Journal articles on the topic 'Rotors – Aerodynamics'
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1
Barkat, Ibtissem, Abdelouahab Benretem, Fawaz Massouh, Issam Meghlaoui, and Ahlem Chebel. "Modeling and simulation of forces applied to the horizontal axis wind turbine rotors by the vortex method coupled with the method of the blade element." International Journal of Power Electronics and Drive Systems (IJPEDS) 12, no. 1 (March 1, 2021): 413. http://dx.doi.org/10.11591/ijpeds.v12.i1.pp413-420.
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This article aims to study the forces applied to the rotors of horizontal axis wind turbines. The aerodynamics of a turbine are controlled by the flow around the rotor, or estimate of air charges on the rotor blades under various operating conditions and their relation to the structural dynamics of the rotor are critical for design. One of the major challenges in wind turbine aerodynamics is to predict the forces on the blade as various methods, including blade element moment theory (BEM), the approach that is naturally adapted to the simulation of the aerodynamics of wind turbines and the dynamic and models (CFD) that describes with fidelity the flow around the rotor. In our article we proposed a modeling method and a simulation of the forces applied to the horizontal axis wind rotors turbines using the application of the blade elements method to model the rotor and the vortex method of free wake modeling in order to develop a rotor model, which can be used to study wind farms. This model is intended to speed up the calculation, guaranteeing a good representation of the aerodynamic loads exerted by the wind.
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Povarov, Sergii. "Determination of the aerodynamic characteristics of the tiltrotor with the wingtip-mounted coaxial rotors." MECHANICS OF GYROSCOPIC SYSTEMS, no. 40 (December 26, 2021): 108–16. http://dx.doi.org/10.20535/0203-3771402020248778.
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The article describes the study of rotor-to-wing aerodynamic interaction for the wingtip-mounted coaxial rotors configuration of the tiltrotor aircraft.
The influence of the rotor slipstreams on lift-to-drag ratio characteristic was determined. Obtained results were compared with similar characteristics of the equivalent in thrust conventional single rotor slipstreams impact.
Using the computational aerodynamics methods (panel-vortex method) the flow around the tiltrotor model with the wingtip-mounted single and coaxial rotors has been simulated. A study of the basic model configuration with conventional single rotors, based on the technical characteristics of the AgustaWestland AW609 tiltrotor, was conducted. Further researches were conducted for a modified model where single rotors were replaced with equivalent in thrust coaxial rotors. The influence of the rotor slipstreams on the aerodynamic characteristics of the model for both directions of rotors rotation in coaxial combination is considered. Also, the dependence of the maximum lift-to-drag characteristic due to the coaxial rotor diameters change has been determined.
The results show that the coaxial rotor slipstreams-to-wing aerodynamic interaction effect is the similar to the effect of conventional single rotor, but less intensive. Comparison of the results showed that a tiltrotor equipped with wingtip-mounted single rotors has approximately 20% greater maximum lift-to-drag characteristic than one equipped with coaxial rotors with the same thrust. However, the use of coaxial rotors allows getting higher maximum speed, when conventional single rotors lose the efficiency significantly. Therefore, it is advisable to conduct further research for the possibility of using coaxial rotors for tiltrotor aircrafts.
The research results are presented in graphical form. The obtained data provides a basis for further studies of the described problem, and also will be useful for new tiltrotor design works.
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Povarov, Sergey. "Comparison of aerodynamic characteristics of convertible models with single and coaxial schemes of propellers." MECHANICS OF GYROSCOPIC SYSTEMS, no. 39 (May 20, 2020): 96–105. http://dx.doi.org/10.20535/0203-3771392020229110.
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The article describes the study of rotor-to-wing aerodynamic interaction for the wingtip-mounted coaxial rotors configuration of the tiltrotor aircraft.
The influence of the rotor slipstreams on lift-to-drag ratio characteristic was determined. Obtained results were compared with similar characteristics of the equivalent in thrust conventional single rotor slipstreams impact.
Using the computational aerodynamics methods (panel-vortex method) the flow around the tiltrotor model with the wingtip-mounted single and coaxial rotors has been simulated. A study of the basic model configuration with conventional single rotors, based on the technical characteristics of the AgustaWestland AW609 tiltrotor, was conducted. Further researches were conducted for a modified model where single rotors were replaced with equivalent in thrust coaxial rotors. The influence of the rotor slipstreams on the aerodynamic characteristics of the model for both directions of rotors rotation in coaxial combination is considered. Also, the dependence of the maximum lift-to-drag characteristic due to the coaxial rotor diameters change has been determined.
The results show that the coaxial rotor slipstreams-to-wing aerodynamic interaction effect is the similar to the effect of conventional single rotor, but less intensive. Comparison of the results showed that a tiltrotor equipped with wingtip-mounted single rotors has approximately 20% greater maximum lift-to-drag characteristic than one equipped with coaxial rotors with the same thrust. However, the use of coaxial rotors allows getting higher maximum speed, when conventional single rotors lose the efficiency significantly. Therefore, it is advisable to conduct further research for the possibility of using coaxial rotors for tiltrotor aircrafts.
The research results are presented in graphical form. The obtained data provides a basis for further studies of the described problem, and also will be useful for new tiltrotor design works.
4
Yin, F. F., J. J. Chen, X. K. Li, Z. L. Ye, W. Tang, X. Shen, and X. J. Guo. "A blade element momentum model for dual-rotor wind turbines considering inter-rotor velocity interferences." Journal of Physics: Conference Series 2265, no. 4 (May 1, 2022): 042058. http://dx.doi.org/10.1088/1742-6596/2265/4/042058.
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Abstract A blade element momentum model for predicting the aerodynamic performance of dual-rotor wind turbines (DRWTs) as an aerodynamic design tool is introduced in this paper. The model considers the inter-rotor axial velocity reduction and the tangential velocity components in the front rotor’s wake to model the inter-rotor velocity interferences for the inflow velocity as the input of the BEM theory. A DRWT with two NREL 5MW rotors is studied using the present model and CFD simulations. Results from the two methods show good agreements with each other in the trends of power, thrust, and aerodynamic loads on the blades despite the error in near-tip regions. The present DRWT configurations have lower optimum tip speed ratios and a wider range of high-CP speeds. The maximum efficiency of the present turbine is improved by only 5%, indicating that a dedicated blade design for DRWT aerodynamics is required to enhance power output and lower the aerodynamic loads.
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Chiang, H. W. D., and S. Fleeter. "Passive Control of Flow-Induced Vibrations by Splitter Blades." Journal of Turbomachinery 116, no. 3 (July 1, 1994): 489–500. http://dx.doi.org/10.1115/1.2929438.
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Splitter blades as a passive control technique for flow-induced vibrations are investigated by developing an unsteady aerodynamic model to predict the effect of incorporating splitter blades into the design of an axial flow blade row operating in an incompressible flow field. The splitter blades, positioned circumferentially in the flow passage between two principal blades, introduce aerodynamic and/or combined aerodynamic-structural detuning into the rotor. The unsteady aerodynamic gust response and resulting oscillating cascade unsteady aerodynamics, including steady loading effects, are determined by developing a complete first-order unsteady aerodynamic analysis together with an unsteady aerodynamic influence coefficient technique. The torsion mode flow induced vibrational response of both uniformly spaced tuned rotors and detuned rotors are then predicted by incorporating the unsteady aerodynamic influence coefficients into a single-degree-of-freedom aero-elastic model. This model is then utilized to demonstrate that incorporating splitters into axial flow rotor designs is beneficial with regard to flow induced vibrations.
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Franke, Daniel, Daniel Möller, Maximilian Jüngst, Heinz-Peter Schiffer, Thomas Giersch, and Bernd Becker. "Experimental Aerodynamic and Aeroelastic Investigation of a Transonic Compressor Rotor with Reduced Blade Count." International Journal of Turbomachinery, Propulsion and Power 6, no. 2 (June 11, 2021): 19. http://dx.doi.org/10.3390/ijtpp6020019.
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This study investigates the aerodynamic and aeroelastic characteristics of a transonic axial compressor, focusing on blade count reduced rotor behavior. The analysis is based on experiments, conducted at the Transonic Compressor Darmstadt test rig at Technical University of Darmstadt and compulsory simulations. In order to obtain measurement data for the detailed aerodynamic and aeroelastic investigation, extensive steady and unsteady instrumentation was applied. Besides transient measurements at the stability limit to determine the operating range and limiting phenomena, performance measurements were performed, presenting promising results with respect to the capabilities of blade count reduced rotors. Close to the stability limit, aerodynamic disturbances like radial vortices were detected for both rotors, varying in size, count, speed and trajectory. Comparing the rotor configurations results in different stability limits along the compressor map as well as varying aeromechanical behavior. Those effects can partially be traced to the variation in blade pitch and associated aerodynamics.
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Shukla, Dhwanil, and Narayanan Komerath. "Multirotor Drone Aerodynamic Interaction Investigation." Drones 2, no. 4 (December 3, 2018): 43. http://dx.doi.org/10.3390/drones2040043.
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Aerodynamic interactions between rotors are important factors affecting the performance of in-plane multirotor Unmanned Air Vehicles (UAVs) or drones, which are the majority of small size UAVs (or mini-drones). Optimal design requires knowledge of the flow features. The low Reynolds number of many UAV rotors raises the question of how these features differ from those expected by traditional analytical methods for rotorcraft. Aerodynamics of a set of side-by-side rotors in hover over a range of rotor separation and Reynolds number is studied using high-speed Stereo Particle Image Velocimetry (SPIV) and performance measurements. The instantaneous and time-averaged SPIV data presented here indicate an increase in inter-rotor wake interactions with decrease in rotor spacing and Reynolds number. A dip in rotor efficiency at small rotor spacing at low Reynolds number is observed through thrust and torque measurements. The basic components of in-plane multirotor wake and velocity profiles are identified and discussed to help generalize the findings to a wide range of drones. However, the data provide confidence in traditional analysis tools, with small modifications.
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Gennaretti, M., and G. Bernardini. "Aeroelastic response of helicopter rotors using a 3D unsteady aerodynamic solver." Aeronautical Journal 110, no. 1114 (December 2006): 793–801. http://dx.doi.org/10.1017/s0001924000001664.
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The prediction of blade deflections and vibratory hub loads concerning helicopter main rotors in forward flight is the objective of this work. They are determined by using an aeroelastic model derived through the coupling between a nonlinear blade structural model and a boundary integral equation solver for three-dimensional, unsteady, potential aerodynamics. The Galerkin method is used for the spatial integration, whereas the periodic blade response is determined by a harmonic balance approach. This aeroelastic model yields a unified approach for aeroelastic response and blade pressure prediction that may be used for aeroacoustic purposes, with the possibility of including effects from both blade-vortex interaction and multiple-body aerodynamic interaction. Quasi-steady aerodynamic models with wake-inflow from the three-dimensional aerodynamic solver are also applied, in order to perform a comparative study. Numerical results show the capability of the aeroelastic tool to evaluate blade response and vibratory hub loads for a helicopter main rotor in level flight conditions, and examine the sensitivity of the predictions on the aerodynamics model used.
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Huo, Chao, Roger Barènes, and Jérémie Gressier. "Experimental Analysis of the Aerodynamics of Long-Shrouded Contrarotating Rotor in Hover." Journal of the American Helicopter Society 60, no. 4 (October 1, 2015): 1–12. http://dx.doi.org/10.4050/jahs.60.042004.
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This paper aims to quantify the benefits of a shrouded coaxial rotor configuration through experimental comparisons with free (not shrouded) rotors in hover. The experiment shows that both the figure of merit of contrarotating rotors and the system power loading are improved by the shroud inclusion. Improvements are induced by a suction effect at the inlet, which can be optimized by a regulation effect of the mass flow. Compared to free rotors, the strong suction peak formed on the shroud leading edge by a 65% increase in mass flow, allowing the shroud to contribute up to 56% of the total thrust. More uniform pressure distribution in the downstream rotor and less contraction of the slipstream decrease losses and increase the rotor efficiency. The shrouded system efficiency is further improved if the upstream rotor rotates slower than the rear one, for a given total shaft power, because a stronger pressure depression occurs upstream of the rotors to generate more mass flow. On the other hand, the system behavior is insensitive to the interrotor distance.
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Prothin, S., C. Fernandez Escudero, N. Doué, and T. Jardin. "Aerodynamics of MAV rotors in ground and corner effect." International Journal of Micro Air Vehicles 11 (January 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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Jahn, Ingo, and Peter Jacobs. "Using Meridional Streamline and Passage Shapes to Generate Radial Turbomachinery Geometry and Meshes." Applied Mechanics and Materials 846 (July 2016): 1–6. http://dx.doi.org/10.4028/www.scientific.net/amm.846.1.
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An important aspect for structural and aerodynamics design of radial flow turbomachinery is the definition of the geometry and the generation of meshes for computational analysis. Particularly in the area of computational design and optimization, the way the geometry is defined is important, as it can limit design space. Traditionally, radial compressors and radial turbine rotors are defined using a mechanical design approach. Effectively a hub and shroud profile, followed by a rotorblade geometry are defined and the shape is adjusted in order to meet certain aerodynamic boundary conditions. The current paper presents an alternative approach, in which the overall geometry is defined starting from an aerodynamic requirement. The corresponding rotor and blade geometry is generated automatically, based on certain constraints. The advantage of this approach is the ability to define directly the aerodynamic requirements, which may allow a simpler efficient optimization of the aerodynamics.
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Shen, Xin, Ping Hu, Jinge Chen, Xiaocheng Zhu, and Zhaohui Du. "The unsteady aerodynamics of floating wind turbine under platform pitch motion." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 8 (March 29, 2018): 1019–36. http://dx.doi.org/10.1177/0957650918766606.
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The aerodynamic performance of floating platform wind turbines is much more complex than fixed-base wind turbines because of the flexibility of the floating platform. Due to the extra six degrees-of-freedom of the floating platform, the inflow of the wind turbine rotors is highly influenced by the motions of the floating platform. It is therefore of interest to study the unsteady aerodynamics of the wind turbine rotors involved with the interaction of the floating platform induced motions. In the present work, a lifting surface method with a free wake model is developed for analysis of the unsteady aerodynamics of wind turbines. The aerodynamic performance of the NREL 5 MW floating wind turbine under the prescribed floating platform pitch motion is studied. The unsteady aerodynamic loads, the transient of wind turbine states, and the instability of the wind turbine wakes are discussed in detail.
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Figat, Marcin. "Aerodynamics analysis of rotor’s impact on the aircraft in the tandem wing configuration." Aircraft Engineering and Aerospace Technology 92, no. 3 (October 22, 2018): 336–44. http://dx.doi.org/10.1108/aeat-01-2018-0065.
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Purpose This paper aims to present the results of aerodynamic calculation of the aircraft in tandem wing configuration called VTOL. A presented vehicle combines the capabilities of the classic aircraft and helicopters. The aircraft is equipped with two pairs of tilt-rotors mounted on the tips of the front and the rear wing. The main goal of the presented research was to find the aerodynamic impact of both pairs of tilt-rotors on aerodynamic coefficients of the aircraft. Moreover, the rotors impact on the static stability of the aircraft was investigated too. Design/methodology/approach The CFD analysis was made for the complete aircraft in the tandem wing configuration. The computation was performed for the model of aircraft which was equipped with the four sub-models of the front and rear rotors. They were modeled as the actuator discs. This method allows for computing the aerodynamic impact of rotating components on the aircraft body. All aerodynamic analysis was made by the MGAERO software. The numerical code of the software was based on the Euler flow model. The used numerical method allows for the quick computation of very complex model of aircraft with a satisfied accuracy. Findings The result obtained by computation includes the aerodynamic coefficients which described the impact of the tilt rotors on the aircraft aerodynamic. The influence of the angle of attack, sideslip angle and the change of rotor tilt angle was investigated. Evaluation of the influence was made by the stability margin analysis and the selected stability derivatives computation. Practical implications Presented results could be very useful in the computation of dynamic stability of unconventional aircraft. Moreover, results could be helpful during designing the aircraft in the tandem wing configuration. Originality/value This paper presents the aerodynamic analysis of the unconventional configuration of the aircraft which combines the tandem wing feature with the tilt-rotor advantages. The impact of disturbance generated by the front and rear rotors on the flow around the aircraft was investigated. Moreover, the impact of rotors configuration on the aircraft static stability was found too.
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Lei, Yao, and Jinli Wang. "Aerodynamic Performance of Quadrotor UAV with Non-Planar Rotors." Applied Sciences 9, no. 14 (July 10, 2019): 2779. http://dx.doi.org/10.3390/app9142779.
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The mobility of a quadrotor UAV is significantly affected by its aerodynamics, especially when the closely spaced rotors are applied in the multi-rotor system. This paper addresses the aerodynamic modeling of non-planar quadrotor UAV with various rotor spacing (1 d–2 d) and disk plane angle (0–50 deg). The inter-rotor interference and the power models are also proposed in this paper. In order to validate the non-planar model, a series of CFD analyses and experiments were conducted. The obtained results demonstrate that the flow field of the non-planar quadrotor is extremely complicated when the unsteady flow is involved. The pulsation of partial angle of attack and pressure distribution is formed when the blade passes through the vortex. The thrust is increasing significantly along with the tilt angle, resulting from the stronger outflow of the non-planar rotors, which is also leading the power increment. However, the thrust increment is not that obvious when the spacing is larger than 1.4 d. The experiments and the numerical simulation results provide consistent trends and demonstrate the effectiveness of the aerodynamic model of the non-planar quadrotor. The comparison with the traditional planar quadrotor validates that the proposed non-planar quadrotor has better aerodynamic and control performances with a larger power loading.
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Gundy-Burlet, K. L., M. M. Rai, R. C. Stauter, and R. P. Dring. "Temporally and Spatially Resolved Flow in a Two-Stage Axial Compressor: Part 2—Computational Assessment." Journal of Turbomachinery 113, no. 2 (April 1, 1991): 227–32. http://dx.doi.org/10.1115/1.2929090.
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Fluid dynamics of turbomachines are complicated because of aerodynamic interactions between rotors and stators. It is necessary to understand the aerodynamics associated with these interactions in order to design turbomachines that are both light and compact as well as reliable and efficient. The current study uses an unsteady, thin-layer Navier–Stokes zonal approach to investigate the unsteady aerodynamics of a multistage compressor. Relative motion between rotors and stators is made possible by the use of systems of patched and overlaid grids. Results have been computed for a 2 1/2-stage compressor configuration. The numerical data compare well with experimental data for surface pressures and wakes. In addition, the effect of grid refinement on the solution is studied.
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Gennaretti, M., and L. Greco. "Whirl flutter analysis of prop-rotors using unsteady aerodynamics reduced-order models." Aeronautical Journal 112, no. 1131 (May 2008): 261–70. http://dx.doi.org/10.1017/s0001924000002207.
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Abstract The prediction of this aeroelastic phenomenon is an urgent need of the designer and requires devoted numerical tools. This work examines the influence of the accuracy of the aerodynamic modelling on whirl flutter analysis, with particular attention to those models that can conveniently be applied to preliminary design and control purposes. Considering a simple pylon/prop-rotor structure, the aeroelastic instability boundaries are identified by 2D quasi-steady and 2D unsteady aerodynamics theories, along with a 3D unsteady, potential flow BEM solver. A methodology for deriving reduced-order models from unsteady aerodynamic solutions is used. The numerical investigation highlights that the accuracy of the aerodynamic solver included in the analysis may be of crucial importance. The use of 2D aerodynamic models does not always guarantee conservative stability predictions, and this is particularly true for three-bladed rotors where a fully 3D unsteady solver coupled with a wake alignment algorithm seems to be necessary.
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Sun, Zhenye, Wei Jun Zhu, Wen Zhong Shen, Wei Zhong, Jiufa Cao, and Qiuhan Tao. "Aerodynamic Analysis of Coning Effects on the DTU 10 MW Wind Turbine Rotor." Energies 13, no. 21 (November 3, 2020): 5753. http://dx.doi.org/10.3390/en13215753.
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The size of wind turbine rotors is still rapidly increasing, though many technical challenges emerge. Novel rotor designs emerge to satisfy this up-scale trend, such as downwind load-aligned concepts, which orients the loads along the blade spanwise to greatly decrease the bending moments at the root. As the studies on the aerodynamics of these rotor concepts using 3D body-fitted mesh are very limited, this paper establishes different cone configurations based on the DTU 10 MW reference rotor and conducts a series of simulations. It is found that the cone angle and the distance from the blade section to the tip vortex are two deterministic factors on conning. Upwind rotors have larger power output, less thrust, smaller wake deficit, and smaller influencing area than downwind rotors of the same size, which provides superior aerodynamic priority and benefits wind farm design. The largest upwind cone angle of 14.03°, among the cases studied, leads to the highest torque to thrust ratio which is 3.63% higher than the baseline rotor. The downwind load-aligned rotor, designed to reduce the blade root bending moments at large wind speed, performs worse at the present simulation conditions than an upwind rotor of the same size.
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Veismann, Marcel, Daniel Yos, and Morteza Gharib. "Parametric study of small-scale rotors in axial descent." Physics of Fluids 34, no. 3 (March 2022): 035124. http://dx.doi.org/10.1063/5.0083761.
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Despite extensive research in multirotor aerodynamics in the recent past, axial descent, specifically the vortex ring state, still poses great challenges for multirotor configurations as this flight stage is typically accompanied by severe losses in rotor thrust and strong thrust fluctuations. This paper presents a parametric study to investigate the influence of relevant geometric parameters of a small-scale rotor blade on the rotor performance in axial descent. Design variables subject to variation were the collective pitch, chord length, taper ratio, number of blades, as well as the tip geometry. Custom rotors for each parameter modification were manufactured and experimentally evaluated in wind tunnel tests with mean thrust recordings and measurements of the thrust fluctuations serving as performance metrics. Results indicated that rotor blades with larger aspect ratio and higher blade loading coefficient are less affected by the adverse aerodynamics in the vortex ring state, experiencing lower thrust losses and vibrational loads. Particle image velocimetry flow visualization confirmed that the aerodynamic losses in the vortex ring state can be attributed to blade vortex interactions. Comparison of the rotor flow structure in hover of all investigated rotor designs suggested that improvements in the descent performance of a rotor stem from a combination of reduced tip vortex strength and increased axial tip vortex convection rate. Using the experimental findings of this study, a predictive model for approximating the maximum extent of mean thrust losses in axial descent for a given blade geometry and hover thrust coefficient could be established.
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Zhang, Yuan, Xin Cai, Shifa Lin, Yazhou Wang, and Xingwen Guo. "CFD Simulation of Co-Planar Multi-Rotor Wind Turbine Aerodynamic Performance Based on ALM Method." Energies 15, no. 17 (September 2, 2022): 6422. http://dx.doi.org/10.3390/en15176422.
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Considering requirements such as enhanced unit capacity, the geometric size of wind turbine blades has been increasing; this, in turn, results in a rapid increase in manufacturing costs. To this end, in this paper, we examine the aerodynamics of co-planar multi-rotor wind turbines to achieve higher unit capacity at a lower blade length. The multiple wind rotors are in the same plane with no overlaps. The ALM-LES method is used to investigate the interaction effect of the blade tip vortices, by revealing the regulation of aerodynamic performance and flow field characteristics of the multi-rotor wind turbines. The simulated results suggest an observable reduction in the blade tip vortices generated by blades located closely together, due to the breaking and absorption of the blade tip vortices by the two rotors. This results in increased aerodynamic performance and loads on the multi-rotor wind turbine. The influence between the blade tip vortex is mainly located in the range of 0.2 R from the blade tip, with this range leading to a significant increase in the lift coefficient. Thus, when the wind rotor spacing is 0.2 R, the interaction between the blade tip vortices is low.
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Stuermer, A., J. Yin, and R. Akkermans. "Progress in aerodynamic and aeroacoustic integration of CROR propulsion systems." Aeronautical Journal 118, no. 1208 (October 2014): 1137–58. http://dx.doi.org/10.1017/s0001924000009829.
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Abstract Contra-Rotating Open Rotor (CROR) propulsion systems have seen renewed interest as an economic and environmentally friendly powerplant for future transport aircraft. Installation effects, i.e. the mutual interactions between airframe components and the rotors, have a pronounced impact on the aerodynamic and aeroacoustic performance for this type of engine. In the past five years, DLR’s Institute of Aerodynamics and Flow Technology has performed a number of numerical studies investigating important aspects relating to engine-airframe integration of CROR engines. In this article an overview of coupled aerodynamic and aeroacoustic simulations investigating representative pusher-configuration CROR engines will be given, focusing on the impact on aerodynamic performance and aeroacoustics caused by the presence of a pylon, the potential for noise reduction by employing trailing-edge blowing at the pylon trailing edge as well as the performance and noise variations caused by different senses of rotation of the rotors. It is shown that the interaction with the pylon strongly impacts blade performance and front rotor noise emissions but that the use of active flow control in the form of pylon trailing-edge blowing can alleviate these adverse installation effects to a notable extent.
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He, Pan, and Jian Xia. "Study on the Influence of Low-Level Jet on the Aerodynamic Characteristics of Horizontal Axis Wind Turbine Rotor Based on the Aerodynamics–Controller Interaction Method." Energies 15, no. 8 (April 7, 2022): 2709. http://dx.doi.org/10.3390/en15082709.
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Accurate prediction of the aerodynamic characteristics of wind rotors subjected to various wind profiles is of considerable importance in the aerodynamics and structural design of wind turbines. As a very complex atmospheric phenomenon, the impact of a low-level jet (LLJ) on the aerodynamic characteristics of wind rotors is becoming more and more significant with the increase in wind turbine height. Additionally, during calculating the aerodynamic characteristics of the wind rotor, the known wind speed, rotor speed, and blade-pitch angle are generally required. However, when the wind profile is in the LLJ condition, it is difficult to determine the blade-pitch angle and rotor speed. Therefore, in this paper, the blade-element-momentum (BEM) method is exploited by considering the coupling with the generator-torque controller and blade-pitch controller. In order to solve the problem of the unknown rotor speed and blade-pitch angle under the LLJ condition, a C++ code is developed. Then, the influence of the LLJ on the aerodynamic characteristics of the wind rotor is exclusively examined. The research results show that the calculation method can precisely evaluate the rotor speed, blade-pitch angle, and aerodynamic characteristics of the wind rotor. The influence of the LLJ on the aerodynamic loads of the wind rotor is greater than that of the wind shear. When the LLJ is placed inside the rotor swept area, the aerodynamic loads of the blade exhibit two local maximums and local minimums with the variation of the azimuth angle in a rotation period. The closer the LLJ height is to the hub height, the greater the average aerodynamic loads of the wind rotor are, and the smaller the amplitude of aerodynamic loads of the blade is relative to the average value. When the LLJ height is positioned outside the rotor swept area, the change law of the aerodynamic loads of the blade would be similar to that of the wind subjected to a very strong wind shear inflow. This study provides a crucial reference for a more rational assessment of the aerodynamic characteristics of wind turbines under the action of complex wind profiles, as well as revealing the influence of the LLJ on the aerodynamic characteristics of wind turbines.
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Tran, Ngoc Khanh, Van Quang Dao, Phu Khanh Nguyen, Thi Kim Dung Hoang, and Van Khang Nguyen. "Numerical Investigations of Aerodynamics Characteristics of Main Rotors in Helicopter UAV Used for Pesticide Spraying in Agriculture." Applied Mechanics and Materials 889 (March 2019): 425–33. http://dx.doi.org/10.4028/www.scientific.net/amm.889.425.
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In the last several decades past, Helicopters UAVs (Unmanned Aerial Vehicles) have quickly developed and day by day, they play an important role in human life. As it is well-known, helicopters UAV make some outstanding characteristics such as light weight, flexibility and particularly automatically controlled. By applying these characteristics, we research and manufacture Helicopter UAV using for spraying pesticide in agriculture. One of the most important components is main rotor because main rotor generated thrust, drag and momentum. Helicopters UAV efficient changed depending on main rotor. The research works focus on aerodynamics characterization of main rotor in helicopter UAV. This work uses CFD tool in ANSYS CFX software to calculate the aerodynamics parameters generated by main rotor using in UAV. The aim is to characterize the aerodynamics characteristics such as thrust, drag, pressure, aerodynamics quality on the different flight modes (hover, vertical and forward flight). Firstly, the simulations are carried out in hover flight mode with different blade pitch angles. The results are compared to experiment date in another research to validate numerical results. Then, the simulations are carried out in vertical flight mode and forward flight mode. The results showed that thrust and drag coefficient creased with increasing blade pitch angle. When blade pitch angle started from 1800, thrust coefficient decreased but drag coefficient increased sharply. The rotor performance was measured by aerodynamics quality and numerical results showed that the best rotor performance was at 900. In the vertical flight mode, the thrust and drag coefficient decreased with increasing vertical velocity but rotor performance increased slightly. The best vertical velocity for vertical flight is around 2 m/s and 3 m/s. Finally, in forward flight mode, the aerodynamics characterizations of rotors depended on azimuthal angular position of blade or time. Our helicopter operates in environment with light gust. The results showed the change of aerodynamics coefficient to time. Both thrust and drag coefficient changed but the rotor performance did not change much.
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Jiang, Yuening, Hai Li, and Hongguang Jia. "Aerodynamics Optimization of a Ducted Coaxial Rotor in Forward Flight Using Orthogonal Test Design." Shock and Vibration 2018 (May 28, 2018): 1–9. http://dx.doi.org/10.1155/2018/2670439.
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To investigate the aerodynamic complexities involved in the combination of freestream and propeller’s suction flow field of ducted coaxial rotors system in forward flight, an orthogonal L16(43) test design has been applied to optimize the design parameters including forward speed, pitch angle, and axial spacing between rotors. Multiblock grids and Multiple Frame of Reference (MFR) method are adopted for calculating aerodynamic performance of the system, hover characteristic was compared with experimental data obtained from the test stand, and the thrust performance is well predicted for various rotor spacing and a range of rpm. This solution approach is developed for the analytical prediction of forward flight and the simulation results indicated that the design parameters influenced lift, drag, and torque reduced in the order: wind speed > rotor spacing > pitch angle, wind speed > pitch angle, and rotor spacing > wind speed > pitch angle, respectively. The optimal rotor spacing and pitch angle were determined to maximize the aerodynamic performance considering high lift, low drag, and trimmed torque.
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Tchakoua, Pierre, René Wamkeue, Mohand Ouhrouche, Ernesto Benini, and Gabriel Ekemb. "Electric Circuit Model for the Aerodynamic Performance Analysis of a Three-Blade Darrieus-Type Vertical Axis Wind Turbine: The Tchakoua Model." Energies 9, no. 10 (October 14, 2016): 820. http://dx.doi.org/10.3390/en9100820.
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The complex and unsteady aerodynamics of vertical axis wind turbines (VAWTs) pose significant challenges for simulation tools. Recently, significant research efforts have focused on the development of new methods for analysing and optimising the aerodynamic performance of VAWTs. This paper presents an electric circuit model for Darrieus-type vertical axis wind turbine (DT-VAWT) rotors. The novel Tchakoua model is based on the mechanical description given by the Paraschivoiu double-multiple streamtube model using a mechanical‑electrical analogy. Model simulations were conducted using MATLAB for a three-bladed rotor architecture, characterized by a NACA0012 profile, an average Reynolds number of 40,000 for the blade and a tip speed ratio of 5. The results obtained show strong agreement with findings from both aerodynamic and computational fluid dynamics (CFD) models in the literature.
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Wu, Huagen, Jiankang Liu, Yuqi Shen, Mengtao Liang, and Beiyu Zhang. "Research on Performance of Variable-Lead Rotor Twin Screw Compressor." Energies 14, no. 21 (October 24, 2021): 6970. http://dx.doi.org/10.3390/en14216970.
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Twin-screw compressors are widely used in aerodynamics, refrigeration and other fields. The screw rotors are the core component of the screw compressor and affect the performance of the compressor. This paper focuses on variable-lead rotors. A thermal process simulation model considering leakage is established to calculate the efficiency of the compressor. Different lead change methods are compared by evaluating the contact line, exhaust port and simulation results. The results show that the compressor obtains better performance when the lead decreases rapidly on the discharge side. Furthermore, the effects of the wrap angle and internal volume ratio on variable-lead rotors are studied. The work provides a reference for the design of the screw compressor rotor.
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Redchyts', Dmytro O. "Numerical simulation of wind turbine rotors aerodynamics." PAMM 7, no. 1 (December 2007): 2100049–50. http://dx.doi.org/10.1002/pamm.200700521.
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Torabi Asr, Mahdi, Reza Osloob, and Faizal Mustapha. "Double-Stage H-Darrieus Wind Turbine - Rotor Aerodynamics." Applied Mechanics and Materials 829 (March 2016): 21–26. http://dx.doi.org/10.4028/www.scientific.net/amm.829.21.
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H-Darrieus wind turbines, due to their simple design and relatively low manufacturing costs have recently received much attention particularly for standalone applications. However start-up issues associated with their operation restricted their operation in areas of low average wind speed and encourages engineers to develop novel design. Several design proposed in this way but in most cases design came up with complex sensing mechanisms and mechanical actuators or high cost manufacturing parts. A recent rotor design called double Darrieus rotor proposed as a German patent case bridged these complexities appropriately. The aim of present study is to investigate this innovative design from aerodynamic point of view by means of validated CFD techniques. A flow-driven simulation setup based on 6DOF calculations employed in order to study rotor operation from stand still until peak performance obtained. Results from these precise modeling reveal the superiority of the proposed double-stage design in compare with the original H-Darrieus rotors in terms of start-up behavior and optimum performance.
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Hu, Y., F. Du, and H. L. Zhang. "Investigation of unsteady aerodynamics effects in cycloidal rotor using RANS solver." Aeronautical Journal 120, no. 1228 (May 10, 2016): 956–70. http://dx.doi.org/10.1017/aer.2016.38.
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ABSTRACTThe cycloidal propeller for a Micro-Aerial Vehicle (MAV)-scale cyclogyro in hover was studied using a 2D Reynolds-averaged Navier-Stokes equations solver. The effects of the blade dynamic stall, parallel Blade Vortex Interaction (BVI), inflow variation and flow curvature were discussed, based on the results of numerical simulation. The results from the 2D Computational Fluid Dynamics simulation indicated that the blade of the cycloidal rotor is actually performing a pitching oscillation, if observed in a moving reference frame. The dynamic stall vortices shed from the upstream blade cause intense parallel BVI on the downstream blade. The interaction will induce upwash and downwash on the downstream blade. This changes the effective reduced frequency and actually delays the stall of the blade, which is beneficial to the thrust generation. There is also strong downwash in the rotor cage and it changes the inflow velocity experienced by the blade. The downwash and flow curvature can either be beneficial or harmful to the thrust generation. The combined effects of dynamic stall, parallel BVI, inflow variation and flow curvature cause large aerodynamic force peaks and ensure the cycloidal rotors work at very low rotation speeds with high thrust. This guarantees that the cycloidal rotors possess at least the same level of hover efficiency as screw propellers.
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Guérin, S., R. Schnell, and R. G. Becker. "Performance prediction and progress towards multi-disciplinary design of contra-rotating open rotors." Aeronautical Journal 118, no. 1208 (October 2014): 1159–79. http://dx.doi.org/10.1017/s0001924000009830.
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Abstract At DLR’s Institute of Propulsion Technology, the prediction tools and multi-disciplinary optimisation strategies developed for turbofan engines have been extended to contra-rotating open rotors (CROR). Thereby the objective has been to appraise and improve the performance of CROR engines and thus to reduce their environmental impact. The present paper reviews the intermediate progress achieved in this scope. The prediction is based on analytical and CFD methods and covers the fields of engine performance analysis, aerodynamics and acoustics. The aerodynamic and acoustic results could be partly validated through the comparison to experimental data obtained from wind-tunnel tests. In a multi-disciplinary approach the aforementioned aspects are optimised together. First results of an aero-acoustic optimisation are presented. Furthermore this paper undertakes some comparison between high-bypass ratio turbofan engines and open-rotor concepts.
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Jamieson, P., C. Simao Ferreira, P. Dalhoff, S. Störtenbecker, M. Collu, E. Salo, D. McMillan, J. McMorland, L. Morgan, and A. Buck. "Development of a multi rotor floating offshore system based on vertical axis wind turbines." Journal of Physics: Conference Series 2257, no. 1 (April 1, 2022): 012002. http://dx.doi.org/10.1088/1742-6596/2257/1/012002.
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Abstract The upscaling of wind turbines results in fewer units per installed MW reducing infrastructure and maintenance costs of offshore wind farms. Multi rotor systems (MRS), comprising many wind turbine rotors on a single support structure, are potentially a means to maximize the upscaling benefit in achieving larger unit capacities than is feasible or economic with the conventional, 3-bladed horizontal axis wind turbine (HAWT). The MRS has an inherent upscaling advantage which, for a system with many rotors compared to a single rotor, reduces the total weight and cost of rotor-nacelle assemblies by a large factor. An innovative MRS design is presented based on vertical axis wind turbine (VAWT) rotors of the 2-bladed, H-type. Many disadvantages of VAWT design compared to HAWT in a single rotor system (reduced power performance and higher drive train torque, for example) are resolved in the MRS configuration. In addition, reduced component number and simpler components is advantageous for reliability and O&M cost. This MRS concept has many synergies arising from the choice of VAWT rotors. Results comprise a high-level evaluation of system characteristics and the first stage of more detailed investigation of aerodynamics of the high aspect ratio VAWT.
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Herbert-Acero, José F., Jaime Martínez-Lauranchet, Oliver Probst, Santos Méndez-Díaz, Krystel K. Castillo-Villar, Manuel Valenzuela-Rendón, and Pierre-Elouan Réthoré. "A Hybrid Metaheuristic-Based Approach for the Aerodynamic Optimization of Small Hybrid Wind Turbine Rotors." Mathematical Problems in Engineering 2014 (2014): 1–18. http://dx.doi.org/10.1155/2014/746319.
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This work presents a novel framework for the aerodynamic design and optimization of blades for small horizontal axis wind turbines (WT). The framework is based on a state-of-the-art blade element momentum model, which is complemented with the XFOIL 6.96 software in order to provide an estimate of the sectional blade aerodynamics. The framework considers an innovative nested-hybrid solution procedure based on two metaheuristics, the virtual gene genetic algorithm and the simulated annealing algorithm, to provide a near-optimal solution to the problem. The objective of the study is to maximize the aerodynamic efficiency of small WT (SWT) rotors for a wide range of operational conditions. The design variables are (1) the airfoil shape at the different blade span positions and the radial variation of the geometrical variables of (2) chord length, (3) twist angle, and (4) thickness along the blade span. A wind tunnel validation study of optimized rotors based on the NACA 4-digit airfoil series is presented. Based on the experimental data, improvements in terms of the aerodynamic efficiency, the cut-in wind speed, and the amount of material used during the manufacturing process were achieved. Recommendations for the aerodynamic design of SWT rotors are provided based on field experience.
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Qi, Haotian, Ping Wang, Linsong Jiang, and Yang Zhang. "Investigation on Aerodynamic Noise Characteristics of Coaxial Rotor in Hover." Applied Sciences 12, no. 6 (March 9, 2022): 2813. http://dx.doi.org/10.3390/app12062813.
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A numerical method based on Reynolds Averaged Navier–Stokes (RANS) equations and a high-efficiency trim model is developed to simulate the aerodynamics of a coaxial rotor. Farassat 1A equations are used for the prediction of thickness and loading noise. Hover cases of different thrust coefficients with torque balance are conducted. The sound pressure history of different observation points positioned below the rotor disk plane is analyzed. Results indicate that the special noise characteristics of the coaxial rotor are mainly caused by the noise superposition of the twin rotors and the unsteady loads of aerodynamic interaction. A new kind of impulsive loading noise is induced by the blade-meeting interaction. In contract to the single rotor, the loading noise of a coaxial rotor has a much larger sound pressure level in the high-frequency band. The loading noise is obviously enhanced around the blade-meeting azimuths. The maximum noise of the coaxial rotor is located immediately below the rotor disk center, while for the single rotor, it is the minimum location.
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Filippone, Antonio. "Rapid Estimation of Airfoil Aerodynamics for Helicopter Rotors." Journal of Aircraft 45, no. 4 (July 2008): 1468–72. http://dx.doi.org/10.2514/1.35560.
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Miller, R. H. "Simplified Treatment of Unsteady Aerodynamics for Lifting Rotors." Journal of Aircraft 38, no. 3 (May 2001): 590–92. http://dx.doi.org/10.2514/2.2809.
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Benini, Ernesto, and Roberto Biollo. "Aerodynamics of swept and leaned transonic compressor-rotors." Applied Energy 84, no. 10 (October 2007): 1012–27. http://dx.doi.org/10.1016/j.apenergy.2007.03.003.
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van Kuik, G. A. M., D. Micallef, I. Herraez, A. H. van Zuijlen, and D. Ragni. "The role of conservative forces in rotor aerodynamics." Journal of Fluid Mechanics 750 (June 9, 2014): 284–315. http://dx.doi.org/10.1017/jfm.2014.256.
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AbstractThe theory to predict the performance and loads on rotors (propellers, screws, windmills) has a history of more than a century. Apart from modern computational fluid dynamics and vortex panel models taking the true blade geometry into account, most other models proceed from an infinitely thin actuator disc or line. These models assume an externally defined force field distributed at the disc or line, representing the loads on the real rotor. Given this force field, the flow is solved by momentum balances or by the equations of motion. The use of external force fields was discussed in textbooks of the first decades of the 20th century, but has received little attention since then. This paper investigates the higher-order effect of adding thickness to the actuator disc or changing the actuator line to a blade with cross-sectional dimensions. For the generation of a Rankine vortex by a force field acting on an actuator disc with thickness, an exact solution has been found in which not only the thrust and torque determine the flow, but also a radial force. This force is conservative, in contrast to the other force components. For rotor blades, a conservative normal and radial force acting on the chordwise bound vorticity is present. This explains the experimentally observed inboard motion of the tip vortex of model wind turbine rotors before the wake induction field drives it outboard. Simulations by computational fluid mechanics and a vortex panel code reproduce the inboard motion, but an actuator line analysis, in which the chordwise vorticity is absent, does not. The conservative load is only $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}1\mbox{--}2\, \%$ of the thrust on the entire blade but ${\approx }10\, \%$ of the thrust at the tip ($r/R>0.9$). Conservative forces at the disc and rotor blade vanish for vanishing disc thickness or blade cross-section, so play no role in any of the infinitely thin actuator disc or line methods. However, if higher-order effects of non-zero dimensions are to be modelled, the conservative force field has to be included.
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de Andrade, Donizeti, and David A. Peters. "Coupling of a State-Space Inflow to Nonlinear Blade Equations and Extraction of Generalized Aerodynamic Force Mode Shapes." Applied Mechanics Reviews 46, no. 11S (November 1, 1993): S295—S304. http://dx.doi.org/10.1115/1.3122648.
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The aeroelastic stability of helicopter rotors in hovering flight has been investigated by a set of generalized dynamic wake equations and hybrid equations of motion for an elastic blade cantilevered in bending and having a torsional root spring to model pitch-link flexibility. The generalized dynamic wake model employed is based on an induced flow distribution expanded in a set of harmonic and radial shape functions, including undetermined time dependent coefficients as aerodynamic states. The flow is described by a system of first-order, ordinary differential equations in time, for which the pressure distribution at the rotor disk is expressed as a summation of the discrete loadings on each blade, accounting simultaneously for a finite number of blades and overall rotor effects. The present methodology leads to a standard eigenanalysis for the associated dynamics, for which the partitioned coefficient matrices depend on the numerical solution of the blade equilibrium and inflow steady-state equations. Numerical results for a two-bladed, stiff-inplane hingeless rotor with torsionally soft blades show the importance of unsteady, three-dimensional aerodynamics in predicting associated generalized aerodynamic force mode shapes.
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Qin, Chao (Chris), Eric Loth, Daniel S. Zalkind, Lucy Y. Pao, Shulong Yao, D. Todd Griffith, Michael S. Selig, and Rick Damiani. "Active rotor coning for a 25 MW downwind offshore wind turbine." Journal of Physics: Conference Series 2265, no. 3 (May 1, 2022): 032022. http://dx.doi.org/10.1088/1742-6596/2265/3/032022.
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Abstract A two-bladed downwind turbine system was upscaled from 13.2 MW to 25 MW by redesigning aerodynamics, structures, and controls. In particular, three 25-MW rotors were developed, and the final version is a fully redesigned model of the original rotor. Despite their radically large sizes, it was found that these 25-MW turbine rotors satisfy this limited set of structural design drivers at the rated condition and that larger blade lengths are possible with conewise load-alignment. In addition, flapwise morphing (varying the cone angle with a wind-speed schedule) was investigated to minimize mean and fluctuating blade root bending loads using steady inflow proxies for the maximum and lifetime damage equivalent load moments. Compared to the fixed coned rotor case, morphing can provide an Annual Energy Production (AEP) increase of 6%, and the maximum blade root flapwise bending moment increases 21% (still under the constraint, i.e., 10% of the ultimate moments) as a trade-off. The resulting series of 25-MW rotors can be a valuable baseline for further development and assessment of ultra-large-scale wind turbines.
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BAZILEVS, YURI, MING-CHEN HSU, KENJI TAKIZAWA, and TAYFUN E. TEZDUYAR. "ALE-VMS AND ST-VMS METHODS FOR COMPUTER MODELING OF WIND-TURBINE ROTOR AERODYNAMICS AND FLUID–STRUCTURE INTERACTION." Mathematical Models and Methods in Applied Sciences 22, supp02 (July 25, 2012): 1230002. http://dx.doi.org/10.1142/s0218202512300025.
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We provide an overview of the Arbitrary Lagrangian–Eulerian Variational Multiscale (ALE-VMS) and Space–Time Variational Multiscale (ST-VMS) methods we have developed for computer modeling of wind-turbine rotor aerodynamics and fluid–structure interaction (FSI). The related techniques described include weak enforcement of the essential boundary conditions, Kirchhoff–Love shell modeling of the rotor-blade structure, NURBS-based isogeometric analysis, and full FSI coupling. We present results from application of these methods to computer modeling of NREL 5MW and NREL Phase VI wind-turbine rotors at full scale, including comparison with experimental data.
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Hartin, John R. "Evaluation of Prediction Methodology for Blade Loads on a Horizontal Axis Wind Turbine." Journal of Solar Energy Engineering 112, no. 4 (November 1, 1990): 315–19. http://dx.doi.org/10.1115/1.2929941.
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The accurate prediction of horizontal axis, wind turbine cyclic blade loads is critical in the design of a machine that is fatigue life limited. A rotor code called LOADS has been developed that analyzes blade loads for rigid-hub rotors of simple geometry but includes blade flap-wise flexing and unsteady aerodynamics. The code is described and the results of its application to the SERI Combined Experiment Tests using turbulent wind simulation are presented with some initial conclusions regarding the accuracy of the results.
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Stauter, R. C., R. P. Dring, and F. O. Carta. "Temporally and Spatially Resolved Flow in a Two-Stage Axial Compressor: Part 1—Experiment." Journal of Turbomachinery 113, no. 2 (April 1, 1991): 219–25. http://dx.doi.org/10.1115/1.2929087.
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The fluid dynamics of turbomachines are extremely complex, due in part to the aerodynamic interactions between rotors and stators. It is necessary to acquire fluid dynamic data that reflect the interactive nature of a turbomachine to correlate with the fluid dynamics predicted from modern analyses. The temporal and spatial variations in the midspan aerodynamics of the second stage of a two-stage compressor have been studied with a two-component LDV system. Spatial variations were examined by traversing the LDV probe volume through a dense matrix of both axial and circumferential positions, while temporal resolution was achieved by acquiring all data as a function of the instantaneous rotor position. Hence, the data set reveals rotor and stator wake structure and decay in both the stationary and rotating frames of reference. The data also compared very favorably with extensive pneumatic measurements previously acquired in this compressor. In Part 2 of the paper, the data are used in the assessment of a prediction of the flow in the compressor using a time-accurate, thin-layer, two-dimensional Navier–Stokes analysis.
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Krishnan, Navaneetha, Axelle Viré, and Rikus van de Klippe. "Study of a passive pitching rotor using blade element momentum theory coupled to a rigid-body model." Journal of Physics: Conference Series 2265, no. 3 (May 1, 2022): 032057. http://dx.doi.org/10.1088/1742-6596/2265/3/032057.
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Abstract Misaligned wind turbine rotors experience uneven loads because of two effects: dissymmetry of lift, and skewed wake effect. Rotor-crafts that have a similar problem introduce various mechanisms to combat this — one of them is to add a δ3-hinge. The hinge provides the blade with an additional degree of freedom to relieve the unbalanced loads; in theory, it is a self-correcting mechanism. In this work, we couple a blade element momentum (BEM) approach for the aerodynamics to a rigid-body model that simulates the hinge rotation. The results from BEM are used to identify the working mechanisms of the hinged rotor and highlight the strengths and weaknesses of such a rotor.
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Tang, Peng, Fei Wang, and Yuehong Dai. "Controller Design for Different Electric Tail Rotor Operating Modes in Helicopters." International Journal of Pattern Recognition and Artificial Intelligence 33, no. 08 (June 25, 2019): 1959022. http://dx.doi.org/10.1142/s0218001419590225.
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The nonlinear aerodynamics and new kinds of operation associated with helicopter electric tail rotors (ETRs) make accurate speed tracking control under complex flight conditions a key challenge confronting designers. In this paper, we present an electric propulsion system for tail rotors that uses a high-power-density permanent magnet motor. The management of aerodynamic disturbance rejection and accurate speed control are aspects of ETR design that require particularly close attention. To this end, we have developed a speed controller that is based on an active disturbance rejection control (ADRC) technique that can handle fixed speed and adjustable pitch-angle modes. We have also applied a linear extended state observer (LESO) with a self-tuning bandwidth to estimate fluctuations in the drive system. For variable speeds, a simple controller combined with an adaptive radial basis function (RBF) observer and nonlinear state error feedback using ADRC was designed to replace LESO while avoiding any dependence on the system parameters. The stability of the controllers was analyzed and their effectiveness was verified using a simulation platform. Test results showed that the propulsion system is able to achieve fast dynamic response and aerodynamic disturbance rejection.
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Thirumaleshwar Hegde, Navya, V. I. George, C. Gurudas Nayak, and Kamlesh Kumar. "Transition flight modeling and robust control of a VTOL unmanned quad tilt-rotor aerial vehicle." Indonesian Journal of Electrical Engineering and Computer Science 18, no. 3 (June 1, 2020): 1252. http://dx.doi.org/10.11591/ijeecs.v18.i3.pp1252-1261.
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<span>The development of fully autonomous Unmanned Aerial Vehicles (UAV) plays a major contribution towards reducing the risk to human life in various applications including rescue teams, border patrol, police and inspection of buildings, pipelines, coasts, and terrains. Tiltrotor hybrid UAV exhibit special application value due to its unique rotor structure. The variation in the model dynamics and aerodynamics due to the tilting rotors are the major key issues and challenges which attracted the attention of many researchers. This vehicle combines the hovering capabilities of a helicopter along with the high-speed cruise capabilities of a conventional airplane by tilting its four rotors. In the present research work, the authors attempt to model a quad tilt rotor UAV using Newton-Euler formulation. A dynamic model of the vehicle is derived mathematically for horizontal, vertical and transition flight modes. A robust H-infinity control strategy is proposed, evaluated and analyzed through simulation to control the flight dynamics of the different modes of the UAV. Simulation results shows that the tiltrotor UAV achieves transition successfully.</span>
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de Montaudouin, J., N. Reveles, and M. J. Smith. "Computational aeroelastic analysis of slowed rotors at high advance ratios." Aeronautical Journal 118, no. 1201 (March 2014): 297–313. http://dx.doi.org/10.1017/s0001924000009131.
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Abstract The aerodynamic and aeroelastic behaviour of a rotor become more complex as advance ratios increase to achieve high-speed forward fight. As the rotor blades encounter large regions of cross and reverse flows during each revolution, strong variations in the local Mach regime are encountered, inducing complex elastic blade deformations. In addition, the wake system may remain in the vicinity of the rotor, adding complexity to the blade loading. The aeroelastic behaviour of a model rotor with advance ratios ranging from 0·5 to 2·0 has been evaluated with aerodynamics provided via a computational fluid dynamics (CFD) method. Significant radial blade-vortex interaction can occur at a high advance ratio; the advance ratio at which this occurs is dependent on the rotor configuration. This condition is accompanied by high vibratory loads, peak negative torsion, and peak torsion and in-plane loads. The high vibratory loading increases the sensitivity of the trim model, so that at some high advance ratios the vibratory loads must be filtered to achieve a trimmed state.
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Copenhaver, W. W., E. R. Mayhew, C. Hah, and A. R. Wadia. "The Effect of Tip Clearance on a Swept Transonic Compressor Rotor." Journal of Turbomachinery 118, no. 2 (April 1, 1996): 230–39. http://dx.doi.org/10.1115/1.2836630.
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An experimental and numerical investigation of detailed tip clearance flow structures and their effects on the aerodynamic performance of a modern low-aspect-ratio, high-throughflow, axial transonic fan is presented. Rotor flow fields were investigated at two clearance levels experimentally, at tip clearance to tip blade chord ratios of 0.27 and 1.87 percent, and at four clearance levels numerically, at ratios of zero, 0.27, 1.0, and 1.87 percent. The numerical method seems to calculate the rotor aerodynamics well, with some disagreement in loss calculation, which might be improved with improved turbulence modeling and a further refined grid. Both the experimental and the numerical results indicate that the performance of this class of rotors is dominated by the tip clearance flows. Rotor efficiency drops six points when the tip clearance is increased from 0.27 to 1.87 percent, and flow range decreases about 30 percent. No optimum clearance size for the present rotor was indicated. Most of the efficiency change occurs near the tip section, with the interaction between the tip clearance flow and the passage shock becoming much stronger when the tip clearance is increased. In all cases, the shock structure was three dimensional and swept, with the shock becoming normal to the endwall near the shroud.
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Shaza Rae Selvarajoo, Zulfaa Mohamed-Kassim, and Wei Shyang Chang. "Aerodynamic Characterization of Darrieus Turbines during Self-Start at different Azimuthal Quadrants." CFD Letters 15, no. 2 (January 20, 2023): 126–42. http://dx.doi.org/10.37934/cfdl.15.2.126142.
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One key technology to extract kinetic energy from wind and water is the vertical-axis turbines. However, these flows and currents often fluctuate, forcing the turbine rotors to operate in transient modes. To improve rotor performance, the transient aerodynamic characteristics across the four quadrants of the rotor sweep must be well-understood. We address this need by simulating the transient process of a 3-bladed Darrieus turbine rotor during self-start using the dedicated turbine aerodynamics software QBlade. The simulated transient evolution of the rotor compares well against the experimental and computational-fluid-dynamics data from previous studies. When the rotor self-starts within its first three cycles, its torque is contributed differently from each of the four quadrants. Respectively, its windward and upwind quadrant positively contributes by up to 43% and 326% each to the overall torque, and the leeward and downwind quadrant negatively reduces by up to -346% and -85% each from the overall torque. However, upon reaching steady state, these roles change where the positive torques are contributed by the upwind and leeward quadrants by up to 120% and 10%, respectively, while the negative torques are caused by the downwind and windward quadrants by up to -18% and -13%, respectively. Insights into these rotor dynamics can be later used to propose newer rotor designs or operations to improve the transient performance of the turbine
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Shaw, S. T., and N. Qin. "Study of the aerodynamics of in-plane motion." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 215, no. 2 (February 1, 2001): 89–104. http://dx.doi.org/10.1243/0954410011531790.
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A computational analysis is performed of the unsteady aerodynamics associated with the blade sections of helicopter rotors in forward flight. The unsteady flow is studied through solutions of the two- dimensional Reynolds averaged Navier-Stokes equations together with a strongly coupled two-equation model of turbulence. Two motions are studied. The first motion is that of an aerofoil subjected to harmonic in-plane oscillations. The influence of advance ratio and reduced frequency is investigated. It is shown that, in the absence of shock waves, the flow is periodic with a reduced frequency equal to that of the forcing motion. However, the flow development lags behind the forcing motion. Furthermore, for constant reduced frequency the phase lag is independent of advance ratio. In addition to harmonic motion, the aerodynamic response to a step change in Mach number is investigated. Using an assumed form of the response of lift coefficient to a step change in Mach number, a lift transfer operator for step changes in Mach number is obtained in the Laplace domain. An analytical expression for the response to harmonic Mach number oscillations is then obtained from the transfer operator. The resulting formulation for the aerodynamic response confirms that the lag between the forcing motion and the aerodynamic response is independent of advance ratio.
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Kothe, L. B., and A. P. Petry. "NUMERICAL AND EXPERIMENTAL STUDY OF A TWO-STAGE SAVONIUS WIND TURBINE." Revista de Engenharia Térmica 18, no. 2 (December 16, 2019): 52. http://dx.doi.org/10.5380/reterm.v18i2.70794.
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This article presents a numerical and experimental study of vertical axis wind turbine performance comparison involving a two-stage Savonius rotor with similar parameters. The experimental study is conducted in the aerodynamic tunnel at the Fluid Mechanics Laboratory of the Federal University of Rio Grande do Sul. The aerodynamics rotors are manufactured by 3D prototyping technique. Numerical simulations are performed using the Finite Volumes Method performed by the solution of the Reynolds Averaged Navier-Stokes (RANS) and continuity equations using the SST k-ω turbulence model. The numerical domain is modeled in order to maintain the same characteristics of the experimental model. The mesh quality is evaluated through the GCI (Grid Convergence Index) method. The static and dynamic torque coefficients and the power coefficients are compared. The tests are made without blockage corrections due to the small blockage ratio from 7.5%. Results show that the turbine has a positive static torque coefficient for any rotor angles. The dynamic torque reaches the maximum value for a tip speed ratio (λ) of 0.2 for the experimental and numerical cases. The relative difference between the numerical simulations and the experimental results are between 3.8% and 13.4%.
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Garipova, Lyaysan Ildusovna, Andrei Sergeevich Batrakov, Alexander Nikolaevich Kusyumov, Sergey Anatolievich Mikhaylov, and George Barakos. "Aerodynamic and acoustic analysis of helicopter main rotor blade tips in hover." International Journal of Numerical Methods for Heat & Fluid Flow 26, no. 7 (September 5, 2016): 2101–18. http://dx.doi.org/10.1108/hff-08-2015-0348.
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Purpose The design of main rotor blade tips is of interest to helicopter manufactures since the tip details affect the performance and acoustics of the rotor. The paper aims to discuss this issue. Design/methodology/approach In this paper, computation fluid dynamics is used to simulate the flow around hovering helicopter blades with different tip designs. For each type of blade tip a parametric study on the shape is also conducted for comparison calculations were performed the constant rotor thrust condition. The collective pitch and the cone angles of the blades were determined by at an iterative trimming process. Findings Analysis of the distributed blade loads shows that the tip geometry has a significant influence on aerodynamics and aeroacoustics especially for stations where blade loading is high. Originality/value The aeroacoustic characteristics of the rotors were obtained using Ffowcs Williams-Hawkings equations.