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Old   July 19, 2002, 05:05
Default CFL number and time accuracy for LES
Li Yang
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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.


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Old   July 28, 2002, 02:47
Default Re: CFL number and time accuracy for LES
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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
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Old   August 1, 2002, 06:11
Default Re: CFL number and time accuracy for LES
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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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