Adding a turbulence dissipation rate production term

[thomas.roc]

Hi everyone,

I would like to add a turbulence dissipation rate production term into the GLS turbulence closure and more precisely in the GLS equation. Physically speaking it would be a quadratic function of the production of turbulence kinetic enegy.

So far I am struggling with numerical and implementation issues. Mainly I cannot figure out whether I should modify gls_prestep and gls_corstep or only the gls_corstep. In a same manner I haven't quiet worked out whether I should inject this term as an additional production of turbulent energy (into the Pprod term in gls_corstep for instance) or as an additional dissipation term (into the BCP term in gls_corstep).

Have anyone already try this kind of modification in a turbulence closure model ? Any thoughts or insights ?

Regards

[jcwarner]

i am not quite sure what a "turbulence dissipation rate production term " is.
If you look at my paper -
"Performance of four turbulence closure models implemented using a generic length scale method" Ocean Modeling 8, 2005, 81-113.

Look at eq 13. I we choose the correct values for p,m,n we can make 'psi' to be dissipation. So are you trying to add a term to the RHS of eq 13?

[thomas.roc]

Absolutely spot-on, I'd like to add a source term on the RHS of the previously mention equation number 13, function of the squared production of turbulent kinetic energy.
So how do I proceed ?

Cheers

[jcwarner]

I think u only need to be in gls_corstep.F. You can look at the code and find a section like this:

Code: Select all

!
!  Time-step shear and buoyancy production terms.
!
            cff=0.5_r8*(Hz(i,j,k)+Hz(i,j,k+1))
            tke(i,j,k,nnew)=tke(i,j,k,nnew)+                            &
     &                      dt(ng)*cff*Kprod
            gls(i,j,k,nnew)=gls(i,j,k,nnew)+                            &
     &                      dt(ng)*cff*Pprod*gls(i,j,k,nstp)/           &
     &                      MAX(tke(i,j,k,nstp),gls_Kmin(ng))

this provides guidance on how the source/sink terms are added. Kprod is the shear and buoyancy production terms for the tke equation, and Pprod is the shear and buoy prod terms for the gls (psi) equation. if you compare these 2 equations above to eqtns 9 and 13 in the paper, u can see how the source/sink terms are time stepped. The diffusion term is vastly more involved, and is solved w/ Thomas algorithm in gls_corstep further down. But it does not sound like u need to be in there.

[thomas.roc]

That's what I thought as well !

Thank you so much for the help