[caohan]

Hi All,
I am a newbie of CFD simulation, now I am doing a wind turbine simulation.The tested wind turbine is 20 kw, untwisted rotor sized at a diameter of 10.1m and constant chord length is 0.458m, wind speed is 10m/s, during this situation, the roatational speed is assumed as 72 rpm.Viscous model is standard k-e, MRF and sliding mesh both were used in my model.
here are the velocity and pressure contours by using MRF. The pics looks normal, but the moment is too big when I export the report.
this is the pressure moment
(-70.524025 -54.304947 18263.371)
this is the viscous moment
(-0.73487449 3.8853738 59.417488)
this is the total moment
(-71.258899 -50.419573 18322.789)
because the rotational axis is z-axis, so someone tell me I should only focus on the moment on z-direction which is 18322.789. is it correct? if it is, by using this value, the output power is 138.15 kw. this is unbelievable, because the actual wind turbine only has 20 kw output power. does somebody has the same problem with me. really hope someone can help me get through it!!

Han

[esp-m1000]

It looks like we have the same problem....hope someone will explain what's wrong.
I suggest u to visit

http://www.cfd-online.com/Forums/flu...on-vawt-4.html

There in last post i write i said how i have done the simulation.
Maybe we have some error in common.

[caohan]

Originally Posted by esp-m1000

It looks like we have the same problem....hope someone will explain what's wrong.
I suggest u to visit

http://www.cfd-online.com/Forums/flu...on-vawt-4.html

There in last post i write i said how i have done the simulation.
Maybe we have some error in common.

Hi esp-m1000,
Thank you for your reply, maybe we can work together to find out what kind of issue will cause such a big error. are you using MRF or sliding mesh to simulate you model? I try both two ways and result make me disappointed. by the way, how can you calculate the moment in Fluent, did you export the moment from report?
Han

[esp-m1000]

I'm using sliding mesh, and to calculate the moment i export the moment from report.
I monitor the Cm of the turbine in:
solve -> monitors -> force: options: print, plot and write
wall zones: turbine
coefficient: moment
moment center (0,0,0)
I don't know what's wrong.....

[aalisha]

Hello Caohan and esp-m1000,

have you find the error? I am also doing something similar on vertical axis tidal turbine. and can you please help me to find the torque using Cm..

[amin_veysi]

hi you must change the reference value, in this case you must change area from 1 to sweep area, length from 1 to radius of blade and velocity from one to hub velocity

[UmeProIITG]

hi all, I am also facing same kind of problem. Even I changed the reference value of the area 1m^2 to swept area and length was also changed from 1m to radius of the rotor. By the way I do not understand what do you mean by hub velocity @ amin_veysi.

[UmeProIITG]

@ amin_veysi how many cell zone will appear if we use sliding mesh condition? In our case it is 2. Is it correct?

[aalisha]

Hey amin,

Actually even after changing the reference values, I was not sure about the value power of co-efficient by using co-efficient of moment. However, now I am using Cp= Cm X Tip speed ratio.