Hi, I'd like to model with FLUENT the dispertion of gas in the atmosphere. the gas leaves the vent and disperses in the atmosphere under the effect of the wind. I've tried modeling this case defining boundary conditions for a turbulent flow with chemical species mixing and reaction but I've met problems with FLUENT. I'de like to get advices for how modeling on GAMBIT this case (Cylindrical vent introducing gas at 56 kg/s in atmosphere where's ambient air at 28 m/s.I'd also like to know which boundary conditions are required to specify on GAMBIT.

Thank you in advance for you responses.

Khalid

what is your points? there is not chemical mixig and reaction there, my suggestion: for open space behind and above the ventressure inlet for vent:velocity inlet for face of incoming wind:velocity inlet

Thank you Jesse for your response.

for boundary conditions, I've already tried these boudary conditions but it didn't work. that's my model: Vent as cylinder and open space as cube. the vent comes from under ground to the open space. so, I've modeled with gambit a cube and a cylinder. the cylinder and the cube have the same base level. the base for the cube represent the ground => wall and for the cylinder (vent) represent pressure inlet because I have to specify it: I know 2 conditions about the vent: pressure in the event + out-flow in the top of the vent. When I export the mesh to Fluent, I have an error message indicating that pressure inlet and out-flow can't be specified together. I have the same message when I change the out-flow by velocity-inletin the top of the ven => ???

But when I use out-vent in the top of the vent it works.

When I use the pressure-inlet for the other face of the cube (open space) => error message indicating: pressure inlet two adjacente faces => ????

Concerning the solver with FLUENT, I don't know exactly how modeling this case. I tought about multiphase flow => for the vent, define the fluid as gas and for the open space define the fluid as air. but I can't test this solution because I can't export correctly the mesh and I don'y know if the calculation will be possible because of the interface between the top of the vent and the open space.

I'm waiting for your suggestions.

Thank you in advance.

Khalid

there is a similare case in ANSYS CFX,if you have the resource, you may refer to that for a answer,

one clear incompatible thing is the pressureinlet and outflow, these two would not come along,refere to Fluent manual; besides if you know the velocity of outlet of the vent, you dont have to specify the boundary condition at the inlet;you just start from the top of the vent;

about the cubic open space, velocity inlet for the first half cube, pressure inlet for second half and the top of the cube; all other faces(ground, vent) taken as wall.

i hope i helped;

Hi jesse,

Happy new year and best wishes.

thank you for your response. I 've tried with model / species / transport & reaction (without reaction in my case) in FLUENT to model my case and it works. I've choose the incompressible ideal gas for the air and all the components of the vented gas. I've just a doubt about the viscosity which I kept as constant for the air and the components of the vented gas.

thank you in advance for any suggestions from you.

Khalid