# Make a simulation of water flowing into a vase !??

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 April 5, 2005, 11:26 Make a simulation of water flowing into a vase !?? #1 Vu Trinh Tuan Guest   Posts: n/a I want to simulate water flowing into a vase, like this : http://img.photobucket.com/albums/v4...pnet/mykem.jpg But the problem is I don't know how to set up a variable to simulate the flow !!! I think there must be a variable, which is called "water" or something like that, otherwise, when using CFX-Post, we just have : pressure, temperature, velocity, …. But we don't know how water flows. Therefore, I use a variable called "water", type of which is "Volumetric" and Units is "kg m^-3" but I think it's not correct. The simulating result looks very bad. This is my result : http://img.photobucket.com/albums/v4...t/myresult.jpg So, can you tell me how to set up a variable to simulate water flowing into a vase ? I need the simalation to be as real as possible ! Like this picture : http://img.photobucket.com/albums/v4...et/mychuan.jpg

 April 5, 2005, 11:30 Re: Make a simulation of water flowing into a vase #2 HVN Guest   Posts: n/a Did you use VOF method?

 April 5, 2005, 12:36 Re: Make a simulation of water flowing into a vase #3 Vu Trinh Tuan Guest   Posts: n/a I don't know ! In Ansys Multiphysics, we can use VOF, but limit with 2D model ! We can't use VOF method with 3D model in Ansys Multiphysics ! In CFX, I don't know how to use VOF ??? thanks for reading !

 April 5, 2005, 13:48 Re: Make a simulation of water flowing into a vase #4 Rui Guest   Posts: n/a Hi, You have to chose 2 fluids (multiphase flow): Water and Air (I suppose the vessel is previously full of Air). The presence of water will be characterized by its volume fraction (Water.vf in CFX-Post) In CFX-Pre, Domain, Fluid Models, chose the Standard Free-Surface Model (take a look at the CFX-5.7.1 Documentation, Solver Theory, Multiphase Theory, page 161). You may chose the Homogeneous or the Inhomogeneous Model, I don't know which one will work better in your case, but I think you may start with the Homogeneous Model and if you cannot get good results change to the Inhomogeneous Model (take a look at Solver Modelling, Multiphase Flow Modelling, pages 154-155). Take a look at Tutorial 7 (Free Surface Flow over a Bump), and if you have access to the CFX-Community web site, take a look at this paper: http://www-waterloo.ansys.com/cfxcom...CFXTP00341.pdf . Both deal with steady-state situations, but they deal with water-air free surface flows. However, in transient simulations you are not allowed to use mesh adaption. About your model: 1- If it is axissimetric, I suppose you may model just a slice of the domain and apply symmetry boundary conditions. 2- There has to be an outlet for the air to leave the vessel. For what I saw in one of the .jpg there isn't such boundary. 3- You used the same time-steps as in Tutorial 4. Do the equations converge? I'm nearly sure they don't. For this kind o processes you will need quite smaller time-steps Regards, Rui

 April 6, 2005, 05:16 Re: Make a simulation of water flowing into a vase #6 Vu Trinh Tuan Guest   Posts: n/a To HVN : You're right ! I'm very suprised !!! You knew me from Vietnam ? Why you're trying to learn Vietnamese ? I have just read example No.7 of CFX, so, I think I knew the way to set up VOF method in CFX 5.7. Anyway, can you tell me more clearly about what you say : "Following your geometry, why do you use a full 3D model. You should perhaps use a slice of your geometry with only 1 cell layer in the thickness. It is a way to model a 2D geometry with a 3D software." PS : Anyway, where are you come from ? thanks everbody !!!

 April 6, 2005, 06:49 Re: Make a simulation of water flowing into a vase #7 HVN Guest   Posts: n/a See tutorail 7, 11 or 19 for an example of 2D simulations with a 3D CFD software. In other words, take one section of your geometry with a small thickness and put symmetry conditions on both sides of your section. But depending of your meshing software, it would be easy or not to mesh efficiently (for myself, I would use Gambit or Prostar for that). HV PS: I am a vietnamese french.

 April 6, 2005, 14:23 Re: Make a simulation of water flowing into a vase #8 Vu Trinh Tuan Guest   Posts: n/a To HVN : thanks for helping ! But I think what I need is 3D model and transient ! I understood your meaning : "2D simulations with a 3D CFD software", but I think in this case, it's not enough ! First, now, I am trying to do example No.7, in transient ! But I don't know what I did right or wrong, hic ! Anyway, can you show me the way to do Ex.No.7 in transient ??? You know, my english is bad, so, you should be sympathetic towards me, trying understand what I said !!! PS : to HVC : can you give me your e-mail ? My name is TRUNG thanks everybody !

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