# Two Inlets with Different Velocities

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 January 26, 2010, 01:07 Two Inlets with Different Velocities #1 New Member   Ch'ng Huey Khim Join Date: Nov 2009 Posts: 11 Rep Power: 9 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?

 January 26, 2010, 01:55 #2 Super Moderator     Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,194 Rep Power: 33 define each BC as separate velocity inlets __________________ In memory of my friend Hervé: CFD engineer & freerider

 January 26, 2010, 02:05 #3 New Member   Ch'ng Huey Khim Join Date: Nov 2009 Posts: 11 Rep Power: 9 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.

 January 26, 2010, 05:06 #4 Senior Member   Jouke de Baar Join Date: Oct 2009 Posts: 125 Rep Power: 9 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! rajann_786 likes this. Last edited by jack1980; January 26, 2010 at 05:07. Reason: spelling error

 January 27, 2010, 05:09 #5 Senior Member     Svetlin Filipov Join Date: Mar 2009 Location: United Kingdom Posts: 176 Rep Power: 10 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....

 January 27, 2010, 08:20 #6 New Member   Ch'ng Huey Khim Join Date: Nov 2009 Posts: 11 Rep Power: 9 Initialize from whole domain? How am i gonna set the boundary condition such as inlets velocities?

 January 27, 2010, 08:38 #7 Senior Member     Svetlin Filipov Join Date: Mar 2009 Location: United Kingdom Posts: 176 Rep Power: 10 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?

 January 27, 2010, 08:55 #8 New Member   Ch'ng Huey Khim Join Date: Nov 2009 Posts: 11 Rep Power: 9 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-#?

 January 27, 2010, 08:58 #9 Senior Member     Svetlin Filipov Join Date: Mar 2009 Location: United Kingdom Posts: 176 Rep Power: 10 post a picture of the BC tab...... I am not sure I can understand the problem

January 27, 2010, 09:13
#10
Senior Member

Svetlin Filipov
Join Date: Mar 2009
Location: United Kingdom
Posts: 176
Rep Power: 10
Quote:
 Originally Posted by khimkhim 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?!?!?!?!?!?

 January 27, 2010, 09:26 #11 New Member   Ch'ng Huey Khim Join Date: Nov 2009 Posts: 11 Rep Power: 9 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"?

 January 27, 2010, 09:32 #12 Senior Member     Svetlin Filipov Join Date: Mar 2009 Location: United Kingdom Posts: 176 Rep Power: 10 yes... all zones

 January 27, 2010, 10:12 #13 New Member   Ch'ng Huey Khim Join Date: Nov 2009 Posts: 11 Rep Power: 9 I shall try then. Really thanks a lot for the advice~

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