[sivarama1]

Hi,
your wind velocity how much?
I think your inlet boundary conditions wrong,out let you given in pressure @
0 pa know.

[sivarama1]

setup of Angular velocity,
I think to use this formulation for angular velocity ω that must be applied to moving/sliding mesh (that is to the blades) by an user defined function.

ω t = ωt-1 + [Maer t-1 - M res (ωt-1)] / Irotor * Δt

where:

Maer= torque calculated on rotor due to flow
Mres(ω) = function for torque due to electrical energy power generation depending on ω itself.
Irotor = rotor Inertia

[sharan]

Originally Posted by sivarama1

Hi,
your wind velocity how much?
I think your inlet boundary conditions wrong,out let you given in pressure @
0 pa know.

I have considered no wind velocity. Fluid domain is chosen as rotating one with 1500 rpm and reference pressure is taken as 1 atm(which is default value).

[sivarama1]

In NASA WHICH TYPE OF BETTER AIRFOILS

[sharan]

Originally Posted by sivarama1

In NASA WHICH TYPE OF BETTER AIRFOILS

It depends on the application.

For high speed applications laminar flow airfoils (NACA 6 series) are well suited.

Supercritical airfoils are also well suited for high speed applications.

[sivarama1]

Hi all,
please verify this file,
i am sending ram.10 zip file.
In this site limit of capacity is there,please any body give me MAIL ID

[sivarama1]

Another doubt,
I am analyzing wind rotor blade airfoil,i am attaching file please check it out,
wind velocity means free streem velocity 50m/s,atmospheric conditions,
angle of attack 4 dec,
but is converging,results drag and lift coefficents very very high is
comming,i think i given boubdary conditions wrong,
please check it out and let me know
Thankyou.

[sharan]

Originally Posted by sivarama1

Another doubt,
I am analyzing wind rotor blade airfoil,i am attaching file please check it out,
wind velocity means free streem velocity 50m/s,atmospheric conditions,
angle of attack 4 dec,
but is converging,results drag and lift coefficents very very high is
comming,i think i given boubdary conditions wrong,
please check it out and let me know
Thankyou.

where is the file.....

can u mail it to me @ sharantillu@gmail.com
Ill try

[sivarama1]

FATAL ERROR : |
| |
| Initial values are required for all variables in TRANSIENT runs. |
| In this simulation, no initial value was set for |
| |
| Variable : Pressure |
| Domain : rotordisc |
| |
| The value can be set using the Initial Values panel in CFX Pre. |
| |
| To bypass this message and use default solver initial values, |
| set the expert parameter "transient initialisation override = t"

[Andy QUB]

James and Ken (and others),

I have been reading your comments and you seem to know what you are talking about! I am at the early stages of a research project to model a HA tidal turbine (similar to you James). A major difference is that I am focusing on the wake from the device as opposed to its output power. I am planning my geometry/mesh creation at the moment and am trying to decide between rotation techniques (sliding mesh or rotating reference) and whether to generate a single blade with periodic BCs or the whole turbine. I am fairly new to CFD so any thoughts you all have would be greatly appreciated.

Thanks, Andy

[Lysistrata]

Originally Posted by sindhu sati

Vertical Axis Wind Turbine was designed to respond to the ever increasing demand for wind turbines that work well in the urban environment,

The only people who say that seem to be trying to sell something.

I would like to see a more independent assessments of small-scale wind turbine performance in urban areas. Some of the results I have seen are very poor.

In general, small-scale => low Reynolds numbers => low lift, which is not good for lift-type VAWT. Drag VAWT (e.g. Savonius rotors) are not good for generating large amounts of electricity.

[Lysistrata]

Originally Posted by sindhu sati

This new millennium as seen many great changes and perhaps the most notable has been the shift in consciousness amongst the masses toward “sustainable living”.

It seems you are able to give a sales pitch well, but you are unable to back it up with hard evidence, e.g. independent studies that give the efficiency of the VAWT you are touting.

One trend I have noticed lately is an increase in the number of environmental snake-oil salesmen.

[gerritgroot]

Hi all,

I didn't read all posts, but to answer to the first post, to find the optimum rmp you should use a BEM method, CFD is very slow for this.

Next to that, there is no equilibrium rpm! The equilibrium rpm that will be reached depends on the amount of "electrical brake" that is given by the generator. So, the user decides how fast the rotor should go, if you don't it will simply accelerate upto a maximum and not generate any power at all.

Cp depends on the blade pitch angle beta and the tip speed ratio lambda
Cp=Cp(beta,lambda)

- Beta is the angle that the tip chord (even though it's zero, so a virtual tip chord) makes with the rotor plane (defining zero geometrical twist at the tip)
- Lambda is defined as Vtip/Vwind=omega*r/Vwind

If you plot cp in 3D as a function of beta and lambda, you'll find a smooth hill with a certain maximum at let's say (lambda_opt,beta_opt), the easiest way to find this maximum is using a BEM, you then run the CFD at the conditions where the BEM tells you you ought to run it.

I don't see any reason to run unsteady rotor acelerations in CFD.

[saini.yashwant]

Originally Posted by James Date
;32185

Ken

It sounds impressive, but we actually farmed out the solution of this problem to a third party. We only usually run a two node parallel solve cluster where I work at the moment.

The convergence was 1e-2 Max and 1e-4 RMS, this is very unsatisfactory in my opinion. I would have liked to have got to the bottom of this, but the project did not allow. Although the convergence is poor the predicted power seemed to be reasonably close to that found using BEM. In order to get accurate pitching moments the convergence would need to be a lot tighter, I believe.

Ken are you able to let us know a little bit more about your project?

What sort of mesh are you putting around your blade?

Regards James

sir
i am doing wind turbine analysis using fluent. i hav some query with boundary conditions . how to rotate the blade rotor and how to calculate the power in fluent software.
thanks

[jbritton]

Anyone had a play with the rigid body motion in CFX on a wind turbine?

I did for a bit for a seminar we were running but couldn't get it to converge in time so just left it

[Shamoon Jamshed]

Originally Posted by Ken (Wind Turbine CFD Super Rookie)
;32251

Hi Ruibo,

Good to know that someone else is also doing CFD work on wind turbine rotor. First of all, what type of convergence criteria you have on your results? Is the result you mentioned already the final product through mesh dependency test? Based on the 500k node counts my guess is yes, right?

Secondly, you must have impressive hardware capability, only 1 hr of runtime for each analysis with 500k nodes, impresive! By the way, how big is your cylindrical domain?

I don't know how the final result, power is extracted from Fluent, is that number coming from one torque number (already internally calculated by Fluent) or you made a few spanwise cut on calculated sectional torque, than intergrating the numbers to get to the final torque value? If you happen to have experimental results on sectional torque, compare between the experimental and your computational results and find out which span location gives you the maximum discrepancy and work from there. Maybe at certain region or span location mesh is not fine enough? Or have you tried out different turbulence model? Why did you pick K-(can't read) SST model at the first place? Any papers mention this is good for this kind of flow problem, or this is reconmended by Fluent tech support guy? So far I still haven't found any good papers on HAWT papers. You might want to check out some papers on CFD analysis on propeller blades, that might help also, i hope.

Good luck, keep in touch.

Ken

Hi Ken. I am really impressed with a lot of work you have been doing on WTB. Well I am also new to it and I am doing CFD analysis of a single blade. I have two imptnt questions
1. should the airfoil be modeled in facing the velocity at the tip or at its lower side. (if there is no angle of attack)

2. How to compute power from Fluent?

Please reply

[naimishharpal]

Hi Guys,
I am interested to similar work, and a good news is that I have recently discovered a CFD methodology which can calculate the output RPM, Torque, Angular Velocity, and thus the actual Power for a given wind turbine, i.e. no need to define any RPM. As a sample test case, the CFD results and calculations are presented in attachment (URL: https://sites.google.com/a/cfdmax.com/fsi_vawt/). Please have a look and if you are interested, let's have a further chat.

Thanking you,
Naimish Harpal


--------------------------------

Originally Posted by Ken (Wind Turbine CFD Super Rookie)
;32106

Hi James,

So what you are suggesting is to analyze wind turbine rotor just like the way of analyzing engine propeller, i.e. primarily finding out what the torque, power are at a given RPM setting.

If I read you correctly (and please correct me if I am wrong and I am throwing in some numbers here), let say for a 1.5 ft diamater engine prop, by setting a RPM of 1,500 (which corresponds to a tip Mach number of 0.10 or a wind turbine roor tip speed ratio of 3.59) with a forward speed of 10 m/s, I for example got a torque of 0.2 ft-lbf, this translate to a power of 31.41 ft-lbf/s (or 42.65 W). Now I am treating it as a wind turbine rotor. At a wind speed of 10m/s, the rotor will generate 42.65 W of power when it is turning at 1,500 RPM.

Is this basically what you are saying?

Thanks for the time. Ken

[cfd_newbie]

Originally Posted by naimishharpal

Hi Guys,
I am interested to similar work, and a good news is that I have recently discovered a CFD methodology which can calculate the output RPM, Torque, Angular Velocity, and thus the actual Power for a given wind turbine, i.e. no need to define any RPM. As a sample test case, the CFD results and calculations are presented in attachment (URL: https://sites.google.com/a/cfdmax.com/fsi_vawt/). Please have a look and if you are interested, let's have a further chat.

Thanking you,
Naimish Harpal


--------------------------------

Hi Everyone,
Consider my post as a general information.
For the newbies in CFD analysis of wind turbine here are 2 very good papers you should read before starting your analysis.

"Predicting 2D Airfoil and 3D Wind Turbine Rotor Performance using a Transition Model for General CFD Codes",
R. Langtry, J. Gola and F. Menter, ANSYS CFX, Otterfing, Germany, AIAA-2006-0395 44th AIAA Aerospace Sciences Meeting and Exhibit

and

http://wwweng.uwyo.edu/mechanical/fa...-2009-1221-908

Caution - CFD analysis of wind turbine is a tough nut to crack according to my experience.
Raashid

[Lysistrata]

Originally Posted by naimishharpal

As a sample test case, the CFD results and calculations are presented in attachment (URL: https://sites.google.com/a/cfdmax.com/fsi_vawt/). Please have a look and if you are interested, let's have a further chat.

Interesting, but it is for a Savonius VAWT. These drag devices have quite poor performance compared to "lifting" types.

Have you tried modeling other, more efficient, types of VAWT?

[naimishharpal]

Thanks for your comment. Since I was just testing the methodology of rotating frame, I selected a simplest blade profile. My near future target is to apply analogous technique for HAWT, and validating my results. If you can help to suggest me any known experimental data, then it would be grate to me.

- Naimish

Originally Posted by Lysistrata

Interesting, but it is for a Savonius VAWT. These drag devices have quite poor performance compared to "lifting" types.

Have you tried modeling other, more efficient, types of VAWT?