Cavitation convergence problem

Figd84 · September 29, 2009, 11:41

i´m studying cavitation in a knife valve preceded by 3 plate-horifice devices. The geometry is 2D. I´ve done a steady, turbulent (k-epsilon) simulation to stablish a initial flow field without activating the cavitation model. After have a good convergence I´ve included the cavitation model, changing the pressure-velocity coupling to Simplec and linear pressure discretization.

I´ve been testing many under relaxation factors but I have divergence with every of them. I´ve tried unsteady solution with 0.0001s time step, but obtained the same result.

Any advice on this??

Thanks in advance

-mAx- · September 30, 2009, 02:21

Is your time step really adapted?
try to set dt as follow:
dt= 0.5 * (min cell size)/(max velocity expected)
For info, I set dt=1e-7..1e-6 for hydraulic devices

Figd84 · September 30, 2009, 15:46

I´ve reduced time step, it´s iterating now... I´ll let you know the results. Thanks

September 29, 2009, 11:41	Cavitation convergence problem	#1
Figd84 Member Felipe Gutiérrez Donoso Join Date: Mar 2009 Posts: 31 Rep Power: 17	i´m studying cavitation in a knife valve preceded by 3 plate-horifice devices. The geometry is 2D. I´ve done a steady, turbulent (k-epsilon) simulation to stablish a initial flow field without activating the cavitation model. After have a good convergence I´ve included the cavitation model, changing the pressure-velocity coupling to Simplec and linear pressure discretization. I´ve been testing many under relaxation factors but I have divergence with every of them. I´ve tried unsteady solution with 0.0001s time step, but obtained the same result. Any advice on this?? Thanks in advance

September 30, 2009, 02:21		#2
-mAx- Super Moderator Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41	Is your time step really adapted? try to set dt as follow: dt= 0.5 * (min cell size)/(max velocity expected) For info, I set dt=1e-7..1e-6 for hydraulic devices __________________ In memory of my friend Hervé: CFD engineer & freerider

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September 30, 2009, 15:46		#3
Figd84 Member Felipe Gutiérrez Donoso Join Date: Mar 2009 Posts: 31 Rep Power: 17	I´ve reduced time step, it´s iterating now... I´ll let you know the results. Thanks