Humidity ? as passive scalar?

Hello There

As far as i know it is at the moment not possible to simulate humidity in an airflow. For example for a thermal comfort simulation in a room.

Would it be possible to make use of the passive scalar source. Like having one scalar for dry air and one separate scalar for vapored water? Condensation and evaporation on surface doesnt need to be accounted for.

I dont kow if this is possible nor advisable. I would much appriciate If some expert could answer me

Thanks!

Hi, this is Fillia, thank you for reaching out!

To begin with, you can include humidity as an input for the thermal comfort parameter calculation, Have a look here: Thermal Comfort Parameters | Thermal Simulation | SimScale

However, if this is not what you are interested in, may I ask you whether you actually wish to simulate an inlet where two different passive scalars are entering the domain?

Best regards,
Fillia

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Hi Fillia
Thanks for the Link. Im aware of that.

Its more like having a possibility to have entering airflows with different humidity. Lets stay i have a room with natural ventilation. So we have a outside domain with a certain percent of humidity. Then we have a mechanical ventilation with an inlet with x percent of humidity. Now the idea ist to understand or to visualise how the air mixed and where in the room we have x percent of humidity. Something like that. (its not an actual project. I just want to understand what is currently possible)

I think my initial idea with the passive scalar is bollox, since the air and the humidity needs to be mixed from the start.

regards david

I see, as described in our documentation, passive scalar is a scalar quantity that is not actively involved in the flow physics of the CFD simulation. This is only ensured if the passive scalar source can be considered as a fluid with contaminants/species present in low concentration, getting transported with the fluid flow, thereby having a negligible effect on the thermophysical properties of the fluid. And I am not sure this is what you want to achieve at the moment, as you are referring to humidity., which is the concentration of water. Does this make sense?

Best regards,
Fillia

Yeah. Thanks for understanding that. So there is no tool to investigate the concentration of humidity in the airflow currently.
Regards David

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Make sure to include your feedback here: https://roadmap.simscale.com/tabs/2-under-consideration

Cheers!