SimScale CAE Forum

Obstacles after pressure inlet and some other questions


Hi guys,

I’m have a few questions about the proper approach for simulating different situations.

The first example, if I would have a room with one window and some equipment that is consuming air at a high rate on another side of the room. What approach would be the best to simulate pressure drop and wind speed at the inlet caused by air filter installed after pressure inlet? Let’s assume that the filter has a pressure drop of 100Pa. Should I set the pressure inlet to -100Pa or I need to create porous media with the right settings to simulate filter?
Is using pressure inlet/outlet to simulate an open window in the room a proper way?

In another example, instead of the air filter, I would like to have movable louvers with settings at 100% (fully open), 50% (half open) and 0% (closed). Is there a way to change this setting inside of the Simscale (using porous media, for example), or it is necessary to change louver angle in cad software? It would be also interesting for me to see the pressure change in the room along with the airspeed at the inlet.

I have one question about porous media. Is it possible to use it as a tool for blocking the air in ducts? For example, I have one main duct, which separates left and right at some point. For simulation I would like to try three different scenarios, one with air going both right and left, one with only right air direction and one with only left air direction. It would be great to use some tool in simscale (porous media maybe) to block right/left duct instead of changing the geometry and doing mesh again.

I think this is all for now, thanks for your help and for helping me to understand how simscale and cfd simulations are working :blush:


Hey @mpilas!

Nice to see you again :slight_smile: I remember your posts in this thread: Failed simulation in building wind CFD - how is the setup you want to realize different from the old one? Is it just about the pressure drop itself?

Regarding porous media, that is indeed possible but you would need to know the properties or at least approximate the filter behavior. This post here by @varsey might help you out: Setting Up a Simulation Using Porous Media. Regarding blocking maybe @varsey can give you some parameter examples to accomplish this. If you want to have the flow blocked in two directions and have it concentrated in one direction you can set the coefficients to a high value.

Regarding the louvers I would not approach this with porous media as this will definitely has an influence on the flow behavior and certainly makes a difference in terms of modeling. Just upload adapted CAD models and make changes accordingly, that way you have at least a distinct modeling we can also work with.




Hi @mpilas!

Porous media would be the most practical choice for your simulation. It’s fast and robust.
Since you already know what is the pressure drop, just use this number to calculate porous media parameters using formulas in this discussion: **Setting Up a Simulation Using Porous Media **.

Best regards,


Hi guys, @jousefm likevise :slight_smile: You remembered well, and actually this first example maybe can be applied to that simulation. Let’s say that I have one big air filter at the entrance of the building and I’m interested to see how pressure will change in the building after adding filter and will wind speed change at the building entrance.

For filter properties I know that it is a G2 filter with a pressure drop of 40Pa.

Thank you @jousefm for clarifying thing for me.

Hi @varsey, thank you for the link. I have check it before, but I don’t understand which formula should I use? I assume this one:

d = 150 (1-eps)^2 / (eps^3 * D^2)
f = 1.75 * (1-eps) / (eps^3 * D)

But I don’t have information about porosity (D) and mean particles diameter (eps). In most cases manufacturers provides filter classification, average arrestance and efficiency with min/max. pressure drop.