[siamak 60]

Hi

Dear Foamer's
I simply changed bouyantbuossinesqueSimpleFoam solver to write bonjiorno Model for nanofluid Heat Transfer. In this new solver which named as Mixedbonj, Temperature Equation changed to adopt bonjiorno's Model Also Concentration equation named as "V" added. My problem is that in field V Negative value obtained for some cells and I have no idea what to do ?

can anyone Help with this ISSUE ?
code and case uploaded

solver source: http://www.mediafire.com/file/fe5kxc...dbonj.zip/file
case Source: http://www.mediafire.com/file/vmw8zq.../case.zip/file
my OF is Version 6.

Please help on finding whats wrong with this solver
Thanks in Advance

[siamak 60]

I find out that with low Temperature Difference As 5 degrees of Celsius No negative value derived, with 10 degree Temp diff only 3 cells show negative value on boundary. with 20 degrees 15 cells have Negative Value and with 40 degrees Difference many cells(about 150 cells) on boundary have negative value and Also adjacent cells on internal field had negative Value So I guess that the way is to treat boundary value of V "Concentration VolScalarField" that if any cells have Negative Value it will be replaced with Zero the question is How ?


thanks for your Time

[syavash]

Originally Posted by siamak 60

I find out that with low Temperature Difference As 5 degrees of Celsius No negative value derived, with 10 degree Temp diff only 3 cells show negative value on boundary. with 20 degrees 15 cells have Negative Value and with 40 degrees Difference many cells(about 150 cells) on boundary have negative value and Also adjacent cells on internal field had negative Value So I guess that the way is to treat boundary value of V "Concentration VolScalarField" that if any cells have Negative Value it will be replaced with Zero the question is How ?


thanks for your Time

Hi,

Having negative values for a passive scalar is common when using some unbounded schemes. Try using bounded scheme like limitedLinear or van Leer as follows to suppress the negative values:

div(phi,V) Gauss vanLeer01;

This way, you limit the scalar value essentially between 0 and 1 in the entire domain.

Regards,
Syavash

[siamak 60]

Originally Posted by syavash

Hi,

Having negative values for a passive scalar is common when using some unbounded schemes. Try using bounded scheme like limitedLinear or van Leer as follows to suppress the negative values:

div(phi,V) Gauss vanLeer01;

This way, you limit the scalar value essentially between 0 and 1 in the entire domain.

Syavash

Thanks for your suggestion but it did not work ALso I think this is not a passive scalar because it can change value of Temperature Field( a little) if it Counts on considering this field as Active one.



I appreciate for helps on finding other solution

[syavash]

Originally Posted by siamak 60

Thanks for your suggestion but it did not work ALso I think this is not a passive scalar because it can change value of Temperature Field( a little) if it Counts on considering this field as Active one.



I appreciate for helps on finding other solution

Not sure why it does not work as should. I think either passive or not it should limit the values.

Regards,
Syavash