k-omega SST - Low Re Wall Functions

fredicenci · March 7, 2017, 13:18

Hello Guys,

Well, I’ve been reading about the use of wall functions (or not to use them) in k-omega SST.
What I would like to know is:

What is the difference between fixedValue and low reynolds wall funcions (kLowReWallFunction; omegaWallFunction; nutLowReWallFunction)

If I have a external turbulent flow, where y +< 1, and I want to avoid the use of wall functions, what should I use on the walls for k, omega and nut? fixedValue or LowReFunctions?

Also, on "Value" I always set as $internalField (the same value estimated for the inlet). What is the difference if I set "uniform 0" instead internalField ?

Thanks a lot

piu58 · March 7, 2017, 13:36

If y+ is very small you don't need any wall functions. They don't have any effect, the parameters come close to zero. You may try that out.

fredicenci · March 8, 2017, 17:24

Thanks for your reply,

So, what should be the settings for omega and k on the walls? fixedvalue value; uniform 0; ?? zerogradient??

Thanks a lot!

piu58 · March 9, 2017, 02:17

You may use the adequate wall functions with "uniform 0".

March 7, 2017, 13:18	k-omega SST - Low Re Wall Functions	#1
fredicenci Member Fredi Cenci Join Date: Dec 2016 Posts: 38 Rep Power: 9	Hello Guys, Well, I’ve been reading about the use of wall functions (or not to use them) in k-omega SST. What I would like to know is: What is the difference between fixedValue and low reynolds wall funcions (kLowReWallFunction; omegaWallFunction; nutLowReWallFunction) If I have a external turbulent flow, where y +< 1, and I want to avoid the use of wall functions, what should I use on the walls for k, omega and nut? fixedValue or LowReFunctions? Also, on "Value" I always set as $internalField (the same value estimated for the inlet). What is the difference if I set "uniform 0" instead internalField ? Thanks a lot

March 7, 2017, 13:36		#2
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	If y+ is very small you don't need any wall functions. They don't have any effect, the parameters come close to zero. You may try that out. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

March 9, 2017, 02:17		#4
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	You may use the adequate wall functions with "uniform 0". __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

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March 8, 2017, 17:24		#3
fredicenci Member Fredi Cenci Join Date: Dec 2016 Posts: 38 Rep Power: 9	Thanks for your reply, So, what should be the settings for omega and k on the walls? fixedvalue value; uniform 0; ?? zerogradient?? Thanks a lot!