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

Wind Turbine DFBI

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

Reply
 
LinkBack Thread Tools Display Modes
Old   April 15, 2013, 21:51
Default Wind Turbine DFBI
  #1
New Member
 
BKaiser
Join Date: Sep 2012
Posts: 4
Rep Power: 3
BKaiser is on a distinguished road
Hello,

I am attempting to model a rotating wind turbine using the dynamic fluid body interaction (DFBI) solver in STAR CCM+. I've constrained the turbine (floating in the center of the control volume, no tower) to rotate about the axis it would in reality, set an initial rotational velocity, moments of inertia, ramp time, release time, etc. I have one region, with many surfaces, and DFBI turned on. My DFBI body is the turbine, which is also it's own surface within the region.

For some reason, the turbine surface still expects a specified rotation rate, even though I already specified an initial one in my DFBI body. Near the end of ramp time, the rotation was faster than the specified initial rotation, and the solver seemed to disregard the specified rotation rate for the surface. Did I do the simulation correctly, and if so, why does it ask for a specified rotation rate for the surface which it seems to not use?

Also, I had pictures out put from each time step and STAR appears to be rotating my entire mesh, not just the turbine. STAR crashes when I try to see the geometry, scalar, or mesh scenes.

Thanks in advance! I apologize for the long question.
BKaiser is offline   Reply With Quote

Old   April 16, 2013, 10:20
Default
  #2
Member
 
Ryan Coe
Join Date: Jun 2010
Location: Albuquerque, NM
Posts: 98
Rep Power: 6
ryancoe is on a distinguished road
How are you achieving the rotation of the turbine blades? Are the blades located within their own cylindrical embedded region?
__________________
Ryan
ryancoe is offline   Reply With Quote

Old   April 17, 2013, 20:46
Default
  #3
New Member
 
BKaiser
Join Date: Sep 2012
Posts: 4
Rep Power: 3
BKaiser is on a distinguished road
Hi Ryan,

No, I just set the initial rotation for that part only, assuming that the way STAR works in this case is to treat the rotation like a boundary condition...but it seems like that is not correct.

Do I need to embed the turbine in a separate mesh?

Thanks!

-Bryan
BKaiser is offline   Reply With Quote

Old   April 17, 2013, 21:21
Default
  #4
Member
 
Ryan Coe
Join Date: Jun 2010
Location: Albuquerque, NM
Posts: 98
Rep Power: 6
ryancoe is on a distinguished road
From what I can tell from your description of the simulation you want to run, yes you do need to have a separate region for the turbine blade. This allows the blade to rotate and the rest of the domain to remain inertially fixed.
__________________
Ryan
ryancoe is offline   Reply With Quote

Old   April 19, 2013, 14:19
Default
  #5
New Member
 
BKaiser
Join Date: Sep 2012
Posts: 4
Rep Power: 3
BKaiser is on a distinguished road
Thanks Ryan! I will go back to the demos for that then.

I've been looking at the moving reference frame approach, and STAR says it's "not suitable for resolving flow structures, e.g. wake coming off rotating machinery"... do you recommend another method in STAR for wakes coming off rotating machinery?
BKaiser is offline   Reply With Quote

Old   April 19, 2013, 15:20
Default
  #6
Senior Member
 
Join Date: Mar 2009
Location: Austin, TX
Posts: 127
Rep Power: 8
kyle is on a distinguished road
You need to use sliding mesh.

Also, you need to start with a simpler simulation. Do not start with the monster DFBI simulation. Start with a steady-state rotating reference frame simulation, then use that result as the initial conditions for a transient sliding mesh simulation and experiment to find a suitable mesh size and time step. Only then should you even be thinking about enabling DFBI.
kyle is offline   Reply With Quote

Old   April 19, 2013, 15:38
Default
  #7
New Member
 
BKaiser
Join Date: Sep 2012
Posts: 4
Rep Power: 3
BKaiser is on a distinguished road
Hi Kyle,

Thanks, yes I just went over the MRF demo, and will run some basic simulations before progressing up to DFBI.

Do you know what degree of accuracy STAR's RANS models are capable of for predicting wake flow structure? I'm wondering if there is information regarding what I can expect when I get there.

Thanks,

-Bryan
BKaiser is offline   Reply With Quote

Old   April 19, 2013, 15:49
Default
  #8
Senior Member
 
Join Date: Mar 2009
Location: Austin, TX
Posts: 127
Rep Power: 8
kyle is on a distinguished road
It really depends on your geometry and your goals. If you are simulating a turbine with 2 or 3 blades, then no steady-state simulation is going to even come close to resolving the wake accurately. If your geometry is a windmill with 50+ blades then a simple steady-state RANS MRF simulation might actually do a reasonably good job.

This has nothing to do with STAR's capabilities, it just can't calculate things that you don't ask it to calculate. Moving reference frame simulations will always be less accurate than sliding mesh because MRF can only calculate for a single physical position of the moving geometry. Sometimes it's close enough, sometimes it isn't.

Last edited by kyle; April 19, 2013 at 17:21.
kyle is offline   Reply With Quote

Old   August 1, 2013, 20:47
Default
  #9
New Member
 
malu
Join Date: Jun 2013
Posts: 8
Rep Power: 3
malfrienz is on a distinguished road
is there any limitation using the rotating mesh and eulerian multiphase models simultaneously??
I'm modelling a rotating blade over which gas-liquid mixture flows. Once i turn on the rotation, the AMG solver diverges.
Thanks.
malfrienz is offline   Reply With Quote

Reply

Tags
boundaries condition, dfbi, fsi, rotation, star ccm+

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
Ducted wind turbine (BC for the shroud) Pepita CFX 4 June 29, 2013 07:09
Moving reference frame in wind turbine kongl1986 FLUENT 0 March 30, 2013 11:50
Vertical Axis Wind Turbine atorninc Main CFD Forum 3 March 6, 2013 04:38
FSI - Wind Turbine AUN CFX 13 August 29, 2012 16:44
Wind turbine simulation Saturn FLUENT 1 June 16, 2006 02:12


All times are GMT -4. The time now is 12:42.