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-   -   when I use multi block the condition of stability can not be fulfilled (http://www.cfd-online.com/Forums/flow-3d/97169-when-i-use-multi-block-condition-stability-can-not-fulfilled.html)

mostafa_khan February 10, 2012 06:28

when I use multi block the condition of stability can not be fulfilled
 
The run with :2 block(multi block) . time :49 & 50s ===>>> we havenít the condition of stability

http://up1.iranblog.com/images/07579212815572826888.jpg
http://up1.iranblog.com/images/72605597896341112526.jpg
=================

The run with: one block. time :49 & 50s ===>>>we have the condition of stability

http://up1.iranblog.com/images/75901615364813247522.jpg
http://up1.iranblog.com/images/75871595434115422480.jpg

===============

Hello
Im working on flip bucket.
As you illustrated in the pictures, when I use multi block the condition of stability can not be fulfilled, but in one block im able to reach the condition of stability.
As you know,one block simulation is time consumption
I want to know there is away to reach the condition of stability by using multi-block?
I want to know where I made mistake.i wonder if my friends could possibly make it crystal clear?
Best regards.

mostafa_khan February 10, 2012 12:12

new run with new meshing

3block-linked :

http://up1.iranblog.com/images/72279389513980366691.png


there is that problem
the condition of stability can not be fulfilled

details:
block N.1 : cell size=1 cm
block N.2(on flip bucket) : cell size= 0.6 cm
block N.3 : cell size=1 cm
t:60s


http://up1.iranblog.com/images/25458325263069062774.png

JBurnham April 19, 2012 12:17

The cells should be even multiples of those in the adjacent block. That is, your flip-bucket block should have cells that are 0.5 units long (cubes are best), not 0.6. FLOW-3D interpolates results between mesh blocks; if the cell grid lines don't line up exactly, then interpolation leads to momentum diffusion and stability difficulties (pressure solver).


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