open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

When specifying a point sink (i.e. negative source) using the sources file, does anybody know how the model treats the tracer sink?

The source file requires that a corresponding tracer value is specified for the source, however this doesn't really make sense in the context of a negative source. I assume the model would simply remove a mass of tracer corresponding to the negative flow rate and tracer concentration at the sink point.

Regards,
Toby

I assume if you just set the tracer concentrations to 0 for a negative source then it will work correctly, as the concentration of the control volume shouldn't change if a volume of fluid is removed from it.

Not sure if the source code checks whether the source is entering or exiting (i.e. positive or negative flow) and ignores the tracer concentration if negative.

Just to close out this thread I carried out a basic test cases of a closed model domain (no liquid boundary fluxes) and a negative source. Based on this I can confirm that for sink points the amount of tracer removed from the domain is not dependent on the prescribed value but rather takes the actual modelled value at the sink location.

This intuitively makes sense and was what I expected but wanted to be sure.

Something that may be already clear to many but to me was not was that the listing printout 'ERROR ON THE QUANTITY DURING THIS TIMESTEP' for the tracer is the net mass of tracer entering or exiting the domain + any difference in total mass between the current and previous timesteps. I was under the impression that the word 'ERROR' implied an artificial numerical loss/addition of tracer but this is necessarily the case. Is there any other printout which indicates the error associated to the total mass between the current and previous timesteps excluding the fluxes?