# Time Step in LES

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 August 21, 2010, 07:40 Time Step in LES #1 New Member   Saeed Salehi Join Date: Aug 2010 Posts: 17 Rep Power: 8 Hi Every one. i want to solve a turbulent model in fluent with LES. as you know LES is a transient model. my problem is that i dont know how much my time step should be. is there any body help me? tnx.

 August 23, 2010, 04:51 #2 New Member   Dong Liang Join Date: Jan 2010 Location: Shanghai, China Posts: 12 Rep Power: 8 hi, generally speaking, the time step in les is the reciprocal of Re number. i.e. if the Re number is 2000, the time step should be no more than 0.0005.

 August 23, 2010, 05:47 Time step is LES for Re=10^5 #3 New Member   Saeed Salehi Join Date: Aug 2010 Posts: 17 Rep Power: 8 Thank you. dear davedong. wow what a small time step! my problem Re is 10^5. do you know how much my time step should be? or generelly is there any releation between Re and best time step? Best Regards.

August 23, 2010, 22:45
#4
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Dong Liang
Join Date: Jan 2010
Location: Shanghai, China
Posts: 12
Rep Power: 8
Quote:
 Originally Posted by salehi144 Thank you. dear davedong. wow what a small time step! my problem Re is 10^5. do you know how much my time step should be? or generelly is there any releation between Re and best time step? Best Regards.
hi,
as i know, it's a rule in Smagorisky model. the reciprocal of Re is equal to the small spacial scale divided by the velocity, in another word, the time step size.
10e-5 time step size is OK. it is absolutely right.
my native language is not english. may it will not make you misunderstand.

Last edited by davedong; August 24, 2010 at 02:16.

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