Problem in Multiphase setup with phases

NiBa · November 6, 2014, 06:01

Hello to everybody, I try to simulate a heat transfer in a boiler with fluent. I have two inlets (air and water lquid). I used the multiphase model so i choose 3 phases (air, water(l), water(v)). I define as primary phase at the tab 'Phases' the water liquid as the maual said. However while i run the calculation, no iterations appears because there is an error that say 'Primary Phase must be the liquid phase' although i have already define as it. Should i change the primary phase
somewhere else or in a tab in setup area?
Also in the boundary i can not define different phases for inlets. i mean that when i change 'inlet velocity air' to 'phase 1' the 'inlet velocity water' becomes automatically 'phase 1'. I guess that i have to fill all the tabs of the phases (and the mixture) and put in some phases volume of fraction 0. i dont know if it is something like that correct.
Sorry for the bad english.

NiBa · November 6, 2014, 07:34

I had finally problem with the initialization. Now i try to run the setup and i confront problems that related to the temperature. For instance, the residuals diverged because of problem in temperature ->decreasing coarsening group size and also increasing relaxation sweeps.i have tried VOF model but i think that the appropriate is the eulerian. I work on the eulerian model using the parameter boiling. For the viscocity i use k-e. i dont know if there is a problem of compatibility.

NiBa · November 6, 2014, 10:12

I think that for this problem it is needed to initialize separately water and air because of the grat difference in temperature. Can someone help me with this trial. I try to find something about advanced initialization but i can't!
Sorry for my english again.

arindam · November 7, 2014, 17:59

I have exactly same problem, I was running a boiling model. First run liquid water through the model to get the temperature right, then introduce vapor phase, that way you get convergence easily. Also try patching the temperature values at various zones, if you can hand-calculate them.

Hope this helps.

Abdullah hassan · December 2, 2023, 04:42

arindam, can you please make me understand how to first only run the water and then Introduce the vapor?

November 6, 2014, 06:01	Problem in Multiphase setup with phases	#1
NiBa Member Nikolaos Babilas Join Date: Nov 2014 Posts: 37 Rep Power: 12	Hello to everybody, I try to simulate a heat transfer in a boiler with fluent. I have two inlets (air and water lquid). I used the multiphase model so i choose 3 phases (air, water(l), water(v)). I define as primary phase at the tab 'Phases' the water liquid as the maual said. However while i run the calculation, no iterations appears because there is an error that say 'Primary Phase must be the liquid phase' although i have already define as it. Should i change the primary phase somewhere else or in a tab in setup area? Also in the boundary i can not define different phases for inlets. i mean that when i change 'inlet velocity air' to 'phase 1' the 'inlet velocity water' becomes automatically 'phase 1'. I guess that i have to fill all the tabs of the phases (and the mixture) and put in some phases volume of fraction 0. i dont know if it is something like that correct. Sorry for the bad english.

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November 6, 2014, 07:34		#2
NiBa Member Nikolaos Babilas Join Date: Nov 2014 Posts: 37 Rep Power: 12	I had finally problem with the initialization. Now i try to run the setup and i confront problems that related to the temperature. For instance, the residuals diverged because of problem in temperature ->decreasing coarsening group size and also increasing relaxation sweeps.i have tried VOF model but i think that the appropriate is the eulerian. I work on the eulerian model using the parameter boiling. For the viscocity i use k-e. i dont know if there is a problem of compatibility.

November 6, 2014, 10:12		#3
NiBa Member Nikolaos Babilas Join Date: Nov 2014 Posts: 37 Rep Power: 12	I think that for this problem it is needed to initialize separately water and air because of the grat difference in temperature. Can someone help me with this trial. I try to find something about advanced initialization but i can't! Sorry for my english again.

November 7, 2014, 17:59		#4
arindam New Member Arindam Singha Join Date: Apr 2014 Posts: 8 Rep Power: 12	I have exactly same problem, I was running a boiling model. First run liquid water through the model to get the temperature right, then introduce vapor phase, that way you get convergence easily. Also try patching the temperature values at various zones, if you can hand-calculate them. Hope this helps.

December 2, 2023, 04:42		#5
Abdullah hassan New Member Abdullah hassan Join Date: Oct 2023 Posts: 9 Rep Power: 3	arindam, can you please make me understand how to first only run the water and then Introduce the vapor?