What LES should do for you?

som87 · January 21, 2014, 16:05

The main reason which restrict the wide range use of LES now-a-days, is the computational cost. Lets be practical, most cases (talking about industry), people are more concerned about calculation of some flow property say pressure distribution. Now using URANS, the results can very well be used for industry purpose where with LES the same (or maybe accurate if applied properly) data will cost more cpu. I have been once told "no need of 4th order accuracy" while I was trying to modify a code. LES is a far more physical model of turbulence than URANS. But when we are talking about industry...thing's will always be judged in economic way

To other poster: idk whats more stupid:- to make a joke or to troll on one

sbaffini · January 21, 2014, 16:17

I should first say that i know nothing about how things work in USA and, specifically, the CTR at Stanford.

But, from what i understood, they go where money are. Specifically, it seems that the PSAAP program is now giving money on UQ.

In contrast, the Summer Program seems more representative of what is now going on. Still, the lower income of LES works could simply reflect the fact that, after 30 years on LES, there is much less to say on the general level without really going into details, something which is not easily financed in these days.

Also, after 30 years, it might be the case that people now understand LES sufficiently to realize that they do not want to have anything to do with it.

Finally, it might be also the case that the time LES required to be mature enough (it still isn't in my opinion) has been sufficient for DNS to become available for the simulations targeted by the mature LES. For example, if you consider the channel flow test case, there are no clear proofs that a general purpose (i.e., a non spectral code) LES solver could really do it at Re numbers beyond, maybe, Re_tau=950... which is still embarassingly low for applications.

If we go to more complicate applications, where no actual DNS reference exists, my opinion is that, as a matter of fact, ILES is the approach which possibly gives the higher reliability... which is, at least, ironic and says everything on the status of LES.

FMDenaro · January 21, 2014, 16:40

more details about the state-of-the-art in LES can be found in http://meetings.aps.org/Meeting/DFD13/sessionindex2

January 21, 2014, 16:05		#41
som87 Member Join Date: May 2012 Posts: 68 Rep Power: 14	The main reason which restrict the wide range use of LES now-a-days, is the computational cost. Lets be practical, most cases (talking about industry), people are more concerned about calculation of some flow property say pressure distribution. Now using URANS, the results can very well be used for industry purpose where with LES the same (or maybe accurate if applied properly) data will cost more cpu. I have been once told "no need of 4th order accuracy" while I was trying to modify a code. LES is a far more physical model of turbulence than URANS. But when we are talking about industry...thing's will always be judged in economic way To other poster: idk whats more stupid:- to make a joke or to troll on one __________________ Best wishes, Somdeb Bandopadhyay

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January 21, 2014, 16:17		#42
sbaffini Senior Member Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 2,195 Blog Entries: 29 Rep Power: 39	I should first say that i know nothing about how things work in USA and, specifically, the CTR at Stanford. But, from what i understood, they go where money are. Specifically, it seems that the PSAAP program is now giving money on UQ. In contrast, the Summer Program seems more representative of what is now going on. Still, the lower income of LES works could simply reflect the fact that, after 30 years on LES, there is much less to say on the general level without really going into details, something which is not easily financed in these days. Also, after 30 years, it might be the case that people now understand LES sufficiently to realize that they do not want to have anything to do with it. Finally, it might be also the case that the time LES required to be mature enough (it still isn't in my opinion) has been sufficient for DNS to become available for the simulations targeted by the mature LES. For example, if you consider the channel flow test case, there are no clear proofs that a general purpose (i.e., a non spectral code) LES solver could really do it at Re numbers beyond, maybe, Re_tau=950... which is still embarassingly low for applications. If we go to more complicate applications, where no actual DNS reference exists, my opinion is that, as a matter of fact, ILES is the approach which possibly gives the higher reliability... which is, at least, ironic and says everything on the status of LES.

January 21, 2014, 16:40		#43
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,896 Rep Power: 73	more details about the state-of-the-art in LES can be found in http://meetings.aps.org/Meeting/DFD13/sessionindex2