vof problem
 

Dear all

I am facing a problem about VOF.

My structure is a hollow cylinder put in a wave filed. when the wave comes, water inside the hollow cylinder will rise and fall. When I look into to the scalar scene there's something wrong with the volume fraction of water within the hollow cylinder as shown in the attachment. It will be appreciated if some can help me to explain what may cause such kind of problem.

http://www.tu265.com/di-bc619e664e45...85716ba1d4.jpg

Hey Dai,

Where are you? Not on Skype anymore?

What motion are you using for the cylinder?

Arun

It just looks like a lot of air is inside the cylinder. Are you sure the sim is converging mass each timestep? What is your CFL number for the interface?

Hi me3840

Thank you for your answer. Well, when talking about CFL, the CFL for the interface is larger than 1 which is not good. So I am currently testing a case with smaller time step size. I have one question, basically, we should keep the CFL number below 0.5 to use second order temporal discretization method, however, mesh around the device is so small that if the CFL is kept below 0.5 the computation time will be sky high. Can you give some suggestion about this issue? Thanks in advance.

Eh, you may be able to skate by with 2 or higher. Just measure the mass conservation of the heavy phase and make sure you're not loosing too much of it.