urgent problem in the multi-stage multi-row computation

BalanceChen · September 18, 2010, 09:27

I generated the multi-row grid by copy and rotate an existed grid block. Thus the IGV have 8 channels and rotor have 24 channels. Then i connect them in IGG by "import IGG project". Next, the boundary condition is reset, i.e., the connecting face is set to be "ROT".
The problem is when i am going to run in fine turbo, after reading in the grid, errors go as

"CSTRDA/C1DMED: TOO MANY MERGER PAIRS( 41 > 40)

NBCMAX EXPERT PARAMETER SHOULD BE INCREASED"

I have no idea of what should i do, is there anybody come across problems like this, please help me, thx~~

Hamidzoka · September 20, 2010, 23:14

NBCMAX is an expert parameter that can be set in NUMECA.
when you change the fine/turbo mode from "standard" to "expert"
you can find it in one of tables of "contorl variables" page, namely"integer parameters".
but i think your problem is mainly due to number of channels you 've selected. why 8 and 24? perhaps this enormous amount of mesh causes such problem. if you are to solve an steady problem, just one blade per each row will be enough. but in case an unsteady solution is desired, the best solution is to choose the lowest integer balde count ratio. e.g. a configuration of 1 to 3 is adequate for this case. this will reduce your meshing to 1/8.

Regards

BalanceChen · September 23, 2010, 21:26

Thank you very much for your detailed explanation, problem is figured out~
The problem i consern now is with an nonaxisymmetrical inlet flow, whole rows computation is thus needed.

Thanks again.

Regards.

September 18, 2010, 09:27	urgent problem in the multi-stage multi-row computation	#1
BalanceChen Member Join Date: Sep 2010 Posts: 45 Rep Power: 15	I generated the multi-row grid by copy and rotate an existed grid block. Thus the IGV have 8 channels and rotor have 24 channels. Then i connect them in IGG by "import IGG project". Next, the boundary condition is reset, i.e., the connecting face is set to be "ROT". The problem is when i am going to run in fine turbo, after reading in the grid, errors go as "CSTRDA/C1DMED: TOO MANY MERGER PAIRS( 41 > 40) NBCMAX EXPERT PARAMETER SHOULD BE INCREASED" I have no idea of what should i do, is there anybody come across problems like this, please help me, thx~~

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September 20, 2010, 23:14		#2
Hamidzoka Senior Member Hamid Zoka Join Date: Nov 2009 Posts: 282 Rep Power: 18	NBCMAX is an expert parameter that can be set in NUMECA. when you change the fine/turbo mode from "standard" to "expert" you can find it in one of tables of "contorl variables" page, namely"integer parameters". but i think your problem is mainly due to number of channels you 've selected. why 8 and 24? perhaps this enormous amount of mesh causes such problem. if you are to solve an steady problem, just one blade per each row will be enough. but in case an unsteady solution is desired, the best solution is to choose the lowest integer balde count ratio. e.g. a configuration of 1 to 3 is adequate for this case. this will reduce your meshing to 1/8. Regards

September 23, 2010, 21:26		#3
BalanceChen Member Join Date: Sep 2010 Posts: 45 Rep Power: 15	Thank you very much for your detailed explanation, problem is figured out~ The problem i consern now is with an nonaxisymmetrical inlet flow, whole rows computation is thus needed. Thanks again. Regards.