# CFL number and time accuracy for LES

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 July 19, 2002, 05:05 CFL number and time accuracy for LES #1 Li Yang Guest   Posts: n/a Dear all, I am now doing LES using SIMPLE based solver. I use the Crank-Nicolson scheme in time and the central difference scheme in space. I would like to use the fully implicit scheme in time as well. My questions are: (1) Which scheme would allow me to use a larger CFL number and how large a CFL number you normally used? (2) How do I know my solution is time accurate ? Thank you very much in advance. Li

 July 28, 2002, 02:47 Re: CFL number and time accuracy for LES #2 baal Guest   Posts: n/a hello,i finished the code of les program with fortran,and i use implicit scheme,but when cfl is 1.22,the convergent rate is very small,could you help me?thanks

 August 1, 2002, 06:11 Re: CFL number and time accuracy for LES #3 adarsh Guest   Posts: n/a for implicit schemes any CFL can lead you to convergence .Cfl nos up to 20 has been used.but the accuracy of solution goes down as CFL no. increases.For time accuracy u can also use jameson's method of false time stepping. but if the samllest time scale of the flow as given by kolmogorov scales is less , the it becomes a restricting factor and convergence can be affected. hope this helps Adarsh

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