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nyatoto August 10, 2002 10:29

Pitched blade impeller
Hi All,

I am trying to model a pitched blade impeller with CF4.4 Build. How do I create the pitched blade if I want to employ a block structured mesh?

Please help?


Astrid August 11, 2002 16:31

Re: Pitched blade impeller
I am quite sure that someone has created a hex mesh for a Pitch blade impeller before. Ask the helpdesk as they might have one on the shelf for you.


nyatoto August 13, 2002 04:34

Re: Pitched blade impeller
Hi Astrid,

Thanks for the feed back. I am sending the querry to the help desk, but just before I do that,I need a little more advise. In CFX Build4.4 I get Quad4, and then the Isomesh and Paver as the default options. Where do I get this Hex?

Do you mean unstructured mesh in CFX4.4? My approach is to apply a block structured mesh. Secondly I can not use Paver because I have an UNMATCHED BOUNDARY!

Regards Nyatoto

Astrid August 13, 2002 17:23

Re: Pitched blade impeller
If you want to solve your case with CFX4, forget Paving as the paver will give you an unstructured mesh. CFX4 only accepts structured meshes.

The quad4 elements refer to recangulars, that are used to create a surface mesh.

In your case, the route to obtain a hex grid is 1) create an unmatched boundary on the solids and the surfaces that touch your sliding interface, 2) create a quad4-mesh on the surfaces of ALL solids (e.g. solid 1.1, 1.2, 1.3, .... , not on surface 1, 20, 25 ...), and than 3) hit the last button, again select all blocks and press apply to create a volume mesh (structured hex mesh).

Good luck. You may need that. Forgive me if I am wrong, but you do not sound like an experienced CFX4 Build user. If you don't have a lot of time, and don't need the models from CFX 4, I would advise you to use CFX 5.5.1.


nyatoto August 15, 2002 06:03

Re: Pitched blade impeller
Yes, Ia m a new user.

I am now contemplating using CFX5.5.1. My earlier fear (according to what i was told) was that CFX5 does not handle Multiphase system well. Is this correct? Would you recommend that I model a multiphase system with impeller, and other internals such as draft tube and sparger, using CFx5.5.1?

regards ochieng

nyatoto August 15, 2002 12:52

Re: Pitched blade impeller
Just a second thought, There is an obvious answer I have just seen; follow the on going discussion on CFX4 Vs CFX5:


Astrid August 16, 2002 02:13

Re: Pitched blade impeller
Unfortunately, I have no experience with mulitphase flow. Though, my colleage has experience in CFX 4. It took weeks to get it converged. CFX 5? We haven't had the time to find out well. We did one simple case and it seemed to work, although the grid was somewhat miserable.

If you have a very complicated vessel with a lot of internals, I would recommend CFX 5.5.1. If you want to be sure about multiphase, ask around (in this forum f.i.) or at the helpdesk.

If you want to stick to CFX 4, you might consider using CFX Hexa for the meshing. This package makes is easier to create structured meshes for complicated geometries.


nyatoto August 16, 2002 03:41

Re: Pitched blade impeller
thanks for the tips.

I will post another querry specific to the multiphase modelling, Using a Rushton turbine in a 2phase system, I could not get a convergence after 8 days (60,000 iterations).


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