# Opening BC for multiphase problem

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 October 25, 2005, 11:06 Opening BC for multiphase problem #1 John Guest   Posts: n/a Hi, all Does someone have expeience of defining an opening BC for a gas-liquid phase problem? It seems that I need to input both gas liquid velocities. However I do not know that. Please give some comments, Thanks! Best regards! John

 October 25, 2005, 11:22 Re: Opening BC for multiphase problem #2 Rui Guest   Posts: n/a Hi, Whether it's a multi-phase or a single-phase problem, on an Opening BC you may input the pressure instead of velocity. Take a look at the Documentation, Solver Modelling - Boundary Condition Modelling - Opening, and Solver Theory - Basic Solver Capability Theory - Boundary Conditions - Opening Regards, Rui

 October 25, 2005, 11:37 Re: Opening BC for multiphase problem #3 John Guest   Posts: n/a Hi, Rui Thanks for your reply. Yes, I can choose to input pressure, however in that case I need to input volume fractions of gas and liquid as well. I also need to know the values of the additional variables at opening location, which I do not know. Thanks! John

 October 25, 2005, 12:46 Re: Opening BC for multiphase problem #4 Rui Guest   Posts: n/a Hi, The volume fractions and the additional variables values at the Opening BC will only be used for flow into the domain. If in your Opening BC there is actually flow into the domain, you have to know the volume fractions and the additional variables values that are flowing into your domain. But there's another option which isn't mentioned in the Documentation, and which you may only be set editing the .ccl file: BOUNDARY : out Boundary Type = OPENING Location = out BOUNDARY CONDITIONS : MASS AND MOMENTUM : Option = Extrapolation END END END However, this was told to me by the CFX support: "Note that this type of treatment of the b.c. should not be used for a steady state case, as it is not constrained enough"I never used this type of definition, so I don't know if it works well or not. Regards, Rui

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