How to set initial conditions for LES 3D case?

Derek2580 · March 20, 2018, 21:29

Still doing unsteady flow past 3D cylinder. Can someone advise how to set initial conditions for LES 3D case?? Or if you could provide any similar tutorial. Much appreciate!

Initial conditions includes: k, nut, nuTilda, p and u (btw, is "s" necessary for LES?

piu58 · March 21, 2018, 01:12

I use:

k: Fixed value 0.1 nearly everywhere, kqRWallFunction at a surface of interest

nut: calculated nearly eveyrwhere, nutkWallFunction at a surface of interest

p: zeroGradient nearly everywhere, a fixed value at one of the patches

I don't need much more for the dynamicKEqn model.

Derek2580 · March 21, 2018, 23:07

Thank you Sir!

Derek2580 · March 30, 2018, 11:38

sir, will the initial k and nut significant affect the calculation results?

piu58 · March 30, 2018, 12:25

In any case it influences how fast and stable the simulation starts. But you may try this out for your case.

dickcruz · April 22, 2018, 02:41

Quote:

Originally Posted by piu58

I use:

k: Fixed value 0.1 nearly everywhere, kqRWallFunction at a surface of interest

nut: calculated nearly eveyrwhere, nutkWallFunction at a surface of interest

p: zeroGradient nearly everywhere, a fixed value at one of the patches

I don't need much more for the dynamicKEqn model.

I always thought that the kqRWallFunction and nutKWallFunction were used only on cases with RAS for turbulence modelling. Is that not true?

So, with these wall functions in place, do you use 30<y+<300 ?

March 20, 2018, 21:29	How to set initial conditions for LES 3D case?	#1
Derek2580 New Member Derek Join Date: Mar 2018 Posts: 10 Rep Power: 8	Still doing unsteady flow past 3D cylinder. Can someone advise how to set initial conditions for LES 3D case?? Or if you could provide any similar tutorial. Much appreciate! Initial conditions includes: k, nut, nuTilda, p and u (btw, is "s" necessary for LES?

March 21, 2018, 01:12		#2
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	I use: k: Fixed value 0.1 nearly everywhere, kqRWallFunction at a surface of interest nut: calculated nearly eveyrwhere, nutkWallFunction at a surface of interest p: zeroGradient nearly everywhere, a fixed value at one of the patches I don't need much more for the dynamicKEqn model. __________________ Uwe Pilz -- Die der Hauptbewegung überlagerte Schwankungsbewegung ist in ihren Einzelheiten so hoffnungslos kompliziert, daß ihre theoretische Berechnung aussichtslos erscheint. (Hermann Schlichting, 1950)

March 30, 2018, 12:25		#5
piu58 Senior Member Uwe Pilz Join Date: Feb 2017 Location: Leipzig, Germany Posts: 744 Rep Power: 15	In any case it influences how fast and stable the simulation starts. But you may try this out for your case. __________________ 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 21, 2018, 23:07		#3
Derek2580 New Member Derek Join Date: Mar 2018 Posts: 10 Rep Power: 8	Thank you Sir!

March 30, 2018, 11:38		#4
Derek2580 New Member Derek Join Date: Mar 2018 Posts: 10 Rep Power: 8	sir, will the initial k and nut significant affect the calculation results?