Vertical Axis Wind Turbine (VAWT) simulation
 

I have done a steady state simulation of a vertical axis wind turbine. The solution has converged to a max residual of 1e-5 but i get an excessive torque value so I'm having my doubts on the physics setup.

The steps i have followed are:

1.- Draw the wind turbine blades
2.- Draw a cylinder around the blades (rotating fluid)
3.- Draw a large frustum around the blades
4.- Substract the cylinder from the frustum to obtain the outer volume shown in the image.
5.- Subtract the blades from the cylinder to obtain the inner volume shown in the image.

https://i.imgsafe.org/c5bbf6b055.png

* The cylinder containing the blades is set as a rotating domain with the design rotational speed of the turbine and Z rotation axis (turbine axis).
* The frustum is a stationary domain.

The boundary conditions i have used are:

- Inlet the left and lateral faces of the frustum, with a velocity component in the X axis (free stream of air).
- Outlet at the right face of the frustum.
- Interfaces between the frustum and cylinder common faces, with frozen rotor frame change
- Wall at the blades.

My questions are:
1.- Is the physics setup correct?

2.- The real torque in the turbine oscillates with time due to the angular rotation and different angles of attack. The torque obtained by CFX is the average over time?

3.- What is the physical effect of increasing the volume of the cylinder around the blades (with rotating fluid) ? It currently contains the blades tightly (cylinder height = 1.2x blade height)

Q1 - probably not. But you should do the first level of investigation yourself. Have a look in the post processor - do the streamlines look reasonable? Is the rotor rotating in the correct direction? Are you getting attached flow where you expect, and separations where you expect?

Q2 - If you modelled this as frozen rotor the torque returned is the instantaneous torque at this angle in the rotation.

Q3 - It should be no effect. If this has an effect it shows there is a problem in your setup.

jorge..how did you get an excessive torque value
 

i have followed same procedure which you have done.
i had make mesh in ICEM CFD 16.2 and run simulation in fluent 16.2 but i never got torque (moment) above 0.
i have give the rotating zone to frame motion and my aerofoils are stationary wall.
i have almost try all model like k-e (std and realizable), k-w(SST), S-A etc.

please any one give me some idea. why this is happening with me.:confused:

Try the fluent forum.

hi ghorrocks;
thanks for your reply.but i dont know whats this fluent forum?