPARATION OF ROTOR AND TEST STAND LOADS IN ROTORCRAFT WIND-TUNNEL TESTING". W 14th Aerodynamic Testing Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1986. http://dx.doi.org/10.2514/6.1986-737.

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Raporty organizacyjne na temat "Aerodynamic loads"

Homicz, G. F. Numerical simulation of VAWT stochastic aerodynamic loads produced by atmospheric turbauence: VAWT-SAL code. Office of Scientific and Technical Information (OSTI), wrzesień 1991. http://dx.doi.org/10.2172/5177561.

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Luttges, Marvin W., Mark S. Miller, Michael C. Robinson, Derek E. Shipley i David A. Simms. Evidence That Aerodynamic Effects, Including Dynamic Stall, Dictate HAWT Structure Loads and Power Generation in Highly Transient Time Frames. Office of Scientific and Technical Information (OSTI), sierpień 1994. http://dx.doi.org/10.2172/10177826.

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Cicolani, Luigi S., Jeffery Lusardi, Lloyd D. Greaves, Dwight Robinson, Aviv Rosen i Rueben Raz. Flight Test Results for the Motions and Aerodynamics of a Cargo Container and a Cylindrical Slung Load. Fort Belvoir, VA: Defense Technical Information Center, kwiecień 2010. http://dx.doi.org/10.21236/ada517702.

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