Hello, I am simulating a 3D VAWT in Fluent and the total Cm coefficient is 30 and checked out the research paper and this value is true..How can we calculate the power coefficient?
I think what you get from FLEUNT is the total moment coefficient (3 * Cm of each profile, if your turbine has three blades or 2*Cm if it is only two blades). but using this value to calculate the moment and then the power might be wrong.
What you have to do is to use the forces (fx, fy, fz) to calculate the moments about the three axes (x,y,z). Suppose the z-axis is the rotational axis then you can get simply the Moment as follows:
M = (fx . R)_blade1+(fx . R)_blade2+(fx . R)_blade3 (r is the turbine radius)