Learning Forum

[l.hutcheson1]

I’m trying to simulate a hybrid Darrieus VAWT and I’m coming across a unusual issue:

It seems that the edge of the rotor area is being defined as the inlet instead of the inlet itself (Image 1), despite the simulation being set up identically to another working simulation with slightly different dimensions. My suspicion is that this stems from the creation of new contact regions under boundary conditions which are present in this model (Image 2), but not the other working model. These also appear under “Mesh Interfaces” leading me to believe this is what is stopping the mesh from sliding. In the working model, it is only “blades” and the lines which make up the wall region each being named “wall XX” (Image 3) that are under the Wall heading here, otherwise all setup parameters are the same between models.

 

The issue also seems entirely related to the angular rotation of the rotor, since varying the inlet velocity has no effect on the simulation. I've tried to create the entire system again, but it leads to the same result. the simulation is in 2D and large structure support is enabled. 

 

Thanks for your help.

[Rob]

The surface (interface) pair between the two zones needs setting up. It looks like you currently have a pair of walls. 

[l.hutcheson1]

Any idea on how I should set this up? 

[Rob]

Yes, have a look at the interface functions in Fluent's User Guide. They're covered in Boundary Conditions. 

[l.hutcheson1]

Hi Rob,

Thanks for your help so far, I've managed to run the simulations and the contours look as expected, however, the output torque is much less than expected by a factor of nearly 10^4. Any ideas on what could be causing this? 

[Rob]

Check the domain scale? I assume you've set the centre point? Also, are you moving the VAWT using moving mesh at a fixed speed or based on the force/flow speed? 

[l.hutcheson1]

I've double checked the domain scale and moment co-ordinates and they're correct. The movement is based on inlet velocity in boundary conditions and a rotational velcoity for the rotor in cell zones conditions.