newtons method failing to converge... help?

mealyj · January 27, 2010, 13:11

Hi,

I want to simulate the flow of oxygen dissolved in water through a porous medium with the aim of determining the change in concebtration of O2 over time. at the moment i am using a homogenous binary mixture of O2 and H20. however the solver wont complete and gives an error saying that newton's method failed to converge in 150 iterations in relation to the variable static pressure. this occurs in all domains. any ideas on why this might be happening? any help would be greatly appreciated.

Cheers.

mealyj · January 27, 2010, 14:15

correction: that should be variable composition mixture.

same problem though

ghorrocks · January 27, 2010, 17:04

It is not going to be possible to debug a multi-phase simulation like this on the forum. All I can recommend is you follow the general principle of starting with a simple single phase flow and making sure everything converges. The add the physics one step at a time, making sure it converges each time.

You may need a very small time step, double precision, a better initial guess or to ramp the flow from a simple initial condition to the true situation.

January 27, 2010, 13:11	newtons method failing to converge... help?	#1
mealyj New Member Jake Mealy Join Date: Jan 2010 Posts: 6 Rep Power: 16	Hi, I want to simulate the flow of oxygen dissolved in water through a porous medium with the aim of determining the change in concebtration of O2 over time. at the moment i am using a homogenous binary mixture of O2 and H20. however the solver wont complete and gives an error saying that newton's method failed to converge in 150 iterations in relation to the variable static pressure. this occurs in all domains. any ideas on why this might be happening? any help would be greatly appreciated. Cheers.

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January 27, 2010, 14:15		#2
mealyj New Member Jake Mealy Join Date: Jan 2010 Posts: 6 Rep Power: 16	correction: that should be variable composition mixture. same problem though

January 27, 2010, 17:04		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	It is not going to be possible to debug a multi-phase simulation like this on the forum. All I can recommend is you follow the general principle of starting with a simple single phase flow and making sure everything converges. The add the physics one step at a time, making sure it converges each time. You may need a very small time step, double precision, a better initial guess or to ramp the flow from a simple initial condition to the true situation.