[DAWTson]

Hi,

I'm rather new to Star CCM+, and currently trying to efficiently try design-iterations of a diffuser for a DAWT. Hence, I'd like to run my simulations axisymmetrically. I want to prescribe a volumetric force, like the virtual disc, but I dont know how to accomplish this.

From the manual (and general google search) I gather that:

1) It has to be assigned from "Physica values" under Regions.

2) I have to create a table or Field Function to define the position/span of the source.

I am not familiar with the syntax of field functions however, and my search in the threads in here has lead me anywhere useful so far.
Any suggestions on how to accomplish this easily?
I'd like to prescribe the force to a line from e.g. [0,0,0] to [0,1,0]

Thanks a lot!

[cwl]

I'd like to prescribe the force to a line from e.g. [0,0,0] to [0,1,0]

($$Position[1] >= 0) && (Position[1] <= 1)
?
  <your value>
:
  0

In here $$Position[1] is the y-coordinate (x is $$Position[0], z is $$Position[2]).
That would apply force everywhere in 0.0 ≤ y ≤ 1.0.

But - force cannot be applied at "line" it should be applied in some volume, so depending on your task approach - you'll have to add some extra coordinate conditions (into the first line of the field function) so that your field function would be appied only in the chosen volume.

[DAWTson]

Thank you for your reply cwl.

Would this mean I should apply it on an area, which would then become a volume once the axisymmetric condition is enforced?

[DAWTson]

So, I have written the code in the attached picture in a scalar field function.
It previews nicely, so I am assuming nothing is wrong with the code itself.
However, the field function does not appear when selecting my function in the momentum source option. When looking under the field functions section, I see that it is crossed out - do I need to somehow publicize it, or is this a symbol of some error? This is also shown in attached picture.

[cwl]

I'd suggest you read about field functions in the STAR-CCM+ user guide, it is somewhere around page 454 (depending on the version).

[DAWTson]

I found the reason.
For anyone who may need this: The force needs to be assigned to an area if you are using an axisymmetric analysis, and be a vector.
I made it work with he following:

[$$Position[1] >= 0 && $$Position[0] >= -0.05 && $$Position [1] <= 0.56 && $$Position[0] <= 0.05 ? 260 : 0, 0, 0]
| | |
|
from y coord > 0 from x coord > -0.05 to y coord < 0.056 to x coord < 0.05 assign 260 N/m3

and with a 0 component in y and z direction.

Hope this may help someone.

[cwl]

Good job DAWTson!

Also - thank you for sharing your solution, I'm pretty sure someone would find it helpful