# Help con BC

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 January 3, 2008, 11:04 Hi, Im new using OpenFoam. I d #1 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 Hi, Im new using OpenFoam. I dont have much experience in CFD neither... just doing some work for university. Currently, Im modelling a big hole in a surface (copper open mine, about 4 kms long) and at this point I need to impose atmospheric conditions for the wind. Here is the mesh: http://img176.imageshack.us/my.php?image=meshsd8.png The problem is when I set 'inlet' condition for the circular boundary, the next error appears: Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow. Total flux : 4.2258e+06 Specified mass inflow : 7.50341e+07 Specified mass outflow : 7.85048e+07 Adjustable mass outflow : 0 I have to impose a constant field of velocity on the boundary, and I as far as I understand, the error says there is no conservation of flow. On top, I set 'symmetryPlane' condition and 'wall' to the ground. Im still using icoFoam, just to get familiar with the libraries and parameters. So.. the main question is.. what are the best BC for this problem? I appreciate any help Sorry for my english... Im from Chile.

 January 3, 2008, 12:09 Hi Manuel, Did you try to do #2 Senior Member     Dragos Join Date: Mar 2009 Posts: 647 Rep Power: 11 Hi Manuel, Did you try to do what the solver suggests: run potentialFoam to initialize the outflow? Dragos

 January 3, 2008, 14:06 I dont know what it exactly me #3 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 I dont know what it exactly means... can you tell me what to do plz? If I run potentialFoam with the same conditions, same as before I get: Create mesh for time = 0 Reading field p Reading field U Calculating potential flow --> FOAM FATAL ERROR : Continuity error cannot be removed by adjusting the outflow. Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow. Total flux : 1e-300 Specified mass inflow : 7.50341e+07 Specified mass outflow : 7.85048e+07 Adjustable mass outflow : 0 From function adjustPhi(surfaceScalarField& phi, const volVectorField& U,const volScalarField& p in file cfdTools/general/adjustPhi/adjustPhi.C at line 111. FOAM exiting I dont understand what Im doing wrong

 January 3, 2008, 17:08 Hello again Manuel, Would it #4 Senior Member     Dragos Join Date: Mar 2009 Posts: 647 Rep Power: 11 Hello again Manuel, Would it be possible for me to have a look at your case (download it from some website)? Dragos

 January 3, 2008, 23:17 I would really appreciate your #5 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 I would really appreciate your help, Im sending it tomorrow, it is in the office. You need the complete folder right? Ill upload it on a website at night... thx!! Manuel

 January 4, 2008, 09:26 OK, I sent to your email the U #6 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 OK, I sent to your email the URL with the folder 'chuqui', the complete case. Thx again!!

 January 4, 2008, 11:09 Hi Manuel, I just looked brie #7 Senior Member     Dragos Join Date: Mar 2009 Posts: 647 Rep Power: 11 Hi Manuel, I just looked briefly through your case and ... I could not find any outlet boundary condition. It is always a must to have an outlet if you have an inlet... hmm unless you have a mass sink somewhere in your domain. Where are you supposed to have an outlet? Dragos

 January 4, 2008, 11:30 What Im trying to model is the #8 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 What Im trying to model is the flow of wind... so I supposed that imposing constant condition on boundary for velocity... the flow would just 'pass' through the Mine doing some strange behavior... is that so bad? That's why I asked about the BC's for this problem, how can I simulate just the flow of wind through the surface? By the way, I tried to set the 'top' boundary as outlet, but most part of the wind went there... so ugly... I tried to split the 'inlet_velocity' face (to make the inlet & outlet surface), but as you see the mesh is complicated & I dont know how to do that... Any suggestions?

 January 4, 2008, 12:25 Ok, so if I understand correct #9 Senior Member     Dragos Join Date: Mar 2009 Posts: 647 Rep Power: 11 Ok, so if I understand correctly you want to simulate the flow over an irregular surface (the bottom of your domain). If this is true, then one solution is to split in 2 the cylindrical surface that is right now an inlet, and transform it into an inlet and an outlet. This implies that you know already the direction of the flow. I don't know how to do the split with OpenFOAM utilities, but I suspect you have used Gambit to produce the mesh, and there, you can do the splitting very easy. Dragos

 January 4, 2008, 12:39 That's exactly what I said htt #10 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 That's exactly what I said and yes, the mesh was made in Gambit (not by me) but then exported to Fluent to make the .msh archive. I tried to read in Gambit that file... but I couldnt... some compatibility problems I think. So, if you suggest to make the splitting.. Ill put my efforts there. Thanks!

 January 4, 2008, 14:24 Nop, definitely I couldnt http #11 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 Nop, definitely I couldnt nobody here uses here Fluent or Gambit... could you do the splitting for me plz? I uploaded the msh file... so if you could... that would be great! and I promise not to bother you anymore Manuel

 January 4, 2008, 16:56 I'll try, but I cannot do it n #12 Senior Member     Dragos Join Date: Mar 2009 Posts: 647 Rep Power: 11 I'll try, but I cannot do it now. Most probably on Monday. Also I need to know how to split. Can you make a sketch showing which side will be the inlet and which the outlet? Dragos

 January 7, 2008, 08:28 OK, here you are: http://im #13 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 OK, here you are: http://img292.imageshack.us/img292/2425/mesh2ut0.png They told me that wind flows from north to south in the morning and all the way around at night. So, I made the simplest split; two approximately symmetric hemispheres according to the real orientation. It doesn't really matters which of the them you choose as 'inlet', I think we can change it anyways in OpenFoam. Thanks again!! Manuel

 January 10, 2008, 15:02 Manuel, Correct me if I am #14 New Member   Yingfeng Shen Join Date: Mar 2009 Location: Finland Posts: 8 Rep Power: 8 Manuel, Correct me if I am wrong. I have never done any wind simulation. But can't you set a fixedValue boundary condition at the top, something like uniform value (5,0,0) assuming your top surface normal is the z axis. Then the deep hole wall as well as the bottom will have fixed zero velocity. This would be like the cavity example in the tutorial. Yingfeng

 January 10, 2008, 16:29 Hm... but I need to simulate w #15 New Member   Manuel Larenas Aravena Join Date: Mar 2009 Location: Santiago, Chile Posts: 15 Rep Power: 8 Hm... but I need to simulate wind coming from outside and passing over the mine... in the cavity is just an internal flow. Am I right? Manuel

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