SimScale CAE Forum

Simulating fluid flow just outside an outlet


I’m a newbie to SimScale, trying to simulate fluid flow through a model of a simple device that receives air from a compressor at a single inlet, and releases air into the atmosphere from a single outlet. The primary area of interest is how fluid flows just outside the outlet. Given that the simulation requires flows both “internal” and “external” to the model, I’m a little unclear on what is the most effective way to proceed…

Is extending the model’s mesh to include a portion of the “outside world” the best/only way to do this?

Alternatively: Is it possible (and does it make sense!) to place the model’s mesh inside (or partially inside?) another mesh representing the outside world? If this second case makes sense: What is the recommended way to handle the relative placement of “model” and “world” meshes, such that the inlet doesn’t influence flow within the “world” mesh?

I also wanted to double check that an appropriate choice for outlet (and/or “world”) boundary condition would be a pressure outlet with the value 0… Does that choice make sense? (The inlet boundary condition is a velocity or flow rate inlet).

Any recommendations would be hugely appreciated.


Hi @spacemanspiff and first of all welcome to SimScale! :wink:

The first project that came into my mind when you talked about “releasing air into the atmosphere” was the project from @Milad_Mafi Chimney pollution analysis .

For the simulation setup, a steady-state turbulent fluid flow analysis type in a addition to a passive scalar model for the exhaust gases was used. This means that the gas itself does not have an impact on the fluid flow but is transported with the flow. Also molecular diffusion effects are accounted for - however depending on the velocity field of the flow, it is often very small in comparison to the convective transport effects. The image below shows the concentration of carbon dioxide in the atmosphere. One can see how the gas is distributed within the environment.

Is that something that you were looking for?

You can copy this project into your Dashboard and have a look at the settings there.

Feel free to ask if something is not clear enough.

Happy SimScaling!


Thanks - I’ll take a look at the chimney simulation.