code_saturne User's Forum

Dear CS team,

I am simulating a turbulent flow using k-epsilon model. I wanted to define an extra variable (ev) which I derive from k and epsilon. Later, I must compute gradient of this (ev) variable in order to add it as a source term in k and epsilon equation.
I was wondering how shall I define this variable so that I can use grdcel subroutine? As this subroutine need coefficients (coefa, coefb etc.).
Any suggestions please, if that sounds out of scope
Thanks in advance for your time.

Vilas

Hello,

Simply define a user scalar : it will have boundary coefficients, coefa/coefb, et you may define gradients on it; actually, you may compute gradients on any cell-based 1d or 3d array, but "real" variables such as scalars have their own (and not temporary) coefa/coefb values.

Regards,

Yvan

Dear Yvan,

Thanks for the concern.
How is it possible to add a physical porperty synonymous to lets say turbulent viscosity? I tried to define it using user scalar, but it seems code saturne consider it for species transport equation (with some diffusivity coefficient). How can I have it in propce array so that I can keep the time average as well?

Thanks a lot.

Vilas

Hello,

For a simple property, defining a field is simplest (in cs_user_parameters.f90, preferably in cs_user_field_parameters or in usipsu). You can check in src/base/fldini.f90 to see how standard fields are defined (for versions 3.0 to 3.2; in trunk an future 3.3, varaibles are defined earlier, in fldvar.f90).

For gradients, you will then need to build local "coeffa/b" values. Just grep the code for "grdcel to find examples of this (doing this on 3.2 will be even better, as fields which have their own coeffa/coefb use anther routine).

Regards,

Yvan