I am simulating a stirred tank. First for one phase and in the next step for 2 phases (gas dispersion in water using the Algebraic Slip Mixture Model (ASMM).

I want to define the top surface of the liquid as free surface.

how shoud the top surface of the tank be defined in Gambit (outflow? wall? outlet pressure??)

many thanks

Mounir

define it as wall, but set in FLUENT as specified stress, set 0 for all variable

Hi Mounir,

I am solving a problem similar like your's. If you want to simulate the top surface of the liquid as a free surface you must use two-phase model. The first phase is the liquid in the tank and the second phase is the air above the liquid surface. So, you need to modify your grid file so that the air to be included above the reactor. After this you can read your modified grid file into Flient and can use some of multiphase model - VOF by example. It is convenient to define the air as a primary phase and the water as a secondary one. After the initialiazation of the solution you must patch the water-liquid fraction value 1 and start the iterations process. Keep in mind that the multuphase calculations are very CPU intensive. If you have any other questions, please do not hesitate to ask me. I hope I can answer to you.

Please go and check the example problem in the fluent tutorial guide : vol 3. Its about water and air in a spinning bowl. It should provide as a good start to set up your VOF problem.

you have to define it has symmetry boundary condition. if you are using algebraic slip model u cannot have transient conditions and also u cannot have mixture of particles or discrete phase. i would like you to check the same.

[Yapoo]

Originally Posted by Peter Staykov
;95458

Hi Mounir,

I am solving a problem similar like your's. If you want to simulate the top surface of the liquid as a free surface you must use two-phase model. The first phase is the liquid in the tank and the second phase is the air above the liquid surface. So, you need to modify your grid file so that the air to be included above the reactor. After this you can read your modified grid file into Flient and can use some of multiphase model - VOF by example. It is convenient to define the air as a primary phase and the water as a secondary one. After the initialiazation of the solution you must patch the water-liquid fraction value 1 and start the iterations process. Keep in mind that the multuphase calculations are very CPU intensive. If you have any other questions, please do not hesitate to ask me. I hope I can answer to you.

Hi Peter
in the same problem but in the open channel,what is the best bounday condition for outlet?
if it's pressure outlet, so what about pressure gauge value?

[crispysalt]

Hi,
How do I modify my gambit drawing so that the air can be included above the reactor? If I have an open shell reactor how should I do?

Thanks!

[Omarspace]

Hi all
I am sorry but When I searched to model my free surface i found only Open channel flow which is horizontal how to define it as vertical ? Also what if i don't know my free surface dimensions I am modeling falling water film