CFD Online Discussion Forums

CFD Online Discussion Forums (
-   FLUENT (
-   -   Species mass flow inlet (

lorenz August 5, 2011 11:46

Species mass flow inlet
I have a problem with the boundary condition mass flow inlet. I have enabled the Species model and use a mixture of air and h2o, stationary. I want to model a room with air in/and outlet -> no problem. Air with a vapout content of 0.1% coming from the inlet

Additionally I want to model the vapour production by a human inside. So I have one surface with boundary condition mass flow inlet m=1.3e-5 kg/s Species h20=1. So only vapour coming out of that inlet. Inlet diffusion is disabled, because I want to keep the defined massflow.

When I run the calculation I get no convergence of the h2O content and parts with "negative" water content, meaning lower then the inlet content. How can I fix this? A UDF? How would it have to look like?

By trying different things i observed some other strange things:

- When I set the massflow from a massflow inlet to zero but have specified a Species concentration for the inlet I still get a relevant Species flow from this surface. This happens even though Species diffusion from inlet is disabled. When I enable Species diffusion from inlet the mass flow inlet becomes unrealistically big (much bigger then for a wall boundary condition with specified Species)

- When i define a wall boundary with specified Species at the border. I expect a netto mass flow from the wall to the volume because of diffusion and convection. This mass flow is visible in concentration profiles. But when I calculate the mass flow with the report tool it is zero. Why?

Thank You for help

lorenz August 11, 2011 06:13

can nobody help on this topic? I still didn't find a solution...

niket shah March 13, 2012 02:42

hey did u done with this work...bcoz I am doing the same kind of the problem...If you want to share your knowledge then reply me back...

lorenz March 15, 2012 08:26

I couldn't solve the boundary diffusion inlet massflow. But I modelled the problem now in a different way:

I use a volume source term for the water vapour source instead of boundary inlet. I use a udf for the source to be active only in a defined volume. --> This wirks very well.

All times are GMT -4. The time now is 01:01.