I am trying to simulate a water film flow on the walls of a vertical pipe, but the surface tension is causing so much trouble as the solution is diverging. In my tansient simulation to solve the divergence problem I decreased the time step but the simulation is going to take a very long time.
Do you have any idea how can I deal with this problem?
My simulation is 2D, transient simulation and multiphase flow (air and water).
Models used energy, turbulence and VOF models.
have you check your mesh size? Because The divergen of the solution is not only depend on the time step of simulation, but also on the mesh size.
Hi Mohamed Salama
Apart from the mesh quality you could increase your general mesh size to get better stability at the same time step size for your simulation, as Ardan Nagra Coutsar allready mentioned, of cause you will trade off some degree of accuracy.
Take a look at the definition of the Courant number: https://en.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_condition.
Ardan Nagra Coutsar I have a very fine mesh it's part of the problem actually, (it is delaying the computation process) but I don't know any guidance except the value of Y+.
Christian Schubert
I will increase my mesh size, because I guess it is finer as it should be, do u have any guidelines that I can follow to determine initial mesh size?
Also, I want to ask about implicit body force option under VOF model, are you able to explain it to me?
One more question, can you explain enhanced wall treatment option to me? these options might affect the convergence in my solution but I don't fully understand it.
Mohamed Salama What type of mesh do you use? According to my experience type of mesh which give the stable simulation is tetrahedron. And also try to use finer mesh in spesific region, dont use same mesh size in your model.
Maybe you should try grid convergence/grid independence. Try to run your model with coarse mesh (triangle and bigger size) then reduce the size and also finer your mesh in spesific regin (ex: around the wall of pipe)
Implicit body force can make your simulation convergence.
Maybe you can check here https://www.sharcnet.ca/Software/Fluent6/html/ug/node929.htm#sec-imp-body-forces.
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