# Nonlinear problem with almost no implicit terms

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 June 13, 2006, 16:32 Hi Rafal! At first the equa #2 Assistant Moderator   Bernhard Gschaider Join Date: Mar 2009 Posts: 3,971 Rep Power: 41 Hi Rafal! At first the equations looked to me like something I have seen before (two phase flow in porous media), but then again they didn't. Questions I have at a first glance: - dimensionless velocities? (I know physicicsts do it all the time, usually by normalizing with c, but engineers?) - the relative densities of liquid and gas go into K? - which leads to the next question: both (gas and liquid) are incompressible? - in (2) you wanted to write K/(sqrt(A) grad(A))? Otherwise I can't match the dimensions. - You are looking for a stationary solution? I think it can be done in OF, but I'm not aware of a solver in the distribution that is similar to your problem. __________________ Note: I don't use "Friend"-feature on this forum out of principle. Ah. And by the way: I'm not on Facebook either. So don't be offended if I don't accept your invitation/friend request

 June 14, 2006, 06:02 Hi Bernhard, Thanks for ans #3 Member   rafal zietara Join Date: Mar 2009 Location: Manchester, UK Posts: 60 Rep Power: 9 Hi Bernhard, Thanks for answer. I didn't want to provide to much details about the system not to complicate the problem to much. Good intuition. Those equation describe motion of liquid in a soap foam (drainage of water from a foam due to gravity), which is similar to flow in porous media in a sens that we have also channels in which our fluid flows through static material. In this case material consist of close packed air bubbles moving upwards (velocity of gas v in eq.(2)). Channels are located in the junction of three bubbles. First of all word of apology. I mistook dimension of K which is m (and NOT m-1 as i wrote above), sorry for confusion. To give you more details about the equation and provide more comprehensive description of the problem i have prepared it in attachment with derivation of equations. derivation.dvi Velocity of gas (v) i assumed is influenced by water drainage. v is calculated separately (done this before). in this discussion we can assume is known. I assume also that both fluids (gas,liquid) are incompressible. I am looking for steady state solution. Why normalisation to get dimensionless velocities? A (cross-section area through channel) in case of foam is in order of 10-5 with velocities in the order of 10-1 may give numerical problems. I do not stick to this normalization it is only idea i read somewhere about. If it is a problem i can remove it. Do not hasitate to ask for more details. All help is appreciated. Thank you in advance for all suggestions and i invite everyone to discussion. rafal

 June 14, 2006, 06:09 IS: Velocity of gas (v) i assu #4 Member   rafal zietara Join Date: Mar 2009 Location: Manchester, UK Posts: 60 Rep Power: 9 IS: Velocity of gas (v) i assumed is influenced by water drainage SHOULD BE: Velocity of gas (v) i assumed is NOT influenced by water drainage

 April 24, 2008, 08:11 hi all, i am supposed to modi #5 Member   davey david Join Date: Mar 2009 Posts: 54 Rep Power: 9 hi all, i am supposed to modify a code into a dimensionless one.how do i go about it? thanks in advance

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