The State-of-the-Art Technology of H-Type Darrieus Wind Turbine Rotors

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Siddhant Jain ◽  
Ujjwal K. Saha
Keyword(s):  
State Of The Art ◽  
Technological Development ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Scientific Work ◽  
The State ◽  
Small Scale ◽  
Curvature Effects ◽  
Blade Vortex Interaction ◽  
Darrieus Rotor

Abstract There has been a resurgence of interest in the development of small-scale vertical-axis wind turbines (VAWTs) in the past few decades as is evident from the plethora of published scientific work. This attention may be attributed to the desperate need for cheaper, cleaner, and off-grid mechanisms for generating electric power. In such hasty scenario, VAWTs are being considered as one of the potential solution for small-scale power generation. Among the VAWTs, H-type Darrieus rotors have undergone extensive exploration. In this review work, an attempt has been made to assemble all the major areas of research done in the field of H-type Darrieus rotor development. These areas include the aerodynamic models, computational fluid dynamics (CFD) methods and turbulence models, self-starting and dynamic stalling behavior, blade-vortex interaction and wake studies, and blade designs and optimization studies, besides topics of special interest like blade curvature effects and skewed flows. Overall, the work gives a comprehensive review of the state-of-the-art technology of the H-type Darrieus rotor. Finally, recommendations have been made for each of the areas keeping in view of the technological development.

scholarly journals Investigations on the Effect of Radius Rotor in Combined Darrieus-Savonius Wind Turbine

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Kaprawi Sahim ◽  
Dyos Santoso ◽  
Dewi Puspitasari
Keyword(s):  
Wind Turbine ◽  
Wind Tunnel Test ◽  
Vertical Axis ◽  
Radius Ratio ◽  
Small Scale ◽  
Wind Speeds ◽  
Vertical Axis Wind Turbines ◽  
Savonius Wind Turbine ◽  
Darrieus Rotor ◽  
Low Wind Speeds

Renewable sources of energy, abundant in availability, are needed to be exploited with adaptable technology. For wind energy, the wind turbine is very well adapted to generate electricity. Among the different typologies, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off-grid power generation at low wind speeds. The combined Darrieus-Savonius wind turbine is intended to enhance the performance of the Darrieus rotor in low speed. In combined turbine, the Savonius buckets are always attached at the rotor shaft and the Darrieus blades are installed far from the shaft which have arm attaching to the shaft. A simple combined turbine offers two rotors on the same shaft. The combined turbine that consists of two Darrieus and Savonius blades was tested in wind tunnel test section with constant wind velocity and its performance was assessed in terms of power and torque coefficients. The study gives the effect of the radius ratio between Savonius and Darrieus rotor on the performance of the turbine. The results show that there is a significant influence on the turbine performance if the radius ratio was changed.

scholarly journals RANS and Hybrid RANS-LES Simulations of an H-Type Darrieus Vertical Axis Water Turbine

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2348 ◽  
Author(s):  
Omar Mejia ◽  
Jhon Quiñones ◽  
Santiago Laín
Keyword(s):  
Turbulence Models ◽  
Vertical Axis ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Small Scale ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Flow Phenomena ◽  
Water Turbine

Nowadays, the global energy crisis has encouraged the use of alternative sources like the energy available in the water currents of seas and rivers. The vertical axis water turbine (VAWT) is an interesting option to harness this energy due to its advantages of facile installation, maintenance and operation. However, it is known that its efficiency is lower than that of other types of turbines due to the unsteady effects present in its flow physics. This work aims to analyse through Computational Fluid Dynamics (CFD) the turbulent flow dynamics around a small scale VAWT confined in a hydrodynamic tunnel. The simulations were developed using the Unsteady Reynolds Averaged Navier Stokes (URANS), Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) turbulence models, all of them based on k-ω Shear Stress Transport (SST). The results and analysis of the simulations are presented, illustrating the influence of the tip speed ratio. The numerical results of the URANS model show a similar behaviour with respect to the experimental power curve of the turbine using a lower number of elements than those used in the DES and DDES models. Finally, with the help of both the Q-criterion and field contours it is observed that the refinements made in the mesh adaptation process for the DES and DDES models improve the identification of the scales of the vorticity structures and the flow phenomena present on the near and far wake of the turbine.

scholarly journals Continuous Ultrasonic Reactors: Design, Mechanism and Application

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 344 ◽  
Author(s):  
Zhengya Dong ◽  
Claire Delacour ◽  
Keiran Mc Carogher ◽  
Aniket Pradip Udepurkar ◽  
Simon Kuhn
Keyword(s):  
State Of The Art ◽  
Pilot Scale ◽  
Chemical Processes ◽  
The State ◽  
Small Scale ◽  
Immiscible Fluid ◽  
Flow Reactors ◽  
Design Mechanism ◽  
Ultrasonic Reactors

Ultrasonic small scale flow reactors have found increasing popularity among researchers as they serve as a very useful platform for studying and controlling ultrasound mechanisms and effects. This has led to the use of these reactors for not only research purposes, but also various applications in biological, pharmaceutical and chemical processes mostly on laboratory and, in some cases, pilot scale. This review summarizes the state of the art of ultrasonic flow reactors and provides a guideline towards their design, characterization and application. Particular examples for ultrasound enhanced multiphase processes, spanning from immiscible fluid–fluid to fluid–solid systems, are provided. To conclude, challenges such as reactor efficiency and scalability are addressed.

scholarly journals Neural Machine Translation with Joint Representation

2020 ◽  
Vol 34 (05) ◽  
pp. 8285-8292
Author(s):  
Yanyang Li ◽  
Qiang Wang ◽  
Tong Xiao ◽  
Tongran Liu ◽  
Jingbo Zhu
Keyword(s):  
Machine Translation ◽  
English Translation ◽  
Large Scale ◽  
State Of The Art ◽  
Statistical Machine Translation ◽  
The State ◽  
Small Scale ◽  
Neural Machine Translation ◽  
Joint Representation

Though early successes of Statistical Machine Translation (SMT) systems are attributed in part to the explicit modelling of the interaction between any two source and target units, e.g., alignment, the recent Neural Machine Translation (NMT) systems resort to the attention which partially encodes the interaction for efficiency. In this paper, we employ Joint Representation that fully accounts for each possible interaction. We sidestep the inefficiency issue by refining representations with the proposed efficient attention operation. The resulting Reformer models offer a new Sequence-to-Sequence modelling paradigm besides the Encoder-Decoder framework and outperform the Transformer baseline in either the small scale IWSLT14 German-English, English-German and IWSLT15 Vietnamese-English or the large scale NIST12 Chinese-English translation tasks by about 1 BLEU point. We also propose a systematic model scaling approach, allowing the Reformer model to beat the state-of-the-art Transformer in IWSLT14 German-English and NIST12 Chinese-English with about 50% fewer parameters. The code is publicly available at https://github.com/lyy1994/reformer.

Performance Evaluation of H-Type Darrieus Vertical Axis Wind Turbine with Different Turbine Solidity

2020 ◽  
Vol 17 (2) ◽  
pp. 833-839
Author(s):  
Muhamad Fadhli Ramlee ◽  
Ahmad Fazlizan ◽  
Sohif Mat
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Small Scale ◽  
Stream Velocity ◽  
Wind Condition ◽  
Vertical Axis Wind Turbine ◽  
Power Performance ◽  
Darrieus Rotor

Among renewable energy resources, wind energy is one of the best alternative for power generation. Recently, vertical axis wind turbine (VAWT) received renewed interest as small-scale wind energy converter due to its suitability for urban application, where the wind condition is known to be unsteady and turbulence. Amongst various type of VAWTs, H-type Darrieus rotor has become more popular, thanks to its simple construction features, resulting to low manufacturing and installation cost. The aim of this paper is to evaluate numerically the power performance of straight-bladed Darrieus VAWT with different turbine solidity using computational fluid dynamic (CFD) technology. A series of two-dimensional CFD simulations of a three-bladed H-type Darrieus rotor were performed with 3 different solidities, σ (0.3, 0.5 and 0.7) to evaluate their power performance. Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations were used to calculate the instantaneous moment coefficient, Cm and power coefficient, Cp over a range of tip speed ratio, λ (0.5–4.5) with a free stream velocity of 8.0 m/s. The simulation results show that high solidity turbine performed well at low values of λ while turbine with low solidity has a wider operating range of λ and performed better at λ > 3.0 due to less blade-wake interactions between upstream and downstream halves of the turbine and lower blockage effect. The findings lend substantially to our understanding of physics flow around blades and turbine in order to optimize the power performance of small scale straight-bladed Darrieus VAWT operating in unsteady and turbulence wind condition.

scholarly journals A Review of Grooved Dynamic Gas Bearings

2019 ◽  
Vol 72 (1) ◽  
Author(s):  
Lili Gu ◽  
Eliott Guenat ◽  
Jürg Schiffmann
Keyword(s):  
High Speed ◽  
State Of The Art ◽  
Integrated Design ◽  
The State ◽  
Small Scale ◽  
Second Phase ◽  
Foil Bearings ◽  
Turbulence Effects ◽  
Physical Phenomena ◽  
Gas Bearing

Abstract This paper offers an extensive review of publications dealing with the modeling, the design, and the experimental investigation of grooved dynamic gas-lubricated bearings. Recent years have witnessed a rise in small-scale and high-speed turbomachinery applications. Besides the well-known gas foil bearings, grooved bearings offer attractive advantages, which unveil their potential in particular at small scale due to the structural simplicity as well as satisfying predictability. This paper starts with a general background of the application of gas-lubricated bearings and introduces and compares the different gas bearing topologies. Further, the state-of-the-art modeling of grooved gas-lubricated bearings is introduced, systematically assessing the advantages and inconveniences of two major approaches, i.e., the narrow groove theory (NGT) and direct discretization method. Since the NGT method is an elegant and efficient approach to model the complex effects of periodic grooves, a critical section is dedicated to the NGT. In a second phase, different models to include additional physical phenomena such as real gas lubrication, rarefaction, or turbulence effects are reviewed. The paper concludes with a critical assessment of the state-of-the-art and indicates potential fields of research that would allow to shed more light into the understanding of these bearings, as well as with some thoughts on the integrated design methodologies of gas bearing supported rotors.

On combining GUI desktop GIS with computer clusters & cloud resources, the role of programming skills and the state of the art in GUI driven GIS HPC applications

2021 ◽  
Author(s):  
Sebastian M. Ernst
Keyword(s):  
Software Development ◽  
Graphics Processing Units ◽  
High Performance ◽  
State Of The Art ◽  
Scientific Work ◽  
Practical Experience ◽  
The State ◽  
Entry Barrier ◽  
Software Libraries ◽  
Cloud Resources

<p>The Free and Open Source Software (FOSS) ecosystem around Geographic Information System (GIS) is currently seeing rapid growth – similar to FOSS ecosystems in other scientific disciplines. At the same time, <span>t</span>he <span>need</span> of broad programming and software development skills appears to become a common theme for potential (scientific) users. There is a rather clear boundary between what can be done with Graphical User Interface applications such as QGIS only on the one hand side and contemporary software libraries on the other hand side – if one <span>actually has the required </span><span>skillet</span><span> to us</span><span>e the latter</span><span>. Practical experience shows that more and more types of research require far more than </span><span>just </span><span>rudimentary software development skills. </span><span>Those can be hard to </span><span>acquire</span><span> and distract from the actual scientific work at hand</span><span>. </span><span>For instance t</span><span>he installation, integration and deployment of much desired software libraries </span><span>from the field of high-performance computing (HPC) </span><span>for </span><span>e.g. g</span><span>eneral-purpose computing on graphics processing units </span><span>(GPGPU)</span> <span>or computations on clusters or cloud resources </span><span>is very often becoming an obstacle on its own. </span><span>Recent advances in packaging and deployment systems around popular programming language ecosystems such as Python enable a new kind of thinking, </span><span>however. </span><span>Desktop GUI applications can now much more easily be combined with the mentioned type of libraries, which lowers the entry barrier to HPC applications and the handling of large quantities of data drastically. This work aims at providing an overview of the state of the art in this field and showcasing possible techniques. </span></p>

Exploring the Educational Power of Serious Games

2012 ◽  
pp. 928-946
Author(s):  
Carlos Rodríguez-Hoyos ◽  
Maria João Gomes
Keyword(s):  
Research Agenda ◽  
Serious Games ◽  
State Of The Art ◽  
Scientific Work ◽  
The State ◽  
Google Scholar ◽  
Analysis And Synthesis

In this chapter, the authors present a review of the state of the art of research carried out over the last few years aimed at a deeper analysis of the educational uses of serious games. In this endeavour, they examined a sample of the scientific work generated between 2008 and 2010 from three sources: Biblioteca do Conhecimento Online, Google Scholar, and the database Edit Lib belonging to the Association for the Advancement of Computing in Education (ACCE). As a result of this process of analysis and synthesis, the authors present the main lines of research carried out in this field of work and propose a research agenda in order to improve the educational power of edutainment.

Sign in / Sign up

Export Citation Format

Share Document