# Torque calculation of 2D VAWT Wind Turbine

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September 19, 2010, 02:37
Torque calculation of 2D VAWT Wind Turbine
#1
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Join Date: Feb 2010
Posts: 24
Rep Power: 7
Hello Everyone,

I am working on my Thesis which is basically 2D CFD simulation of Vertical Axis Wind Turbine. I need to calculate the torque generated by a wind turbine in order to find Cp. In this regard I am running 2D simulation with sliding mesh technique and saving the case/data file after every 10 degrees of rotation hence I have 36 files for one complete revolution. Now I am reporting the value of forces in X and Y direction (Fx and Fy) from each case/data file for all 3 Blades. Then I calculate Torque on each blade using formula
T1 = - Fx1.RcosΘ - Fy1.R.sinΘ
T2 = -Fx2.Rcos(Θ+120) - Fy2.R.sin(Θ+120)
T3 = -Fx3.Rcos(Θ+240) - Fy3.R.sin(Θ+240)
Total Torque T = T1 + T2 + T3 (Total Torque “T” is calculated for every 10 degree of rotations)

Average Torque = Σ T/n (0-360 degrees) where n = 360/10 = 36
Please let me know if the method I am using is correct. I am confused about the sign convention of Torque equations. is there any other way to find out Torque and Cp(Coefficient of performance)?
Attached Images
 Velocity Contours.jpg (21.6 KB, 605 views) Zoomed in view of Rotor.PNG (30.2 KB, 641 views)

Last edited by jola; January 5, 2012 at 12:02.

 September 20, 2010, 01:15 #2 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 2,972 Rep Power: 30 in Fluent you can compute moments (torque) Report/Forces... choose Moments instead of Forces. __________________ In memory of my friend Hervé: CFD engineer & freerider

 September 20, 2010, 19:57 #3 New Member   Join Date: Feb 2010 Posts: 24 Rep Power: 7 Thanks for your reply. I tried to report the moment in fluent but its all negative. is it cuz my Turbine is rotating in counterclockwise direction? do I have to sum them all up to get the total torque (M= M1+M2+M3) for angle 0-360 degrees? Thanks

 September 21, 2010, 02:31 #4 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 2,972 Rep Power: 30 If you compute the moment you should give the right axis. if you set the angular velocity, you should give the right direction (axis-convention) And yes, if all your moment are computed on the same point, you can add them __________________ In memory of my friend Hervé: CFD engineer & freerider

 November 20, 2010, 11:06 Asking for help!! #5 New Member   Low Chee Boon Join Date: Nov 2010 Posts: 3 Rep Power: 6 Hi , friend ! im new for Fluent, i also want to get the data from VAWT after simulation. but i dont know how to build up 2D drawing in Fluent. Can you guide me how to build it up in fluent ?

August 27, 2011, 01:42
#6
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s.rasoul_varedi
Join Date: Feb 2010
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Quote:
 Originally Posted by -mAx- If you compute the moment you should give the right axis. if you set the angular velocity, you should give the right direction (axis-convention) And yes, if all your moment are computed on the same point, you can add them

Hi Max, how are you? i hope that you are well
i simulated 2d VAWT successfully with OF (ggi method) and get the good result for mummentum as expected.
after that i decide to simulate it in 3d Geometry. so i create the 3d geometry and Mesh in Gambit and import it to OF, every thing is ok and i stop the run after 50 rotation degrees. when i see contours of velocity or pressure, every things is ok, but when i extract the mummentum, the result is very bad!!!??? why this happen???
for calculate the forces and mummentum for every blade i added similar code in controlDict file :
forces_1
{
type forces;
functionObjectLibs ("libforces.so");
outputControl timeStep;
outputInterval 100;
PName p;
Uname U;
log true;
rhoInf 1.2;
CofR (0 0 0);

______
Rasoul

 August 29, 2011, 01:42 #7 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 2,972 Rep Power: 30 adapt CofR (0 0 0) coordinates. They are needed for torque computation __________________ In memory of my friend Hervé: CFD engineer & freerider

 August 29, 2011, 04:07 #8 Member   s.rasoul_varedi Join Date: Feb 2010 Posts: 82 Rep Power: 6 How to adapt CofR (0 0 0)? i set it at center of rotating object

 August 29, 2011, 04:08 #9 Member   s.rasoul_varedi Join Date: Feb 2010 Posts: 82 Rep Power: 6 How to adapt CofR (0 0 0)? i set it at center of rotating object _____ Rasoul

 August 29, 2011, 04:12 #10 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 2,972 Rep Power: 30 It should be the a point on your rotation axis __________________ In memory of my friend Hervé: CFD engineer & freerider

 August 29, 2011, 04:36 #11 Member   s.rasoul_varedi Join Date: Feb 2010 Posts: 82 Rep Power: 6 would you mind to seee this froum(from post 8): Wind driven rotation i set my result for 2D and 3D VAWT and case in it. i think that i chose the point on the rotation axis ______ Rasoul

 August 29, 2011, 04:47 #12 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 2,972 Rep Power: 30 do you think or are you sure? If you go back to your mesher, check if (0 0 0) belong to your rotation axis. __________________ In memory of my friend Hervé: CFD engineer & freerider

 August 29, 2011, 05:23 #13 Member   s.rasoul_varedi Join Date: Feb 2010 Posts: 82 Rep Power: 6 now i am surely chose the point at the center of axis. i check it witj mesher and paraview? did you see my result and pic that set in the mentianed froum in the last post? _______ Rasoul

 August 30, 2011, 04:48 #14 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 2,972 Rep Power: 30 check if pressure distribution on blades are the same on 2d and 3d __________________ In memory of my friend Hervé: CFD engineer & freerider

 September 26, 2013, 03:35 #15 New Member   Michael Bausas Join Date: May 2013 Posts: 10 Rep Power: 4 Anonymized_JL1, good day! I am also working on a three bladed VAWT for my thesis.. I am currently building my gemometry and mesh using ICEM CFD. I started with a 1/3 portion of the turbine and had generated its unstructured mesh.. Do u have any suggestion on how to go on with my meshing from this point? How shall I generate the other two parts and how to merge them into a whole rotor. Please help. Thanks in advance..

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