Artículos de revistas: "Rotor walks"

1

Angel, Omer y Alexander E. Holroyd. "Rotor Walks on General Trees". SIAM Journal on Discrete Mathematics 25, n.º 1 (enero de 2011): 423–46. http://dx.doi.org/10.1137/100814299.

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2

Huss, Wilfried y Ecaterina Sava-Huss. "Range and Speed of Rotor Walks on Trees". Journal of Theoretical Probability 33, n.º 3 (20 de abril de 2019): 1657–90. http://dx.doi.org/10.1007/s10959-019-00904-1.

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3

Groiseau, Caspar, Alexander Wagner, Gil Summy y Sandro Wimberger. "Impact of Lattice Vibrations on the Dynamics of a Spinor Atom-Optics Kicked Rotor". Condensed Matter 4, n.º 1 (14 de enero de 2019): 10. http://dx.doi.org/10.3390/condmat4010010.

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We investigate the effect of amplitude and phase noise on the dynamics of a discrete-time quantum walk and its related evolution. Our findings underline the robustness of the motion with respect to these noise sources, and can explain the stability of quantum walks that has recently been observed experimentally. This opens the road to measure topological properties of an atom-optics double kicked rotor with an additional internal spin degree of freedom.

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4

Florescu, Laura, Shirshendu Ganguly, Lionel Levine y Yuval Peres. "Escape Rates for Rotor Walks in $\mathbb{Z}^d$". SIAM Journal on Discrete Mathematics 28, n.º 1 (enero de 2014): 323–34. http://dx.doi.org/10.1137/130908646.

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5

Dereniowski, Dariusz, Adrian Kosowski, Dominik Pająk y Przemysław Uznański. "Bounds on the cover time of parallel rotor walks". Journal of Computer and System Sciences 82, n.º 5 (agosto de 2016): 802–16. http://dx.doi.org/10.1016/j.jcss.2016.01.004.

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6

Kaiser, Robin y Ecaterina Sava-Huss. "Random rotor walks and i.i.d. sandpiles on Sierpiński graphs". Statistics & Probability Letters 209 (junio de 2024): 110090. http://dx.doi.org/10.1016/j.spl.2024.110090.

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7

Chan, Swee Hong. "Rotor Walks on Transient Graphs and the Wired Spanning Forest". SIAM Journal on Discrete Mathematics 33, n.º 4 (enero de 2019): 2369–93. http://dx.doi.org/10.1137/18m1217139.

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8

DOERR, BENJAMIN y TOBIAS FRIEDRICH. "Deterministic Random Walks on the Two-Dimensional Grid". Combinatorics, Probability and Computing 18, n.º 1-2 (marzo de 2009): 123–44. http://dx.doi.org/10.1017/s0963548308009589.

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Jim Propp's rotor–router model is a deterministic analogue of a random walk on a graph. Instead of distributing chips randomly, each vertex serves its neighbours in a fixed order. We analyse the difference between the Propp machine and random walk on the infinite two-dimensional grid. It is known that, apart from a technicality, independent of the starting configuration, at each time the number of chips on each vertex in the Propp model deviates from the expected number of chips in the random walk model by at most a constant. We show that this constant is approximately 7.8 if all vertices serve their neighbours in clockwise or order, and 7.3 otherwise. This result in particular shows that the order in which the neighbours are served makes a difference. Our analysis also reveals a number of further unexpected properties of the two-dimensional Propp machine.

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9

Pham, Trung Van. "Orbits of rotor-router operation and stationary distribution of random walks on directed graphs". Advances in Applied Mathematics 70 (septiembre de 2015): 45–53. http://dx.doi.org/10.1016/j.aam.2015.06.006.

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10

Klasing, Ralf, Adrian Kosowski, Dominik Pająk y Thomas Sauerwald. "The multi-agent rotor-router on the ring: a deterministic alternative to parallel random walks". Distributed Computing 30, n.º 2 (17 de septiembre de 2016): 127–48. http://dx.doi.org/10.1007/s00446-016-0282-y.

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11

Ketterer, Philip, Elena M. Willner y Hendrik Dietz. "Nanoscale rotary apparatus formed from tight-fitting 3D DNA components". Science Advances 2, n.º 2 (febrero de 2016): e1501209. http://dx.doi.org/10.1126/sciadv.1501209.

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We report a nanoscale rotary mechanism that reproduces some of the dynamic properties of biological rotary motors in the absence of an energy source, such as random walks on a circle with dwells at docking sites. Our mechanism is built modularly from tight-fitting components that were self-assembled using multilayer DNA origami. The apparatus has greater structural complexity than previous mechanically interlocked objects and features a well-defined angular degree of freedom without restricting the range of rotation. We studied the dynamics of our mechanism using single-particle experiments analogous to those performed previously with actin-labeled adenosine triphosphate synthases. In our mechanism, rotor mobility, the number of docking sites, and the dwell times at these sites may be controlled through rational design. Our prototype thus realizes a working platform toward creating synthetic nanoscale rotary motors. Our methods will support creating other complex nanoscale mechanisms based on tightly fitting, sterically constrained, but mobile, DNA components.

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12

Tanabe, Yasutada, Masahiko Sugiura, Takashi Aoyama, Hideaki Sugawara, Shigeru Sunada, Koichi Yonezawa y Hiroshi Tokutake. "Multiple Rotors Hovering Near an Upper or a Side Wall". Journal of Robotics and Mechatronics 30, n.º 3 (20 de junio de 2018): 344–53. http://dx.doi.org/10.20965/jrm.2018.p0344.

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The influence of walls on the performance of multiple rotor type drones is numerically simulated. With the current wide-spread applications of autonomously flyable UAVs, there are potential needs to use the drones for inspections and observation near various structures, such as buildings and bridges. The flow fields around multiple rotors are influenced significantly by the existence of an upper or a side wall, so that the thrust, required torque, and other forces and moments are changed. It is found that when a rotor approaches an upper wall, as the distance between the rotor and the upper wall is less than a diameter of the rotor, the thrust suddenly increases, which causes the rotors to collide with the upper wall. When an isolated rotor is operated near a side wall, the thrust decreases and a rolling moment appears to tilt the rotor toward the wall as the distance becomes shorter. For a multiple rotor drone near a side wall, the rotors have different distances from the wall, which causes the whole aircraft tilts toward the wall. From the perspective of safety operations, the multi-rotor drone should be kept away from both the upper wall and the side wall at a distance of at least 1.5 times of the rotor diameter to prevent unexpected motions of the aircraft caused by the wall during hovering flight.

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13

Wilson, J. "An Experimental Determination of Losses in a Three-Port Wave Rotor". Journal of Engineering for Gas Turbines and Power 120, n.º 4 (1 de octubre de 1998): 833–42. http://dx.doi.org/10.1115/1.2818476.

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Wave rotors, used in a gas turbine topping cycle, offer a potential route to higher specific power and lower specific fuel consumption. In order to calculate this potential realistically, a knowledge of the loss mechanisms is required. The experiment reported here was designed as a statistical experiment to identify the losses due to finite passage opening time, friction, and leakage, using a three-port, flow divider, wave rotor cycle. Incidence loss was also found to be important. Rotors of 12 in. diameter were used, with two different lengths, 9 in. and 18 in., and two different passage widths, 0.25 in. and 0.54 in., in order to vary friction and opening time. To vary leakage, moveable end walls were provided so that the rotor to end wall gap could be adjusted. The experiment is described, and the results are presented, together with a parametric fit to the data.

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14

Suryavamshi, N. y B. Lakshminarayana. "Numerical Prediction of Wakes in Cascades and Compressor Rotors Including the Effects of Mixing: Part II—Rotor Passage Flow and Wakes Including the Effects of Spanwise Mixing". Journal of Turbomachinery 114, n.º 3 (1 de julio de 1992): 617–26. http://dx.doi.org/10.1115/1.2929186.

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The results of a numerical investigation to predict the flow field including wakes and mixing in axial flow compressor rotors has been presented in this paper. The wake behavior in a moderately loaded compressor rotor has been studied numerically using a three-dimensional incompressible Navier–Stokes solver with a high Reynolds number form of the k–ε turbulence model. The equations are solved using a time-dependent implicit technique. The agreement between the measured data and the predictions is good, including the blade boundary layer profiles, wake mean velocity profiles, and decay. The ability of the pseudocompressibility scheme to predict the entire flow field including the near and far wake profiles and its decay characteristics, effect of loading, and the viscous losses of a three-dimensional rotor flow field has been demonstrated. An analysis of the passage-averaged velocities and the pressure coefficients shows that the mixing in the downstream regions away from the hub and annulus walls is dominated by wake diffusion. In regions away from the walls, the radial mixing is predominantly caused by the transport of mass, momentum, and energy by the radial component of velocity in the wake.

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15

Huss, Wilfried, Lionel Levine y Ecaterina Sava-Huss. "Interpolating between random walk and rotor walk". Random Structures & Algorithms 52, n.º 2 (26 de noviembre de 2017): 263–82. http://dx.doi.org/10.1002/rsa.20747.

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16

Tamborrino, Antonia, Claudio Perone, Gianluca Veneziani, Antonio Berardi, Roberto Romaniello, Maurizio Servili y Alessandro Leone. "Experimental Investigation of a New Modular Crusher Machine Developed for Olive Oil Extraction Plants". Foods 11, n.º 19 (30 de septiembre de 2022): 3035. http://dx.doi.org/10.3390/foods11193035.

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The crushing system is crucial in the virgin olive oil (VOO) mechanical extraction process. The use of different crusher machines can highly influence the quality of the final product, mainly due to the phenolic and volatile content responsible for VOO sensory and health properties. An experimental investigation was conducted to evaluate the effect of the geometric features of a new model of crusher machine for olives. The crusher machine consists of interchangeable rotors: a rotor with hammers and a rotor with knives. The evaluation was carried out with the same fixed grid in stainless steel with 6 mm diameter circular holes. An evaluation was carried out on the impact of the crusher tools on the pit particle size and on the distribution of energy and temperature. The performance of the plant was also assessed in terms of process efficiency and olive oil quality. The results showed that the specific energy released by the tool per unit of product, calculated through both energy conservation and comminution theory, is about 25–27% higher in the case of hammers. Since the impact energy is mainly dissipated in the product as heat, the temperature reached during milling operations with the hammer crusher was also higher by the same percentage with respect to the knife crusher. This has important consequences on the quality of the product: the new knife rotor used in the crushing phase produced an improvement in VOO quality, relating mainly to sensory attributes and the health-enhancing properties of the final product. The ability of the crusher to break cell walls and vacuoles, thus releasing the oil contained therein, is comparable for the two different rotors.

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17

Shen, Zhe y Takeshi Tsuchiya. "Cat-Inspired Gaits for a Tilt-Rotor—From Symmetrical to Asymmetrical". Robotics 11, n.º 3 (13 de mayo de 2022): 60. http://dx.doi.org/10.3390/robotics11030060.

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Among the tilt-rotors (quadrotors) developed in recent decades, Ryll’s model with eight inputs (four magnitudes of thrusts and four tilting angles) attracted great attention. Typical feedback linearization maneuvers all of the eight inputs with a united control rule to stabilize this tilt-rotor. Instead of assigning the tilting angles by the control rule, the recent research predetermines the tilting angles and leaves the magnitudes of thrusts with the only control signals. These tilting angles are designed to mimic the cat-trot gait while avoiding the singular decoupling matrix in feedback linearization. To complete the discussions of the cat-gait inspired tilt-rotor gaits, this research addresses the analyses on the rest of the common cat gaits, walk, run, transverse gallop, and rotary gallop. It is found that the singular decoupling matrix exists in walk gait, transverse gallop gait, and rotary gallop gait; the decoupling matrix can hardly be guaranteed to be invertible analytically. Further modifications (scaling) are conducted to these three gaits to accommodate the application of feedback linearization; the acceptable attitudes, leading to invertible decoupling matrix, for each scaled gait are evaluated in the roll-pitch diagram. The modified gaits with different periods are then applied to the tilt-rotor in tracking experiments, in which the references are uniform rectilinear motion and uniform circular motion with or without the equipment of the modified attitude-position decoupler. All the experiments are simulated in Simulink, MATLAB. The result shows that these gaits, after modifications, are feasible in tracking references, especially for the cases equipped with the modified attitude-position decoupler.

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18

Laura Florescu, Lionel Levine y Yuval Peres. "The Range of a Rotor Walk". American Mathematical Monthly 123, n.º 7 (2016): 627. http://dx.doi.org/10.4169/amer.math.monthly.123.7.627.

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19

Prothin, S., C. Fernandez Escudero, N. Doué y T. Jardin. "Aerodynamics of MAV rotors in ground and corner effect". International Journal of Micro Air Vehicles 11 (enero de 2019): 175682931986159. http://dx.doi.org/10.1177/1756829319861596.

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The work presented in this paper is part of a project called ARChEaN (Aerodynamic of Rotors in Confined ENvironment) whose objective is to study the interactions of a micro drone rotor with its surroundings in the case of flight in enclosed environments such as those encountered, for example, in archeological exploration of caves. To do so the influence of the environment (walls, ground, ceiling, etc) on the rotor’s aerodynamic performance as well as on the flow field between the rotor and the surroundings is studied. This paper focuses on two different configurations, flight near the ground and flight near a corner (wall and ground), and the results are analyzed and compared to a general free flight case (i.e. far away from any obstacle). In order to carry out this analysis both numerical and experimental approaches are conducted. The objective is to validate the numerical model with the results obtained experimentally and to benefit from the advantages of both approaches in terms of flow analysis. This research work will provide knowledge on how to operate these systems as to minimize the possible negative environment disturbances, reduce power consumption and predict the micro drone’s behaviour during enclosed flights.

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20

Delvecchio, Michele, Francesco Petiziol y Sandro Wimberger. "Resonant Quantum Kicked Rotor as A Continuous-Time Quantum Walk". Condensed Matter 5, n.º 1 (11 de enero de 2020): 4. http://dx.doi.org/10.3390/condmat5010004.

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We analytically investigate the analogy between a standard continuous-time quantum walk in one dimension and the evolution of the quantum kicked rotor at quantum resonance conditions. We verify that the obtained probability distributions are equal for a suitable choice of the kick strength of the rotor. We further discuss how to engineer the evolution of the walk for dynamically preparing experimentally relevant states. These states are important for future applications of the atom-optics kicked rotor for the realization of ratchets and quantum search.

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21

Papoyan, Vl V., V. S. Poghosyan y V. B. Priezzhev. "Spiral structures in the rotor-router walk". Journal of Statistical Mechanics: Theory and Experiment 2016, n.º 4 (20 de abril de 2016): 043207. http://dx.doi.org/10.1088/1742-5468/2016/04/043207.

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22

Ahmed, Noor A. y K. J. Netto. "Computer Aided Design and Manufacture of a Novel Vertical Axis Wind Turbine Rotor with Winglet". Applied Mechanics and Materials 607 (julio de 2014): 581–87. http://dx.doi.org/10.4028/www.scientific.net/amm.607.581.

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In this paper the computer aided design and manufacture of a rot with winglet for performance enhancement of a vertical axis wind turbine is presented. Both computer numerical control milling and rapid prototyping have been used in the manufacture of the rotor. The rotor was then tested for performance using the large wind tunnel of the Aerodynamics laboratory of University of New South Wales. The results show substantial improvement of the rotor with the winglets installed.

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23

Papoyan, Vl V., V. S. Poghosyan y V. B. Priezzhev. "Rotor-router walk on a semi-infinite cylinder". Journal of Statistical Mechanics: Theory and Experiment 2016, n.º 7 (28 de julio de 2016): 073209. http://dx.doi.org/10.1088/1742-5468/2016/07/073209.

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24

Tran, Ngoc-Tien y Duc-Minh Nguyen. "Analysis of flow characteristics of cylindrical and helical type multi-lobe roots blower". EUREKA: Physics and Engineering, n.º 1 (19 de enero de 2023): 67–75. http://dx.doi.org/10.21303/2461-4262.2023.002578.

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Roots blower is a positive displacement machine that has the advantage of a larger flow than conventional blowers. Roots blowers are widely used in industrial production such as chemicals, food, medical, etc. However, during actual operation, this type of machine often achieves low performance. One of the issues that greatly affect performance is the flow characteristics of the blower. Flow characteristics include factors related to flow rate, pressure, and flow phenomena in the blower chamber. Flow characteristic analysis is a complex problem in hydraulic machines. Flow analysis helps to investigate the motion of the flow to design high-performance machines. This study uses a mathematical model of gear theory to design the rotor profile with cylindrical and helical lobes of the multi-lobe Roots blower. The rotor profile is formed on the principle that the ellipse rolls without slipping on the base circle. On the basis of the mathematical model of the rotor profile, the paper compares the flow rate and pressure characteristics of the two blowers. The fluid dynamics analysis model was built on ANSYS software. The structural grid model is also built to increase the computational efficiency of the mathematical model. The lobes are embedded and rotated in the blower chamber. The results show that with the same radial and axial dimensions, the cylindrical lobe has a larger flow. However, the helical lobe has a more stable flow quality than the cylindrical lobe (15.2 % less flow fluctuation). In terms of pressure, the helical lobe type has a higher pressure than the cylindrical lobe type. In addition, the helical lobe type also reduces the influence of eddy currents acting on the blower chamber walls and rotors. That results in increased blower efficiency. The results of the paper will be a reliable basis for reducing time in the development of multi-lobe Roots blowers with high performance

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25

Bohn, D., E. Deuker, R. Emunds y V. Gorzelitz. "Experimental and Theoretical Investigations of Heat Transfer in Closed Gas-Filled Rotating Annuli". Journal of Turbomachinery 117, n.º 1 (1 de enero de 1995): 175–83. http://dx.doi.org/10.1115/1.2835635.

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The prediction of the temperature distribution in a gas turbine rotor containing closed, gas-filled cavities, for example in between two disks, has to account for the heat transfer conditions encountered inside these cavities. In an entirely closed annulus, forced convection is not present, but a strong natural convection flow exists, induced by a nonuniform density distribution in the centrifugal force field. Experimental investigations have been made to analyze the convective heat transfer in closed, gas-filled annuli rotating around their horizontal axes. The experimental setup is designed to establish a pure centripetal heat flux inside these annular cavities (hot outer, and cold inner cylindrical wall, thermally insulated side walls). The experimental investigations have been carried out for several geometries varying the Rayleigh number in a range usually encountered in cavities of turbine rotors (107 < Ra < 1012). The convective heat flux induced for Ra =1012 was found to be a hundred times larger compared to the only conductive heat flux. By inserting radial walls the annulus is divided into 45 deg sections and the heat transfer increases considerably. A computer program to simulate flow and heat transfer in closed rotating cavities has been developed and tested successfully for annuli with isothermal side walls with different temperatures giving an axial heat flux. For the centripetal heat flux configuration, three-dimensional steady-state calculations of the sectored annulus were found to be consistent with the experimental results. Nevertheless, analysis of unsteady calculations show that the flow can become unstable. This is analogous to the Be´nard problem in the gravitational field.

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26

Swaminathan, V. P., N. S. Cheruvu y A. Saxena. "Life Assessment of an HP-IP Rotor Under Creep Service Conditions". Journal of Engineering for Gas Turbines and Power 112, n.º 2 (1 de abril de 1990): 237–42. http://dx.doi.org/10.1115/1.2906169.

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A CrMoV high and intermediate-pressure (HP-IP) rotor exhibited in-service cracking in the blade groove walls. Cracks initiated from a notch and propagated under creep conditions to a depth of 0.255 in. (6.5 mm). Since the unit was base loaded, the contribution of cyclic loading (startups and shutdowns) was not significant. The total life of the groove walls is predicted by applying a life prediction approach that accounts for both crack initiation and propagation. Crack initiation life is based on short-term creep tests extrapolated to long times using a time-temperature parameter. Crack propagation time is estimated using a newly developed time-dependent fracture mechanics concept. A parameter Ct is used to express the crack growth rate under creep loading conditions. Pertinent material properties such as creep deformation and creep crack growth rate were obtained by testing the material from the subject rotor. The results obtained by this analysis show that about 50 percent of the estimated life was spent in crack propagation. Predicted service life time compares very favorably with the actual operating life of the rotor.

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27

Konuş, Mehmet Fatih y Ömer Savaş. "Rotor Vortex Wake in Close Proximity of Walls in Hover". Journal of the American Helicopter Society 61, n.º 4 (1 de octubre de 2016): 1–12. http://dx.doi.org/10.4050/jahs.61.042003.

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28

Chaieb, Ismahane, Toufik Boufendi y Xavier Nicolas. "Taylor-Couette flow with mixed convection heat transfer and variable properties in a horizontal annular pipe". Thermal Science, n.º 00 (2021): 271. http://dx.doi.org/10.2298/tsci210218271c.

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Taylor-Couette flows in a horizontal annular gap between finite coaxial cylinders in rotor-stator configuration are numerically investigated. The inner cylinder (rotor) rotates at a constant angular velocity while the outer cylinder (stator) is at rest. They are limited at their extremities by two fixed walls that prevent axial fluid flow. In addition, a heat transfer is generated by an imposed temperature difference, with the rotor hotter than the stator while the end-walls are adiabatic. The fluid physical properties are temperature dependent. This non-linear physics problem, with a strong coupling of the conservation equations and boundary conditions, is solved by a finite volume method with numerical schemes of second order space and time accuracies. The radius and aspect ratios and the Taylor, Grashof and Prandt numbers are the control parameters. The developed numerical code has been tested for different meshes and perfectly validated. Extensive calculations have been made in large ranges of the Taylor and Grashof numbers to analyze the Taylor-Couette flow in convection modes. The results highlight the dynamic and thermal instabilities generated in the Taylor Couette flow from the appearance of Ekman cells to the Taylor vortex propagation in the entire annulus. The combined effect of these vortices with the secondary flow improves the heat transfer. Furthermore, the influence of the physical properties in the radial direction is more marked in the vicinity of the walls. Finally, we propose an empirical correlation of the Nusselt number in the studied parameter ranges.

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29

Kolaei, Amir, Devin Barcelos y Götz Bramesfeld. "Experimental Analysis of a Small-Scale Rotor at Various Inflow Angles". International Journal of Aerospace Engineering 2018 (8 de octubre de 2018): 1–14. http://dx.doi.org/10.1155/2018/2560370.

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The performance characteristics of a rotor that is typically used for small unmanned aircraft were analyzed in a series of wind-tunnel experiments. Wind-tunnel measurements were conducted with the rotor at various inflow angles in order to investigate the effects on the rotor performance of partially or fully edgewise flow as they are typically encountered with small multirotor vehicles. Rotor tests were also performed under static and fully axial flow conditions in order to investigate the aerodynamic performance during hover as well as vertical climb and descent. The wind-tunnel data were corrected to account for the interference of wind-tunnel walls with the rotor wake and the blockage due to the presence of the rotor test stand in the wind-tunnel test section. The results are presented in terms of thrust, power, and roll moment coefficients under different rotor rotational speeds for a T-motor 18x6.1. Additionally, the measured thrust and power coefficients of Master Airscrew Electric 11x7 are compared with available propeller data under static and axial flow conditions for verification purposes. It is shown that the rotor performance characteristics are strongly affected by the freestream advance ratio and the freestream inflow angles. For example, at inflow angles that are typical for multirotor vehicles between about 15° and 0° with respect to the rotor disc, thrust coefficients stay constant or grow with increasing advance ratio, whereas power coefficients remain relatively constant with changing advance ratio.

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30

Furukawa, M., K. Saiki, K. Nagayoshi, M. Kuroumaru y M. Inoue. "Effects of Stream Surface Inclination on Tip Leakage Flow Fields in Compressor Rotors". Journal of Turbomachinery 120, n.º 4 (1 de octubre de 1998): 683–92. http://dx.doi.org/10.1115/1.2841777.

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Experimental and computational results of tip leakage flow fields in a diagonal flow rotor at the design flow rate are compared with those in an axial flow rotor. In the diagonal flow rotor, the casing and hub walls are inclined at 25 deg and 45 deg, respectively, to the axis of rotation, and the blade has airfoil sections with almost the same tip solidity as that of the axial flow rotor. It is found out that “breakdown” of the tip leakage vortex occurs at the aft part of the passage in the diagonal flow rotor. The “vortex breakdown” causes significant changes in the nature of the tip leakage vortex: disappearance of the vortex core, large expansion of the vortex, and appearance of low relative velocity region in the vortex. These changes result in a behavior of the tip leakage flow that is substantially different from that in the axial flow rotor: no rolling-up of the leakage vortex downstream of the rotor, disappearance of the casing pressure trough at the aft part of the rotor passage, large spread of the low-energy fluid due to the leakage flow, much larger growth of the casing wall boundary layer, and considerable increase in the absolute tangential velocity in the casing wall boundary layer. The vortex breakdown influences the overall performance, also: large reduction of efficiency with the tip clearance, and low level of noise.

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31

Сыркин, Vladimir Syrkin, Васильев y Sergey Vasilev. "JUSTIFICATION OF ROTOR SPEED OF RADIAL HONEY SEPARATOR WITH THE HORIZONTAL FULCRUM PIN". Bulletin Samara State Agricultural Academy 1, n.º 4 (27 de octubre de 2016): 51–54. http://dx.doi.org/10.12737/21791.

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The purpose of research is increase in effectiveness of pumping of honey in the separator of radial type with a horizontal spin axis of a rotor. Use radial a separator allows to make honey pumping on both sides of a frame at once and places larger quantity of a frames. The radial separator consists of housing and a rotor. The rotor is set in motion via the belt drive manually or the electric motor. The rotation frequency of a rotor of a separator is the major technology factor influencing honey pumping process. With increase in a rotation frequency the centrifugal force providing a honey exit from honeycombs of a frame increases. The high rotation frequency of a rotor with a framework, can lead to destruction of a wax basis of a cellular frame. Low the rotation frequency can become the reason of inexact pumping of honey from honeycombs. In the course of centrifugation the honey which is contained in everyone unit is affected by the gravity, a centripetal force, tangential force of shift of layers of honey, force of reaction of walls of honeycombs. As a result of calculation it is established that the rotation frequency of a rotor depends on such parameters as viscosity of honey, geometrical parameters of honeycombs, distances of honeycombs from a separator rotor spin axis. In the course of work there will be first of all a honey honeycombs located further from a rotor axis. Decrease in cooperative weight of a frame will allow to keep its wholeness and to gradually increase a separator rotor rotation frequency.

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32

Papoyan, Vl V., V. S. Poghosyan y V. B. Priezzhev. "A loop reversibility and subdiffusion of the rotor-router walk". Journal of Physics A: Mathematical and Theoretical 48, n.º 28 (29 de junio de 2015): 285203. http://dx.doi.org/10.1088/1751-8113/48/28/285203.

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33

Comyn, Graeme I., David S. Nobes y Brian A. Fleck. "PERFORMANCE EVALUATION AND WAKE STUDY OF A MICRO WIND TURBINE". Transactions of the Canadian Society for Mechanical Engineering 35, n.º 1 (marzo de 2011): 101–17. http://dx.doi.org/10.1139/tcsme-2011-0007.

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In preparation for a study on icing of wind turbine blades, we tested a horizontal axis micro wind turbine in a low speed wind tunnel. The ratio of wind turbine rotor area to wind tunnel cross-sectional area resulted in highly blocked experimental configuration. The turbine was instrumented to measure rotational speed of the rotor, axial thrust and power output. Performance characteristics were calculated and compared with the manufacturer’s published data. In addition, the near wake of the turbine was measured with a Kiel probe. One dimensional axial momentum theory, including a modification that includes channel walls, was applied to determine power extracted from the wind by the rotor. The results were compared to actual power output and show that though the assumptions of the model over-predict power by 50 % the basic trend is followed.

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34

Liu, Qi, Hang Guo, Wei Wang, Yu Ting Wu, Fang Ye y Chong Fang Ma. "Static Finite Element Analysis on Cast Shell of a 100 kW Single Screw Expander". Applied Mechanics and Materials 694 (noviembre de 2014): 279–82. http://dx.doi.org/10.4028/www.scientific.net/amm.694.279.

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In the process of shell design of a 100kW single screw expander, the fundamental research on the screw chamber walls thickness is still lacking. Thin wall may cause deformation and the damage possibility of the inlet passage. Thick wall will increase the weight of the expander and led to assembly problem and transportation inconvenience. In this paper, static finite element analysis on cast shell of the 100 kW single screw expander was carried out. By calculating stress distribution and deformation of the expander shell under 1.5 times of the design pressure, the authors find the thickness of gate rotor chamber walls and inlet passage walls as 15 mm is acceptable, but the thickness of screw chamber walls should be at least 35 mm.

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35

Gannon, Anthony J. y Theodor W. von Backstro¨m. "Solar Chimney Turbine Performance". Journal of Solar Energy Engineering 125, n.º 1 (27 de enero de 2003): 101–6. http://dx.doi.org/10.1115/1.1530195.

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An experimental investigation of the performance of a solar chimney turbine is presented. The design features a single rotor and uses the chimney supports as inlet guide vanes (IGVs) to introduce pre-whirl. This reduces the turbine exit kinetic energy at the diffuser inlet and assists the flow turning in the IGV-to-rotor duct. The rotor configuration allows the supports to be placed directly under the chimney walls. Measurements from a scale model turbine are used to calculate the turbine performance and efficiency. Efficiencies over a wide operating range and detailed performance measurements at two operating points are presented. Total-to-total efficiencies of 85–90% and total-to-static of 77–80% over the design range are measured. The detailed measurements give insight into the turbine performance and possible design improvements. These results allow more accurate simulation of solar chimney power plants.

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36

Ortega, Adrian, Thomas Gorin y Craig S. Hamilton. "Quantum transport in a combined kicked rotor and quantum walk system". Physics Letters A 395 (abril de 2021): 127224. http://dx.doi.org/10.1016/j.physleta.2021.127224.

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37

Chan, Swee Hong. "Infinite-step stationarity of rotor walk and the wired spanning forest". Proceedings of the American Mathematical Society 149, n.º 6 (26 de marzo de 2021): 2415–28. http://dx.doi.org/10.1090/proc/15476.

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38

YOKOYAMA, Yuya, Satoshi KATAOKA, Daiki TSUJI, Yuta CHONO, Ayaka YASHIMA, Mizue MUNEKATA y Hiroyuki YOSHIKAWA. "810 Fluid Force on the Micro Quad-Rotor in Hovering near Walls". Proceedings of Conference of Kyushu Branch 2014.67 (2014): _810–1_—_810–2_. http://dx.doi.org/10.1299/jsmekyushu.2014.67._810-1_.

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39

Nussupbekov, Bekbolat, Yerlan Oshanov, Michael Ovcharov, Elmira Mussenova, Didar Ospanova y Madina Bolatbekova. "Development and creation of a hydrodynamic liquid heating unit". Eastern-European Journal of Enterprise Technologies 5, n.º 8(119) (30 de octubre de 2022): 62–69. http://dx.doi.org/10.15587/1729-4061.2022.264227.

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The work is devoted to the study of the parameters of an installation for heating a coolant using liquid forcing through throttle openings. A scheme of a full-size experimental stand has been developed and the principles of operation are described in detail. For visual observation of the state of the liquid at different angular speeds of rotation of the rotor, a transparent drum model is made. The influence of the shape of the rotor skirt and the depth of its immersion in the liquid on the filling capacity of the rotor cavity at an angular velocity from 42 to 314 rad/s has been determined. The optimal parameters of the depth of immersion of the drum skirt with a diameter of 0.5 m in the liquid, at low rotor speeds of 16, 24, 32 rad/s, were obtained. The angle of inclination is calculated and it is experimentally proved that for a conical shape it is 5 degrees. It was found that at angular velocities of the rotor more than 100 rad/s, the shape and depth of immersion of the skirt in the liquid do not affect the filling of the rotor, since the feed is higher than its flow through the throttle openings. It is shown that the use of rotational forces to heat the liquid allows using an electric motor with less power, since it is spent only on unwinding the rotor with the liquid. The calculated dependence of the liquid pressure on the side walls of the rotor, the liquid heating temperature on the angular velocity of rotation of the rotor and on two values of the area of the throttle openings, at 31.4·10-6 m2 and 64.34·10-6 m2, is obtained. When the total area of the throttle openings is doubled, the temperature of the liquid heating at the same angular velocities increases from 35.6 °C to 82.5 °C. The above installation parameters allow you to get hot water when using small shell-and-tube heat exchangers

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40

Chudyk, I. I., Ya S. Hrydzhuk y L. R. Yurych. "Estimation of mechanical energy consumption of the drill string in rotary drilling". Oil and Gas Power Engineering, n.º 2(30) (21 de noviembre de 2018): 17–24. http://dx.doi.org/10.31471/1993-9868-2018-2(30)-17-24.

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The article is devoted to the study of dynamic phenomena in the drill string based on energy positions. Thefriction of mechanical transmissions in rotor drive, curved sections of the drill string on drill-hole walls in thedrilling mud and change in the torque on the bit are the main causes of the mechanical energy consumption in theprocess of drilling. In this case, the required engine power is used for to provide drill string rotation in the well withsome unevenness and bottom-hole deepening. The power balance equation of the mechanical system “power drive–drill string–bottom hole” is analyzed. Theauthors have developed the problem for defining the kinetic energy of drill string in rotor drilling, which is spent onovercoming the friction in drive transmissions and drill string on drill-hole walls in the drilling mud as well as ondrilling the bottom hole. The use of the defined mathematical dependencies is demonstrated by the nomograph fordetermining the friction power in case of drill string free run in the well. The obtained results of theoreticalresearch can be used by engineering and manufacturing divisions of drilling enterprises for the engineeringestimate of energy consumption in rotary drilling.

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MINASYAN, David, Alana ELOEVA, Sergey NAZAROV y Pavel SKVORTSOV. "COMPARISON OF THE CRUSHED MATERIAL MOVEMENT MODEL IN THE BODY OF A VERTICAL CENTRIFUGAL MILL". Sustainable Development of Mountain Territories 13, n.º 1 (27 de marzo de 2021): 119–24. http://dx.doi.org/10.21177/1998-4502-2021-13-1-119-124.

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Introduction. Improving the performance, increasing productivity, reducing the metal consumption of grinding equipment and other mining machines is usually a very expensive process. It requires a large amount of development work, the production of prototype machines, and a large amount of experimental research. In this regard, one of the most important tasks is to simulate the movement of bulk material in operations for processing minerals in various equipment. In such modeling, the discrete element method (DEM) is widely used. The purpose of the research is to compare the models of the movement of the crushed material in the body of a vertical centrifugal mill. Research methodology The motion of the bulk medium in a vertical centrifugal mill was modeled using two models. In the first model, the cylindrical body of the centrifugal mill was assumed to be stationary, and on its surface and on the entire surface of the rotor, conditions were set for the absence of a relative speed of movement of the crushed material. In the second model, a hydrodynamic model was used to describe the motion of a granular material as a viscous incompressible liquid with a compression ratio that depends on the pres-sure. In this model, the viscosity coefficient is represented as consisting of two terms: a constant (analogous to dynamic viscosity) and an excess pressure over hydrostatic pressure. Research results It is established that both models give the same character of the movement of the material in the mill body. It is determined that the absolute velocity of the material movement near the walls and near the mill rotor is approximately the same for both models, but in the data obtained using the hydrodynamic model, as the material moves away from the walls and the rotor, it slows down more than for the model using the discrete element method. It is revealed that the absolute velocity of the material movement near the walls and at the axis of the mill rotor is approximately the same for both models, but in the data obtained using the hydrodynamic model, as it moves away from the walls and the rotor, the material slows down significantly more than for the model using the discrete element method. Based on the simulation results, it can be concluded that for a more accurate simulation of the processes occurring during the rapid movement of bulk material in the grinding equipment, it is preferable to use a model using the discrete element method. It is advisable to use the hydrodynamic model for conducting a large number of search dawns or as a predicate model that will allow you to quickly set the initial velocity values for particles in a model using the discrete element method. Conclusions 1. A hydrodynamic model of the motion of a bulk medium in a vertical centrifugal mill, represented as a viscous incompressible liquid with a compression coefficient depending on the pressure has been developed. 2. It is established that for a more correct simulation of the processes occurring during the rapid movement of bulk material in the grinding equipment, it is preferable to use a model using the discrete element method. At the same time, it is advisable to use the hydrodynamic model for conducting a large number of search calculations or as a predicate model that will allow you to quickly set the initial velocity values for particles in a model using the discrete element method.

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42

Akwa, J. V. y A. P. Petry. "STATORS USE INFLUENCE ON THE PERFORMANCE OF A SAVONIUS WIND ROTOR USING COMPUTATIONAL FLUID DYNAMICS". Revista de Engenharia Térmica 10, n.º 1-2 (31 de diciembre de 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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43

Bohn, D., R. Emunds, V. Gorzelitz y U. Kru¨ger. "Heat Transfer Committee Best 1994 Paper Award: Experimental and Theoretical Investigations of Heat Transfer in Closed Gas-Filled Rotating Annuli II". Journal of Turbomachinery 118, n.º 1 (1 de enero de 1996): 11–19. http://dx.doi.org/10.1115/1.2836590.

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Increasing the thermal efficiency by higher turbine inlet temperatures is one of the most important aims in the area of gas turbine development. Because of the high temperatures, the turbine vanes and blades have to be cooled, and also knowledge of the mechanically and thermally stressed parts in the hottest zones of the rotor is of great interest. The prediction of the temperature distribution in a gas turbine rotor containing closed, gas-filled cavities, for example, in between two disks, has to account for the heat transfer conditions encountered in these cavities. In an entirely closed annulus, forced convection is not present, but a strong natural convection flow exists, induced by a nonuniform density distribution in the centrifugal force field. In Bohn et al. (1994), experimental and numerical investigations on rotating cavities with pure centripetal heat flux had been carried out. The present paper deals with investigations on a pure axially directed heat flux. An experimental setup was designed to realize a wide range of Ra numbers (2·108< Ra < 5·1010) usually encountered in cavities of gas turbine rotors. Parallel to the experiments, numerical calculations have been conducted. The numerical results are compared with the experimental data. The numerical scheme is also used to account for the influence of Re on heat transfer without changing Ra. This influence could not be pointed out by experiments, because a variation of the Re–Ra characteristic of the employed annuli was not possible. It was found that the numerical and experimental data are in quite good agreement, with exception of high Ra, where the numerical scheme predicts higher heat transfer than the experiments show. One reason may be that in the experiments the inner and outer cylindrical walls were not really adiabatic, an assumption used in the numerical procedure. Moreover, the assumption of a two-dimensional flow pattern may become invalid for high Ra. The influence of three-dimensional effects was studied with the three-dimensional version of the numerical code. In contrast to the radial directed heat transfer, it was found that Nu is much smaller and depends strongly on Re, whereas the radial heat transfer is only weakly influenced by Re.

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Nikiforov, A. N., N. A. Tatus’ y A. E. Shokhin. "Self-excitation of an experimental rotor with radial walls and filled partially with liquid". Journal of Machinery Manufacture and Reliability 44, n.º 3 (mayo de 2015): 200–203. http://dx.doi.org/10.3103/s1052618815030139.

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Wu, Han, Chuntai Zheng, Peng Zhou, Ryu Fattah, Xin Zhang, Guocheng Zhou y Bao Chen. "The multi-functional rotor aerodynamic and aeroacoustic test platform at HKUST". INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, n.º 2 (1 de agosto de 2021): 4410–17. http://dx.doi.org/10.3397/in-2021-2695.

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This paper describes the multi-functional rotor noise and aerodynamics test platform at the Hong Kong University of Science and Technology (HKUST). To investigate the noise characteristics of propellers with aerodynamic flows, the test rig is installed in the 2.5×2 (m) low-speed and low-noise wind tunnel in the Aerodynamic and Acoustic Facility (AAF) at HKUST. The wind tunnel can facilitate flow from 0 to 40 m/s. The test rig is assembled in a turntable on the ceiling of the tunnel wall, which enables the testing range of pitch angle can vary from 0° (axial flow) to 90° (parallel flow), with an accuracy of 0.1°. The noise produced by the rotor is measured by a set of wall-mounted surface microphones. Semi-empirical calibration is conducted to quantify the noise reflection by the tunnel walls. A low-noise struct has been designed and manufactured to locate a set of far-field microphones equipped with nosecone, to improve the quality of acoustic measurement inside the flow. In addition, a synchronized system is developed to conduct the phase-locking Particle Image Velocimetry (PIV) measurement on the rotor, to study the flow pattern to better understand the noise generation mechanism.

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46

Shahsavari, A. y M. Nili-Ahmadabadi. "Investigation of an innovative non-free vortex aerodynamic procedure to design a single-stage transonic compressor". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 232, n.º 11 (8 de junio de 2017): 2132–43. http://dx.doi.org/10.1177/0954410017710272.

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This paper presents an innovative design method for a transonic compressor based on the radial equilibrium theory by means of increasing blade loading. Firstly, the rotor blade of a transonic compressor is redesigned based on the constant spanwise de-Haller number and diffusion. The design method leads to an unconventional increased axial velocity distribution in tip section, which originates from non-uniform enthalpy distribution assumption. A code is applied to extract the compressor meridional plane and blade-to-blade geometry containing rotor and stator in order to design the blade three-dimensional view. A structured grid is generated for the numerical domain of fluid. Finer grids are used for the regions near walls to capture the boundary layer effects and behavior. Reynolds-averaged Navier–Stokes equations are solved by finite volume method for rotating zones (rotor) and stationary zones (stator). The experimental data, available for the performance map of NASA Rotor67, is used to validate the results of the current simulations. Then, the capability of the design method is validated by computational fluid dynamics that is capable of predicting the performance map. The numerical results of the new geometry by representing 11% improvement in efficiency and 19% in total pressure ratio verify the new method advantages. The computational fluid dynamics results also show that the newly designed rotor blades due to a higher velocity in the tip section have a special capacity to increase the loading without any separation. The mass flow reduction is observed in the new geometry, which could be easily improved by changing stagger angle.

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47

Khlaifat, Nour, Ali Altaee, John Zhou, Yuhan Huang y Ali Braytee. "Optimization of a Small Wind Turbine for a Rural Area: A Case Study of Deniliquin, New South Wales, Australia". Energies 13, n.º 9 (6 de mayo de 2020): 2292. http://dx.doi.org/10.3390/en13092292.

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The performance of a wind turbine is affected by wind conditions and blade shape. This study aimed to optimize the performance of a 20 kW horizontal-axis wind turbine (HAWT) under local wind conditions at Deniliquin, New South Wales, Australia. Ansys Fluent (version 18.2, Canonsburg, PA, USA) was used to investigate the aerodynamic performance of the HAWT. The effects of four Reynolds-averaged Navier–Stokes turbulence models on predicting the flows under separation condition were examined. The transition SST model had the best agreement with the NREL CER data. Then, the aerodynamic shape of the rotor was optimized to maximize the annual energy production (AEP) in the Deniliquin region. Statistical wind analysis was applied to define the Weibull function and scale parameters which were 2.096 and 5.042 m/s, respectively. The HARP_Opt (National Renewable Energy Laboratory, Golden, CO, USA) was enhanced with design variables concerning the shape of the blade, rated rotational speed, and pitch angle. The pitch angle remained at 0° while the rising wind speed improved rotor speed to 148.4482 rpm at rated speed. This optimization improved the AEP rate by 9.068% when compared to the original NREL design.

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48

Li, Yi, Xiangyun Zhao, Zhe Lin y Guang Zhang. "Particle Collision Study Based on a Rotational Boundary Condition". Journal of Marine Science and Engineering 11, n.º 3 (24 de febrero de 2023): 490. http://dx.doi.org/10.3390/jmse11030490.

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The main engineering machinery for the hydrodynamic lifting of seafloor mineral particles is rotor machinery with rotating impeller motion. It is important to study the rebound mechanism of collisions between particles and rotating walls to improve the accuracy of numerical simulation of rotor machinery. In this study, the law of motion change after collisions between particles and rotating walls is investigated using an experimental research method. The results show that the deflection angle of the particles after collision decreases with increases in the rotational speed of the wall, and the spin angular velocity increases with increases in the rotational speed of the wall. The normal velocity coefficient of restitution under the rotating wall is not affected by the rotational speed of the wall. The tangential coefficient of restitution under rotational boundary condition is smaller than the tangential coefficient of restitution under the stationary wall, and the higher the rotational speed, the closer it is to the coefficient of restitution under the stationary wall. During collision in the experiment, the main mode of contact between the particle and the rotating wall is sliding contact. Sliding friction between the particle and the rotating wall results in energy loss in the tangential velocity of the particle, and also provides energy for deflection of the particle’s trajectory and increased kinetic energy from the spin angular velocity; sliding friction loss is affected by the speed of the wall.

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Brennan, G., N. W. Harvey, M. G. Rose, N. Fomison y M. D. Taylor. "Improving the Efficiency of the Trent 500-HP Turbine Using Nonaxisymmetric End Walls—Part I: Turbine Design". Journal of Turbomachinery 125, n.º 3 (1 de julio de 2003): 497–504. http://dx.doi.org/10.1115/1.1450766.

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This paper describes the redesign of the HP turbine of the Rolls-Royce Trent 500 engine, making use of nonaxisymmetric end walls. The original, datum turbine used conventional axisymmetric end walls, while the vane and (shrouded) rotor aerofoil profiles were nominally the same for the two designs. Previous research on the large-scale, low-speed linear cascade at Durham University (see Hartland et al., 1998, “Non-Axisymmetric End Wall Profiling in a Turbine Cascade,” ASME 98–GT-525), had already demonstrated significant potential for reducing turbine secondary losses using nonaxisymmetric end walls-by about one third. This paper shows how a methodology was derived from the results of this research and applied to the design of the single-stage Trent 500-HP turbine (model rig). In particular, the application of a new linear design system for the parametric definition of these end wall shapes (described in Harvey et al., 1999, “Non-Axisymmetric Turbine End Wall Design: Part I Three-Dimensional Linear Design System,” ASME 99–GT-337) is discussed in detail.

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50

SHIMASAKI, Ryota, Satoshi KATAOKA, Wataru TOBO, Mizue MUNEKATA y Hiroyuki YOSHIKAWA. "Effects of Transverse Side Walls on Aerodynamic Characteristics of a Micro Quad-Rotor in Hovering". Proceedings of Mechanical Engineering Congress, Japan 2016 (2016): G0500504. http://dx.doi.org/10.1299/jsmemecj.2016.g0500504.

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