Setup for implicit LES

newbie384 · April 13, 2015, 22:10

Hi. As I understand, implicit LES means no SGS model is used. If I use WALE, I have to set the constant Cw=0 in starccm+. I wonder what should I do with the constant Ct, which is related to turbulent time scale. Should I set Ct=0 as well for implicit LES? Thanks a lot in advance.

DaveyBaby · April 14, 2015, 05:00

I think implicit generally refers to the time-marching scheme and not the subgrid scale models?
Cw=0.544 by default, an optimised parameter. Why do you have to set Cw=0 please? Is this to help the turbulence to develop initially or something? Sorry if my answer is actually a question, I am intrigued! I have initialised all my LES successfully without doing this, is it to save time?

reza_65 · November 28, 2016, 13:06

Quote:

Originally Posted by DaveyBaby

I think implicit generally refers to the time-marching scheme and not the subgrid scale models?
Cw=0.544 by default, an optimised parameter. Why do you have to set Cw=0 please? Is this to help the turbulence to develop initially or something? Sorry if my answer is actually a question, I am intrigued! I have initialised all my LES successfully without doing this, is it to save time?

Hi,

No here, implicit Les means, having no Subgrid-scale model for turbulence.
Moreover, in the MILES approach, the numerical error of the schemes are used as SGS models by purpose.
A paper on the topic using OpenFOAM: http://dx.doi.org/10.1002/
fld.925

Regards,
Reza

April 13, 2015, 22:10	Setup for implicit LES	#1
newbie384 Member Join Date: Mar 2013 Posts: 68 Rep Power: 13	Hi. As I understand, implicit LES means no SGS model is used. If I use WALE, I have to set the constant Cw=0 in starccm+. I wonder what should I do with the constant Ct, which is related to turbulent time scale. Should I set Ct=0 as well for implicit LES? Thanks a lot in advance.

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April 14, 2015, 05:00		#2
DaveyBaby Member DaveyBaby Join Date: May 2013 Posts: 46 Rep Power: 12	I think implicit generally refers to the time-marching scheme and not the subgrid scale models? Cw=0.544 by default, an optimised parameter. Why do you have to set Cw=0 please? Is this to help the turbulence to develop initially or something? Sorry if my answer is actually a question, I am intrigued! I have initialised all my LES successfully without doing this, is it to save time?