# How to mesh this with blockMesh?

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June 22, 2012, 11:33
How to mesh this with blockMesh?
#1
Member

Alexander A
Join Date: Jun 2012
Posts: 53
Rep Power: 7
Hi,

I am beginner in OF and I want to carry out a CFD-analysis for a so called cyclogyro.

On the attached pics you can see a cfx mesh for the problem which I have found in the internet: On the first pic you can see a big cylinder with one small white cylinder in the center, which rotates with a certain speed and five small cylinders with an airfoil which rotate with the big cylinder (the blue ring) around the small white cylinder in the center and also do rotaing oscillation around its own small cylinder axis.

On the second pic you can see the small cylinder with an airfoil which does the oscillating rotation.

The inner white cylinder in the center and the oscillating airfoil are solid boddies.

How can you mesh this problem with blockMesh. I know how to do a cylinder but how to do a cylinder in another bigger cylinder like the pic shows?

And how can you do the solidBoddyMotions described? Which functions do you need for it?

Many thanks for your help in advance.

Regards A.A
Attached Images
 1.gif (60.2 KB, 66 views) 2.gif (54.6 KB, 45 views)

June 23, 2012, 07:25
#2
Senior Member

Roman Thiele
Join Date: Aug 2009
Location: London, UK
Posts: 368
Rep Power: 14
one way to decompose the domain is attached. blockMesh supports arc edges, therefore this should not be such a big problem. unfortunately I don't know how to do rotating domain, but I think there you should take a look at the MRF tutorials.
Attached Images
 1_mod.gif (60.0 KB, 46 views)
__________________
~roman

 June 25, 2012, 04:52 #3 Member   Alexander A Join Date: Jun 2012 Posts: 53 Rep Power: 7 Hi thanks for the quick reply. My next question is how can I put a vertex by giving the coordinates that it is positioned exactly on an arc, in order to have one exact face for two patches?

June 25, 2012, 05:17
#4
Senior Member

Roman Thiele
Join Date: Aug 2009
Location: London, UK
Posts: 368
Rep Power: 14
Quote:
 Originally Posted by A.A. Hi thanks for the quick reply. My next question is how can I put a vertex by giving the coordinates that it is positioned exactly on an arc, in order to have one exact face for two patches?
I don't completely understand what you mean.
__________________
~roman

 June 25, 2012, 06:05 #5 Member   Alexander A Join Date: Jun 2012 Posts: 53 Rep Power: 7 I do the inner cylinder first with a circle consisting of five blocks (one in the middle and four North East South West Blocks with arcs). Then I want to attach the cake peaces which you showed me to this inner circle. But how do I know the exact coorordinates of the knots which lay on the inner cirle´s arc which are part of the cake peace. I thought you have to know the coordinates of the knots for each block so that there is no gab between the blocks (patches) Does each patch has to be connected to the other patch exactly by the coordinates or can you have gaps between the patches?

 June 25, 2012, 07:59 #6 Senior Member     Roman Thiele Join Date: Aug 2009 Location: London, UK Posts: 368 Rep Power: 14 The problem that you sketched did not have an inner cylinder (at least not one that needs to be meshed). Therefore, you only mesh the parts that are blue. So you need to only make blocks for the blue stuff first. There is no need to mesh the inner cylinder (white cylinder). __________________ ~roman

 June 25, 2012, 08:36 #7 Member   Alexander A Join Date: Jun 2012 Posts: 53 Rep Power: 7 I also need to mesh inside the five excentric cylinders because theiy comprise the airoils. How can I give the coordinates of the knots (vertices) of the white cylinders so that they lay exactly on the arcs of blue blocks?

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