[Chris_321]

Hello everybody,

is someone around who can tell me what is the easiest way to get the right coordinates for the rotating axe?

I created a point at the middle of the fan surface in Icem and took the coordinates but the problem is that CFX and CFDPost use a different coordinatesystem in my model.

At the moment i create a point in CFD Post and change his coordinates until it match the rorating axe but im shure there is an easier and automatic way like the "create point in the middle of a circle" feature in CAD software.

How is it possible to get the right coordinates in CFX or in CFD Post in a easier way?

[Chris_321]

One Minute after writing this post i solved it by myself, i just need to calculate the coordinates with (Icem Coordinate)/1000 = ( CFX Coordinate)

I think its because of the dimension units?


This thread can be closed

[ghorrocks]

I also see your blades have some thickness. This will make convergence difficult (as it will shed vorticies) and should be avoided if possible.

[Chris_321]

Hi ghorrocks,

thank you for that information!

If i delete some of the surfaces and mesh the others, how can i use them in cfx?

[Chris_321]

If i do it this way CFX dont even find the surfaces anymore, any advise?

[ghorrocks]

If the actual geometry you are modelling has bluff faces like this then you have to model it - just be aware that it will make things hard.

But if you want to make the simulation easier and can modify the geometry then you have two options:
1) Model the blade as a thin surface
2) put a blunt leading edge and a sharp trailing edge on the blade, to make it into an airfoil shape. If the leading edge is too sharp it will separate and will be difficult again.

[Chris_321]

Hi,

do you have a tutorial or something where i can see how this is done in Icem?
I have a little bit trouble with the meshing of those surfaces.

[ghorrocks]

Have a look at ICEM and the ANSYS community site for tutorials.

If you are looking at thin surfaces this is well described in the documentation.

If you are changing the shape to an airfoil shape then this is a geometry modelling operation and there are lots of tutorials on the community site describing this. Or you can do it on whatever solid modelling package you use the generate the geometry in the first place.

[Chris_321]

I remeshed everything and i think the mesh looks pretty well. The Error message is still there so i followed the steps that the solver told me.

1. Rotating Axis ( Should be good!)
2. Meshing ( Very Fine)
3. Tolerance change ( from 10 up to 30)


Nothing works for me :/

can someone help me?

[ghorrocks]

What error message?

Please post an image of what you are modelling and your mesh. Also include your CCL please.

[Chris_321]

I will try to explain step by step:

First i tried to simulate an oven with a ventilator inside, but i think thats to mutch for the start.


So i changed my simulation and first I will simulate a ventilator driven flow.

The softwares i can use are ICEM, Fluent,CFX, CFD Post

Meshing:









CFX- Pre:

Composide Region "vanes" for the thin surfaces:



Why is there two "Ventilator" surfaces? I specified ventilator as a part of some surfaces in ICEM, shouldnt it be just one part in CFX aswell? Or is it because of the two sides of the surfaces? Do i have to do two composide regions?


Boundarys:


I added the rotating wall to the region "vanes" i specified before.



If i ran the solver i get this error message:

+--------------------------------------------------------------------+
| ERROR #002100080 has occurred in subroutine CHECK_NORMV. |
| Message: |
| The specified velocity vector on the boundary patch |
| |
| Vane |
| |
| has a significant normal component at one or more faces. One of |
| these face locations is |
| |
| (x,y,z) = ( 1.66769E-01,-1.42672E-01, 1.33330E-02). |
| |
| The angle between the specified velocity and the element surface is|
| 42.918 degrees at this face. This is considered an error because |
| it implies that the mesh is moving. The following are possible |
| reasons for the error message: |
| 1. There is a setup error; for example, an incorrect axis of |
| rotation. |
| 2. There may be a meshing problem; for example, the nodes on a |
| rotating surface might not lie on the surface of revolution. |
| 3. The boundary is curved and the mesh is very coarse. In this |
| case, you may modify the tolerance by increasing the |
| expert parameter 'tangential vector tolerance wall' |
| from its default of 20 degrees. |
+--------------------------------------------------------------------+

The location the solver says is located here

[ghorrocks]

You appear to be modelling a fan with a stationary mesh but specifying a velocity on the fans wall boundary. This is not the correct way of doing this. You should put the fan in a rotating frame of reference instead. Have a look at the CFX tutorials for how to set up rotating frame of reference simulations.

[Chris_321]

Thank you ghorrocks!

One Thing and i leave you alone


Is there a way to add the thin surfaces to a rotating domain?

Because all i have in my domain is the thing in the middle not the thin surfaces

[ghorrocks]

If you are not modelling heat transfer in the rotor then you do not model the rotor as a solid. If the rotating domain includes thin surfaces then they will rotate as well. Nothing special is required to make thin surfaces rotate.

You really should have a look at the CFX tutorials on how to set up rotating machinery simulations.

[Chris_321]

I already took a look at it but im still wondering on how it works in my chase.

As far as i understand the right approch in this simulation is just one fluid domain with a rotating reference frame right?

But how would i do it if there are buffles or something like that?


I somehow dont understand why i cant just let the fluid domain stationary and just add a rotating frame to the ventilator ( If i get the thin surfaces finally to both domains....)

In the "oven" simulation - the simulation why i started this thread - i'm interessted in the heat transfer in the rotor.

I think after taken a deeper look for the tutorials i come close to my results

But now im fighting with this error ...

Details of error:-
----------------
Error detected by routine DELDAT
CDANAM = /FLOW/MESH/LATEST/ZN1 /CrdVx
ICOM,IRET,IERR 1025 2 1
CRESLT = ERR

Current Directory : /FLOW/PHYSICS/ZN1

+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| Stopped in routine MEMERR |
| |
| |
| |
| |
| |
+--------------------------------------------------------------------+

[ghorrocks]

If you are modelling heat transfer inside the rotor (I do not mean only at the surface, I mean you wan the temperature distribution inside the rotor) then you need to model the rotor as a solid. Note this can only be done in CFX V15 as previous versions did not easily support moving solid domains.

So it sound like in your case the oven is a stationary domain and the rotor fluid is in a rotating domain and the rotor solid is also in a rotating domain.

[haribhaskaran]

Hey Chrisitian

Were you able to get rid of the error message ? I am working on a very similar simulation and am seeing the same error message.

Thanks

Hari