[federvo.mala]

Originally Posted by sarah4

Hello Federvo


I am wondering why your flow direction is -1 for "Y" direction, while your rotational direction is +1 for "Y".

I can see from your picture your turbine rotates +Y, then flow direction (from inlet to outlet) should be +1.

Am i right? Or i missed something?

Thanks.

Well, you can't see the axis orientation, but the the flow comes from the positive towards negative part of the Y direction, hence the minus. And as you can see the frame is rotating about +ve Y clockwise.

[sarah4]

Originally Posted by federvo.mala

Well, you can't see the axis orientation, but the the flow comes from the positive towards negative part of the Y direction, hence the minus. And as you can see the frame is rotating about +ve Y clockwise.

Thanks for your reply but i am still confused:

If the flow comes from the positive towards negative (-Y), then your turbine is rotating -Y (right hand). But you said the frame is rotating + Y. Are you saying that: if the trubine rotates -Y then the rotational flow domain should be defined as +Y?

[tranchitam]

Originally Posted by federvo.mala

HI

1 - yes you are right. Changed to symmetry in my final model.

2 - probably right, but I always used SRF

3 -

I indeed used k-w with intensity and viscosity ratio specs.

I first extracted the torque from Fluent and then calculated power (available) via a simple formula....

What are you working on?

Best,
Fred

Hi Federvo

Have you ever calculate wind turbine with MRF?

My study is I want to rotate the blades when the wind is as the input?

So I have two fluid domains, the rotating is a cylindrical region surrounding the blades, the stationary is also a cylinder representing the far field. There are 3 interfaces for the connections between the rotating and stationary. Most of BCs are similar to your setting.

Finally, I've a problem with pathlines. The pathlines does not continue to spin when it goes out of the interface behind blades. I think the problem is I get wrong setting for interface ! Did you get the same problem ???

Could you give me some advices ?

Many thanks

[federvo.mala]

Originally Posted by tranchitam

Hi Federvo

Have you ever calculate wind turbine with MRF?

My study is I want to rotate the blades when the wind is as the input?

So I have two fluid domains, the rotating is a cylindrical region surrounding the blades, the stationary is also a cylinder representing the far field. There are 3 interfaces for the connections between the rotating and stationary. Most of BCs are similar to your setting.

Finally, I've a problem with pathlines. The pathlines does not continue to spin when it goes out of the interface behind blades. I think the problem is I get wrong setting for interface ! Did you get the same problem ???

Could you give me some advices ?

Many thanks

Hi,

Sorry never done MRF before.

I know what you are saying, and what you want to do is called an FSI (fluid-structure interaction) simulation which is more advanced and have absolutely no experience on this.

MRF should not be too much of a trouble since the BC are very similar.

I remember I had that problem in CFX while doing MRF which bothered me a lot and never found an explanation so I switched to FLUENT with SRF. Anyway, this is likely to be a problem of visualisation and/or interface as you said.

I have not used FLUENT in months so apologise if I can't help you much.

Best

[tranchitam]

Hi Federvo,

Thanks for your reply, your topic helps me so much.

In many papers, MRF is the model is used most, but nobody show the way they set bcs for it!!!

I found out a topic in CFX forum is also talking about wind turbine and MRF model, It's seem that frozen rotor model can solve the problem about FSI. I am going to switch to CFX for trying to fix this problem .

and another questions

1. Here, I still do not quite understand why the input value speed is 7m/s while rotating domain is 7.54rad/s. Is there any formula between them?

2. How to simulate the effect of wind on the blades. Is there any way to rotate the blade with a input velocity values​​?

Thanks alot

[Dorit]

Hi everyone,

I'm currently doing a simulation on NREL too.

I'd be interested in getting some general mesh info on what you've been using:
1) what first cell height gave you what Y+ when using which turbulence model
2) how big are your meshes?

For myself, I generated a mesh if 0.2mm first cell height but it resulted in Y+'s of around 5-10 when using the k-omega model at 7m/s inlet speed. The surface pressure on the suction side of the blade doesn't match well with the experimental data so I've now reduced the first cell height to 0.012mm. Have you guys used similar values?
My overall mesh was about 17 million cells when it was fully structured but I've now created a hybrid mesh which reduced the number of cells to 13 million. I think I should be able to get some good results with that but my convergence is painfully slow. After 15,000 iterations I still don't have a steady solution, although it's heading that way.

How do you calculate cp? In the equation cp=(p_blade-p_inf)/0.5*roh*v_rel^2 where do you get the free stream static pressure from? I wanted to get it from my velocity inlet but it's only 4Pa which seems pretty insignificant compared to the static pressure at the blade surface which goes up to 500Pa in my simulations.

Tranchitam I'm not sure if I understand you correctly but are you saying that you want to do a simulation that mimics the actual start-up of a wind turbine? So that the turbine is initially at rest but as the wind blows it slowly starts rotating until it reaches fully operating speed? If that's what you're trying to do then we should talk some more cause I'm trying to do that too.

Many thanks
Dorit

[monaya flower]

hey Dorit
I am doing asimulation on NREL also .
iam using MRF , kw sst model , i reached the convergence but the torque is very high .

[rami1]

I am doing my project about the wind turbine simulation by Ansys Fluent. First of all I need to know more about wind turbine. Let me know if you know a good book to study before starting work with Fluent.

[zhenglun.wei]

Mostly, I read journal papers for information of the wind turbine. However, here is a text book of wind turbine that is being used in some university:
Wind Energy Explained - Theory, Design and Application.
by J.F. Manwell, J.G. McGowan and A.L. Rogers.

[rami1]

Thanks a lot zhenglun.wei. I have this book and I think at first I can study third chapter of this book "Aerodynamics of wind turbines".Then I want to follow Ansys Fluent tutorials. So let me know if you have any suggestion such as special journal papers which can help me to learn about wind energy & turbine and wind turbine simulation in Ansys Fluent. I appreciated your help in advance.

[s.q]

Originally Posted by zhenglun.wei

Dear Federico,

According to your questions,
With this setup, the far field is affecting the whole flow because is set as wall, how can I set it to not influence the far field, something like open atmosphere or maybe a free-shear wall?
A: As I know, outflow is good option. Conceptually, it just let the flow go out.

Have I set the Moving refererence frame correctly?
A: To my limited knowledge, it is correct. I tried it in a turbine simulation in aircraft engine case before.

And what about the initial gauge pressure at the inlet bc?
A: No idea on this one.

After reading your thread, I have 3 questions:
1, I can not see the Fig.1;
2, Where did you get the mesh file for the NREL wind turbine? Is there any open source for that?
3, Why do you want to use wall roughness = 0? Are you assuming that the wind turbine is pure smooth?


best,
Alan

hi dear
i,m simulating a big (5MW) wind turbine using FLUENT.and i had set just the flow around the wind turbine az MRF.
Do you think is that true????
or it is better to consider all zones as MRF???

[aqstax]

Do refer to this thread:
http://www.cfd-online.com/Forums/flu...i-turbine.html

it will be useful.

[niloogh]

Originally Posted by federvo.mala

You should put '1' on the x axis and leave '0' for the other axis.

For a horizontal axis SRF is fine (based on literature) and suggestions. Although for a vertical one things are different.

hi dear federvo
i had simulated a wind turbine in fluent such as you.
and now the torque amounts which i have got from "report-moment" is about 10 times bigger than real amounts .what should i do???
would you plz help me??

[aqstax]

Hi niloogh,

Do not fret, just keep trying to refine your mesh. Also, try to analyse your setup, and find errors. If you can't find any, posting details will help, as simply stating that your results are inaccurate won't help us help you. Lastly, check out the thread in the post just before yours. It has information very useful to creating a correct setup. I had lots of problems with inaccuracies, which I had to solve myself. I posted my solutions there.

[Zeeshan Nasir]

Hi Monaya Flower, you have worked on a shrouded wind turbine.I am working now on shrouded wind turbine..Can you help me in setting boundry conditions??? I am doing simulation of whole turbine not just a blade...I will be highly obliged..Plz send relevant things on zeshomechi3331@gmail.com

[puri]

i am using srf method .how can i calculate tip speed ratio and power cofficient in fluent .
i have gone through this forum and found cp=cm*tsr but these guys don't tell how to evaluate tsr and cm in detail.please help me i have a deadline of 1 week to meet... pictures will be appriciated