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Eulerian model for evaporation and heat exchange

    • soloviev
      Subscriber

      Hello,


       


      I am working on implementing a new simulation to model evaporation and heat at the air-sea interface under strong winds. I have looked at tutorials and the user's guide and have come up with some starting parameters. 


       


      I was hoping I could verify that these would be sufficient before trying the model.


      gravity on


      should energy equation be checked? I don't believe it's necessary here


       


      Models:


      Multiphase - Eulerian - should either Multi-fluid VOF or Dens discrete phase model be applied as well?


      Implicit formulation


      Phase interaction: mass transfer - evaporation 


      surface tension - set constant


      heat transfer - 2 resistance model 


      Viscous model - k- omega SST (dispersed?)


       


      Species transport model - does this need to be enabled with a moist air material for effective evaporation?


       


      Materials:


      water, air, moist air? (mix of air/water)


       


      Boundary conditions:


      no slip on most boundaries, except wind applied either at inlet or at top of domain. 


      would consider applying periodic boundaries if I run this model with waves eventually. 


       


      Solution methods: These I am not so certain of 


      Scheme: Phase coupled simple


      Gradient: Least squares cell based


      Pressure: Presto!


      Momentum: First order upwind


      Volume fraction: geo reconstruct


      Transient formulation: bounded second order


       


      I plan to patch the water in (no waves initially).


      I read on another forum that the evaporation needs to be driven by the relative humidity, I want to ensure this is done properly. 


       


      I would appreciate any assistance in developing this model properly!


       


      Thanks,
      Alex

    • DrAmine
      Ansys Employee
      You need two phases where the gas phase is wet air mixture. Better to use a bit more diffusive scheme at the interface like compressive. For mass transfer use UDF or species mass transfer. For turbulence stick to mixture turbulence first.
    • DrAmine
      Ansys Employee
      Interfacial area to be set as gradient or user defined.
    • soloviev
      Subscriber

      Sounds great. I will run a trial with these settings and let you know if I have any problems or questions.


       


      Thanks,
      Alex

    • DrAmine
      Ansys Employee

      Better to use UDF for mass transfer and rely on Schrage's law for mass transfer

    • soloviev
      Subscriber

      Question, should the energy equation be checked?


      Other question, would either dense discrete phase model or multi-fluid vof model be applicable here in eulerian parameters? 


      Thanks,


      Alex

    • DrAmine
      Ansys Employee

      If this is only due to concentration gradients then you can switch it off but you will then not account for any energy content change due to vaporization..


      Why DDPM? 


      MultiVOF is a submodel allowing for better interlolation schemes. So you can use it, bear in mind that the interface mass transport would rather require something diffusive use ndo not use at first GEo. (Compressive from Sharp/Dispersed is fai enough.)

    • soloviev
      Subscriber

      Thank you. I have implemented these settings. I will work on a UDF for mass transfer as well. I am only familiar with editing UDFs, I have not written one from scratch yet.


       


      Thanks,
      Alex


       

    • soloviev
      Subscriber

      Hello,


      We have been further working on this model. Is there a way to use the LES viscous model with the eulerian multiphase model? We switched to the eulerian model to implement the heat transfer in the phase interactions tab, but LES is crucial to our simulations. I see that the mixture model is compatible with LES, would this multiphase model be appropraiate for our situation? 


       


       


      Thanks,


      Alex

    • soloviev
      Subscriber

      Hello,


      I was wondering if there are any answers to my questions above? 


       


      Thanks,


      Alex

    • DrAmine
      Ansys Employee

      The LES turbulence model is only available as beta feature.

    • soloviev
      Subscriber

      So it can be used with the Eulerian model if the beta feature is turned on?


       


      Thanks,


      Alex

    • DrAmine
      Ansys Employee

      Yes.

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