# How to apply a function as boundary condition

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 January 13, 2009, 04:48 Dear Foamers, I'm a newbie #1 New Member   Chuang Gao Join Date: Mar 2009 Posts: 12 Rep Power: 10 Dear Foamers, I'm a newbie here. For my question, I want to add a function with time and circumferential position as the variables for the inlet boundary condition. The study object is a circular ring and the inlet radius is R2 while the outlet one is R3. The inlet condition should be V2=V_mean+sin(Omega*t+phi), in which the Omega is the angular velocity and a constant in this expression. V_mean and phi (initial position) are also constants, t is the time for unsteady calculation. Can such kind of boundary condition be given? For fluent, this is very easy through using the UDF. Thanks all.

 January 15, 2009, 04:49 i need to run a combustion pro #2 New Member   VIJAYAKUMAR R Join Date: Mar 2009 Location: BANGALORE, KARNATAKA, INDIA Posts: 20 Rep Power: 10 i need to run a combustion problem.... i used XI-foam as solver, while running some errors are coming... i need to know which solver is good for combustion problem.. and few guidelines for solving combustion problem.

 January 15, 2009, 06:07 OK. Let's see: http://openfoam #3 Assistant Moderator   Bernhard Gschaider Join Date: Mar 2009 Posts: 3,997 Rep Power: 42 OK. Let's see: http://openfoamwiki.net/index.php/Ho..._Message_Board You hit the points 1,2,3,5 and 7. Not a bad score. But it means it is very unlikely that you'll get an answer. No offense. __________________ 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

 January 15, 2009, 06:53 Ok, I'd like to use the DNS so #4 New Member   Chuang Gao Join Date: Mar 2009 Posts: 12 Rep Power: 10 Ok, I'd like to use the DNS solver in OpenFoam 1.5. Is this information clear?

 January 15, 2009, 07:14 Hi Chuang I am certain that #5 Senior Member   Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Deltares, Delft, The Netherlands Posts: 1,740 Rep Power: 29 Hi Chuang I am certain that Bernhard's comment was not minded on you, but on the person who hijacked the thread. As a answer to your question, I cannot see any spatial variation in your boundary condition, thus you might be able to achieve what you are after by applying "timeVarying". I am not at a OF-machine at the present, but you should be able to find it using the search function. Best regards Niels __________________ Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.

 January 15, 2009, 15:47 Hi Chunag! Niels is right. #6 Assistant Moderator   Bernhard Gschaider Join Date: Mar 2009 Posts: 3,997 Rep Power: 42 Hi Chunag! Niels is right. I meant the other poster. Sorry if I upset you Bernhard __________________ 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

 January 15, 2009, 22:26 Hi, Niels and Bernhard, If #7 New Member   Chuang Gao Join Date: Mar 2009 Posts: 12 Rep Power: 10 Hi, Niels and Bernhard, If you plot the function I posted, it has nonuniform distribution along the circumferential direction. for a function, such as sin(n*theta) is a kind of flower function. theta is the circumferential coordinate. I've noticed a poster which talked about parabolic inlet boundary condition. But there do existed some differences. Can anybody give me a hint?

 January 18, 2009, 16:03 Hi Chuang There is not prob #8 Senior Member   Niels Gjoel Jacobsen Join Date: Mar 2009 Location: Deltares, Delft, The Netherlands Posts: 1,740 Rep Power: 29 Hi Chuang There is not problem in specifying boundary conditions, which are varying both in space and time. I you want to give a Dirichlet condition, then I would recommend you to find parabolicInlet-BC, which you will be able to find on this forum. This you should be able to modify to the purpose you are considering. When you have implemented your own conditions just compile the BC using the wmake-procedure, link the BC to the solver of your choice, and you should be well off. Good luck, Niels __________________ Please note that I do not use the Friend-feature, so do not be offended, if I do not accept a request.

 January 19, 2009, 19:45 Hi Niels, Thx for your kin #9 New Member   Chuang Gao Join Date: Mar 2009 Posts: 12 Rep Power: 10 Hi Niels, Thx for your kind help! I'll try it and post my results here. Best Regards, Chuang Gao

 February 12, 2009, 11:22 Hi everybody, I'm dealing wit #10 Member   Andrea Petronio Join Date: Mar 2009 Location: Trieste, Italy Posts: 39 Rep Power: 10 Hi everybody, I'm dealing with boundary condition as function of a calculated scalar fields. I think to derive it from a fixedValue bc. Someone have already done something similar?

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