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May 2, 2010, 03:56 |
Dambreak
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#1 |
New Member
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Does anybody know how to model dam-break? i've attach the picture
there is no inlet or outlet and the volume of water is constant. |
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May 2, 2010, 07:03 |
???
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#2 |
New Member
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it has a simple geometry but i don't know how to set boundary conditions ????????
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May 2, 2010, 07:19 |
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#3 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
This looks straight-forward. Have you done the tutorial example for free surface flow over a bump? That should give you the main idea of how to do it.
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May 2, 2010, 07:26 |
?
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#4 |
New Member
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yea, i've done tutorials but this is special model, there is no inlet and outlet, i made my model in free surface with 2 fluids by volume fraction equation
how do you think? |
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May 2, 2010, 07:37 |
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#5 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
No inlet and outlet makes it much easier. You will still probably need an air opening on the top to let air go in and out.
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May 2, 2010, 07:42 |
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#6 |
New Member
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honey i've already made a simple 2-D model, without inlet and outlet; just an opening above! i don't know why it doesn't run!
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May 2, 2010, 07:52 |
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#7 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
What is the error message? Post the output file.
Honey? I have been called many things in CFD but never honey |
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May 2, 2010, 07:56 |
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#8 |
New Member
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ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: | | Floating point exception: Overflow " you dont know how your help is valued to me!" |
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May 2, 2010, 08:18 |
out file
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#9 |
New Member
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the out put file is not valid to upload
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May 2, 2010, 17:26 |
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#10 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
Floating point exception means that the solver has diverged badly. You need to improve the numerical stability of the simulation. This can be caused by lots of things, but in rough order I would check:
1) That the physics is correct 2) That you time step is small enough 3) That the mesh quality is high enough 4) If using high order differencing switch to low order (but just for debugging, once things are working go back to high order differencing) |
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May 3, 2010, 02:28 |
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#11 | |
Member
Ali Torbaty
Join Date: Jul 2009
Location: Sydney, Australia
Posts: 72
Rep Power: 16 |
Quote:
1- try to refine your mesh 2- In your intial conditons, instead of using automatic options try to provide information (e.g. velocity, hydrostatic pressure,...) 3- start with very small time step in cases other than dam break (e.g. flow over a spillway), I found, it is much easier to fill the domain with water and let model drain out extra water while converging toward steady condition. |
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May 3, 2010, 06:21 |
this is the error message!
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#12 |
New Member
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to check anything!!!
a 2-D model; no inlet or outlet; just an opening with air; initials: velocity components are zero; hydrostatic pressure is applied; homogeneous turbulent model, time step=.001s & total time=2s, turbulent eddy dissipation checked and this is the result: +--------------------------------------------------------------------+ | ERROR #001100279 has occurred in subroutine ErrAction. | | Message: | | Floating point exception: Divide by zero | | i think the mesh size is small enough! now what? ((((( |
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May 3, 2010, 07:46 |
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#13 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,729
Rep Power: 143 |
Divide by zero errors can come from many sources - you will have to find it. Try removing the hydrostatic pressure initial condition, removing gravity, running a laminar model as a few ideas to try to find the source of the error.
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September 19, 2011, 03:52 |
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#14 |
Member
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I would like to mention that the first two screen shots are showing the results from a smooth particle hydrodynamic ( SPH ) method not a VOF/FVM method
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