Komega sst wall function

AhmedHafez · June 26, 2021, 07:41

Hi everyone,
I have been working with fluent and now I try to shift to OpenFoam.

I know that there are many threads that discuss this subject. However, I still bit confused with appling wall functions for komega sst model, since I don't use them in fluent.

Why do i need wall function if my yplus <1. If I will apply it which one shall chose for k, omega and nut.

Is the case change if I have a bit larger yplus.

Thank you all.

HPE · June 26, 2021, 08:59

Hi,

>> Why do i need wall function if my yplus <1.

There is no wall-function term/modelling being applied to flow regions below yPlus=1 etc. OpenFOAM applies/switches/blends the available expressions/wall models automatically depending on spatiotemporal-variant yPlus values, so that users would not need to think/worry about yPlus - wall-function interactions.

So, wall function in OpenFOAM is just all-in-one Pokémon.

AhmedHafez · June 26, 2021, 10:07

Thank you for your reply. Now, I understanded
so, could you help me choosing the best one for komega sst, I found:
K have two types of wall function: kqRWallFunction and kLowReWallFunction
Omega have only: omegaWallFunction
and for nut : nutWallFunction, nutLowReWallFunction, nutUWallFunction, nutkWallFunction and nutUSpaldingWallFunction

I appreciate your help.

HPE · June 26, 2021, 10:25

I don't think there is the best one. The safest option might be choosing nutUSpalding and kqRWallFunction for the multiple-choice items above.

AhmedHafez · June 26, 2021, 11:17

Thank you for your great help

June 26, 2021, 07:41	Komega sst wall function	#1
AhmedHafez New Member Ahmed Hafez Join Date: Jul 2018 Posts: 26 Rep Power: 7	Hi everyone, I have been working with fluent and now I try to shift to OpenFoam. I know that there are many threads that discuss this subject. However, I still bit confused with appling wall functions for komega sst model, since I don't use them in fluent. Why do i need wall function if my yplus <1. If I will apply it which one shall chose for k, omega and nut. Is the case change if I have a bit larger yplus. Thank you all.

June 26, 2021, 08:59		#2
HPE Senior Member Herpes Free Engineer Join Date: Sep 2019 Location: The Home Under The Ground with the Lost Boys Posts: 932 Rep Power: 12	Hi, >> Why do i need wall function if my yplus <1. There is no wall-function term/modelling being applied to flow regions below yPlus=1 etc. OpenFOAM applies/switches/blends the available expressions/wall models automatically depending on spatiotemporal-variant yPlus values, so that users would not need to think/worry about yPlus - wall-function interactions. So, wall function in OpenFOAM is just all-in-one Pokémon. saidc. likes this. __________________ The OpenFOAM community is the biggest contributor to OpenFOAM: User guide/Wiki-1/Wiki-2/Code guide/Code Wiki/Journal Nilsson/Guerrero/Holzinger/Holzmann/Nagy/Santos/Nozaki/Jasak/Primer Governance Bugs/Features: OpenFOAM (ESI-OpenCFD-Trademark) Bugs/Features: FOAM-Extend (Wikki-FSB) Bugs: OpenFOAM.org How to create a MWE New: Forkable OpenFOAM mirror

June 26, 2021, 10:25		#4
HPE Senior Member Herpes Free Engineer Join Date: Sep 2019 Location: The Home Under The Ground with the Lost Boys Posts: 932 Rep Power: 12	I don't think there is the best one. The safest option might be choosing nutUSpalding and kqRWallFunction for the multiple-choice items above. __________________ The OpenFOAM community is the biggest contributor to OpenFOAM: User guide/Wiki-1/Wiki-2/Code guide/Code Wiki/Journal Nilsson/Guerrero/Holzinger/Holzmann/Nagy/Santos/Nozaki/Jasak/Primer Governance Bugs/Features: OpenFOAM (ESI-OpenCFD-Trademark) Bugs/Features: FOAM-Extend (Wikki-FSB) Bugs: OpenFOAM.org How to create a MWE New: Forkable OpenFOAM mirror

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June 26, 2021, 10:07		#3
AhmedHafez New Member Ahmed Hafez Join Date: Jul 2018 Posts: 26 Rep Power: 7	Thank you for your reply. Now, I understanded so, could you help me choosing the best one for komega sst, I found: K have two types of wall function: kqRWallFunction and kLowReWallFunction Omega have only: omegaWallFunction and for nut : nutWallFunction, nutLowReWallFunction, nutUWallFunction, nutkWallFunction and nutUSpaldingWallFunction I appreciate your help.

June 26, 2021, 11:17		#5
AhmedHafez New Member Ahmed Hafez Join Date: Jul 2018 Posts: 26 Rep Power: 7	Thank you for your great help