Number of internal iterations in the Dual time method

diwakaranant · December 23, 2013, 09:52

Hi All

I am trying to run an unsteady simulation using Dual
time stepping, over NACA0012 airfoil.
I am using Euler Implicit time integration scheme.

I wanted to know how to select the value of internal iterations
UNST_INT_ITER, for the dual time method ?

I ran the steady case which took around 40000 iterations for the
given convergence criteria.

Is the value of internal iterations for the dual time method related to this ?

Thanks
Anant

fpalacios · January 11, 2014, 23:16

Instead os specifying the number of iteration you can specify the convergence level (3-4 order of magnitude would be OK)
RESIDUAL_REDUCTION= 3
In principle the inner iteration should converge quicker than the steady state case because the physical step is typically very small and your initial guess is close to the final solution after Deta t.

Best Regards,
Francisco

December 23, 2013, 09:52	Number of internal iterations in the Dual time method	#1
diwakaranant Member Anant Diwakar Join Date: Jan 2013 Posts: 68 Rep Power: 13	Hi All I am trying to run an unsteady simulation using Dual time stepping, over NACA0012 airfoil. I am using Euler Implicit time integration scheme. I wanted to know how to select the value of internal iterations UNST_INT_ITER, for the dual time method ? I ran the steady case which took around 40000 iterations for the given convergence criteria. Is the value of internal iterations for the dual time method related to this ? Thanks Anant

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January 11, 2014, 23:16		#2
fpalacios Super Moderator Francisco Palacios Join Date: Jan 2013 Location: Long Beach, CA Posts: 404 Rep Power: 15	Instead os specifying the number of iteration you can specify the convergence level (3-4 order of magnitude would be OK) RESIDUAL_REDUCTION= 3 In principle the inner iteration should converge quicker than the steady state case because the physical step is typically very small and your initial guess is close to the final solution after Deta t. Best Regards, Francisco