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January 15, 2010, 06:41 |
Boundaries definition
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#1 |
Senior Member
Join Date: Jan 2010
Posts: 110
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Hi all:
Is there any way in a free-surface model to don`t specify the normal speed in the inlet boundary? Well, of course I need to specify initial values but i don`t want to specify that value (the normal speed) in the boundary. I just want to give an initial height of the water (in the upstream and downstream sections) and I hope that the model converges to some discharge. Is this possible? How can I create periodic boundary conditions? Many thanks |
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January 15, 2010, 23:15 |
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#2 | |||
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,728
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Quote:
Quote:
Quote:
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January 16, 2010, 14:12 |
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#3 |
Senior Member
Fatema Zandi Goharrizi
Join Date: Mar 2009
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Salam = Hi
you can use static pressure or total one I think I'm working with a project with the same definition for inlet but not periodic · I used static pressure and defined a function in expression. see tutorial 7 , I used the same function for UpPres and put it for static pressure. in this tutorial you can learn how specify the Hd hydraulic head. see expressions and use the step function. learn about it in guide. I have version 11 good luck |
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January 16, 2010, 14:18 |
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#4 | |
Senior Member
Fatema Zandi Goharrizi
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Quote:
salam = hi in tutorial 7 it used outlet water height if i'm right.
zandi Last edited by zandi; January 17, 2010 at 07:03. |
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January 16, 2010, 16:13 |
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#5 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
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From memory improvements to periodic boundary conditions were made, allowing you to set an inlet and outlet to be linked with specified flow rate or pressure drop or a few other options.
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January 18, 2010, 04:52 |
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#6 |
Senior Member
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Hi All.
Thanks a lot for your suggestions. Yes ghorrocks I am using V12. I have already saw in the documentation how to set the periodic boundaries (it`s called domain interface isn`t it?). However I still have one question. In the option Interface model I have 3 options : mass flow rate, none and pressure change. At the present moment I have chosed none...Is this a problem? Setting periodic boundary conditions there is no need to define inlet boundaries with velocities isn`t it? Zandi, I am going to see tutorial 7. Regards |
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January 18, 2010, 05:00 |
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#7 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
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A periodic boundary is a type of domain interface. There are other types as well.
The three options relate to how the flow goes out one end and comes in the other. Mass flow rate means the mass flow will be set to your specified amount. Pressure means the pressure rise/drop over the boundary will be set. None means all flow variable map over. If your model is one chamber in a cascade of many identical chambers then periodic boundaries can be a good approach. You the use a pressure or mass flow periodic boundary to drive a flow through the domain and you will get the representative flow in the chamber. In your case I assume you have a mass flow rate, so in this case you will not need to set velocities or fluid heights. However an initial guess which is close may help convergence. |
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