Learning Forum

[jcooper]

Hi Oscar:

A  simple flux is something with a numerical value.  Fluxes that introduce dependencies on other species are unsupported because linearisation is required to keep these kinds of specifications from resulting in overconsumption/overshoot of species.

 

You are right that Fluent sources are volumetric only.  A surface source can be emulated by adding inflation to that surface and then splitting one or more of the inflation layers off to create to a new cell zone in Fluent.

To assign an inflation layer to a new zone in Fluent, you can follow the steps outlined below:

 If you are dealing with a constant number of elements in the inflation layer, you can use the following method:

1. Go to Adapt > Boundary > Option = Cell Distance > Number of Cells = inflation layers > Boundary Zone = [wall boundary with inflation] > Mark
2.  Then proceed to Mesh > Separate > Cells > Mark > Registers = Marked Zone > Separate.

 

 

 

 

You should get a message like:

 

And possibly others, depending on what that wall is connected to.

This process will allow you to separate the inflation layer into a separate cell zone, which will allow you to apply a volumetric source/sink.

Note that for a source of H2o based on H2 concentration (or mass fraction), ie: 0.001*molconH2, there MUST be a corresponding equal and opposite "source" of H2 -0.001*molconH2. (This was not the case in your implementation.)  Note that species source terms may have to be linearized if the source depends on the mass fraction of the specie it is being applied to.  Linearization will require the source term to be described via UDF as in this example for momentum source terms:

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v241/en/flu_udf/flu_udf_DetailedExampleUDFs.html%23flu_udf_udf_mom_source

The source linearization coefficient is typically the derivative of the source term w.r.t. the solved specie.

 

Best Regards,

Judy