# capillary tube simulation

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 June 25, 2014, 20:37 capillary tube simulation #1 New Member   MI Join Date: Jan 2014 Location: Michigan Posts: 11 Rep Power: 4 Hi all, recently i am doing a capillary tube simulation by FLUENT. capillary tube dimension and simulation result are showing below(unit is mm).dimension.jpggeometry.jpg For the parameters setup, basically i follow Fluent tutorial about VOF model. 1. i use pressure-based, transient solver. 2. VOF model is used. and scheme is explicit scheme. 3. water and air is used as material. air is primary phase and water is secondary phase. wall adhesion option is selected and surface tension coefficient is 73.5dyn/cm. 4. I use pressure inlet and pressure outlet. for both of them, gauge presseue is 0. and water volume fraction is 1 at inlet and 0 at oulet. 5. For wall, contact angle is 30deg. 6. for the solution method, i use PISO scheme. 7. since i meet some convergent problem at beginning, i change all the relaxation factors to 0.25. But the result is weird.result.jpg i expect water flow would go downward when it pass the tee. But it go upward... do i miss gravity setup or the geometry itself cause this problem??.. help!!help!! thank ahead

 June 30, 2014, 06:38 #2 New Member   Márton Stibrányi Join Date: Mar 2014 Location: Hungary Posts: 7 Rep Power: 4 What is the BC at the bottom? You should define pressure outlet for both the top and bottom boundary. Enable gravity and specify the operating density to 0. What are the initial conditions? Air everywhere?

June 30, 2014, 08:20
#3
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Quote:
 Originally Posted by stiboo What is the BC at the bottom? You should define pressure outlet for both the top and bottom boundary. Enable gravity and specify the operating density to 0. What are the initial conditions? Air everywhere?
hi!thank you for your reply.boundary condition is pressure inlet and outlet. and initial condition is air everywhere.but i did not enable gravity. i will try that today!
and also i think my geometry may not be proper. i will try to change it a little bit.

 June 30, 2014, 10:55 #4 New Member   Márton Stibrányi Join Date: Mar 2014 Location: Hungary Posts: 7 Rep Power: 4 I meant that you should define pressure outlet at both end of the vertical tube.

June 30, 2014, 11:07
#5
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MI
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Quote:
 Originally Posted by stiboo I meant that you should define pressure outlet at both end of the vertical tube.
the vertical bottom end is design to be a closed end.

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