CFD Online Logo CFD Online URL
Home > Forums > CFX

Torque definition

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

LinkBack Thread Tools Display Modes
Old   December 18, 2007, 12:31
Default Torque definition
Posts: n/a
I am now using CFX 10.0 to evaluate the power coefficient for a vertical layout marine turbine. The turbine consists of three separated blades which are immersed in water and rotating in a constant speed. The whole computational domain is separated into two zones for ease of designating boundary condition: (1). Stationary outer zone. This outer zone almost covers the whole domain except the circular region occupied by the rotating blades. Inflow, outflow and symmetric boundary conditions are included in this region; (2). Rotating inner zone. It is this circular zone that includes the blades (no-slip wall boundary condition has been employed on the blades surface). On the interface, GGI scheme (by default) is used to synchronize the zones.

I used the "cel" expressions to obtain the torque value at the blades. What confusing me so much is that by looking at the transient curve the torque is sometime positive and will change to negative after a while. In my humble opinion, a "positive" torque means it helps the turbine running in the same direction as it rotate at that moment. Likewise, a "negative" torque means the overall effect of the fluid is retarding the rotating of the turbine, which is harmful. Am I right on this point? If not, is there anyone here who can help me on it? It is quite important for me to understand it.
  Reply With Quote

Old   December 18, 2007, 17:09
Default Re: Torque definition
Glenn Horrocks
Posts: n/a

The torque returned is referenced to a right hand coordinate system, the direction of rotation is not considered.

Glenn Horrocks
  Reply With Quote

Old   December 19, 2007, 07:47
Default Re: Torque definition
Posts: n/a
Hi, Glenn Could you please put it more clear? what is the exact meaning of "positive" or "negative" torque?

Thanks Yali
  Reply With Quote

Old   December 20, 2007, 18:03
Default Re: Torque definition
Glenn Horrocks
Posts: n/a
This is high school mechanics.

Glenn Horrocks
  Reply With Quote

Old   July 11, 2012, 12:49
New Member
Join Date: Apr 2012
Posts: 8
Rep Power: 7
heatdrive is on a distinguished road
i'm doing the simulation for vertical axis wind turbine using steady state and mrf function setting..
my torque from fluent result sometime positive and sometime negative..why is that happen? is there anything wrong with my simulation setup?
heatdrive is offline   Reply With Quote

Old   July 11, 2012, 18:19
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 13,876
Rep Power: 107
ghorrocks is a jewel in the roughghorrocks is a jewel in the roughghorrocks is a jewel in the rough
Either it is real or your simulation has a big error. Could be either.
ghorrocks is offline   Reply With Quote


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
Torque calculation of 2D VAWT Wind Turbine Anonymized_JL1 FLUENT 14 September 26, 2013 03:35
OpenFOAM static build on Cray XT5 asaijo OpenFOAM Installation 9 April 6, 2011 12:21
positive and negative torque forces Wei-Haur Lam CFX 0 March 19, 2008 08:45
Torque definition Yali CFX 2 January 7, 2008 04:13
about use macro to compute torque in TASCflow lancy CFX 0 June 10, 2003 06:19

All times are GMT -4. The time now is 18:03.