HI Abdelkader,

Can you describe your system of interest in more details, please? Is it a chamber with inlets and outlets? Where is the H2S supposed to enter the domain?

In your screenshots, you defined a source term for H2S (with 7 kg/m3/s !!, not 7 kg/s) for the zone named solid:018, which means that H2S is produced with the defined volumetric reaction rate inside this volume. But what I read from your description, you may want to define an inlet boundary condition for H2S, defined as a velocity or mass flow inlet, instead. If you had an mass-flow inlet in your system, you could define the desired mass flow rate under Boundary Conditions -> e.g. "inlet" -> Edit -> Momentum -> mass flow rate, and a species mole fraction under Boundary Conditions -> e.g. "inlet" -> Edit -> Species -> species mass fraction. Obviously, you already have a pressure-outlet boundary conditions, as your solver says that you get reversed flow "in 98262 faces on pressure outlet-10".

Btw - it's not "cell zone method", you only defined boundary conditions for the fluid volume.

However, these ideas are just an educated guess because it's not absolutely clear to me what you try to model...

Best regards,

Stephan

Hi, Stephan,

Thank you for your valuable inputs. Actually my system of interest is a large complex terrain in which I would like to study the release of the H2S. the air is coming from an inlet boundary condition and the H2S is releasing somewhere within the colobal volume which is rectangular geometry. I have used the cell zone modeling to mark the cells where the H2S should release as a source term and the zone named solid:18 is the marked cells. The mass source shown in the screen shots is defined by (kg/m3/s) and the H2S source also by (kg/m3/s) and here I`m confused where to include the mass fraction of the H2S and what Mass source means ? it is the mass flow rate trough these marked cell (in volumetric unity ?)

yes I do have pressure outlet boundary condition along the side and the top surfaces of the rectangular volume.

I would appreciate your kind clarifications on the issue if you got an experience on such simulations.

Kind regards,

Abdelkader

OK, I hope that I understand you correctly now: simply speaking you have a box of given volume with at least one inlet and one outlet, only air is entering the domain through the inlet (green surface in the enclosed sketch) but a mixture of air and H2S will leave the domain (orange surfaces) because H2S is produced within the volume defined by the marked cells (blue). If this is correct, you don't have to define a mass fraction for H2S inside the cell volume. The H2S mass balance for the box can be written as follows: dc(H2S)/dt = -c(H2S)*F+R(H2S) where F is the flow rate at the exit of the blue box, which is of course determined by the air flow rate through your system, and R(H2S) is the volumetric H2S production rate (mass source) inside the blue box. For example, if you want to release a H2S/air mixture from the box with a flow rate of 7kg/s and a H2S volume fraction of 10%vol, you can define a H2S mass source of 0.7 kg/s - the H2S mass fraction in both, the cell zone and your overall domain, will then be determined by the flow in your system.

Again, the mass source in Fluent means the volumetric production rate inside the cell zone (please also refer to the user's guide, section 7.1.1. Species Transport Equations for further information).

Kind regards,

Stephan

Thank you Stephan, it seems to be clear for me now.

I really appreciate your valuable inputs.

Kind regards,

Abdelkader

Dear Stephan,

I have the similar problem. When I define h2s mass source (i.e. 400kg/m3.s) as constant for the cell zone volume, and I have inlet species transport, I am not able to see any release from the box. I was just wondering what I have missed in the simualtion!

Cheers.