Hi,

Is it possible to perform remeshing in CFX, i.e. change mesh topology (reduce or increase number of nodes and elements) in order to maintain mesh quality during calculation?

Thank you.

Only if you use the mesh adaptation feature (steady state only?). General mesh topology changes arnt allowed.

Hi,

You can stop the simulation and restart with a new mesh and interpolate the results onto the new mesh. This allows changes of mesh topology in both steady and transient simulations.

Glenn Horrocks

If you are doing a transient run with moving meshes and you use this interpolation method, you can set the first few timesteps after the interpolation to be very small compared to the normal timestep size. This will help reestablish decent convergence levels.

You can automate this too using junction box routines i.e. use logic like:

After interpolation use 0.001*DT until convergence levels are below X threshold value whereafter use DT.

How can I simulate piston moving in CFX10. Major problem is that entire volume must be collapsed during piston moving. Is there some ideas how to avoid highly skewed elements?

Hi Stanislav,

Have a look at my PhD thesis. I used CFX4 to model an IC engine but the same methodology works for CFX5/CFX10 and is much easier to implement.

http://adt.lib.uts.edu.au/public/adt...018/index.html

Note that normal IC engines still have some clearance volume at TDC so the volume does not collapse to zero. You can use this to squish the mesh into the small space left and not do any mesh topology changes, at least for the piston motion.

Glen Horrocks

Glenn!

Thank you very much. Your thesis is very helpfull. I have only one question about it. Can I use this technique to simulate Fluid Structure Interaction (FSI) problem? I'm going to use CFX+Ansys. Do you know if it possible to control CFX by Fortran routines during FSI simulation?

Hi,

I do not know the limitations of FSI. Talk to CFX support.

Glenn Horrocks