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 September 11, 2008, 16:51 Greatly Urgent!!!!! Help me please. #1 MK Guest   Posts: n/a Dear Everybody I am simulating an unsteady flow through a pipe. The cross-sectional area reduces to 10 percent in the middle. I mean the area is one tenth of the area at the begining or the end of the pipe. I can not converge the problem in any method. I try changing any possible parameter, but the problem diverged. Could you please help me. I should also mention that I analyzed the problem very well with 50 percent area reduction. I need your help as soon as possible. Thanks a lot.

 September 12, 2008, 08:28 Re: Greatly Urgent!!!!! Help me please. #2 K.K.Singh Guest   Posts: n/a Try SIMPLEC if not used so far.

 September 12, 2008, 13:27 Re: Greatly Urgent!!!!! Help me please. #3 MK Guest   Posts: n/a Dear K.K.Singh I appreciate your answer. I used the SIMPLEC, but the problem did not converged. If you have any other idea please make me known. Do you know where I can refer to? Thanks a lot.

 September 12, 2008, 16:37 Re: Greatly Urgent!!!!! Help me please. #4 K.K.Singh Guest   Posts: n/a Give more details like grids used, turbulence model, under relaxation factors etc. Have u tried node based gradient option instead of cell based gradient option? Try to refine mesh near the constriction by using adapt mesh command.

 September 13, 2008, 01:57 Re: Greatly Urgent!!!!! Help me please. #5 MK Guest   Posts: n/a Dear K.K.Singh I have used the Hex/Cooper mesh in the volume. The viscous model is laminar, but as I have checked the Reynolds number in the throat last night, it was over 10000, so the flow is turbulent. Does it make much error, if I use the laminar model for simulation? Under relaxation factors are set as default in Fluent. I mean pressure=0.3 , density=1 , body force=1 , and momentum=0.7. I should also mention that I have refined the mesh near the throat, but no improvement occured. By the way, where can I change node based gradient option to cell based gradient option? Thanks a lot.

 September 13, 2008, 02:05 Re: Greatly Urgent!!!!! Help me please. #6 MK Guest   Posts: n/a I forgot an item. If I need to use the turbulent model, please introduce the best one and tell me how to set related parameters? Regards.

 September 20, 2008, 06:51 Re: Greatly Urgent!!!!! Help me please. #7 Madusuthanan Guest   Posts: n/a you can set your turbulence model by using fluent menu DEFINE-Model-Visous, from that select the required turbulance model, The most used model is K-epsilon 2 equation model.Since you are dealing with pipe problem you have set the turbulence intensity and Hydarulic diameter in your boundary condition panel.

 September 29, 2008, 15:19 Re: Greatly Urgent!!!!! Help me please. #8 azadhoor Guest   Posts: n/a Use finer mesh.

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