when I use multi block the condition of stability can not be fulfilled

mostafa_khan · February 10, 2012, 06:28

The run with :2 block(multi block) . time :49 & 50s ===>>> we haven’t the condition of stability

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

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

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

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 :

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

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).

February 10, 2012, 06:28	when I use multi block the condition of stability can not be fulfilled	#1
mostafa_khan New Member www.manvatoo.com Join Date: Nov 2011 Posts: 5 Rep Power: 14	The run with :2 block(multi block) . time :49 & 50s ===>>> we haven’t the condition of stability ================= The run with: one block. time :49 & 50s ===>>>we have the condition of stability =============== 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.

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February 10, 2012, 12:12		#2
mostafa_khan New Member www.manvatoo.com Join Date: Nov 2011 Posts: 5 Rep Power: 14	new run with new meshing 3block-linked : 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

April 19, 2012, 12:17		#3
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 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).