CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

High torque coefficient Cm for Vertical Axis Wind Turbine (VAWT)

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

Like Tree1Likes
  • 1 Post By tony00

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 28, 2010, 08:33
Default High torque coefficient Cm for Vertical Axis Wind Turbine (VAWT)
  #1
New Member
 
Join Date: Nov 2009
Posts: 22
Rep Power: 17
tony00 is on a distinguished road
Hello,
I am modelling the 2D vertical axis wind turbine (VAWT). The turbulence model is k-epsilon with std wall function. I simulate 4 angular velocities: 5, 10, 15 and 20 rad/s. Wind velocity is 11 m/s. Model is using U-RANS with sliding mesh.
Problem is that I obtain excessively high torque calculated from the Cm (4 to 5 times larger than it should be). Cm is obtained from Fluent, torque calculated with the Cm definition(Cm=T/(0.5 x rho x v^2 x A x R).
Time step: tried both time steps corresponding to 1 degree and 1/8th degree. Results perfectly match so the 1deg step is fine enough.
I would be very grateful to the one who can spot if and/or where I am making a mistake and can contribute to making this simulation happen the best way.

Thanks
All the best
TonyMac
gaist likes this.

Last edited by tony00; March 17, 2010 at 06:25. Reason: wrote seconds instead of degrees to define the angular step increment
tony00 is offline   Reply With Quote

Old   March 16, 2010, 17:34
Default
  #2
Member
 
benoit paillard
Join Date: Mar 2010
Posts: 96
Rep Power: 16
bennn is on a distinguished road
that might sound - and actually be - silly but check that you actually divided the torque by the appropriate value, to get a reduced coefficient instead of a Nm torque. That happened here not too long ago.
bennn is online now   Reply With Quote

Old   March 19, 2010, 09:26
Default
  #3
New Member
 
Join Date: Nov 2009
Posts: 22
Rep Power: 17
tony00 is on a distinguished road
Hello Benoit,
all solved and getting pretty good results now. As you suggested it was indeed a problem with the constants entered in report-> reference values.
Thanks
Tony
tony00 is offline   Reply With Quote

Old   March 22, 2010, 23:43
Default Change fluent reference values
  #4
Member
 
Haris Hameed
Join Date: Oct 2009
Posts: 48
Rep Power: 17
harishameed33 is on a distinguished road
Change fluent reference values

compute velocity form inlet
and change reference area to swept area
your cm will change
hope this work
harishameed33 is offline   Reply With Quote

Old   April 1, 2010, 01:59
Default
  #5
New Member
 
SHIVA
Join Date: Feb 2010
Posts: 7
Rep Power: 16
skshivas is on a distinguished road
Quote:
Originally Posted by tony00 View Post
Hello,
I am modelling the 2D vertical axis wind turbine (VAWT). The turbulence model is k-epsilon with std wall function. I simulate 4 angular velocities: 5, 10, 15 and 20 rad/s. Wind velocity is 11 m/s. Model is using U-RANS with sliding mesh.
Problem is that I obtain excessively high torque calculated from the Cm (4 to 5 times larger than it should be). Cm is obtained from Fluent, torque calculated with the Cm definition(Cm=T/(0.5 x rho x v^2 x A x R).
Time step: tried both time steps corresponding to 1 degree and 1/8th degree. Results perfectly match so the 1deg step is fine enough.
I would be very grateful to the one who can spot if and/or where I am making a mistake and can contribute to making this simulation happen the best way.

Thanks
All the best
TonyMac
Dear Tony,

I m also facing the same problem. still i m not able to reasolve the fluent case. please give some idea to predict the Torgue and Co efficient of the performance (Cp) of the wind Turbine.

With Regards

S.SIVAKUMAR
skshivas is offline   Reply With Quote

Old   June 11, 2010, 06:15
Default
  #6
New Member
 
Join Date: Jan 2010
Posts: 28
Rep Power: 16
esp-m1000 is on a distinguished road
Hi tony, maybe I'm affected by the same problem you solved.
I hope you will share with me your solution.

Thanks
esp-m1000 is offline   Reply With Quote

Old   February 21, 2014, 01:07
Default Doubt
  #7
New Member
 
dynamic
Join Date: Oct 2013
Posts: 3
Rep Power: 13
Poojitha is on a distinguished road
In the Cm definition, what is A(area)?
Poojitha is offline   Reply With Quote

Old   March 25, 2014, 02:56
Default
  #8
New Member
 
behzad shahizare
Join Date: Feb 2014
Location: malaysia
Posts: 5
Rep Power: 12
shahizare is on a distinguished road
Send a message via Skype™ to shahizare
Quote:
Originally Posted by harishameed33 View Post
Change fluent reference values

compute velocity form inlet
and change reference area to swept area
your cm will change
hope this work
what is the swept area in 2D model for vawt ?
shahizare is offline   Reply With Quote

Old   June 2, 2014, 03:25
Default high value of Cm
  #9
New Member
 
Aalisha
Join Date: Jan 2014
Posts: 18
Rep Power: 12
aalisha is on a distinguished road
Quote:
Originally Posted by skshivas View Post
Dear Tony,

I m also facing the same problem. still i m not able to reasolve the fluent case. please give some idea to predict the Torgue and Co efficient of the performance (Cp) of the wind Turbine.

With Regards

S.SIVAKUMAR
Hey I am also facing the same problem. I am trying to change the values for the references. IF you can share how you have solved this problem? Thanks.

-Aalisha
aalisha is offline   Reply With Quote

Old   January 9, 2015, 23:27
Default
  #10
New Member
 
Join Date: Jan 2015
Posts: 1
Rep Power: 0
mshaheen is on a distinguished road
For a 2D case should I take the area = 1, and in this case what should be the depth.
mshaheen is offline   Reply With Quote

Old   March 27, 2017, 02:51
Default CM coefficient
  #11
New Member
 
nima seyfi
Join Date: Feb 2017
Posts: 3
Rep Power: 9
nima2472 is on a distinguished road
hi
can anybody help me please
what is A and L in equation of CM blow:
cm=M/0.5*RHO*U^2*A*I
my case is a vertical axis wind turbine
archimedes spiral wind turbine blade
nima2472 is offline   Reply With Quote

Old   July 23, 2018, 07:13
Default
  #12
New Member
 
UTTAR PRADESH
Join Date: Jul 2018
Posts: 1
Rep Power: 0
danakalu is on a distinguished road
Quote:
Originally Posted by tony00 View Post
Hello Benoit,
all solved and getting pretty good results now. As you suggested it was indeed a problem with the constants entered in report-> reference values.
Thanks
Tony
can you please tell me the reference value that you have used.
danakalu is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
VAWT Wind Turbine Tom Smith FLUENT 11 August 27, 2011 02:38
my VAWT Darreius coefficient of performance high above Betz efficiency radix FLUENT 0 August 27, 2009 01:51
Moment coefficient of vertical axis wind rotor Agni Main CFD Forum 0 August 28, 2008 07:07
help to find torque of a wind turbine using fluent athiyaman.p FLUENT 1 March 10, 2006 11:49
Multicomponent fluid Andrea CFX 2 October 11, 2004 06:12


All times are GMT -4. The time now is 17:55.