interDyMFoam gamma fluxes with topology change

sean_mcintyre · July 24, 2009, 12:20

Hi,
I'm trying to use interDyMFoam for the simulation of water entry. The geometry is similar to the movingConeTopo tutorial, with different shapes and some more grid refinement, plus a gamma field. Anyway, the solution seems to chug along nicely until the interface interacts with the cell addition zone (or removal? - I haven't checked that, as the removal zone was under the water). It seems that the gamma fluxes might get swapped (phase 1 for phase 2, or vice versa) in those cells. With a density ratio of 1, this doesn't cause stability issues, but when some quantity of water gets made into air (I think), that it generates pd spikes, eventually leading to a crash.

Has anyone else experienced this? If so, is there an easy enough fix?

Thanks,
Sean McIntyre

nikos_fb16 · July 24, 2009, 12:32

Hi,

which timediscretisation do you use? If its not euler try again with euler.

I had some problems with the rayleigh taylor instability and interdymfoam, that were related to the timescheme.

Nikos

sean_mcintyre · July 24, 2009, 13:09

I'm just trying to get a really simple case set up, so the schemes are plain Euler for time, first and second order things for space discretization. Also, if I have it write the solution really often, I can see the strange happenings in pd at the mesh extrusion layer, as opposed to the fluid-fluid interface. Actually, it does the water entry nicely until there is a change in gamma around the extrusion layer. Once that happens, pd gets funky in that region, and the solution crashes pretty quickly. I'll see about posting the case (it's small) in a little bit.

Thanks,
Sean McIntyre

July 24, 2009, 12:20	interDyMFoam gamma fluxes with topology change	#1
sean_mcintyre New Member Sean McIntyre Join Date: Mar 2009 Location: State College, PA Posts: 11 Rep Power: 17	Hi, I'm trying to use interDyMFoam for the simulation of water entry. The geometry is similar to the movingConeTopo tutorial, with different shapes and some more grid refinement, plus a gamma field. Anyway, the solution seems to chug along nicely until the interface interacts with the cell addition zone (or removal? - I haven't checked that, as the removal zone was under the water). It seems that the gamma fluxes might get swapped (phase 1 for phase 2, or vice versa) in those cells. With a density ratio of 1, this doesn't cause stability issues, but when some quantity of water gets made into air (I think), that it generates pd spikes, eventually leading to a crash. Has anyone else experienced this? If so, is there an easy enough fix? Thanks, Sean McIntyre

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July 24, 2009, 12:32		#2
nikos_fb16 New Member Nikolaos Spyrou Join Date: Mar 2009 Posts: 22 Rep Power: 17	Hi, which timediscretisation do you use? If its not euler try again with euler. I had some problems with the rayleigh taylor instability and interdymfoam, that were related to the timescheme. Nikos

July 24, 2009, 13:09		#3
sean_mcintyre New Member Sean McIntyre Join Date: Mar 2009 Location: State College, PA Posts: 11 Rep Power: 17	I'm just trying to get a really simple case set up, so the schemes are plain Euler for time, first and second order things for space discretization. Also, if I have it write the solution really often, I can see the strange happenings in pd at the mesh extrusion layer, as opposed to the fluid-fluid interface. Actually, it does the water entry nicely until there is a change in gamma around the extrusion layer. Once that happens, pd gets funky in that region, and the solution crashes pretty quickly. I'll see about posting the case (it's small) in a little bit. Thanks, Sean McIntyre