What is the meaning of min(alpha)

k.kshitij · August 14, 2013, 23:22

Hi All,

I'm using interFoam solver in openFoam and the alpha(min) is becoming negative. What is the meaning of the value (mean averaged, or the minimum value of alpha in all the cells). Can any one please help me.

Thanks,

cfdonline2mohsen · August 15, 2013, 08:00

Try to bound Alpha between 0 and 1 by using limited schemes in fvSchemes. e.g:

Code:

div(phi,alpha1) Gauss vanLeer01;             //HTRL to bound the vanLeer scheme strictly between 0 and 1 to avoid negative and higher than 1 alpha

see also section 4.4.1.1 Schemes for strictly bounded scalar fields of the User-Guide for more info

k.kshitij · August 15, 2013, 08:11

Hi,

Thanks for the suggestion, actually I'm simulating diesel flow atomization inside injector atomization. For this kind of approach to handle the advective term they are using NVD(Normalized Variable Diagram) based schemes, like gamma and SFCD. The moment I implement these schemes my volume fraction becomes negative.
Currently I'm using the upwind scheme to keep the alpha bounded.

August 14, 2013, 23:22	What is the meaning of min(alpha)	#1
k.kshitij New Member Kshitij kunte Join Date: Jun 2011 Posts: 18 Rep Power: 14	Hi All, I'm using interFoam solver in openFoam and the alpha(min) is becoming negative. What is the meaning of the value (mean averaged, or the minimum value of alpha in all the cells). Can any one please help me. Thanks, ScarFace likes this.

August 15, 2013, 08:00		#2
cfdonline2mohsen Senior Member Mohsen KiaMansouri Join Date: Jan 2010 Location: CFD Lab Posts: 118 Rep Power: 16	Try to bound Alpha between 0 and 1 by using limited schemes in fvSchemes. e.g: Code: div(phi,alpha1) Gauss vanLeer01; //HTRL to bound the vanLeer scheme strictly between 0 and 1 to avoid negative and higher than 1 alpha see also section 4.4.1.1 Schemes for strictly bounded scalar fields of the User-Guide for more info Yage likes this. __________________ “If you have an apple and I have an apple and we exchange these apples then you and I will still each have one apple. But if you have an idea and I have an idea and we exchange these ideas, then each of us will have two ideas.”

August 15, 2013, 08:11		#3
k.kshitij New Member Kshitij kunte Join Date: Jun 2011 Posts: 18 Rep Power: 14	Hi, Thanks for the suggestion, actually I'm simulating diesel flow atomization inside injector atomization. For this kind of approach to handle the advective term they are using NVD(Normalized Variable Diagram) based schemes, like gamma and SFCD. The moment I implement these schemes my volume fraction becomes negative. Currently I'm using the upwind scheme to keep the alpha bounded. ScarFace likes this.

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