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Hello,
I have measurements of wind speed from three-components ultrasonic anemometers. I need to calculate the integral length scale and power spectrum. I have used the standard procedure for this, i. e. calculate the fluctuation of the chosen component of the signal of wind speed, then the autocorrelation curve of the component , integrate the autocorrelation curve up to the first zero crossing and multiply the integral with mean wind speed. However, the mean wind speed can be negative, as the anemometer can measure wind component in both directions. Obviously, the integral of the autocorrelation curve can be only positive. Then I get negative integral length scale as a result of the negative mean wind speed. How would you solve this? Would it be correct to use the absolute value of the wind speed? Thanks for your ideas.
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Integral length scales can arise from both Eulerian and Lagrangian autocorrelation functions and both are useful and both can be negative in at least some regions. If, on average, a velocity perturbation at one point or residence time is negative when the perturbation at the initial point is positive, the perturbations are negatively correlated and the autocorrelation function is negative valued at that point/time. If this persists far/long enough, the integral of the function can become negative. This is not common but is routinely observed in flows, especially those that have coherent structures. It is common that people use exponential decay functions to approximate the autocorrelation functions, and there is some theoretical basis for this. However, complex flows have much more complex autocorrelation functions. You may be being misled by the common practice of using such functions to approximate what can be a more complex function. The exponential decay function, by the way, cannot be entirely accurate since its derivative at initial condition is not zero. Since flows have mass/momentum, their autocorrelation functions should have a zero derivative in the limit of zero distance/time from the origin.
Having said all that, I suspect there is an error in your data analysis.
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I am micro-siting wind turbines in WAsP.
I need to optimize the layout obtained after micro-siting using open-source optimization software.
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WindFarmer is proprietary and costs around 5000 Euros per year. Not Open source, nor free
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We know wind turbines extract energy from the wind in order to produce electricity, the wind downstream of a turbine has a lower energy content than the wind upstream. Suppose, the understudy region is formed of two zones (Figure attached). In the dark red zone, the initial wind velocity is greater than that in the light red zone.
Bearing in mind the different initial wind velocities, How to determine the resulting wind speed, due to the wake effect of turbine 1 on turbine 2 (case 1) and of turbine 3 on turbine 4 (case 2)?
Scenario: The problem in case 2, perhaps the recovered wind speed at turbine 4 is greater than V0 =8 m/s (initial speed at light red region)
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Dear Bassam:
At the first, and as you know that several different factors influence the potential wind resource in an area. The three main factors that influence power output are: wind speed, air density, and blade radius. Wind turbines need to be in areas with a lot of wind on a regular basis, which is more important than having occasional high winds.
# Wind speed:
Wind speed largely determines the amount of electricity generated by a turbine. Higher wind speeds generate more power because stronger winds allow the blades to rotate faster. Faster rotation translates to more mechanical power and more electrical power from the generator. The relationship between wind speed and power for a typical wind turbine is shown in Figure (a).
Turbines are designed to operate within a specific range of wind speeds. The limits of the range are known as the cut-in speed and cut-out speed. The cut-in speed is the point at which the wind turbine is able to generate power. Between the cut-in speed and the rated speed, where the maximum output is reached, the power output will increase cubically with wind speed. For example, if wind speed doubles, the power output will increase 8 times. This cubic relationship is what makes wind speed such an important factor for wind power. This cubic dependence does cut out at the rated wind speed. This leads to the relatively flat part of the curve in Figure (a), so the cubic dependence is during the speeds below 15 m/s (54 kph).
The cut-out speed is the point at which the turbine must be shut down to avoid damage to the equipment. The cut-in and cut-out speeds are related to the turbine design and size and are decided on prior to construction.
#Air Density:
Power output is related to the local air density, which is a function of altitude, pressure, and temperature. Dense air exerts more pressure on the rotors, which results in higher power output.
#Turbine Design:
Wind turbines are designed to maximize the rotor blade radius to maximize power output. Larger blades allow the turbine to capture more of the kinetic energy of the wind by moving more air through the rotors. However, larger blades require more space and higher wind speeds to operate. As a general rule, turbines are spaced out at four times the rotor diameter. This distance is necessary to avoid interference between turbines, which decreases the power output.
# There's a phenomenon, which referred to as the reduced wake effect:
During curtailment, less power is extracted from the wind and thus the wake effects are reduced. This leads to a wind speed increase at the downstream turbine and therefore to an apparent increase of its available power. This phenomenon is referred to as the reduced wake effect.
# So you could benefit from this valuable article about this topic:
"Analysis of the reduced wake effect for available wind power calculation during curtailment"
# Abstract:
With the increase of installed wind power capacity, the contribution of wind power curtailment to power balancing becomes more relevant. Determining the available power during curtailment at the wind farm level is not trivial, as curtailment changes the wake effects in a wind farm. Current best practice to estimate the available power is to sum the available power calculated by every wind turbine. However, during curtailment the changed local wind conditions at the wind turbines lead to inaccurate results at the wind farm level. This paper presents an algorithm to determine the available power of a wind farm during curtailment. Moreover, results of curtailment experiments are discussed that were performed on nearshore wind farm Westermeerwind to validate the algorithm. For the case where a single turbine is being curtailed, it is shown that the algorithm reduces the estimation error for the first downstream turbine significantly. Further development of the algorithm is required for accurate estimation of the second turbine. All further downstream turbines did not experience a change in wake conditions.
I hope it will be helpful ...
With my best regards ...
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In Serra Gaúcha of Rio Grande do Sul, Brasil, our researches have been stated several deficiences in wind flow determination, to setting up a airblast sprayer.
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We are using turbulent air jets which need low air flow whil are rotating the leaves and cover all of them on both sides agmanor@ airgreen.co.il
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Seismic design takes advantage of larger damping owing to structure ductility to reduce the design load by R factor (of 3 to 8 value). Apparently, both seismic and wind governing loads are derived from similarly rare event at about 500 years return period, although some recent codes use 2/3 of MCE 2500yrs for seismic. But why only seismic design allows some structural yielding and acceptable damage, while wind design should remain elastic? Is there some concept that I misunderstand?
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I think earthquake forces are impulsive in nature and they also act back and forth demanding ductility in the structure to prevent sudden collapse of structure. Whereas wind loads are build-up over time and not dynamic loads.
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I actually want to design a prototype system which constantly supply air to the wind turbine. Generally wind turbines are efficient in some particular windy seasons. So I thought about Artificially cause the wind to flow by concept of maintaining pressure difference in between two regions. Can it will possible to do that?
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As elaborated in a 2014 US patent for Artificial Wind Generator:
Naturally available energy such as sunlight is used to create high and low air pressure areas artificially in two separate chambers or regions. The two areas are connected together through a tube, which results in wind flow from the higher air pressure area to the lower air pressure area, which wind flow is used to power wind turbines which in turn generate electric power. An Artificial Wind Generator apparatus for generating electrical energy through the artificial initiation and maintenance of wind flow in an enclosed system wherein a natural energy source is used to create pressure differences in two chambers
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Hi, I want to get three years of hourly wind speed data at 50 meters height for specific locations in Turkey. Unfortunately, I couldn't find any good websites for this. Do you know any online sources for this?
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Ahmet Emre Onay, You can click any location and select the data type (Hourly, daily etc.), select dates, then click process, download result. this will give 10m height data, use power law or logarithmic law to convert to 50 m. Also, you can check Global wind atlas
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I want to analyze the results of a wind tunnel setup. Is there any manual with the detail of it? How does it work? Different components and the detailed analysis of results...
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Barlow, Jewel B., William H. Rae, and Alan Pope. Low-speed wind tunnel testing. John Wiley & Sons, 1999.
Regards
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For hexahedral meshing, it is quite simple to divide one edge in a particular number of division. But for tetrahedral meshing it is not that simple. If we are using a complicated domain for aerodynamic flow and if it is difficult for doing the hexahedral meshing, then how to divide the edge in element in that fashion and what thing must be kept in mind while doing the grid convergence study.
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Mr.Prasenjit, i feel for correcting your problem it is better to go with smaller size element with fine mesh. Also, your problem could be corrected with aspect ratio 1, many researchers mentioned that aspect ratio 1 would give better results with close converging with exact results. I mean to say instead of refining longer or shorter direction it is better to use length to width ratio of element is 1 for getting close results..ok all the best in your research..
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I think factors such as height above ground level, surface roughness, temperature, solar radiation, humidity, pressure, and the slope of the earth can be influential.Which factors have the most impact and which one has the least impact?
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The new study indicates that large natural climate cycles are a potential culprit.
Using models to study factors that influence global wind behavior, researchers have found that large climate patterns - which affect temperatures in certain parts of the world - have a major impact on wind speed. Temperature differences between adjacent areas, or between the ocean and adjacent land areas, can affect air flow.
You can also read this file below:
to estimate wind speed based on the environmental specifications, can also read this file below:
file:///C:/Users/dell/Downloads/atmosphere-10-00804.pdf
file:///C:/Users/dell/Downloads/applsci-09-05385-v2%20(1).pdf
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Which blades is most efficiency and often used to design wind turbine horizontal axis? Where I will find the perfil alar?
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Wind energy is used to generate environmentally friendly electrical energy with high moment forces through the wind turbine rotation. Although electric power generation is good, wind turbine noise affects the environment by creating different sound pressure levels.
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I'm looking for historical wind speed data in Vietnam for coastal areas. Data can be 10 or 2-min. averaged. The data will be used for extreme wind speed and recurrence period analysis that is why I need data for as long period of time as possible.
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You need to keep track of friends and students who are studying in Australia. They usually work on data from neighboring countries.
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While going through the ASCE 7-16, I encountered with the equation C26.11-8 under chapter 26 'Wind loads: General Requirements'.
fn1=150/h (ft) ------------- Equation (C26.11-8)
There is a reference to two papers by Zhou and Kareem. However, I couldn't quite grasp the idea on how the equation was derived and wanted to know if that equation is reliable to use?
Thank you so much for your time.
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This is an empirical equation, there is no derivation.
It is usually used by designers to estimate the wind load.
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Actually I'm trying to generate wind direction and velocity using sentinel
1 images.
But I'm having some problems.
After processing the imaging, using Sentinel 1 toolbox (SNAP), we have been
obtained this kind of image (see file attached). In this image appears
wind direction (with ambiguity) and velocity in m/s.
Where I tried to export these parameters those that are exported are in
the .txt file attached.
My questions is: 1 - How to extract the wind velocity from these image and
export it in as made in .txt file attached ?
2 - How eliminate the ambiguity in order to obtain the
wind direction?
Do you know anybody that is working in these theme using sentinel 1 data
in order to help me.
With my best regards,
geraldo
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Hello, try to save the txt file as excel format.
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At Present i am working on Building Aerodynamic, i have modeled a group building models and analysed in CFD. Now, I want to verify my result in wind tunnel. I am getting problem in scale down model according to non-dimensional analysis, to match Reynolds number for model and prototype.
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Dear Vignesh, depending on what you want to measure, but I think you should use as characteristic length the width of the building or its dimensions in the main direction of motion of the flow.
Let me add the following information FYI: the validity of wind tunnel results obtained in testing of scale models is based on the fluid mechanics Principle of Dynamic Similarity (White, F.M., Fluid Mechanics, 6 ed., Boston, USA: McGraw-Hill, 2003, p. 866) which states that: "If two physical phenomena can be described using the same formulation (same equations and same initial and boundary conditions), the solutions for one of the phenomena are valid for the other one." For the motion of air around and obstacle, this Principle guarantees that the non-dimensional results measured in a wind tunnel for a scale model (e.g., lift, drag, and pitching moment coefficients) will be the same as for the real, full-scale obstacle if the following conditions are fulfilled:
  1. Geometric similarity: all relevant aerodynamic features of the real obstacle must be accurately replicated in the scale model
  2. The Mach number must be the same for the model and obstacle θ γ
  3. (as you said) The Reynolds number must also be the same
  4. Heat transfer (thermal effects) and diffusion can be neglected
For CFD, this is not usually a problem, since you have much flexibility in defining the boundary conditions and other settings such that these 4 conditions are satisfied and, for example, Re and M match those of the real fluid problem.
Now the dilemma comes when trying to extrapolate wind tunnel results to the real fluid problem: If the fluid properties for both the tests and real case are the same (i.e., same speed of sound (T), ρ and μ), and the scale model is smaller or larger than the real obstacle, it is obvious that it is not possible to have simultaneously the same M and Re as in the real problem. If we cannot replicate simultaneously both parameters, it is then necessary to choose which one will be kept similar to the real case. Generally, we choose the parameter with a stronger influence on the flow. For instance, roughly speaking M is dominant for supersonic flows and Re for subsonic flows (your case). Thus, for example, in high-subsonic testing, we would strive to work with the same Re as in the real case, and would not pay so much attention to M. Effectively, this means that we are not complying fully with the requirements of the Principle of Dynamic Similarity, and thus the test results have some error respect to the behavior in the real case. Many researchers have characterized the Re and M scaling effects to be able to correct for this error when extrapolating the wind tunnel results to the real case, if the Re and/or M in the tunnel are different than those of the real case.
If the fluid properties for both your tests and real case are the same, you should try to work with a model as similar as possible in dimensions the real obstacle, bearing in mind also these recommendations (Barlow, J.B., Rae, W.H., Pope, A., Low-speed Wind Tunnel Testing, 3 ed., NY, USA: Wiley & Sons, 1999, p. 713):
  • Blocking coefficient (ratio of frontal area of model to frontal area of test chamber): should be less than 0.1
  • Wingspan (or width) of the model: should be less than 4/5 (80%) of test chamber width
If you manage to have same Re and M, then the lift and drag coefficients (cL = Lift/(0.5*rho*V^2*S) and cD = Drag/(0.5*rho*V^2*S)) that you obtain from the tunnel can be extrapolated to the real vehicle. If you manage to have only the same Re, the lift and drag coefficients that you obtain should be corrected, but this error should not be very large and maybe the values from the tunnel are still valid to you. If you don't manage to have the same Re, then you could correct the cL and cD following the procedure described in the attached image from White's book Fluid Mechanics, for which you need to have values of cL or cD at several flow velocities (i.e., at several Reynolds numbers).
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What is the most accurate way of calculating wind direction (2D NESW), wind speed and vertical wind movement using 3D Ultrasonic Anemometer data in the form of uX-uY-uZ m/s (or U-V-W vector) data? I am looking for calculations, methods and/or sources for these approaches.
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Hey,
I am working on the Multi body dynamics of a 300kW VAWT as part of my graduation thesis. I have created a reduced order model of the turbine using SIMPACK (MBD solver from dassault systems). I am facing some difficulties with running modal analysis due to error in modal matrix being singular.
I am reaching out to people who have worked with SIMPACK, hoping to get some help with my model .
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I think Anays Rigid Dynamics will give you all the possible options in comparison to any other tool. Try for it to cross verify the results.
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I'm looking for the airfoil characteristics for SAND 0018/50 (SANDIA 0018/50) that is used wind turbine (VAWT of Darrieus type) tabulated for different Angle of attack and Reynold number?
Any suggestions are highly welcome.
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Dear Amin,
I was also going to suggest you to use QBlade. QBlade is open source software for design and simulation of horizontal and vertical axis wind turbines (HAWT and VAWT), distributed under the GNU General Public License.
What is most interesting to you is that its integration in XFOIL allows airfoil design and airfoil performance analysis, and even allows also for extrapolation of airfoil performance data to 360° angle of attack, etc. That is, QBlade, using panel methods, allows obtaining for any given airfoil the lift and drag coefficients for different angles of attack and values of Re. You can download QBlade and manuals here: http://qblade.npage.de/
If the specific airfoil that you want to test is not available in QBlade's airfoil library/database, in the following UIUC's link you can find the airfoil coordinates to import to QBlade: http://m-selig.ae.illinois.edu/ads.html
Hope this is useful,
Jose
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I found that energy efficiency deals with combustion efficiency, using biomass fuels and stuff like that. Can we link between wind energy and energy efficiency by some means?
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Hi Ahmed, renewable energy is a type of energy which is inexhaustible, while energy efficiency deals with utilising the existing energy irrespective of renewable or non renewable, judiciously. that is, getting the work done with less expenditure of energy without the loss of quality. For example a bulb that draws 3W of power to light a room compared to the similar bulb that draws 5W power to light the same room, is considered to be energy efficient. further if the same bulb utilises electricity obtained from fossil fuel, it is considered to be energy from non renewable source. If the same power is obtained from water or wind energy thn it is energy from renewable source.
hope it helps!! :/
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How could I use this tool to reach to wind pressure distribution over simulated building and How could I deal generally with the results?
Thank you
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Thank you Leighton Cochran
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People feel uncomfortable in the upper stairs of the tall building when the building move laterally due to wind load or to be accurate the lateral acceleration of the building. Is their any recommendations or limits in code provisions for this acceleration.
Thanks
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thank you Leighton Cochran
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Could wind tunnel provide accurate results to wind load distribution over the building?
What if the building is very flexible like cable stayed bridges or tall building. Could it be simulated using wind tunnel?
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Khaled. Yes, the buildings and structures you mention (and many other human constructions) are routinely studied in wind tunnels every day. Some at universities (eg UWO, CSU, TTU, UF, Monash, HKUST, etc.) and some at commercial facilities (eg RWDI, CPP, MEL, etc.). The success at modeling various actions on a small-scale model in the wind tunnel has been well-established and refined since the 1960s. There are dozens of wind-engineering societies and associations in many countries around the world (AAWE and AWES to name two I belong to) and these are all connected to the international body, IAWE. The best assessment of "accuracy" is to compare the wind tunnel with a full-scale building in the real wind. There are several good examples of this (a well-known recent example was the Texas Tech University Building that spanned work over the 1990s and 2000s, and an earlier effort in Britain called SILSOE) in the literature and, with some caveats, the agreement is really quite good between model and full scale data. The Elsevier journal called Journal of Wind Engineering and Industrial Aerodynamics has been the source of many papers in this field for over 40 years. Lots of reading for you!
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As far as I know, almost always the mechanism of the design of wind turbines is for one direction, which it generates electricity-power based on one way of the main wind in the particular region where is installed and it has been designed for the best efficiency of it, however my question is that regardless the mechanism of the turbine, should we consider the effects of the opposite direction wind, i.e. effects like the fatigue phenomenon for designing the most effected parts of the whole structure like the foundation of it?
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Thank you very much professor Giorgio Soave for the helpful comment, truly the very proper word for the direction of the wind is prevailing direction. As for the foundation, and more specifically the concrete itself which measures could be recommended?
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In textbook I read this sentence "In the case of positive aerodynamic damping the forces generated by motion through the airstream tend to oppose the motion. Negative damping tends to reinforce the motion. "
Why the damping is negative?
What is the physical meaning of the aerodynamic damping?
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thank you Hayrani Oz
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& is there anyway to apply internal and external pressure coefficient in staad?
if yes,How can we calculate that value(based on IS code) 
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Please check reference below.. hope it will be helpful for you… Regards…
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I have a boundary layer wind tunnel, and I have Pitot Tube Dwyer 160E. And I need to use a differential pressure sensor to have measures between 0 - 30 m/s, or 0 to 500 Pa. Can you recommend a good one, Please
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The most sensitive of the Microswitch pressure transducers (sealed, plastic, robust device about 50x25x12 mm in size with two pressure ports) are inexpensive and at very linear in the calibration in terms of Pa/V. From memory around 100 Pa/v when you calibrate with screw-driven syringe, or similar. Good luck. LC.
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I have a question on wind flow around the building using CFD. Why the most of the people are using steady RANS (RANS) models instead of Transient (URANS and LES). The flow will be stochastic turbulence in nature, but most of the reputed papers on wind flow around the building, ventilation, pedestrian comfort etc.., are used SRANS (STEADY RANS), models. 
Thanks advance
looking forward the answers.
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Rajasekarababu,
In most of one phase industrial applications, RANS is a pragmatic choice. This is explained by the robustness, ease of use and efficiency of the RANS.
However most of multiphase flows are highly transient and steady state approach does not work.
Some industrial applications expose limitations to the RANS modelling approach. For these applications, LES and DES provide a viable alternative at the expense of increased complexity and simulation time.
Regards
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LCOE = NPV(CAPEX+OPEX)/NPV(GENR)
or
LCOE = CAPEX+NPV(OPEX)/NPV(GEN)
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Your first equation is correct. You may refer to the following relevant sources to the LCOE calculations, and its estimation for wind, and solar-PV energy sources. Good luck
Deleted research item The research item mentioned here has been deleted
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Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be converted to electricity.Wind turbines have been used as a source of renewable energy for generating electricity in certain countries without others. What are the most important factors limiting the installation and use of wind turbines to generate electricity in a particular area?
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The climate conditions in that area, in particular the average value of wind speed, and the ecological considerations like the migration of birds. Also we should not forget the economical justifications to construct such a plant, in other words how much cost one-kilowatt per hour from this plant comparing with that produced from fossil-fueled plants.
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I need to calculate the forces caused by vortex shedding(or vortex induced vibrations) on a tapered cantilever structure under wind loading.
I did some reading and some researchers suggests to calculate the response using some empirical equations to include the motion induced forces due to lock in and negative damping as I understood.
Your advice and suggestions will be appreciated.
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I would look on line for the Strouhal number of similar structures at similar Reynolds numbers to see what is already been done. When in doubt 0.22 is a good first guess at the Strouhal number. From there I would set up an excel spreadsheet with different heights above the base plane, then do a 1/7th power law for the boundary layer effect and calculate the wind velocity in 10 or so different points up the height. From there you should be able to get the vortex shedding frequency as a function of wind speed and height to compare to your structural resonances. Figuring out the unsteady lift force is more problematic from first principles but I bet there is a lot out there in the published technical literature. Good luck
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In analysis of lattice towers in wind why only dynamic analysis done. What about the static pressures of stagnation due to incidence of wind ?
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Generally there are two approaches for calculating wind pressure: Static approach and dynamic approach. The dynamic approach is more realistic , so it is preferred for any type of structures. Consequently, the dynamic approach is also preferred for towers.
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In the analysis of wind energy cost, Investment (I) is included and covers the turbine price plus 20% for civil work and other connections. For a machine size above 600kW, I would like to have an actualized reference about the specific cost of wind turbines for different size ranges.
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Hello
I am working on Flow Control in Wind Turbines and as a startup I need to select the airfoil and design the blade in accordance.Power coefficient is taken generally as 0.4 as I have taken 3 bladed turbine  and efficiency to be 0.9.Can anyone tell me what is the conventional steps to be followed while designing the blade?Should I fix the rotor diameter before going for design? In that case how I can fix the rotor diameter? 
Thanks in advance
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Hello, I have a HAWT blade and I want to know what is the value of the chord of it because we have many chord lengths of the same airfoil due to the loft technique...Thanks 
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Hello
I am focusing on Wind turbine blade design with flow controls and as a preliminary work,I have to design the blade.WInd turbine blades are not like the conventional wing and they need a different modelling methodology.Can anyone share or tell how to proceed with the blade design and how it can be modeled 
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There are PMIG and DFIG Technology which is used as recent wind turbine in operation in india and in other country
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Recently, some engineers have patented Magnus type wind turbines with a number of rotating cylinders acting as blades. Some of these wind turbines use spiral ribs along the cylindrical blades to improve the lift-to-drag ratio. I have some doubts about the real effectiveness of such blades especially from the point of view of the net power output. Are here any experts or anyone who studied it?
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I have analysed the unsteady forces calculated by FAST v7 to get the periodical unsteady forces to check the fatigue due to them.
I got fn and ft for 30 station on the HAW blade of 7m length.
The time length was 151 seconds and step was 0.004 s.
My procedure was to get the max fn in each time step and assuming it is acting on the blade at this time neglecting the position and the other components to simplify my analysis.
I made fft analysis and got the periodical ones and I assumed that for the next 151 seconds these forces will repeat themselves.
The results of fft (Fn vs frequency) and fn in time domain is shown below
Can you tell me your opinion on this procedure?
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can we discuses some of necessary requirements to avoid the failures in wind turbine ? And how we can calculate the time that the wind turbine is ready for production?
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Hello,
I agree with Tony Maine that failures always have non-zero probabilities; however, they can be reduced. There are several ways for achieving that target, such as,
1. Condition, and diagnostic-based monitoring,
2. Preventive maintenance,
3. Enhancing the maintainability of the systems through better designs, sufficient logistics, and technical training.
4. Careful selection of protective devices and subsystems and proper setting of their operation constraints.
5. Oversizing and redundancy of components.
Of course, the reliability is accompanied with costs and so the failure. Therefore, optimal techno-economic reliability level should be determined. There are some relevant publications in my RG profile. Please feel free to read them.
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Comparing a building in a low density area, with another one located in a dense urban neighborhood; the wind speed on facades and therefore the temperature of the facade elements varies.
Is the effect of wind speed in such cases marginal or significant? How necessary is that to couple CFD analysis with heating/cooling energy simulation (e.g. using EnergyPlus)?
I would appreciate it if you could reply by referring to valid reference books/scientific papers.
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Dear Mehdi,
Could you please explain about how you could come up with "4 percent"?
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Working in the optimization of power supply to isolated communities with renewable sources. It is necessary to establish the best combination of generating units.
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Hello,
The RETSCreen software includes one of the most complete, and continuously updated database of renewable energy products including wind turbine generators of various scales.
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Can anyone give me a complete explanation about using 3 blades on a wind turbine instead of another number especially in the utility-scale wind turbine types?
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Dear Ali,
Regarding your question, I am attaching a document (even in french) in which it is shown the number ob blades impact on the power coefficient (Cp - left figure)) and the Yaw Moment (right figure) of a wind or marine turbine. When analyzing these curves, it came obvious that a three-blade turbine is the best choice in terms of Cp (even reduced but with a larger TSR range) and Yaw Moment (less oscillations of the turbine pile).
Regards,
Mohamed
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I need to optimize an airfoil using dynamic characterization for which I need to calculate the pitching moments vs. time. I am very new to GH Bladed. Can anyone suggest me where would I find tutorials for plotting such time varying parameters? 
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My Thanks to you was long pending...Thank you!
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Hello Everyone, I am also facing the problem of TI decaying very fast in my simulation of turbulent flow . I am modeling the flow around 2D square cylinder and used k-e model. I made the model in ADINA and computed the values of k and e based on TI, length scale and mean flow velocity. I don't have the option of entering the turbulent viscosity. So any suggestions on how to solve this problem?
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Dear Divye Malik
you can put the following steps:
1- the turbulent intensity at the entrance about 0.05 and make a long entrance region, you can read the following papers;
2- make a long entrance region and  you can read the following papers;
3- make the upper and lower boundaries as symmetry.you can read the following papers;
you can read the following papers;
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Hi, I am currently an architecture student doing a research study related to wind engineering. I have been using the Australian standards to help me calculate the wind internal pressure and get the external pressure coefficient but I have a problem in understanding when the wind speed is taken at height z. I understand that for leeward and side walls, and roofs the wind speed is mostly taken at height z but for the windward wall, when is the wind speed taken at height z? Thank you.
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Hello, I need this model for my thesis, any help would be appreciated.
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Yes, I know the  synchronous generator wind turbine theoretically and practically well, because also I have treated with it in my PhD when I have designed new Electric Rotary Converter Machine. You can follow and read my published papers in my profile in Google Scholar (Khalid G. Mohammed). My regards
Dr. Khalid G. Mohammed
University of Diyala, College of Engineering, Iraq
Aug.14, 2017
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Hi,
I need statistics regarding annual average wind speeds (preferably at 50 meters height) in India and Pakistan for the period between years 2000 and 2010. I would appreciate if you could kindly guide me how to get such data?
Thanks
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I can also recommend using MERRA-2 which is available here: http://www.soda-pro.com/web-services/meteo-data/merra
The platform itself is very user-friendly and works quite fast.  
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Hello
I am working on design of NACA 63415 airfoil for my research.Besides computational methods,I am interested to do the profile mathematically.Can anyone tell me what is the chord length equation for a 6 series NACA airfoils.Thanks 
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I have the wake height and width behind a scaled down car model from a wind tunnel experiment. I am not sure how to compare the wake of this scaled down model with the actual body and get the estimated height of wake behind the car in actual condition.
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Dear Abhishek,
Ingo is right. Just let me add the following to his explanations: The validity of wind tunnel results obtained in testing of scale models is based on the fluid mechanics Principle of Dynamic Similarity [1] which states the following: "If two physical phenomena can be described using the same formulation (same equations and same initial and boundary conditions), the solutions for one of the phenomena are valid for the other one."
For the motion of air around and obstacle, this Principle guarantees that the non-dimensional results measured in a wind tunnel for a scale model will be the same as for the real, full-scale obstacle if the following conditions are fulfilled:
  • Geometric similarity: all relevant aerodynamic features of the real obstacle must be accurately replicated in the scale model
  • The Mach number must be the same for the model and obstacle: M = V/a = V/sqrt(γ·R·θ)
  • The Reynolds number must also be the same: Re = ρ·V·L/μ
  • Heat transfer (thermal effects) and diffusion can be neglected
And here is the big Dilemma: If the fluid properties for both the tests and real case are the same (i.e., same speed of sound (T), ρ and μ), and the scale model is smaller or larger than the real obstacle, it is obvious that it is not possible to have simultaneously the same M and Re as in the real problem. If we cannot replicate simultaneously both parameters, it is then necessary to choose which one will be kept similar to the real case. Generally, we choose the parameter with a stronger influence on the flow. For instance, roughly speaking M is dominant for supersonic flows (meaning that the value of M has a stronger effect on the behavior of supersonic flows than the value of Re) and Re for subsonic flows. Thus, for example, in high-subsonic testing, we would strive to work with the same Re as in the real case, and would not pay so much attention to M.
Effectively, this means that we are not complying fully with the requirements of the Principle of Dynamic Similarity. Fortunately, still the wind tunnel results can be useful. The only issue is that they have some error respect to the behavior in the real case, and we have to correct for that. Many researchers have characterized the Re and M scaling effects to be able to correct for this error when extrapolating the wind tunnel results to the real case. So, if the fluid properties for both your tests and real case are the same, you should try to work with a model as similar as possible in dimensions the real obstacle, bearing in mind also these recommendations [2]:
  • Blocking coefficient (ratio of frontal area of model to frontal area of test chamber): should be less than 0.1
  • Wingspan (or width) of the model: should be less than 4/5 (80%) of test chamber width
Hope this is useful,
Jose
[1]  White, F.M., Fluid Mechanics, 6 ed., Boston, USA: McGraw-Hill, 2003, p. 866
[2]  Barlow, J.B., Rae, W.H., Pope, A., Low-speed Wind Tunnel Testing, 3 ed., NY, USA: Wiley & Sons, 1999, p. 713
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I want to analyze a 110 story building for performance based wind engineering, how/where do I get wind load time history data from ?
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The following link is presenting time history of wind pressures on tall building:
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How can optimizing blade of vertical axis wind turbine by using Ansys Fluent?
And what can Ansys Fluent do?
Thanks.
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Why do I get infinite power coefficient solution at the root of wind turbine blade in aerodynamic analysis using blade element momentum theory?
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In the base region about 20% of the blade is usually a torque moment large enough and the value of force lift is small, so it is very difficult to get unlimited power in the root of the blade.
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To work out the aerodynamics of vertical axis wind turbine (VAWT) and probably the HAWT, we need to know Reynold number (Re) to use it along with angle of attach to find the drag and lift coefficients (Cd & Cl) from the airfoil characteristics, I would like to know which velocity we use to find Reynold number, Re=v*L/neu, is it the induced (axial flow) velocity (assuming that MST or DMST is considered), or the relative velocity, or the tangential velocity Vt=Omega*R?
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Amin- You are right. You may use free wind speed if you are working on large Reynolds number. However, technically, you should be using relative wind speed, especially for small wind turbines. Thanks and best
Thanks and best wishes
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I design a Darrieus turbine with adjustable blade angles to improve the efficiency of the turbine at low wind speeds.
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The cycloidal propeller StECon works as well horizontal as vertical, because it truns completly under water. The first project StEwaKorad concludes a vertical construction with a gaer outside the water. Now we discuss for a gear filled with water for grease.
The StECon will run also in the wind, but we are looking first for an application in water.
In comparison to an Darrieus-Propeller the blades of the StECon turn arround their own axis and therefore the gear is necessary.
If you are interested have look at www.stecon.xyz and let me know more questions.
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I am trying to design a wind turbine blade and came across these two methods. Looking at the variation in the chord length these methods have while calculating near the rotor hub, which method provides better practical results?
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Betz limit gives the maximum theoretical output power of wind turbine Cp=0.59. The popular method for finding chord and twist angle of turbine blades is BEM (Blade element momentum) theory with rotor tip and root corrections.  
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"disk loading" is also called in some papers " screen factor"
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Many thanks Seghiour
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I have the turbulent intensity values derived from the Standard deviation of the mean wind speeds, and the mean wind speeds themselves. I also have the mean yaw position of the turbine. 
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Try to google it, You will find many papers and articles
regards.
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Can you please give me insight on optimization of wind turbine blade (Mathematical modeling for same)??
You may cite reference for that
Thanks
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Thanks you dear Itsuya Muta sir and all,
I am very thankful to you and above all who has paid their kind attention to this question
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as per the Indian criteria 
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Dear sir
I my page please find paper exergy analysis and optimization of wind turbine. I hope it can be helpful
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I am trying to use the wavelet analysis to investigate the trend of the SST and wind speed time series. Now my question is:
How can I use the wavelet analysis to see the trend of time series?
I am very grateful to you if you can provide me the answer of my question and suggest me the useful papers related to this topic. Thank You.
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There are several of works that deals with the application of Wavelet in the analysis of Elnino
You can start with
- Grinsted A, Moore JC, Jevrejava S. “Application of the cross wavelet transform and the wavelet coherence to geophysical time series”. Nonlinear Processes in Geophysics 2004;11:561–6.
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I would like to know whether vertical axis or horizontal axis wind turbine give more structural load to its tower given all other conditions and specifications are the same (power output, height, wind speed). The size may differ for both as long as the rated power output at a given wind speed is the same.
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Given all other parameters being the same, the horizontal axis wind turbines cause less vibrational loads and torque on the tower compared to the vertical axis wind turbines. 
I think this is a testimonial that the horizontal axis wind turbines have the largest market share compared to the vertical axis wind turbines.
Hope this helps answer your question.
Professor Yehia Khalil, Yale University, USA
Fellow of the University of Oxford, UK
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If one is trying to identify the area in the region, where hybrid renewable energy is more appropriate, one would like to combine solar insolation and wind power data to be super imposed on one another. This may cater as feasibility analysis before going into the diurnal analysis of complementary nature of VREs at certain location.
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It may be of no use to find out that solar and wind energy resources complement each other on a monthly basis - as most weather data are offered. You have to perform simulations in order to know the real situation of the hybrid plant. It does not help much to have simultaneity of wind and solar resources if your storage capacity is dimensioned for one of the sources only; it does not help if there are too long gaps in the availability along time, so that your storage capacity is not big enough, either. I do not believe in such a graphical representation.
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please can someone help me in modeling a wind turbine with a DFIG ? i need your suggestions pllz
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Dear Idrisi,
For WInd turbine model, you can find such model in the Matlab simulink demo.
Also you can find some examples for the DFIG in MAtlab DEMO.
for more details please check the following
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The wind turbine would be a savonius or maybe a Darrieus. It would be used for urban zones. High power capacity would not be really needed. The economic factor is really important. So, PMSG?, IG?
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PMSG are best suited for low-speed and also low-power wind turbine applications.
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The distance between the sonic anemometer transducers decides the lower limit to the size of the eddy being measured. But equally, this distance is also dependent upon the ability of the transducers and associated control and conditioning circuits to respond rapidly enough with the necessary increasing measurement frequency as the transducer separation distance decreases. Also the physical size of the transducers plays an increasingly important role in disturbance of the wind field around the anemometer as the distance shortens. This is an instrument question - not a theoretical one.
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As you say, it is a small World. I know all those and have worked with them all, some more than others
BR
Søren
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Hello, I am working on the simulation of a wind turbine (5MW-Sinovel SL5000).But, I don’t have data of a DFIG generator (5 MW), moment of inertia, coefficient of various friction and gear-box.   
Please provide me the data if anybody have it.
Thank you for your help.
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Thank you Vinicius Dadalto for your help.
In fact, I worked on the “Robust control by sliding mode of wind turbine based on Doubly-fed Induction Generator” on my M.S work. And now, I continue my PhD work in the same road, i.e. modeling and control of doubly fed induction-generator (DFIG) based on the wind turbine systems. Currently I want to control the MPPT and the pitch angle by fuzzy logic. I need your help if you can. Can you give me your mail please?
Best regards.
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What is need of putting gcin wind power calculation.
does it shows the effect of geographical location on air density or on velocity.
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Hi,
I want to get the total output power of a wind farm. I only have an annual wind speed with 10-minute average in one location, but I want to get the information with more information, thus I have to add some turbulence into our measured 10-minute average wind speed.
I don't know how to do it
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Hi all,
I thinks this is good reference for my question. Hope it could be useful for others with the same question.
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Hello everyone,
I am developing my graduation project at Unesp Sorocaba - SP Brazil.
I chose as the theme: Fuzzy logic applied in pitch angle control for wind turbines.
I studied a lot about wind turbines and I realized that the generator most used is the DFIG (Double Fed Induction Generator).
But this type of generator is a bit more complex than a SCIG (squirrel cage rotor) or even a PMSG that uses permanent magnets as a stator.
So, I decided to use a SCIG, since the focus of my work is on pitch angle control.
But, the behavior of the generator is really important to the analysis, because I need to compair the results of the power (active and reactive).
This way I have to use reliable parameters that bring reality to my model. And that's my problem. I'm not finding the parameters I need to simulate a wind turbine. I found some data from a turbine made by Vestas, the V39, but aerodynamic parameters can not be found.
I'm using a template in Simulink. I'm adapting this model.
Is there anyone who could help me in this. To point one way. Any tip will help a lot!
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Mr Bhupendra and Mr Mohamed,
Thank you very much for your help!
Mr Mohamed, I'll study these papers sir. Thank you very much.
Regards
Vinícius
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 i got a Torque as 137797N-m and rotational velocity is 2.22rad/sec.moreover i took fullscale GE1.5xle model whose rated power is 1.5MW.kindly suggest how to get the power coefficient in fluent?
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Hi,
Usually using "C_m" in fluent is a good choice.(Torque coefficient)
You can active "C_m" in fluent (in monitors) and by using:
C_p=C_m*TSR
calculate power coefficient.
It's very important that using correct reference values in fluent.
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one of the serious problems in Vertical Axis Wind Turbine simulation is negative torque value. I searched the internet and found that TSR<1 (Tip Speed Ratio) result in negative torque value most of the time but in some simulations for TSR<1 , torque values are positive. I am simulating a 2D VAWT in ANSYS Fluent 16.
What is reason for negative torque values? Is there any solution? 
appreciate any help.
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Can you look at the pressure contours near the blades? And the velocity vectors? You should be able to estimate the angle of attack from the vectors and see if the pressure contours make sense according to experiments on airfoils (highly documented)
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I searched in possible PhD topic in VAWTs especially the structural mechanics or optimization however most of things I 've found are related to aerodynamics only. 
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Dear Ahmed,
I suggest to you a links and attached files in topics.
-Offshore floating vertical axis wind turbines: Advantages ...
-Dr Lin Wang Research Fellow in Structural Mechanics