deltaT (timestep) effects on simpleFoam

ukaya · July 19, 2023, 08:26

It has been discussed without apparent solution in multiple posts in this forum, that's why I wanted to ask again.

Fact: deltaT parameter from controlDict affects the simpleFoam solver, even though it is a steadystate problem.

People hinted that it will influence the underrelaxation or turbulence equations. Does anyone have proper information/insights on this? From many trainings I heard that it will not have any effects, which is obviously wrong.

Thank you in advance,
Umut

JulioPieri · July 21, 2023, 14:57

I've noticed that there are some relaxations that use deltaT. For instance, the externalWallHeatFluxTemperature boundary condition has the option to set "thermalInertia" somewhere. Looking at the code, this term uses deltaT, despite being steady or unsteady solver.

So I agree with you, it might be in some other places with this sneaky relaxation.

sharonyue · July 25, 2023, 11:03

Is it possible to provide a case that can reproduce this issue?

D

July 19, 2023, 08:26	deltaT (timestep) effects on simpleFoam	#1
ukaya New Member Umut Kaya Join Date: Aug 2020 Posts: 5 Rep Power: 5	It has been discussed without apparent solution in multiple posts in this forum, that's why I wanted to ask again. Fact: deltaT parameter from controlDict affects the simpleFoam solver, even though it is a steadystate problem. People hinted that it will influence the underrelaxation or turbulence equations. Does anyone have proper information/insights on this? From many trainings I heard that it will not have any effects, which is obviously wrong. Thank you in advance, Umut

July 25, 2023, 11:03		#3
sharonyue Senior Member Dongyue Li Join Date: Jun 2012 Location: Beijing, China Posts: 839 Rep Power: 17	Is it possible to provide a case that can reproduce this issue? D __________________ My OpenFOAM algorithm website: http://dyfluid.com By far the largest Chinese CFD-based forum: http://www.cfd-china.com/category/6/openfoam We provide lots of clusters to Chinese customers, and we are considering to do business overseas: http://dyfluid.com/DMCmodel.html

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July 21, 2023, 14:57		#2
JulioPieri Member Julio Pieri Join Date: Sep 2017 Posts: 96 Rep Power: 8	I've noticed that there are some relaxations that use deltaT. For instance, the externalWallHeatFluxTemperature boundary condition has the option to set "thermalInertia" somewhere. Looking at the code, this term uses deltaT, despite being steady or unsteady solver. So I agree with you, it might be in some other places with this sneaky relaxation.