CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > CFX

Wind Turbine - Rotation of the Baldes

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes

Reply
 
LinkBack Thread Tools Display Modes
Old   July 11, 2013, 12:07
Default
  #21
New Member
 
sina
Join Date: Jul 2013
Posts: 11
Rep Power: 5
aghsin is on a distinguished road
Hi Glenn
I read in one of your previous post that running a serious Steady State simulation to find a rotational speed of rotor is the easiest approach. I wanna know if I run a series of steady state simulation with different rotor rpm, how I can get conclusion about the real rpm of rotor from the graph rpm vs torque?
aghsin is offline   Reply With Quote

Old   July 13, 2013, 06:59
Default
  #22
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,832
Rep Power: 100
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
It is a simple thing then to integrate through time the rpm versus torque curve to model the rotor speed versus time. The maths to do this is straight forward and should be easily done in Excel, matlab, python or whatever you like to do basic numerical work in.
ghorrocks is offline   Reply With Quote

Old   July 17, 2013, 19:48
Default
  #23
New Member
 
sina
Join Date: Jul 2013
Posts: 11
Rep Power: 5
aghsin is on a distinguished road
Glenn,
thank you for your reply. you said somewhere that extrapolating to find a net zero torque in torque vs rpm curve will give us the actual rotating speed. would you please let me know the concept behind this?
aghsin is offline   Reply With Quote

Old   July 18, 2013, 08:58
Default
  #24
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,832
Rep Power: 100
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
Basic mechanics - if the rotor has zero torque then it runs at constant speed. So find the point where the fluid power equals the absorbed power and you have your steady state operating point.
ghorrocks is offline   Reply With Quote

Old   July 19, 2013, 20:58
Default
  #25
New Member
 
sina
Join Date: Jul 2013
Posts: 11
Rep Power: 5
aghsin is on a distinguished road
Glenn,
Thank you for your help. I performed a simulation of axial turbine from start up based on Rigid body approach and I got almost the same result compared your suggestion (series of steady state simulation). I got almost the same rotational speed of rotor in both approach. In both case the torque got zero when the rotor get a steady rotation, I was wounder how I can calculate a power output based on the equation P=TW, now? Because torque=0.
aghsin is offline   Reply With Quote

Old   July 20, 2013, 06:06
Default
  #26
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,832
Rep Power: 100
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
If the rotor is just freewheeling around then there is no output power. But if the power/torque is being absorbed in the generator (or whatever is absorbing the power) then you just get the power straight from that.
ghorrocks is offline   Reply With Quote

Old   February 24, 2016, 04:50
Default
  #27
siw
Senior Member
 
Stuart
Join Date: Jul 2009
Location: Portsmouth, England
Posts: 488
Rep Power: 15
siw will become famous soon enough
Glenn,

How would you apply the steady-state approach if the rotating blades are obscured over some regions of the rotation, e.g. the attached image of a simple example (I've removed a lot of the geometry for clarity)? Here steady-state simulations would be needed at different angles.

I too want to simulate the blades spinning up from rest due to the freestream velocity.

Thanks
Attached Images
File Type: jpg Obscured Blades.JPG (50.6 KB, 16 views)

Last edited by siw; February 24, 2016 at 05:58.
siw is offline   Reply With Quote

Old   February 24, 2016, 06:07
Default
  #28
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,832
Rep Power: 100
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
Nothing is attached. But no matter, I think I understand your question.

If you want to use the frozen rotor approach but have a configuration where there will be torque variations depending on rotor angle, then you need to do enough frozen rotor simulations at enough angles so you know the torque versus angle curve well enough that you can determine an average power.
ghorrocks is offline   Reply With Quote

Old   February 24, 2016, 07:46
Default
  #29
siw
Senior Member
 
Stuart
Join Date: Jul 2009
Location: Portsmouth, England
Posts: 488
Rep Power: 15
siw will become famous soon enough
Glenn,

Updated the post with the image.
siw is offline   Reply With Quote

Old   March 17, 2016, 07:56
Default
  #30
New Member
 
Héctor Lodoso
Join Date: Oct 2015
Posts: 5
Rep Power: 3
Héctor Lodoso is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
Far easier, but a little less elegant is to sweep through a range of rotation speeds in a series of steady state runs. This will give you a torque/power versus speed curve. Then interpolate on this curve your intended torque/power and there you have it. If you like then run this point as well to improve the accuracy of the interpolation.
Hello Mr. Horrocks,

What do you exactly mean with the quoted sentence?
I do not understand the concept "steady state runs" when you talk at the same time of "rotation speed" of the rotor. Is the rotor actually moving (rotating) in a transient simulation? Or do you mean to compute the rotation speed throug the inlet wind velocity? ....
Héctor Lodoso is offline   Reply With Quote

Old   March 17, 2016, 21:28
Default
  #31
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,832
Rep Power: 100
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
By steady state runs I mean use frozen rotor or one of those simplified rotating frames of reference models which accounts for the frame rotation inside a steady state simulation.
ghorrocks is offline   Reply With Quote

Old   March 18, 2016, 04:14
Default
  #32
New Member
 
Héctor Lodoso
Join Date: Oct 2015
Posts: 5
Rep Power: 3
Héctor Lodoso is on a distinguished road
Quote:
Originally Posted by ghorrocks View Post
By steady state runs I mean use frozen rotor or one of those simplified rotating frames of reference models which accounts for the frame rotation inside a steady state simulation.
Thank you for your reply.

Then I understand it is a sweep of pure steady state simulations or with the use moving reference frames. But then, how could I take into account the rotation speed of the rotor in a pure steady state run?

Please excuse my ignorance.
Héctor Lodoso is offline   Reply With Quote

Old   March 18, 2016, 20:34
Default
  #33
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,832
Rep Power: 100
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
If the simulation is purely steady state with no rotating frames of reference then you can't account for the rotation. It is the rotating frame of reference model which accounts for the rotation.
ghorrocks is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
please help in simulating a wind turbine blade in 6 DOF ????.... usman naseer Main CFD Forum 2 March 10, 2016 03:53
Ducted wind turbine (BC for the shroud) Pepita CFX 4 June 29, 2013 07:09
3D wind turbine modelling/boundary condition defn in rotation bakay FLUENT 9 September 14, 2011 05:32
Wind turbine simulation Saturn FLUENT 1 June 16, 2006 02:12
Wind turbine simulation Saturn Main CFD Forum 1 June 12, 2006 03:57


All times are GMT -4. The time now is 10:59.