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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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Chiu, Tak Wai. "Aerodynamic loads on a railway train in a cross-wind at large yaw angles." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358612.
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Prosser, Daniel T. "Advanced computational techniques for unsteady aerodynamic-dynamic interactions of bluff bodies." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53899.
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Interactions between the aerodynamics and dynamics of bluff bodies are important in many engineering applications, including suspension bridges, tall buildings, oil platforms, wind turbine towers, air drops, and construction with cranes. In the rotorcraft field, bluff bodies are commonly suspended underneath the vehicle by tethers. This approach is often the only practical way to deliver a payload in a reasonable amount of time in disaster relief efforts, search-and-rescue operations, and military operations. However, currently a fundamental understanding of the aerodynamics of these bluff bodies is lacking, and accurate dynamic simulation models for predicting the safe flying speed are not available. In order to address these shortcomings, two main advancements are presented in this thesis.
The aerodynamics of several three-dimensional canonical bluff bodies are examined over a range of Reynolds numbers representative of wind-tunnel-scale to full-scale models. Numerical experiments are utilized, with a focus on uncertainty analysis and validation of the computations. Mean and unsteady forces and moments for these bluff bodies have been evaluated, and empirical models of the shear layer characteristics have been extracted to quantify the behaviors and provide predictive capability. In addition, a physics-based reduced-order simulation model has been developed for bluff bodies. The physics-based approach is necessary to ensure that the predicted behavior of new configurations is accurate, and it is made possible by the breakthroughs in three-dimensional bluff body aerodynamics presented in this thesis. The integrated aerodynamic forces and moments and dynamic behavior predicted by model are extensively validated with data from wind tunnels, flight tests, and high-fidelity computations. Furthermore, successful stability predictions for tethered loads are demonstrated. The model is applicable to the simulation of any generic bluff body configuration, is readily extensible, and has low computational cost.
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Pesmajoglou, Stelianos. "Three-dimensional wake computations applied to horizontal axis wind turbines." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367829.
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Öhrman, Jakob. "Evaluation of a CFD method for estimating aerodynamic loads on external stores on JAS 39 Gripen." Thesis, Umeå universitet, Institutionen för fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-44380.
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Loads determination for external stores on fighter aircraft is an important task for manufacturers in ensuring the safe operation of their aircraft. Due to the large number of possible store combinations, wind tunnel tests – the primary approach to obtaining loads data – cannot be performed for all configurations. Instead, supplementary techniques to estimating loads are necessary. One approach is to use information from another store and adapt it, using so-called scaling methods, to the non-tested store. In this thesis, a scaling method combining the results of computational fluid dynamics (CFD) simulations, for both a non-tested and a reference store, with existing wind tunnel data for the reference store, is thoroughly examined for a number of different stores, angles of attack, sideslip angles and Mach numbers. The performance of the proposed scaling method is assessed in relation to currently used scaling methods, using non-parametric and multivariate statistics. The results show no definitive improvement in performance for the proposed scaling method over the current methods. Although the proposed method is slightly more conservative, considerable variability in the estimates and an increased time consumption for scaling leads the author to advise against using the proposed method for scaling aerodynamic loads on external stores.Lastbestämning för yttre utrustning på stridsflygplan är en viktig uppgift för att tillverkarna ska kunna garantera säkerheten för sina flygplan. Då antalet möjliga utrustningskombinationer är mycket stort, kan inte vindtunneltester – normalt den främsta metoden för att erhålla lastdata – utföras för alla konfigurationer. Således behövs kompletterande metoder för att skatta laster. Ett alternativ är att använda data från en annan utrustning och anpassa den, med hjälp av så kallade skalningsmetoder, till den icke-testade utrustningen. I detta examensarbete behandlas en skalningsmetod som kombinerar resultaten från numeriska strömningsberäkningar – så kallade CFD-simuleringar – för både en testad och en icke-testad utrustning med befintliga vindtunneldata för den testade utrustningen. Metoden undersöks grundligt för ett antal olika utrustningar, anfallsvinklar, sidanblåsningsvinklar och Machtal. Prestandan hos den föreslagna skalningsmetoden utvärderas i relation till nu använda skalningsmetoder, baserat på icke-parametrisk och multivariat statistik. Resultaten visar inga definitiva förbättringar av prestanda för den föreslagna skalningsmetoden jämfört med de nuvarande metoderna. Även om den föreslagna metoden är något mer konservativ, så föranleder betydande variationer i skattningar och en ökad tidsåtgång för skalning författaren att avråda från att använda den föreslagna metoden för skalning av luftlaster på yttre utrustning.
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Chang, Byungik. "A time-domain model for predicting aerodynamic loads on a slender support structure for fatigue design." [Ames, Iowa : Iowa State University], 2007.
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Alesbe, Israa [Verfasser], and Moustafa [Akademischer Betreuer] Abdel-Maksoud. "Combined aerodynamic and hydrodynamic loads on offshore wind turbines / Israa Al-Esbe ; Betreuer: Moustafa Abdel-Maksoud." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2017. http://d-nb.info/1129780651/34.
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Kwok, Raymond Hoi-Kit. "Comparison of three widely-used aerodynamic modifications that minimize the impact of wind loads on tall buildings." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38946.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.Includes bibliographical references (leaves 59-60).
For tall buildings, motion caused by wind is usually the most damaging to the lateral support system. As a result, engineers have invented many different methods to limit the motion of the buildings, for example dampers, bracings and outriggers etc. Aerodynamic modification, which is a passive approach, can also be used to reduce the impacts of wind loads. In this thesis, three widely-used aerodynamics modifications are discussed: 1) Shaping the corners of buildings, 2) Addition of openings through buildings and 3) Optimizing cross-sectional shapes of buildings. Comparison based on five criteria related to economy, sustainability, appearance, ease of construction and effectiveness in suppressing response of buildings caused by wind, is performed. With the help of a comparison matrix, it is shown that for a building located in downtown Boston, the method based on optimizing cross-sectional shapes is the best option.
by Raymond Hoi-Kit Kwok.
M.Eng.
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Housley, Paul. "Semi-empirical prediction of the normal aerodynamic loads on axisymmetric bodies of arbitrary profile in non-uniform flowfields." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432733.
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Carn, Cheril, and cheril Carn@dsto defence gov au. "The inverse determination of aircraft loading using artificial neural network analysis of structural response data with statistical methods." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080109.090600.
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An artificial Neural Network (ANN) system has been developed that can analyse aircraft flight data to provide a reconstruction of the aerodynamic loads experienced by the aircraft during flight, including manoeuvre, buffet and distributed loading. For this research data was taken from the International Follow-On Structural Test Project (IFOSTP) F/A-18 fatigue test conducted by the Royal Australian Air Force and Canadian Forces. This fatigue test involved the simultaneous application of both manouevre and buffet loads using airbag actuators and shakers. The applied loads were representative of the actual loads experienced by an FA/18 during flight tests. Following an evaluation of different ANN types an Ellman network with three linear layers was selected. The Elman back-propagation network was tested with various parameters and structures. The network was trained using the MATLAB 'traingdx' function with is a gradient descent with momentum and adaptive learning rate back-propagation algorithm. The ANN was able to provide a good approximation of the actual manoeuvre or buffet loads at the location where the training loads data were recorded even for input values which differ from the training input values. In further tests the ability to estimate distributed loading at locations not included in the training data was also demonstrated. The ANN was then modified to incorporate various methods for the calculation and prediction of output error and reliability Used in combination and in appropriate circumstances, the addition of these capabilities significantly increase the reliability, accuracy and therefore usefulness of the ANN system's ability to estimate aircraft loading.To demonstrate the ANN system's usefulness as a fatigue monitoring tool it was combined with a formulae for crack growth analysis. Results inficate the ANN system may be a useful fatigue monitoring tool enabling real time monitoring of aircraft critical components using existing strain gauge sensors.
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Maines, Nathan Louis. "Use of the Discrete Vortex Method to Calculate Wind Loads over a Surface-Mounted Prism and a Bridge Cross-Section with Flaps." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/32952.
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This thesis aims at presenting the Discrete Vortex Method (DVM) as a tool to determine the flow field and associated wind loads over structures. Two structures are considered: the first is a surface-mounted prism and is used to simulate wind loads over low-rise structures. The second is a bridge section with attached flaps that can be oriented to vary the moment coefficient. Advantages and disadvantages of using DVM for these applications are discussed. For the surface-mounted prism, the results show that the developed code correctly predicts the flow separation around the corners. As for the surface pressures, it is concluded that parallel processing, which could be easily implemented for DVM, should be used to correctly predict surface pressures and their variations. This is due to the required slow time advancement of the computations. The results on attaching flaps to bridge sections yield required orientations to minimize moments under different angles of attack.Master of Science
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Habte, Filmon Fesehaye. "Database-Assisted Analysis and Design of Wind Loads on Rigid Buildings." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2573.
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The turbulent nature of the wind flow coupled with additional turbulence created by the wind-building interaction result in highly non-uniform, fluctuating wind-loading on building envelopes. This is true even for simple rectangular symmetric buildings. Building codes and standards should reflect the information on which they are based as closely as possible, and this should be achieved without making the building codes too complicated and/or bulky. However, given the complexity of wind loading on low-rise buildings, its codification can be difficult, and it often entails significant inconsistencies. This required the development of alternative design methods, such as the Database-Assisted-Design (DAD) methodology, that can produce more accurate and risk-consistent estimates of wind loads or their effects.
In this dissertation, the DAD methodology for rigid-structures has been further developed into a design tool capable of automatically helping to size member cross sections that closely meet codified strength and serviceability requirements. This was achieved by the integration of the wind engineering and structural engineering phases of designing for wind and gravity loads. Results obtained using this method showed DAD’s potential for practical use in structural design. Different methods of synthesizing aerodynamic and climatological data were investigated, and the effects of internal pressure in structural design were also studied in the context of DAD. This dissertation also addressed the issues of (i) insufficiently comprehensive aerodynamic databases for various types of building shapes, and (ii) the large volume (in size) of existing aerodynamic databases, that can significantly affect the extent to which the DAD methodology is used in engineering practice.
This research is part of an initiative to renew the way we evaluate wind loads and perform designs. It is transformative insofar as it enables designs that are safe and economical owing to the risk-consistency inherent in DAD, meaning that enough structural muscle is provided to assure safe behavior, while fat is automatically eliminated in the interest of economy and CO2 footprint reduction.
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Junior, Luciano Jorge de Andrade. "A ação do vento em silos cilíndricos de baixa relação altura/diâmetro." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-15092015-113629/.
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Os silos metálicos cilíndricos de chapa corrugada e cobertura cônica são as unidades mais utilizadas no Brasil para o armazenamento de produtos granulares. As principais ações variáveis que atuam sobre os silos são as pressões devidas aos produtos armazenados e ao vento, sendo esta ação crítica quando o silo se encontra vazio. Devido à grande eficiência estrutural da forma cilíndrica e à resistência elevada do aço, estas estruturas são leves e delgadas e, portanto, suscetíveis a perdas de estabilidade local e global e arrancamento. Com a finalidade de avaliar estes efeitos foram realizados estudos teóricos e experimentais sobre as ações do vento em silos. O trabalho foi desenvolvido com ensaios de modelos aerodinâmicos e aeroelásticos em um túnel de vento na Universidade de Cranfield, Inglaterra, com o objetivo de determinar os coeficientes aerodinâmicos no costado e na cobertura. Os resultados mostram que os valores dos coeficientes recomendados pela Norma Brasileira de vento, NBR 6123 (1990), são adequados para o costado. Para a cobertura cônica, como não são especificados pela NBR, são recomendados valores dos coeficientes aerodinâmicos determinados nos ensaios. Conclui-se também que a colocação externa das colunas é a favor da segurança e que o uso de anéis enrijecedores no costado é indicado e muito importante para a estabilidade local e global da estrutura do silo.The steel cylindrical silos made of corrugated sheets with conical roofs are the most used units to the storage of granular materials. The main silo loads are the pressures due to the stored material and to the wind, being this action the critical one when the silo is empty. Due to the high efficiency of the cylindrical form and to the high strength of the steel, these structures are thin and light-weight and, as a consequence, susceptible to the loss of local and global stability and to the pull out of the structure. With the aim to assess these effects related to the wind loading in silos, some theoretical and experimental studies were conducted. The work was carried out with aerodynamic and aeroelastic models tested in a boundary layer wind tunnel in the University of Cranfield, England, with the objective to determine the aerodynamic coefficients of the cylinder and the conical roof. The results show that the coefficients of the Brazilian Code of wind loads, NBR 6123 (1990), are adequate to the cylinder. The coefficients to the conical roof are suggested based on our tests, considering that there are no values specified by the NBR. As well it is concluded that the outside columns is on the side of safety and it is indicated the use of wind rings attached to the cylinder, which are very important to the local and global stability of the silo structure.
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Zedník, Roman. "Příprava experimentálního měření aerodynamických charakteristik na zmenšeném modelu automobilu v aerodynamickém tunelu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417795.
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This master thesis focuses on designing of an external six-component balance. This universal concept would provide access of results from different models of wings, aircraft and automobiles with relatively small scales. This work also includes theoretical background needed in aerodynamic testing, analysis of 1D beam element model of scale and explanation of components used in scale. Lastly methods of calibration and measurement in aerodynamic tunnel are described, which can be adopted for this design to achieve the adequate level of accuracy.
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Mohammadi, M. Sajad, and Rishiraj Mukherjee. "Wind Loads on Bridges : Analysis of a three span bridge based on theoretical methods and Eurocode 1." Thesis, KTH, Bro- och stålbyggnad, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-125349.
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The limitations lying behind the applications of EN-1991-1-4, Eurocode1, actions on structures-general actions-wind load-part 1-4, lead the structural designers to a great confusion. This may be due to the fact that EC1 only provides the guidance for bridges whose fundamental modes of vibration have a constant sign (e.g. simply supported structures) or a simple linear sign (e.g. cantilever structures) and these modes are the governing modes of vibration of the structure. EC1 analyzes only the along-wind response of the structure and does not deal with the cross wind response. The simplified methods that are recommended in this code can be used to analyze structures with simple geometrical configurations. In this report, the analytical methods which are used to describe the fluctuating wind behavior and predict the relative static and dynamic response of the structure are studied and presented. The criteria used to judge the acceptability of the wind load and the corresponding structural responses along with the serviceability considerations are also presented. Then based on the given methods the wind forces acting on a continuous bridge whose main span is larger than the 50 meters (i.e. > 50 meter requires dynamic assessment) is studied and compared with the results which could be obtained from the simplified methods recommended in the EC1.
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Kargarmoakhar, Ramtin. "Large-Scale Testing to Study the Effects of Critical Parameters on the Aerodynamic Behavior of Long Span Bridges." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1857.
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Long-span bridges are flexible and therefore are sensitive to wind induced effects. One way to improve the stability of long span bridges against flutter is to use cross-sections that involve twin side-by-side decks. However, this can amplify responses due to vortex induced oscillations.
Wind tunnel testing is a well-established practice to evaluate the stability of bridges against wind loads. In order to study the response of the prototype in laboratory, dynamic similarity requirements should be satisfied. One of the parameters that is normally violated in wind tunnel testing is Reynolds number. In this dissertation, the effects of Reynolds number on the aerodynamics of a double deck bridge were evaluated by measuring fluctuating forces on a motionless sectional model of a bridge at different wind speeds representing different Reynolds regimes. Also, the efficacy of vortex mitigation devices was evaluated at different Reynolds number regimes.
One other parameter that is frequently ignored in wind tunnel studies is the correct simulation of turbulence characteristics. Due to the difficulties in simulating flow with large turbulence length scale on a sectional model, wind tunnel tests are often performed in smooth flow as a conservative approach. The validity of simplifying assumptions in calculation of buffeting loads, as the direct impact of turbulence, needs to be verified for twin deck bridges. The effects of turbulence characteristics were investigated by testing sectional models of a twin deck bridge under two different turbulent flow conditions.
Not only the flow properties play an important role on the aerodynamic response of the bridge, but also the geometry of the cross section shape is expected to have significant effects. In this dissertation, the effects of deck details, such as width of the gap between the twin decks, and traffic barriers on the aerodynamic characteristics of a twin deck bridge were investigated, particularly on the vortex shedding forces with the aim of clarifying how these shape details can alter the wind induced responses.
Finally, a summary of the issues that are involved in designing a dynamic test rig for high Reynolds number tests is given, using the studied cross section as an example.
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Gillam, David A. "Airloads on a finite wing in a time dependent incompressible freestream." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/12371.
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Cantoni, Lorenzo. "Load Control Aerodynamics in Offshore Wind Turbines." Thesis, KTH, Kraft- och värmeteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291417.
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Due to the increase of rotor size in horizontal axis wind turbine (HAWT) during the past 25 years in order to achieve higher power output, all wind turbine components and blades in particular, have to withstand higher structural loads. This upscalingproblem could be solved by applying technologies capable of reducing aerodynamic loads the rotor has to withstand, either with passive or active control solutions. These control devices and techniques can reduce the fatigue load upon the blades up to 40% and therefore less maintenance is needed, resulting in an important money savings for the wind farm manager. This project consists in a study of load control techniques for offshore wind turbines from an aerodynamic and aeroelastic point ofview, with the aim to assess a cost effective, robust and reliable solution which could operate maintenance free in quite hostile environments. The first part of this study involves 2D and 3D aerodynamic and aeroelastic simulations to validate the computational model with experimental data and to analyze the interaction between the fluid and the structure. The second part of this study is an assessment of the unsteady aerodynamic loads produced by a wind gust over the blades and to verify how a trailing edge flap would influence the aerodynamic control parameters for the selected wind turbine blade.På grund av ökningen av rotorstorleken hos horisontella vindturbiner (HAWT) under de senaste 25 åren, en design som har uppstod för att uppnå högre effekt, måste alla vindkraftkomponenter och blad stå emot högre strukturella belastningar. Detta uppskalningsproblem kan lösas genom att använda metoder som kan minska aerodynamiska belastningar som rotorn måste tåla, antingen med passiva eller aktiva styrlösningar. Dessa kontrollanordningar och tekniker kan minska utmattningsbelastningen på bladen med upp till 40 % och därför behövs mindre underhåll, vilket resulterar i viktiga besparingar för vindkraftsägaren. Detta projekt består av en studie av lastkontrolltekniker för havsbaserade vindkraftverk ur en aerodynamisk och aeroelastisk synvinkel, i syfte att bedöma en kostnadseffektiv, robust och pålitlig lösning som kan fungera underhållsfri i tuffa miljöer. Den första delen av denna studie involverar 2D- och 3D-aerodynamiska och aeroelastiska simuleringar för att validera beräkningsmodellen med experimentella data och för att analysera interaktionen mellan fluiden och strukturen. Den andra delen av denna studie är en bedömning av de ojämna aerodynamiska belastningarna som produceras av ett vindkast över bladen och för att verifiera hur en bakkantklaff skulle påverka de aerodynamiska styrparametrarna för det valda vindturbinbladet.
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McNabb, Michael Lynn. "Development of a cycloidal propulsion computer model and comparison with experiment." Master's thesis, Mississippi State : Mississippi State University, 2001. http://library.msstate.edu/etd/show.asp?etd=etd-08032001-111940.
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Saini, Manjinder. "Experimental and computational study of airfoil load alteration using oscillating fence actuator." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663059971&sid=3&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Wilks, Brett Landon Burkhalter Johnny Evans. "Aerodynamics of wrap-around fins in supersonic flow." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Fall/Thesis/WILKS_BRETT_54.pdf.
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Liu, Haiying. "Interfacing comprehensive rotorcraft analysis with advanced aeromechanics and vortex wake models." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22534.
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Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2008.Committee Chair: Bauchau, Olivier; Committee Member: Armanios, Erian; Committee Member: Hodges, Dewey; Committee Member: Ruzzene, Massimo; Committee Member: Stallybrass, Michael.
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Wacker, Thomas. "A preliminary study of configuration effects on the drag of a tractor-trailer combination." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25143.
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The effect of configuration changes and add-on devices on the drag reduction of a tractor-trailer is studied through wind tunnel tests using two 1/12-scale models. The configuration changes involve ground clearance, tractor-trailer gap, roof angle and back inclination while add-on devices include flow deflectors, skirts and gap seals. Moving surface boundary layer control as a means of drag reduction is also attempted. Both drag and pressure data are obtained to help identify local contributions. Results suggest that an optimum combination of configuration parameters can reduce drag up to 17% while the add-on devices resulted in a further decrease by a modest amount. The results with moving surface boundary layer control proved to be inconclusive.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Heene, Mario. "Aerodynamic Propeller Model for Load Analysis." Thesis, KTH, Matematik (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103226.
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An aerodynamic propeller model, which can contribute to the prediction of structural loads experienced by aircraft in different flight maneuvers is presented.The model is based on Blade Element Momentum theory and is able to predict the unsymmetrical and frequency-dependent forces and moments induced by the propeller on the airplane structure at steady and unsteady inflow-conditions.In order to validate the model, a comparison with experimental results was performed and it can be seen that the model is in agreement with the experimental data providing that the aerodynamic data used for the calculations has good accuracy.En modell har utvecklats för att beräkna aerodynamiska krafter som orsakas av propellern vid manöverflygning. Modellen använder sig av klassiska bladelementteorin för predikering av osymmetriska stationära krafter som uppstår vid snedanblåsning av propellerskivan. Modellen kommer att användas inom ett forskningsprojekt om effektiv beräkning av aerodynamiska laster vid flygmanövrar och i vindbyar. En vidareutveckling av den klassiska metoden används för att ta fram instationära kraftbidrag i frekvensplanet i en form som är lämpligt för aeroelastiska stabilitetsanalys och beräkning av vindbylasterna.Jämförelser med omfattande experimentella resultat har genomförts för att validera modellen. Inom ramen för antaganden och noggrannheten i modellens indata kan modellens tillförlitighet bedömas som tillräckligt för ändamålet. Däremot visar sig att propellermodellen är -- som förväntat -- mindre lämpligt för att bedöma propellerlasterna utanför propellerns reguljära driftområdet.
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Higman, Jerry Paul. "On the indentification of harmonic loads and inflow of a coupled bending-torsion helicopter rotor blade." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/12529.
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Standingford, David William Fin. "Optimal lifting surfaces, including end plates, ground effect & thickness /." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phs785.pdf.
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Brzozowski, Daniel Paul. "Dynamic control of aerodynamic forces on a moving platform using active flow control." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42930.
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The unsteady interaction between trailing edge aerodynamic flow control and airfoil motion in pitch and plunge is investigated in wind tunnel experiments using a two degree-of-freedom traverse which enables application of time-dependent external torque and forces by servo motors. The global aerodynamic forces and moments are regulated by controlling vorticity generation and accumulation near the trailing edge of the airfoil using hybrid synthetic jet actuators. The dynamic coupling between the actuation and the time-dependent flow field is characterized using simultaneous force and particle image velocimetry (PIV) measurements that are taken phase-locked to the commanded actuation waveform. The effect of the unsteady motion on the model-embedded flow control is assessed in both trajectory tracking and disturbance rejection maneuvers. The time-varying aerodynamic lift and pitching moment are estimated from a PIV wake survey using a reduced order model based on classical unsteady aerodynamic theory. These measurements suggest that the entire flow over the airfoil readjusts within 2-3 convective time scales, which is about two orders of magnitude shorter than the characteristic time associated with the controlled maneuver of the wind tunnel model. This illustrates that flow-control actuation can be typically effected on time scales that are commensurate with the flow's convective time scale, and that the maneuver response is primarily limited by the inertia of the platform.
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Horký, Martin. "Měření aerodynamických charakteristik vozidla na základě jízdních testů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231526.
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Schoř, Pavel. "Load State of an Aircraft with an Elastic Wing." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-383528.
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V této práci je navržena metoda výpočtu zatížení letadla s netuhým křídlem, založená na spojení panelové metody prvního řádu dle Katz and Plotkin, Low-Speed Aerodynamics, 2001 s metodou stukturální analýzy dle Píštěk et al., Pevnost a životnost letadel I, 1988 a Lebofsky,Numerically Generated Tangent Stiffness Matrices for Geometrically Non-Linear Struc- tures, 2013. Panelová metoda poskytuje přasná data pro výpočet zatížení křídla od vzdušných sil za předpokladu že lze dané proudění aproximovat po- mocí potenciálního proudění, Narozdíl metod založených na interakci s CFD metodami lze navrženou metodu používat i na bežném počítači.
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Zink, Paul Scott. "A methodology for robust structural design with application to active aeroelastic wings." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12424.
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Kuchan, Abigail. "The integration of active flow control devices into composite wing flaps." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44758.
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Delaying stall is always an attractive option in the aerospace industry. The major benefit of delaying stall is increased lift during takeoff and landings as well as during high angle of attack situations. Devices, such as fluidic oscillators, can be integrated into wing flaps to help delay the occurrence of stall by adding energized air to the airflow on the upper surface of the wing flap. The energized air from the oscillator allows the airflow to remain attached to the upper surface of the wing flap. The fluidic oscillator being integrated in this thesis is an active flow control device (AFC). One common method for integrating any device into a wing flap is to remove a section of the flap and mechanically secure the device. A current trend in the aerospace industry is the increased use of fiber-reinforced composites to replace traditional metal components on aircraft. The traditional methods of device integration cause additional complications when applied to composite components as compared to metal components. This thesis proposes an alternative method for integration of the AFC devices, which occurs before the fabrication of wing flaps is completed and they are attached to the aircraft wing.
Seven design concepts are created to reduce the complications from using current methods of integration on composite wing flaps. The concepts are based on four design requirements: aerodynamics, manufacturing, maintenance, and structure. Four of the design concepts created are external designs, which place the AFC on the exterior surface of the wing flap in two types of grooved channels. The other three designs place the AFC inside the wing flap skin and are categorized as internal designs. In order for the air exiting the AFC to reach the upper surface of the wing flap, slots are created in the wing flap skin for the internal designs. Within each of the seven design concepts two design variants are created based on foam or ribbed core types.
Prototypes were created for all of the external design AFC devices and the side inserted AFC and retaining pieces. Wing flap prototypes were created for the rounded groove straight AFC design, the semi-circular groove with straight AFC, and the side inserted AFC designs. The wing flaps were created using the VARTM process with a vertical layup for the external designs. The rounded groove and semi-circular groove prototypes each went through three generations of prototypes until an acceptable wing flap was created. The side inserted design utilized the lessons learned through each generation of the external design prototypes eliminating the need for multiple generations. The lessons learned through the prototyping process helped refine the designs and determine the ease of manufacturing to be used in the design evaluation.
The evaluation of the designs is based on the four design requirements stated above. The assessment of the designs uses two levels of evaluation matrices to determine the most fitting design concept. As a result of the evaluation, all four of the external designs and one of the internal designs are eliminated. The two remaining internal designs' foam core and ribbed variants are compared to establish the final design selection. The vertically inserted AFC foam core design is the most fitting design concept for the integration of an AFC device into a composite wing flap.
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Pienkowski, John P. "Analysis of the aerodynamic orbital transfer capabilities of a winged re-entry vehicle." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FPienkowski.pdf.
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Thesis (M.S. in Space Systems Operations)--Naval Postgraduate School, September 2002.Thesis advisor(s): Stephen A. Whitmore, Michael G. Spencer. Includes bibliographical references (p. 73-74). Also available online.
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Page, Anthony Baker. "Piecewise-constant control strategies for use in minimum fuel aeroassisted orbital transfers." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-08042009-040438/.
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Gonzalez-Martino, Ignacio. "Development of Moderate-Cost Methodologies for the Aerodynamic Simulation of Contra-Rotating Open Rotors." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-01063434.
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This study is devoted to the development of moderate-cost methodologies for the aerodynamic simulation of open rotors. The main goals are, on one side, to develop and validate these rapid methodologies, and, on the other side, to better understand the mechanisms behind propeller in-plane loads, also called the 1P loads. To reach the first goal, the HOST-MINT code, based on the lifting-line theory, has been adapted and improved for the unsteady simulation of propellers and open rotors. The code has been assessed by comparison with experimental data and more complex and precise CFD simulations. Finally, the first developments and tests of a Lagrangian/Eulerian coupling strategy between HOST-MINT and the elsA CFD code have been performed. These studies enable to endeavor a number of applications of this type of rapid methodologies in the aerodynamic design of future open rotors. Moreover, these methodologies may be adapted for other domains linked to aerodynamics, such as aeroelastic problems or preliminary aeroacoustic predictions.
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Harris, John N. "Referenced pressure and temperature sensitive coatings using solid state phosphors /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/8577.
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Ytterström, Anders. "Parallel Computing for Applications in Aeronautical CFD." Doctoral thesis, KTH, Aeronautical Engineering, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3179.
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Ostler, Jon N. "Flight Testing Small, Electric Powered Unmanned Aerial Vehicles." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1223.pdf.
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Anastasiadis, John S. "Stability of cylindrical laminates by highter order shear deformable theories." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/12376.
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Ahmed, Hamza Hafez Ahmed Anwar. "End-wall flow of a surface-mounted obstacle on a convex hump." Auburn, Ala., 2009. http://hdl.handle.net/10415/1946.
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Comstock, Robert. "Hypersonic Heat Transfer Load Analysis in STAR-CCM+." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2226.
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This thesis investigates the capabilities of STAR-CCM+, a Computational Fluid Dynamics (CFD) software owned by Siemens, in predicting hypersonic heat transfer loads on forward-facing surfaces. Results show that STAR-CCM+ predicted peak heat transfer loads within +/- 20% of experimental data on the leading edge of a delta wing design from the X-20 Dyna-Soar program with 73o of sweep. Steady-state laminar simulations were run as replications of wind tunnel tests documented in NASA CR-535, a NASA technical report that measured and studied the hypersonic pressure and heat transfer loads on preliminary X- 20 wing designs across a wide range of Reynolds numbers and Mach numbers in different wind tunnel and shock tunnel facilities. One of the Mach 8.08 test cases that was run at NASA Arnold Engineering Development Center Wind Tunnel B was selected as the case of comparison for this thesis, which was designated as test AD462M-1 in the original report. The CFD simulations assumed an ideal gas in laminar flow with temperature-dependent viscosity, thermal conductivity, and isobaric specific heat across an angle of attack range from 0o to 30o. A separate CFD study of heat transfer loads of a hemisphere-cylinder at Mach 6.74 was used as a simpler and less computationally-expensive validation case compared against wind tunnel data from NASA Langley Research Center to help select the appropriate CFD solver and mesh settings for this thesis.
For the hemisphere-cylinder, the heat transfer load at the stagnation point was overpredicted in STAR-CCM+ by 21.8%. Peak heat transfer loads on the delta wing leading edge were all within +/- 20% of the wind tunnel data, which was published for angles of attack between 15o to 30o. A more adverse heat transfer gradient along the leading edge of the delta wing was also observed in the direction from the front of the wing to the outer wing tip when compared to wind tunnel data. The pressure loads on the delta wing leading edge in CFD were within +/-10% of wind tunnel measurements.
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Zhang, Luying. "Rotating instability on steam turbine blades at part-load conditions." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:cf8ecad1-0fd2-49b7-8e28-6d00c62c173e.
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A computational study aimed at improving the understanding of rotating instability in the LP steam turbine last stage working under low flow rate conditions is described in this thesis. A numerical simulation framework has been developed to investigate into the instability flow field. Two LP model turbine stages are studied under various flow rate conditions. By using the 2D simulations as reference and comparing the results to those of the 3D simulations, the basic physical mechanism of rotating instability is analysed. The pressure ratio characteristics across the rotor row tip are found to be crucial to the inception of rotating instability. The captured instability demonstrates a 2D mechanism based on the circumferential variation of unsteady separation flow in the rotor row. The 3D tip clearance flow is found not a necessary cause of the instability onset. Several influential parameters on the instability flow are also investigated by a set of detailed studies on different turbine configurations. The results show that the instability flow pattern and characteristics can be altered by the gap distance between the stator and rotor row, the rotor blading and the stator row stagger angle. Some flow control approaches are proposed based on the observations, which may also serve as design reference. The tip region 3D vortex flow upstream to the rotor row is also captured by the simulations under low flow rate conditions. Its appearance is found to be able to suppress the inception of rotating instability by disrupting the interaction between the rotor separation flow and the incoming flow. Finally, some recommendations for further work are proposed.