# Time step continuity error

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 January 3, 2013, 14:21 Time step continuity error #1 Member   Ali Shamooni Join Date: Oct 2010 Posts: 42 Rep Power: 8 Sponsored Links Hi I have some clear questions? I wonder if someone can reply clearly too 1-is time step continuity error really important in steady solvers including energy eq.? 2-what about unsteady ones that use piso? 3-if the answer is yes what should be the order of a-sum local, b-global c-cumulative continuity errors?

 January 4, 2013, 06:19 #2 Senior Member     Mostafa Mahmoudi Join Date: Jan 2012 Posts: 319 Rep Power: 8

January 5, 2013, 11:35
#3
Member

Ali Shamooni
Join Date: Oct 2010
Posts: 42
Rep Power: 8
Quote:
I have read the source of compressibleContinuityErrs.H and have seen in such a strange manner the continuity is checked. one of my questions was "is it realy important in steady solvers?"
as u can see in "rhoPimpleFoam" tutorial case "angleduct"after 10 step it has:

sum local=0.000953371, global=0.000776714, cumulative=0.402763

 January 5, 2013, 13:00 #4 Member   Aathavan Join Date: Nov 2012 Posts: 70 Rep Power: 6 Hi There, I am also getting the same problem, here is some data. I really dont know how to solve this problem. I am using MRFSimpleFoam Time = 31 time step continuity errors : sum local = 0.00425606, global = 0.000924716, cumulative = 0.0274701 Time = 32 time step continuity errors : sum local = 0.00357216, global = 0.000535369, cumulative = 0.0280054 Time = 33 time step continuity errors : sum local = 0.00360527, global = -0.000591305, cumulative = 0.0274141 Time = 34 time step continuity errors : sum local = 0.00362457, global = -0.000742113, cumulative = 0.026672 Time = 35 time step continuity errors : sum local = 0.00331502, global = -0.000725819, cumulative = 0.0259462 Time = 36 time step continuity errors : sum local = 0.00305899, global = 0.000333275, cumulative = 0.0262795 Time = 37 time step continuity errors : sum local = 0.0030778, global = 0.000586366, cumulative = 0.0268658 I have gone through the link which you have given to alish1984 and so many other post as well. Now I came to know, its is important as well it is something to do with pressure solver. I changed relTol to 0 then there where no problem, but its taking lot of time to solve pressure (for one time step 10 to 15 min) the above data is for relTol = 0.0005 in fvSolution --> pressure adambarfi, if you are able to explain how to solve it, I will be grateful to you. Thanks in advance, Aadhavan

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