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-   -   Multi meshing blocks (http://www.cfd-online.com/Forums/flow-3d/81196-multi-meshing-blocks.html)

Davahue October 19, 2010 10:31

Multi meshing blocks
 
Hi, I've been trying to use some blocks at the same simulation. First, I have fixed some points to enhance the blocks and I've restricted manually the ratio between both block's cells near the unity.

But when I simulate, it's like the flow stops at the boundary, like a wall!
I've been trying with outflow B.C. allowing inflow, and continuity B.C. but the problem persists...

What's Wrong? Could anybody help me please?
thanks in advice!

Renaud GORRIA October 20, 2010 03:18

Multi meshing blocks
 
Hello,

You should set Symetry BC between the different blocks of your simulation. It will works :rolleyes:

(symetry means "by default" in this case, the solver reads it corretly as a condition between multi-blocks)

Davahue October 21, 2010 07:52

I've checked symmetry BC at the Boundary tabs for the block #2 (that is into the block #1), I run simulation and I still get the same problem, what happens? is this the BC you told me? or can I edit another kind of BC between blocks? :confused:

thanks in advice!

Quote:

Originally Posted by Renaud GORRIA (Post 279921)
Hello,

You should set Symetry BC between the different blocks of your simulation. It will works :rolleyes:

(symetry means "by default" in this case, the solver reads it corretly as a condition between multi-blocks)


Renaud GORRIA October 22, 2010 02:52

You must check all the six-BC of the block 2 as Symmetry BC.

And if the block 2 considers one side which is the same plane that a side of the block 2 (for example your block 2 is inclued in Blk1 but both start on X=0), so you have to check the same BC on the 2 sides (blk1 ande blk2). For my example Specified Presssure on X=0.

Is it your case? Is your blk2 totally inclued in blk1?

MuxaB October 23, 2010 15:02

One possible reason two adjacent mesh blocks not to be connected properly is a gap between them, so make sure that the coordinates of the mesh boundaries on both blocks are identical.

The definition of the inter-block block boundaries depends only on the relative position of the blocks, i.e., the coordinates of the boundaries. Once the pre-processor determines that the two mesh blocks are adjacent, it set the boundary type to inter-block irrespective of the user input.

The parts of an inter-block boundary that are NOT facing another block are always treated as a wall.

Davahue October 24, 2010 09:25

Quote:

Originally Posted by MuxaB (Post 280448)
One possible reason two adjacent mesh blocks not to be connected properly is a gap between them, so make sure that the coordinates of the mesh boundaries on both blocks are identical.

The definition of the inter-block block boundaries depends only on the relative position of the blocks, i.e., the coordinates of the boundaries. Once the pre-processor determines that the two mesh blocks are adjacent, it set the boundary type to inter-block irrespective of the user input.

The parts of an inter-block boundary that are NOT facing another block are always treated as a wall.

My block 2 is completly into de block 1, I've set 2 fixed points in each direction, and I've set simmetry boundary conditions in Boundaries... but it still don't run as I want.. it runs the boundaries as a wall.

When I start to simulate, I get that message:

open area mismatch at inter-block boundaries of all blocks as % of total open area at these mesh boundaries = 5.96348E-12

so I think, I've put correclty all.. but there should be a problem at the BC so I've copied here my text information:
&bcdata

wl=11, wr=8, wf=2, wbk=2,
flrbct(1,1)=16.,

/


&mesh


nxcelt=80, px(2)=-3., nycelt=40, nzcelt=10, pz(2)=1.0, px(1)=-10., py(1)=-4., py(2)=-2., pz(1)=0.0, px(3)=7., px(4)=20., py(3)=2., py(4)=4.,

/

&bcdata

iobctp(1)=1, iobctp(2)=1, iobctp(3)=1, iobctp(4)=1, iobctp(5)=1, iobctp(6)=1, ipbctp(1)=0,

/

&mesh

nxcelt=100,
px(1)=-3., px(2)=7., nycelt=100, py(1)=-2., py(2)=2., nzcelt=10, pz(1)=0.0, pz(2)=1.0,

/


Another appointment is that when I see the results, the solid that is into the block 2,
don't seem to have the resolution it must have, it has the definiton that the block 1 gives it...
I've also tried to put interblock BC manually and doesn't happen anything different!

Could help me please?

thanks in advice!:)

Renaud GORRIA October 26, 2010 04:54

In your prepin I can see that the top and the bottom of the blk1 and blk2 are adjacent. I think it comes from this point... try to set up a blk2 strickly IN the blk1.

MuxaB October 29, 2010 00:27

Even with coincidental bottom and top boundaries in z-direction, it looks in order to me. The flow should proceed along the x-direction. Could you please attach an image of the solution you receive?

One other question. When you post-process do you have both blocks selected under Mesh Block button in Analyze tab or just block 1 (which would be the default in earlier versions of FLOW-3D).

Davahue October 30, 2010 16:03

Quote:

Originally Posted by Renaud GORRIA (Post 280745)
In your prepin I can see that the top and the bottom of the blk1 and blk2 are adjacent. I think it comes from this point... try to set up a blk2 strickly IN the blk1.

Quote:

Originally Posted by MuxaB (Post 281282)
Even with coincidental bottom and top boundaries in z-direction, it looks in order to me. The flow should proceed along the x-direction. Could you please attach an image of the solution you receive?

One other question. When you post-process do you have both blocks selected under Mesh Block button in Analyze tab or just block 1 (which would be the default in earlier versions of FLOW-3D).

Now it runs ok, the problem was in the postprocess, I didn't konw that I had to check both meshes, I hadn't seen this tab in Analyze, now it's all OK. Thanks!!
I'm very gratefull with both of you, I hope it could help somebody else!

MuxaB November 1, 2010 00:50

You are very welcome, Davahue. Glad it worked.


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