Reply To: How to setup multiphase mixture? (simulating incubation of agar)

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The air inside the petri dishes is not at 100% RH when the incubation starts. We measured the RH during the incubation process. It does not start at 100%, but after some time, the RH in every petri dish reaches and stays around 100%. Moisture escapes from the agar medium and causes this to happen.

I have also set the agar viscosity at 8000 kg/(m s), to act more as a solid.

I would like to initialize and patch the atmosphere with 40% RH (patch every fluid zone, except the agar, as 0.025 water-vapor and 0.975 air for the Volume fraction). With temperature patched at ~35 degrees Celsius, can Fluent simulate the moisture escaping the agar?

You mentioned that I would need very small timesteps for accuracy. I will most likely need to simulate at least 4 days of incubation. What size of the timestep would you recommend?

As for the compressible gas that you mentioned, do I get that by using ideal-gas in the density settings for air and water-vapor? Are there any other specific settings I need to change?

(Edit): How can I use Species Transport alongside Multiphase Models? I would like to use Species Transport for initial RH values in the atmosphere. The species (air-vapor) consists of water-vapor and air. In that case, how many phases should I have?

Before, I used three phases: agar, water-vapor and air, with mass transfer (evaporation-condensation) from agar to water-vapor. Now, having Species Transport activated, are two phases (agar and air-vapor) enough? In this case, the evaporation-condensation is from agar to air-vapor; or from agar to water-vapour (in which case, again I would need three phases for the multiphase model)?