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Dissertations / Theses on the topic 'Dynamics of rotor'

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Published: 4 June 2021
Last updated: 6 February 2022

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1

Matos, Catherine Anne Moseley. "Download reduction on a wing-rotor configuation." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12058.

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2

Stackley, Sean Joseph. "Dynamics of full annular rotor rub." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/10945/21799.

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3

Fernando, Bothalage D. R. "Fluid dynamics of rotor-stator cavities." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/43057.

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This investigation is of mass, momentum and heat transfer applications of the idealised rotor-stator cavities using Computational Fluid Dynamics (CFD). This approach is based on previous literature that provides a fundamental view of the subject. However, this research is more focused on the development and simulation of high-fidelity computational models to refine the understanding of rotor-stator flow problems in engineering. An open source CFD toolbox, OpenFOAM, is used to solve Navier-Stokes equations and turbulence is modelled using Large eddy simulation (LES) approaches. The rotor boundary layer roughness is modelled by the parametric force approach, which is an ideal method to represent real-world roughness. Different types of rough wall conditions are imposed on the rotor. The roughness of the rotor wall affected the mean velocity profiles and turbulence intensity at the rotor. Increasing the roughness height transmits these effects to the stator wall. The outer wall of the rotor-stator cavity provides a passage to transport the roughness induced disturbances to the stator side, which tends to an unsteady flow even at minor roughness levels. The nanofluid heat transfer in the rotor-stator cavities is investigated using single-phase and two-phase transport models. Both models result in enhanced heat transfer rate by using different volume fractions of nanoparticles. The two-phase models provide additional information on the relative slip in the nanoparticle phase due to the Brownian and thermophoresis effects. Near the hot stator, particles are displaced away from the surface, which results in a mild reduction of heat transfer rates. The final section studies the Lagrangian particle dynamics and deposition in a Rotating Disk Chemical Vapour Deposition (RCVD) chamber. Here, the rotating effects of the disk highly agitate the particle phase, which enhances the deposition efficiencies on the rotor. Apart from that, carrier phase turbulence and thermophoretic forces are important factors in particle dynamics.
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4

Abu-Mahfouz, Issam Abdullah. "Routes to chaos in rotor dynamics." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060787527.

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5

Sotiriou, C. P. "An experimental and a theoretical investigation of rotor pitch damping using a model rotor." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277512.

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6

Samuelsson, Joakim. "Rotor dynamic analysis of 3D-modeled gas turbinerotor in Ansys." Thesis, Solid Mechanics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19071.

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The world we are living in today is pushing the technology harder and harder. The products need to get better and today they also need to be friendlier to the environment. To get better products we need better analysis tools to optimize them and to get closer to the limit what the material can withstand. Siemens industrial Turbomachinery AB, at which thesis work is made, is constructing gas and steam turbines. Gas and steam turbines are important in producing power and electricity. Electricity is our most important invention we have and most of the people are just taking electricity for granted. One way to produce electricity is to use a gas turbine which is connected to a generator and by combing the turbine with a steam turbine the efficiency can be up to 60 %. That is not good enough and everybody want to get better efficiency for the turbines, meaning less fuel consumption and less impact on the environment.

The purpose of this thesis work is to analyze a tool for rotor dynamics calculations. Rotor dynamics is important in designing a gas turbine rotor because bad dynamics can easily lead to disaster. Ansys Classic version 11 is the analyze program that is going to be evaluated for the rotor dynamic applications. Nowadays rotor dynamics is done with beam elements i.e. 1D models, but in this thesis work the beam elementsare going to be changed to solid elements. With solid elements a 3D model can be built and thanks to that more complex calculations and simulations can be made. For example, with a 3D model 3D effects can be shown and e.g. simulations with blade loss can be done. 3D effects are not any problem today but in the future the gas turbines have to get better and maybe also the rotational speed will increase.

Ansys isn’t working perfectly yet, there are some problems. However Ansys have a good potential to be an additional tool for calculations of rotor dynamics, because more complex calculations and simulations can be done. More knowledge and time needs to form the rules to modeled a rotor and developing the analysis methods. Today the calculated lateral critical speeds are lower than the ones obtained from the in-house program Ardas version 2.9.3 which is used in Siemens Industrial Turbomachinery AB today. The difference between the programs are not so big for the four first lateral modes, only 3-8 %, but the next three lateral modes have a difference of 10-20 %. The torsion frequencies from Ansys are the same as the ones from Ardas, when the Solid186 elements are used to model the blades.

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7

Ferrarese, Gastone <1983&gt. "Dynamics and control issues of multi-rotor platforms." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7127/.

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This thesis deals with the analytic study of dynamics of Multi--Rotor Unmanned Aerial Vehicles. It is conceived to give a set of mathematical instruments apt to the theoretical study and design of these flying machines. The entire work is organized in analogy with classical academic texts about airplane flight dynamics. First, the non--linear equations of motion are defined and all the external actions are modeled, with particular attention to rotors aerodynamics. All the equations are provided in a form, and with personal expedients, to be directly exploitable in a simulation environment. This has requited an answer to questions like the trim of such mathematical systems. All the treatment is developed aiming at the description of different multi--rotor configurations. Then, the linearized equations of motion are derived. The computation of the stability and control derivatives of the linear model is carried out. The study of static and dynamic stability characteristics is, thus, addressed, showing the influence of the various geometric and aerodynamic parameters of the machine and in particular of the rotors. All the theoretic results are finally utilized in two interesting cases. One concerns the design of control systems for attitude stabilization. The linear model permits the tuning of linear controllers gains and the non--linear model allows the numerical testing. The other case is the study of the performances of an innovative configuration of quad--rotor aircraft. With the non--linear model the feasibility of maneuvers impossible for a traditional quad--rotor is assessed. The linear model is applied to the controllability analysis of such an aircraft in case of actuator block.
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8

Karpenko, Evgueni. "Nonlinear dynamics of a Jeffcott Rotor with imperfections." Thesis, University of Aberdeen, 2003. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=158924.

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An in-depth analytical, numerical and experimental study investigating the vibrational characteristics of a rotor system with a clearance is the main objective of this thesis.  The mathematical modelling of a two degrees-of-freedom rotor system was done based on the Jeffcott rotor model.  The physical model assumes a situation where gyroscopic forces are neglected and concentrates on the dynamic responses caused by interactions between a whirling rotor and a massless snubber ring, which has much higher stiffness than the rotor. Two analytical methods for calculating nonlinear dynamic responses of the rotor system are devised in order to obtain robust analytical solutions maintaining high computational accuracy. To unveil the global dynamics of the rotor system different nonlinear dynamics analysis techniques in the form of time trajectories, phase portraits, bifurcation diagrams, Poincaré maps, power spectrum analysis, basins of attraction and parameter planes are employed.  In particular, the effect of preloading on the system dynamics was also investigated. Based on analysis of the nonlinearity of the restoring forces, the Jeffcott rotor model was justified in comparison with the squeeze film damping journal using the short bearing approximation. Design and basic modification to the existing experimental rig was carried out in order to create a ‘smart’ structure to effectively control the system responses using an ER damper, Shape Memory Alloys composite beams, eccentricity controllers and forcing frequency.  Extensive experimental studies are undertaken to explore the system dynamics and justify the computational model.
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9

Tu, Chihyung. "Computer-aided design software for rotor dynamics analysis." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07102009-040616/.

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10

Cheng, Yuping. "Dynamics of Hypoid and Bevel Geared Rotor Systems." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1391708583.

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11

Xie, Lihan. "Suivi numérique des bifurcations pour l'analyse paramétrique de la dynamique non-linéaire des rotors." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI018/document.

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Au cœur des moyens de transport, de transformation d'énergie, et de biens d'équipements, les machines tournantes peuvent avoir des comportements dynamiques complexes dus à de multiples sources de non linéarités liées aux paliers hydrodynamiques, à la présence de fissures, aux touches rotor-stator, ... Des phénomènes comme les décalages fréquentiels et donc de vitesses critiques, les cycles d'hystérésis avec sauts d'amplitudes, le changement brutal du contenu fréquentiel des réponses, sont des expressions de ces comportements. Résoudre les équations du mouvement induites par des modélisations avec des éléments finis de type poutre ou volumique, pour calculer les réponses à des sollicitations diverses (comme le balourd ou le poids propre), est réalisable avec des méthodes d'intégration pas à pas dans le temps mais au prix de temps de calcul prohibitifs. Cela devient particulièrement préjudiciable au stade du pré-dimensionnement où il est nécessaire de réaliser rapidement des études paramétriques. Aussi une alternative intéressante est de mettre en {\oe}uvre une méthode numérique, à la fois générale et efficace pour analyser la réponse non linéaire des rotors en régime stationnaire. La démarche proposée combine, dans un premier temps, la méthode de la balance harmonique (HBM) et la technique de bascule Temps-Fréquence (AFT) afin d'obtenir rapidement dans le domaine fréquentiel les réponses périodiques des rotors à grand nombre de degrés de liberté apportés par les éléments finis volumiques. Puis, l'association à la méthode de continuation par pseudo-longueur d'arc aboutit à établir continûment l'ensemble des solutions d'équilibre dynamique sur la plage de vitesse de rotation. Enfin la stabilité dynamique locale de la solution périodique est analysée grâce à des indicateurs de bifurcation basés sur l'évolution des exposants de Floquet. Ainsi sont détectées les bifurcations de branches de solutions périodiques de type point limite, point de branchement et notamment Neimark-Sacker. Leur localisation est déterminée précisément en résolvant un système augmenté constitué de l'équation du mouvement et d'une équation supplémentaire caractérisant le type de bifurcation considéré. En déclarant un paramètre du système (coefficient de frottement, jeu rotor/stator, amplitude de l'excitation,...) comme nouvelle variable, l'utilisation de la technique de continuation conjointement avec le système augmenté détermine directement le cheminement des bifurcations en fonction de ce paramètre sur la nappe des réponses non linéaires. Les suivis de bifurcations délimitent les zones de fonctionnement spécifiques, extraient efficacement l'essentiel du comportement dynamique et offrent ainsi une nouvelle approche pour dimensionner de façon efficace les systèmes notamment en rotation. Nombre des développements réalisés sont implantés dans le code de calcul Cast3M
Generally speaking, the rotating systems utilized in the energy production have a small rotor-stator gap, are able to run during long periods, and are mounted on hydrodynamic bearings. Rotor-stator interactions in case of blade loss, crack propagation due to fatigue, and a variable stiffness due to the nonlinear restoring forces of the bearings can make the rotordynamics nonlinear and the responses complicated: significant amplitude and frequency shifts are introduced, sub- and super-harmonics appear, and hysteresis occurs. It is of great importance to understand, predict and control this complicated dynamics. Due to the large number of DOFs and the broad range of study frequency, the computation time for solving the equations of motion by a temporal integration method can be quite prohibitive. It becomes particularly disadvantageous at the design stage where a parametrical study need to be quickly performed. An alternative numerical method, which is general and effective at the same time, is proposed in order to analyse the nonlinear response of the rotors at steady state. Firstly, the periodic responses of nonlinear rotors are calculated in the frequency domain by combining harmonic balance method (HBM) and alternating frequency-time (AFT). With the help of continuation method, all dynamic equilibrium solutions of nonlinear systems are determined for the range of study frequency. Then, Floquet exponents which are the eigenvalues of Jacobian are sought for stability analysis of periodic solutions. Then the local stability of the periodic solution is analysed through the bifurcation indicators which are based on the evolution of Floquet exponents. The bifurcations of periodic solution branch, such as limit point, branch point, and Neimark-Sacker bifurcation, are thus detected. By declaring a system parameter (friction coefficient, rotor / stator gap, excitation amplitude, ...) as a new variable, applying once again the continuation method to the augmented system determines directly the bifurcation's evolution as a function of this parameter. Thus, parametric analysis of the nonlinear dynamic behaviour is achieved, the stability boundary or the regime change boundary is directly determined. Numerous developments are implemented in the calculation code Cast3M
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12

Ozbay, Serkan. "Extension-Twist Coupling Optimization in Composite Rotor Blades." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10422.

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For optimal rotor performance in a tiltrotor aircraft the difference in the inflow and the rotor speeds between the hover and cruise flight modes suggests different blade twist and chord distributions. The blade twist rates in current tiltrotor applications are defined based upon a compromise between the figure of merit in hover and propeller efficiency in airplane mode. However, when each operation mode is considered separately the optimum blade distributions are found to be considerably different. Passive blade twist control, which uses the inherent variation in centrifugal forces on a rotor blade to achieve optimum blade twist distributions in each flight mode through the use of extension-twist coupled composite rotor blades, has been considered for performance improvement of tiltrotor aircraft over the last two decades. The challenge for this concept is to achieve the desired twisting deformations in the rotor blade without altering the aeroelastic characteristics of the vehicle. A concept referred to as the sliding mass concept is proposed in this work in order to increase the twist change with rotor speed for a closed-cell composite rotor blade cross-section to practical levels for performance improvement in a tiltrotor aircraft. The concept is based on load path changes for the centrifugal forces by utilizing non-structural masses readily available on a conventional blade, such as the leading edge balancing mass. A multilevel optimization technique based on the simulated annealing method is applied to improve the performance of the XV15 tiltrotor aircraft. A cross-sectional analysis tool, VABS together with a multibody dynamics code, DYMORE are integrated into the optimization process. The optimization results revealed significant improvements in the power requirement in hover while preserving cruise efficiency. It is also shown that about 21% of the improvement is provided through the sliding mass concept pointing to the additional flexibility the concept provides for tailoring of the structure without any additional weight penalty on the system.
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13

Hromádka, Adam. "Dynamika rotoru turbodmychadla s kluznými ložisky na bázi MBS." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231714.

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The first part of the thesis describes construction of turbochargers. The next chapter summarizes currently used methods to solve dynamics of vehicle turbocharger´s rotor. Build-up of the model of a rotor and substitution of a joint with a bearing is appended with advantages and disadvantages. Practical part of the thesis focusses at analyse of a specific rotor of turbocharger with use of MBS. Output of the analyse are rotor´s vibrations. Last chapter complains methods to improve the model.
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14

Hiatt, Daniel S. "A study of helicopter rotor dynamics and modeling methods." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA304198.

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15

Neilson, Richard David. "Dynamics of simple rotor systems having motion dependent discontinuities." Thesis, University of Dundee, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362927.

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16

CHAVEZ, RAMIRO GERMAN DIAZ. "DYNAMICS OF AN HORIZONTAL ROTOR ON ELASTOMERIC BEARING SUPPORTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4338@1.

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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
Dentro do campo dos controladores passivos, um dos dispositivos usados pelas suas propriedades de amortecimento são os Apoios Elásticos, que constituem uma solução econômica e efetiva na supressão ou atenuação das vibrações em sistemas dinâmicos com problemas de ressonância ou instabilidade, freqüentemente pela falta de amortecimento suficiente. Este trabalho envolve o estudo de um rotor horizontal com apoios elásticos (silicone), adaptado a partir de um rotor existente, o estudo de diversos efeitos sobre a sua operação, a medição de seu movimento, a identificação dos parâmetros do problema, a medição e validação a partir de resultados simulados em um modelo numérico. Os fenômenos incluídos no estudo são o efeito giroscópio (rotor descentrado com respeito do vão), desbalanceamento do rotor e empenamento do eixo. Neste trabalho os parâmetros do sistema foram determinados usando técnicas de identificação, análise modal e otimização não linear devido à anisotropia do sistema.
Viscoelastic Passive Controllers are an important field of technological research due to the development of new materials and design techniques. Damping properties allow an easy retrofit of existing machines with excessive vibration problems, developing Elastomeric Bearing Supports. They are an economic and effective solution in the suppression or attenuation of vibrations in dynamic systems suffering from instability or resonance problems, which often lack of sufficient damping. This work involves the study of an horizontal rotor with elastomeric bearing supports, adapted of another one, the study of several effects on his operation, the measurement of his motion, the identification of the problems parameters, the measurement and validation from the simulated results in a numeric model. Phenomena included in the study are the gyroscopic effect (rotor out of the middle), rotor unbalance and shaft bow. In this work the systems parameters were determined using identification, modal analysis and nonlinear optimization techniques due to the anisotropy of the system.
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17

Xu, Yeyin. "STABILITY AND BIFURCATION DYNAMICS OF JOURNAL BEARING ROTOR SYSTEMS." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/dissertations/1835.

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In this dissertation, the mechanical models of 2-DOF and 4-DOF nonlinear journal bearing rotor systems are established. A more accurate model of oil film forces is derived from Reynolds equations. The periodic motions in such nonlinear journal bearing systems are obtained through discrete mapping method. Such a semi-analytical method constructs an implicit discrete mapping structure for periodic motions by discretization of the continuous journal bearing rotor differential equations. Stable and unstable periodic solutions of periodic motions are obtained with prescribed accuracy. The bifurcation tree of periodic motions in rotor system without oil film forces is demonstrated through the route from period-1 motion to period-8 motion. Stable period-2 and unstable period-1 motion are presented for 2 DOF journal bearing rotor system. Possibly infinite periodic solutions are found in 4 DOF journal bearing rotor system. For the rotor systems, the stability and bifurcations of periodic motions are analyzed through eigenvalue analysis of the corresponding Jacobian matrix of the discretized nonlinear systems. The frequency amplitude characteristics of periodic motions in 2 DOF journal bearing system are presented for a good understanding of the nonlinear dynamics of journal bearing rotor system in frequency domain . The rich dynamics of the journal bearing systems are discovered. The numerical illustrations of stable periodic motions are brought out with the initial conditions from analytical prediction.
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18

Gurkan, Niyazi Ersan. "Non-linear Mathematical Modeling Of Gear Rotor Bearing Systems Including Bearing Clearance." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606798/index.pdf.

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ABSTRACT NON-LINEAR MATHEMATICAL MODELING OF GEAR-ROTOR-BEARING SYSTEMS INCLUDING BEARING CLEARANCE GÜ
RKAN, Niyazi Ersan M.S. Department of Mechanical Engineering Supervisor: Prof. Dr. H. Nevzat Ö
ZGÜ
VEN November 2005, 130 pages In this study, a non-linear mathematical model of gear-rotor systems which consists of elastic shafts on elastic bearings with clearance and coupled by a non-linear gear mesh interface is developed. The mathematical model and the software (NLGRD 2.0) developed in a previous study is extended to include the non-linear effects due to bearing clearances by using non-linear bearing models. The model developed combines the versatility of using finite element method and the rigorous treatment of non-linear effect of backlash and bearing clearances on the dynamics of the system. The software uses the output of Load Distribution Program (LDP), which computes loaded static transmission error and mesh compliance for the contact points of a typical mesh cycle, as input. Although non-varying mesh compliance is assumed in the model, the excitation effect of time varying mesh stiffness is indirectly included through the loaded static transmission error, which is taken as a displacement input into the system. Previous computer program which was written in Fortran 77 is rewritten by using MatLAB 7.0 and named as NLGRD (Non-Linear Geared Rotor Dynamics) Version 3.0. The program is highly flexible and open to further developments. The program calculates dynamic to static load ratio, dynamic transmission error, forces and displacements at bearings. The mathematical model suggested and the code (NLGRD version 3.0) are validated by comparing the numerical results obtained from the model suggested with experimental data available in literature. The results are also compared with those of previously developed non-linear models. The effects of different system parameters such as bearing stiffness, bearing clearance and backlash on the gears are investigated. The emphasis is placed on the interaction of clearances in bearings with other system parameters.
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19

Abras, Jennifer N. "Enhancement of aeroelastic rotor airload prediction methods." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28182.

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Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Smith, Marilyn; Committee Member: Bauchau, Olivier; Committee Member: Costello, Mark; Committee Member: Moulton, Marvin; Committee Member: Ruffin, Stephen.
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20

Fulton, Mark V. "Stability of elastically tailored rotor blades." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/12248.

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21

Tang, Wei. "Numerical solutions of unsteady flow past rotor sections." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/13336.

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22

Malpica, Carlos A. "Contributions to the dynamics of helicopters with active rotor controls." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8344.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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23

Johnson, Catherine. "Optimisation of aspects of rotor blades using computational fluid dynamics." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/7553/.

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This work presents a framework for the optimisation of various aspects of rotor blades in forward flight. The literature survey suggests that the quest for such a method is generating much research as more performance is obtainable from current designs. With increasing computational power and efficient methods, this can be of practical use to the helicopter industry. The proposed method employs CFD in conjunction with metamodels such as artificial neural networks (ANNs) and kriging interpolation, and a non-gradient based optimiser, in the form of genetic algorithms (GAs), for optimisation. The approach is demonstrated using several cases, including the optimisation of linear twist of rotors in hover (a steady case) and the optimisation of rotor sections in forward flight (an unsteady case); other cases include transonic aerofoils, wing and rotor tip planforms. For rotor tip planforms, first a simple rectangular rotor in hover was optimised. Then the developed method was used to optimise the anhedral and sweep of the UH60-A rotor blade in forward flight while constraining its hover performance and the final rotor optimisation was for a BERP-like rotor in forward flight, also constraining hover performance. For each case, a parameterisation method was defined, a specific objective function created using the initial CFD data and the metamodel was used for evaluating the objective function during the optimisation using the GAs. The obtained results suggest optima in agreement with engineering intuition but provide precise information about the shape of the final lifting surface and its performance. The results were checked by comparison with the Pareto subset of data and the metamodels were also validated with high-fidelity CFD data. Neither was sensitive to the employed techniques with substantial overlap between the outputs of the selected methods. The main CPU cost was associated with the population of the CFD database necessary for the metamodel. To improve this further, the Harmonic Balance alternative for obtaining the CFD data (as opposed to Time Marching) was used to increase efficiency and reduce clock time for the BERP-like tip optimisation. The novelty of this method is the use of a metamodel in conjunction with high-fidelity CFD data so that high-resolution performance improvements can be captured efficiently using a non-gradient based method.
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24

Bochette, Nikolaus J. "Computational analysis of flow through a transonic compressor rotor." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FBochette.pdf.

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25

Velkova, Cvetelina Vladimirova. "Modélisation du comportement dynamique des rotors d’hélicoptères." Thesis, Paris, ENSAM, 2013. http://www.theses.fr/2013ENAM0055/document.

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Modélisation du comportement dynamique des rotors d'hélicoptèresL'objectif de la thèse est l'étude et la modélisation du comportement dynamique et aérodynamique du rotor de l'hélicoptère en considérant à la fois les forces d'inertie et les forces aérodynamiques et en tenant compte des déformations élastiques des pales. L'algorithme de couplage proposé permet d'effectuer le calcul transitoire avec échange de données entre les solveurs fluide et structure à chaque pas de temps.La particularité de cette étude est l'utilisation du modèle aérodynamique de la ligne active, qui représente les forces de pale appliquées au fluide par des termes sources. Ces termes sources sont répartis dans les cellules de maillage à l'emplacement de la pale. Ainsi, la rotation, la torsion et le battement de la pale peuvent être représentés sans aucune déformation du maillage. Un avantage de la ligne active est que la simulation utilise un nombre réduit de nœuds, car des conditions aux limites «lois des parois» ne doivent pas être modélisées.Le cas d'un petit rotor expérimental d'hélicoptère est étudié en vol d'avancement. Les solveurs de fluide et de structure sont couplés pour calculer le comportement aérodynamique et dynamique du rotor. Pour ce faire, un algorithme de couplage faible en série décalé est appliqué. Les calculs itératifs sont contrôlés par un code spécialement conçu. Au début de chaque itération, le code calcule et répartit les termes sources dans le domaine fluide. A la fin du pas de temps, le code exécute le solveur de calcul de structure pour calculer un seul pas de temps. Ce solveur calcule le déplacement de la pale sous l'effet des forces aérodynamiques, élastiques et d'inertie et renvoi les résultats au solveur fluide. Les déplacements de la pale calculés servent de référence pour le solveur fluide au pas de temps suivant, pour distribuer les termes sources. Le calcul s'arrête lorsque le critère de convergence est vérifié.Afin de valider le cas simulé, des expérimentations sont réalisées en soufflerie. La puissance et la poussée aérodynamique du rotor sont mesurées. La Vélocimétrie par images de particules (PIV) est utilisée pour obtenir le champ de vitesse autour du rotor. Les mesures PIV à phase bloqué dans des plans azimutaux ont permis de reconstituer le champ d'écoulement 3D. La comparaison entre les résultats numériques et les expériences montre un bon accord et permet de valider la méthode de couplage proposée
MODELING THE DYNAMIC BEHAVIOR OF HELICOPTER ROTORThe aim of the thesis is the investigation and modeling of dynamic and aerodynamic behavior of helicopter rotor considering both inertial and aerodynamic forces and taking into account the elastic deformation of the blades. The proposed coupling algorithm allows the transient calculations with data exchange between the fluid and structure solvers at each time step.The particularity of this research is the use of an actuator line aerodynamic model, which represents the blade forces applied to the fluid as source terms. These source terms are distributed in the grid cells where the blade is located. Thus the rotation, flapping and torsion of the blade can be represented without any grid deformation. An advantage of the actuator line is that the simulation uses a reduced number of nodes, because the “wall” boundary conditions do not need to be modeled.The case of small experimental helicopter rotor is studied in forward flight. The fluid and structure solvers are coupled to calculate aerodynamic and dynamic behavior of the rotor. For this purpose, a loosely coupling serial staggered algorithm is applied. The iterative calculations are controlled by specially developed code. At the beginning of each iteration, this code calculates and distributes the source terms in the fluid domain. At the end of the time step, the code runs the structural solver to execute a single time step. This solver calculates the blade displacement under aerodynamic, elastic and inertial forces, and the results are returned to the fluid solver. The calculated blade displacements serve as reference in the next fluid step to distribute the source terms. The calculation stops when the convergence criteria are met.In order to validate the simulated case, measurements are carried on in the wind tunnel. The power and aerodynamic thrust of the rotor are measured. Particle Image Velocimetry (PIV) is used to obtain the velocity field around the rotor. Phase locked measurement in azimuth planes enabled to reconstruct 3D flow field. The comparison between numerical results and experiments shows good agreement and permits to validate the proposed coupling method
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26

Krothapalli, Krishnamohan Rao. "Helicopter rotor dynamic inflow modeling for maneuvering flight." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12066.

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27

Riley, Troy M. "Aeroacoustics and Fluid Dynamics Investigation of Open and Ducted Rotors." University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1627667464605408.

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28

Boyd, David Douglas Jr. "Rotor/Fuselage Unsteady Interactional Aerodynamics: A New Computational Model." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28591.

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A new unsteady rotor/fuselage interactional aerodynamics model has been developed. This model loosely couples a Generalized Dynamic Wake Theory (GDWT) to a Navier-Stokes solution procedure. This coupling is achieved using a newly developed unsteady pressure jump boundary condition in the Navier-Stokes model. The new unsteady pressure jump boundary condition models each rotor blade as a moving pressure jump which travels around the rotor azimuth =and is applied between two adjacent planes in a cylindrical, non-rotating grid. Comparisons are made between predictions using this new model and experiments for an isolated rotor and for a coupled rotor/fuselage configuration.
Ph. D.
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29

Wang, Yi-Ren. "The effect of wake dynamics on rotor eigenvalues in forward flight." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/13031.

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30

Gupta, Vinit. "Quad tilt rotor simulations in helicopter mode using computational fluid dynamics." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3172.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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31

Chen, Youliang. "Effect of containment flexibility on the impact dynamics of a rotor." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362906.

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32

Robbins, Shane Laurence. "The feasibility of rotor fault detection from a fluid dynamics perspective." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/79180.

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The majority of condition monitoring techniques employed today consider the acquisitioning and analysis of structural responses as a means of profiling machine condition and performing fault detection. Modern research and newer technologies are driving towards non-contact and non-invasive methods for better machine characterisation. In particular, unshrouded rotors which are exposed to a full field of fluid interaction such as helicopter rotors and wind turbines, amongst others, benefit from such an approach. Current literature lacks investigations into the monitoring and detection of anomalous conditions using fluid dynamic behaviour. This is interesting when one considers that rotors of this nature are typically slender, implying that their structural behaviour is likely to be dependent on their aerodynamic behaviour and vice versa. This study sets out to investigate whether a seeded rotor fault can be inferred from the flow field. Studies of this nature have the potential to further a branch of condition monitoring techniques. It is envisaged that successful detection of rotor anomalies from the flow field will aid in better distinction between mass and aerodynamic imbalances experienced by rotor systems. Furthermore, the eventual goal is to better describe the adjustments made to helicopter rotor systems when performing rotor track and balance procedures. Time-dependent fluid dynamic data is numerically simulated around a helicopter tail rotor blade using URANS CFD with the OpenFOAM software package. Pressures are probed at locations in the field of the rotor and compared to results attained in an experimental investigation where good correlation is seen between the results. A blade is modelled with a seeded fault in the form of a single blade out of plane by 4°. Comparisons are drawn between the blade in its ‘healthy’ and ‘faulty’ configuration. It is observed that the fault can be detected by deviations in the amplitudes of the pressure signals for a single revolution at the probed locations in the field. These deviations manifest as increases in the frequency spectrum at frequencies equivalent to the rotational rate (1 per revolution frequencies). The results described are assessed for their fidelity when the pressure is probed at different locations in the domain of the rotor. Deviations in the pressure profiles over the surface of the blades are also seen for the asymmetric rotor configuration but may prove too sensitive for practical application.
Dissertation (MEng)--University of Pretoria, 2019.
Mechanical Engineering
MEng
Unrestricted
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33

Madden, Ryan J. "Identification of Unmodeled Dynamics in Rotor Systems Using Mu-Synthesis Approach." Cleveland State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=csu1294695084.

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34

Jarroux, Clément. "Nonlinear transient dynamics of on-board rotors supported by Active Magnetic Bearings." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI069/document.

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De manière générale, les turbomachines sont des machines tournantes permettant la conversion des différents types d’énergie. Ces dernières sont composées d’une partie mécanique en rotation, appelée rotor, interagissant avec un fluide. La rotation a donc un rôle clé pour ces machines et la liaison entre les parties fixes et les parties tournantes, appelée palier, est primordiale pour un fonctionnement fiable et optimal. Les turbomachines supportées par des paliers magnétiques actifs (PMAs) sont de plus en plus utilisées par les industriels notamment grâce à l’absence de contact direct entre parties fixes et parties tournantes, permettant un gain d’énergie et une réduction des émissions de CO2. La plupart du temps, ces machines sont « embarquées » et reposent sur des supports mobiles. Les mouvements générés par ces supports doivent être considérés dans la prévision du comportement dynamique des turbomachines afin d’améliorer les designs en conséquence. Cette thèse est une contribution à l’étude des turbomachines supportées par des PMAs sujettes à de fortes sollicitations extérieures. L’approche est numérique et expérimentale. L’utilisation d’un banc d’essais académique composé d’un système rotor-PMA, aux propriétés d’une turbomachine industrielle, a permis de tester les modèles développés pour des cas de sollicitations extérieures de type séisme et choc, générées grâce à l'excitateur 6-axes de l'equipex PHARE. Il est montré que le modèle permet la bonne prévision du comportement réel de la machine. Cet outil pourra donc être utilisé pour des designs de type industriel
Turbomachines are rotating machines enabling the conversion of the different types of energy. The latter are composed of a rotating mechanical part, called rotor, interacting with a fluid. Therefore, rotation play a key role in these machines and the mechanical link between the fixed and the rotating parts, called bearing, is essential for reliable and optimal operations. Turbomachines supported by active magnetic bearings (AMBs) are increasingly used by industrial companies, especially thanks to the absence of direct contact between fixed and rotating parts, enabling energy savings and reduction of CO2 emissions. Most of the time, these machines are "on-board" and are fixed on mobile supports. The motions generated by these supports must be considered in the prediction of the dynamic behaviour of turbomachinery in order to improve the designs accordingly. This PhD is a contribution to the study of turbomachines supported by AMBs subjected to strong external base motions. The approach is numerical and experimental. The use of an academic scale test rig comprising a rotor-AMB system, with the properties of an industrial turbomachine, allowed to test the developed models for cases of external solicitations such as earthquake and shock, thanks to the 6-axis shaker of the equipex PHARE. It is shown that the model provides good predictions of the behaviour of the machine for the tested cases. This tool can therefore be used for industrial designs
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35

Casey, Cody. "Crack detection in a rotor dynamic system by vibration monitoring." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17838.

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36

Emery, Michael Aaron. "The effects of torsional-lateral coupling on the dynamics of a gear coupled rotor." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4727.

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This thesis focuses on the torsional-lateral interactions seen in gear coupled rotors. Of particular interest are cases where the torsional stiffness parameters affect the lateral critical speeds and where lateral stiffness and damping parameters affect torsional critical speeds and amplitudes. A common procedure for critical speed calculations has been to solve lateral and torsional systems separately. This procedure is tested through an eigenvalue analysis. It is shown in this thesis, however, that torsional-lateral interactions play major roles in each other's critical speeds. Some research has seemingly uncoupled two lateral degrees of freedom from the gear system by choosing bearing forces and a coordinate system pointing along the line of action and normal to the line of action. This simplification method has been tested for cases when the lateral bearing stiffness becomes asymmetric. The force generated by a rotating imbalance also creates a variable moment arm as the center of mass rotates about the geometric center of the gear. This variable moment arm is commonly neglected, but is included in the last case study and its effects are displayed in the results section of this thesis.
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37

Lee, An Sung. "An experimental investigation of a noncontacting flexibly mounted rotor mechanical face seal." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16019.

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38

Ickes, Jacob. "Improved Helicopter Rotor Performance Prediction through Loose and Tight CFD/CSD Coupling." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1408476196.

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39

Henricks, Quinten Michael. "Computational Aerodynamic and Aeroacoustic Study of Small-Scale Rotor Geometries." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1546618814905583.

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40

King, Robert L. "Nonlinear dynamics in the modeling of helicopter rotor blade lead/lag motion." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA366866.

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Dissertation (Ph.D. in Aeronautical and Astronautical Engineering) Naval Postgraduate School, June 1999.
"June 1999". Dissertation supervisor(s): E. Roberts Wood. Includes bibliographical references (p. 81). Also available online.
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41

Samadli, Vugar. "Rotor-bearing system dynamics of a high-speed micro end mill spindle." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015756.

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42

Perera, Ittapana. "Theoretical and experimental study of coupled torsional-lateral vibrations in rotor dynamics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ38558.pdf.

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43

Pretorius, Morné. "Comprehensive active magnetic bearing modelling taking rotor dynamics into account / M. Pretorius." Thesis, North-West University, 2008. http://hdl.handle.net/10394/2647.

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The McTronX Research Group at the North-West University is conducting research in the field of Active Magnetic Bearings (AMBs) with the aim of establishing a knowledge base for future industry consultation. AMBs are environmentally friendly and are a necessity in the pebble bed modular reactor (PBMR), a South-African initiated project, which is predicted to be the means of supplying Africa and many other countries with modular energy in the future. Aside from the PBMR, there are numerous other AMB industrial applications. The aim of this project is to develop a comprehensive AMB model that considers the effect that rotor dynamics has on an AMB system. This model is used to analyse a double radial AMB, capable of suspending a rigid- and flexible rotor, to explain previously noticed phenomena. Two modelling methods are focussed on namely the System Matrix Method and Transfer Matrix Method (TMM) both of which are implemented in MATLAB®. The rigid rotor model is firstly implemented as a point mass in state-space form followed by use of the TMM to analyse its bending modes. The stability and critical speeds of the system are analysed due to a change in the supports' properties along with rotor gyroscopy and its effect on the system. During analysis of the flexible rotor the TMM was used via a similar approach as was followed with the rigid rotor. The results indicate that the system is experiencing lower than expected damping due to the model that is used within the control loop. The previously assumed rotor model in the control loop is not sufficient to describe its complex behaviour. This causes the unexpected damping characteristics. This project suggests future work to be conducted in expanding the frequency domain model of the rotor within the control loop to account for its physical shape.
Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2009.
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Collins, Kyle Brian. "A multi-fidelity framework for physics based rotor blade simulation and optimization." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26481.

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Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009.
Committee Co-Chair: Dr. Dimitri Mavris; Committee Co-Chair: Dr. Lakshmi N. Sankar; Committee Member: Dr. Daniel P. Schrage; Committee Member: Dr. Kenneth S. Brentner; Committee Member: Dr. Mark Costello. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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45

Abdulqadir, Sherwan Ahmed. "Turbulence modelling for horizontal axis wind turbine rotor blades." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/turbulence-modeling-for-horizontal-axis-wind-turbine-rotor-blades(2536b213-3a0c-4977-ac39-916a9fce98d2).html.

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This Thesis aims to assess the reliability of turbulence models in predicting the flow fields around the horizontal axis wind turbine (HAWT) rotor blades and also to improve our understanding of the aerodynamics of the flow field around the blades. The simulations are validated against data from the NREL/NASA Phase VI wind turbine experiments. The simulations encompass the use of fourteen turbulence models including low-and high-Reynolds-number, linear and non-linear eddy-viscosity models and Reynolds stress models. The numerical procedure is based on the finite-volume discretization of the 3D unsteady Reynolds-Averaged Navier-Stokes equations in an inertial reference frame with the sliding mesh technique to follow the motion of the rotor blades. Comparisons of power coefficient, normalised thrust, local surface pressure coefficients (CP) and the radial variation of the section average of normal force coefficients with published experimental data over a range of tip-speed ratios, lead to the identification of the turbulence models that can reliably reproduce the values of the key performance indicators. The main contributions of this study are in establishing which RANS models can produce quantitatively reliable simulations of wind turbine flows and in presenting the flow evolution over a range of operating conditions. At low (relative to the blade tip speed) wind speeds the flow over the blade surfaces remains attached and all RANS models return the correct values of key performance coefficients. At higher wind speeds there is circumferential flow separation over the downwind surface of the blade, which eventually spreads over the entire surface, Moreover, within the separation bubble the centrifugal force pumps the flow outwards, which at the higher wind speeds suppresses the formation of the classical tip vortices. More refined RANS models which do not rely on the linear effective viscosity approximation generally lead to more reliable predictions over this range of higher wind speeds. In particular the Gibson-Launder version of the Reynolds stress transport model and the high-Re versions of the Lien et al non-linear k-ε produce consistently reliable simulations over the entire range of wind speeds. By contrast some popular linear effective viscosity models, like the SST (k-ω) and the v^2-f, perform the poorest over this complex flow range. Finally all RANS models are also able to predict the dominant (lowest) frequency of the pressure fluctuations and the non-linear effective viscosity models, the Launder and Shima version of RSM and the SST are also able to return some of the higher frequencies measured.
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46

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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47

Duran, Celio. "Modélisation du comportement dynamique non-linéaire et transitoire de turbomoteur avec multitouches rotor/stator." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0144.

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Cette thèse traite de la dynamique non-linéaire multi-contact des ensembles rotor/stator et s’applique en particulier aux tur-bomoteurs d’hélicoptère conçus par Turboméca, groupe Safran. L’amélioration des performances des turbines à gaz pousse les constructeurs à réduire les jeux fonctionnels rotor-stator no-tamment, tout en garantissant robustesse et fiabilité. Cela nécessite de développer des modèles les plus précis possible afin de prévoir et maîtriser des situations à risques telles que les interactions rotor/stator entre les parties fixes et tournantes déclen-chées principalement, dans le cas des turbomoteurs d’hélicoptère, par la perte d’aubes. La partie 1 présente une synthèse bibliographique des principaux phénomènes physiques rencontrés suite à une touche ro-tor/stator en s’appuyant sur l’expérimentation et le calcul. Un bilan sur les différents modèles numériques de gestion du con-tact frottant est détaillé. La dualité entre méthodes temporelles et fréquentielles est aussi abordée comme la méthode de la ba-lance harmonique et les schémas d’intégration temporelle de la famille de Newmark. Il est aussi décrit deux outils d’analyse fréquentielle : le spectrogramme pour analyser l’évolution d’un spectre fréquentiel dans le temps, le full-spectrum pour pren-dre en compte les précessions du rotor. La partie 2 se focalise sur des systèmes dynamiques académiques : un oscillateur forcé à double butées, un rotor de Jeffcott et un rotor à 3 disques avec tous deux une interaction disque/carter. Compte tenu du caractère transitoire du comportement des turbomoteurs, il s’agit de tester des méthodes d’intégration temporelle pas à pas et aussi des lois de contact. Il en ressort que la méthode de Newmark à accélération moyenne, et les lois de contact type « pénalité amortie » combinées à une régularisation de la raideur et de l’amortissement par une fonction arc tangente sont pertinentes. La modélisation de rotor en flexion en ré-gime transitoire et avec plusieurs touches possibles est réalisée avec la méthode des éléments finis et l’intégration des mé-thodes et techniques précédentes. L’ensemble de la modélisation est mise en œuvre sous l’environnement Matlab et se traduit au final par un logiciel nommé ToRoS (Touche Rotor-Stator). Le turbomoteur de l’Ardiden 1H fait l’objet de la dernière partie. Le logiciel ToRoS développé est utilisé pour prévoir la dyna-mique transitoire de sa turbine libre soumise à de multiples touches, consécutifs à un départ d’aubes. Les lois de contacts ap-pliquées dépendent du type de contact : disque/carter, labyrinthe/stator, palier/butée. Durant la descente en vitesse, la ligne d’arbre adopte, en fonction du niveau de balourd, de la vitesse de rotation, des paramètres du contact et du frottement, un comportement avec un contact quasi-permanent en précession directe
This PhD thesis deals with the nonlinear transient dynamic response of rotor/stator assemblies in the case of multi-contacts, it is applied on Turbomeca’s helicopter turbo-engine. In order to improve gas turbine performances, constructors have to reduce rotor/stator clearances, while continuing to maintain component’s reliability, durability and safety. It implies the development of models to predict and control unsafe situations as, rotor/stator interactions between fixed and rotating parts, mainly triggered by a blade-loss in helicopters turbo-engine case. The first part of this document is concerned with a bibliographical summary of the main physical phenomena observed after a rotor/stator interaction, this is supported by experiments and numerical calculations. A review of the various sliding contact numerical models is presented. The duality between time and/or frequency simulation response methods as, harmonic balance method vs Newmark time integration scheme is discussed. Then two numerical tools for frequency domain analysis are described: the spectrogram to analyze frequency spectrum as a function of the time, the full-spectrum for analyzing the rotor whirl motions. The second part is focused on the time response simulation of some academic systems: an excited oscillator with two end-stops, a Jeffcott rotor and finally a 3 disks rotor both subjected to disk/casing interactions. Given the transient behavior exhibited by turbo-engine rotors following a rotor/stator contact, the purpose is to test several step-by-step time integration scheme combined with different contact laws. This analysis has shown that the Newmark scheme with constant acceleration used with damped contact penalty laws combined to stiffness and damping coefficients smoothed by arctangent functions are relevant. The rotor bending modeling during transient motion considering possible multi-contacts with the stator is realized using the finite element method and the previously reviewed contact modeling methods. The simulation is implemented under Matlab environment and is named ToRoS. (Rotor/Stator Touch). Finally, the developed modeling is applied to the Ardiden 1H turbo-engine. The ToRoS software is used to predict the transient dynamic response of the free power turbine subjected to multi-contacts, after a sudden blade-loss which is modeled by a sudden unbalance. Contact laws are applied and depend on contact type and location: disk/casing, seals, thrust bearing. Depending on the mass unbalance level, the speed of rotation, the contact and friction parameters, the rotor can be in a quasi-permanent contact state in forward whirl while the rotation speed is running-down
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48

Iacobucci, Alessandra. "Nonequilibrium stationary states of rotor and oscillator chains." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLED040/document.

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Nous étudions les propriétés des états stationnaires et de dynamiques hors-équilibre, d’un point de vue théorique et numérique. Ces dynamiques sont obtenues en perturbant la dynamique d’équilibre par forçage mécanique et/ou thermique. Dans l’approche théorique, le système considéré évolue selon une dynamique de Langevin à laquelle on ajoute une force extérieure. Nous étudions la convergence de la loi de la dynamique vers la mesure stationnaire, en donnant des estimations quantitatives du taux, dans les régimes Hamiltonien et sur amorties. Dans l’approche numérique, nous considérons une chaîne de rotateurs soumise aux deux forçages et une chaîne d’oscillateurs de Toda soumise à un forçage thermique et à une perturbation stochastique. Nous étudions les caractéristiques de l’état stationnaire et les propriétés de transport. Dans le cas de la chaîne de rotateurs nous observons en particulier que le courant d’énergie moyen est dans certains cas accru par un gradient de température opposé
We study the properties of stationary states associated with nonequilibrium dynamics from a theoretical and a numerical point of view. These dynamics are obtained by perturbing equilibrium dynamics with mechanical and / or thermal forcings. In the theoretical approach, the system considered evolves according to a Langevin dynamics perturbed by a torque. In this framework, we study the convergence of the law of dynamics to the stationary measure, giving quantitative estimates of the exponential rate, both in the Hamiltonian and `` overdamped '' regimes.By a numerical approach, we consider a chain of rotors subjected to both forcings and a chain of Toda oscillators subject to a thermal forcing and a stochastic perturbation. We study the features of the stationary state and analyze its transport properties. In particular, in the case of the rotor chain, contrary to what is naively expected, we observe that the average energy current is in some cases increased by an opposite temperature gradient
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49

Bangalore, Ashok K. "Computational fluid dynamic studies of high lift rotor systems using distributed computing." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12949.

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50

Jonnalagadda, V. R. Prasad. "A derivation of rotor blade equations of motion in forward flight and their solution." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/12963.

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