# Open Water Tank

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 May 2, 2013, 08:20 Open Water Tank #1 New Member   Michael Bell Join Date: May 2013 Posts: 5 Rep Power: 4 Im currently studying the effects of jet flow in plunge pools which involves simulating firing a jet of water into an open surface water tank. I am currently struggling to set up my boundary conditions for the tank and was wondering if anyone had any good pointers. I'm trying to use the VOF method but thus far have had no success. Any help or points would be much appreciated.

 May 2, 2013, 08:53 #2 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,097 Rep Power: 16 I would go these boundary conditions: -velocity or mass-flow inlet for the water jet -pressure outlet for the ambient air -wall for the pool wall How do you plan to let the water leave the domain? Or do you want a rising surface / transient simulation? Maybe write a bit more about your setup and post some picture. What do you have for meshing. Is it 3d or 2d? __________________ The skeleton ran out of shampoo in the shower.

May 2, 2013, 10:30
#3
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Michael Bell
Join Date: May 2013
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The simulation is based on an actual experiment in which the water level remains constant so I've placed two outlets in the top corners of the tank. At the moment I have them as pressure-outlets. Do you think I should set them to outflow? I'm running the simulation in 2d and have currently have a 5mm sized quadrilateral mesh.

I'll attach an annotated screen shot of the tank.

The purpose of the simulation is to study the diffusion of the jet in the pool so once I have the initial tank set up I can easily vary the jets velocity and diameter.

Sorry for asking so many questions, this is the first time I have ever used the software. Thank you for your help so far.
Attached Images
 Tank Sketch.jpg (65.0 KB, 15 views)

 May 2, 2013, 10:37 #4 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,097 Rep Power: 16 1) What means "free water surface" at the top? Is this some kind of boundary condition? 2) It looks like you have water everywhere inside your domain. Why do you want to use the VOF model? __________________ The skeleton ran out of shampoo in the shower.

 May 3, 2013, 07:03 #5 New Member   Michael Bell Join Date: May 2013 Posts: 5 Rep Power: 4 By free water surface I mean that there is no rigid wall on the top of the tank and that the tank is open. I am unsure on what boundary conditions I should set that to? As for the VOF I was unsure on the process and thought it might be a valid method for analysis.

 May 3, 2013, 07:15 #6 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,097 Rep Power: 16 VOF is a multiphase model. You only need it, if you want to have water and air inside your domain. If you have just water, there is no need to use it. So what do you plan? __________________ The skeleton ran out of shampoo in the shower.

 May 3, 2013, 09:42 #7 New Member   Michael Bell Join Date: May 2013 Posts: 5 Rep Power: 4 For the purpose of my work the analysis does not need to be time dependent so therefore I will set my time to steady. Since the inlet jet is meant to be turbluent I will set viscous solver to k-epsilon. I will set my domain as water-liquid then focus on my boundary conditions. Like you've previously mentioned, walls will be wall, inlet will be set to velocity-inlet and outlets set to outflow. I've read on other threads that I can set my water surface to wall and put the shear equal to 0 to simulate the water's surface. I will also try setting the surface to pressure-outlet. Finally, I will initialize the model computing from the inlet and run my calculations. What do you think of my method thus far?

 May 3, 2013, 09:52 #8 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,097 Rep Power: 16 Sounds good. I never use the "outflow" bc. Don't know why, but up to now pressure and velocity/massflow was the choice __________________ The skeleton ran out of shampoo in the shower.

 May 3, 2013, 09:55 #9 New Member   Michael Bell Join Date: May 2013 Posts: 5 Rep Power: 4 Brilliant. Thank you for your help! I'll let you know how I get on.

 May 3, 2013, 10:03 #10 Senior Member     Philipp Join Date: Jun 2011 Location: Germany Posts: 1,097 Rep Power: 16 I think I would try this: pool.jpg 2phase VOF-flow. Don't know if that works, but it looks the most intuitionally to me. __________________ The skeleton ran out of shampoo in the shower.

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