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-   -   Boundary Conditions for a Venturi in Gambit (http://www.cfd-online.com/Forums/fluent/71000-boundary-conditions-venturi-gambit.html)

KAWICGB December 11, 2009 15:24

Boundary Conditions for a Venturi in Gambit
 
I need help assigning boundary conditions for a venturi I have 3-D modeled and meshed in Gambit. My known is the velocity at the inlet. I would like to find the pressure differential between the inlet and the throat and between the inlet and the outlet.

How I modeled the venturi:
-I modeled the venturi by inserting points in the following configuration

*...... *....... *..... *
...........* ...*
* ........................*

-I then connected the points to form lines
______ .........._____
| ........\_____/...... |
|_________________|

-From here I used the "Wireframe" function to connect the lines to form 1 face. Then I revolved the face to get a single solid

........___P1__.............. __P3__
.......|........... \__P2__/........... |
V -> |..................................... |
.......|............. ______............|
.......|_______/ ..........\______|

I have the 1st vertical face assigned as the velocity inlet. I have the horizontals and diagonals assigned as walls.

How do I assign the boundary conditions to get P1, P2, and P3

Thanks in advance!

jiangtao167 December 13, 2009 18:18

venturi tube is used to obtain the velocity of flow. actually the velociy in normal direction to the axis at p is zero,so i think wall with velocity equal inlet velocity for p1&p3 is suitable,and the bc. at p2 is wall with velocity caculated by using continuity eq.
u can also try symmetry BC. which is identical with moving wall mathematically
but i have a question how you kown the inlet velocity of a venturi tube

KAWICGB December 13, 2009 18:37

I am designing a venturi that will be used to measure the volumetric flow rate. The differential pressure will be monitored to insure the correct inlet velocity and volumetric flow rate. I've done the calculations, but now I want to simulate it and verify my work. I also want to look at the pressure regain from P2 to P3.

KumarP December 15, 2009 05:35

venturi
 
Hi
I think its better to use cylinder and frustum for creating the venturi (top down approach), unless u are particular about the bottom up approach. To get the pressure differential, create isosurfaces and find the static pressure difference. Hope this helps


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