multiphaseInterFoam: cycleAlpha

idrama · June 1, 2011, 10:58

Hello Foamers,

can anybody explain briefly the meaning of cycleAlpha in multiphaseInterFoam.

Cheers in advance

Ohbuchi · June 4, 2011, 04:10

Hi,
If you cycleAlpha set to 'yes' in fvSolution, reference phase (refPhase) will change in sequential order in the correction loop of "multiphaseMixture.solveAlpha" function.

idrama · June 4, 2011, 08:02

Okay, I understand so far! But I can't see the purpose; can you explain that, please?

Cheers

Ohbuchi · June 4, 2011, 17:55

I suppose, cycleAlpha may avoid for accumulating strain to specific phase.

For the reference phase, "alpha = 1 - Sum of alpha other phases".
This constraint must be needed for mass conservation, but for reference phase not very accurate.

alberto · June 4, 2011, 17:58

Hi,

performing subCycles consists in performing sub-stepping in time. Take a look at:

http://foam.sourceforge.net/docs/cpp..._8H_source.php
http://foam.sourceforge.net/docs/cpp..._8H_source.php

Best,

idrama · June 5, 2011, 04:41

Strange: Under usage of that option my water phase disappears; if I don't use cycleAlpha then all the phases are there but the min/max values vary from -161 to 31.
Has anybody ever seen anything like that?

In general, are not multiphase phase flow simulation well-engineered?

alberto · June 5, 2011, 20:05

Quote:

Originally Posted by idrama

Strange: Under usage of that option my water phase disappears; if I don't use cycleAlpha then all the phases are there but the min/max values vary from -161 to 31.
Has anybody ever seen anything like that?

No I did not see this caused by alpha sub-cycles. More information is required however to answer you properly.

Best,

idrama · June 6, 2011, 04:14

I wanna simulate a vessel with an thin oil layer at the wall surrounded by air. Initially, there is no water in the tank, rather, the water is being injected via a nozzle. When cycleAlpha is turned on the water jet vanished, and so vice versa. Using the interFoam solver with sub. water and air everything goes fine, even there is no water in the domain at t0.

Ohbuchi · June 6, 2011, 07:37

Hi,
I've calculate tutorial case damBreak4phase without cycleAlpha option.
And I attached result of alphaair contour, with or without cycleAlpha.
I think both results are almost same.

Ohbuchi · June 6, 2011, 07:38

I'm sorry. These contour picture were alphawater, not alphaair.

June 1, 2011, 10:58	multiphaseInterFoam: cycleAlpha	#1
idrama Senior Member Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 18	Hello Foamers, can anybody explain briefly the meaning of cycleAlpha in multiphaseInterFoam. Cheers in advance

June 4, 2011, 17:58		#5
alberto Senior Member Alberto Passalacqua Join Date: Mar 2009 Location: Ames, Iowa, United States Posts: 1,912 Rep Power: 36	Hi, performing subCycles consists in performing sub-stepping in time. Take a look at: http://foam.sourceforge.net/docs/cpp..._8H_source.php http://foam.sourceforge.net/docs/cpp..._8H_source.php Best, __________________ Alberto Passalacqua GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as in both physical and virtual formats (current status: http://albertopassalacqua.com/?p=1541) OpenQBMM - An open-source implementation of quadrature-based moment methods. To obtain more accurate answers, please specify the version of OpenFOAM you are using.

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June 4, 2011, 04:10		#2
Ohbuchi Member Masashi Ohbuchi Join Date: Oct 2009 Posts: 74 Rep Power: 17	Hi, If you cycleAlpha set to 'yes' in fvSolution, reference phase (refPhase) will change in sequential order in the correction loop of "multiphaseMixture.solveAlpha" function.

June 4, 2011, 08:02		#3
idrama Senior Member Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 18	Okay, I understand so far! But I can't see the purpose; can you explain that, please? Cheers

June 4, 2011, 17:55		#4
Ohbuchi Member Masashi Ohbuchi Join Date: Oct 2009 Posts: 74 Rep Power: 17	I suppose, cycleAlpha may avoid for accumulating strain to specific phase. For the reference phase, "alpha = 1 - Sum of alpha other phases". This constraint must be needed for mass conservation, but for reference phase not very accurate.

June 5, 2011, 04:41		#6
idrama Senior Member Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 18	Strange: Under usage of that option my water phase disappears; if I don't use cycleAlpha then all the phases are there but the min/max values vary from -161 to 31. Has anybody ever seen anything like that? In general, are not multiphase phase flow simulation well-engineered?

June 6, 2011, 04:14		#8
idrama Senior Member Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 18	I wanna simulate a vessel with an thin oil layer at the wall surrounded by air. Initially, there is no water in the tank, rather, the water is being injected via a nozzle. When cycleAlpha is turned on the water jet vanished, and so vice versa. Using the interFoam solver with sub. water and air everything goes fine, even there is no water in the domain at t0.

June 6, 2011, 07:38		#10
Ohbuchi Member Masashi Ohbuchi Join Date: Oct 2009 Posts: 74 Rep Power: 17	I'm sorry. These contour picture were alphawater, not alphaair.