# VOF model

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 April 15, 2005, 06:57 VOF model #1 Aly Guest   Posts: n/a hello i am trying to simulate the water-air interface in vertcial pipe. I am using unsteady state VOF model. I started my case as steady state single phase (water)simulation to have velocity field developed and later turn on the VOF model. The problem i am experinecing is: I define water velocity at the inlet (bottom of the pipe)at the start of the steady state run but when I switch to unsteady solution and turn ON the VOF model (geo-recons)..... to enter the boundary conditon for air velocity ( at the separate inlet) it does not display the box for the input of the air velocity but just the volume fraction box. Am i missing something? help needed. thanks

 April 15, 2005, 08:22 Re: VOF model #2 Aly Guest   Posts: n/a hi there I just looked at fluent manual VOF model option since single momentum equation is shared between the phases meaning only one velocity. If i have single phase steady state soltuion (i.e. developed velocity field for water) and than i introduce the VOF model .........I only need to specify volume fraction for other phase? now the question is that does it means that air velocity is calculated from the multiplication of volume fraction and water velocity during the calculations in cell? How am i suppose to take into account the entrance air velocity from separate inlet which is different than water velocity?

 April 15, 2005, 16:17 Re: VOF model #3 Srinivas Parimi Guest   Posts: n/a Hello Aly, To introduce separate velocities for two phases as inlet, I think you have to use the mixture model. In VOF you can only specify the primary phase velocity and the VOF of the secondary phase. all the best srinivas parimi

 April 22, 2005, 13:43 Re: VOF model #4 majid mirzabeagi Guest   Posts: n/a I am student and want to use VOF modle for thin layer of water that warm from below( marangoni- benard convection ) my qustion: 1- i want to see hexagonal cells in thin layer of water, when i select steady state botton after iteration,when i see my answer, there arent any phase , and all water convert to vapor, how can i do? 2- if it possible , send for me an example near to this situation,thank.