cavitating calculations on a pressure control valve

SimonH. · October 12, 2009, 08:03

hi guys

right know i´m writing my diploma thesis and for that i make a benchmark between cfx and openfoam. my current subject is a pressure control valve with different lifts and pressure difference. i specified most of it in a nother thread: http://www.cfd-online.com/Forums/ope...rol-valve.html and http://www.cfd-online.com/Forums/ope...lon-model.html . After laminar calculations in both codes i had large differences in my results so i made turbulent simulations for cases with high re-numbers. In the postprocessing appeard negative pressures so i decided to start a twophase calculation. So my problem is the even after more than 1000 iterations in steadystate the force on my moving body dont converge and i have a high imbalance between my massflow on the in- and outlet. what kind of specification would be appropriate in this case or in a transient case. I´m fairly new in cfd and after all my other cases in cfx ran without big problems i dont have too much insight in cfx could there be something i just forgotten. Maybe someone have some clues for me or faced something similar.

hope to hear from you

mfg simon

ghorrocks · October 12, 2009, 18:20

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

Cavitation modelling is not an easy topic. Are you sure you need it? It makes things more complicated by orders of magnitude. As it appears you are a beginner then I strongly suggest you get the single phase simulations working reliably before even considering multiphase stuff.

I have done plenty of simulations of valves with mild cavitation were a single phase simulation was close enough to get the device performance. If the cavitation region is small then it can be ignored.

October 12, 2009, 08:03	cavitating calculations on a pressure control valve	#1
SimonH. New Member Simon Hastreiter Join Date: Jun 2009 Location: Regensburg Posts: 17 Rep Power: 16	hi guys right know i´m writing my diploma thesis and for that i make a benchmark between cfx and openfoam. my current subject is a pressure control valve with different lifts and pressure difference. i specified most of it in a nother thread: http://www.cfd-online.com/Forums/ope...rol-valve.html and http://www.cfd-online.com/Forums/ope...lon-model.html . After laminar calculations in both codes i had large differences in my results so i made turbulent simulations for cases with high re-numbers. In the postprocessing appeard negative pressures so i decided to start a twophase calculation. So my problem is the even after more than 1000 iterations in steadystate the force on my moving body dont converge and i have a high imbalance between my massflow on the in- and outlet. what kind of specification would be appropriate in this case or in a transient case. I´m fairly new in cfd and after all my other cases in cfx ran without big problems i dont have too much insight in cfx could there be something i just forgotten. Maybe someone have some clues for me or faced something similar. hope to hear from you mfg simon

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October 12, 2009, 18:20		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	http://www.cfd-online.com/Wiki/Ansys...gence_criteria Cavitation modelling is not an easy topic. Are you sure you need it? It makes things more complicated by orders of magnitude. As it appears you are a beginner then I strongly suggest you get the single phase simulations working reliably before even considering multiphase stuff. I have done plenty of simulations of valves with mild cavitation were a single phase simulation was close enough to get the device performance. If the cavitation region is small then it can be ignored.