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-   -   Using groovyBC to specify Open boundary conditions (http://www.cfd-online.com/Forums/openfoam/131210-using-groovybc-specify-open-boundary-conditions.html)

banji March 11, 2014 10:54

Using groovyBC to specify Open boundary conditions
 
Hi Foamers,

Please, is it possible to use the groovyBC to specify an open boundary condition. I am trying to simulate a die swell problem and need to specify a traction free surface on the lateral boundaries.

Thanks in anticipation.

gschaider March 11, 2014 17:58

Quote:

Originally Posted by banji (Post 479359)
Hi Foamers,

Please, is it possible to use the groovyBC to specify an open boundary condition. I am trying to simulate a die swell problem and need to specify a traction free surface on the lateral boundaries.

Thanks in anticipation.

You should be a BIT more specific about the mathematical formulation of "traction free", "lateral boundaries" etc. Never expect people to put more time into an answer than you obviously took to formulate the question

banji March 11, 2014 18:28

1 Attachment(s)
Quote:

Originally Posted by gschaider (Post 479438)
You should be a BIT more specific about the mathematical formulation of "traction free", "lateral boundaries" etc. Never expect people to put more time into an answer than you obviously took to formulate the question

Thanks Bernhard for the observation and reply.

Attached is a rough picture of the computational domain and some comments. In particular, what i would like to know is if i can specify the following bc in the attachment with groovybc.

'n' and 'm' denote the unit normal and tangent vectors to the surface and \tau is the total stress tensor.

Thanks.

gschaider March 12, 2014 18:12

Quote:

Originally Posted by banji (Post 479441)
Thanks Bernhard for the observation and reply.

Attached is a rough picture of the computational domain and some comments. In particular, what i would like to know is if i can specify the following bc in the attachment with groovybc.

'n' and 'm' denote the unit normal and tangent vectors to the surface and \tau is the total stress tensor.

Thanks.

OK. We're getting nearer. It's a multiphase problem. That wasn't really clear from your initial question. Which solver are you going to use?

Still the sketch confuses me: are you talking about the boundary condition where you've written "free surface" or of the BC on the free surface between liquid and air (the bulb in your sketch)?

Anyway: BC for the stress tensor can usually not be directly enforced but by enforcing a BC on the other fields that ensures that the stress is 0 (something like zeroGradient for U or so)

banji March 12, 2014 18:20

Quote:

Originally Posted by gschaider (Post 479635)
OK. We're getting nearer. It's a multiphase problem. That wasn't really clear from your initial question. Which solver are you going to use?

Still the sketch confuses me: are you talking about the boundary condition where you've written "free surface" or of the BC on the free surface between liquid and air (the bulb in your sketch)?

Anyway: BC for the stress tensor can usually not be directly enforced but by enforcing a BC on the other fields that ensures that the stress is 0 (something like zeroGradient for U or so)

I am using interFoam and neglecting surface tension effects. It's the free surface between liquid and air.

Is it possible to set a pde as a BC (in cases when it is difficult to obtain analytical solution of the variable on the remote field) and then groovyBC solves for the variable to be used as a BC?

gschaider March 13, 2014 10:59

Quote:

Originally Posted by banji (Post 479636)
I am using interFoam and neglecting surface tension effects. It's the free surface between liquid and air.

Is it possible to set a pde as a BC (in cases when it is difficult to obtain analytical solution of the variable on the remote field) and then groovyBC solves for the variable to be used as a BC?

For the free interface between liquid and air you can't set a BC with a VOF-solver. They can only be set on the boundaries of the grid (thus the name): where in your sketch you wrote "free surface". Your nomenclature confuses me more and more

I'm not sure what you mean with "set a PDE as a BC". But generally I'd say "no". Usually the BC can be expressed in terms of values and gradients

banji March 13, 2014 12:14

Quote:

Originally Posted by gschaider (Post 479798)
For the free interface between liquid and air you can't set a BC with a VOF-solver. They can only be set on the boundaries of the grid (thus the name): where in your sketch you wrote "free surface". Your nomenclature confuses me more and more

I'm not sure what you mean with "set a PDE as a BC". But generally I'd say "no". Usually the BC can be expressed in terms of values and gradients

You are correct, Bernhard. Maybe the snapshots attached might make my problem clearer.

The flow domain - http://math.rareinfos.com/wp-content...low_domain.png

Inlet and Outlet bc - http://math.rareinfos.com/wp-content...boundaries.png
I had no problem with this one.

free surface stress condition - http://math.rareinfos.com/wp-content...9.40.30-AM.png

simplified form of the stress condition - http://math.rareinfos.com/wp-content..._condition.png

Here is a link to the paper .

Thanks for the support for the fine utility.

gschaider March 14, 2014 20:49

Quote:

Originally Posted by banji (Post 479818)
You are correct, Bernhard. Maybe the snapshots attached might make my problem clearer.

The flow domain - http://math.rareinfos.com/wp-content...low_domain.png

Inlet and Outlet bc - http://math.rareinfos.com/wp-content...boundaries.png
I had no problem with this one.

free surface stress condition - http://math.rareinfos.com/wp-content..._condition.png

simplified form of the stress condition - http://math.rareinfos.com/wp-content..._condition.png

Here is a link to the paper .

Thanks for the support for the fine utility.

3.3 is in interFoam not a boundary condition but modelled on the interior. You can't influence that in it.

banji March 14, 2014 20:59

Thank you!

barati April 7, 2014 11:29

error when run model with groovyBC
 
Hi fomers
i want to define U Field and T field in two rooms with BuoyantBoussinesqSimpleFoam solver when immplementation the BC and run model the error into log file has plesae Help me
error is :
Reading field T

--> FOAM Warning :
From function groovyBCFvPatchField<Type>::groovyBCFvPatchField(c onst fvPatch& p,const DimensionedField<Type, volMesh>& iF,const dictionary& dict)
in file groovyBCFvPatchField.C at line 131
No value defined for T on ceiling therefore using 160{0}
Reading field p_rgh

--> FOAM Warning :
From function groovyBCFvPatchField<Type>::groovyBCFvPatchField(c onst fvPatch& p,const DimensionedField<Type, volMesh>& iF,const dictionary& dict)
in file groovyBCFvPatchField.C at line 131
No value defined for p_rgh on ceiling therefore using 160{0}
--> FOAM Warning :
From function groovyBCFvPatchField<Type>::groovyBCFvPatchField(c onst fvPatch& p,const DimensionedField<Type, volMesh>& iF,const dictionary& dict)
in file groovyBCFvPatchField.C at line 131
No value defined for p_rgh on TwallR therefore using 96{0}
Reading field U

--> FOAM Warning :
From function groovyBCFvPatchField<Type>::groovyBCFvPatchField(c onst fvPatch& p,const DimensionedField<Type, volMesh>& iF,const dictionary& dict)
in file groovyBCFvPatchField.C at line 131
No value defined for U on ceiling therefore using 160{(0 0 0)}
--> FOAM Warning :
From function groovyBCFvPatchField<Type>::groovyBCFvPatchField(c onst fvPatch& p,const DimensionedField<Type, volMesh>& iF,const dictionary& dict)
in file groovyBCFvPatchField.C at line 131
No value defined for U on TwallR therefore using 96{(0 0 0)}
Reading/calculating face flux field phi

Selecting incompressible transport model Newtonian

barati April 7, 2014 14:05

groovyBC
 
1 Attachment(s)
hi fomers
i want to attach file which immplemantaion into groovyBC
why error and not to do this model please help me

nimasam April 8, 2014 11:03

you should add keyword value to your syntax
Quote:

type groovyBC;
valueExpression "vector(0,pos().x > 8 && pos().x < 10.2 && pos().y ==3.27 ? -5 : 0, 0)";
gradientExpression "vector(0, 0, 0)";// consider the rest of celing insulated
fractionExpression "1";
value uniform (0 -0.05 0);//should be considered



barati April 8, 2014 15:06

thank a lot for note
please let me to check it and tell you if error to be clean

S.M.H May 27, 2015 03:52

1 Attachment(s)
Quote:

Originally Posted by nimasam (Post 484693)
you should add keyword value to your syntax


hi i have same problem

what i must do to fix this problem?

thanks


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