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Multiphase: Diameter model for droplets in gas

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Old   August 4, 2022, 05:48
Default Multiphase: Diameter model for droplets in gas
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Lennart
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Hi,

I am simulating liquid droplets moving through a continuous gas phase with the multiphase solver multiphaseEulerFoam.

In the phaseProperties dictionary, a diameter model has to be defined for each phase. Currently, I am looking for a suitable diameter model for the liquid droplets. From my understanding, the following types are available:
  • constant - constant diameter
    Not suitable, as I am expecting the droplets to decrease in size due to evaporation.
  • isothermal - diameter changes with pressure according to d = d_0*(p_0/p)^(1/3)
    According to this model, the diameter would increase with a low pressure, as the particle is less compressed. This model seems to be made for compressible gas bubbles in a continuous liquid phase. In the case of liquid droplets however, the diameter should rather decrease with a low pressure due to evaporation.
  • IATE - a more complex model, however only for gas bubbles in a continuous liquid phase
  • linearTsub - diameter changes based on heat transfer due to liquid-sub-cooling, therefore also only only for gas bubbles in a continuous liquid phase
Except for the constant diameter model, which is not physical, all diameter models seem to be made for bubbles only. Is there any additional model for droplets that I am missing?
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Old   August 5, 2022, 03:56
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AFAIK, there are no evaporation models implemented due to thermal condition changes. At least for Euler-Euler approach. For VoF, there are some models like Lee or interfacialHeatResistance available, but again: I'm not sure
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Old   August 5, 2022, 05:20
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Hey


I have been posting recently about a similar simulation, involving liquid nitrogen droplets carried by gaseous methane:


Parcels minimum temperature in reactingParcelFoam


I think it would be worth a shot to try the reactingParcelFoam solver (eulerian for the gaseous phase and lagrangian for the particles), and you can setup evaporation and heat/mass transfer in different ways.
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Old   August 5, 2022, 12:15
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Quote:
Originally Posted by überschwupper View Post
AFAIK, there are no evaporation models implemented due to thermal condition changes. At least for Euler-Euler approach. For VoF, there are some models like Lee or interfacialHeatResistance available, but again: I'm not sure
Thanks for the feedback.

I have done some tests with the constant diameter model and it shows that the water vapour fraction in the continuous phase is indeed increasing around the water droplets. Also, the gas temperature is decreasing (probably due to the latent heat required for the evaporation).

Therefore, it seems to me that evaporation and mass transfer are indeed working properly even though the droplet diameter is kept constant (as paradox as this sounds...).
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Old   August 5, 2022, 12:22
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Quote:
Originally Posted by Alczem View Post
Hey


I have been posting recently about a similar simulation, involving liquid nitrogen droplets carried by gaseous methane:


Parcels minimum temperature in reactingParcelFoam


I think it would be worth a shot to try the reactingParcelFoam solver (eulerian for the gaseous phase and lagrangian for the particles), and you can setup evaporation and heat/mass transfer in different ways.
Thanks a lot for this recommendation!

In fact, reactingParcelFoam is the solver I have initially worked with... However, I was facing some stability problems and was not satisfied with the results, so I have decided to try again with a multiphase solver.

I am still unsure which of the two methods to focus on. Anyway, it is good to know you have successfully used the lagrangian one for a similar case.
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