[mohammad]

Hi everybody
I am doing a CFD simulation of a 2 bladed wind turbine under wind shear profile condition when the wind speed changes according to a logarithmic wind profile. The wind turbine is standstill ( not rotating) and I want to model a single blade at the zero azimuth angle ( = blades are supposed to be vertical).

The question is:
How should I simulate the B.C on the geometrical plane of symmetry?
What is the B.C? From the first moment it is clear that "Symmetric" boundary condition is not true because the wind speed distribution on the two sides of this plate are not the same.

I was thinking to use a domain and put a single blade somewhere in the domain. in this new model the domain is stretched out of both sides of the blade ( form the root and the tip).Therefore I can apply the wind profile to the domain and this wind profile contains some part of the wind profile just before the blade's root. ( SEE THE ATTACHMENT )

This new idea can simulate some effects of wind shear profile near the blade's root; however, because the other blade does not exist here the wind simulation is still not exact in the sense that the wind before the blade's root is not affected by the other blade.


Can anybody please help me to clarify which B.C should I use?

Regards,

[ghorrocks]

How should I simulate the B.C on the geometrical plane of symmetry?

It is not clear what you are modelling. If this is modelling the blade when stationary then apply a tangential velocity equal to the velocity at your boundary.

[mohammad]

Dear Glenn

Originally Posted by ghorrocks

It is not clear what you are modelling.

because I am going to simulate half model( one blade only) , I am asking about the B.C. of the plane of geometrical symmetry which passes through the hub and divides the wind turbine to two geometrically similar blades.

Originally Posted by ghorrocks

If this is modelling the blade when stationary then apply a tangential velocity equal to the velocity at your boundary.

According to your idea, if i apply this condition, still i am removing the effects( shear effects) of the removed part of model ( the other blade) which is not simulated in my simulation.

my question is that is there any way to simulate the effects of the wind shear ( friction and shear forces,....) on that plane?
Regards,

[ghorrocks]

Why not model this using the rotating frames of reference? Then you can do a model with the difficulty of a steady state simulation, but include the effects of blade rotation. Much more accurate and easier. Also you do not have the weird bottom boundary to worry about.

[mohammad]

Originally Posted by ghorrocks

Why not model this using the rotating frames of reference?

I am doing the standstill analysis....How can I use the rotary frame for a stationary case!!!???

[mohammad]

Hi everybody!!!!

Any help???!!!

[ghorrocks]

is there any way to simulate the effects of the wind shear ( friction and shear forces,....) on that plane?

Yes, as I said before just apply a tangential velocity to the plane equal to the boundary layer velocity at that height.

[mohammad]

Originally Posted by mohammad

Hi everybody
I am doing a CFD simulation of a 2 bladed wind turbine under wind shear profile condition when the wind speed changes according to a logarithmic wind profile. The wind turbine is standstill ( not rotating) ...........................................

Regards,

Dear all,
I have made the model and applied the velocity profile ,as mentioned by Glenn Horrocks.

However I cannot get a stable results.
I have tried many differnt timesteps.....also I switched to the Transient simulation . But, all of my attemps failed.

Do you have any idea? how should I get the results....

Thanks,

[ghorrocks]

http://www.cfd-online.com/Wiki/Ansys...gence_criteria