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Artykuły w czasopismach na temat "Stator simulations"
1
Reinmo¨ller, U., B. Stephan, S. Schmidt i R. Niehuis. "Clocking Effects in a 1.5 Stage Axial Turbine—Steady and Unsteady Experimental Investigations Supported by Numerical Simulations". Journal of Turbomachinery 124, nr 1 (1.02.2001): 52–60. http://dx.doi.org/10.1115/1.1425811.
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The interaction between rotor and stator airfoils in a multistage turbomachine causes an inherently unsteady flow field. In addition, different relative circumferential positions of several stator rows and rotor rows, respectively, have an influence on the flow behavior in terms of loss generation, energy transport and secondary flow. The objective of the presented study is to investigate the effects of stator airfoil clocking on the performance of a 1-1/2 stage axial cold air turbine. The investigated axial turbine consists of two identical stators. The low aspect ratio of the blades and their prismatic design leads to a three-dimensional outlet flow with a high degree of secondary flow phenomena. Nevertheless, the small axial gaps between the blade rows are responsible for strong potential flow interaction with the radial wake regions in the measurement planes. Consequently, parts of the wakes of the first stator are clearly detected in the rotor outlet flow. To give an overview of the time-averaged flow field, measurements with pneumatic probes are conducted behind each blade row at ten different clocking-positions of the second stator. Further, an optimized clocking position was found due to a minimum in pressure loss behind the second stator. The unsteady measurements are carried out with hot-wire probes for three selected stator-stator positions. Animations of selected flow properties show the influence of different circumferential positions of the second stator on the unsteady flow behavior and secondary flow field. In addition and compared with experimental results three-dimensional unsteady viscous flow computations are performed.
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Tomasello, Stella Grazia, Roberto Meloni, Luca Andrei i Antonio Andreini. "Study of Combustor–Turbine Interactions by Performing Coupled and Decoupled Hybrid RANS-LES Simulations under Representative Engine-like Conditions". Energies 16, nr 14 (15.07.2023): 5395. http://dx.doi.org/10.3390/en16145395.
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Combustion–turbine interaction phenomena are attracting ever-growing interest in recent years. As a matter of fact, the strong unsteady and three-dimensional flow field that characterizes the combustor is usually conserved up to the first-stage nozzle, possibly affecting its design and performance in terms of aerodynamics and the effectiveness of the cooling system as well. Such conditions are also exacerbated by the employment of lean-burn combustors, where high turbulence levels are required for the flame stabilization, resulting in even greater temperature and velocity distortions at the inlet of the first-stage nozzle. Even if it has been proven by several past studies that the best way of studying the combustor–turbine interaction is simulating the two components together, performing coupled simulations is still challenging from a numerical point of view, especially in an industrial context. For this reason, the application and generation of the most representative and reliable boundary conditions possible at the inlet of the S1N have assumed an increased importance in order to study the two components separately by performing decoupled simulations. In this context, the purpose of the present work is to compare fully integrated combustor–stator SBES simulations to isolated stator ones. To perform the stator-only calculations, the fully unsteady inlet conditions of the stator have been recorded at the interface plane between the two components in the integrated SBES simulation and then they have been reconstructed by applying the proper orthogonal decomposition (POD) technique. The SBES simulations of the isolated stator have been so performed with the aim of determining whether the flow field obtained is comparable with the one of the integrated simulation, thus allowing more realistic results to be obtained rather than imposing time-averaged 2D maps, as per standard design practice.
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Wang, Ziwei, Xiong Jiang, Ti Chen, Yan Hao i Min Qiu. "Numerical simulation of transonic compressor under circumferential inlet distortion and rotor/stator interference using harmonic balance method". Modern Physics Letters B 32, nr 12n13 (10.05.2018): 1840021. http://dx.doi.org/10.1142/s0217984918400213.
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Simulating the unsteady flow of compressor under circumferential inlet distortion and rotor/stator interference would need full-annulus grid with a dual time method. This process is time consuming and needs a large amount of computational resources. Harmonic balance method simulates the unsteady flow in compressor on single passage grid with a series of steady simulations. This will largely increase the computational efficiency in comparison with the dual time method. However, most simulations with harmonic balance method are conducted on the flow under either circumferential inlet distortion or rotor/stator interference. Based on an in-house CFD code, the harmonic balance method is applied in the simulation of flow in the NASA Stage 35 under both circumferential inlet distortion and rotor/stator interference. As the unsteady flow is influenced by two different unsteady disturbances, it leads to the computational instability. The instability can be avoided by coupling the harmonic balance method with an optimizing algorithm. The computational result of harmonic balance method is compared with the result of full-annulus simulation. It denotes that, the harmonic balance method simulates the flow under circumferential inlet distortion and rotor/stator interference as precise as the full-annulus simulation with a speed-up of about 8 times.
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Akwa, J. V., i A. P. Petry. "STATORS USE INFLUENCE ON THE PERFORMANCE OF A SAVONIUS WIND ROTOR USING COMPUTATIONAL FLUID DYNAMICS". Revista de Engenharia Térmica 10, nr 1-2 (31.12.2011): 63. http://dx.doi.org/10.5380/reterm.v10i1-2.61965.
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This paper aims at verifying the influence of using five kinds of stators in the averaged moment and power coefficients of a Savonius wind rotor using computational fluid dynamics (CFD). The analyzed stators have cylindrical shape with two and three openings, one and four deflector blades and walls shaped like a wings. The equations of continuity, Reynolds Averaged Navier-Stokes – RANS and the Eddy Viscosity Model k-ω SST, in its Low-Reynolds approaches, with hybrid near wall treatment; are numerically solved using the commercial software Star-CCM+, based on Finite Volume Method, resulting in the fields of pressure and velocity of the flow and the forces acting on the rotor buckets. The moment and power coefficients are achieved through integration of forces coming from the effects of pressure and viscosity of the wind on the buckets device. The influence of the stators use in the moment and power coefficients is checked by changing the geometry of the device for each simulations series, keeping the Reynolds number based on rotor diameter equal to 433,500. The obtained values for averaged moment and power coefficients indicate that for each type of stator used, there was maximum performance for a given tip speed ratio of rotor. Improvement in performance over the operation without stator was obtained only to the operations using stator with four deflector blades and to the stator with cylindrical shape with three openings. The improvement percentage in performance obtained for the best condition (use of four deflector blades at tip speed ratio equal to 1) is 12% compared to the performance of the rotor operating without stator.
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Tang, Jing, Jie Chen, Kan Dong, Yongheng Yang, Haichen Lv i Zhigang Liu. "Modeling and Evaluation of Stator and Rotor Faults for Induction Motors". Energies 13, nr 1 (26.12.2019): 133. http://dx.doi.org/10.3390/en13010133.
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The modeling of stator and rotor faults is the basis of the development of online monitoring techniques. To obtain reliable stator and rotor fault models, this paper focuses on dynamic modeling of the stator and rotor faults in real-time, which adopts a multiple-coupled-circuit method by using a winding function approach for inductance calculation. Firstly, the model of the induction machine with a healthy cage is introduced, where a rotor mesh that consists of a few rotor loops and an end ring loop is considered. Then, the stator inter-turn fault model is presented by adding an extra branch with short circuit resistance on the fault part of a stator phase winding. The broken rotor bar fault is then detailed by merging and removing the broken-bar-related loops. Finally, the discrete models under healthy and faulty conditions are developed by using the Tustin transformation for digital implementation. Moreover, the stator and rotor mutual inductances are derived as a function of the rotor position according to the turn and winding functions distribution. Simulations and experiments are performed on a 2.2-kW/380-V/50-Hz three-phase and four-pole induction motor to show the performance of the stator and rotor faults, where the saturation effect is considered in simulations by exploiting the measurements of a no load test. The simulation results are in close agreement with the experimental results. Furthermore, magnitudes of the characteristic frequencies of 2f1 in torque and (1 ± 2s)f1 in current are analyzed to evaluate the stator and rotor fault severity. Both indicate that the stator fault severity is related to the short circuit resistance. Further, the number of shorted turns and the number of continuous broken bars determines the rotor fault severity.
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Karanayil, Baburaj, Muhammed Fazlur Rahman i Colin Grantham. "Identification of Induction Motor Parameters in Industrial Drives with Artificial Neural Networks". Advances in Fuzzy Systems 2009 (2009): 1–10. http://dx.doi.org/10.1155/2009/241809.
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This paper presents a new method of online estimation of the stator and rotor resistance of the induction motor in the indirect vector-controlled drive, with artificial neural networks. The back propagation algorithm is used for training of the neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. For the stator resistance estimation, the error between the measured stator current and the estimated stator current using neural network is back propagated to adjust the weights of the neural network. The performance of the stator and rotor resistance estimators and torque and flux responses of the drive, together with these estimators, is investigated with the help of simulations for variations in the stator and rotor resistance from their nominal values. Both types of resistance are estimated experimentally, using the proposed neural network in a vector-controlled induction motor drive. Data on tracking performances of these estimators are presented. With this approach, the rotor resistance estimation was found to be insensitive to the stator resistance variations both in simulation and experiment.
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Rai, M. M., i N. K. Madavan. "Multi-Airfoil Navier–Stokes Simulations of Turbine Rotor–Stator Interaction". Journal of Turbomachinery 112, nr 3 (1.07.1990): 377–84. http://dx.doi.org/10.1115/1.2927670.
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An accurate numerical analysis of the flows associated with rotor–stator configurations in turbomachinery can be extremely helpful in optimizing the performance of turbomachinery. In this study the unsteady, thin-layer, Navier–Stokes equations in two spatial dimensions are solved on a system of patched and overlaid grids for an axial-turbine rotor–stator configuration. The governing equations are solved using a finite-difference, upwind algorithm that is set in an iterative, implicit framework. Results are presented in the form of pressure contours, time-averaged pressures, unsteady pressures, amplitudes, and phase. The numerical results are compared with experimental data and the agreement is found to be good. The results are also compared with those of an earlier study, which used only one rotor and one stator airfoil. The current study uses multiple rotor and stator airfoils and a pitch ratio that is much closer to the experimental ratio. Consequently, the results of this study are found to be closer to the experimental data.
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Hembera, M., H. P. Kau i E. Johann. "Simulation of Casing Treatments of a Transonic Compressor Stage". International Journal of Rotating Machinery 2008 (2008): 1–10. http://dx.doi.org/10.1155/2008/657202.
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This article presents the study of casing treatments on an axial compressor stage for improving stability and enhancing stall margin. So far, many simulations of casing treatments on single rotor or rotor-stator configurations were performed. But as the application of casing treatments in engines will be in a multistage compressor, in this study, the axial slots are applied to a typical transonic first stage of a high-pressure 4.5-stage compressor including an upstream IGV, rotor, and stator. The unsteady simulations are performed with a three-dimensional time accurate Favre-averaged Navier-stokes flow solver. In order to resolve all important flow mechanisms appearing through the use of casing treatments, a computational multiblock grid consisting of approximately 2.4 million nodes was used for the simulations. The configurations include axial slots in 4 different variations with an axial extension ranging into the blade passage of the IGV. Their shape is semicircular with no inclination in circumferential direction. The simulations proved the effectiveness of casing treatments with an upstream stator. However, the results also showed that the slots have to be carefully positioned relative to the stator location.
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Xu, Jieqiong, Qunhong Li i Shimin Wang. "Impulsive Control of the Rotor-Stator Rub Based on Phase Characteristic". Abstract and Applied Analysis 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/495747.
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An impulsive control method is proposed to eliminate the rotor-stator rubbing based on the phase characteristic. The relation between the vibration energy and the phase difference suggests the starting point for controlling the rotor-stator rubbing by implementing impulse. When the contact between the rotor and the stator occurs, the impulse is implemented inx-direction andy-direction several times to avoid the rotor-stator rubbing. The practical feasibility of this approach is investigated by numerical simulations.
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Valkov, T. V., i C. S. Tan. "Effect of Upstream Rotor Vortical Disturbances on the Time-Averaged Performance of Axial Compressor Stators: Part 1—Framework of Technical Approach and Wake–Stator Blade Interactions". Journal of Turbomachinery 121, nr 3 (1.07.1999): 377–86. http://dx.doi.org/10.1115/1.2841330.
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In a two-part paper, key computed results from a set of first-of-a-kind numerical simulations on the unsteady interaction of axial compressor stators with upstream rotor wakes and tip leakage vortices are employed to elucidate their impact on the time-averaged performance of the stator. Detailed interrogation of the computed flow field showed that for both wakes and tip leakage vortices, the impact of these mechanisms can be described on the same physical basis. Specifically, there are two generic mechanisms with significant influence on performance: reversible recovery of the energy in the wakes/tip vortices (beneficial) and the associated nontransitional boundary layer response (detrimental). In the presence of flow unsteadiness associated with rotor wakes and tip vortices, the efficiency of the stator under consideration is higher than that obtained using a mixed-out steady flow approximation. The effects of tip vortices and wakes are of comparable importance. The impact of stator interaction with upstream wakes and vortices depends on the following parameters: axial spacing, loading, and the frequency of wake fluctuations in the rotor frame. At reduced spacing, this impact becomes significant. The most important aspect of the tip vortex is the relative velocity defect and the associated relative total pressure defect, which is perceived by the stator in the same manner as a wake. In Part 1, the focus will be on the framework of technical approach, and the interaction of stator with the moving upstream rotor wakes.
Rozprawy doktorskie na temat "Stator simulations"
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JACQUES, REMI. "Simulations numeriques d'ecoulements transitionnels et turbulents dans des configurations de type rotor-stator". Paris 11, 1997. http://www.theses.fr/1997PA112386.
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Ce travail de these porte sur l'etude numerique des ecoulements transitionnels et turbulents dans une cavite confinee formee de deux disques coaxiaux dont l'un est en rotation uniforme autour de son axe de revolution (rotor), et l'autre stationnaire (stator). Les simulations numeriques sont effectuees sous l'hypothese d'axisymetrie de l'ecoulement instantane. On utilise alors un code de calcul parallelise integrant une decomposition de domaine. Plusieurs caracteristiques des ecoulements entre deux disques tournants sont reproduites : existence de couches limites sur les deux disques tournants, separees par un region centrale de l'ecoulement en rotation moyenne uniforme, caractere plus instable de la couche limite liee au disque fixe. L'existence d'un regime d'ondes inertielles a egalement ete mis en evidence dans le cur de la cavite lorsque l'ecoulement est turbulent dans la couche limite liee au disque fixe. L'etude des equations de transport des tensions de reynolds montre que la rotation modifie les distributions spatiales de certains termes intervenant dans les bilans associes a ces equations. Ils mettent egalement en evidence les limitations de l'hypothese d'axisymetrie qui modifie alors des caracteristiques intrinseques de la turbulence. Des simulations numeriques tridimensionnelles avec un code de calcul parallelise sont alors effectuees pour le regime d'ecoulement laminaire instationnaire. Ces premieres simulations ont montre que l'hypothese d'axisymetrie stabilisait l'ecoulement. Enfin, les resultats de simulation numerique sont confrontes a des resultats fournis par une modelisation de la turbulence de type k - et des resultats experimentaux. Les deux methodologies numeriques fournissent des resultats relativement proches concernant les distributions de vitesse moyenne.
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Schreiber, Johannes. "Investigation of experimental and numerical methods, and analysis of stator clocking and instabilities in a high-speed multistage compressor". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC063/document.
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Les études expérimentales et numériques suivantes visent à la compréhension profonde de l’écoulement se développant dans le compresseur haute-vitesse axial de 3.5 étages CREATE, étudié sur un banc d’essai de 2 MW au Laboratoire de Mécanique des Fluides et Acoustique (LMFA) à Lyon, France. Ce travail a trois objectifs principaux : D’abord, une description globale de l’écoulement avec une identification des limites aux méthodes d’exploration utilisées ; Ensuite, la caractérisation de l’effet du clocking stator-stator dans un compresseur à haute-vitesse ; Troisièmement, l’identification des instabilités à faibles débits pour confirmer les études sur les compresseurs à basse-vitesse et contribuer à plus de compréhension.Il est montré qu’une mauvaise interprétation des données de performance stationnaire se fait facilement en raison des contraintes de mesure et des coefficients de correction sont proposés. À certains endroits dans le compresseur, des limites aux méthodes d’exploration (expérimentales et numériques) de l’écoulement sont identifiées. Cette identification va permettre la poursuite du développement des méthodes. Les principales erreurs de prédiction des simulations concernent la surestimation du blocage induit par l’écoulement de jeu et l’augmentation de pression. En outre, les mesures fournies par les sondes de pression pneumatique surestiment la pression statique en amont des stators. Cette erreur est probablement provoquée par l’interaction entre le champ potentiel du stator et la sonde elle-même. De plus, l’anémométrie Doppler laser surestime la vitesse en aval des stators. Le transport des sillages du rotor à travers des stators n’est pas correctement capturé avec les particules d’ensemencement.Le clocking a seulement un petit effet global dans la bande d’incertitude de mesure dans ce compresseur. Plusieurs contributions à ce faible effet de clocking sont identifiées par l’analyse du transport des structures d’écoulement : Le mélange circonférentiel du sillage de stator et la déformation des sillages le long de leur trajet dans l’écoulement. L’effet local du clocking dépend de la hauteur de veine en raison de la variation de la forme des aubages et du transport des sillages. Des effets positifs et négatifs sont présentés, qui globalement se compensent dans ce compresseur. Les instabilités dans ce compresseur dépendent du point de fonctionnement et des méthodes d’exploration de l’écoulement. Aux points de fonctionnement stables et à la vitesse nominale du compresseur, les résultats numériques montrent une perturbation tournante dans les rotors 2 et 3, alors que les mesures montrent une perturbation tournante que dans le premier rotor et seulement à basse vitesse du compresseur. Dans les deux cas, les perturbations montrent des caractéristiques semblables. Une étude numérique permet d’exclure l’influence des interactions rotor-stator sur la perturbation tournante et met en évidence sa source. Des nouvelles connaissances sur le comportement stable et la périodicité du rotating instability (mesuré) sont dérivées contrairement au comportement instable suggéré par la dénomination et la littérature. Il est montré que cette perturbation évolue en cellule de décrochage tournante à l’approche de la limite de stabilité. A la vitesse nominale du compresseur, une entrée en instabilités de type spike est identifiée expérimentalement. Une description précise de l’apparition brutale du spike et sa différence par rapport à une cellule de décollement tournant sont présentéesThe following experimental and numerical investigations aim at the deep understanding of the flow field in the 3.5 stages high-speed axial compressor CREATE, studied on a 2 MW test rig at the Laboratory of Fluid Mechanics and Acoustics (LMFA) in Lyon, France. This work focuses on three major objectives: Firstly, a global description of the flow field with an identification of limitations to the used exploration methods; Secondly, the characterization of the effect of stator-stator clocking in a high-speed compressor; Thirdly, the identification of instabilities arising at low mass flow rates for confirming studies on low-speed compressors and giving new insights.This work demonstrates that a mis-interpretation of steady performance data occurs easily due to measurement constraints and correction coefficients are proposed. At certain locations in the compressor, the flow field exploration (experimental and numerical) methods are identified to be challenged. This identification will initiate further development of the methods. The main mis-predictions of the simulations concern the over-prediction of the blockage induced by the tip leakage flow and eventually an over-predicted pressure rise. Furthermore, the measurements provided by the pneumatic pressure probes over-estimate the static pressure upstream of the stators. This error is induced by the interaction between the stator potential field and the probe it-self. In addition, the laser Doppler anemometry method over-estimates the velocity downstream the stators. The transport of the rotor wakes through the stators might not be correctly captured with the seeding particles in this high-speed compressor.The investigation of the stator clocking reveals only a small global effect within the measurement uncertainty band. Several contributions to the weak effect of clocking are identified by analysis of the flow structure transport, namely the time-mean mixing out of the stator wakes and the deformation of wakes along their flow path. The local effect of clocking depends on the span-height because of the variation of the circumferential position of the stator wakes and the stator blade shape over the span-height. Local possible positive and negative effects of clocking are identified and are shown to be almost in balance in this compressor. Furthermore, this work demonstrates that the unsteadiness in the flow field is not linked conclusively to the stator clocking.In this compressor, the arising instabilities depend on the operating point and flow field exploration methods. At stable operating points and nominal compressor speed, the numerical results reveal a rotating disturbance in the rotors 2 and 3, whereas the measurements show a rotating disturbance only in the first rotor and only at part speed. In both cases the disturbance exhibits rotating instability like characteristics. An exhaustive numerical study allows to exclude the commonly assumed influence of rotor-stator interactions on the rotating disturbance and pinpoints its source. New insights into the stable behavior and periodicity of the measured rotating instability are derived contrary to the unstable behavior suggested by the naming and literature. This disturbance is shown to evolve into rotating stall cells when approaching the stability limit. At nominal compressor speed, a spike type surge inception is identified I n the measured field. A precise description of the abrupt onset of the spike cell and its difference to a rotating stall cell are presented
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D'Haudt, Emmanuel. "Étude expérimentale de l'influence des conditions périphériques sur un écoulement turbulent de type rotor-stator : premières confrontations avec des résultats de simulations numériques". Lille 1, 2006. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/2006/50376-2006-D_Haudt.pdf.
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Les recherches effectuées sur des écoulements turbulents dans des cavités interdisques ont permis de mettre en évidence l'importance des conditions aux limites. Ce présent travail a pour but de mieux comprendre les phénomènes qui régissent l'apparition de différents types d'écoulements observés dans une cavité rotor-stator non soumise à un flux radial forcé. Dans cette optique, un banc d'essais a été adapté pour étudier plus spécifiquement l'influence de deux paramètres géométriques, l'un lié à une faible différence entre le rayon des disques, l'autre relatif à la présence d'un carter permettant de supprimer l'écoulement produit par la paroi externe du rotor. La base de données constituée à partir de mesures effectuées principalement par anémométrie à fils chauds a été confrontée à des résultats de simulations numériques réalisés à l'aide du code de calcul FLUENT. L'analyse des résultats montre en particulier qu'à la périphérie du système, le fluide éjecté par l'effet centrifuge du rotor est nécessairement compensé par une injection provenant partiellement du fluide au repos situé à l'extérieur à la cavité, près du stator, et de la réintroduction du fluide éjecté par le rotor. La proportion entre ces deux sources, qui dépend étroitement des paramètres géométriques retenus, influe sur le niveau de pré-rotation du fluide en entrée de cavité et conditionne ainsi l'apparition des différents types d'écoulement observés, notamment l'écoulement en bloc de type Batchelor.
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D'Haudt, Emmanuel Bois Gérard Debuchy Roger. "Étude expérimentale de l'influence des conditions périphériques sur un écoulement turbulent de type rotor-stator premières confrontations avec des résultats de simulations numériques /". Villeneuve d'Ascq : Université des sciences et technologies de Lille, 2007. https://iris.univ-lille1.fr/dspace/handle/1908/988.
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Reproduction de : Thèse de doctorat : Mécanique : Lille 1 : 2006.N° d'ordre (Lille 1) :3874. Résumé en français et en anglais. Titre provenant de la page de titre du document numérisé. Bibliogr. p. 171-173.
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Peres, Noele. "A 3D pseudospectral method for cylindrical coordinates. Application to the simulations of rotating cavity flows". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4309/document.
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La simulation d'écoulements dans des cavités cylindriques en rotation présente une difficulté particulière en raison de l'apparition de singularités sur l'axe. Le présent travail propose une méthode collocative pseudospectrale suffisamment efficace et précise pour surmonter cette difficulté et résoudre les équations 3D de Navier-Stokes écrites en coordonnées cylindriques. Cette méthode a été développée dans le cadre des différentes études menées au laboratoire M2P2, utilisant une méthode collocative de type Chebychev dans les directions radiale et axiale et Fourier-Galerkin dans la direction azimutale [thêta]. Pour éviter de prescrire des conditions sur l'axe, une nouvelle approche a été développée. Le domaine de calcul est défini par (r,[thêta],z)∈[-1,1]×[0,2π]×[-1,1] avec un nombre N pair de points de collocation dans la direction radiale. Ainsi, r=0 n'est pas un point de collocation. La distribution de points de type Gauss-Lobatto selon r et z densifie le maillage seulement près des parois ce qui rend l'algorithme bien adapté pour simuler les écoulements dans des cavités cylindriques en rotation. Dans la direction azimutale, le chevauchement des points dû à la discrétisation est évitée par l'introduction d'un décalage égal à π/2K à [thêta]>π dans la transformée de Fourier. La méthode conserve la convergence spectrale. Des comparaisons avec des résultats expérimentaux et numériques de la littérature montrent un très bon accord pour des écoulements induits par la rotation d'un disque dans des cavités cylindriques ferméesWhen simulating flows in cylindrical rotating cavities, a difficulty arises from the singularities appearing on the axis. In the same time, the flow field itself does not have any singularity on the axis and this singularity is only apparent. The present work proposes an efficient and accurate collocation pseudospectral method for solving the 3D Navier-Stokes equations using cylindrical coordinates. This method has been developed in the framework of different studies of rotor-stator flows, using Chebyshev collocation in the radial and axial directions and Fourier-Galerkin approximation in the azimuthal periodic direction [thêta]. To avoid the difficulty on the axis without prescribing any pole and parity conditions usually required, a new approach has been developed. The calculation domain is defined as (r,[thêta];,z)∈[-1,1]×[0,2π]×[-1,1] using an even number N of collocation points in the radial direction. Thus, r=0 is not a collocation point. The method keeps the spectral convergence. The grid-point distribution densifies the mesh only near the boundaries that makes the algorithm well-suited to simulate rotating cavity flows where thin layers develop along the walls. In the azimuthal direction, the overlap in the discretization is avoided by introducing a shift equal to π/2K for [thêta]>π in the Fourier transform. Comparisons with reliable experimental and numerical results of the literature show good quantitative agreements for flows driven by rotating discs in cylindrical cavities. Associated to a Spectral Vanishing Viscosity, the method provides very promising LES results of turbulent cavity flows with or without heat transfer
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Millithaler, Pierre. "Dynamic behaviour of electric machine stators : modelling guidelines for efficient finite-element simulations and design specifications for noise reduction". Thesis, Besançon, 2015. http://www.theses.fr/2015BESA2003/document.
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Dopées par un intérêt croissant des industries telles que l’automobile, les technologies demotorisation100% électriques équipent de plus en plus de véhicules à la portée du grand public. Endépit d’une opinion commune favorable sur les faibles émissions sonores des moteurs électriques,la maîtrise des performances vibratoires et acoustiques d’une telle machine reste un challenge trèscoûteux à relever. Associant l’expertise de l’entreprise Vibrate cet du département MécaniqueAppliquée de l’institut Femto-ST, cette thèse CIFRE vise à améliorer les connaissances actuellessur le comportement mécanique de machines électriques. De nouvelles méthodes de modélisationpar éléments finis sont proposées à partir d’approches d’homogénéisation,analyses expérimentales,recalage de modèles et études de variabilité en température et en fréquence,pour permettre uneprédiction plus performante du comportement vibratoire d’un moteur électriqueBoosted by the increasing interest of industries such as automotive,100% electric engine technologies power more and more affordable vehicles for the general public.Inspite of a rather favourable common opinion about the low noisee mitted by electric motors, controlling the vibratory and acoustic performances of such machines remains a very costly challenge to take up. Associating the expertise of the company Vibratec and the institute Femto-ST Applied Mechanics Department, this industry-orientedPh.D.thesisaimsatimprovingthecurrentknowledgeaboutthe mechanicalbehaviour ofelectric machines. New finite-element modelling method sare proposedf rom homogenisation approaches,experimental analyses, model up dating procedures and variability studies in temperature and frequency, in order to predict the behaviour of an electric motor more efficiently
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Sauvage, Bastien. "Approximation et adaptation numériques pour les écoulements en machines tournantes". Electronic Thesis or Diss., Université Côte d'Azur, 2024. http://www.theses.fr/2024COAZ5045.
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Ce travail s'inscrit dans un projet de recherche dont l'objectif est de proposer des simulations numériques en fluides (CFD) capables de capturer le bruit produit par les machines tournantes.Cette thèse, au sein de ce projet, à pour objectif d'étudier des méthodes d'adaptation de maillages (instationnaires) pour des écoulements turbulents instationnaires.On commence par décrire les outils nécessaires à nos études, à savoir les méthodes numériques, les modèles de turbulences et l'adaptation de maillages. Une première partie est consacrée à l'étude de l'algorithme d'adaptation de maillage instationnaire "Transient Fixed Point" appliqué à des écoulements turbulents autour de cylindres à différents nombre de Reynolds. Puis on étudie une méthode pour prendre en compte la rotation dans les simulations,que l'on couple avec les méthodes d'adaptation de maillage. Des exemples numériques sont proposés.Ces premiers travaux se heurtent à deux importants problèmes ouverts en CFD maillage-adaptative.Afin de choisir de manière optimale le pas d'avancement en temps implicite, on présente une nouvelle méthode d'adaptation de maillages espace-temps, qui permet d'adapter simultanément le maillage en espace et le maillage en temps. Afin d'adapter le maillage à la fois à l’écoulement moyen et aux grandes structures turbulentes, on propose une nouvelle approche d'adaptation de maillage pour la turbulence en calcul LES et hybrideThis work is part of a research project aimed at proposing numerical fluid simulations (CFD) capable of capturing the noise produced by rotating machines.The aim of this thesis is to study mesh adaptation methods for unsteady turbulent flows. We begin by describing the tools required for our studies, namely numerical methods, turbulence models and mesh adaptation. The first part is devoted to the study of the "Transient" unsteady mesh adaptation algorithms applied to turbulent flows around cylinders at different Reynolds numbers. A method for taking rotation into account in simulations is then studied, and coupled with mesh the adaptation methods. Numerical examples are proposed.This initial work encounted two major unsolved problems in CFD mesh-adaptation. In order to optimally select the implicit time step, a new space-time mesh adaptation method is presented, which simultaneously adapts the space mesh and the time mesh. In order to adapt the mesh to both mean flow and large turbulent structures, a new mesh adaptation approach is proposed for turbulence in LES and hybrid computation
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Jung, Alexander. "Berechnung der Stator-Rotor-Wechselwirkung in Turbomaschinen". [S.l. : s.n.], 2000. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB8862171.
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Bridel-Bertomeu, Thibault. "Investigation of unsteady phenomena in rotor/stator cavities using Large Eddy Simulation". Thesis, Toulouse, INPT, 2016. http://oatao.univ-toulouse.fr/17867/1/BRIDEL_BERTOMEU.pdf.
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This thesis provides a numerical and theoretical investigation of transitional and turbulent enclosed rotating flows, with a focus on the formation of macroscopic coherent flow structures. The underlying processes are strongly threedimensional due to the presence of boundary layers on the discs and on the walls of the outer (resp. inner) cylindrical shroud (resp. shaft). The complexity of these flows poses a great challenge in fundamental research however the present work is also of importance for industrial rotating machinery, from hard-drives to space engines turbopumps - the design issues of the latter being behind the motivation for this thesis. The present work consists of two major investigations. First, industrial cavities are modeled by smooth rotor/stator cavities and therein the dominant flow dynamics is investigated. For the experimental campaigns on industrial machinery revealed dangerous unsteady phenomena within the cavities, the emphasis is put on the reproduction and monitoring of unsteady pressure fluctuations within the smooth cavities. Then, the LES of three configurations of real industrial turbines are conducted to study in situ the pressure fluctuations and apply the diagnostics already vetted on academic problems.
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Emmanuelli, Ariane. "Numerical simulation and modelling of entropy noise in nozzle and turbine stator flows". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC067.
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L'étude du bruit de combustion est motivée par l'augmentation de sa contribution relative au bruit émis par les moteurs aéronautiques actuels, ainsi que par son impact sur la conception de chambres de combustion à basse émission de NOx. Le bruit entropique est une source de bruit de combustion indirect générée par l'accélération de perturbations entropiques à travers les tuyères et les étages de turbine à l'aval de la chambre de combustion. Cette étude porte sur la simulation numérique et la modélisation du bruit entropique à travers une tuyère et un stator de turbine. Dans un premier temps, le bruit entropique est simulé dans une tuyère avec un code CAA (Computational AeroAcoustics) afin de valider un modèle 2D existant sous des hypothèses similaires. Les niveaux de bruit entropique et de diffusion acoustique obtenus par les deux méthodes sont en accord. Leur comparaison au bruit estimé par des modèles compacts et 1D montre que les effets bi-dimensionnels sont significatifs. De plus, de la vorticité induite par l'accélération de perturbations entropiques est identifiée, mais celle-ci ne contribue pas significativement au bruit généré. Une géométrie de stator de turbine haute pression est ensuite étudiée en 2D. Le modèle pour les tuyères 2D est étendu à ces configurations, héritant de certaines de ses hypothèses. L'étude de celles-ci montre que l'impact de la vorticité et des variations azimutales des fluctuations acoustiques, négligées par le modèle, est significatif. Ces hypothèses devront être relaxées lors de développements futurs. Les calculs CAA permettent également de caractériser la génération de bruit entropique sous hypothèses simplificatrices avec à la fois des champs porteurs Euler et RANS. Une étude plus approfondie du cas RANS est nécessaire pour sa validation, ainsi que pour mieux comprendre le rôle de la couche limite dans la génération du bruit entropique. Enfin, un canal de stator est étudié par des calculs ZDES (Zonal Detached Eddy Simulation) afin d'examiner les effets 3D et visqueux sur le bruit généré. La tri-dimensionnalité de l'écoulement est mise en évidence et les perturbations sont post-traitées en portant une attention particulière au filtrage des fluctuations hydrodynamiques et aux réflexions en parois. Les résultats obtenus par la CAA et la ZDES sont comparables, ce qui indique que la tri-dimensionnalité et la viscosité de l'écoulement ont un effet limité sur le bruit entropique généré dans un stator de turbineThe investigation of combustion noise is motivated by its growing relative contribution to the noise emitted by modern turbofan engines overall, as well as its effect on low NOx emission combustor design. Entropy noise is a source of indirect combustion noise, which is generated by the acceleration of heterogeneities, in this case entropy, downstream of the combustion chamber. This study consists of the investigation of entropy noise in nozzle and turbine stator flow using both analytical and numerical methods. Nozzle flow is considered first. A Computational AeroAcoustics (CAA) reference case is built for the validation of an existing two-dimensional semi-analytical model developed under similar assumptions. The levels of entropy noise and acoustic scattering estimated using both methods are in good agreement. Two-dimensional effects on entropy noise are highlighted, notably by comparison with compact and 1D models. In addition, vorticity induced by the acceleration of entropy noise is evidenced, but it yields negligible vortex sound. Next, the focus is shifted to a 2D high-pressure turbine stator. The 2D model for nozzle flow is extended to this configuration, inheriting some of its main assumptions. Their investigation, using CAA in particular, sets the path for future developments and allows insight to be gained into the role of both vorticity and azimuthal variation of acoustics, which are neglected by the model. CAA also allows to characterise entropy noise generation in 2D stator flow under simplifying assumptions, using Euler and RANS mean flows. Further investigation is needed to validate the RANS case and to fully understand the effect of boundary layers on entropy noise generation. Finally, entropy noise is simulated using Zonal Detached Eddy Simulation (ZDES) in a stator channel in order to investigate 3D and viscous effects on entropy noise. The three-dimensionality of the flow is highlighted and acoustic signals are carefully post-processed, ensuring hydrodynamic perturbations are correctly filtered and boundary reflections are minimised. The closeness of noise levels obtained using CAA and ZDES suggest three-dimensional and viscous effects have a limited impact on the entropy noise generated in turbine stator flow
Książki na temat "Stator simulations"
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Center, Ames Research, red. Three-dimensional Navier-Stokes simulations of turbine rotor-stator interaction. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1988.
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Center, Ames Research, red. Three-dimensional Navier-Stokes simulations of turbine rotor-stator interaction. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1988.
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Boretti, A. A. Three-dimensional Euler time accurate simulations of fan rotor-stator interactions. [Cleveland, Ohio: National Aeronautics and Space Administration, Lewis Research Center, Institute for Computational Mechanics in Propulsion, 1990.
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Boretti, A. A. Three-dimensional Euler time accurate simulations of fan rotor-stator interactions. Cleveland, Ohio: Lewis Research Centre, 1990.
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Lewis Research Center. Institute for Computational Mechanics in Propulsion., red. Three-dimensional Euler time accurate simulations of fan rotor-stator interactions. [Cleveland, Ohio: National Aeronautics and Space Administration, Lewis Research Center, Institute for Computational Mechanics in Propulsion, 1990.
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Boretti, A. A. Three-dimensional Euler time accurate simulations of fan rotor-stator interactions. [Cleveland, Ohio: National Aeronautics and Space Administration, Lewis Research Center, Institute for Computational Mechanics in Propulsion, 1990.
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Federico, Cecconi, red. La società dei beni: Dalla famiglia allo Stato alle imprese private. Torino: Bollati Boringhieri, 2006.
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United States. Army Test and Evaluation Command, red. TECOM, modeling & simulation. [Aberdeen Proving Ground, MD: U.S. Army Test and Evaluation Command, 1994.
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Center, Ames Research, red. Gas-Grain Simulation Facility. [Moffett Field, Calif.]: NASA Ames Research Center, 1993.
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Center, Ames Research, red. Gas-Grain Simulation Facility. [Moffett Field, Calif.]: NASA Ames Research Center, 1993.
Znajdź pełny tekst źródłaCzęści książek na temat "Stator simulations"
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Neuhauser, Magdalena, Francis Leboeuf, Jean-Christophe Marongiu, Etienne Parkinson i Daniel Robb. "Simulations of Rotor–Stator Interactions with SPH-ALE". W Advances in Hydroinformatics, 349–61. Singapore: Springer Singapore, 2013. http://dx.doi.org/10.1007/978-981-4451-42-0_29.
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Song, An, Xiang Luo, Zhongliang He i Jian He. "Numerical Investigation on Flow and Heat Transfer of a Rotor–Stator Cavity with Labyrinth Seal". W Computational and Experimental Simulations in Engineering, 797–814. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-42515-8_56.
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Giangaspero, G., M. Almquist, K. Mattsson i E. van der Weide. "Unsteady Simulations of Rotor Stator Interactions Using SBP-SAT Schemes: Status and Challenges". W Lecture Notes in Computational Science and Engineering, 247–55. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-19800-2_21.
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Feng, Wenzong, Qing Zhang, Zhuoxiang Chen, Jianqun Zhang i Haoyu Wang. "Dynamical Simulation Analysis of Faulty Gearbox in Quay Crane Under Dynamic Load". W Lecture Notes in Mechanical Engineering, 187–99. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-1876-4_15.
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AbstractDynamics simulations with faults can elucidate fault vibration characteristics, yet the vibrational properties of the quay crane lifting gearboxes under dynamic load excitation remain unclear. Based on multi-body dynamics theory, a multi-body dynamical model of the quay crane gearbox is established, simulating dynamic load excitation caused by cables and containers during the operation of a quay crane. The vibration responses under various working conditions and load types of different gear states are analyzed, and the corresponding fault frequency features are extracted by envelope spectrum. Simulations indicate that local gear faults enlarge the amplitude of gearbox vibrations, inducing the phenomenon of gear mesh frequency and its harmonics modulated by gear fault frequency. Based on these studies, a testbed for the quay crane gearbox is constructed. The experiment verifies the accuracy of the dynamic model and reveals that the simulation signal of load-as-dynamic-load is more consistent with reality than static load. The results provide a basis for fault diagnosis of quay crane lifting gearboxes under dynamic load, and can offer simulation data support for intelligent diagnosis models lacking fault samples.
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Wang, Rui, Tong Zhu, Chuang Zhou i Jian-Min Zhang. "LEAP-ASIA-2019 Simulations at Tsinghua University". W Model Tests and Numerical Simulations of Liquefaction and Lateral Spreading II, 399–408. Cham: Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-48821-4_19.
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AbstractThis chapter presents the constitutive model calibration and numerical simulations of centrifuge shaking table tests for LEAP-ASIA-2019, at Tsinghua University. A plasticity model that can provide unified description for the behavior sand at different states under both monotonic and cyclic loading, with focus on the large post-liquefaction shear deformation, is calibrated and used in this study. New undrained cyclic torsional shear test results for Ottawa F65 sand provided in the most recent phase of the LEAP project are used in the calibration process. Typical results for acceleration, excess pore pressure, and displacement for one of the tests are presented in detail, showing that the numerical simulation is able to capture the liquefaction related behavior in the tests well. Comparisons between the simulation and test residual displacement results for the five different tests show conflicting results. The simulations for the two RPI tests under different centrifuge acceleration levels with different stress states and input motion frequencies generally show adequate agreement with test results, exhibiting the constitutive model and numerical simulation method’s wide applicability range. However, the simulation results for the KyU tests are significantly different to the test results.
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Serre, Eric, Patrick Bontoux i Brian Launder. "Studies of Transitional and Turbulent Flows in Rotor-Stator Cavity Using High-Performance Computations". W Direct and Large-Eddy Simulation V, 205–12. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-1-4020-2313-2_22.
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Qi, Jianhui. "Multi-objective Optimisation for Supercritical CO$$_2$$ Radial Inflow Turbine Stator". W Simulation Tools and Methods for Supercritical Carbon Dioxide Radial Inflow Turbine, 197–235. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-2860-4_7.
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Theorell, Axel, i Jörg Stelling. "Microbial Community Decision Making Models in Batch and Chemostat Cultures". W Computational Methods in Systems Biology, 141–58. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-85633-5_9.
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AbstractMicrobial community simulations using genome scale metabolic networks (GSMs) are relevant for many application areas, such as the analysis of the human microbiome. Such simulations rely on assumptions about the culturing environment, affecting if the culture may reach a metabolically stationary state with constant microbial concentrations. They also require assumptions on decision making by the microbes: metabolic strategies can be in the interest of individual community members or of the whole community. However, the impact of such common assumptions on community simulation results has not been investigated systematically. Here, we investigate four combinations of assumptions, elucidate how they are applied in literature, provide novel mathematical formulations for their simulation, and show how the resulting predictions differ qualitatively. Crucially, our results stress that different assumption combinations give qualitatively different predictions on microbial coexistence by differential substrate utilization. This fundamental mechanism is critically under explored in the steady state GSM literature with its strong focus on coexistence states due to crossfeeding (division of labor).
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Negri, Luca, i Andrea Chiarini. "Power Simulation of Communication Protocols with StateC". W Applications of Specification and Design Languages for SoCs, 277–94. Dordrecht: Springer Netherlands, 2006. http://dx.doi.org/10.1007/978-1-4020-4998-9_16.
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Verma, Amar Kumar, P. Spandana, S. V. Padmanabhan i Sudha Radhika. "Quantitative Modeling and Simulation for Stator Inter-turn Fault Detection in Industrial Machine". W Intelligent Computing and Communication, 87–97. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-1084-7_10.
Pełny tekst źródłaStreszczenia konferencji na temat "Stator simulations"
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Stummann, Simon, Daniel Pohl, Peter Jeschke, Hannes Wolf, Alexander Halcoussis i Matthias Franke. "Secondary Flow in Variable Stator Vanes With Penny-Cavities". W ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63771.
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This paper presents a description of Detached Eddy Simulations being carried out on a variable stator vane with a penny-cavity in order to determine the secondary flow phenomena in the main flowpath. Variable stator vanes are common in multi-stage compressors to prevent flow separations on rotor and stator blades at off-design operation points. The bearing of the stators at hub and tip generate unavoidable circular-shaped ring gaps, which are called penny-cavities. The aim of this paper is to determine secondary flow phenomena in variable stator vanes on an annular cascade testbed resulting from the throughflow of the penny-cavities. Reynolds-Averaged-Navier-Stokes simulations and scale resolving Detached-Eddy-Simulations of a variable stator vane with hub penny-cavity were therefore performed using Ansys CFX. The results of these simulations will be compared to corresponding simulations without penny-cavity. The study shows secondary flow phenomena, which are comparable to the interaction of a transverse jet in a free stream. Due to the low momentum ratio of R = 0.5, the jet immediately veers in the direction of the main flow. The typical vortices which develop from a transverse jet in a free stream are identified. The steady RANS simulation shows an asymmetrical counter-rotating vortex pair. A lack of unsteady secondary flow interaction can be seen in the RANS simulations in contrast to the Detached-Eddy-Simulations, which resolve large turbulent scales. Hence an interaction between the counter-rotating vortex pair and the unsteady shear layer vortices in the stator is visible. In the Detached Eddy Simulations the counter-rotating vortex pair is superimposed by the unsteady shear-layer vortices. The vortices produce significant additional mixing losses, which will be shown in detail. By comparing simulations with and without penny-cavity, the penny-cavity losses are quantified. In conclusion, this paper will help design engineers become more aware of the significance of the penny-cavity with variable stator vanes.
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Feng, Dakui, Hang Zhang, Yue Sun, Qing Wang i Xiaofei Hu. "Studies About Design of Rear Stator of Ducted Propeller Using CFD". W ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96020.
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Abstract Ducted propeller designs are becoming more popular because of their high efficiency, resistance to cavitation and low radiated noise. In this paper, unsteady RANS simulations are carried out for the design of rear stators for ducted propeller to improve its hydrodynamic performance. The design of rear stator is carried out based on the wake field behind propellers. The two-dimensional airfoil modified from NACA4603 is studied to obtain the angle of attack that makes thrust on stators maximum. The analyses are performed at different angles of attack, using commercial computational fluid dynamics (CFD) solver STAR-CCM+ to solve URANS equations. URANS equations are discretized by finite volume method and solved by PISO algorithm. Simulations have been made using unstructured grid with mesh moving technique. The simulation results indicate that the total thrust coefficient and efficiency of modified ducted propeller have been improved by 7.32% and 5.72% respectively compared with the parent one. The simulation results show that the design method is reasonable and feasible.
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Galpin, Paul, Thorsten Hansen, Georg Scheuerer, Ryan Kelly, Adam Hickman, Aleksandar Jemcov i Scott C. Morris. "Validation of Transonic Axial Compressor Stage Unsteady-State Rotor-Stator Simulations". W ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64786.
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The paper describes the validation of steady-state and unsteady CFD simulations against experimental data from a single-stage, transonic axial compressor stage. The experimental data include overall compressor performance, high-resolution traverses of total pressure and total temperature, and unsteady-state total pressure measurements downstream of the rotor. Various numerical rotor-stator interaction methods were applied across the operational speedline. These included a steady-state method mixing plane, and a transient time inclination method that accounts for the unsteady rotor to stator pitch change. Best practice procedures were employed to assess and quantify the sensitivity of the simulations to numerical error like mesh and timestep size, turbulence model error and systematic errors related to tip gap, and steady-state or unsteady-state flow assumptions. The effect of turbulence on the mean flow is modelled by a URANS approach based on the SST model and its extensions for laminar-turbulent transition and reattachment prediction. The complex unsteady flow interactions between the rotor and stator were validated against steady-state and unsteady experimental data. The compressor flow is explained in detail including transonic flow features like shock boundary layer interactions. Comparisons are made between the various rotor-stator interaction simulation methods and the experimental data.
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RAI, MAN, i NATERI MADAVAN. "Multi-airfoil Navier-Stokes simulations of turbine rotor-stator interaction". W 26th Aerospace Sciences Meeting. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1988. http://dx.doi.org/10.2514/6.1988-361.
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Zhou, Haowei, Pengcheng Du i Fangfei Ning. "Time step criteria for rotor-stator unsteady simulations of turbomachinery". W GPPS Chania24. GPPS, 2024. http://dx.doi.org/10.33737/gpps24-tc-065.
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With the rapid improvement of computing power, unsteady Reynolds-Averaged Navier-Stokes (U-RANS) solvers are increasingly used to get a deeper comprehension of the rotor-stator unsteady flows inside turbomachinery. The dual-time stepping method is adopted in most U-RANS solvers and the determination of the optimal size of physical time step is a crucial procedure for rotor-stator U-RANS simulations, and it is the primary purpose of this paper. The criteria for determining the size of physical time step for rotor-stator interactions with and without filtering mixing plane were proposed through theoretical analysis. For conventional no-filtering U-RANS simulations, the number of physical time steps is determined by the number of circumferential grid points and the characteristic propagation velocity of flow. While for U-RANS simulations adopting the filtering mixing plane method, the number of retained harmonics through the filtering mixing plane plays an important role. Then, three numerical cases including subsonic rotor-stator interactions, IGV-rotor interactions and rotor-stator interactions coupled with inlet distortion, were carried out to verify the effectiveness of proposed criteria. The results showed that the requirement of time step independence can be satisfied when the number of physical time steps exceeds the number estimated by the criteria, thus the effectiveness of the proposed criteria has been verified.
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Graf, Martin B., i Om P. Sharma. "Effects of Downstream Stator Pressure Field on Upstream Rotor Performance". W ASME 1996 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-gt-507.
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Results of numerical simulations conducted for a high pressure compressor rotor with two different levels of tip clearance are presented. A three-dimensional, steady, Reynolds-Averaged Navier-Stokes code was utilized to perform the computations. The simulations were executed over a range of flow coefficients by specifying different axisymmetric radial profiles in static pressure downstream of the rotor. In this manner, the effect of the downstream stator row was approximated using a simple, circumferentially averaged, radial pressure profile as the boundary condition behind the rotor. The back pressure profiles utilized were those deduced from inviscid flow computations for two different stator designs: (1) a conventional radial stator, and (2) a three-dimensional “bowed” stator. Results of the rotor simulations with nominal tip clearance show that the boundary condition induced by the bowed stator causes a 2% decrease in rotor pressure rise capability, and a 9% increase in rotor loss as compared with the conventional stator. In addition, as the tip clearance is increased to twice the nominal value, the rotor loss grows at a rate 25% higher for the rotor subjected to the bowed stator pressure profile. Accompanying this is a dramatic reduction in rotor speedline slope and pressure rise capability. Analysis of the simulations shows these effects to be linked to the response of the rotor tip clearance vortex to the exit pressure profile set by the downstream stator. These results indicate the need to accurately model the effects of the radial variation in static pressure imposed by the downstream airfoil rows.
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Blaszczak, Jaroslaw R. "Efficiency Improvement and Noise Reduction Through Stator-Stator Clocking Effect of a Two-Stage Turbine". W ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68833.
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The objective of the presented test program was to further experimentally investigate vane-indexing effect influence on the performance, noise and vibration of two-stage low-pressure turbine. Keeping the inlet conditions strictly constant during the tests, two turbine stages were experimentally investigated. Herein, some flow measurement results and the external characteristics for different circumferential positions of the stator vanes are described. Comparisons were made with numerical simulation and they showed good agreement. Experimental data and numerical simulations of stator vane surface pressures are presented to determine how the flow phenomena were affected by indexing of the airfoils for two cases: for nominal rotational speed and for off-design turbine conditions. In addition, correlation to acoustic noise and machine vibration level is presented. They have been found to be clocking dependent. The experimental investigations have been carried out on a two-stage turbine research facility at the Institute of Turbomachinery of the Technical University of Lodz, Poland.
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Reinmöller, U., B. Stephan, S. Schmidt i R. Niehuis. "Clocking Effects in a 1.5 Stage Axial Turbine: Steady and Unsteady Experimental Investigations Supported by Numerical Simulations". W ASME Turbo Expo 2001: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-gt-0304.
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The interaction between rotor and stator airfoils in a multistage turbomachine causes an inherently unsteady flow field. In addition, different relative circumferential positions of several stator rows and rotor rows, respectively, have an influence on the flow behaviour in terms of loss generation, energy transport and secondary flow. The objective of the presented study is to investigate the effects of stator airfoil clocking on the performance of an 1-1/2 stage axial cold air turbine. The investigated axial turbine consists of two identical stators. The low aspect ratio of the blades and their prismatic design leads to a three-dimensional outlet flow with a high degree of secondary flow phenomena. Nevertheless, the small axial gaps between the blade rows are responsible for strong potential flow interaction with the radial wake regions in the measurement planes. Consequently, parts of the wakes of the first stator are clearly detected in the rotor outlet flow. To give an overview of the time-averaged flow field, measurements with pneumatic probes are conducted behind each blade row at ten different clocking-positions of the second stator. Further, an optimised clocking position was found due to a minimum in pressure loss behind the 2nd stator. The unsteady measurements are carried out with hot-wire probes for three selected stator-stator positions. Animations of selected flow properties show the influence of different circumferential positions of the second stator on the unsteady flow behaviour and secondary flow field. In addition and compared with experimental results three-dimensional unsteady viscous flow computations are performed.
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Sato, Masanori, Takashi Nagumo, Kazuyuki Toda i Makoto Yamamoto. "Computation of Rotor/Stator Interaction With Hydrogen-Fuelled Combustion". W ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45618.
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For the next-generation aircraft, a new propulsion system using hydrogen fuel has been proposed. In the present system, hydrogen fuel injected from a stator surface combusts in the turbine passages, accordingly, the conventional combustor can be cut out. The advantage of this system is that we can design a lighter and smaller engine with low emission. We have demonstrated the realizability of this system by using the cycle analysis and the numerical simulations. Through the previous studies, it was confirmed that the rotor/stator interaction has to be investigated, because the hydrogen combustion phenomena within the stator passage is so complex, and thus it would highly affect the rotor performance. In this paper, we focus on the rotor/stator interaction for the detailed investigation of realizability of this system. The 2- and 3-dimensional numerical simulations are performed for a single stage turbine with hydrogen-fuelled combustion. In the 2-dimensional study, the effects of the injection position and injection rate on the flow structure, the static temperature over the blades, and the blade performance are investigated. Furthermore, 3-dimensional numerical simulation is performed. The general aspect of 3-dimensional flow field is demonstrated, and the effect of hydrogen combustion on the components of turbine, for example hub, tip and blade, are investigated.
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Dorney, D. J., D. L. Sondak, P. G. A. Cizmas, V. E. Saren i N. M. Savin. "Full-Annulus Simulations of Airfoil Clocking in a 1-1/2 Stage Axial Compressor". W ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-023.
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Axial compressors have inherently unsteady flow fields because of relative motion between rotor and stator airfoils. This relative motion leads to viscous and inviscid (potential) interactions between blade rows. As the number of stages increases in a turbomachine, the buildup of convected wakes can lead to progressively more complex wake/wake and wake/airfoil interactions. Variations in the relative circumferential positions of stators or rotors can change these interactions, leading to different unsteady forcing functions on airfoils and different compressor efficiencies. In addition, as the Mach number increases the interaction between blade rows can be intensified due to potential effects. It has been shown, both experimentally and computationally, that airfoil clocking can be used to improve the efficiency and reduce the unsteadiness in multiple-stage axial turbomachines with equal blade counts in alternate blade rows. While previous investigations have provided an improved understanding of the physics associated with airfoil clocking, more research is needed to determine if airfoil clocking is viable for use in modern gas-turbine compressors. This paper presents the results of a combined experimental/computational research effort to study the physics of airfoil clocking in a high-speed axial compressor. Computational simulations have been performed for eight different clocking positions of the stator airfoils in a 1-1/2 stage high-speed compressor. To accurately model the experimental compressor, full-annulus simulations were conducted using 34 IGV, 35 rotor and 34 stator airfoils. It is common practice to modify blade counts to reduce the computational work required to perform turbomachinery simulations, and this approximation has been made in all computational clocking studies performed to date. A simulation was also performed in the present study with 1 inlet guide vane, 1 rotor airfoil, and 1 stator airfoil to model blade rows with 34 airfoils each in order to examine the effects of this approximation. Time-averaged and unsteady data (including performance and boundary layer quantities) were examined. The predicted results indicate that simulating the full annulus gives better qualitative agreement with the experimental data, as well as more accurately modeling the interaction between adjacent blade rows.
Raporty organizacyjne na temat "Stator simulations"
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Zhu, Minjie, i Michael Scott. Two-Dimensional Debris-Fluid-Structure Interaction with the Particle Finite Element Method. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, kwiecień 2024. http://dx.doi.org/10.55461/gsfh8371.
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In addition to tsunami wave loading, tsunami-driven debris can cause significant damage to coastal infrastructure and critical bridge lifelines. Using numerical simulations to predict loads imparted by debris on structures is necessary to supplement the limited number of physical experiments of in-water debris loading. To supplement SPH-FEM (Smoothed Particle Hydrodynamics-Finite Element Method) simulations described in a companion PEER report, fluid-structure-debris simulations using the Particle Finite Element Method (PFEM) show the debris modeling capabilities in OpenSees. A new contact element simulates solid to solid interaction with the PFEM. Two-dimensional simulations are compared to physical experiments conducted in the Oregon State University Large Wave Flume by other researchers and the formulations are extended to three-dimensional analysis. Computational times are reported to compare the PFEM simulations with other numerical methods of modeling fluid-structure interaction (FSI) with debris. The FSI and debris simulation capabilities complement the widely used structural and geotechnical earthquake simulation capabilities of OpenSees and establish the foundation for multi-hazard earthquake and tsunami simulation to include debris.
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Allen, Luke, Robert Haehnel i Yonghu Wenren. South Pole Station snowdrift model. Engineer Research and Development Center (U.S.), sierpień 2022. http://dx.doi.org/10.21079/11681/44943.
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The elevated building at Scott-Amundsen South Pole Station was designed to mitigate the effects of windblown snow on it and the surrounding infrastructure. Because the elevation of the snow surface increases annually, the station is periodically lifted on its support columns to maintain its design height above the snow surface. To assist with planning these lifts, this effort developed a computational model to simulate snowdrift formation around the elevated building. The model uses computational fluid dynamics methods and synthetic wind record generation derived from statistical analysis of meteorological data. Simulations assessed the impact of several options for the lifting operation on drifts surrounding the elevated building. Simulation results indicate that raising the eastern-most building section (Pod A), or the entire station all at once, can reduce drift accumulation rates over the nearby arches structures. Long-term analyses, spanning 5–6 years, determine whether an equilibrium drift condition may be reached after a long period of undisturbed drift development. These simulations showed that after about 6 years, the rate of growth of the upwind drift slows, appearing to approach an equilibrium condition. However, the adjacent drifts were still increasing in depth at a roughly linear rate, indicating that equilibrium for those drifts was still several seasons away.
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Murray, Trevor, i Timothy Jacobs. PR-457-16200-R01 Control of Vented Methane Emissions from Integral Compressor Engines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), kwiecień 2018. http://dx.doi.org/10.55274/r0011475.
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At natural gas pipeline compressor stations, methane emissions from compressor and engine crankcases are often vented directly into the atmosphere. There may be advantages to capturing these emissions and using them to offset fuel usage and / or decrease the overall carbon footprint of such a typical compressor station. This study evaluates the feasibility of directing such captured emissions into the intake of the compressor engine and subsequently combusting the methane emissions into carbon dioxide and water. Although seemingly an obvious or trivial solution, there are in fact several challenges and issues that must be considered to evaluate if such a scheme is a reasonable course of action for compressor station methane emissions reduction. The study relies on both extensive literature review and model-based engine simulations to determine the feasibility of rebreathing crankcase gases in pursuit of reducing compressor station methane emissions. The conclusions of the study are limited to the crankcase vent rebreathing into the air intake of large bore, natural gas, 2-stroke engines. The model-based engine simulations require detailed physical geometry of the subject engines as well as knowledge of basic engine operating parameters (e.g., fuel flow, air flow, and fuel composition). The simulation is based on the experimental facility located at Colorado State University, which is a 4-cylinder Cooper-Bessemer GMV-4. One of the important parameters needing to be known is the gas composition of both compressor and engine crankcases. It is extremely difficult to determine the composition of the engine crankcase gases, since the composition depends on a large variety of parameters. For this study, the gases from the compressor crankcase are modeled as methane (i.e., pipeline gas), and the gases from the engine crankcase are modeled as products of combustion with two different levels methane concentration (1500 ppm and 3000 ppm). A sensitivity analysis is performed, and the observed pressure traces from the model-based engine simulation show that the engine performance is not affected by the addition of rebreathed gases. This insensitivity mainly results from the very small rebreathed flow rates compared to the air intake, and the adjustments made on engine parameters, boost pressure and fuel injection rate, to keep trapped equivalence ratio (TER) and the energy delivery rate the same.
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Johnston, Morgan, Kiara Pazan, Yan Ding, Mary Allison i Sung-Chan Kim. Surge analysis in Mobile Harbor, Alabama : ship-simulation report. Engineer Research and Development Center (U.S.), wrzesień 2023. http://dx.doi.org/10.21079/11681/47596.
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A navigation channel improvement study for Mobile Harbor was conducted by the US Army Corps of Engineers, Mobile District (CESAM), and the Alabama State Port Authority. The US Army Engineer Research and Development Center (ERDC) assisted CESAM in assessing channel modifications using ERDC’s Ship/Tow Simulator through a Feasibility Level Screening Simulation study in 2017 and through a more comprehensive ship-simulation study in 2020. During the 2020 study, a safety concern was identified related to vessel interactions between a transiting vessel passing docked vessels at the McDuffie Coal Terminal located along the main federal channel. In the previous ship-simulation studies, the docked vessels were represented as targets, which means the ships are visually represented but no hydrodynamic interaction is captured. To fully assess this interaction, a surge-analysis study was completed in 2022 that used hydrodynamic models to represent docked vessels with representative mooring conditions. This study assessed several proposed navigation channel expansions across from the McDuffie Coal Terminal over the course of six testing days with four pilots. Assessment of the proposed modifications was accomplished through analysis of ship simulations completed by experienced local pilots, track plots, run sheets, and final pilot questionnaires.
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Grenade, Kari, Allan Wright i Ankie Scott-Joseph. Fiscal Rules: Towards a New Paradigm for Fiscal Sustainability in Small States. Inter-American Development Bank, luty 2017. http://dx.doi.org/10.18235/0011783.
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This study contends that Caribbean countries cannot adequately surmount their fiscal and debt challenges in the absence of binding rules that are geared toward entrenching fiscal discipline, curbing fiscal procyclicality, and improving budget transparency and credibility. Distilling global lessons and taking due cognizance of Caribbean countries' idiosyncrasies, the paper explores key technical, operational and institutional issues in the design, implementation, and monitoring of fiscal rules that might be relevant for Caribbean countries that currently do not have legislated rules. Results from simulations carried out to determine welfare effects and the extent of volatility of key macroeconomic variables under various fiscal rules scenarios suggest that of the different types of simulated fiscal rules, expenditure rules perform best in terms of reducing macroeconomic volatility, and in that regard, appear to be the most welfare-enhancing. This is believed to be the first study to carry out such a simulation exercise for Caribbean countries. The findings of the study evince useful insights for policymakers on how to improve the design and conduct of fiscal policy for better fiscal and, by extension, development outcomes.
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Farhi, Edward, i Hartmut Neven. Classification with Quantum Neural Networks on Near Term Processors. Web of Open Science, grudzień 2020. http://dx.doi.org/10.37686/qrl.v1i2.80.
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We introduce a quantum neural network, QNN, that can represent labeled data, classical or quantum, and be trained by supervised learning. The quantum circuit consists of a sequence of parameter dependent unitary transformations which acts on an input quantum state. For binary classification a single Pauli operator is measured on a designated readout qubit. The measured output is the quantum neural network’s predictor of the binary label of the input state. We show through classical simulation that parameters can be found that allow the QNN to learn to correctly distinguish the two data sets. We then discuss presenting the data as quantum superpositions of computational basis states corresponding to different label values. Here we show through simulation that learning is possible. We consider using our QNN to learn the label of a general quantum state. By example we show that this can be done. Our work is exploratory and relies on the classical simulation of small quantum systems. The QNN proposed here was designed with near-term quantum processors in mind. Therefore it will be possible to run this QNN on a near term gate model quantum computer where its power can be explored beyond what can be explored with simulation.
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Henager, Charles H., Fei Gao, Shenyang Y. Hu, Guang Lin, Eric J. Bylaska i Nicholas Zabaras. Simulating Interface Growth and Defect Generation in CZT – Simulation State of the Art and Known Gaps. Office of Scientific and Technical Information (OSTI), listopad 2012. http://dx.doi.org/10.2172/1118122.
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Murphy, Richard D. Work Station for Particle Simulations of Plasmas. Fort Belvoir, VA: Defense Technical Information Center, sierpień 1995. http://dx.doi.org/10.21236/ada299086.
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de Melo Kort-Kamp, Wilton Junior, Diego Alejandro Roberto Dalvit, Sinhara Rishi Malinda Silva i Jeremiah Joseph Rushton. Modeling and Simulation of Static Metasurfaces. Office of Scientific and Technical Information (OSTI), luty 2019. http://dx.doi.org/10.2172/1493539.
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Rambo, P. W., i J. Denavit. Monte Carlo simulations of solid-state photoswitches. Office of Scientific and Technical Information (OSTI), wrzesień 1995. http://dx.doi.org/10.2172/123236.
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