scholarly journals Spatiotemporal dynamics of snow erosion, deposition and horizontal mass flux

2019 ◽  
Vol 65 (250) ◽  
pp. 249-262
Author(s):  
PHILIP CRIVELLI ◽  
ENRICO PATERNA ◽  
MICHAEL LEHNING
Keyword(s):  
Wind Tunnel ◽  
Mass Flux ◽  
Low Cost ◽  
Microsoft Kinect ◽  
Surface Mass ◽  
Wind Speeds ◽  
Particle Counting ◽  
Mass Fluxes ◽  
Power Spectral ◽  
Low Wind Speeds

ABSTRACTThe quantification of snow transport, both in wind tunnels and the field, apply particle counting methods limited to punctual sampling of relatively small volumes. Particle counting can only capture horizontal mass fluxes, failing to measure snow erosion or deposition. Herein, we present a novel low-cost sensor tool, based on a Microsoft Kinect, adapted to capture snow surface changes during snow drifting at unprecedented spatial and temporal resolutions. In the wind tunnel setting of these experiments we observe a balance between erosion and deposition at low wind speeds, while erosion is dominant at higher wind speeds. Significant differences in power spectral densities of surface mass flux and horizontal particle mass flux are observed. We show that for the saltation-length-scale parameter λ = 1, the integrated particle flux can be used to estimate the total surface mass flux in the wind tunnel. This provides an important basis to interpret mass flux measurements in the field.

scholarly journals Potential of dust emission resources using small wind tunnel and GIS: case study of Bakhtegan playa, Iran

2019 ◽  
Vol 9 (8) ◽  
Author(s):  
Siroos Karimzadeh ◽  
Mohammad Mehdi Taghizadeh
Keyword(s):  
Wind Tunnel ◽  
Present Model ◽  
Low Cost ◽  
Dust Emission ◽  
High Potential ◽  
Wind Speeds ◽  
Desert Areas ◽  
Medium Potential

Abstract Determination of the high potential of dust emission is a requisite affair in the management of dusts emission and as well as avoiding its risks. Wind tunnel is among the most important approaches in the study of areas having high potential in emitting dusts. Extensive dried playas and desert areas require the making of low-cost, simple, and car-portable tunnels capable of presenting comparable data of various areas even supposing not having enough precision in the model of real wind motion. In this study, we first engaged in making a car-portable tunnel with a primarily semicircle section of 38 cm height, 50 cm diameter, and 110 cm length. A fan and key appliance with the ability to change speed were used along with a simple transformer launched with car battery. Then, concentration of the pm10 dusts was measured in the various wind speeds of 1, 2.5, 4, 5.5, and 7 m/s by the help of anemometer and digital equipments. The study of Bakhtegan playa was done, as the methodology of handling with this tunnel, in 35 positions, and zoning of the results was performed via ArcGIS software. Depending on the destructibility of the shell by wind, the areas under study were categorized as low potential (34%), medium potential (37%), and high potential (29%) in emitting dusts. The results of zoning spotted the high-potential areas on the map. The usage of small tunnels, as in the present model, may be applied in order for the low-cost and fast studies of vast areas to the purpose of playas management.

scholarly journals Wind farm power optimization through wake steering

2019 ◽  
Vol 116 (29) ◽  
pp. 14495-14500 ◽  
Author(s):  
Michael F. Howland ◽  
Sanjiva K. Lele ◽  
John O. Dabiri
Keyword(s):  
Energy Production ◽  
Wind Farm ◽  
Low Cost ◽  
Wind Farms ◽  
Power Production ◽  
Low Carbon ◽  
Steering Control ◽  
Intergovernmental Panel ◽  
Wind Speeds ◽  
Low Wind Speeds

Global power production increasingly relies on wind farms to supply low-carbon energy. The recent Intergovernmental Panel on Climate Change (IPCC) Special Report predicted that renewable energy production must leap from 20% of the global energy mix in 2018 to 67% by 2050 to keep global temperatures from rising 1.5°C above preindustrial levels. This increase requires reliable, low-cost energy production. However, wind turbines are often placed in close proximity within wind farms due to land and transmission line constraints, which results in wind farm efficiency degradation of up to 40% for wind directions aligned with columns of turbines. To increase wind farm power production, we developed a wake steering control scheme. This approach maximizes the power of a wind farm through yaw misalignment that deflects wakes away from downstream turbines. Optimization was performed with site-specific analytic gradient ascent relying on historical operational data. The protocol was tested in an operational wind farm in Alberta, Canada, resulting in statistically significant (P<0.05) power increases of 7–13% for wind speeds near the site average and wind directions which occur during less than 10% of nocturnal operation and 28–47% for low wind speeds in the same wind directions. Wake steering also decreased the variability in the power production of the wind farm by up to 72%. Although the resulting gains in annual energy production were insignificant at this farm, these statistically significant wake steering results demonstrate the potential to increase the efficiency and predictability of power production through the reduction of wake losses.

Design and Testing of Low-Speed Wind Turbine Blade

2009 ◽  
Author(s):  
R. S. Amano ◽  
R. J. Malloy
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Pid Controller ◽  
Current Data ◽  
Potential Candidate ◽  
Efficient Energy ◽  
Wind Speeds ◽  
Tunnel Model ◽  
Low Wind Speeds ◽  
Design And Testing

There is a need for clean, cheap, and efficient energy. One potential candidate for a source of this energy is a wind energy. In order to maximize the amount of energy captured, a new, low airspeed wind turbines must be designed. A wind turbine was created using the NACA 4412 foil shape and a decreasing chord length with increasing distance from the center of the turbine. The angle of attack was also varied. The airfoil was analyzed in CFD and tested via wind tunnel model. The turbine was connected to a motor which was connected to a resistor and current and voltage meters. Using the voltage and current data at a prescribed rate of rotation, the power generated was calculated. Despite the shortcomings of the model, decent power output was generated. Since the wind tunnel could only perform up to 5 ft/s (or 3.4 mph), this shows that the turbine is acceptable for low wind speeds. For practical use the turbine would need to be scaled to a greater size and a PID controller that can generate higher resistance would need to be employed.

scholarly journals The thermodynamic requirements on atmospheric models imposed by observed stellar nonthermal mass-fluxes and by those observed nonthermal features enhanced in Xe stars

1979 ◽  
Vol 83 ◽  
pp. 215-226
Author(s):  
Richard N. Thomas
Keyword(s):  
Wind Tunnel ◽  
Mass Loss ◽  
Radiation Pressure ◽  
Mass Flux ◽  
A Priori ◽  
Stellar Atmosphere ◽  
Stellar Atmospheres ◽  
Atmospheric Models ◽  
Mass Fluxes ◽  
Hot Corona

If I understand correctly, this session of the Symposium on Mass-Loss and Evolution of O Stars aims at clarifying the merits and demerits of four “theories” for the observed, nonthermal mass-loss from these stars. Hearn has summarized what he considers to be the essential characteristics of each of the four, especially relative to a set of questions which, he considers, put the observational requirements on the “theories” in focus. Representatives of each of the “radiation-pressure initiated, radiative-equilibrium controlled”, “hot corona”, and “warm corona” alternatives have elaborated on Hearn's summary, to stress what they consider essential. So, now, I would do the same for what we caricature as the “imperfect wind-tunnel” model — not theory, which I assert does not yet exist — both for nonthermal mass-flux, and for other observed nonthermal phenomena, in stellar atmospheres generally, not just in O stars particularly. I assert, that in studying nonthermal mass-flux from O stars, if you limit your attention only to nonthermal mass-flux, and only to O stars, you handicap, a priori, your chance to understand what is required for the general model of a stellar atmosphere, in order to produce this variety of nonthermal phenomena observed, alike in all varieties of stars.

scholarly journals The Effect of Wave-damping on the Surface Velocity of Water in a Wind Tunnel

1964 ◽  
Vol 17 (2) ◽  
pp. 184 ◽  
Author(s):  
LM Fitzgerald
Keyword(s):  
Wind Tunnel ◽  
Surface Waves ◽  
Wind Velocity ◽  
Surface Pressure ◽  
Surface Velocity ◽  
Detergent Solution ◽  
Clean Water ◽  
Wind Speeds ◽  
Wavy Surfaces ◽  
Low Wind Speeds

A laboratory wind tunnel has been used to study the movement of the surface of a body of water over which a wind is blowing. The ratio of the surface velocity Us to the wind velocity V has been measured for both smooth and wavy surfaces at wind speeds between 350 and 750 cm/s. It has been found that this ratio is markedly affected by the damping-out of surface waves. For a wavy surface, as obtained with clean water, us/V has a constant value of about 0�03. The damping of the surface waves is achieved by the addition of detergent solution to the water. There is a particular concentration of detergent, and a corresponding surface pressure, at which u s/ V ceases to have this constant value and begins to rise to' values around 0�045. For a fully damped surface us/V rises linearly with V for low wind speeds and tends to a constant value of 0�045 for wind speeds greater than 550 cm/s. These findings are, to some extent, in conflict with the observations and theories of previous workers.

scholarly journals Analysis of the Behavior in the Wind Tunnel of an Experimental Model of Savonius with Interlocking Cups with the Classic Ones with 2, 3 and 4 Semi-Cylindrical Cups

2021 ◽  
Vol 44 (1) ◽  
pp. 11-18
Author(s):  
Nelu CAZACU
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Experimental Model ◽  
Experimental Models ◽  
Dead Zones ◽  
Wind Speeds ◽  
Measuring Section ◽  
Formed Channel ◽  
Low Wind Speeds ◽  
Air Passage

The paper is based on experiments conducted on the wind tunnel at low wind speeds (<9.5 m/s), on an experimental model of S-rotor wind turbine type with four blades and a D/H ratio of 1. Semi-cylindrical cups opposite 180 degrees are aerodynamically coupled by overlap and with an air passage gap to equalize the pressures. The formed channel is shaped to allow the same for pairs of blades at 90 degrees. The experimental model has an area of 0.025 m2 which represents 10% of the surface of the measuring section of the wind tunnel (0.25 m2). The behavior of the experimental model was compared with the experimental models of S-rotor with 2, 3 and 4 semi-cylindrical cups, with the same interception surface. The results confirm the better start of the experimental model by reducing dead zones and operating more evenly and stably over a longer range of wind speeds. The results confirm the validity of the proposed concept of interwoven aerodynamic coupling of semi-cylindrical cups.

scholarly journals Canard optimization for enhancing the performance of small horizontal axis wind turbine at low wind speeds

2020 ◽  
Vol 37 ◽  
pp. 63-71
Author(s):  
Yui-Chuin Shiah ◽  
Chia Hsiang Chang ◽  
Yu-Jen Chen ◽  
Ankam Vinod Kumar Reddy
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Peak Performance ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Optimum Parameters ◽  
Low Wind Speeds

ABSTRACT Generally, the environmental wind speeds in urban areas are relatively low due to clustered buildings. At low wind speeds, an aerodynamic stall occurs near the blade roots of a horizontal axis wind turbine (HAWT), leading to decay of the power coefficient. The research targets to design canards with optimal parameters for a small-scale HAWT system operated at variable rotational speeds. The design was to enhance the performance by delaying the aerodynamic stall near blade roots of the HAWT to be operated at low wind speeds. For the optimal design of canards, flow fields of the sample blades with and without canards were both simulated and compared with the experimental data. With the verification of our simulations, Taguchi analyses were performed to seek the optimum parameters of canards. This study revealed that the peak performance of the optimized canard system operated at 540 rpm might be improved by ∼35%.

scholarly journals Dependence of Power Characteristics on Savonius Rotor Segmentation

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2912
Author(s):  
Krzysztof Doerffer ◽  
Janusz Telega ◽  
Piotr Doerffer ◽  
Paulina Hercel ◽  
Andrzej Tomporowski
Keyword(s):  
High Wind ◽  
Horizontal Axis Wind Turbine ◽  
Savonius Rotor ◽  
Power Characteristics ◽  
Wind Speeds ◽  
Single Segment ◽  
High Elongation ◽  
Low Wind Speeds ◽  
Number Of Segments ◽  
Rotor Type

Savonius rotors are large and heavy because they use drag force for propulsion. This leads to a larger investment in comparison to horizontal axis wind turbine (HAWT) rotors using lift forces. A simple construction of the Savonius rotor is preferred to reduce the production effort. Therefore, it is proposed here to use single-segment rotors of high elongation. Nevertheless, this rotor type must be compared with a multi-segment rotor to prove that the simplification does not deteriorate the effectiveness. The number of segments affects the aerodynamic performance of the rotor, however, the results shown in the literature are inconsistent. The paper presents a new observation that the relation between the effectiveness of single- and multi-segment rotors depends on the wind velocity. A single-segment rotor becomes significantly more effective than a four-segment rotor at low wind speeds. At high wind speeds, the effectiveness of both rotors becomes similar.

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