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October 18, 2015, 18:50 
Fluide Flow aroud a cylinder

#1 
New Member
Badr badro
Join Date: Oct 2015
Posts: 6
Rep Power: 2 
Dear all, Hello
I want realise a 2D simulation of a turbulent flow of a fluide, wind fo example around a cylinder. So the wind flow is turbulent. The turbulence model chosen that i think is the best, is the Shear Stress Transport (SST) Reynoldsaveraged NaviereStokes (RANS) model. * the dimensions are :  The solution domain => L=90 m ; H= 30 m  the Cylindre has a diameter of D= 10 m ; and it is situated in midle of the domain I impose 17 m/s velocity in the inlet section. The problem is that I have no convergence at least, I give a big number of iterations (sometimes more than 10 000 iteration ) without that the programme telling me the convergence. So  How much time can this kind of simulation take to achieve convergence ?  Should I give more and more iteration in order to achieve convergence ?  Can take results and consider them as meaning results without having convergence ? your help please ! 

October 21, 2015, 08:25 

#2 
Member
Devesh Baghel
Join Date: Mar 2009
Posts: 67
Rep Power: 9 
Hi,
1. What is your goal to do this simulation. 2. Can you please post some pictures of mesh, residuals, contour plot etc. 3. What is Y+ around cylinder ? Devesh 

October 21, 2015, 19:48 

#3 
New Member
Badr badro
Join Date: Oct 2015
Posts: 6
Rep Power: 2 
Thanks for replying
can you please join the thread below Problem of convergence simulation of flow wind around cylinder I just gived more information about the problem there. thank you very much. 

October 21, 2015, 23:37 

#4 
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liusuanyatong
Join Date: Jun 2015
Posts: 7
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You can't tell the converage by program.Sometimes，Your result is converage but residual curve isn't down to your request for some reason.You should check that mass flow of inlet equal mass flow of outlet，or not？and you should detect some physical quantity of a point，and check whether the physical quantity is steady finally.These method can judge the coverage.Residual curve isn't the only.But if the Residual curve is up constantly，the result maybe wrong.I'm sorry my English is poor.I hope my answer can help you.


October 22, 2015, 22:21 

#5 
New Member
Badr badro
Join Date: Oct 2015
Posts: 6
Rep Power: 2 
Hi, thanks vey much
Of course your replies are important for me and all this interactivity on the Forum, so that gives me more ideas and pushes me to learn more, I m just beginner In CFD, and by the way you dont have to be sorry my English is more poor that yours So how can I compare the mass flow of the inlet with that of the outlet ? I dont understand What you mean by detecting some physical quantity of a point，and checking whether the physical quantity is steady? 

October 27, 2015, 05:58 

#6  
New Member
liusuanyatong
Join Date: Jun 2015
Posts: 7
Rep Power: 3 
Quote:
I can't upload the pictrue that I grab from fluent.The conpare them in Report. You can see whether the mass flow is equal.The physical quantities mean velocity,temperature and so on.You can do the same things as massflow.If the physical quantity is steady of a point,You can think the result is converage. 

Tags 
convergence, simulation cylinder, turbulent flow 
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