export multi-blocks structured grids to unstructured CGNS format

cfdbooks · September 18, 2017, 21:17

I try to export multi-blocks structured grid using unstructured CGNS format for my own CFD solver. Is the exported grid a single block unstructured grid or a multi-blocks grid? How could I get a single block unstructured grid? Thanks in advance.

dgarlisch · September 20, 2017, 09:58

The Pointwise CGNS CAE exporter always preserves the multi-block grid topology. That is, blocks with the same VC are not combined into a single block at export.

I would suggest joining the blocks, except that Pointwise (v18.0R3) does not support joining structured blocks into a single unstructured hex block. Please contact Pointwise support to request this capability (support at pointwise dot com).

I suggest you try:

Exporting to a different format (see list below)
Create your own CAE exporter for your solver. See the Pointwise CAE Plugin SDK.

I did a quick scan for exporters that combine VCs. One of these CAE exporters may do the trick:
CaeAcuSolve, CaeOpenFOAM, CaeStarCD, CaeStarCDv4, CaeUnsADS, CaeUnsAnsysCFX, CaeUnsCFDPP, CaeUnsCRUNCH, CaeUnsEdge, CaeUnsExodusII, CaeUnsFluent, CaeUnsFUN3D, CaeUnsGambit, CaeUnsNSU3D, CaeUnsSCRYUTetra, CaeUnsShipIR, CaeUnsSU2, CaeUnsTAU, CaeUnsTetrex, CaeUSM3DVGRID

cfdbooks · September 20, 2017, 23:27

Hi,David.
Thanks for your reply. In fact, we are using Cobalt exporter but try to migrate to CGNS. When some one try to export multi-block grid using unstructured format, he needs a single block grid in most cases.

dgarlisch · September 21, 2017, 10:53

Interesting migration...
Cobalt is a face-based grid format.
CGNS is a cell-based grid format.

You may want to consider using OpenFOAM export. It is a face-based format and it will group cells by VC. So, in essence, you will get a single, unstructured block in the exported grid no matter how many blocks are defined in Pointwise.

If you want a cell-based format, try out the formats I listed above.

If you want ultimate control on the export, you should consider creating a CAE export plugin (see link above). A plugin will integrate seamlessly into Pointwise and give you complete control on how your grid data is exported. A plugin also lets you define the BC and VC types supported for your solver. There are example plugins included with the SDK download to help get you started.

Good luck.

cfdbooks · September 21, 2017, 20:02

Our solver uses a cell-vertex finite volume scheme. Coblat format is simple and is not difficult to transfer to the format we needed. We try to use CGNS because it is widely accepted by commercial CFD software and individual CFD solver. Thanks.

September 18, 2017, 21:17	export multi-blocks structured grids to unstructured CGNS format	#1
cfdbooks New Member Join Date: May 2009 Posts: 19 Rep Power: 16	I try to export multi-blocks structured grid using unstructured CGNS format for my own CFD solver. Is the exported grid a single block unstructured grid or a multi-blocks grid? How could I get a single block unstructured grid? Thanks in advance.

September 20, 2017, 09:58		#2
dgarlisch Senior Member David Garlisch Join Date: Jan 2013 Location: Fidelity Pointwise, Cadence Design Systems (Fort Worth, Texas Office) Posts: 307 Rep Power: 14	The Pointwise CGNS CAE exporter always preserves the multi-block grid topology. That is, blocks with the same VC are not combined into a single block at export. I would suggest joining the blocks, except that Pointwise (v18.0R3) does not support joining structured blocks into a single unstructured hex block. Please contact Pointwise support to request this capability (support at pointwise dot com). I suggest you try: Exporting to a different format (see list below) Create your own CAE exporter for your solver. See the Pointwise CAE Plugin SDK. I did a quick scan for exporters that combine VCs. One of these CAE exporters may do the trick: CaeAcuSolve, CaeOpenFOAM, CaeStarCD, CaeStarCDv4, CaeUnsADS, CaeUnsAnsysCFX, CaeUnsCFDPP, CaeUnsCRUNCH, CaeUnsEdge, CaeUnsExodusII, CaeUnsFluent, CaeUnsFUN3D, CaeUnsGambit, CaeUnsNSU3D, CaeUnsSCRYUTetra, CaeUnsShipIR, CaeUnsSU2, CaeUnsTAU, CaeUnsTetrex, CaeUSM3DVGRID

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September 20, 2017, 23:27		#3
cfdbooks New Member Join Date: May 2009 Posts: 19 Rep Power: 16	Hi,David. Thanks for your reply. In fact, we are using Cobalt exporter but try to migrate to CGNS. When some one try to export multi-block grid using unstructured format, he needs a single block grid in most cases.

September 21, 2017, 10:53		#4
dgarlisch Senior Member David Garlisch Join Date: Jan 2013 Location: Fidelity Pointwise, Cadence Design Systems (Fort Worth, Texas Office) Posts: 307 Rep Power: 14	Interesting migration... Cobalt is a face-based grid format. CGNS is a cell-based grid format. You may want to consider using OpenFOAM export. It is a face-based format and it will group cells by VC. So, in essence, you will get a single, unstructured block in the exported grid no matter how many blocks are defined in Pointwise. If you want a cell-based format, try out the formats I listed above. If you want ultimate control on the export, you should consider creating a CAE export plugin (see link above). A plugin will integrate seamlessly into Pointwise and give you complete control on how your grid data is exported. A plugin also lets you define the BC and VC types supported for your solver. There are example plugins included with the SDK download to help get you started. Good luck.

September 21, 2017, 20:02		#5
cfdbooks New Member Join Date: May 2009 Posts: 19 Rep Power: 16	Our solver uses a cell-vertex finite volume scheme. Coblat format is simple and is not difficult to transfer to the format we needed. We try to use CGNS because it is widely accepted by commercial CFD software and individual CFD solver. Thanks.