reducing cfpk in mesh block

mina00 · June 27, 2014, 11:11

İn my mesh block simulation results writing ''in mesh block 2 recommend reducing cfpk by factor of 10''

what is cfpk????

http://upcity.ir/images2/98634055806309742224.jpg

Saeid · June 28, 2014, 17:26

in program window, go to:
Model setup>>Numerics>>
"Volume of Fluid Advection" part and then>> Advanced option>>

you can change F-packing Coefficient there. (cfpk)

Zograth · July 2, 2014, 18:34

All your problems are because of your mesh. With a good mesh you can avoid cfpk errors.

JBurnham · July 5, 2014, 20:40

Zograth is right that a good mesh can eliminate F-packing errors, but there are other causes. In particular, whenever the free surface makes a sharp corner that oscillates in position (e.g., the toe of hydraulic jumps, the impingement trumpet of a falling jet) there will be F-packing errors there.

They are warnings, and do not mean that there is a problem with the solution. In cells that get the warning, the pressure solution is being artifically adjusted slightly to make sure that all underwater cells have fluid fraction F = 1 (keeping proper mass accounts). The rest of the cells have the usual pressure solution, so they tend to protect the cell that is being adjusted.

Usually you can ignore F-packing errors.

mina00 · July 8, 2014, 11:08

Hello JBurnham
I refined the mesh and this error is solve. But another problem appear.
I attached my prepin file.
can you help me??

http://upir.ir/934/weir.zip

So thanks.

June 27, 2014, 11:11	reducing cfpk in mesh block	#1
mina00 Member mina salehi Join Date: Jan 2014 Posts: 30 Rep Power: 12	İn my mesh block simulation results writing ''in mesh block 2 recommend reducing cfpk by factor of 10'' what is cfpk???? http://upcity.ir/images2/98634055806309742224.jpg

June 28, 2014, 17:26		#2
Saeid New Member Saeid Ahmadvand Join Date: Jun 2014 Posts: 15 Rep Power: 11	in program window, go to: Model setup>>Numerics>> "Volume of Fluid Advection" part and then>> Advanced option>> you can change F-packing Coefficient there. (cfpk) mina00, boy and inner7549 like this.

July 2, 2014, 18:34		#3
Zograth New Member frode gimsøy Join Date: Jun 2014 Posts: 9 Rep Power: 11	All your problems are because of your mesh. With a good mesh you can avoid cfpk errors. mina00 and boy like this.

July 5, 2014, 20:40		#4
JBurnham Senior Member Jeff Burnham Join Date: Apr 2010 Posts: 204 Rep Power: 17	Zograth is right that a good mesh can eliminate F-packing errors, but there are other causes. In particular, whenever the free surface makes a sharp corner that oscillates in position (e.g., the toe of hydraulic jumps, the impingement trumpet of a falling jet) there will be F-packing errors there. They are warnings, and do not mean that there is a problem with the solution. In cells that get the warning, the pressure solution is being artifically adjusted slightly to make sure that all underwater cells have fluid fraction F = 1 (keeping proper mass accounts). The rest of the cells have the usual pressure solution, so they tend to protect the cell that is being adjusted. Usually you can ignore F-packing errors. mina00, boy and inner7549 like this.

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July 8, 2014, 11:08		#5
mina00 Member mina salehi Join Date: Jan 2014 Posts: 30 Rep Power: 12	Hello JBurnham I refined the mesh and this error is solve. But another problem appear. I attached my prepin file. can you help me?? http://upir.ir/934/weir.zip So thanks.