Academic literature on the topic 'Wind tunnel startup'
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Journal articles on the topic "Wind tunnel startup"
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Zheng, Guoping, Dapeng Xue, Yizhou Zhuang, and Yusheng Zhu. "Study on Time Factors in the Smoke Control Process of Highway Tunnel Fires." Advances in Civil Engineering 2021 (November 30, 2021): 1–14. http://dx.doi.org/10.1155/2021/6670559.
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Fire is the most deadly risk during tunnel operation. Early rapid response and a reasonable smoke control plan are very important to evaluate tunnel fire performance. In order to study the relevant time factors for smoke management in a highway tunnel, firstly, the logical sequence and time of the fire alarm system (FAS) startup are investigated and analyzed. Then, according to the one-dimensional fluid mechanics model, the time rule of adjusting the airflow field in the tunnel from the normal operation stage to the emergency ventilation state is analyzed theoretically. Finally, the abovementioned theoretical formulas are verified through the employment of model experiments. The analysis shows that the time that passes from the start of the fire to when the exhaust fan is activated is close to 3 minutes. The time required to form a stable critical wind speed, however, is close to 7 minutes, which is longer than the 5 minutes it takes for the fire to reach its maximum temperature. Due to inertia, it takes about 0.5 to 2 minutes for the air velocity in tunnels of different lengths to drop from the traffic piston wind speed to the critical wind speed. If reverse smoke extraction is required, however, the duration is between 3 and 8 minutes. The conclusion is of guiding significance for the preparation of the emergency linkage control scheme for tunnels, as well as for the setting of initial boundary conditions for CFD fire simulations.
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Akbari, Vahid, Mohammad Naghashzadegan, Ramin Kouhikamali, Farhad Afsharpanah, and Wahiba Yaïci. "Multi-Objective Optimization of a Small Horizontal-Axis Wind Turbine Blade for Generating the Maximum Startup Torque at Low Wind Speeds." Machines 10, no. 9 (September 8, 2022): 785. http://dx.doi.org/10.3390/machines10090785.
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Generating a high startup torque is a critical factor for the application of small wind turbines in regions with low wind speed. In the present study, the blades of a small wind turbine were designed and optimized to maximize the output power and startup torque. For this purpose, the chord length and the twist angle were considered as design variables, and a multi-objective optimization study was used to assess the optimal blade geometry. The blade element momentum (BEM) technique was used to calculate the design goals and the genetic algorithm was utilized to perform the optimization. The BEM method and the optimization tools were verified with wind tunnel test results of the base turbine and Schmitz equations, respectively. The results showed that from the aerodynamic viewpoint, the blade of a small wind turbine can be divided into two sections: r/R < 0.52, which is responsible for generating the startup torque, and r/R ≥ 0.52, where most of the turbine power is generated. By increasing the chord length and twist angle (especially chord length) in the r/R < 0.52 section and following the ideal chord length and twist angle distributions in the r/R ≥ 0.52 part, a 140% rise in the startup torque of the designed blade was observed with only a 1.5% reduction in power coefficient, compared with the base blade. Thereby, the startup wind speed was reduced from 6 m/s for the base blade to 4 m/s for the designed blade, which provides greater possibilities for the operation of this turbine in areas with lower wind speeds.
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Čeheľová, Dagmara, Michal Franek, and Boris Bielek. "Atmospheric Boundary Layer Wind Tunnel of Slovak University of Technology in Bratislava." Applied Mechanics and Materials 887 (January 2019): 419–27. http://dx.doi.org/10.4028/www.scientific.net/amm.887.419.
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Aerodynamics is a relatively young scientific discipline, which started developing in the 50´s of last century. There are known several methods for calculating and measuring of the aerodynamic variables – in-situ measurements, wind tunnel measurements, CFD simulations and calculations according to national standards. Each method has its advantages and disadvantages. Nowadays a large focus is on experimental verifying the findings achieved with calculations help and CFD simulations. One of the verification possibilities are measurements in wind tunnels. The submitted paper deals with construction and using of the wind tunnel by the Slovak University of Technology in Bratislava. This device was put into operation after experimental verification in 2012, so this wind tunnel is one of the newest of its kind in Europe. The concept of the construction of individual structural elements and the wind tunnel parts has been designed in collaboration with the Aeronautical Research and Test Institute (Czech Republic) and was based on previous made analysis of aerodynamic tunnels. Its structure was designed and realized by Konštrukta Industry (Slovak Republic). We could it characterized as atmospheric boundary layer wind tunnel with open test section. It is unique with two test sections – front and back measuring space, where the front measuring space is used for uniform flow and the back measuring space is used for turbulent flow. That is why it is not only usable in the civil engineering sector (buildings, bridges, chimneys etc.), but also in city urbanism (pedestrian wind comfort and wind safety, dispersion of air pollutants), aircraft and automotive industries.
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Yamashita, Hiroshi, Naoshi Kuratani, Masahito Yonezawa, Toshihiro Ogawa, Hiroki Nagai, Keisuke Asai, and Shigeru Obayashi. "Wind Tunnel Testing on Start/Unstart Characteristics of Finite Supersonic Biplane Wing." International Journal of Aerospace Engineering 2013 (2013): 1–10. http://dx.doi.org/10.1155/2013/231434.
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This study describes the start/unstart characteristics of a finite and rectangular supersonic biplane wing. Two wing models were tested in wind tunnels with aspect ratios of 0.75 (model A) and 2.5 (model B). The models were composed of a Busemann biplane section. The tests were carried out using supersonic and transonic wind tunnels over a Mach number range of0.3≤M∞≤2.3with angles of attack of 0°, 2°, and 4°. The Schlieren system was used to observe the flow characteristics around the models. The experimental results showed that these models had start/unstart characteristics that differed from those of the Busemann biplane (two dimensional) owing to three-dimensional effects. Models A and B started at lower Mach numbers than the Busemann biplane. The characteristics also varied with aspect ratio: model A (1.3<M∞<1.5) started at a lower Mach number than model B (1.6<M∞<1.8) owing to the lower aspect ratio. Model B was located in the double solution domain for the start/unstart characteristics atM∞=1.7, and model B was in either the start or unstart state atM∞=1.7. Once the state was determined, either state was stable.
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Bai, Ling, and Ke Liu. "Research on Vortex-Induced Vibration Behavior of Steel Arch Bridge Hanger." Applied Mechanics and Materials 137 (October 2011): 429–34. http://dx.doi.org/10.4028/www.scientific.net/amm.137.429.
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A fluid-structure interaction numerical simulation technique based on CFD has been developed to study the vortex-induced vibration behavior of steel arch bridge hanger. Above all, wind acting on bridge hanger is simulated by using Flunet and then vortex-induced dynamic motion of hanger is solved by method in the User Defined Function (UDF). Finally hanger’s transient vibration in wind is achieved by dynamic mesh method provided by Fluent. Using this technique, the vortex-induced vibration behavior of hanger of the Nanjing Dashengguan Yangtze River Bridge is analyzed, including vibration amplitude, vibration-started wind speed and vortex shedding frequency. The study also considers influences of different section type (rectangle, chamfered rectangle and H) of hanger. The following conclusions are obtained. Firstly hanger of different section has different vibration behavior. Secondly vibration-started wind speed of different section hanger differs with each other. Thirdly relation between vibration amplitude and incoming wind speed varies obviously. At the same time, numerical results are compared with those of one wind tunnel test and the out coming is satisfied. Relation between vibration amplitude and wind speed in both numerical simulation and wind tunnel test is similar because vibration-started wind speed in numerical result has only 10% discrepancy with that in wind tunnel test while vibration amplitude’s discrepancy is only 15%. Consequently, analysis results show the reliability of this numerical simulation technique.
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Logunov, Boris A., and Ilya A. Kharin. "Improving the Efficiency of Testing Aircraft Models for Flutter Using Measurement and Information Systems in a Subsonic Wind Tunnel." Vestnik MEI, no. 5 (2021): 103–7. http://dx.doi.org/10.24160/1993-6982-2021-5-103-107.
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The technology of testing dynamically and structurally similar aircraft models for flutter in subsonic wind tunnels using information and measurement systems (IMS) is based on collection and processing of experimental data obtained in subcritical modes. The data received feature a significant scatter, in view of which the critical flutter speed is determined with acceptable accuracy only after its statistical post-processing. In view of the need to study a number of model versions during the flutter tests, the technology involved significant time spent for wind tunnel air flow startups and for processing of experimental data. To decrease the above-mentioned time expenditures, a more efficient technology was developed, using which it becomes possible, owing to a more sophisticated IMS structure, to quickly determine the critical flutter speed with acceptable accuracy directly in the course of tests. The essence of the new technology is that it eliminates interference that occurs in the existing system by introducing data transmission equipment into the IMS structure via a wireless Wi-Fi network. In view of this feature, it becomes possible to do the following in the course of testing the model for flutter in subcritical modes: to record the model time response to the impulse force, perform its spectral analysis, and plot the amplitude spectrum. The plotted amplitude spectrum is then used to measure the fundamental harmonic component, calculate and plot the functional dependence of the quantity inverse to the amplitude of the model oscillations fundamental tone on the flow velocity using approximation and extrapolation methods. The critical flutter speed is determined with acceptable accuracy when the functional dependence graph crosses zero. It is shown that the use of the proposed technology in flutter tests makes it possible to shorten the time taken to start the wind tunnel by a factor of 5 and the time taken to process the experimental data by a factor of 6, with the resulting error not exceeding 5%. It is recommended to use the technology in the Central Aerohydrodynamic Institute's subsonic wind tunnels in performing aircraft models flutter tests.
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Wiriadidjaja, Surjatin, Azmin Shakrine Mohd Rafie, Faizal Mustapha, Fadilah Hasim, Tabrej Khan, and Harijono Djojodihardjo. "Basic Geometries of the New Closed Circuit Wind Tunnel of the Universiti Putra Malaysia (UPM)." Applied Mechanics and Materials 629 (October 2014): 376–81. http://dx.doi.org/10.4028/www.scientific.net/amm.629.376.
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The existing UPM low speed wind tunnel was usually occupied by students, who carried out their final year projects or postgraduate researches, so that there was hardly free time slot for any additional testing work. Due to this reason, a new wind tunnel project has been started recently. Some basic specifications of the new tunnel have been pre-selected before the project was started, which comprised the following design decisions: a tunnel speed of 50 m/s, a test section area of 1´1 m2, and a closed circuit tunnel type. It wouldn’t be difficult to perceive that this pre-selection was made based on some of the trade-off results among the project’s options and constraints. This paper is aimed to present a simple analysis on the design of the new tunnel, focusing only on its basic geometries. Some design decisions that have been made related to its basic geometries are analyzed and reported in this paper. This analysis may be considered as a design verification of the new tunnel or even perhaps be regarded as scientific justification for its existence.
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Hong, B. G., B. R. Kang, J. C. Choi, and P. Y. Oh. "Characteristics of a plasma wind tunnel for the development of thermal protection materials." Aeronautical Journal 121, no. 1240 (May 30, 2017): 821–34. http://dx.doi.org/10.1017/aer.2017.35.
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ABSTRACTThermal plasma wind tunnels with power of 0.4 MW and 2.4 MW have been constructed at Chonbuk National University (CBNU) in Korea. This facility is capable of producing a heat flux greater than 10 MW/m2, a level that is relevant for testing thermal protection materials that are used for re-entry vehicles in space transportation. A segmented arc plasma torch was adopted as a plasma source; this was designed to have high thermal efficiency and long life, and to produce a supersonic plasma flow with enthalpy greater than 10 MJ/kg. We investigated the characteristics of the supersonic plasma flow using intrusive and non-intrusive diagnostic systems. Ablation characteristics of potential thermal protection materials such as carbon/carbon composites and graphite were investigated with the plasma wind tunnel. Cracks and pores in the materials accelerated the erosion. For carbon/carbon composites, the pores grew and the cracks which occurred at the interfaces between the carbon fibres and the matrix propagated, while for the graphite, the erosion started at the pores and peeled off the surface.
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Suryanarayana, G. K., and S. R. Bhoi. "Prediction of total pressure characteristics in the settling chamber of a supersonic blowdown wind tunnel." Aeronautical Journal 115, no. 1171 (September 2011): 557–66. http://dx.doi.org/10.1017/s0001924000006199.
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Abstract Occurrence of transient starting and stopping loads during tests at high Mach numbers is one of the major problems in intermittent blowdown wind tunnels. It is believed that in order to overcome this problem, the wind tunnel could be started at a low Mach number and low stagnation pressure; the desired high Mach number condition could be reached by continuously changing the nozzle contour while synchronously increasing the stagnation pressure. After completing the tests, the nozzle could be brought back to the initial low Mach number accompanied by synchronous decrease in the stagnation pressure. In such a scenario, it is important to ensure that the pressure regulating valve (PRV) of the wind tunnel delivers and maintains a specified minimum stagnation pressure at any Mach number, so that supersonic breakdown of the test section flow does not occur. In this paper, the problem is formulated based on quasi-steady one-dimensional isentropic equations and numerically solved to predict the time histories of settling chamber pressure and storage tank pressure for a given trajectory of the opening of the PRV, as the Mach number is changed from Mach 1 to 4·0 continuously in four seconds and vice versa. The effects of rate of change of PRV open area and rate of change of Mach number on the stagnation pressure characteristics in the settling chamber and storage tank are predicted. The measured trajectories of the PRV in experiments in the NAL 0·6m transonic wind tunnel are used as input to the prediction program to validate the methodology. Predictions indicate that when the nozzle throat is changed from Mach 1 to 4 in four seconds, the settling chamber stagnation pressure rapidly builds up and approaches the pressure in the storage tank. Predictions show an alarming rise in free stream dynamic pressure during transition from Mach 1 to 4 and vice versa, which needs to be verified through measurements.
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Truong, Takara E., Nathaniel G. Luttmer, Ebsa R. Eshete, Alia B. M. Zaki, Derek D. Greer, Tren J. Hirschi, Benjamin R. Stewart, Cherry A. Gregory, and Mark A. Minor. "Evaluating the Effect of Multi-Sensory Stimulation on Startle Response Using the Virtual Reality Locomotion Interface MS.TPAWT." Virtual Worlds 1, no. 1 (September 9, 2022): 62–81. http://dx.doi.org/10.3390/virtualworlds1010005.
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The purpose of the study was to understand how various aspects of virtual reality and extended reality, specifically, environmental displays (e.g., wind, heat, smell, and moisture), audio, and graphics, can be exploited to cause a good startle, or to prevent them. The TreadPort Active Wind Tunnel (TPAWT) was modified to include several haptic environmental displays: heat, wind, olfactory, and mist, resulting in the Multi-Sensory TreadPort Active Wind Tunnel (MS.TPAWT). In total, 120 participants played a VR game that contained three startling situations. Audio and environmental effects were varied in a two-way analysis of variance (ANOVA) study. Muscle activity levels of their orbicularis oculi, sternocleidomastoid, and trapezius were measured using electromyography (EMG). Participants then answered surveys on their perceived levels of startle for each situation. We show that adjusting audio and environmental levels can alter participants physiological and psychological response to the virtual world. Notably, audio is key for eliciting stronger responses and perceptions of the startling experiences, but environmental displays can be used to either amplify those responses or to diminish them. The results also highlight that traditional eye muscle response measurements of startles may not be valid for measuring startle responses to strong environmental displays, suggesting that alternate muscle groups should be used. The study’s implications, in practice, will allow designers to control the participants response by adjusting these settings.
Dissertations / Theses on the topic "Wind tunnel startup"
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Rainbird, John. "Blockage tolerant wind tunnel testing of aerofoils at angles of incidence from 0 to 360 degrees, with respect to the self-start of vertical-axis wind turbines." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/61575.
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The need for better quality aerofoil data, extending to incidences well beyond stall, for the modelling of vertical-axis wind turbine (VAWT) start-up is established through blade element-momentum modelling. The model is used to show that differences between existing post-stall data are large enough to impact on turbine performance. The differences between the existing aerofoil data are found to result primarily from inconsistencies introduced by wind tunnel blockage and the potential flow-derived formulae used to correct for it. A blockage tolerant wind tunnel test section has been constructed and calibrated for aerofoil testing. The tunnel has two semi-permeable walls made up of an array of transverse aerofoil-shaped slats. It produces free-air equivalent data without the need for blockage corrections. The ratio of slat to open area in the permeable walls that best minimises blockage has been obtained through testing of five different-sized NACA 0015 aerofoils. In free-air, results for the five aerofoils would be identical. The open area ratio that produces the most consistent results for the five aerofoils, based on a standard deviation analysis of the results, is therefore judged to be the best. The aerofoils are tested in a solid-walled wind tunnel, and the data processed using a selection of blockage corrections. The corrections are also judged using a standard deviation analysis. The tolerant tunnel, configured with the best open area ratio, outperforms the best corrections. Comparisons are made between results from the tolerant and solid-walled tunnels for the smallest (least blocked) aerofoil, with the latter corrected for blockage. Results are equal to within experimental error. Three additional aerofoils (a symmetrical NACA 0018 and two cambered versions of it) are tested in the tunnel. Results are used in a numerical study of virtual camber effects on VAWT blades. The effect is found to be significant in turbines with large blade chord to turbine radius ratios. Assessments of Reynolds number effects between 20,000 and 300,000 and camber, for attached and detached blade flows, on forces are presented for all four profiles. A critical Reynolds number is established, above which a laminar separation bubble is able to form on the aerofoil's suction surface. Lift generation before stall improves greatly at supercritical Reynolds numbers. VAWT start-up is modelled using a blade-element momentum method and the new experimental results. A conclusion is reached on the causes of characteristic VAWT start-up behaviour. The turbines enter an idling phase and either get stuck in it due to the presence of a "dead band" of negative torque production at low tip-speed ratios, or exit it into a rapid acceleration to final highest speeds. The behaviour results from blade Reynolds number effects, specifically the large jump in aerofoil performance at the critical Reynolds number. When turbines successfully self-start, blades are able to operate in local flows with supercritical Reynolds number for a sufficient portion of their rotation to slowly accelerate through the idling phase. When they encounter a "dead band" this is not the case.
Book chapters on the topic "Wind tunnel startup"
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Manoj Prabakar, S., and T. M. Muruganandam. "Experimental Investigations of a Diffuser Start/Unstart Characteristics for Two Stream Supersonic Wind Tunnel." In 31st International Symposium on Shock Waves 2, 1119–26. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-91017-8_139.
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Kaimal, J. C., and J. J. Finnigan. "Flow Over Flat Uniform Terrain." In Atmospheric Boundary Layer Flows. Oxford University Press, 1994. http://dx.doi.org/10.1093/oso/9780195062397.003.0004.
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We start with the simplest of boundary layers, that over an infinite flat surface. Here we can assume the flow to be horizontally homogeneous. Its statistical properties are independent of horizontal position; they vary only with height and time. This assumption of horizontal homogeneity is essential in a first approach to understanding a process already complicated by such factors as the earth's rotation, diurnal and spatial variations in surface heating, changing weather conditions, and the coexistence of convective and shear-generated turbulence. It allows us to ignore partial derivatives of mean quantities along the horizontal axes (the advection terms) in the governing equations. Only ocean surfaces come close to the idealized infinite surface. Over land we settle for surfaces that are locally homogeneous, flat plains with short uniform vegetation, where the advection terms are small enough to be negligible. If, in addition to horizontal homogeneity, we can assume stationarity, that the statistical properties of the flow do not change with time, the time derivatives in the governing equations vanish as well. This condition cannot be realized in its strict sense because of the long-term variabilities in the atmosphere. But for most applications we can treat the process as a sequence of steady states. The major simplification it permits is the introduction of time averages that represent the properties of the process and not those of the averaging time. These two conditions clear the way for us to apply fluid dynamical theories and empirical laws developed from wind tunnel studies to the atmosphere's boundary layer. We can see why micrometeorologists in the 1950s and 1960s scoured the countryside for flat uniform sites. The experiments over the plains of Nebraska, Kansas, and Minnesota (USA), Kerang and Hay (Australia), and Tsimliansk (USSR) gave us the first inklings of universal behavior in boundary layer turbulence. Our concept of the atmospheric boundary layer (ABL) and its vertical extent has changed significantly over the last few decades.
Conference papers on the topic "Wind tunnel startup"
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Speck, Sebastian, Sebastian Herbst, Hyemin Kim, Franz-Georg Stein, and Mirko Hornung. "Development, Startup Operations and Tests of a Propeller Wind Tunnel Test Rig." In 33rd AIAA Applied Aerodynamics Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2015. http://dx.doi.org/10.2514/6.2015-2578.
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Bianchini, Alessandro, Lorenzo Ferrari, and Sandro Magnani. "Start-Up Behavior of a Three-Bladed H-Darrieus VAWT: Experimental and Numerical Analysis." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45882.
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Despite increasing attention paid by both the industrial and the academic worlds, an effective diffusion of Darrieus wind turbines is still hindered by productivity lower than that of classical HAWTs, mainly connected to the critical behavior of these machines during the transient phases and in particular, during the start-up transitory, which has not been investigated in depth in the past. In this paper, a numerical code for the evaluation of the transient behavior of H-Darrieus turbines is presented. The time-dependent code was based on a theoretical approach derived from the Momentum Models and completed by several sub-models for the evaluation of the main secondary and parasitic effects. The new software was validated with an extended experimental campaign in a wind tunnel on a three-bladed H-Darrieus turbine, obtaining constant agreement with experimental data. A sensitivity analysis was then performed in order to investigate the start-up behavior of a generic small size three-bladed H-Darrieus rotor. In particular, for a fixed turbine layout, the influence of the airfoil type and the blade shape on the startup capabilities of the rotor was investigated as a function of the initial position of the rotor and the oncoming wind velocity.
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Bianchini, Alessandro, Francesco Balduzzi, John M. Rainbird, Joaquim Peiro, J. Michael R. Graham, Giovanni Ferrara, and Lorenzo Ferrari. "An Experimental and Numerical Assessment of Airfoil Polars for Use in Darrieus Wind Turbines: Part 2 — Post-Stall Data Extrapolation Methods." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42285.
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Accurate post-stall airfoil data extending to a full range of incidences between −180° to +180° is important to the analysis of Darrieus vertical-axis wind turbines (VAWTs) since the blades experience a wide range of angles of attack, particularly at the low tip-speed ratios encountered during startup. Due to the scarcity of existing data extending much past stall, and the difficulties associated with obtaining post-stall data by experimental or numerical means, wide use is made of simple models of post-stall lift and drag coefficients in wind turbine modeling (through, for example, BEM codes). Most of these models assume post-stall performance to be virtually independent of profile shape. In this study, wind tunnel tests were carried out on a standard NACA0018 airfoil and a NACA 0018 conformally transformed to mimic the “virtual camber” effect imparted on a blade in a VAWT with a chord-to-radius ratio c/R of 0.25. Unsteady CFD results were taken for the same airfoils both at stationary angles of attack and at angles of attack resulting from a slow VAWT-like motion in an oncoming flow, the latter to better replicate the transient conditions experienced by VAWT blades. Excellent agreement was obtained between the wind tunnel tests and the CFD computations for both the symmetrical and cambered airfoils. Results for both airfoils also compare favorably to earlier studies of similar profiles. Finally, the suitability of different models for post-stall airfoil performance extrapolation, including those of Viterna-Corrigan, Montgomerie and Kirke, was analyzed and discussed.
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Ahmed, Mohammed Rafiuddin, and Epeli Nabolaniwaqa. "Performance Improvement of a Wind Turbine Blade Designed for Low Wind Speeds With a Passive Trailing Edge Flap." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88417.
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The flow characteristics and the lift and drag behavior of a newly designed thick trailing-edged airfoil that was provided with fixed trailing edge flaps (Gurney flaps) of 1% to 5% height right at the back of the airfoil were studied at different low Reynolds numbers (Re) and angles of attack for possible applications in wind turbines suitable for the wind speeds of 4–6 m/s that are common in the Pacific Island Countries. A thick trailing-edged blade section, AF300, that was designed and tested in a recent work for small horizontal axis wind turbines to improve the turbine’s startup and performance at low wind speeds was chosen for this study. Experiments were performed on the AF300 airfoil in a wind tunnel at different Re, flap heights and angles of attack. Pressure distributions were obtained across the surface of the airfoil and the lift and drag forces were measured for different cases. It was found that the flap considerably improves the suction on the upper surface of the airfoil resulting in a high lift coefficient. For some of the angles, in the case of 3 mm and 4 mm flaps, the peak Cp values on the suction surface were significantly higher compared to those without the flap. However, at angles of attack of 12° and above, this unusually high Cp on the upper surface close to the leading edge caused flow separation for some cases as the flow could not withstand the strong adverse pressure gradient. The CFX results matched most of the experimental results without flaps, except that the suction peak was lower numerically. The difference was higher for the case with flaps. It is clear from the results that trailing-edge flaps can be used to improve the performance of small wind turbines designed for low wind speeds.
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Van Treuren, Kenneth W. "Small Horizontal Axis Wind Turbines: Current Status and Future Challenges." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57701.
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The category of small wind turbines is a rapidly growing market. The U. S., Europe (UK), and China are of particular interest and seeing the most growth. This paper examines the category of small wind starting with the variety of definitions found in the literature. Growth world-wide, with an emphasis on these major markets, is analyzed for trends and predicted development. The focus is on fixed pitch, small horizontal axis wind turbines, with a direct drive DC generator in the 1–10 kW class. To understand small wind turbines it is necessary to discuss design tools available for design. Included in this design discussion is the necessity for computational fluid dynamic models as well as experimentally testing both open rotors and wind tunnel models. In order for small wind turbines to continue to improve, better technologies are necessary. For design, wind turbines must be optimized for peak performance to include startup/cut-in speeds and other modifications. These wind turbines will rely on new and purposely designed airfoils; however, for low Reynolds number conditions actual airfoil data are needed as many of the computational tools do not accurately predict separation. Increasingly, noise is an issue, especially if these wind turbines will be sited in populated urban areas. An analysis of noise generation as well as design techniques for reducing noise is necessary for future designs. Important discussions on the technologies particular to small wind turbines should include the topics of aerodynamics and structures/materials. Future applications of small wind turbines seem bright. Small wind turbines are contributing to the concept of distributed generation and helping to reduce the carbon footprint. Urban environments are becoming more accepted for small wind turbines which lead to studies of flow fields in and around buildings. Of particular note are hybrid systems which combine wind with other energy generation systems such as solar, internal combustion engines, and diesel engines to name a few. These systems are advantageous for the homeowner, small business, cell phone towers, remote locations, and backup emergency power systems (to include lighting). Lastly, the concept of energy storage must be addressed in the context of small wind turbines, especially those turbines used in an isolated application. Permitting and government incentives are critical to the future success of these wind turbines.
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Abraham, John, Brian Plourde, Greg Mowry, and Ephraim Sparrow. "Experimental Test of Multi-Stage Vertical-Axis Turbines for Cellular Communication Applications." In ASME 2012 6th International Conference on Energy Sustainability collocated with the ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/es2012-91025.
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A multi-year research program has generated a working prototype for a vertical-axis wind turbine that is capable of powering cellular communication equipment. The turbine is designed to be affixed to already existing communication towers and thereby has a reduced cost of installation. The turbine is driven by air drag forces rather than by lift. It has a number of novel features including venting slots that are created to reduce the thrust loading on the communication tower. In addition, contoured caps are affixed to the upper and lower edges of the turbine blades to increase power production. As previously mentioned, the turbine design itself is a drag-based concept rather than the more typical lift-driven devices. The advantages of the drag-based design are: 1. lower startup wind speed, 2. slower rotation and a lessened vibrational load on the tower, 3. less sensitive to wind direction, and 4. it can be aligned with the tower. The design of the device was carried out through a combination of numerical simulation and experimentation. The simulations have evolved from preliminary two-dimensional calculations to a fully three dimensional, unsteady, computational fluid dynamic analysis. Simultaneously, the experiments have included both in-field and wind-tunnel tests of various stages of the turbine design. An outcome of the effort is a third-generation working vertical-axis wind turbine (VAWT) that is currently being evaluated with in-field tests. The results of the tests are positive and confirm the expectations that were developed during the product design phase. The turbine, which can be constructed with various rotor stages, has the capability of producing approximately 2–3 kW of power in wind-speed environments of 12–16 m/s. These power production levels are greatly in excess of that required to fully power the electronics equipment on a typical cellular communication tower. Unfortunately, subsequent tests showed that the turbine production dropped approximately sevenfold. The cause of the decrease in performance was friction in the mechanical components which coupled the rotating shaft to the support structure. This recognition reinforces the importance of low-resistance mechanical design for VAWTs. Another aspect of the turbine design is the specialized electronics which allow the electronics to adapt to local wind speeds and consequently increase the efficiency of the power production.
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Fujisono, Takashi, Hiroshi Yamashita, Atsushi Toyoda, Hiroki Nagai, Keisuke Asai, Takashi Matsuno, Hiromitsu Kawazoe, Shinkyu Jeong, and Shigeru Obayashi. "Supersonic Wind Tunnel Experiment on Aerodynamic Characteristics and Winglets Effects of the Tapered Supersonic Biplane." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-15015.
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The aerodynamic characteristics and the effects of tip plates of a tapered supersonic biplane wing during the starting process have been investigated through Experimental and Computational Fluid Dynamics (EFD/CFD). Three types of the wing model were used: without tip plate (type-N); with the tip plate which covers only the aft-half of the wing tip (type-A); with the tip plate which covers the entire wing tip (type-B). Experiment was conducted in the supersonic blowdown wind tunnel with 600 mm × 600 mm cross section located at the High-speed Wind Tunnel Facility of Institute of Space and Astronautical Science (ISAS/JAXA). The flow conditions covered from M∞ = 1.5 to 1.9 with increments of 0.1. Pressure-Sensitive Paint was applied to measure pressure distributions on the surface of the wing. CFD simulations were conducted to compare with experiments and to investigate effects of the Mach numbers in detail. The tapered biplane wing without the tip plate was found to start between M∞ = 1.8 and 1.9. The difference of the starting Mach numbers between type-N and type-A was small. On the other hand, the starting Mach number of type-B was about 0.05 higher than that of type-N.
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Plourde, B. D., J. P. Abraham, G. S. Mowry, and W. J. Minkowycz. "Wind-Tunnel Tests of Vertical-Axis Wind Turbine Blades." In ASME 2011 5th International Conference on Energy Sustainability. ASMEDC, 2011. http://dx.doi.org/10.1115/es2011-54604.
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An ongoing research project is investigating the potential of locating vertical-axis wind turbines (WT) on remote, off-grid cellular communication towers. The goal of the WT is to provide local power generation to meet the electrical needs of the tower. While vertical-axis devices are less efficient than their more traditional horizontal-axis counterparts, they provide a number of practical advantages which make them a suitable choice for the present situation. First, the direction of their axis is aligned with the existing tower and its rotation does not interfere with the tower structure. Second, vertical-axis devices are much less susceptible to the direction of wind and they do not require control-systems to ensure they are oriented correctly. Third, vertical-axis turbines have very low start-up wind speeds so that they generate power over a wide range of speeds. Fourth, since vertical-axis turbines rotate at a slower speed compared with horizontal counterparts, they impart a lessened vibration load to the tower. These facts, collectively, make the vertical-axis turbine suitable for the proposed application. The design process involved a detailed initial design of the turbine blade using computational methods. Next, a trio of designs was evaluated experimentally in a large, low-speed wind tunnel. The wind tunnel is operated by the University of Minnesota’s St. Anthony Falls Fluid Laboratory. The tunnel possesses two testing sections. The larger section was sufficient to test a full-size turbine blade. Accounting was taken of the blockage effect following the tests. The experiments were completed on (1) a solid-wing design (unvented), (2) a slotted-wing design (vented), and (3) a capped-and-slotted design (capped). Conditions spanned a wide range of wind speeds (4.5–11.5 m/s). The turbines were connected to electronics which simulated a range of electrical loads. The tested range was selected to span the expected range of resistances which will be found in practice. It was discovered that over a range of these wind speeds and electrical resistances, slots located on the wings result in a slight improvement in power generation. On the other hand, the slotted-and-capped design provided very large increases in performance (approximately 200–300% compared with the unvented version). This large improvement has justified commercialization of the product for use in powering remote, off-grid cellular communication towers.
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Corliss, James M., and H. Sprysl. "Measured Torsional Vibration Characteristics of a 100 Megawatt Wind Tunnel Drive Line." In ASME 1999 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/detc99/vib-8276.
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Abstract A new 100 MW (135,000 Hp) adjustable speed drive system has recently been installed in the NASA Langley National Transonic Facility. The 100 MW system is the largest of its kind in the world and consists of a salient pole synchronous motor powered by a 12-pulse Load Commutated Inverter variable frequency drive. During system commissioning the drive line torsional vibrations were measured with strain gages and a telemetry-based data acquisition system. The torque measurements included drive start-up and steady-state operation at speeds where the drive motor’s pulsating torques match the drive line’s torsional natural frequency. Rapid drive acceleration rates with short dwell times were effective in reducing torsional vibrations during drive starts. Measured peak torsional vibrations during steady-state operation were comparable to predicted values and large enough to produce noticeable lateral vibrations in the drive line shafting. Cyclic shaft stresses for all operating conditions were well within the fatigue limits of the drive line components. A comparison of the torque measurements to an analytical forced response model concluded that a 0.5% critical damping ratio was appropriately applied in the drive line’s torsional analysis.
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Xiao-hua, Fan, Yang Bo, and Sun Qi-zhi. "Investigation on Start-up Process of a Φ300mm Ludwieg Tube Wind Tunnel." In Proceedings of the 32nd International Symposium on Shock Waves (ISSW32 2019). Singapore: Research Publishing Services, 2019. http://dx.doi.org/10.3850/978-981-11-2730-4_0156-cd.
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