Multiphase simulation
Hi,
Iīm learning using Ansys CFX 12.0 and a have a problem with multiphase simulation. My geometry is a kind of cup with an initial level of water and Iīd like simulate the flow inside it when the wall rotates at 2 rad/s, considering a steady state analysis. On CFX-Pre, I started defining in my default domain two fluids, air and water, but I didnīt know how to set this initial level of water and separate it from the air, like a two phase system. Iīve already considered no slip wall, laminal flow, buoyancy and surface tension but my results for volume fraction on CFD-Post are not what I expect, like a paraboloid shape. I couldnīt find the same situation on tutorials. Can someone help me? Thanks, Willian |
Hi, maybe I can help you but I think that the simulation is too complicated for one person that now is learning code.
So, could you send me an image of your domain? Is it your first multiphase simulation? Regards |
hi mach000,
were you able to fix that? I'm having similar problems..... |
Hi,
Yes, itīs my first multiphase simulation and I canīt find anywhere an example for a similar simulation in Ansys CFX. As a first aproximation, I created a simple cilynder using ICEM tools and allowed an auto sizing meshing. My parameters are basically a rotating wall, 2 rad/s, and top surface open to atmosphere and my initial condition is that 50% of cilynder volume is full of water. I think my problem is setting this initial level of water and make sure that there is a two phase situation (Air, Water). Is there any difference in results between defining a new material as a mixture and selecting two materials in domain settings? Thanks a lot for your help, Willian Ps.: ICEM Mesh: http://img641.imageshack.us/i/cilindro.png/ |
It is very hard to run free surface simulations steady state. You will probably have to run the simulation as a transient and wait for the surface to settle out.
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Then, why don't you try to create an hexa elements mesh? Finally, in order to simulate a multiphase simulation you need to define some expression such as Stevin Law and the initial quote of the freesurface. You will find theese expressions in some tutorials. Let me know |
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Thanks for your help, Willian |
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Don't use the surface tension model unless you need it. It makes convergence even harder and mesh quality requirements even stricter. And as I previously said, you have little hope in getting this to work steady state. You will have to run transient and march it out until the waves die down. |
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