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-   -   CFX for windturbine please help me. (http://www.cfd-online.com/Forums/cfx/91050-cfx-windturbine-please-help-me.html)

forgetmenotk July 28, 2011 14:28

CFX for windturbine please help me.
 
Hi there,

I just new for CFX and I am trying to make 3D analysis of 3 blades horizontal axis wind turbine at steady state. I put the domain like picture below
http://img855.imageshack.us/img855/9266/windtunnel2.jpg


I set boundary condition as inlet, outlet, wall (I also set the red zone as wall) and set boundary interface as fluid fluid / frozen rotor. the program is run succesfully but the result that I got is too high (but no that much) I got Cp around 0.52 which is not possible for this design (normally it should be around 0.3-0.45).

Dose anyone have better method to develop the domain of this problem. I just thinking to do other domain like the picture below.

http://img64.imageshack.us/img64/1282/windtunnel.jpg

but I got a problem that I cannot insert domain interface in the orange area. what domain interface I use to use for this area?

If anybody has an experience to do 3D WT test please suggest me. I really need your help...I need to make it close to reality as much as I can.

Regards

ghorrocks July 28, 2011 18:34

You certainly have the outer tunnel too close to the blades. This will cause a constricting effect on the flow and make the result inaccurate compared to measurements taken in open atmosphere.

Your orange region should work fine as a normal GGI.

forgetmenotk July 30, 2011 12:21

Thank you very much , now everything is fine and the results is much more better and reality. And can I ask you another question? I just wann use the results from CFX to import for acoustic analyze but I dont know what function of ansys I have to use.

Regards
forgetmenok

ghorrocks July 31, 2011 06:53

I have heard of people linking CFX to SYSNOISE - ask CFX support for details.

forgetmenotk July 31, 2011 10:07

thanks you very much, I ll try to find it.

Regards

bhatiadinesh August 3, 2011 00:28

If you want to find the noise only a blade pass frequencies then you can export the data using the Dipole function in a transient run found in the exports tab. Then use the data as an input in SYSNOISE or any other such software to evalutae the SPL at BPF Frequencies. Keep the timestep frequency at least 8 times the BPF Frequency to get a passable flow resolution for noise evaluation.

-Dinesh

forgetmenotk August 3, 2011 17:16

Thank you,

I have another question... the domain that I set which use frozen rotor I need to set some value of RPM (I know the value) but it seem to give me the answer at steady state of design RPM at any wind speed.

I just wonder if there are any method to simulate force acting on the blade and rotate the blade in transient?

Forgetmenotk

forgetmenotk August 3, 2011 17:18

I mean the output I want to know more are RPM and Torque at anytime, for example t = 10,20,30

altano August 7, 2011 10:22

Quote:

Originally Posted by forgetmenotk (Post 318768)
I mean the output I want to know more are RPM and Torque at anytime, for example t = 10,20,30

You can't get that with cfx.

Angular velocity is not an output.

Maybe you should create several def file with diffrent rpm (around design point) and get torque value for each. Then put that values to a chart, trend may gives you an idea about what u want to know.

bhatiadinesh August 9, 2011 04:22

Hi,
if you want to simulate the actual rotation due to wind forces then you need to go for FSI simulation, give the flow as inlet and get the rpm and torque as output. If your domain is completely symmetric about the axis of rotation, you shouldn't find a variation in RPM and torque with time. Only if your input is varying you should get a variable RPM and Torque with time in an FSI simulation.
The best way( although a very lengthy one) would be to come up with a operating chart for the wind turbine with delta P v/s mfr at different rpms, and get your result. Initially you can go for only 2-3 rpms and 3-4 mass flows at each RPM's

-Dinesh

ghorrocks August 9, 2011 06:47

I think you will find working out the fan operating curve using guessed rotational speeds at various wind speeds and loads is faster and more accurate. The FSI approach is not easy.

forgetmenotk August 9, 2011 14:33

Thank you for everybody. I know the RPM at any certain velocity from BEM calculation and that was I did at the first time. Right now I got some problem about the gap between rotational domain and outer domain. I try to vary and simulate its but the results is a bit different and I dont know what exactly length of the gap between that. I might have to try again til I got very close results between two difference gap.

Regards

shabaz88 January 9, 2012 13:53

i am also desighning a simallar model i have made the same domain as your first image. i just want to clarify something: did you get better results by increasing the domain size of your first model in the firs timage?

RS2 January 26, 2012 02:32

Quote:

Originally Posted by bhatiadinesh (Post 319422)
Hi,
if you want to simulate the actual rotation due to wind forces then you need to go for FSI simulation, give the flow as inlet and get the rpm and torque as output. If your domain is completely symmetric about the axis of rotation, you shouldn't find a variation in RPM and torque with time. Only if your input is varying you should get a variable RPM and Torque with time in an FSI simulation.
The best way( although a very lengthy one) would be to come up with a operating chart for the wind turbine with delta P v/s mfr at different rpms, and get your result. Initially you can go for only 2-3 rpms and 3-4 mass flows at each RPM's

-Dinesh


Hi Dinesh,

The problem with FSI method is the mesh creation. How to create that Patran Neutral type file which has .out extension as given in tutorial.

Does ansys supports creation of such mesh files. If no, which softwares have capability to do such kind of meshes.

Thankyou.

ghorrocks January 26, 2012 07:05

Patran neutral files come from - Patran, of course. Talk to MSC (or what ever they call themselves now) about Patran.

But I would use the ANSYS meshing tools as they are better integrated into CFX.

Lacerlacer February 6, 2012 02:02

Finding of the power coefficient
 
Quote:

Originally Posted by forgetmenotk (Post 317932)
Hi there,

I just new for CFX and I am trying to make 3D analysis of 3 blades horizontal axis wind turbine at steady state. I put the domain like picture below
http://img855.imageshack.us/img855/9266/windtunnel2.jpg


I set boundary condition as inlet, outlet, wall (I also set the red zone as wall) and set boundary interface as fluid fluid / frozen rotor. the program is run succesfully but the result that I got is too high (but no that much) I got Cp around 0.52 which is not possible for this design (normally it should be around 0.3-0.45).

Dose anyone have better method to develop the domain of this problem. I just thinking to do other domain like the picture below.

http://img64.imageshack.us/img64/1282/windtunnel.jpg

but I got a problem that I cannot insert domain interface in the orange area. what domain interface I use to use for this area?

If anybody has an experience to do 3D WT test please suggest me. I really need your help...I need to make it close to reality as much as I can.

Regards

hi forgetmenotk,

I would like to know that how u are actually extracting power coefficient from CFX? I am doing a similar research, the literature show Cp = (torque*RPM*2*pi/60)/(0.5*density*A*V^3). We pre-set the RPM of the rotor, density , Area, and velocity, and what left is the torque value right? torque value is get from CFX with the function built in? torque_<axis of rotation>@blade right? Thanks alot for the help! :)

Regards,
Lacer


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