Academic literature on the topic 'Lifting line models'
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Journal articles on the topic "Lifting line models"
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Bottasso, Carlo L., Stefano Cacciola, and Xabier Iriarte. "Calibration of wind turbine lifting line models from rotor loads." Journal of Wind Engineering and Industrial Aerodynamics 124 (January 2014): 29–45. http://dx.doi.org/10.1016/j.jweia.2013.11.003.
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Epps, Brenden. "On the Rotor Lifting Line Wake Model." Journal of Ship Production and Design 33, no. 01 (February 1, 2017): 31–45. http://dx.doi.org/10.5957/jspd.2017.33.1.31.
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This article comments on the wake model used in moderately loaded rotor lifting line theory for the preliminary design of propellers and horizontal-axis turbines. Mathematical analysis of the classic wake model reveals an inconsistency between the induced velocities numerically computed by the model versus those theoretically predicted by the model. An improved wake model is presented, which better agrees with theory than previous models and thus improves the numerical consistency and robustness of rotor lifting line design algorithms. The present wake model analytically relates the pitch of the trailing vortices to the pitch of the total inflow computed at the lifting line control points. For conciseness, the article focuses on the propeller case, although both propeller and horizontal-axis turbine examples are presented.
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Duque, Earl P. N., Michael D. Burklund, and Wayne Johnson. "Navier-Stokes and Comprehensive Analysis Performance Predictions of the NREL Phase VI Experiment." Journal of Solar Energy Engineering 125, no. 4 (November 1, 2003): 457–67. http://dx.doi.org/10.1115/1.1624088.
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A lifting-line code, CAMRAD II, and a Reynolds-Averaged Navier-Stokes code, OVERFLOW-D, were used to predict the aerodynamic performance of a two-bladed horizontal axis wind turbine. All computations were compared with experimental data that was collected at the NASA Ames Research Center 80-by-120-foot Wind Tunnel. Lifting-line computations were performed for both axial and yawed operating conditions while the Navier-Stokes computations were performed for only the axial conditions. Various stall delay models and dynamic stall models were used by the CAMRAD II code. For axial operating conditions, the predicted rotor performance varied significantly, particularly for stalled wind speeds. The lifting-line required the use of stall delay models to obtain the proper stall behavior, yet it still has difficulty in predicting the proper power magnitude in stall. The Navier-Stokes method captures the stall behavior and gives a detailed insight into the fluid mechanics of the stall behavior.
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Sugar-Gabor, O. "A general numerical unsteady non-linear lifting line model for engineering aerodynamics studies." Aeronautical Journal 122, no. 1254 (June 6, 2018): 1199–228. http://dx.doi.org/10.1017/aer.2018.57.
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ABSTRACTThe lifting-line theory is widely used for obtaining aerodynamic performance results in various engineering fields, from aircraft conceptual design to wind-power generation. Many different models were proposed, each tailored for a specific purpose, thus having a rather narrow applicability range. This paper presents a general lifting-line model capable of accurately analysing a wide range of engineering problems involving lifting surfaces, both steady-state and unsteady cases. It can be used for lifting surface with sweep, dihedral, twisting and winglets and includes features such as non-linear viscous corrections, unsteady and quasi-steady force calculation, stable wake relaxation through fictitious time marching and wake stretching and dissipation. Possible applications include wing design for low-speed aircraft and unmanned aerial vehicles, the study of high-frequency avian flapping flight or wind-turbine blade design and analysis. Several validation studies are performed, both steady-state and unsteady, the method showing good agreement with experimental data or numerical results obtained with more computationally expensive methods.
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Yang, Wang, Ran Yang, Juanjuan Li, Lin Wei, and Jian Yang. "Optimized tuber-lifting velocity model for cassava harvester design." Advances in Mechanical Engineering 10, no. 9 (September 2018): 168781401880086. http://dx.doi.org/10.1177/1687814018800863.
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The lack of optimized lifting velocity model for cassava tuber lifting results in the shortage of evidence of design of lifting velocity control system and large harvest loss during mechanized harvesting of cassava. First, an optimized velocity model of manually pulling tubers and a velocity model of mechanical lifting tubers were established using physical experiments. And then using the mechanical tuber-lifting velocity model, the mathematical models between coefficients of mechanical tuber-lifting velocity model and cassava harvesting quality were established based on numerical simulation and regression analysis. Moreover, the coefficients were optimized using optimization method and the mechanical optimal tuber-lifting velocity model was obtained. Finally, the optimization results and the mechanical optimal tuber-lifting velocity model were verified by simulation and physical experiment, respectively. The results show that the optimized manual pulling velocity model can be superimposed by a line and a sine curve or a concave downward parabola and a sine curve. The optimal coefficients’ combination of mechanical tuber-lifting velocity model is shown as follows: A = 0.056, B = 0.521, C = 0.048, D = 0.086, E = 38.506, and F = 1.165. The mechanical optimal tuber-lifting velocity model’s expression is simple and the model is reasonable. The mechanical optimal tuber-lifting velocity model, which is established using physical experiments, simulation method, and optimization technique, has great significance for designing lifting velocity control system.
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Hwang, Jaejin, Gregory G. Knapik, Jonathan S. Dufour, and William S. Marras. "A Comparison of Performance Between Straight-Line Muscle and Curved Muscle Models." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 61, no. 1 (September 2017): 1339–40. http://dx.doi.org/10.1177/1541931213601817.
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The straight-line muscle biomechanical models of the lumbar spine have been utilized to predict spinal loads to assess the potential risk of work-related injuries. The curved muscle paths have been suggested to realistically simulate muscles’ behavior in complex lumbar motions. However, the effect of curved muscle paths on the modeling performances and spinal loads in the lumbar spine model during complex lifting exertions has not been fully investigated. The objective of this study was to characterize the differences in modeling performances and spinal loads between the conventional straight-line muscle model and the curved muscle model of the lumbar spine. Twelve subjects (6 males and 6 females) participated in this study. Mean values and standard deviations of age, body mass, and height of all subjects were 26.6 (5.3) years, 73.6 (13.3) kg, and 172.7 (5.4) cm, respectively. Electromyographic (EMG) activities with surface electrodes (Motion Lab Systems MA300-XVI, Baton Rouge, Louisiana, USA) were collected over 10 trunk muscles (pair of the latissimus dorsi, erector spinae, rectus abdominis, external oblique, and internal oblique) with 1000 Hz sampling rate. The OptiTrack optical motion capture system (NaturalPoint, Corvallis, OR, USA) with 24 Flex 3 infrared cameras was used to monitor whole body kinematics with 100 Hz sampling rate. A Bertec 4060A force plate (Bertec, Worthington, OH, USA) was used to measure ground reaction forces with 1000 Hz sampling rate. Customized Laboratory software via a National Instruments USB-6225 data acquisition board (National Instruments, Austin, TX, USA) was utilized to collect all signals simultaneously and efficiently run the model. Subjects performed complex lifting tasks by various load weight (9.1kg and 15.9kg), load origins (counterclockwise 90⁰, counterclockwise 45⁰, 0⁰, clockwise 45⁰, and clockwise 90⁰), and load height (mid-calf, mid-thigh, and shoulder). Both curved muscle model and straight-line muscle model were tested under same experiment conditions, respectively. The curved muscle model showed better model fidelity (average coefficient of determination (R2) = 0.83; average absolute error (AAE) = 14.4%) than the straight-line muscle model (R2 = 0.79; AAE = 20.7%), especially in upper levels of the lumbar spine. The curved muscle model showed higher R2 than the straight-line muscle model, and the T12/L1 level showed the biggest difference as 0.1. The curved muscle model had lower AAE than the straight-line muscle model, and the T12/L1 showed the biggest difference as 18%. The curved muscle model generally showed higher compression (up to 640N at T12/L1), lower anterior-posterior shear loads (up to 575N at T12/L1), and lower lateral shear loads (up to 521N at T12/L1) than the straight-line muscle model. The biggest difference in spinal loads between two models (especially in anterior-posterior shear and lateral shear loads) occurred at upper levels of the lumbar spine, which could be related to the amount of muscle curvatures at each spine level. The curved muscle model generally showed higher compression and lower anterior-posterior and lateral shear loads than the straight-line muscle model. It might be partially related to the muscle paths of the erector spinae (major power producing muscle). In curved muscle model, erector spinae was placed more parallel with the lumbar spine curvature than the straight-line muscle model. It could affect the spinal load distributions such as higher compression and lower shears loads in the curved muscle model compared to the straight-line muscle model. In conclusion, the improved performance of the curved muscle model indicated that the curved muscle approach would be advantageous to estimate precise spinal loads in complex lifting jobs compared to the straight-line muscle approach.
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Menéndez Arán, David H., and Spyros A. Kinnas. "On Fully Aligned Lifting Line Model for Propellers: An Assessment of Betz condition." Journal of Ship Research 58, no. 03 (September 1, 2014): 130–45. http://dx.doi.org/10.5957/jsr.2014.58.3.130.
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We discuss the optimum propeller loading through the use of a lifting line model. Viscous terms are included through a drag-to-lift ratio, and a hub image model is implemented. Two types of trailing wake geometries are considered: one based on helical wakes, which are aligned at the blade (using the so-called "moderately loaded propeller" assumption), and a second one based on a full wake alignment model to represent more accurately the wake geometry and its effect on the efficiency of the propeller. A comparison of the efficiencies and the loading distributions obtained through both methods is presented as well as convergence and numerical accuracy studies. The accuracy of Betz condition according to both wake models is tested, and conclusions are drawn based on these results.
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Gur, O., and A. Rosen. "Comparison between blade-element models of propellers." Aeronautical Journal 112, no. 1138 (December 2008): 689–704. http://dx.doi.org/10.1017/s0001924000002669.
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Abstract Blade-element models are the most common models for the analysis of propeller aerodynamics, performance calculations and propeller design. In spite of their simplicity these models are very efficient and accurate. Blade-element models use the local induced velocities as an input thus they should be combined with another model in order to calculate these induced velocities. Various models are used for the calculation of the induced velocity, where the most popular ones include: momentum, simplified-momentum, lifting-line (prescribed and free wake), and vortex (McCormick and Theodorsen) models. The paper describes the various models, compares their results and discusses the advantages and disadvantages of each one. The results indicate that the Bladeelement/simplified-momentum model offers very good accuracy together with high efficiency. For propeller performance calculations during steady axial flight, where most of the cross-sections do not experience stall, detailed and complicated models for calculating the induced velocities do not show advantages over the simple bladeelement/simplified-momentum model,
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Sutrisno, Sutrisno, Deendarlianto Deendarlianto, Indarto Indarto, Sigit Iswahyudi, Muhammad Agung Bramantya, and Setyawan Bekti Wibowo. "Performances and Stall Delays of Three Dimensional Wind Turbine Blade Plate-Models with Helicopter-Like Propeller Blade Tips." Modern Applied Science 11, no. 10 (September 30, 2017): 189. http://dx.doi.org/10.5539/mas.v11n10p189.
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The research on three dimensional (3-D) wind turbine blades has been introduced (Sutrisno, Prajitno, Purnomo, & B.W. Setyawan, 2016). In the current experiment, the 3-D wind turbine blades would be fitted with helicopter-like blade tips and additional fins to the blade hubs to demonstrate some laminarizing features. It was found that additional helicopter-like blade tip to the turbine blade creates strong laminar flows over the surface of the blade tips. Supplementary, finned hub, fitted to the blade body, creates rolled-up vortex flows, weakens the blade stall growth development, especially for blades at high-speed wind. A proposed mathematical form of modified lifting line model has been developed to pursue further 3-d blade development study of 3-d wind turbine blade. Rolled up vortex effects, developed by finned of the base hub, has been acknowledged could demolish the turbulent region, as well as laminarize the stall domain to intensify the induced wind turbine blade lift.
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Hwang, Jaejin, Gregory G. Knapik, Jonathan S. Dufour, and William S. Marras. "A Biologically-Assisted Curved Muscle Model of the Lumbar Spine." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 60, no. 1 (September 2016): 1119. http://dx.doi.org/10.1177/1541931213601262.
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Biomechanically-assisted models have been developed to estimate spine tissue loads in vivo and used to assess the potential risk of injuries in workers. However, most biomechanical models represented trunk muscles as straight-lines vectors acting between a muscle origin and insertion. Even though straight-line muscles behaved reasonably well in simple dynamic occupational tasks, this assumption could be problematic in complex multidimensional dynamic tasks that include highly asymmetric or extreme bending postures. Previous efforts at developing curved muscle models were not empirically validated or tested under dynamic loading conditions. Hence, the accuracy of spine tissue load estimations of such models has not been well documented. In this study, a curved muscle representation was developed and validated to overcome this concern. The objective of this study was to investigate the model fidelity of a biologically-assisted curved muscle model during complex dynamic lifting tasks. Twelve subjects (7 males and 5 females) participated in this study. Subjects performed dynamic lifting tasks as a function of load weight, load origin, and load height to simulate complex lifting activities from extreme and highly dynamic postures. The moment matching measures were calculated to evaluate how well model estimated the spinal moment of L5/S1 compared to measured spinal moments in terms of correlation (R2) and average absolute error (AAE). The model demonstrated good repeatability and very good model fidelity between various experimental conditions. The mean and standard deviations of multi-planar R2 were 0.85 (0.07), with 78% of all trials (411/528) having R2 > 0.8. For the multi-planar normalized AAE (%), mean and standard deviations were 12.1% (3.9), with 80% of all trials (425/528) having AAE < 15%. The results of this study indicated that curved muscle representation in the biologically-assisted model was an empirically reasonable approach to estimate accurate spine tissue loads of the lumbar spine during complex occupational circumstances.
Dissertations / Theses on the topic "Lifting line models"
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Neumann, Sönke [Verfasser], and Norbert [Akademischer Betreuer] Hoffmann. "Fluid-structure interaction of flexible lifting bodies with multi-body dynamics of order-reduced models and the actuator-line method / Sönke Neumann. Betreuer: Norbert Hoffmann." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2016. http://d-nb.info/1091059357/34.
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Montgomery, Zachary S. "A Propeller Model Based on a Modern Numerical Lifting-Line Algorithm with an IterativeSemi-Free Wake Solver." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7001.
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A fundamental aerodynamic analysis technique for a single straight fixed wing has been expounded upon and turned into a modern technique that can analyze multiple wings of more realistic shapes common on aircraft. This modern technique is extended further to apply towards propellers. A method to overcome propeller analysis problems at low airspeeds is presented. This method is compared to more traditional propeller analysis techniques.
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Cilliers, M. E. "Investigation of an aeroelastic model for a generic wing structure." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80317.
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Thesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Computational Aeroelasticity is a complex research field which combines structural and aerodynamic analyses to describe a vehicle in flight. This thesis investigates the feasibility of including such an analysis in the development of control systems for unmanned aerial vehicles within the Electronic Systems Laboratory at the Department of Electrical and Electronic Engineering at Stellenbosch University. This is done through the development of a structural analysis algorithm using the Finite Element Method, an aerodynamic algorithm for Prandtl’s Lifting Line Theory and experimental work. The experimental work was conducted at the Low-Speed Wind Tunnel at the Department of Mechanical and Mechatronic Engineering. The structural algorithm was applied to 20-noded hexahedral elements in a winglike structure. The wing was modelled as a cantilever beam, with a fixed and a free end. Natural frequencies and deflections were verified with the experimental model and commercial software. The aerodynamic algorithm was applied to a Clark-Y airfoil with a chord of 0:1m and a half-span of 0:5m. This profile was also used on the experimental model. Experimental data was captured using single axis accelerometers. All postprocessing of data is also discussed in this thesis. Results show good correlation between the structural algorithm and experimental data.
AFRIKAANSE OPSOMMING: Numeriese Aeroelastisiteit is ’n komplekse navorsingsveld waar ’n vlieënde voertuig deur ’n strukturele en ’n aerodinamiese analise beskryf word. Hierdie tesis ondersoek die toepaslikheid van hierdie tipe analise in die ontwerp van beheerstelsels vir onbemande voertuie binne die ESL groep van die Departement Elektriese en Elektroniese Ingenieurswese by Stellenbosch Universiteit. Die ondersoek bevat die ontwikkeling van ’n strukturele algoritme met die gebruik van die Eindige Element Methode, ’n aerodinamiese algoritme vir Prandtl se Heflynteorie en eksperimentele werk. Die eksperimentele werk is by die Department Meganiese en Megatroniese Ingensierswese toegepas in die Lae-Spoed Windtonnel. Die strukturele algoritme maak gebruik van ’n 20-nodus heksahedrale element om ’n vlerk-tipe struktuur op te bou. Die vlerk is vereenvouding na ’n kantelbalk met ’n vasgeklemde en ’n vrye ent. Natuurlike frekwensies en defleksies is met die eksperimentele werk en kommersiële sagteware geverifieer. Die aerodinamiese algoritme is op ’n Clark-Y profiel met 0:1m koord lengte en ’n halwe vlerk length van 0:5m geïmplementeer. Die profiel is ook in die eksperimentele model gebruik. Die eksperimentele data is met eendimensionele versnellingsmeters opgeneem. Al die verdere berekeninge wat op ekperimentele data gedoen is, word in die tesis beskryf. Resultate toon goeie korrelasie tussen die strukturele algoritme en die eksperimentele data.
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Fluck, Manuel. "Stochastic methods for unsteady aerodynamic analysis of wings and wind turbine blades." Thesis, 2017. http://hdl.handle.net/1828/7981.
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Advancing towards `better' wind turbine designs engineers face two central challenges: first, current aerodynamic models (based on Blade Element Momentum theory) are inherently limited to comparatively simple designs of flat rotors with straight blades. However, such designs present only a subset of possible designs. Better concepts could be coning rotors, swept or kinked blades, or blade tip modifications. To be able to extend future turbine optimization to these new concepts a different kind of aerodynamic model is needed. Second, it is difficult to include long term loads (life time extreme and fatigue loads) directly into the wind turbine design optimization. This is because with current methods the assessment of long term loads is computationally very expensive -- often too expensive for optimization. This denies the optimizer the possibility to fully explore the effects of design changes on important life time loads, and one might settle with a sub-optimal design.
In this dissertation we present work addressing these two challenges, looking at wing aerodynamics in general and focusing on wind turbine loads in particular. We adopt a Lagrangian vortex model to analyze bird wings. Equipped with distinct tip feathers, these wings present very complex lifting surfaces with winglets, stacked in sweep and dihedral. Very good agreement between experimental and numerical results is found, and thus we confirm that a vortex model is actually capable of analyzing complex new wing and rotor blade geometries.
Next stochastic methods are derived to deal with the time and space coupled unsteady aerodynamic equations. In contrast to deterministic models, which repeatedly analyze the loads for different input samples to eventually estimate life time load statistics, the new stochastic models provide a continuous process to assess life time loads in a stochastic context -- starting from a stochastic wind field input through to a stochastic solution for the load output. Hence, these new models allow obtaining life time loads much faster than from the deterministic approach, which will eventually make life time loads accessible to a future stochastic wind turbine optimization algorithm. While common stochastic techniques are concerned with random parameters or boundary conditions (constant in time), a stochastic treatment of turbulent wind inflow requires a technique capable to handle a random field. The step from a random parameter to a random field is not trivial, and hence the new stochastic methods are introduced in three stages.
First the bird wing model from above is simplified to a one element wing/ blade model, and the previously deterministic solution is substituted with a stochastic solution for a one-point wind speed time series (a random process).
Second, the wind inflow is extended to an $n$-point correlated random wind field and the aerodynamic model is extended accordingly. To complete this step a new kind of wind model is introduced, requiring significantly fewer random variables than previous models.
Finally, the stochastic method is applied to wind turbine aerodynamics (for now based on Blade Element Momentum theory) to analyze rotor thrust, torque, and power.
Throughout all these steps the stochastic results are compared to result statistics obtained via Monte Carlo analysis from unsteady reference models solved in the conventional deterministic framework. Thus it is verified that the stochastic results actually reproduce the deterministic benchmark. Moreover, a considerable speed-up of the calculations is found (for example by a factor 20 for calculating blade thrust load probability distributions).
Results from this research provide a means to much more quickly analyze life time loads and an aerodynamic model to be used a new wind turbine optimization framework, capable of analyzing new geometries, and actually optimizing wind turbine blades with life time loads in mind. However, to limit the scope of this work, we only present the aerodynamic models here and will not proceed to turbine optimization itself, which is left for future work.Graduate
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mfluck@uvic.ca
Book chapters on the topic "Lifting line models"
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Ghiselli, Andrea. "Conclusion." In Protecting China's Interests Overseas, 241–52. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198867395.003.0009.
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The perception that other states are more centralized and better organized than they actually are, as Robert Jervis (1976, 319–42) pointed out in his classic Perception and Misperception in International Politics, is a common phenomenon in international relations. Today, one of the most widely shared myths about China is how its political model is unique because it has succeeded in completing large-scale projects, from building the longest bridge in the world to lifting hundreds of millions of people out of poverty, in a quick and effective way. Dazzled by those achievements, regardless of their actual success, both supporters and detractors often take them as evidence of China’s capacity to play the long game, to work out and execute complex strategies. After all, when so much time has been spent, so many sacrifices made, so many resources consumed, there must be a plan. Every headline, every announcement, every statement about the next big project reinforces this myth. Myths like this appear useful and are easily accepted because they help us to simplify reality and justify our actions. They conveniently spare us having to look at what lies beneath the surface. This is why they are created and why they are dangerous when they are used as foundations for political arguments at times of growing tensions in international affairs....
Conference papers on the topic "Lifting line models"
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Pelegrineli, Luis, Ricardo Afonso Angélico, and Felipe Liorbano. "Application of Galerkin method to the solution of aerodynamic models based on the lifting-line theory." In 24th ABCM International Congress of Mechanical Engineering. ABCM, 2017. http://dx.doi.org/10.26678/abcm.cobem2017.cob17-2863.
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Kinnas, Spyros A., Wei Xu, and Yi-Hsiang Yu. "Computational Models for Prediction of Performance and Design of Tidal Turbines." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20411.
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In this paper, the performance of a horizontal axis, 3-blade tidal turbine is predicted by a vortex lattice method, in which the fully unsteady wake alignment is utilized to model the trailing wake geometry. A blade design procedure, which combines a lifting line approach with the vortex lattice analysis method and a nonlinear optimization scheme, is proposed.
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Baltazar, J., J. Machado, and J. A. C. Falca˜o de Campos. "Hydrodynamic Design and Analysis of Horizontal Axis Marine Current Turbines With Lifting Line and Panel Methods." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49377.
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This paper presents the computational models used by the authors at MARETEC/IST for hydrodynamic design and analysis of horizontal axis marine current turbines. The models combine a lifting line method for the optimization of the turbine blade geometry and an Integral Boundary Element Method (IBEM) for the hydrodynamic analysis. The classical lifting line optimization is used to determine the optimum blade circulation distribution for maximum power extraction. Blade geometry is determined with simplified cavitation requirements and limitations due to mechanical strength. The application of the design procedure is illustrated for a two-bladed 300 kW marine current turbine with a diameter of 11 meters. The effects of design tip-speed-ratio and the influence of blade section foils on power and cavitation inception are discussed. A more complete analysis may be carried out with an IBEM in steady and unsteady flow conditions. The IBEM has been extended to include wake alignment. The results are compared with experimental performance data available in the literature.
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Balduzzi, Francesco, Alessandro Bianchini, Giovanni Ferrara, David Marten, George Pechlivanoglou, Christian Navid Nayeri, Christian Oliver Paschereit, Jernej Drofelnik, Michele Sergio Campobasso, and Lorenzo Ferrari. "Three-Dimensional Aerodynamic Analysis of a Darrieus Wind Turbine Blade Using Computational Fluid Dynamics and Lifting Line Theory." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64701.
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Due to the rapid progress in high-performance computing and the availability of increasingly large computational resources, Navier-Stokes computational fluid dynamics (CFD) now offers a cost-effective, versatile and accurate means to improve the understanding of the unsteady aerodynamics of Darrieus wind turbines and deliver more efficient designs. In particular, the possibility of determining a fully resolved flow field past the blades by means of CFD offers the opportunity to both further understand the physics underlying the turbine fluid dynamics and to use this knowledge to validate lower-order models, which can have a wider diffusion in the wind energy sector, particularly for industrial use, in the light of their lower computational burden. In this context, highly spatially and temporally refined time-dependent three-dimensional Navier-Stokes simulations were carried out using more than 16,000 processor cores per simulation on an IBM BG/Q cluster in order to investigate thoroughly the three-dimensional unsteady aerodynamics of a single blade in Darrieus-like motion. Particular attention was payed to tip losses, dynamic stall, and blade/wake interaction. CFD results are compared with those obtained with an open-source code based on the Lifting Line Free Vortex Wake Model (LLFVW). At present, this approach is the most refined method among the “lower-fidelity” models and, as the wake is explicitly resolved in contrast to BEM-based methods, LLFVW analyses provide three-dimensional flow solutions. Extended comparisons between the two approaches are presented and a critical analysis is carried out to identify the benefits and drawbacks of the two approaches.
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Martín-San-Román, Raquel, José Azcona-Armendáriz, and Alvaro Cuerva-Tejero. "Lifting Line Free Wake Vortex Filament Method for the Evaluation of Floating Offshore Wind Turbines: First Step — Validation for Fixed Wind Turbines." In ASME 2019 2nd International Offshore Wind Technical Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/iowtc2019-7540.
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Abstract An in-house computational tool, called MIST, has been developed to improve the accuracy of the aerodynamic loads predictions of floating wind turbines. MIST has an aerodynamic module based on a Free Vortex filament Method (FVM) for the wake combined with a Lifting Line (LL) model for the blades. This aerodynamic model has been validated, in this first instance, for an onshore configuration against well known experimental data. Different options for the critical parameters of the code have been analyzed to get a deeper understanding of the impact of certain assumptions of this kind of models.
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Marten, David, Matthew Lennie, Georgios Pechlivanoglou, Christian Navid Nayeri, and Christian Oliver Paschereit. "Implementation, Optimization and Validation of a Nonlinear Lifting Line Free Vortex Wake Module Within the Wind Turbine Simulation Code QBlade." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43265.
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The development of the next generation of large multi-megawatt wind turbines presents exceptional challenges to the applied aerodynamic design tools. Because their operation is often outside the validated range of current state of the art momentum balance models, there is a demand for more sophisticated, but still computationally efficient simulation methods. In contrast to the Blade Element Momentum Method (BEM) the Lifting Line Theory (LLT) models the wake explicitly by a shedding of vortex rings. The wake model of freely convecting vortex rings induces a time-accurate velocity field, as opposed to the annular averaged induction that is computed from the momentum balance, with computational costs being magnitudes smaller than those of a full CFD simulation. The open source code QBlade, developed at the Berlin Institute of Technology, was recently extended with a Lifting Line - Free Vortex Wake algorithm. The main motivation for the implementation of a LLT algorithm into QBlade is to replace the unsteady BEM code AeroDyn in the coupling to FAST to achieve a more accurate representation of the unsteady aerodynamics and to gain more information on the evolving rotor wake and flow-field structure. Therefore, optimization for computational efficiency was a priority during the integration and the provisions that were taken will be presented in short. The implemented LLT algorithm is thoroughly validated against other benchmark BEM, LLT and panel method codes and experimental data from the MEXICO and NREL Phase VI tests campaigns. By integration of a validated LLT code within QBlade and its database, the setup and simulation of LLT simulations is greatly facilitated. Simulations can be run from already existing rotor models without any additional input. Example use cases envisaged for the LLT code include; providing an estimate of the error margin of lower fidelity codes i.e. unsteady BEM, or providing a baseline solution to check the soundness of higher fidelity CFD simulations or experimental results.
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Halse, Karl H., Vilmar Æsøy, Dmitriy Ponkratov, Yingguang Chu, Jiafeng Xu, and Eilif Pedersen. "Lifting Operations for Subsea Installations Using Small Construction Vessels and Active Heave Compensation Systems: A Simulation Approach." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23297.
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Sub-sea installation operations require a high level of accuracy and control in order to avoid misalignment and possible collisions between modules on the sea bed. To reduce costs, smaller and lighter construction vessels are now performing these operations. The most critical parts of the operation are lift-off from the deck, passing through the splash zone, and landing sensitive equipment on the sea bed. The hazards are: high dynamic loads, resonance effects, and slack line snap. Therefore, in this study, modeling and simulation are applied to optimize design parameters and develop operational procedures for each operation to reduce risk of failure. Further, the same models can be used in operator simulator training. Modeling and simulation of interactive multi body systems is a rather complex task, involving the vessel as a moving platform, lifting equipment such as cranes and winches, guiding devices, lifting cables and payload behavior in air, all while partly to fully submerged. It is a multi-physics problem involving hydrodynamics, mechanics, hydraulics, electronics, and control systems. This paper describes an approach to link the different models to simulate the operations including interactions between the sub-systems. The paper focuses on the modeling approach used to connect the various dynamic systems into the complete operating system. The work is in its initial phase, and some of the sub-systems models are not complete. The models are described in this paper and will be included in future work. Some initial operational examples are included, to show how the models work together.
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Dubosc, Matthieu, Nicolas Tantot, Philippe Beaumier, and Grégory Delattre. "A Method for Predicting Contra Rotating Propellers Off-Design Performance." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25057.
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This article presents a method for predicting contra rotating propellers individual and total performance which is fast and robust enough to be used in performance engine cycle and engine subsystems detailed design. The method is based on the use of single propeller maps and models mutual induced velocities thanks to one-dimensional theories. These velocities are responsible for interferences between propellers. This article goes through the assumptions on which stands the proposed method and shows that it is relevant compared against more complex methods such as lifting line theory and definitively provides a valuable easy-to-enforce preliminary design tool for open rotor propulsor controls sizing.
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BROUWER, H. "A lifting line model for propeller noise." In 12th Aeroacoustic Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1989. http://dx.doi.org/10.2514/6.1989-1079.
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Salay, Rick, Michalis Famelis, Julia Rubin, Alessio Di Sandro, and Marsha Chechik. "Lifting model transformations to product lines." In ICSE '14: 36th International Conference on Software Engineering. New York, NY, USA: ACM, 2014. http://dx.doi.org/10.1145/2568225.2568267.
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