[Anonymized_JL1]

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)?

[-mAx-]

in Fluent you can compute moments (torque)
Report/Forces... choose Moments instead of Forces.

[Anonymized_JL1]

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

[-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

[Boon]

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 ?

[desert_1250]

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;
patches (Blade1);
PName p;
Uname U;
log true;
rhoInf 1.2;
CofR (0 0 0);



______
Rasoul

[-mAx-]

adapt CofR (0 0 0) coordinates.
They are needed for torque computation

[desert_1250]

How to adapt CofR (0 0 0)? i set it at center of rotating object

[desert_1250]

How to adapt CofR (0 0 0)? i set it at center of rotating object

_____
Rasoul

[-mAx-]

It should be the a point on your rotation axis

[desert_1250]

would you mind to seee this froum(from post 8):
http://www.cfd-online.com/Forums/ope...tml#post322023
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

[-mAx-]

do you think or are you sure?
If you go back to your mesher, check if (0 0 0) belong to your rotation axis.

[desert_1250]

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

[-mAx-]

check if pressure distribution on blades are the same on 2d and 3d

[mikebausas]

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..