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Hello,

I need to add more diffusion for tracers in the main body of the model, but as I increase the diffusion coefficient, the advective flux through liquid flow boundaries is being negated by the increased diffusive flux, resulting in the net flux of the tracer into model dropping towards zero. So I would like to impose liquid boundary advective flux only without the diffusive flux.

Is there a simple way to turn off diffusion though liquid boundaries for tracers.

I think that I could artifically set the lateral boundary type to solid temporarily for the diffusion step only and resetting after.

However the diff3d routine has not way of checking what called it that is if it is solving for tracers or velocities etc. The same goes for the convective transport routine. Adding an indicator of what is being solved in these generic solvers would be very helpful in the future.

Appreciated any suggestions.
John

Hello John,

Just to understand, is this boundary an exit? If it is an entrance the keyword:

TREATMENT OF FLUXES AT THE BOUNDARIES : 2

should give you exactly the quantity of tracer required, equal to discharge * prescribed concentration. If the boundary is an exit you cannot really monitor what happens.

Regards,

JMH

thankyou,

That actually makes a lot of sense. I have wondered exactly how that boundary option worked. So on an inflow, the defined flux is what is used....

John

... and this keyword may act on any open boundary, so possibly :

TREATMENT OF FLUXES AT THE BOUNDARIES : 1;2

if you want the option 2 only on boundary 2.

Regards, JMH.