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December 11, 2012, 02:46 |
Cinema hall simulation
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#1 |
Member
Georgi Angelov
Join Date: Nov 2012
Posts: 78
Rep Power: 13 |
Hello,
I made a model of a hall in Gambit, meshed it after 1000000 tries, load it into Fluent and start to make a simulation. The project is at the University and it is a ventilation system of a cinema hall. My velocity inlets are at the top,lower top and the front wall,my outlets(outflows) are at the stairs.Velocity of the inlets 2 m/s, 2.3 m/s and 1.4 m/s. My professor told me that I have to get solution converged after about 400 iterations or 600 may be. I made 2100 iterations and I still cannot get solution converged. I set K-e viscous method with RNG. Flow,turbulence and energy equations, the discretization of momentum,turbulence kinetic energy,energy,dissipation rate and energy are second order upwind. I cannot figure out where is the problem, may be : 1.More iterations need 2.I change the steps of the pathlines and it shows a lot more pathlines. 3.I made a sweep surface at the stairs z=2.13 and the velocity is still low. Thank you in advance for your help. |
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December 11, 2012, 02:49 |
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#2 |
Member
Georgi Angelov
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http://www.2shared.com/photo/kNkYyvJ...terations.html
http://www.2shared.com/photo/tO7bPr3z/Grid.html http://www.2shared.com/photo/ZopNIMaO/Model.html http://www.2shared.com/photo/YWmf7fyE/Pathlines.html http://www.2shared.com/photo/ZCie20h...aces-z213.html http://www.2shared.com/photo/-PBuP57...y_vectors.html |
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December 11, 2012, 02:50 |
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#3 |
Member
Georgi Angelov
Join Date: Nov 2012
Posts: 78
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This are the pictures of the vectors,pathlines,the model and sweep surface.
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December 11, 2012, 02:53 |
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#4 |
Member
Georgi Angelov
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http://www.2shared.com/photo/kpbt-MlV/Temperature.html temperature pathlines
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December 11, 2012, 04:54 |
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#5 |
New Member
James Goodwin
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Location: Liverpool UK
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Have you tried starting with gravity at a lower order of magnitude and increasing it? (say 9.81e-3, then 9.81e-2 etc)
In simulations where gravity is a dependant variable (because of buoyancy etc) it can often struggle to converge with the gravity set at 9.81 right from the start. |
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December 11, 2012, 04:56 |
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#6 |
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James Goodwin
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Also: What are your under-relaxation factors?
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December 11, 2012, 05:17 |
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#7 | |
Member
Georgi Angelov
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Quote:
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December 11, 2012, 06:29 |
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#8 |
New Member
James Goodwin
Join Date: Nov 2012
Location: Liverpool UK
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The settings for gravity can be changed under "General" and the under-relaxation factors are under "Solution Controls". They determine the maximum amount any term can change in one iteration. Try reducing your momentum and pressure values in order to converge better.
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December 11, 2012, 09:40 |
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#9 | |
Member
Georgi Angelov
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Quote:
And about gravity I found it at Define>Operating conditions>gravity> to put gravitational acceleration of x,y or z ?? |
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December 11, 2012, 09:43 |
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#10 |
Member
Georgi Angelov
Join Date: Nov 2012
Posts: 78
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http://www.2shared.com/photo/vFFWu5I...-Momentum.html Before change
http://www.2shared.com/photo/-cdEnw-...um-After_.html After change |
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