- **OpenFOAM**
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- - **About GroovyBC**
(*http://www.cfd-online.com/Forums/openfoam/114857-about-groovybc.html*)

About GroovyBCHi Foamers,
I am using OpenFOAM2.1.1 version. My solver is steady state and i prepared it by modifying "simpleFoam" solver. I am facing problem with boundary condition for the scalar field (lets say T). The governing equation for the field T as follows: Code: solve ( fvm::div(phi, T) + fvc::div(J) ); At the fixed Walls i need to apply zero flux boundary condition. In the above equation " J" is the flux. So i need to apply J.n=0 at fixed walls. I have little experienced in handling "groovyBC". Can anyone help me how to write this expression. Thanks in advance. Regards M Mallikarjuna Reddy |

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Assuming that J is a surface field then fvc::div(J) only uses the values on the boundary patches (the situation is not better if J is a volume-field). Anyway: if you're not doing completely different physics to somebody else then J is somehow related to grad(T) which makes the second term boil down to something like laplacian(lambda,T) for which you can use the fvm-form which makes everything much more stable. If J is completely unrelated to T then only the actual value of div(J) in the cells matters for the solution of the T-equation and if J is a vector and J=(0,0,0) is not good enough for you then a slip-boundary condition is sufficient |

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Dear gschaider, Thanks for the quick response. In my case i defined J as volume field: Code:
`volVectorField J` Quote:
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Moreover i am struggling with divergence problem. From your valuable suggestion I understood that there is divergence in my case since J is defined as a volume field. Should I define J at the surface field to achieve convergence? Thanks Reddy |

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For convergence: i can only be general here: you mentioned that the functions fX depend on T: the best strategy would be to identify the parts that depend on T, linearize them, put these parts implicitly into the T-equation using fvm-operations and only put the rest of the terms into the explicit source. Also sit down with pen and paper and see if the BC for J can be expressed in terms of T on the boundary. Then implement that BC for T. If you insist on having an all-explicit source term the way you do now you may need veeeery small time-steps (probably) Yeah: if you know what you're doing a surfaceScalar-field for the flux is better than a volVector-field (see creation and usage of phi in the regular solvers) |

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Thanks for your reply. I'll go through your suggestion and let you know if i succeed. Thanks Regards Mallikarjuna Reddy |

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