Small timestep make the simulation not converge

Anna Tian · August 7, 2012, 16:09

Hi

I was stuck by the convergence problem for whole the last week. Today I accidentally find out why. The reason is I used too small time step. But the FAQ suggests us to use small timestep to make our simulation converge. Could you explain why sometimes, to the contrary of the theory, small time step might even prevent convergence?

ghorrocks · August 7, 2012, 19:25

If your time step gets too small then round off errors can become large. Then the noise from round off error means convergence is difficult.

August 7, 2012, 16:09	Small timestep make the simulation not converge	#1
Anna Tian Senior Member Meimei Wang Join Date: Jul 2012 Posts: 494 Rep Power: 15	Hi I was stuck by the convergence problem for whole the last week. Today I accidentally find out why. The reason is I used too small time step. But the FAQ suggests us to use small timestep to make our simulation converge. Could you explain why sometimes, to the contrary of the theory, small time step might even prevent convergence? __________________ Best regards, Meimei

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August 7, 2012, 19:25		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	If your time step gets too small then round off errors can become large. Then the noise from round off error means convergence is difficult.