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Two Inlets with Different Velocities

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Old   January 26, 2010, 01:07
Default Two Inlets with Different Velocities
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Ch'ng Huey Khim
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Hi all,

I have 2 inlets at different walls with different velocities.
How can i simulate the air flow within the domain with this 2 inlets allowing air entrance simultaneously?
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Old   January 26, 2010, 01:55
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Maxime Perelli
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define each BC as separate velocity inlets
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Old   January 26, 2010, 02:05
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Hi max,

Thanks for replying, i've already define them as different velocity inlets with their respective velocity.
Problem is i found that when come to "Solution Initialization", i can only choose 1 inlet to initiate with.
I'm wondering how can i compute from 2 inlets in the same initialization.
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Old   January 26, 2010, 05:06
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The following might work.

First the simple one. Assuming that one inlet is in the lower half and one is in the upper half of your domain:

- initialize in the usual way from the lower inlet
- adapt > region: select a region that includes the upper half of your domain. Press 'Mark'.
- solve > initialize > patch: select either X or Y Velocity (wathever you want to set), enter the value associated with the upper inlet, and under Registers to Patch select hexahedron-r0 (this is the region you marked). Press 'Patch'

This would be the fast way. Still, this may give you akward initial conditions. A nicer solution would be to define a linear Field Function that matches both boundary conditions:

- initialize in the usual form from an inlet
- define > custom field functions: play around with this window to define your linear field function that matches both boundary conditions. Name it 'xvelocity0' or something.
- solve > initialize > patch: select X Velocity, checkbox Use Field Function, select xvelocity0, and select Zones to Patch: fluid.

good luck!

Last edited by jack1980; January 26, 2010 at 05:07. Reason: spelling error
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Old   January 27, 2010, 05:09
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I think you are unaware of the idea of initialization.... this is a step for giving a kind of preliminary values for the iteration process... that's why it is not possible to guess from multiple inlets.... it is like you know the solution!!!!!!
It is possible to initialize from the "whole domain"... try using this....
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Old   January 27, 2010, 08:20
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Initialize from whole domain?
How am i gonna set the boundary condition such as inlets velocities?
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Old   January 27, 2010, 08:38
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Initialization is the final step before Iteration.... setting BC has to be done before that.... in the BC panel ... there you must find your boundary and to set up the values....
Are you sure you didn't give one and the same name to the boundaries?
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Old   January 27, 2010, 08:55
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I did set them as different boundary names although they both of type velocity inlet.
Meaning to say i just need to key in the velocities, then in initialization tab, i select "Compute from" Interior-#?
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Old   January 27, 2010, 08:58
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post a picture of the BC tab...... I am not sure I can understand the problem
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Old   January 27, 2010, 09:13
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Quote:
Originally Posted by khimkhim View Post
Hi max,

Thanks for replying, i've already define them as different velocity inlets with their respective velocity.
Problem is i found that when come to "Solution Initialization", i can only choose 1 inlet to initiate with.
I'm wondering how can i compute from 2 inlets in the same initialization.
From here I understand that you define different BC velocity inlets... and you want to initialize the computation from the 2 inlets..... that's why I wrote my first reply....
Now you are telling me something different?!?!?!?!?!?
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Old   January 27, 2010, 09:26
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Ya, you understand my question correctly a, sorry i make it sounds like something else,
What i meaning to say is that i've already set the velocities in Define - Boundary Condition. When it comes to Solve - Initialize stage, i nd to select a boundary to "Compute From" right?
Here is where i don't understand what you mean by "whole domain". Does it mean "all-zones"?
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Old   January 27, 2010, 09:32
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yes... all zones
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Old   January 27, 2010, 10:12
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I shall try then.
Really thanks a lot for the advice~
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